Patent Application
20240128090
The present invention relates generally to a method for fabricating a layer structure constituted by a dielectric layer in a step formed on a substrate.
For etching of films such as those constituted by metal-oxides, nitrides, or carbides, plasma etching is often used because etch rates are typically high (10-100 nm/s), and the etching is typically anisotropic due to the presence of ions. The presence of ions results in a relatively poor etch-selectivity between materials. On the other hand, wet etching is typically isotropic and often enables etch selectivity to increase but reduces wafer-to-wafer reproducibility and/or uniformity, as well as throughput. Also, wet etching produces a large amount of chemical waste and thus is often associated with safety and environmental concerns, raising an issue.
To achieve uniform etching with enough etch selectivity, radicals-based etching may effectively be used. This can bring about combined benefits of dry etching with good selectivity and wet etching with isotropic property. For their actual applications, however, a specific patterning scheme and a specific etch selectivity will need to be further investigated when using different materials for adjacent layers to produce a desired structure with a specific topology profile. Although radical etch technology is known in the art such as those disclosed in U.S. Pat. Nos. 9,064,815 and 9,275,834, further improvement will be required particularly for forming a film with a desired topology profile.
In particular, selective-etching of SiN films using wet-etch chemicals has been widely used in manufacturing semiconductor devices. For example, SiN films are selectively etched by hot (>100° C.) phosphoric acid solution with water in a structure of SiN/SiO2 stacking layers for, e.g., making memory cells of 3D-NAND devices. However, the etch rate varies depending on several parameters such as chemical concentration, temperature, and duration of dipping. Further, precise control over the etch rate on the nanometer order is difficult and the process throughput is relatively low since a drying process is required after a wet-cleaning process. Moreover, the wet-etch chemical waste is sometimes harmful to our health, requiring special solid wet-cleaning baths for safety and environmental concerns.
On the other hand, dry etching using either a SF6 or NF3 plasma is known and typically used for a side-remaining topology profile of SiN film coating. Due to the presence of ions, dry etching is typically directional, which increases the etch rate of surfaces exposed to ions (typically horizontal surfaces). The presence of ions often makes it difficult to achieve conformal etching or top-remaining etching. For this reason, wet etching is typically used more often in some cases than is dry etching. See US 20170345674A1 (Dry Etching with NF3/O2), US 20180204733A1 (Dry Etching with SF6), and US 20120289056A1 (Wet Etching with Phosphoric Acid).
Wet etching can typically be performed in a manner disclosed in U.S. Pat. No. 9,754,779B1 wherein a SiN film is deposited on a patterned surface under controlled conditions, followed by subjecting it to wet etching using dHF solution, thereby providing either a sidewall-remaining topology profile or top/bottom-remaining topology profile in the SiN film. This technology utilizes the wet-etching characteristics of the SiN film against chemicals, wherein chemical resistance of the SiN film differs between its horizontal surface portion and its vertical surface portion. However, in order to leave a portion of the SiN film on sidewalls of the patterned structure or a portion of the SiN film on top/bottom of surfaces of the patterned structure in the disclosed methods, the deposition process and the wet-etching process, which are by nature different processes, must be performed in different treatment chambers, respectively, resulting in high cost, low throughput, large footprint, and other concerns.
It should be noted that as discussed above, any discussion of problems and solutions in relation to the related art has been included in this disclosure solely for the purposes of providing a context for the present invention, and should not be taken as an admission that any or all of the discussion was known at the time the invention was made or this application is filed.
In view of the foregoing, some embodiments provide a method for fabricating a layer structure having a target topology profile in a step which has a side face and a lateral face, comprising processes of: (a) depositing a dielectric layer on a preselected area of the substrate under first deposition conditions, wherein the dielectric layer has a portion whose resistance to fluorine and/or chlorine radicals under first dry-etching conditions is tuned; and (b) exposing the dielectric layer obtained in process (a) to the fluorine and/or chlorine radicals under the first dry-etching conditions, thereby removing at least a part of the portion of the dielectric layer, thereby forming a layer structure having the target topology profile on the substrate. The target topology profile may typically be a side face-remaining topology profile, a lateral face-remaining topology profile, or a conformal topology profile.
In some embodiments, the method further comprises processes of, prior to process (a): (i) providing reference deposition conditions and reference dry-etching conditions under which a layer structure having a reference topology profile is formed in the step on the substrate by conducting process (a) and process (b); (ii) upon comparing the thus-obtained reference topology profile with the target topology profile, changing at least one parameter of the reference deposition conditions and/or at least one parameter of the reference dry-etching conditions in a manner forming a layer structure having a topology profile in the step on the substrate, which is more similar to the target topology profile than is the reference topology profile; (iii) conducting process (a) and process (b) under the changed deposition/dry-etching conditions; and optionally (iv) repeating processes (ii) and (iii) until the thus-obtained topology profile is substantially equivalent to the target topology profile. Conducting processes (i) to (iv) is preferable and allows efficiently determining the first deposition conditions and the first dry-etching conditions for suitably tuning chemical resistance of the second dielectric layer with reference to that of the first dielectric layer. However, conducting processes (i) and (iv) is not specifically essential to conducting processes (a) and (b), since the principal of “etch selectivity” is known in the art (e.g., etch selectivