Patent Application
20240404833
The present invention relates to methods for dry etching of an etching film such as silicon-containing films, metal-containing films and organic films, in particular, to dry etching methods, selective dry etching methods and cyclic selective dry etching methods for dry etching of the etching films employing an etching gas mixture including a Si-containing hydrofluorocarbon compound that has a general formula:
CxHyFzSin (I)
where 1≤x≤6, 1≤y≤9, 1≤z≤15, n=1 or 2. In some embodiments, the Si-containing hydrofluorocarbon contains at least one methyl group or comprises at least one methyl group attached to the Si atom.
Recently the control of the profile (control of shape, reduced defects and damage to the structure, etc.) and etching speed during formation of high aspect ratio structures (holes, pillars, etc.) became a significant challenge for the fabrication of new semiconductor devices (3D NAND and DRAM memories, low-k dielectric in BEOL). These devices, which are based on thick stacks of silicon oxide and/or alternated layers of silicon nitride and oxide, need to be etched with a fast etch rate and keeping a defined profile (no etch stop, bowing, twisting, or other pattern distortions).
Selective etching of various Si-containing compounds with high selectivity to each other in the same process is required for advanced patterning. Most preferable is so-called “infinite selectivity” regime where non-etching material is not etched or some polymer is deposited on top of it when an etching target material is effectively removed during etching process. Main drawback of this process is deposition of polymer on non-etching material and development of polymer thickness with increase of process time. In the case of advanced patterning presence of thick polymer film after the process will require additional cleaning step, which can cause unintentional modification of films on substrate or damage those films, further limit applicability of certain etching processes with infinite selectivity. This invention provides a new cyclic etching process utilizing Si-containing chemistry to achieve infinite selectivity of etching while not growing thick film of polymer on top of non-etching material or chamber walls. In the present disclosure we demonstrated that addition of Si-containing hydrofluorocarbon to the process gas mixture at least one step of the cyclic etching allows to increase selectivity by growth of polymer on non-etching material, when use of etching process with low selectivity during another step of cyclic etching allows to effectively control thickness of deposited polymer. In particular, it is demonstrated that it is possible to etch Si3N4 (or SiO2) with high selectivity to other tested materials when either thin film of polymer or thin interface layer is formed on surface of non-etching material after the cyclic etching.
Plasma etching method using an etching gas is a key process used for production of semiconductor devices on a substrate. Etching allows to remove material from surface of a substrate, moreover in particular cases it is possible to remove one material selectively to other using dry etching process, which allows to form fine pattern on surface of a substrate. Patterning of various thin films on a workpiece or substrate allows to form components of semiconductor device (e.g. transistors and capacitors, interconnects, signal lines and insulation). Examples of thin films commonly used in fabrication of semiconductor devices are silicon-containing compounds (e.g. polycrystalline silicon, silicon oxide or nitride), organic films (having carbon as a main component), metals, metal oxides or nitrides. For state of art semiconductor devices with most advanced technical nodes, patterning in nanometer or tens of nanometers scale order is required.
Due to the extremely small size of pattern and complex structure at the front end of semiconductor device, extremely high selectivity of the etching process to materials not targeted by the etching is required. Example of such process is so-called “multicolor etching” or “low contrast etching”, where a substrate containing multi-line layer consisting of several materials is exposed during the etching process and only one or several materials of multi-line layer are targeted to be etched. Multicolor etching and similar selective etching processes are crucial for formation of active components in front end of line, interconnects, self-aligned patterning (e.g. self-aligned multiple patterning for lithography and self-aligned contact hole etch) and other fine structures on substrate; therefore, poor selectivity and etching defects related to poor selectivity may result in degraded performance or even compromised functionality of produced semiconductor device.
Various etching processes (e.g. plasma etching, atomic layer etching, thermal etching, and wet etching) and chemistries (e.g. fluorocarbons, Cl- or Br-containing etchants) have been developed to address issue of selective etching in multicolor etching process.
Koyagura et al. (Chemical Etching Treatment of Polydimethylsiloxane for Smoothing Microchannel Surface, Journal of Photopolymer Science and Technology Volume 33, Number 5(2020) 485 490) disclose wet etching process where Si-containing fluorocarbon (C4H9F3Si) appeared in the etching mixture as byproduct. US 2021/0054286 to Lim et al discloses a wet etching method where Si-containing hydrofluorocarbon is used as part of the solvent. US 2005/0263901 to America discloses a method of modifying layer of material during deposition process using addition of Si-containing hydrofluorocarbon to the process gas mixture. U.S. Pat. No. 6,107,166 to Butterbaugh et al. discloses an etching method of alkali and alkaline earth metals based on the use of HF as a main etchant when Si-containing hydrofluorocarbon may be used as addition to the main etchant. US 2021/0193477 to Ishikawa et al. discloses used Si-containing compound as a process gas for deposition of passivation layer during cyclic etching process. WO 2009/019219 to Uenveren et al. discloses etching method of SiO2 for self-aligned contact using hydrofluorocarbons. Although several Si-containing hydrofluorocarbons (i.e., CH2F6Si2, C3H4F6Si, C3H7F3Si, C3H4F6Si) are listed, these Si-containing hydrofluorocarbons have no methyl group attached to the silicon atom and no any supporting etching examples are disclosed. US 2003/0232504 to Eppler et al, discloses a process of etching openings in a dielectric layer, in which an etchant gas includes a fluorocarbon gas (CxFyHz, where x>=1, y>=1, and z>=0), and a silane-containing gas, hydrogen or a hydrocarbon gas (CxHy, where x>=1 and y>=4).
Patterning of the substrate containing several thin films consisting of various materials is a key process for production of semiconductor devices. During patterning of substrate some etching target material could be completely or partially removed from a substrate resulting in the formation of fine pattern which allows to form components of semiconductor device (e.g. transistors and capacitors, interconnects, signal lines and insulation) after several iterations of formation of thin films and patterning. Commonly, various etching processes are used for removal of etching target material or part of etching target material during patterning of a substrate. If partial removal of target material (part of material is targeted for the etching and another part of material presented on the substrate should remain after the etching process) is desired, typically protective film (e.g. hard mask) on top of non-etching film is used. Considering extremely small feature size of patterns in modern semiconductor devices, it may be noted that hard mask should have same order of critical dimensions (e.g. diameter of hole opening, width of trench) of the pattern comparing to pattern formed on the etching target layer. It leads to the necessity to form pattern in a hard mask material with the same feature sizes as in resulting pattern on an etching target material, while keeping high selectivity of the etching process to other materials during patterning of mask to avoid damage and unwanted modifications of etching target film and non-etching films. On the other hand, there are patterning processes requiring long time, such as high aspect ratio etching of 3D NAND channels and DRAM capacitors. Long duration of the process requires use of thicker hard mask and resistant mask material. Use of thick mask results in increase of aspect ratio of pattern on mask and brings additional challenges during patterning process. Typically, thick amorphous carbon, amorphous silicon, or doped amorphous carbon or amorphous silicon are used for high aspect ratio etching processes as a hard mask. Therefore, it is necessary to have etching process capable to remove mask material with reasonable etch rate and high selectivity to other materials presented on the substrate to avoid damage of films other than hard mask for formation of semiconductor devices.
Further development of semiconductor devices requires more complex processes for formation and patterning of thin films in order to keep scaling down components, such as transistors, signal and power lines. Scaling down of feature sizes of components of semiconductor device is necessary to improve performances, efficiency and size of the final device and dramatic decrease of feature size over the past few decades brought extremely strict requirements to fabrication processes. In addition to reduction of feature sizes, portfolio of used materials increased significantly bringing new fabrication challenges. Even though there are few well established processes for selective etching of, for example, SiO2 selectively to Si3N4, using common gas mixtures (such as fluorocarbon or hydrofluorocarbon gases, Cl or Br-containing compounds), there is still a big window for improvement due to the increasing complexity of new semiconductor devices and need in increased number of materials in multicolor etching processes together with possibility to etch each of these materials highly-selective to others.
Disclosed is an etching method for forming an aperture in a substrate, the method comprising:
Also disclosed is an etching method for forming an aperture in a substrate, the method comprising:
Also disclosed is an etching method for forming an aperture in a substrate, the method comprising:
Also disclosed is an etching method for forming an aperture in a substrate, the method comprising:
Also disclosed is an etching method for forming an aperture in a substrate, the method comprising:
Also disclosed is an etching gas composition suitable for use in semiconductor etching reactions, the etching gas composition comprising:
Also disclosed is a selective etching method for forming a structure in a substrate, the selective method comprising:
Also disclosed is a selective etching method for forming a structure in a substrate, the selective method comprising
Also disclosed is a selective etching method for forming a structure in a substrate, the selective method comprising mounting the substrate on a mounting table in a reactor, the substrate having a pattern containing an etching film and at least one non-etching films deposited thereon;
Also disclosed is a selective etching method for forming a structure in a substrate, the selective method comprising
Also disclosed is a selective etching method for forming a structure in a substrate, the selective method comprising
Also disclosed is a selective etching method for forming a structure in a substrate, the selective etching method comprising:
Also disclosed is a selective etching method for forming a structure in a substrate, the selective etching method comprising:
Also disclosed is a selective etching method for forming a structure in a substrate, the selective etching method comprising:
Also disclosed is a selective etching method for forming a structure in a substrate, the selective etching method comprising:
Also disclosed is a selective etching method for forming a structure in a substrate, the selective etching method comprising:
Also disclosed is a cyclic selective etching method for removing a film, the method comprising: )
Also disclosed is a cyclic selective etching method for removing a film, the method comprising: )
Also disclosed is a cyclic selective etching method for removing a film, the method comprising:
Also disclosed is a cyclic selective etching method for removing a film, the method comprising:
Also disclosed is a cyclic selective etching method for removing a film, the method comprising:
Also disclosed is apparatus for delivering an etching gas composition to a semiconductor etching process, the apparatus comprising:
The following detailed description and claims utilize a number of abbreviations, symbols, and terms, which are generally well known in the art.
As used herein, the indefinite article “a” or “an” means one or more.
As used herein, “about” or “around” or “approximately” in the text or in a claim means ±10% of the value stated.
As used herein, “room temperature” in the text or in a claim means from approximately 20° C. to approximately 25° C.
The term “wafer” or “patterned wafer” refers to a wafer having a stack of any existing films including silicon-containing films on a substrate and a patterned hardmask layer on the stack of any existing films including silicon-containing films formed for pattern etch.
The term “substrate” refers to a material or materials on which a process is conducted. The substrate may refer to a wafer or a patterned wafer having a material or materials on which an etching process is conducted. The substrates may be any suitable wafer used in semiconductor, photovoltaic, flat panel, or LCD-TFT device manufacturing. The substrate may also have one or more layers of differing materials already deposited upon it from a previous manufacturing step. For example, the wafers may include silicon layers (e.g., crystalline, amorphous, porous, etc.), silicon-containing layers (e.g., SiO2, SiN, SiON, SiCOH, etc.), metal containing layers (e.g., copper, cobalt, ruthenium, tungsten, indium, platinum, palladium, nickel, ruthenium, gold, etc.) or combinations thereof. Furthermore, the substrate may be planar or patterned. The substrate may be an organic patterned photoresist film. The substrate may include layers of oxides which are used as dielectric materials in MEMS, 3D NAND, MIM, DRAM, or FeRam device applications (for example, ZrO2 based materials, HfO2 based materials, TiO2 based materials, rare earth oxide based materials, ternary oxide based materials, etc.), nitride-based films (for example, TaN, TiN, NbN) that are used as electrodes, or metal-containing or metal-alloy-based films (for example, InGaAs, InxOy (x=0.5 to 1.5, y=0.5 to 1.5), InSnO (ITO), InGaZnO (IGZO), InN, InP, InAs, InSb, In2S3, or In(OH)3, etc.) that are the stronger contenders for the future replacement of silicon in CMOS systems. One of ordinary skill in the art will recognize that the terms “film” or “layer” used herein refer to a thickness of some material laid on or spread over a surface and that the surface may be a trench or a line. Throughout the specification and claims, the wafer and any associated layers thereon are referred to as substrates.
Please note that the films or layers to be etched, such as silicon oxide or silicon nitride, may be listed throughout the specification and claims without reference to their proper stoichiometry (i.e., SiO2, SiO3, Si3N4). The layers may include pure (Si) layers, such as crystalline Si, poly-silicon (p-Si or polycrystalline Si), or amorphous silicon; silicon carbide (SioCp) layers, silicon nitride (SikNl) layers; silicon oxide (SinOm) layers; or mixtures thereof, wherein k, l, m, n, o, and p inclusively range from 0.1 to 6. For instance, silicon nitride is SikNl, where k and l each range from 0.5 to 1.5. More preferably silicon nitride is Si3N4. Herein, SiN in the following description may be used to represent SikNl containing layers. For instance, silicon oxide is SinOm, wherein n ranges from 0.5 to 1.5 and m ranges from 1.5 to 3.5. Preferably, the silicon oxide layer is SiO2. Herein, SiN and SiO in the following description are used to represent SikNl and SinOm containing layers, respectively. The silicon-containing film could also be a silicon oxide based dielectric material such as organic based or silicon oxide based low-k dielectric materials such as the Black Diamond II or III material by Applied Materials, Inc. with a formula of SiOCH. Alternatively, any referenced silicon-containing layer may be pure silicon. Silicon-containing film may also include SiaObCcNdHe where a, b, c, d, e range from 0.1 to 6 and b, c, d, e≥0 independently. The silicon-containing films may also include dopants, such as B, C, P, As Ga, In, Sn, Sb, Bi and/or Ge.
The term “pattern etch” or “patterned etch” refers to etching a non-planar structure, such as a stack of silicon-containing films below a patterned hardmask layer.
As used herein, the term “etch” or “etching” means to use an etching compound and/or a plasma to remove material via ion bombardment, remote plasma, or chemical vapor reaction between the etching gas and substrate and refers to an isotropic etching process and/or an anisotropic etching process. The isotropic etch process involves a chemical reaction between the etching compound and the substrate resulting in part of material on the substrate being removed. This type of etching process includes chemical dry etching, vapor phase chemical etching, thermal dry etching, or the like. The isotropic etch process produces a lateral or horizontal etch profile in a substrate. The isotropic etch process produces recesses or horizontal recesses on a sidewall of a pre-formed aperture in a substrate. The anisotropic etch process involves a plasma etching process (i.e., a dry etch process) in which ion bombardment accelerates the chemical reaction in the vertical direction so that vertical sidewalls are formed along the edges of the masked features at right angles to the substrate (Manos and Flamm, Thermal etching an Introduction, Academic Press, Inc. 1989 pp. 12-13). The plasma etching process produces a vertical etch profile in a substrate. The plasma etching process produces vertical vias, apertures, trenches, channel holes, gate trenches, staircase contacts, capacitor holes, contact holes, slit etch, self-aligned contact, self-aligned vias, super vias etc., in the substrate.
The term “mask” refers to a layer that resists etching. The mask layer may be located above the layer to be etched. The mask layer also refers to a hardmask layer. The mask layer may be an amorphous carbon (a-C) layer, a doped a-C layer, a photoresist layer, an anti-reflective layer, an amorphous silicon (a-Si) layer, an organic planarization layer, and combinations thereof. The mask layer may also be a silicon layer, such as poly-Si, metal oxide such as Ti, Al, Zr, Hf, etc., oxide, and combinations thereof.
The term “aspect ratio” refers to a ratio of the height of a trench (or aperture) to the width of the trench (or the diameter of the aperture).
The term “high aspect ratio” or “HAR” used herein refers to an aspect ratio is exceeding value of 5.
The term “high aspect ratio etching” or “HAR etching” used herein refers to the formation of a vertical hole or aperture pattern in an etching target film by the disclosed plasma etching method when aspect ratio of formed vertical apertures is exceeding value of 5.
The term “etch stop” refers to a layer below the layer to be etched that protects layers underneath.
The term “device channel” refers to layers that are part of actual device and any damage to it will affect device performance.
The term “selectivity” means the ratio of the etch rate of one material to the etch rate of another material. The term “selective etch” or “selectively etch” means to etch one material more than another material, or in other words to have a greater or less than 1:1 etch selectivity between two materials.
The terms “via”, “aperture”, “trench”, and “hole” are sometimes used interchangeably, and generally mean an opening in an interlayer insulator.
As used herein, the term “hydrocarbon” refers to a saturated or unsaturated function group containing exclusively carbon and hydrogen atoms. As used herein, the term “alkyl group” refers to saturated functional groups containing exclusively carbon and hydrogen atoms. An alkyl group is one type of hydrocarbon. Further, the term “alkyl group” refers to linear, branched, or cyclic alkyl groups. Examples of linear alkyl groups include without limitation, methyl groups, ethyl groups, propyl groups, butyl groups, etc. Examples of branched alkyls groups include t-butyl, but are not limited to. Examples of cyclic alkyl groups include without limitation, cyclopropyl groups, cyclopentyl groups, cyclohexyl groups, etc.
The term “organic film” used herein refers to a film formed with organic precursors, including a layer of amorphous carbon (a-C) and a layer of amorphous silicon (a-Si).
The term “Si-containing hydrofluorocarbon compounds” used herein refers to compounds have a general formula:
CxHyFzSin (1)
wherein 1≤x≤6, 1≤y≤9, 1≤z≤15, n=1 or 2, wherein the compound contains at least one methyl group. In some embodiments, the at least one methyl group is attached to Si atom in the Si-containing hydrofluorocarbon compounds. In some embodiments, the at least one methyl group is not attached to Si atom in the Si-containing hydrofluorocarbon compounds.
As used herein, the term “plasma etching” refers to the etching method when use of plasma involved for removal of etching target films not protected by a mask by means of ion bombardment or interaction with reactive species formed in the plasma or plasma afterglow which results in the formation of volatile byproducts that may be effectively removed from the substrate.
Note that herein, the terms “film”, “layer” and “material” may be used interchangeably. It is understood that a film may correspond to, or related to a layer or a material, and that the layer or material may refer to the film. Furthermore, one of ordinary skill in the art will recognize that the terms “film” or “layer” used herein refer to a thickness of some material laid on or spread over a surface and that the surface may range from as large as the entire wafer to as small as a trench or a line.
Note that herein, the terms “etching compound”, “etchant”, “etching gas”, “etch gas”, and “process gas” may be used interchangeably when the etching compound is in a gaseous state under room temperature and ambient pressure. It is understood that an etching compound may correspond to, or related to an etching gas or an etchant or a process gas, and that the etching gas or the etchant or the process gas may refer to the etching compound.
Note that herein, the terms “etching film”, “etching material”, “etching target film”, “target film”, “processing film” and “processing material” may be used interchangeably. It is understood that an etching film may correspond to, or related to an etching material or an etching target film or a processing film or a processing material, and that the etching target film or the processing film or the processing material may refer to the etching film.
The terms “via”, “aperture”, “slit”, “hole” and “structure” are used interchangeably, and generally mean an opening or recess in an interlayer insulator or an opening or recess in a substrate or wafer.
As used herein, the abbreviation “NAND” refers to a “Negated AND” or “Not AND” gate; the abbreviation “2D” refers to 2 dimensional gate structures on a planar substrate; the abbreviation “3D” refers to 3 dimensional or vertical gate structures, wherein the gate structures are stacked in the vertical direction.
The standard abbreviations of the elements from the periodic table of elements are used herein. It should be understood that elements may be referred to by these abbreviations (e.g., Si refers to silicon, N refers to nitrogen, O refers to oxygen, C refers to carbon, H refers to hydrogen, F refers to fluorine, etc.).
The unique CAS registry numbers (i.e., “CAS”) assigned by the Chemical Abstract Service are provided to help better identify the molecules disclosed.
The term “independently” when used in the context of describing R groups should be understood to denote that the subject R group is not only independently selected relative to other R groups bearing the same or different subscripts or superscripts, but is also independently selected relative to any additional species of that same R group. For example in the formula MR1x (NR2R3)(4-x), where M is an atom, x is 2 or 3, the two or three R1 groups may, but need not be identical to each other or to R2 or to R3. Further, it should be understood that unless specifically stated otherwise, values of R groups are independent of each other when used in different formulas.
Ranges may be expressed herein as from about one particular value, and/or to about another particular value. When such a range is expressed, it is to be understood that another embodiment is from the one particular value and/or to the other particular value, along with all combinations within said range. Any and all ranges recited herein are inclusive of their endpoints (i.e., x=1 to 4 or x ranges from 1 to 4 includes x=1, x=4, and x=any number in between), irrespective of whether the term “inclusively” is used.
Reference herein to “one embodiment” or “an embodiment” means that a particular feature, structure, or characteristic described in connection with the embodiment may be included in at least one embodiment of the invention. The appearances of the phrase “in one embodiment” in various places in the specification are not necessarily all referring to the same embodiment, nor are separate or alternative embodiments necessarily mutually exclusive of other embodiments. The same applies to the term “implementation.”
For a further understanding of the nature and objects of the present invention, reference should be made to the following detailed description, taken in conjunction with the accompanying drawings, in which like elements are given the same or analogous reference numbers and wherein:
Disclosed are methods or processes of plasma dry etching using a vapor of Si-containing hydrofluorocarbon etching compound, preferably a vapor of methyl-silyl-hydrofluorocarbon etching compound, as etching gas applied in plasma etching processes including high aspect ratio (HAR) plasma etching processes, selective plasma etching processes and cyclic plasma etching processes for fabrication of semiconductor structures, such as 3D NAND structures, contact holes, DRAM capacitors, etc., but not limited to those applications. The disclosed plasma dry etching methods provide a novel chemistry to etch off silicon-containing films, organic films, metal-containing films or the like, and control formed structure profiles in the plasma etching processes. Protection of sidewalls by controlling plasma-deposited polymers during plasma dry etching is a key mechanism to keep a defined profile without distortions. The disclosed plasma dry etching methods also provide a novel chemistry to control the profile of the plasma-deposited polymers during the plasma etching processes. Furthermore, use of the disclosed Si-containing hydrofluorocarbon compounds in a cyclic plasma etching process allows enhancing control of the shape or profile of etched structures while keeping etch rate comparable.
The disclosed methods of plasma dry etching comprise methods of selective HAR plasma dry etching silicon-containing films over a patterned mask layer, selective plasma dry etching silicon-containing films versus other non-etching films, selective plasma dry etching organic films or metal-containing films versus other non-etching films, and cyclic selective plasma dry etching silicon-containing films, organic films and metal-containing films versus other non-etching films, employing the disclosed Si-containing hydrofluorocarbon etching compounds, preferably methyl-silyl-hydrofluorocarbon etching compounds.
Most of semiconductor devices are formed using processes of formation of thin films on top of a substrate and patterning of those films to receive desired structures and devices. Patterning includes lithography step, which allows defining a formed pattern and etching steps that are used to remove unnecessary materials or films from the substrate through the formed pattern. One of commonly used etching processes is a plasma dry etching when the substrate is exposed to plasma or reactive species formed in the inside of a process chamber. Combination of physical (e.g., sputtering by ion bombardment) and chemical (e.g., surface interactions with reactive species) mechanisms in plasma etching allows achieving preferential etching of a particular material selectively to other materials depending on used chemistry and process conditions.
The disclosed herein includes selective plasma etching processes that is one of key processing for patterning of thin films during fabrication of advanced semiconductor devices. The selective plasma etching processes may selectively etch undesired materials vertically, such as 3D NAND structures, contact holes, etc., and horizontally such as multiple materials on the surface of a substrate. Plasma etching is used almost in all steps of semiconductor chip fabrication that requires patterning (e.g., front end of line, back end of line, and middle end of line). Most critical parameters for the plasma etching are etch rate (to keep it high throughput during the fabrication of the semiconductor device), selectivity (to reduce damages or unintentional modifications of non-etching film), constant process development ongoing to achieve high etch rate while keeping high selectivity and an increase of the portfolio of etching materials/gases which could be processed selectively to each other.
In particular, in some cases, it is possible to achieve so-called infinite selective etching, when the etching target material is etched but some polymer is deposited on non-etching materials preserving it from etching. Typically, infinite selectivity comes at cost of lower etch rate comparing to processes with lower selectivity. In addition, if long etching process is needed infinite selectivity may lead to deposit a thick polymer film on the surface of non-etching materials, electrodes of the plasma etching device and plasma etching chamber itself, which requires further processing or cleaning to remove the deposited polymer film. In some cases, deposition of polymer may limit the applicability of infinite selectivity etching process. A possible solution to solve the problem of excessive polymer deposition during etching with infinite selectivity is to use a cyclic etching process, where undesired deposited polymer is removed during one of steps inside an etching cycle. The disclosed herein comprises cycling etching processes featuring introduction of a Si-containing hydrofluorocarbon to at least one of the steps inside etching cycles, which allows etching of etching target material with high selectivity versus non-etching materials and to keep non-etching materials and chamber walls close to their initial conditions after cyclic etching process.
The disclosed Si-containing hydrofluorocarbon compounds have a general formula:
CxHyFzSin (I)
where 1≤x≤6, 1≤y≤9, 1≤z≤15, n=1 or 2.
In some embodiments, the Si-containing hydrofluorocarbon compounds in formula (I) may be methyl-silyl-hydrofluorocarbons containing one or more methyl group(s).
In some embodiments, the Si-containing hydrofluorocarbon compounds in formula (I) may be methyl-silyl-hydrofluorocarbons containing one or more methyl group(s) in which at least one methyl group is attached to the Si atom.
In some embodiments, the Si-containing hydrofluorocarbon compounds in formula (I) may be methyl-silyl-hydrofluorocarbons containing one or more methyl group(s) in which none of the one or more methyl group(s) is attached to the Si atom.
In some embodiments, the Si-containing hydrofluorocarbon compounds may not contain any methyl groups.
The disclosed Si-containing hydrofluorocarbon compounds may be used for promotion of the passivation process during HAR etching. Main feature of the disclosed Si-containing hydrofluorocarbon compounds is the formation of species with Si atom under plasma conditions and at least one methyl group attached to Si atom that promotes the formation of a Si-containing polymer on the surface of a substrate.
Rich deposition of a robust polymer on surfaces of the substrate achieved by the use of Si-containing hydrofluorocarbon may be used for the promotion of the passivation process during HAR etching. Therefore, a vapor of any Si-containing hydrofluorocarbon compounds covered by the formula (I) with at least one methyl group attached to Si, such as CH4F2Si, CH3F3Si, C2H6F2Si, C3H9FSi, C4H9F3Si, C5H9F5Si, C4H10F4Si2, C2H6F4Si2, C3H9F3Si2, and C6H9F7Si, may be used for selective plasma etching. Use of the Si-containing hydrofluorocarbons with at least one methyl group attached to Si allows to deposit a robust polymer at a fast deposition rate; however, in general, the presence of Si atom in the hydrofluorocarbon will allow to deposit more robust polymer comparing to commonly used hydrofluorocarbon or fluorocarbon gas due to incorporation of Si into the deposited polymer, even in absence of methyl group attached to silicon or in the case when a Si-containing hydrofluorocarbon molecule contains methyl group not attached to Si atom.
Exemplary disclosed Si-containing hydrofluorocarbon etching compounds are listed in Table 1, in which their structure formula, CAS numbers and boiling points are included. These molecules are commercially available or may be synthesized by methods known in the art. The disclosed Si-containing hydrofluorocarbon etching compounds may also include their isomers.
As summarized in Table 1, not only Si-containing hydrofluorocarbons with methyl group attached to Si, such as C4H9F3Si and C5H9F5Si, may be used for the plasma etching process, but also their isomers and isomers of other Si-containing hydrofluorocarbons with at least one methyl group attached to Si may be used for the plasma etching process with molecular formula from the list of CH4F2Si, CH3F3Si, C2H6F2Si, C3H9FSi, C3H9F3Si, C5H9F5Si, C6H9F7Si, C4H10F4Si2, C2H6F4Si2.
Furthermore, besides the Si-containing hydrofluorocarbons that contain methyl group(s) and have at least one methyl attached to Si atom used for dry etching process as an etching gas, vapors of the Si-containing hydrofluorocarbons that may not have isomers with at least one methyl group attached to the Si atom or the Si-containing hydrofluorocarbons that may not have isomers with one or more methyl group(s), may also be used for dry etching process as an etching gas, for example, CHF3Si, CH2F2Si, CH3FSi, CHF5Si, CH2F4Si, C2HF7Si, C2H2F6Si, C2H3F5Si, C2H4F4Si, C2H4F2Si, C2H3F3Si, C2H2F4Si, C2HF5Si, C3H4F6Si, C3H4F6Si, C3HF7Si, C3H3F5Si, C3H4F4Si, C3H5F3Si, C4H5F7Si, C4H3F9Si, C4H2F10Si, C4HF11Si, C5H8F6Si, C5H7F7Si, C6HF15Si, C6H4F12Si, and C6H7F9Si. Furthermore, the Si-containing hydrofluorocarbons may contain two Si atoms that may not have isomers with methyl group(s) attached to Si atoms, such as CH5FSi2, CH3F3Si2, CH2F6Si2, C2H7F3Si2, C2H9FSi2, C2H4F6Si2, C2HF7Si2, C2H2F6Si2, C2H3F5Si2, C2H4F4Si2, C3H4F8Si2, C3H6F4Si2, C4H10F4Si2, C4H6F6Si2, C4H11FSi2, and C4H8F2Si2. The above mentioned Si-containing hydrofluorocarbons may be used for dry etching process as an etching gas due to the presence of Si atom in the hydrofluorocarbon which will allow to deposit more robust polymer comparing to commonly used hydrofluorocarbon or fluorocarbon gases due to incorporation of the Si into the deposited polymer, even in absence of methyl group attached to silicon. As stated above, the other Si-containing hydrofluorocarbons not having isomers with methyl group(s) attached to Si or not having isomers with methyl group(s) may be used for dry etching process as an etching gas to increase selectivity and etching profile control in the case of HAR etching.
Considering the examples of the Si-containing hydrofluorocarbon etching compounds and their isomers listed in Table 1, and the study described in Examples that follow, it may be summarized that the vapor of any Si-containing hydrofluorocarbons and Si-containing hydrofluorocarbons may be used for plasma etching process as an etching gas, in particular any Si-containing hydrofluorocarbons that are covered by the formula (I). Preferably, in the Si-containing hydrofluorocarbons at least one methyl group attached to Si atom due to capability of depositing a robust polymer and enhancing an etching process selectivity.
The disclosed Si-containing hydrofluorocarbon compounds covered by the formula (I) include CH4F2Si, CH3F3Si, C2H6F2Si, C3H9FSi, C4H9F3Si, C5H9F5Si, C4H10F4Si2, C2H6F4Si2, C3H9F3Si2, C6H9F7Si, or their isomers that have at least one methyl group attached to Si atom.
The disclosed Si-containing hydrofluorocarbon compound is CH3F3Si, C2H6F2Si, C4H9F3Si, C5H9F5Si or their isomers.
The disclosed Si-containing hydrofluorocarbon compound is CH3F3Si or its isomers.
The disclosed Si-containing hydrofluorocarbon compound is C2H6F2Si or its isomers.
The disclosed Si-containing hydrofluorocarbon compound is C4H9F3Si or its isomers.
The disclosed Si-containing hydrofluorocarbon compound is C5H9F5Si or its isomers.
In some embodiments, the disclosed Si-containing hydrofluorocarbon compounds and their isomers that are covered by the formula (I) but do not contain methyl group(s). This type of the compounds may include some of the isomers of CHF3Si, CH2F2Si, CH3FSi, CHF5Si, CH2F4Si, C2HF7Si, C2H2F6Si, C2H3F5Si, C2H4F4Si, C2H4F2Si, C2H3F3Si, C2H2F4Si, C2HF5Si, C3H4F6Si, C3HF9Si, C3HF7Si, C3H3F5Si, C3H4F4Si, C3H5F3Si, C4H5F7Si, C4H3F9Si, C4H2F10Si, C4HF11Si, C5H8F6Si, C5H7F7Si, C6HF15Si, C6H4F12Si, C6H7F9Si, which may be used as an etching gas in the disclosed plasma dry etching processes even though they do not contain methyl groups.
The boiling point of the disclosed Si-containing hydrofluorocarbon compounds may range from approximately −50° C. to approximately 250° C., preferably, the boiling point of the disclosed Si-containing hydrofluorocarbon compounds may range from approximately −30° C. to approximately 200° C., more preferably, the boiling point of the disclosed Si-containing hydrofluorocarbon compounds may range from approximately −20° C. to approximately 150° C. Even more preferably. the boiling point of the disclosed Si-containing hydrofluorocarbon compounds may range from approximately 20° C. to approximately 150° C.
The disclosed Si-containing hydrofluorocarbon etching compounds are provided at greater than 95% v/v purity, preferably at greater than 99.99% v/v purity, and more preferably at greater than 99.999% v/v purity. The disclosed Si-containing hydrofluorocarbon etching compounds contain less than 5% by volume trace gas impurities, with less than 150 ppm by volume of impurity gases, such as N2 and/or H2O and/or CO2, contained in said trace gaseous impurities. Preferably, the water content in the plasma etching gas is less than 20 ppm by weight. The purified product may be produced by distillation and/or passing the gas or liquid through a suitable adsorbent, such as a 4 Å molecular sieve. The disclosed Si-containing hydrofluorocarbon etching compounds contain less than 10% v/v, preferably less than 1% v/v, more preferably less than 0.1% v/v, and even more preferably less than 0.01% v/v of any of its isomers, which may be purified by distillation of the gas or liquid to remove isomers and may provide better process repeatability.
Alternatively, the disclosed Si-containing hydrofluorocarbon etching compounds may contain between 0.01% v/v and 99.99% v/v of its isomers, particularly when the isomer mixture provides improved process parameters or if isolation of the target isomer is too difficult or expensive. The mixture of isomers may also reduce the need for two or more gas lines to the reaction chamber. Some of the disclosed Si-containing hydrofluorocarbon etching compounds are gaseous at room temperature and atmospheric pressure. For the non-gaseous (i.e., liquid or solid) compounds, their gas form may be produced by vaporizing the compounds through a conventional vaporization step, such as direct vaporization or by bubbling with inert gas (such as N2, Ar, He). The non-gaseous compounds may be fed in liquid state to a vaporizer where it is vaporized before it is introduced into a reactor.
In the disclosed methods of plasma dry etching, plasma etching gas is a gas mixture including at least one of following substances: a Si-containing hydrofluorocarbon, an oxidizing gas, an inert gas, fluorocarbon and/or hydrofluorocarbon-based chemicals, or another additional gas. The inert gas may be selected from He, Ar, Kr, Xe, or Ne; the oxidizing gas may be selected from O2, O3, CO, CO2, COS, SO, SO2, FNO, NO, NO, NO2, N2O, or H2O; the additional gas may be selected from H2, SF6, NF3, N2, NH3, Cl2, BCl3, BF3, Br2, F2, HBr, HCl or combinations thereof. The Si-containing hydrofluorocarbon is preferably a gas of hydrofluorocarbon compound and containing Si atom with at least one methyl group (—CH3) attached to Si atom to form molecular fragments including Si atom with several methyl groups attached to promote deposition process on non-etching materials for increase of selectivity. This is preferable due to capability to etch list of etching target materials while depositing (meaning infinite selectivity) on other non-etching materials. Furthermore, in the disclosed plasma etching methods, the Si-containing hydrofluorocarbon is preferably a gas of a compound represented by a composition formula (I). Using the inert gas is for generation of plasma and promotion of ion bombardment during the etching process and depending on gas ratio promotes or suppresses dissociation of other gases in the etching gas mixture, which causes direct impact on etching speed and anisotropy of the etching process. An addition of the oxidizing gas to the etching gas mixture allows increasing etching speed, promoting isotropic etching and surface or gas phase chemical reactions, and increasing selectivity of the etching process, depending on the etching gas mixture and type of etching and non-etching materials. The additional gas mentioned above may improve control of process or increase etch rate. The fluorocarbon or hydrofluorocarbon gas may promote both anisotropic etching process of etch film and vertical surface and/or non-etching film passivation. Examples of the fluorocarbon gases that may be used in the disclosed plasma etching method include, but is not limited to, CF4, C2F6, C3F6, C4F6, C4F8, C5F8, C5F10, C6F12, C7F14, C8F16, of the like. Examples of the hydrofluorocarbon gases that may be used in the disclosed plasma etching method include, but is not limited to, CH2F2, CH3F, CHF3, C2H5F, C3H7F, C5H7F, C3H2F6, C3H4F2, C3H2F4, C4H2F6, C4H3F7, or the like.
Under the plasma condition, various reactive species and ions are generated directly by dissociation of these compounds and chemical reactions through interaction between species presented in gas phase. Typically, plasma etching effect may be achieved with any of compounds represented by above mentioned compounds, when the above mentioned compounds are used individually or mixed with each other. Depending on the structure of individual compound, it may promote either etching performance (including increase of etching speed of particular etching material) or passivation during high aspect ratio etching process. In particular, a mixture of C4F6 and C4F8 is one of commonly used mixtures because C4F6 is efficient for promotion of passivation and C4F8 is efficient for increase of etching speed, resulting in a high anisotropy of etching processes as discussed in the Comparative Example 6 that follows. Furthermore, a hydrofluorocarbon gas such as CH2F2 may be added to increase the etching speed of silicon nitride film if it is desired.
In order to achieve HAR of etched structures and improve etching selectivity to certain materials or films while keeping high etch rate, etching gases may be chosen to form preferentially volatile byproducts with the etching material while not reacting with non-etching material forming less volatile byproducts. It has been discovered throughout the disclosed methods of plasma dry etching that the addition of Si-containing hydrofluorocarbons covered by the formula (I) to the process etching gas mixture allows to dramatically increase selectivity and aspect ratio during etching of Si-containing compound materials.
In the case of plasma etching processes disclosed herein, etching based on chemical reaction may be combined with physical sputtering by ion bombardment. Gases used for plasma etching are typically dissociated by plasma resulting in presence of large number of reactive species which are capable of deposition or etching or surface functionalization. This brings additional way of selective etching, when material is removed in the same time some film is deposited on non-etching material. This approach allows achieving large values of selectivity during etching process and the deposited film may be removed after the etching process or removed during the etching process.
In the disclosed plasma etching methods, use of Si-containing hydrofluorocarbons in the etching gas mixture allows achieving high or even infinite selectivity of etching target materials to other non-etching materials while keeping relatively high etching rate. Selectivity is achieved by deposition of a robust polymer on non-etching materials while the polymer is not deposited on (or react with) the etching target material. Capability of depositing a robust polymer during etching process is attributed to formation of Si-containing fragments with methyl groups attached directly to Si atom by dissociation of the Si-containing hydrofluorocarbons. Molecules having Si and methyl groups with the methyl groups attached to the Si is commonly used as a precursor for deposition of Si-containing films, which correlates well with observed results in the disclosed methods, e.g., use of trifluoromethylsilane (C4H9F3Si) results in generation of trimethylsilane fragments (C3H9Si) by dissociation of parent molecules in plasma due to weak bounding between Si atom and trifluoromethyl group in trimethylsilane molecule.
Various disclosed methods of plasma dry etching applying the above descriptions are described herein below.
In some embodiments, the disclosed method of plasma dry etching silicon-containing films is applied to etch a substrate having one or more processing or etching films (e.g. silicon oxide, silicon nitride or combinations thereof) and one or more non-etching films (e.g. amorphous carbon, amorphous silicon, doped amorphous carbon, doped amorphous silicon, metals, etc.) in HAR etching processes for fabrication of semiconductor structures, such as 3D NAND structures, contact holes, DRAM capacitors, etc., but are not limited to those applications. The disclosed method of plasma dry etching one or more processing films for forming a HAR aperture in a substrate comprise the steps of:
The one or more processing films may be silicon-containing films including SiaObCcNdHe where a, b, c, d, e range from 0.1 to 6 and b, c, d, e each may be independently 0. The one or more processing films may also include dopants, such as B, C, P, As Ga, In, Sn, Sb, Bi and/or Ge. The non-etching films may be patterned hardmask layers, e.g. amorphous carbon, amorphous silicon, doped amorphous carbon, doped amorphous silicon, metals, etc.
The term “high aspect ratio aperture” or “HAR aperture” used herein refers to the formation of an aperture pattern in an etching target film by the disclosed plasma etching method when aspect ratio of formed aperture structures is exceeding value of 5. High anisotropy (etching of exposed target material preferentially in a substantial vertical direction) of a plasma etching process is required to achieve HAR of etched apertures (see
Example of initial structure of a substrate including plasma etching film and non-etching film with some openings is presented in
Selection of etching gases and ratio of each gas concentration in an etching gas mixture is required to achieve balance between deposition process for protection of vertical surfaces (hereafter “passivation”) and etching process for anisotropic removal of materials. Typically, a combination or a mixture of etching gases is used, where each gas type is playing different role. The processing etching gas mixture used in the disclosed methods of plasma dry etching silicon-containing films may include at least one disclosed Si-containing hydrofluorocarbon (e.g., CH3F3Si, C2H6F2Si, C4H9F3Si, C5H9F5Si), at least one fluorocarbon or hydrofluorocarbon gas (e.g. C4F8, C4F6, CF4, CH2F2), optionally at least one inert gas (e.g. He, Ar, Kr, Xe, Ne), optionally an oxidizing gas (e.g. O2, O3, CO, CO2, COS, SO, SO2, FNO, NO, N2O, NO2, H2O, Cl2, F2). optionally an additional gas selected from H2, SF6, NF3, N2, NH3, Cl2, BCl3, BF3, Br2, F2, HBr, HCl or combinations thereof, which are used for the formation of reactive species and ions in a plasma. Besides, at least one fluorocarbon or hydrofluorocarbon gas, selected from CF4, C2F6, C3F6, C4F6, C4F8, C5F8, C5F10, C6F12, C7F14, C8F16, CH2F2, CH3F, CHF3, C2H5F, C3H7F, C5HF7, C3H2F6, C3H4F2, C3H2F4, C4H2F6, C4H3F7, or the like, may be added to the etch gas mixture.
More specifically, the disclosed plasma etching methods have the following steps. In the first step, a substrate containing one or more films including optionally non-etching films that may be patterned, i.e., having some patterns such as openings or apertures in the film, is placed on a mounting table or a substrate holder in a plasma etching chamber or a reactor. The substrate may be any types of etching target materials as long as it could be processed by plasma etching. For example, monocrystalline Si wafer including at least one Si-containing film, organic film or metal containing film or plural films part of which may be patterned. Example of the substrate having the films and non-etching films with pattern is shown in
The disclosed plasma etch methods using the disclosed Si-containing hydrofluorocarbon compounds as etching gas produce apertures, such as channel holes, gate trenches, staircase contacts, capacitor holes, contact holes, contact etch, slit etch, self-aligned contact, self-aligned vias, super vias etc., in the silicon-containing films. The resulting apertures may have an aspect ratio ranging from approximately 5:1 to approximately 500:1, preferably from approximately 20:1 to approximately 400:1; and a diameter ranging from approximately 5 nm to approximately 500 nm, preferably less than 100 nm. For example, one of ordinary skill in the art will recognize that a channel hole etch produces apertures in the silicon-containing films having an aspect ratio greater than 50:1.
In some embodiments, the disclosed methods of plasma dry etching include methods of selective plasma dry etching silicon-containing films employing the disclosed Si-containing hydrofluorocarbon etching compounds. The disclosed methods of selective plasma dry etching of silicon-containing films may process a substrate having one or more etching target films, e.g., silicon oxide, silicon nitride or combinations thereof, and non-etching films, e.g., amorphous silicon, SiCN, SiC, doped amorphous silicon or the like, deposited thereon. The disclosed methods of selective plasma dry etching silicon-containing films provide a process of etching Si-containing materials or films with high selectivity over other materials or films. The disclosed methods of selective plasma dry etching silicon-containing films may be isotropic and anisotropic etching applied to form 2D and 3D active components on logic substrates, such as FinFET, Gate All Around (GAA)-FET or Forksheet-FET, etc.
The disclosed methods of selective plasma dry etching silicon-containing films provide a novel chemistry to increase of selectivity of etching target materials to non-etching materials by promotion of a polymer formation on the non-etching materials using an addition of the Si-containing hydrofluorocarbon to an etching gas mixture. In the disclosed plasma etching methods, the addition of the Si-containing hydrofluorocarbon to the etching gas mixture allows to inhibit etching of the non-etching materials by deposition of a polymer thereon while keeping etching target material at a reasonable etch rate resulting in high or even infinite value of selectivity. In particular, it is demonstrated that it is possible to etch silicon-containing films, such as SiO2 and Si3N4 with infinite selectivity to each other, and to amorphous carbon, polycrystalline silicon, W, SiC, SiON and SiCN, which are materials commonly used in multicolor etching and advanced patterning. The Examples 12 to 18 that follow are promising for selective etching of Si-containing compounds. The disclosed methods of selective plasma dry etching Si-containing films for forming a structure in a substrate comprises the steps of:
The one or more processing films may be silicon-containing films including SiaObCcNdHe where a, b, c, d, e range from 0.1 to 6 and b, c, d, e each may be independently 0. The one or more processing films may also include dopants, such as B, C, P, As Ga, In, Sn, Sb, Bi and/or Ge. The non-etching films may be all other materials used in fabrication of semiconductor devices at certain level such as, organic films (a-C or doped a-C film, a-Si, photoresist (PR), etc.), metal film, metal-containing film. The non-etching films may be other silicon-containing films different from the silicon-containing film to be etched but having the same formula as the silicon-containing film to be etched, that is, SiaObCcNdHe where a, b, c, d, e range from 0.1 to 6 and b, c, d, e each may be independently 0.
Example of initial structure of a substrate having multiple films including plasma etching films and non-etching films with some openings is presented in
Specifically, the disclosed methods aim to etch particular Si-containing compound (e.g., silicon oxide, silicon nitride) selectively to all other materials used in fabrication of semiconductor devices at certain level (e.g., front end of line or middle end of line) employing a mixed gas including at least one of following substances: at least one Si-containing hydrofluorocarbon, inert gas, oxidizing agent, optionally fluorocarbon and/or hydrofluorocarbon and additional gas as a processing etching gas mixture. The use of Si-containing hydrofluorocarbon in the processing etching gas mixture allows to achieve high or even infinite selectivity of silicon-containing films to other materials while keeping relatively high etching speed. The at least one Si-containing hydrofluorocarbon is covered by formula (I). The inert gas may be selected from He, Ar, Kr, Xe, Ne. The oxidizing gas may be selected from O2, O3, CO, CO2, SO, SO2, FNO, NO, NO, NO2, H2O, H2, or N2O. The additional gas may be any of the following gas: H2, SF6, NF3, N2, NH3, Cl2, BCl3, BF3, Br2, F2, HBr, HCl or combinations thereof. The optionally fluorocarbon and/or hydrofluorocarbon may be selected from one or more of CF4, C2F6, C3F6, C4F6, C4F8, C5F8, C5F10, C6F12, C7F14, C8F16, CH2F2, CH3F, CHF3, C2H5F, C3H7F, C5HF7, C3H2F6, C3H4F2, C3H2F4, C4H2F6, C4H3F7, or the like. A selectivity of the etching film to the at least one non-etching film may be larger than 5, preferably, larger than 10.
As stated above, for example, use of trifluoromethylsilane (C4H9F3Si) results in generation of trimethylsilane fragments (C3H9Si) by dissociation of parent molecules in plasma due to weak bounding between Si atom and trifluoromethyl group in trimethylsilane molecule, which allows deposition of a polymer in Example 14, which brings infinite selectivity discussed in the present disclosure.
In some embodiments, the disclosed methods of plasma dry etching include methods of selective plasma dry etching organic films or metal-containing films employing the disclosed Si-containing hydrofluorocarbon etching compounds. The disclosed methods of selective plasma dry etching organic or metal-containing films etch a substrate having one or more etching films (e.g., amorphous carbon and W-doped amorphous carbon), and non-etching films (e.g., polycrystalline silicon, silicon nitride, silicon oxide, metal or the like) deposited thereon. In particular, the disclosed selective etching methods aim to etch particular organic materials (e.g., a-C and doped a-C, a-Si, PR, etc.) or metal-containing films selectively to all other materials (e.g. Si-containing film, doped Si-containing film, etc.) used in fabrication of semiconductor device at certain level (e.g. front end of line or middle end of line) employing a mixed gas of at least one Si-containing hydrofluorocarbon, oxidizing agent, inert gas and optionally fluorocarbon and/or hydrofluorocarbon as an etching gas. The disclosed methods of selective plasma dry etching of organic films or metal-containing films comprise the steps of:
The amorphous carbon and W-doped amorphous carbon are one of common materials for 3D NAND high aspect ratio etching mask, self-align patterning mask, contact etch mask, etc. Using Si-containing hydrofluorocarbon is possible to dramatically increase the selectivity of the etching process to other materials. Adding the oxidizing gas (e.g., O2, O3, CO, CO2, SO, SO2, FNO, NO, N2O, NO2, H2O, H2, or N2O) and/or inert gas (e.g., He, Ar, Kr, Xe, Ne,) mixture to the etching gas may promote polymer deposition on non-etching materials. Highly selective etching of amorphous carbon and W-doped amorphous carbon over the non-etching films is promising for organic mask patterning and stripping and for patterning of other materials on the substrate.
Accordingly, the disclosed methods of selective plasma dry etching organic films or metal-containing films may enable a high selectivity of amorphous carbon and W-doped amorphous carbon over non-etching materials while keeping high etching rate of organic materials or metal-containing films presented on a substrate or a mask material for formation of a pattern on the mask material without damaging under layered materials.
The disclosed method of selective plasma dry etching organic films or metal-containing films may be used in selective etching for formation of a pattern on organic hard mask, stripping or patterning of another organic film on the substrate. The disclosed method of selective plasma dry etching of organic films or metal-containing films is a method of processing a substrate including one or more etching target film (e.g. amorphous carbon and doped amorphous carbon) and non-etching films (e.g. polycrystalline silicon, silicon nitride, silicon oxide, metal), when an etching gas mixture includes at least one Si-containing hydrofluorocarbon (e.g. C4H9F3Si), an inert gas (e.g. Ar), an oxidizing gas (e.g. O2), and an additional gas selected from H2, SF6, NF3, No, NH3, Cl2, BCl3BF3, Br2, F2, HBr, HCl or combinations thereof used for formation of reactive species and ions in the plasma. Here, hydrofluorocarbon or fluorocarbon gases may not be included in the etching gas mixture. The substrate may be any type of materials as long as it could be processed by plasma etching. A selectivity of the etching organic films or metal-containing film to the at least one non-etching film may be larger than 5, preferably, larger than 10.
Depending on etching process, selectivity to certain materials may be achieved by use of physical or chemical properties of materials presented on substrate and the etching gas. The addition of Si-containing hydrofluorocarbon to the etching gas mixture allows dramatically increasing selectivity during etching of organic materials or metal-containing films by deposition of polymer on non-etching materials. Example of initial structure of a substrate having an organic etching films or metal-containing films and non-etching films with some openings is presented in
In some embodiments, the disclosed methods of plasma dry etching include methods of cyclic selective plasma dry etching of silicon-containing films and metal-containing films employing the disclosed Si-containing hydrofluorocarbon etching compounds.
The disclosed methods of cyclic selective plasma dry etching of silicon-containing or metal-containing films etch a substrate including one or more etching target film, e.g. metal (e.g., platinum), silicon oxide, silicon nitride or combinations thereof and non-etching materials or films (e.g. amorphous silicon, SiCN, SiC, doped amorphous silicon), when an etching gas mixture including at least one Si-containing hydrofluorocarbon, optionally an oxidizing agent, optionally a fluorocarbon or hydrofluorocarbon gas and optionally at least one inert gas are used for formation of reactive species and ions in at least one step of cyclic plasma etching process. Etching process is performed in a cyclic way comprising several etching steps repeated in a sequence over the time, when conditions of each etching step may be altered depending on number of cycles. The substrate may be any type of materials as long as it could be processed by plasma etching. The disclosed methods of cyclic selective plasma dry etching silicon-containing or metal-containing films achieve high selectivity to non-etching materials while keeping high etch rate throughput to etching target films and low rate of polymer deposition on non-etching materials and etching chamber interior using a cyclic etching process. The disclosed methods of cyclic selective plasma dry etching of silicon-containing films or metal-containing films may be used in formation of structures by selective etching in front end of line, self-aligned multiple patterning, hard mask opening and etching, etc. The disclosed methods of cyclic selective plasma dry etching an etching film (such as silicon-containing films or metal-containing films) comprises:
Here, the first etching gas may contains the disclosed Si-containing hydrofluorocarbon, one or more hydrofluorocarbons or fluorocarbons, an oxidizing gas, an inert gas and/or an additional gas. The second etching gas may contains one or more hydrofluorocarbons or fluorocarbons, an oxidizing gas, an inert gas and/or an additional gas. The disclosed methods of cyclic selective plasma dry etching of silicon-containing films may further comprise introducing a third etching gas after the step v). Here, the third etching gas is the same as the second etching gas containing one or more hydrofluorocarbons or fluorocarbons, an oxidizing gas, an inert gas and/or an additional gas. However, in one or each cycle, the third etching gas and the second etching gas do not have the same combinations of etching gas compositions from each other. For example, if the second etching gas is a combination of C4F6, O2, Ar and CO2, then the third etching gas may be a combination of CH2F2, O2, Ar and SF6 or CH2F2, O3, He, and SF6. A purging step is applied to after using each etching gas, that is, the purging step is applied after steps iii) and v). During the purging, the electric power for generating the plasma may be still on or may turn off. After purging, the electric power for generating the plasma is turned on. Here, the one or more hydrofluorocarbons or fluorocarbons may be selected from CF4, C2F6, C3F6, C4F6, C4F8, C5F8, C5F10, C6F12, C7F14, C8F16, CH2F2, CH3F, CHF3, C2H5F, C3H7F, C5HF7, C3H2F6, C3H4F2, C3H2F4, C4H2F6 or C4H3F7; the oxidizing gas may be selected from O2, O3, CO, CO2, SO, SO2, FNO, N2, NO, N2O, NO2, or H2O, COS; the inert gas may be selected from the group consisting of He, Ar, Xe, Kr, or Ne; and the additional gas may be selected from H2, CO2, SF6, NF3, N2, NH3, Cl2, BCl3, HCl, HBr, or Br2.
The possibility to form a polymer on the surface of the substrate, depending on the material being exposed, brings another way of highly selective etching, when the material is removed during the etching process while some film is deposited on non-etching plasma etching materials. This approach allows achieving large values of selectivity, and the deposited film could be removed after the etching process or removed during the etching if a cyclic process is employed. The disclosed cyclic etching methods improve selectivity of etching of the etching target film while keeping high etch rate and low amount of the deposited polymer on the non-etching materials. The addition of Si-containing hydrofluorocarbon to the process gas mixture allows dramatically increasing the selectivity during the etching of Si-containing films and/or metal-containing films while the use of a cyclic process allows significant reduction of polymer growth while keeping high etch rate.
The disclosed cyclic etching process refers to the process when the substrate is processed in an etching chamber using etching steps which are repeated in a sequence. Example of substrate processed using cyclic etching is shown in
The disclosed methods of cyclic selective plasma dry etching of silicon-containing films include etching of particular materials, e.g. Si-containing films including silicon nitride, silicon oxide, and a-C selectively to any other materials used in fabrication of semiconductor device at certain level (e.g. front end of line or middle end of line) using a mixed gas of at least one Si-containing hydrofluorocarbon, optionally inert gas, oxidizing gas and fluorocarbon and/or hydrofluorocarbon as an etching gas while etching process further contains several steps with variable etching recipes repeated in a cyclic way. Use of cyclic etching process consisting of several steps allows achieving high or infinite values of selectivity while depositing insignificant amount of polymer or just forming thin film interface on surface of non-etching materials.
The disclosed cyclic plasma etching methods may achieve preferential etching of Si-containing compound with high selectivity to other materials such as mask materials and non-etching materials while not modifying non-etching materials.
In the disclosed cyclic plasma etching method, a plasma etching gas is a gas mixture including at least one of the following substances: a Si-containing hydrofluorocarbon, an inert gas, an oxidizing agent, a fluorocarbon and/or hydrofluorocarbon, and an additional gas. Once again, the inert gas may be selected from He, Ar, Kr. Xe, Ne; the oxidizing agent may be selected from O2, O3, CO, CO2, COS, SO, SO2, FNO, NO, N2O, NO2, N2O, Cl2, F2; the hydrofluorocarbons or fluorocarbons may be selected from CF4, C2F6, C3F6, C4F6, C4F8, C5F8, C5F10, C6F12, C7F14, C8F16, CH2F2, CH3F, CHF3, C2H5F, C3H7F, C5HF7, C3H2F6, C3H4F2, C3H2F4, C4H2F6 or C4H3F7; the additional gas may be selected from H2, SF6, NF3, N2, NH3, Cl2, BCl3, BF3, Br2, F2, HBr, HCl or combinations thereof. A selectivity of the etching film to the at least one non-etching film may be larger than 5, preferably, larger than 10.
In summary, in the disclosed plasma dry etching methods described above, an etching gas mixture includes at least one disclosed Si-containing hydrofluorocarbon compounds. In addition, at least one hydrofluorocarbon or fluorocarbon gases, at least one oxidizing gases, at least one inert gas, and/or at least one additional gas may be added to the disclosed Si-containing hydrofluorocarbon compounds forming the etching gas mixture before etching. In some embodiments, the at least one hydrofluorocarbon or fluorocarbon gases, at least one oxidizing gases, at least one inert gas, and/or at least one additional gas may be optional. For example, in the disclosed plasma etching methods of selective plasma dry etching organic films, at least one hydrofluorocarbon or fluorocarbon gases is optional and may or may not be included in the etching gas mixture.
Under the plasma condition, various reactive species and ions are generated directly by dissociation of these compounds and chemical reactions through interaction between species presented in the gas phase. Typically, plasma etching effect could be achieved with any of compounds represented by above mentioned compounds, when the above mentioned compounds are used individually or mixed with each other. Depending on the structure of individual compound, it may promote either etching performance (including increase of etching speed of particular etching target material) or passivation during high aspect ratio etching process. In particular, a mixture of C4F6 and C4F8 is one of commonly used mixtures because C4F8 is efficient for promotion of passivation and C4F8 is efficient for increase of etching speed, resulting in a high anisotropy of etching processes as discussed in the Comparative Example 6 that follows. Furthermore, hydrofluorocarbon gas such as CH2F2 may be added to increase the etching speed of silicon nitride film if it is desired.
Other gases such as an inert gas or an oxidizing gas may be added to the etching gas mixture. Using an inert gas is to increase ion bombardment during the etching process and depending on gas ratio promotes or suppresses dissociation of other gases in the etching gas mixture, which causes direct impact on etching speed and anisotropy of the etching process. Furthermore, an addition of the oxidizing gas to the etching gas mixture allows increasing the etching speed, depending on the etching gas mixture and type of target and non-etching materials isotropy and selectivity of the etching process. Furthermore, an additional gas selected from H2, SF6, NF3, N2, NH3, Cl2, BCl3, BF3, Br2, F2, HBr, HCl or combinations thereof may be added to the etching gas mixture in order to improve control of process or increase etch rate.
The disclosed etching gas mixtures are suitable for plasma etching semiconductor structures, such as, channel holes, gate trenches, staircase contacts, slits, capacitor holes, contact holes, self-aligned contact, self-aligned vias, super vias etc., in the silicon-containing films. The disclosed etching gas mixtures are not only compatible with currently available mask materials but also compatible with the future generations of mask materials because the disclosed Si-containing etching compounds induce little to no damage on the mask along with good profile of high aspect ratio structures. In other words, the disclosed etching gas mixtures may produce vertical etched patterns having minimal to no bowing, pattern collapse, or roughness. In order to achieve these properties, the disclosed etching gas mixtures may deposit an etch-resistant polymer layer during etching to help reduce the direct impact of the oxygen and fluorine radicals during the etching process. The disclosed etching gas mixtures may also reduce damage to p-Si or crystalline Si channel structure during etching.
Material compatibility tests are important to determine if any of the disclosed etching gas mixtures will react with chamber materials and degrade the performance of the chamber with short term or long-term use. Key materials involved in parts of the chamber, valves, etc. include stainless steel, aluminum, nickel, PCTFE, PVDF, PTFE, PFA, PP, kalrez, viton and other metals and polymers. At times these materials are exposed to high temperatures, for example, higher than 20° C., and high pressures, for example, higher than 1 atm, which may enhance their degradation. The metrology methods may include visual inspection, weight measurement, measuring nanometer scale changes in scanning electron microscopy (SEM), tensile strength, hardness, etc.
The disclosed etching gas mixtures may be used to plasma etch silicon-containing films on a substrate. The disclosed plasma etching method may be useful in the manufacture of semiconductor devices such as NAND or 3D NAND gates or Flash or DRAM memory capacitors or transistors such as fin-shaped field-effect transistor (FinFET). Gate All Around (GAA)-FET, Nanowire-FET, Nanosheet-FET, Forksheet-FET, Complementary FET (CFET), Bulk complementary metal-oxide-semiconductor (Bulk CMOS), MOSFET, fully depleted silicon-on-insulator (FD-SOI) structures. The disclosed etching gas mixtures may be used in other areas of applications, such as different front end of the line (FEOL) and back end of the line (BEOL) etch applications such as metal films patterning, formation of metal interconnects, buried power lines and signal lines. Additionally, the disclosed etching gas mixtures may also be used for etching Si in 3D through silicon via (TSV) etch applications for interconnecting memory to logic on a substrate and in MEMS applications.
The disclosed plasma etching method includes providing a reaction chamber having a substrate disposed therein. The reaction chamber may be any enclosure or chamber within a device in which etching methods take place such as, and without limitation, reactive ion etching (RIE), capacitively coupled plasma (CCP) with single or multiple frequency RF sources, inductively coupled plasma (ICP), or microwave plasma reactors, or other types of etching systems capable of selectively removing a portion of the silicon-containing film or generating active species. One of ordinary skill in the art will recognize that the different plasma reaction chamber designs provide different electron density and temperature control. Suitable commercially available plasma reaction chambers include but are not limited to the Applied Materials magnetically enhanced reactive ion etcher sold under the trademark eMAX™ or the Lam Research Dual CCP reactive ion etcher dielectric etch product family sold under the trademark 2300® Flex™. The RF power in such may be pulsed to control plasma properties and thereby improving the etch performance (selectivity and damage) further.
In the disclosed plasma etching method, the plasma etching chamber is equipped with parallel plate electrodes plasma generators where a high frequency electromagnetic field of frequency in range from 2 to 100 MHz is applied to the upper electrode or lower electrode or both electrodes and a low frequency electromagnetic field of frequency in range from 40 KHz to 2 MHz is applied to the lower electrode, when a gap between the electrodes is kept in a range between 10 and 35 mm. A combination of these electric fields allows to apply power to the upper electrode within a range of 0-10,000 W and to the lower electrode within the range of 0-100,000 W. Pressure in the etching chamber during the plasma etching process is kept between 5 and 100 mTorr with introduced the etching gas mixture. Alternatively, plasma-treated reactants of the disclosed etching gas mixtures may be produced outside of a reaction chamber. For example the MKS Instruments' ASTRONI® reactive gas generator or the like may be used to treat the reactants prior to passage into the reaction chamber. For example, operated at 2.45 GHz, 7 KW plasma power, and a pressure ranging from approximately 0.5 Torr to approximately 10 Torr, the reactant O2 may be decomposed into two O′ radicals. Preferably, the remote plasma may be generated with a power ranging from about 1 KW to about 10 KW, more preferably from about 2.5 KW to about 7.5 KW. The reaction chamber may contain one or more than one substrate. For example, the reaction chamber may contain from 1 to 200 silicon wafers having from 25.4 mm to 450 mm diameters. The substrates may be any suitable substrates used in semiconductor, photovoltaic, flat panel or LCD-TFT device manufacturing. Examples of suitable substrates include wafers, such as silicon, silica, glass, Ge, SiGe, GeSn, InGaAs, GaSb, InP, or GaAs wafers. The wafer will have multiple films or layers on it from previous manufacturing steps, including silicon-containing films or layers. The layers may or may not be patterned. Examples of suitable layers include without limitation silicon (such as amorphous silicon, p-Si, crystalline silicon, any of which may further be p-doped or n-doped with B, C, P, As, Ga, In, Sn, Sb, Bi and/or Ge), silica, silicon nitride, silicon oxide, silicon oxynitride, SiaObHcCdNe, (wherein a>0; b, c, d, e≥0), Ge, SiGe, GeSn, InGaAs, GaSb, InP; mask layer materials such as amorphous carbon with or without dopants, antireflective coatings, photoresist materials, a metal oxide, such as AlO, TiO, HfO, ZrO, SnO, TaO etc. or a metal nitride layer such as AIN, ZrN, SnN, HfN, titanium nitride, tantalum nitride etc. or combinations thereof; etch stop layer materials such as SiaObHcCdNe, (wherein a>0; b, c, d, e≥0) selected from silicon nitride, polysilicon, crystalline silicon, silicon carbide, SiON, SiCN or combinations thereof, or device channel materials such crystalline silicon, epitaxial silicon, doped silicon, or combinations thereof. The silicon oxide layer may form a dielectric material, such as an organic based or silicon oxide based low-k dielectric material (e.g., a porous SiCOH film). An exemplary low-k dielectric material is sold by Applied Materials under the trade name Black Diamond II or III. Additionally, layers comprising tungsten, cobalt, copper or noble metals (e.g. platinum, palladium, rhodium or gold) may be used. Furthermore, examples of the silicon-containing films may be SiaObHcCdNe, (wherein a>0; b, c, d, e≥0). Throughout the specification and claims, the wafer and any associated layers thereon are referred to as substrates.
The vapor of the disclosed etching gas mixture is introduced into the reaction chamber containing the substrate having silicon-containing films deposited thereon. The vapor of the disclosed etching gas mixture or the vapor of each component in the disclosed etching gas mixture may be introduced to the chamber at a flow rate ranging from approximately 0.1 sccm to approximately 1 sim. For example, for a 300 mm wafer size, the vapor may be introduced to the chamber at a flow rate ranging from approximately 1 sccm to approximately 50 sccm. Alternatively, for a 450 mm wafer size, the vapor may be introduced to the chamber at a flow rate ranging from approximately 25 sccm to approximately 250 sccm. One of ordinary skill in the art will recognize that the flow rate may vary from tool to tool. The disclosed Si-containing hydrofluorocarbon etching compounds and the hydrofluorocarbon or fluorocarbon compounds may be supplied either in neat form or in a blend with an inert gas, such as N2, Ar, Kr, Ne He, Xe, etc., or solvent. The disclosed Si-containing hydrofluorocarbon etching compounds and the hydrofluorocarbon or fluorocarbon compounds may be present in varying concentrations in the blend. For liquid Si-containing hydrofluorocarbon etching compounds and the hydrofluorocarbon or fluorocarbon compounds, the vapor form of the Si-containing hydrofluorocarbon etching compounds and the hydrofluorocarbon or fluorocarbon compounds may be produced by vaporizing the neat or blended Si-containing hydrofluorocarbon etching compound solution and the hydrofluorocarbon or fluorocarbon compound solution through a conventional vaporization step such as direct vaporization or by bubbling. The neat or blended Si-containing hydrofluorocarbon etching compounds and the neat or blended hydrofluorocarbon or fluorocarbon compounds may be fed in liquid state to a vaporizer where it is vaporized before it is introduced into the reactor.
Alternatively, the neat or blended Si-containing hydrofluorocarbon etching compounds may be vaporized by passing a carrier gas into a container containing the disclosed Si-containing hydrofluorocarbon etching compounds and the hydrofluorocarbon or fluorocarbon compounds or by bubbling the carrier gas into the disclosed Si-containing hydrofluorocarbon etching compounds and the hydrofluorocarbon or fluorocarbon compounds. The carrier gas may include, but is not limited to, Ar, He, N2, Kr, Xe, Ne and mixtures thereof. Bubbling with a carrier gas may also remove any dissolved oxygen present in the neat or blended Si-containing hydrofluorocarbon etching compound solution and the hydrofluorocarbon or fluorocarbon compound solution. The carrier gas and disclosed Si-containing hydrofluorocarbon etching compounds are then introduced into the reactor as a vapor.
If necessary, a container containing the disclosed Si-containing hydrofluorocarbon etching compounds may be heated to a temperature that permits the Si-containing hydrofluorocarbon etching compounds to be in liquid phase and to have a sufficient vapor pressure for delivery into an etching tool. The container may be maintained at temperatures in the range of, for example, approximately 0° C. to approximately 150° C., preferably from approximately room temperature to approximately 100° C., more preferably from approximately room temperature to approximately 50° C. More preferably, the container is maintained at room temperature in order to avoid heating lines to an etch tool. Those skilled in the art recognize that the temperature of the container may be adjusted in a known manner to control the amount of Si-containing hydrofluorocarbon etching compounds vaporized.
For 3D NAND applications, plasma activated vapor of the disclosed etching gas mixture or the disclosed plasma activated etching gas preferably exhibits high selectivity toward the mask and etches through the alternating layers of SiO and SiN or alternating layers of polysilicon and SiO2 resulting in a vertical etch profile with no profile distortion (such as bowing or roughness), which is important for 3D NAND applications. Additionally, the plasma activated vapor deposits polymer on sidewall to minimize feature profile deformation. For other applications, such as DRAM and 2D NAND, for example, the plasma activated vapor of the disclosed etching gas mixture under different process conditions may selectively etch SiO from SiN. The disclosed plasma activated etching gas may selectively etch SiO and/or SiN from mask layers, such as a-C, photoresist, a-Si, p-Si, or silicon carbide; or from metal contact layers, such as Cu, W, Ru, etc.; or from channel regions consisting of SiGe or polysilicon regions. The disclosed plasma activated etching gas may selectively etch organic films from other films, such as a-C, photoresist, a-Si, p-Si, or silicon carbide; or from metal contact layers, such as Cu, W, Ru, etc.; or from channel regions consisting of SiGe or polysilicon regions.
The disclosed activated etching gas mixture (e.g., through igniting a plasma of the etching gas mixture) including Si-containing hydrofluorocarbon etching gas reacts with the silicon-containing films deposited on the substrate to form volatile by-products that are removed from the reaction chamber. The a-C mask, antireflective coating, and photoresist layer on the substrate are less reactive with the activated etching gas. Thus, the activated etching gas selectively reacts with the silicon-containing films to form volatile by-products.
Alternatively, the disclosed activated etching gas mixture (e.g., through igniting a plasma of the etching gas mixture) including Si-containing hydrofluorocarbon etching gas reacts with organic films deposited on the substrate to form volatile by-products that are removed from the reaction chamber. In this case, with varying processes and different etching conditions, the organic films, such as a-C mask, are more reactive with the activated etching gas. Thus, the activated etching gas selectively reacts with the organic films to form volatile by-products.
Temperature and pressure within the reaction chamber are held at conditions suitable for the silicon-containing film to react with the activated etching gas. For instance, the pressure in the chamber may be held between approximately 0.1 mTorr and approximately 1000 Torr, preferably between approximately 1 mTorr and approximately 10 Torr, more preferably between approximately 10 mTorr and approximately 1 Torr, and more preferably between approximately 10 mTorr and approximately 100 mTorr, as required by the etching parameters. Likewise, substrate temperature in the chamber may range between about approximately −196° C. to approximately 500° C., preferably between approximately −120° C. to approximately 300° C., more preferably between approximately −100° C. to approximately 50° C.; and more preferably between approximately −70° C. to approximately 40° C. Chamber wall temperatures may range from approximately −196° C. to approximately 300° C. depending on the process requirements.
Alternatively, the temperature and the pressure within the reaction chamber are held at conditions suitable for the organic film to react with the activated etching gas. For instance, the pressure in the chamber may be held between approximately 0.1 mTorr and approximately 1000 Torr, preferably between approximately 1 mTorr and approximately 10 Torr, more preferably between approximately 10 mTorr and approximately 1 Torr, and more preferably between approximately 10 mTorr and approximately 100 mTorr, as required by the etching parameters. Likewise, the substrate temperature in the chamber may range between about approximately −196° C. to approximately 500° C., preferably between approximately −120° C. to approximately 300° C., more preferably between approximately −100° C. to approximately 50° C., and more preferably between approximately −70° C. to approximately 40° C. Chamber wall temperatures may range from approximately −196° C. to approximately 300° C. depending on the process requirements.
The reactions, between the silicon-containing film and the activated etching gas, and between the organic films and the activated etching gas, result in anisotropic removal of the silicon-containing films and the organic films from the substrate depending on process parameters. Atoms of nitrogen, oxygen, and/or carbon may also be present in the silicon-containing films and organic films. The removal is due to a physical sputtering of silicon-containing films and organic films from plasma ions (accelerated by the plasma) and/or by chemical reaction of plasma species to convert Si to volatile species, such as SiFx, wherein x ranges from 1-4.
The disclosed plasma etch methods using the disclosed Si-containing hydrofluorocarbon compounds as etching gas produce apertures, such as channel holes, gate trenches, staircase contacts, capacitor holes, contact holes, contact etch, slit etch, self-aligned contact, self-aligned vias, super vias etc., in the silicon-containing films. The resulting apertures may have an aspect ratio ranging from approximately 5:1 to approximately 500:1, preferably approximately 20:1 to approximately 400:1, and a diameter ranging from approximately 5 nm to approximately 500 nm, preferably less than 100 nm. For example, one of ordinary skill in the art will recognize that a channel hole etch produces apertures in the silicon-containing films having an aspect ratio greater than 50:1.
Typical materials that need to be etched may be SiO. A process of etching SiO may be relevant to etching trenches in Borophosphosilicateglass (BPSG), Tetraethylorthosilicate (TEOS), or low deposition rate TEOS (LDTEOS). An etch stop layer may be silicon nitride or silicon oxygen nitride (SiON) or poly silicon or metal or metal nitride (e.g. W or TiN). A mask material used may be a-C, p-Si, amorphous silicon B-doped a-C, W-doped a-C, B-doped amorphous silicon, or photo resist materials. Herein, the disclosed Si-containing hydrofluorocarbon etching compounds are applied to etch SiO, SiN, p-Si and/or a-C substrate films.
The disclosed etching methods are not limited to above stated experimental conditions in any way and type of plasma etching tool (capacity coupled or inductively coupled plasma), process conditions (pressure, power, temperature, duration of process), process gas mixture, combination and proportion of gases in the gas mixture, gas flow, workpiece or substrate and plasma etching chamber itself may be altered for each process and during the process.
The disclosed also includes etching gas delivery systems.
Here, a programmable logic controller (PLC) (not shown) may installed to the system and is configured for and adapted to control all elements, valves, gas sources, and the like in the apparatus. The etching gas delivery apparatus is specifically adapted to regulate the flow of the first etchant and the second etchant to form the etching gas composition having a predefined ratio of the first etchant and the second etchant based on a chemical formula of the first etchant and the second etchant. The first etchant and the second etchant may or may not be mixed before introducing into an etching processing chamber or a reactor. The first etchant and the second etchant may be mixed in mixing element 806 before introducing into an etching processing chamber or a reactor. The first etchant and the second etchant may be independently introduced into an etching processing chamber or a reactor and mixed therein. The dashed lines 820 and 822 show the first etchant and the second etchant are directly introduced into an etching processing chamber or a reactor without mixing, respectively. In some embodiments, the first etchant is a disclosed Si-containing hydrofluorocarbon and a container of the first etchant may operatively be connected to a device used for semiconductor etching process(es).
In some embodiments, the second enchant may be an inert gas selected from Ar, Kr, Xe, N2, He, Ne or combination thereof, an oxidizer or an oxidizing gas selected from O2, O3, CO, CO2, COS, SO, SO2, FNO, NO, N2O, NO2, H2O, N2O, Cl2, F2, or the like, or an additional gas selected from H2, SF6, NF3, N2, NH3, Cl2, BCl3, BF3, Br2, F2, HBr, HCl or combinations thereof. In addition, the etching gas delivery apparatus shown in
A detailed description of the present disclosure through examples and comparative examples is provided as follows to further illustrate embodiments of the invention. However, the present disclosure is not limited to presented examples in any way, and etching conditions, etching gas mixture, combination and proportion of gases or vapors in the etching gas mixture, substrate and plasma etching chamber itself may vary.
Examples 1-11 and Comparative Examples 1-6 have the following conditions.
Plasma etching device: In the disclosed methods, parallel plate (capacity coupled plasma) plasma generator was used as the plasma etching device. The parallel plate configuration included upper electrode and lower electrode, on which a substrate was placed (lower electrode was used as sample holder with cooling capability). The separation between the electrodes was either 13 or 30 mm. Upper electrode was connecter either to 27 MHz or 60 MHz generator when lower electrode was connected to 2 MHz generator.
Plasma etching condition: During the plasma etching process power supplied to the upper electrode was varied in range from 500 to 2000 W, when power applied to the lower electrode was varied in range from 750 to 7000 W. Pressure was maintained constant during the process in a range between 5 and 100 mTorr. The plasma etching time was set at value between 30 and 300 seconds. Etch rate was estimated in nanometers per minute. Plasma etching gas mixture included Ar, O2, C4F6 and/or C4F8 used as a fluorocarbon gas and C2H6F2Si or CH3F3Si, C4H9F3Si or C5H9F5Si used as a Si-containing hydrofluorocarbon gas and optionally included CH2F2 used as a hydrofluorocarbon gas.
Substrate: The substrates used in Examples 1-11 and Comparative Examples 1-6 were shown in
Plasma etching profile and selectivity: As a criteria for comparison of high aspect ratio etching performance of the disclosed plasma etching process and reference plasma etching processes using a typical etching gas mixture, e.g., a mixture of Ar, O2, C4F6 and/or C4F8, selectivity, top CD, middle CD and bottom CD were chosen, since they are reflecting control of an etched pattern profile. Selectivity has been calculated as the ratio of silicon dioxide etching depth (arrow 8 on
During comparison, higher value of selectivity or infinite selectivity was targeted, when neck CD, top CD, bottom CD, bow CD and middle CD were targeted to be as close as possible to the value of diameter of bottom of opening in the amorphous carbon mask (120 nm, arrow 3 on
Plasma etching was performed in a plasma etching chamber where a power of 750 W was applied to the top electrode at frequency of 27 MHz, a power of 1500 W was applied to the bottom electrode at a frequency of the 2 MHz, a pressure in chamber was maintained at 30 mTorr and a gap between the electrodes was set at 13 mm. An etching gas mixture including following flows of gases was introduced to the plasma etching chamber: 150 sccm of Ar, 12 sccm of C4F8, 12 sccm of O2 and 1.2 sccm of C5H9F5Si. Plasma etching process was carried out for 2 minutes. Resulting structure of a cross-section of the substrate after the plasma etching process is shown on
Plasma etching was performed in the same way as in Example 1, with exception that process gas mixture was replaced by the following: 75 sccm of Ar, 15 sccm of C4F6, 10 sccm of O2 and 0.6 sccm of C5H9F5Si. Resulting structure of a cross-section of the substrate after the etching process is shown on
Plasma etching was performed in a plasma etching device where power of 1000 W was applied to the top electrode at frequency of 60 MHz, power of 7000 W was applied to the bottom electrode at a frequency of the 2 MHz, pressure in chamber was maintained at 20 mTorr and gap between the electrodes was set at 20 mm. Process gas mixture including following flows of gases was introduced to the plasma etching chamber: 150 sccm of Ar, 60 sccm of C4F8, 30 sccm of O2 and 5 sccm of C4H9F3Si. Plasma etching process was carried for 2 minutes. Resulting structure of a cross-section of the substrate after the etching process is shown on
Plasma etching was performed in a plasma etching device where power of 1000 W was applied to the top electrode at frequency of 60 MHz, power of 7000 W was applied to the bottom electrode at a frequency of the 2 MHz, pressure in chamber was maintained at 20 mTorr and gap between the electrodes was set at 20 mm. Process gas mixture including following flows of gases was introduced to the plasma etching chamber: 150 sccm of Ar, 60 sccm of C4F8, 35 sccm of O2 and 5 sccm of C4H9F3Si. Plasma etching process was carried for 5 minutes. Resulting structure of a cross-section of the substrate after the etching process is shown on
Plasma etching was performed in a plasma etching device where power of 1000 W was applied to the top electrode at frequency of 60 MHz, power of 7000 W was applied to the bottom electrode at a frequency of the 2 MHz, pressure in chamber was maintained at 20 mTorr and gap between the electrodes was set at 20 mm. Process gas mixture including following flows of gases was introduced to the plasma etching chamber: 150 sccm of Ar, 60 sccm of C4F8, 30 sccm of O2 and 5 sccm of C4H9F3Si. Plasma etching process was carried for 30 seconds. Etch rate for each studied material is summarized in Table 3.
Plasma etching was performed in the same way as in Example 5, with exception that process gas mixture was replaced by the following: 150 sccm of Ar, 40 sccm of C4F8, 20 sccm of CH2F2, 30 sccm of O2 and 5 sccm of C4H9F3Si. Plasma etching process was carried for 30 seconds. Etch rate for each studied material is summarized in Table 3.
Plasma etching was performed in the same way as in Example 5, with exception that process gas mixture was replaced by the following: 150 sccm of Ar, 30 sccm of C4F8, 30 sccm of CH2F2, 30 sccm of O2 and 5 sccm of C4H9F3Si. Plasma etching process was carried for 30 seconds. Etch rate for each studied material is summarized in Table 3.
Plasma etching was performed in the same way as in Example 1, with exception that C5H9F5Si was not added to the process gas mixture. Resulting structure of a cross-section of the substrate after the etching process is shown on
Plasma etching was performed in the same way as in Example 2, with exception that C5H9F5Si was not added to the process gas mixture. Resulting structure of a cross-section of the substrate after the etching process is shown on
Plasma etching was performed in the same way as in Example 3, with exception that C4H9F3Si was not added to the process gas mixture. Resulting structure of a cross-section of the substrate after the etching process is shown on
Plasma etching was performed in the same way as in Example 3, with exception that 5 sccm flow of C4H9F3Si was replaced by 5 sccm flow of C4F6. Resulting structure of a cross-section of the substrate after the etching is shown on
Plasma etching was performed in the same way as in Example 4, with exception that C4H9F3Si was not added to the process gas mixture. Resulting structure of a cross-section of the substrate after the etching process is shown on
Plasma etching was performed in the same way as in Example 4, with exception that 5 sccm flow of C4H9F3Si was replaced by 5 sccm flow of C4F6. Resulting structure of a cross-section of the substrate after the etching process is shown on
Specifically, in Example 1, where 1.3 sccm of C5H9F5Si was added to the working gas mixture of Ar, O2 and C4F8 selectivity to the mask material was 13, which is much higher comparing to Comparative Example 1 where under the same conditions without C5H9F5Si value of selectivity was 7, which is almost twice lower. In Examples 2 and 3, where 0.6 sccm of C5H9F5Si or 5 sccm of C4H9F3Si was added to the process gas mixture of Ar, O2 and C4F6 or C4F8 respectively. selectivity to the mask material was infinite (thickness of mask increased after the process), when in Comparative Examples 2, 3 and 4 where under the same conditions without Si-containing hydrofluorocarbon, or when Si-containing hydrofluorocarbon was replaced by C4F6, value of selectivity was in range from 5 to 20 and which is significantly lower. Moreover, as it can be observed at scanning electron microscopy cross section images of substrates, in the case of Comparative Example 2 plasma etching target material was not etched due to excessive passivation (
Most crucial comparative criteria which indicating etching profile control capability are top and middle CD, since they both are directly affecting etching profile at higher depth. Bottom CD is important but less crucial criteria, since profile distortions such as tapering at bottom could be fixed by over etching (continue of etching process after reaching desired depth or stop layer), when in comparison expansion or clogging in top CD is irreversible. From Table 2 it may be clearly observed that in case of addition of Si-containing hydrofluorocarbon (C4H9F3Si or C5H9F5Si) to the working gas mixture in examples 1-4, both top and middle CD are closer or identical to initial value of opening in the mask (120 nm, arrow 3 on
As it may be observed from Table 3, in the case when 20 or 30 sccm of CH2F2 was added to the process gas mixture it was possible to etch not only SiO2 selectively to a-C and polycrystalline silicon, but also Si3N4. Specifically, in Example 7 when 30 sccm of CH2F2 was added to the process gas mixture it was possible to etch SiO2 and Si3N4 with comparable etch rate and infinite selectivity to a-C and polycrystalline silicon, which are commonly used as a mask material. Observed results are suggesting that the same process as for high aspect ratio etching of SiO2 demonstrated in Examples 1-4 could be implemented for high aspect ratio etching of Si3N4 or alternating layers of SiO2 and Si3N4 (ONON stack) if CH2F2 will be added to the process gas mixture. Moreover, observed infinite selectivity of etching SiO2 or Si3N4 to metal films tested in Examples 5-7 (Ru, Co, Mo, W) indicates that those metals or another metal films (e.g., Al, Pt, Au) may be used as a stop layer for etching process. It means that if metal thin film (e.g. contact pad, buried power rail) exists under target plasma etching material (e.g., SiO2 or Si3N4) high aspect ratio etching process will stop when etched opening with reach metal film and damage to the metal film will be minimized due to infinite selectivity. Additionally etch rate of metal oxide and metal nitride films (TiO2 and TiN) in Example 7 was considerably smaller comparing to SiO2 and Si3N4 etch rate, meaning that it is possible to achieve soft landing on metal oxide or nitride film as well if etching process is well optimized. This effect may be useful for high aspect ratio contact hole etching or etching of other high aspect ratio structures which will land on metal, metal nitride or oxide film (e.g., 3D NAND channel or DRAM capacitor high aspect ratio etching). From summarizing observations in Examples 1-4 and Comparative Examples 1-6, it may be concluded that addition of Si-containing hydrofluorocarbon, preferably with at least one methyl group attached to Si, and more preferably C4H9F3Si or C5H9F5Si to the process gas mixture allows to improve selectivity and preserve lateral dimensions of the structure during high aspect ratio etching. Additionally, formation of fluorocarbon fragments (such as C2F4 observed in the quadrupole mass spectra) during dissociation of Si-containing hydrofluorocarbon can support plasma etching of the material, as it was observed in Examples 1, 2 and Comparative Examples 1, 2. Moreover, as it was demonstrated in Examples 5-7, addition of CH2F2 to the process gas mixture is effective to improve etching of Si3N4, enabling high aspect ratio etching of Si3N4 film or alternating films of SiO2 and Si3N4 while keeping high selectivity to metals.
Plasma etching was performed in a plasma etching device where power of 1000 W was applied to the top electrode at frequency of 60 MHz, power of 7000 W was applied to the bottom electrode at a frequency of the 2 MHz, pressure in chamber was maintained at 20 mTorr and gap between the electrodes was set at 20 mm. Process gas mixture including following flows of gases was introduced to the plasma etching chamber: 150 sccm of Ar, 60 sccm of C4F8, 30 sccm of O2 and 5 sccm of C2H6F2Si. Plasma etching process was carried for 2 minutes. Resulting structure of a cross-section of the substrate after the etching process is shown on
Plasma etching was performed in the same way as in Example 8, with exception that plasma etching process was carried for 5 minutes. Resulting structure of a cross-section of the substrate after the etching process is shown on
Plasma etching was performed in the same way as in Example 8, with exception that process gas mixture was replaced by the following: 150 sccm of Ar, 60 sccm of C4F8, 30 sccm of O2 and 5 sccm of CH3F3Si. Resulting structure of a cross-section of the substrate after the etching process is shown on
Plasma etching was performed in the same way as in Example 9, with exception that process gas mixture was replaced by the following: 150 sccm of Ar, 60 sccm of C4F8, 30 sccm of O2 and 5 sccm of CH3F3Si. Resulting structure of a cross-section of the substrate after the etching process is shown on
Most crucial comparative criteria which indicating etching profile control capability are top and middle CD, since they both are directly affecting etching profile at higher depth. Bottom CD is important but less crucial criteria, since profile distortions such as tapering at bottom could be fixed by over etching (continue of etching process after reaching desired depth or stop layer), when in comparison expansion or clogging in top CD is irreversible. From Table 2 it may be clearly observed that in case of addition of C2H6F2Si or CH3F3Si to the working gas mixture in examples 8-11, both top and middle CD are closer or identical to initial value of opening in the mask (120 nm, arrow 3 on
Examples 12-18 have the following conditions.
Plasma etching device: In the disclosed methods, parallel plate (capacity coupled plasma) plasma generator was used as the plasma etching device. The parallel plate configuration included upper electrode and lower electrode, on which a substrate was placed (lower electrode was used as sample holder with cooling capability). The separation between the electrodes was either 13 or 20 mm. Upper electrode was connecter either to 27 MHz or 60 MHz generator when lower electrode was connected to 2 MHz generator.
Plasma etching conditions: During the plasma etching process power supplied to the upper electrode was varied in range from 500 to 2000 W, when power applied to the lower electrode was varied in range from 750 to 7000 W. Pressure was maintained constant during the process in a range between 1 and 100 mTorr. The plasma etching time was set at value between 30 and 300 seconds. Etch rate was estimated in nanometers per minute. Plasma etching gas mixture included Ar, O2, C4F8 used as a fluorocarbon gas and C2H6F2Si or CH3F3Si or C4H9F3Si or C5H9F5Si used as a Si-containing hydrofluorocarbon gas
Substrate: referring to
Plasma etching was performed in a plasma etching device where power of 750 W was applied to the top electrode at frequency of 27 MHz, power of 1500 W was applied to the bottom electrode at a frequency of the 2 MHz, pressure in chamber was maintained at 30 mTorr and gap between the electrodes was set at 13 mm. Process gas mixture including following flows of gases was introduced to the plasma etching chamber: 75 sccm of Ar, 7.6 sccm of C5H9F5Si and flow of O2 varied in a range between 0 and 20 sccm. Plasma etching process was carried out for 1 minute.
Plasma etching was performed in the same way as in Example 12, with exception that process gas mixture was replaced by the following: 125 sccm of Ar, 9 sccm of C4F6, 14 sccm of O2 and flow of C5H9F5Si varying in the range between 0 and 2.5 sccm.
Plasma etching was performed in a plasma etching device where power of 1000 W was applied to the top electrode at frequency of 60 MHz, power of 7000 W was applied to the bottom electrode at a frequency of the 2 MHz; power for both top and bottom electrode was pulsed at frequency of 500 Hz and duty cycle 60%. Pressure in chamber was maintained at 20 mTorr and gap between the electrodes was set at 20 mm. Process gas mixture including following flows of gases was introduced to the plasma etching chamber: 150 sccm of Ar, 40 sccm of O2, 65 sccm of C4F8 and flow of C4H9F3Si varying in the range between 0 and 10 sccm. Plasma etching process was carried out for 30 seconds.
Plasma etching was performed in the same way as in Example 14, with exception that process gas mixture was replaced by the following: 150 sccm of Ar, 30 sccm of O2, 5 sccm of C4H9F3Si and flows of C4F8 and CH2F2 varying in the range between 0 and 60 sccm, while keeping total flow of both C4F8 and CH2F2 at 60 sccm.
Plasma etching was performed in the same way as in Example 14, with exception that process gas mixture was replaced by the following: 150 sccm of Ar, 30 sccm of O2, 60 sccm of CH2F2 and flow of C4H9F3Si varying in the range between 0 and 25 sccm.
As it could be observed from Table 5, etch rate varies in a wide range depending on chosen gas mixture and type of material used as etching target. There are few combinations of gas flows where particular material could be etched exclusively with infinite selectivity to other tested materials. For instance in Example 12 and 14 it was possible to etch SiO2 with infinite selectivity to all other tested materials when conditions listed in Table 5 were used for the etching process. Moreover, it could be clearly observed from
In the Example 14, C4F8 was used as a main etchant, which is effective for SiO2 etching, when C4H9F3Si was added to the gas mixture to promote polymer deposition and increase of selectivity to other than SiO2 materials. The same approach may be used for selective etching of other materials if another main etchant is used. In Example 16 CH2F2 was used as a main etchant, which is effective for Si3N4 etching. As a result it was possible to suppress etching of materials other than Si3N4 by addition of C4H9F3Si to the gas mixture and promotion of polymer deposition while keeping reasonable etch rate of Si3N4. Moreover, at flow rates of C4H9F3Si above 10 sccm etch rate of Si3N4 was even promoted due to presence of trifluoromethyl group in the C4H9F3Si molecule, which can supply fluorocarbon to the process and promote etching of Si3N4, when polymer will be deposited on another materials. In the case of condition highlighted in Table 5 for Example 16, when 25 sccm of C4H9F3Si was added to the process gas mixture it was possible to achieve infinite selectivity to a-C, poly-Si, W, SiO2, SiC, SiCN, SiON; when at lower flow rates of C4H9F3Si or when C4H93Si was not added to the process gas mixture (condition with 0 sccm on
In addition, there were several conditions where it was possible to etch combination of materials with infinite selectivity to other tested materials. For instance, in Example 15 it was possible to etch both Si3N4 and SiO2 with infinite selectivity to a-C, poly-Si, W, SiC, SiCN, SiON. In some cases it is necessary to etch multiple materials simultaneously with high selectively to rest of substrate, and demonstrated in the present disclosure selective etching using Si-containing hydrofluorocarbon mixed with common gases (e.g. mixture including either inert gas, fluorocarbon, hydrofluorocarbon, oxidizing gas or combinations of thereof) may be essential for this purpose.
In particular, for the application of multicolor etching typically several Si-containing films are presented on the substrate and exposed during the etching process. Commonly used Si-containing films are SiO2, Si3N4, SiC, SiCN and SiON; therefore, demonstrated etching of SiO2, Si3N4 or both of those materials with high or infinite selectivity to another Si-containing materials achieved by addition of Si-containing hydrofluorocarbon to the process gas mixture will be essential for advanced patterning of a substrate using multicolor etching.
Plasma etching was performed in a plasma etching device where power of 1000 W was applied to the top electrode at frequency of 60 MHz, power of 7000 W was applied to the bottom electrode at a frequency of the 2 MHz; power for both top and bottom electrode was pulsed at frequency of 500 Hz and duty cycle 60%. Pressure in chamber was maintained at 20 mTorr and gap between the electrodes was set at 20 mm. Process gas mixture including following flows of gases was introduced to the plasma etching chamber: 150 sccm of Ar, 30 sccm of O2, 60 sccm of C4F8 and flow of C2H6F2Si varying in the range between 0 and 10 sccm. Plasma etching process was carried out for 30 seconds.
Plasma etching was performed in the same way as in Example 17, with exception that process gas mixture was replaced by the following: 150 sccm of Ar, 30 sccm of O2, 60 sccm of C4F8 and flow of CH3F3Si varying in the range between 0 and 13 sccm.
As it could be observed from Table 6, etch rate varies in a wide range depending on chosen gas mixture and type of material used as etching target. There are few combinations of gas flows where particular material could be etched with high selectivity or even exclusively with infinite selectivity to other tested materials. For instance in Example 17 and 18 it was possible to etch SiO2 with high or infinite selectivity to all other tested materials when conditions listed in Table 6 were used for the etching process. Moreover, it could be clearly observed from
Examples 19-22 and Comparative Example 7 have the following conditions.
Plasma etching device: In the disclosed methods, parallel plate (capacity coupled plasma) plasma generator was used as the plasma etching device. The parallel plate configuration included upper electrode and lower electrode, on which substrate was placed (lower electrode was used as sample holder with cooling capability). The separation between the electrodes was either 13 or 20 mm. Upper electrode was connected either to 27 MHz or 60 MHz power generator when lower electrode was connected to 2 MHz power generator.
Plasma etching conditions: During the plasma etching process power supplied to the upper electrode was varied in range from 500 to 1000 W, when power applied to the lower electrode was varied in range from 750 to 7000 W; power applied to both top and bottom electrodes may be pulsed at lower frequency (e.g. 1-1000 Hz) and duty cycle in range from 10-99%. Pressure has been maintained constant during the process at values selected in range between 5 and 100 mTorr. The plasma etching time was set at value between 30 and 60 seconds. Plasma process gas mixture included Ar, O2 and CH3F3Si or C2H6F2Si or C4H9F3Si as Si-containing hydrofluorocarbon gas.
Substrate: referring to
Initial thickness of each target plasma etching material was as follows: 300 nm of a-C, 110 nm of W, 550 nm of poly-Si, 300 nm of Si3N4, 2000 nm of SiO2.
Plasma etch rate and selectivity: Plasma etch rate was estimated as a difference between initial thickness of plasma etching target material film and thickness of the film after etching process divided by duration of etching process in minutes, to receive etch rate in nm/min. Selectivity was estimated as ratio of etch rate calculated for two different plasma etching materials. Term “infinite selectivity” refers to the case where material is removed from the substrate while non-etching material remains intact or thin film is deposited on top of non-etching material during etching process.
Plasma etching was performed in a plasma etching device where power of 750 W was applied to the top electrode at frequency of 27 MHz, power of 1500 W was applied to the bottom electrode at a frequency of the 2 MHz, pressure in chamber was maintained at 30 mTorr and gap between the electrodes was set at 13 mm. Process gas mixture including following flows of gases was introduced to the plasma etching chamber: 75 sccm of Ar, 7.6 sccm of C4H9F4Si and flow of O2 varied in a range between 0 and 20 sccm. Plasma etching process was carried out for 1 minute.
Plasma etching was performed in a plasma etching device where power of 700 W was applied to the top electrode at frequency of 60 MHz, power of 7000 W was applied to the bottom electrode at a frequency of the 2 MHz; power applied to both top and bottom electrode was pulsed at 500 Hz with duty cycle of 60%. Pressure in chamber was maintained at 25 mTorr and gap between the electrodes was set at 30 mm. Process gas mixture including following flows of gases was introduced to the plasma etching chamber: 150 sccm of Ar, 20 sccm of C4H9F3Si and flow of O2 varied in a range between 5 and 90 sccm. Plasma etching process was carried out for 30 seconds.
Plasma etching was performed in the same way as in Example 20, with exception that 15 sccm flow of C4H9F3Si in process gas mixture was replaced with 15 sccm flow of C4F6.
As it could be observed from Table 7 and
Furthermore, it was possible to etch W doped a-C in Example 20 when O2 flowrate was above 45 sccm which can be essential for high aspect ratio etching applications (such as ONON channel etching or staircase contact etching in 3D NAND) where robust mask is required due to long time of process resulting in use of doped a-C as a hard mask. Observed infinite selectivity to other tested materials will ensure that films covered by mask (such as Si3N4 or SiO2) will not be damaged during patterning of mask itself.
Another possible application is selective mask removal using studied in the present disclosure gas mixture. Use of Si-containing hydrofluorocarbon in a process gas mixture will allow selective removal of a-C mask from the substrate while not damaging another materials. On the other hand, as it may be observed in Comparative Example 19 that it is possible to etch a-C and W doped a-C when C4H9F3Si is not added to the process gas mixture and the same flow of C4F6 added instead. However, selectivity to other tested materials is dramatically decreased in case of use of C4F6, even though C4F6 is commonly used gas for enhancement of polymerization to preserve hard mask or sidewalls during high aspect ratio etching process. Poor selectivity of a-C and doped a-C etching will limit process window for the mask patterning or removal and may make practical use of the process impossible for certain applications.
Therefore, it may be concluded that addition of Si-containing hydrofluorocarbon gas to the process gas mixture allows significant increase of selectivity to non-etching material by deposition of robust polymer, while keeping reasonable etching speed of the target organic film, comparable to common Ar+O2+C4F6 gas mixture. Benefits of use of Si-containing hydrofluorocarbon are expected to be the same when compared to the use of an Ar+O2 gas mixture to selectively etch organic films.
Plasma etching was performed in a plasma etching device where power of 700 W was applied to the top electrode at frequency of 60 MHz, power of 7000 W was applied to the bottom electrode at a frequency of the 2 MHz; power applied to both top and bottom electrode was pulsed at 500 Hz with duty cycle of 60%. Pressure in chamber was maintained at 25 mTorr and gap between the electrodes was set at 20 mm. Process gas mixture including following flows of gases was introduced to the plasma etching chamber: 150 sccm of Ar, 20 sccm of C2H6F2Si and flow of O2 varied in a range between 0 and 90 sccm. Plasma etching process was carried out for 30 seconds.
Plasma etching was performed in the same way as in Example 21, with exception that process gas mixture was replaced by the following: 150 sccm of Ar, 25 sccm of CH3F3Si and flow of O2 varied in a range between 0 and 90 sccm.
As it could be observed from Table 8 and
Examples 23 to 32 regarding cyclic plasma dry etching methods have the following conditions.
Plasma etching device: In the disclosed methods, parallel plate (capacity coupled plasma) plasma generator was used as the plasma etching device. The parallel plate configuration included upper electrode and lower electrode; on which substrate was placed (lower electrode was used as sample holder with cooling capability). The separation between the electrodes was either 13 or 20 mm. Upper electrode was connecter either to 27 MHz or 60 MHz generator when lower electrode was connected to 2 MHz generator.
Plasma etching condition: During the plasma etching process power supplied to the upper electrode was varied in range from 500 to 2000 W, when power applied to the lower electrode was varied in range from 750 to 7000 W. Power applied to the top and the bottom electrode may be both pulsed at lower frequency (e.g. 1-1000 Hz) with duty cycle in range 199%. Pressure has been maintained constant during the process at values selected in range between 5 and 100 mTorr. The plasma etching time was set at value between 10 and 60 seconds. Deposition rate has been estimated in nanometers per minute. Negative deposition rate represents condition when material on the substrate was etched. Plasma process gas mixture included at least one of the following gases: Ar, O2, C4F6 and/or C4F8 as a fluorocarbon gas, C4H9F3Si or C5H9F5Si as Si-containing hydrofluorocarbon gas, CH2F2 as hydrofluorocarbon gas.
Substrate: referring to
Plasma etch rate and selectivity: Plasma deposition or etch rate was estimated as a difference between initial thickness of plasma etching target material film and thickness of the film after etching process divided by time, to receive etching or deposition rate in nm/min. Negative deposition rate in some of examples represents etching of the sample (in fact equivalent to etch rate value).
Cyclic etching process: The disclosed cyclic etching process refers to the process when the substrate is processed in an etching chamber using several etching steps which are repeated in a sequence. Example of substrate processed using cyclic etching shown in
The substrate after the first step of the etching cycle is presented on
Plasma etching condition: Plasma etching was performed in a plasma etching device where power of 750 W was applied to the top electrode at frequency of 27 MHz, power of 1500 W was applied to the bottom electrode at a frequency of the 2 MHz, pressure in chamber was maintained at 30 mTorr and gap between the electrodes was set at 13 mm. Process gas mixture including following flows of gases was introduced to the plasma etching chamber: 75 sccm of Ar, 7.6 sccm of C5H9F5Si and flow of O2 varied in a range between 0 and 20 sccm. Plasma etching process was carried out for 1 minute.
Plasma etching was performed in the same way as in Example 23, with exception that process gas mixture was replaced by the following: 75 sccm of Ar, 9 sccm of C4F6, 14 sccm of O2 and flow of C5H9F5Si varying in the range between 0 and 2.5 sccm.
Plasma etching was performed in the same way as in Example 23, with exception that process gas mixture was replaced by the following: 125 sccm of Ar, 9 sccm of C4F8, 14 sccm of O2 and flow of C5H9F5Si varying in the range between 0 and 2.5 sccm.
Plasma etching condition: Plasma etching was performed in a plasma etching device where power of 700 W was applied to the top electrode at frequency of 60 MHz, power of 7000 W was applied to the bottom electrode at a frequency of the 2 MHz; power for both top and bottom electrode was pulsed at frequency of 500 Hz and duty cycle 60%. Pressure in chamber was maintained at 20 mTorr and gap between the electrodes was set at 20 mm. Process gas mixture including following flows of gases was introduced to the plasma etching chamber: 150 sccm of Ar, 15 sccm of C4H9F3Si, flow of O2 varying in the range between 0 and 90 sccm. Plasma etching process was carried out for 30 seconds.
Plasma etching was performed in the same way as in Example 26, with exception that power applied to the top electrode was 1000 W and process gas mixture was replaced by the following: 150 sccm of Ar, 40 sccm of O2, 65 sccm of C4F8 and flow of C4H9F3Si varying in the range between 0 and 10 sccm.
Plasma etching was performed in the same way as in Example 26, with exception that power applied to the top electrode was 1000 W and process gas mixture was replaced by the following: 150 sccm of Ar, 30 sccm of O2, 5 sccm of C4H9F3Si and flows of C4F8 and CH2F2 varying in the range between 0 and 60 sccm, while keeping total flow of both C4F8 and CH2F2 at 60 sccm.
Plasma etching was performed in the same way as in Example 26, with exception that power applied to the top electrode was 1000 W and process gas mixture was replaced by the following: 150 sccm of Ar, 30 sccm of O2, 60 sccm of CH2F2 and flow of C4H9F3Si varying in the range between 0 and 25 sccm.
Plasma etching condition: Cyclic plasma etching process was performed in a plasma etching device where power of 1000 W was applied to the top electrode at frequency of 60 MHz, power of 7000 W was applied to the bottom electrode at a frequency of the 2 MHz; power for both top and bottom electrode was pulsed at frequency of 500 Hz and duty cycle 60%. Pressure in chamber was maintained at 20 mTorr and gap between the electrodes was set at 20 mm.
Each cycle contained two etching steps. First, step selective etching of Si3N4 (with deposition of polymer on materials other than Si3N4) and second step aggressive etching of Si3N4 with low selectivity (which is etching polymer deposited during 1st step and materials other than Si3N4).
During the first etching cycle, the first step was performed using process gas mixture supplied to the chamber including following flows of gases: 150 sccm of Ar, 25 sccm of C4H9F3Si, 60 sccm of CH2F2 and 30 sccm of O2. Plasma etching process during first step was carried out for 17 seconds. Second step was performed using process gas mixture supplied to the chamber including following flows of gases: 150 sccm of Ar, 15 sccm of C4F8, 45 sccm of CH2F2 and 30 sccm of O2. Plasma etching process during second step was carried out for 10 s.
Second and following cycles were using the same gas mixtures for the first and second step inside each cycle as during the first cycle, however duration of each step was altered. Duration of first step with selective etching was set to 10 s and duration of second with not selective etching was set to 40 s for second and following etching cycles.
Plasma etching condition: Cyclic plasma etching process was performed in a plasma etching device where power of 700 W was applied to the top electrode at frequency of 60 MHz, power of 7000 W was applied to the bottom electrode at a frequency of the 2 MHz; power for both top and bottom electrode was pulsed at frequency of 500 Hz and duty cycle 60%. Pressure in chamber was maintained at 25 mTorr and gap between the electrodes was set at 20 mm.
Each cycle contained two etching steps. First step selective etching of Pt (with deposition of polymer on materials other than Pt) and second step etching of Pt with low selectivity (which is etching polymer deposited during 1st step and materials other than Pt).
The first step was performed using process gas mixture supplied to the chamber including following flows of gases: 150 sccm of Ar, 15 sccm of C4H9F3Si, and 15 sccm of O2. Plasma etching process during first step was carried out for 60 seconds. Second step was performed using process gas mixture supplied to the chamber including following flows of gases: 150 sccm of Ar, 65 sccm of C4F8 and 30 sccm of O2. Plasma etching process during second step was carried out for 9 s. Estimated etch rate for each material per etching cycle is summarized in Table 9.
Plasma etching condition: Plasma etching was performed in a plasma etching device where power of 700 W was applied to the top electrode at frequency of 60 MHz, power of 7000 W was applied to the bottom electrode at a frequency of the 2 MHz; power for both top and bottom electrode was pulsed at frequency of 500 Hz and duty cycle 60%. Pressure in chamber was maintained at 25 mTorr and gap between the electrodes was set at 20 mm. Process gas mixture including following flows of gases was introduced to the plasma etching chamber: 150 sccm of Ar, 15 sccm of C4H9F3Si, 15 sccm of O2. Plasma etching process was carried out for 30 seconds. Estimated etch rate for each material per etching cycle is summarized in Table 9. Negative etch rate corresponds to the case when polymer was deposited on the studied material and reflects deposition rate.
Based on assumption that amount of removed etching target material or deposited polymer scales linearly with the process time it was estimated that it will be necessary to run process described in the present example for around 54 s to remove same amount of Pt as it was reported for one cycle of etching in Example 31.
As it could be observed from Examples 23 to 32 in
In Example 30, cyclic etching process was developed using condition with infinite selectivity etching of Si3N4 from Example 29 for the first step inside etching cycles. As it could be observed from
From a comparison of
Presence of thick polymer after continuous selective etching will require use of cleaning recipe after the etching process to remove polymer, which may damage exposed target material, mask and structure further limiting use of the selective etching process in fabrication of novel semiconductor devices. On the other hand, in the case of presently disclosed cyclic etching process only thin film of polymer or thin modified layer on surface of non-etching material will be present after etching process, which may be easily removed by sort cleaning, minimizing possible damage and reducing processing time. Additionally, soft cleaning steps or another etching steps may be included inside each cycle or some defined cycles to further tune cyclic etching process and eliminate presence of polymer or modified layer on surface of non-etching material and keeping non-etching material film close to initial condition after cyclic etching.
On the other hand, different rate of deposition of polymer on the surface of various materials observed in examples 1-7 may be used for development of cyclic etching recipe using steps within each cycle including deposition of polymer and etching. For instance in
Results demonstrated in the present disclosure show that reach polymer deposition with variable rate depending on the target material and etching of particular materials with infinite selectivity which is possible when Si-containing hydrofluorocarbon is added to the process gas mixture (Examples 23 to 32) looks promising for development of cyclic etching processes. It was further demonstrated, that it is possible to inhibit polymer deposition using cyclic process and keep condition of the non-etching material close to initial, when in the case of continuous process with infinite selectivity thick polymer film will deposit, requiring further processing or additional cleaning. Developed cyclic etching process using Si-containing hydrofluorocarbon in at least one of the cycle step looks promising for advanced patterning of substrate during fabrication of semiconductor device. In particular for the application of multiple patterning, multicolor etching or low-contrast etching, when typically several Si-containing films are presented on the substrate and exposed during the etching process. Commonly used Si-containing films in those processes are SiO2, Si3N4, SiC, SiCN and SiON; therefore, demonstrated capability of selective etching of SiO2, Si3N4 or both of those materials achieved by cyclic etching process with addition of Si-containing hydrofluorocarbon to the process gas mixture in at least one of cycle steps will be essential for advanced patterning of a substrate using multicolor etching. Additionally, demonstrated capability of selective etching or deposition of thinner polymer film on organic material (e.g., a-C) looks promising for organic mask patterning or removal because it will provide high selectivity to materials other than the processed mask and will not lead to deposition of thick film on those materials.
Although the subject matter described herein may be described in the context of illustrative implementations to process one or more computing application features/operations for a computing application having user-interactive components the subject matter is not limited to these particular embodiments. Rather, the techniques described herein can be applied to any suitable type of user-interactive component execution management methods, systems, platforms, and/or apparatus.
It will be understood that many additional changes in the details, materials, steps, and arrangement of parts, which have been herein described and illustrated in order to explain the nature of the invention, may be made by those skilled in the art within the principle and scope of the invention as expressed in the appended claims. Thus, the present invention is not intended to be limited to the specific embodiments in the examples given above and/or the attached drawings.
This application claims the benefit of the filing date of U.S. provisional application No. 63/256,698, filed on Oct. 18, 2021, the teachings of which are incorporated herein by reference.
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/US2022/046985 | 10/18/2022 | WO |
| Number | Date | Country | |
|---|---|---|---|
| 63256698 | Oct 2021 | US |
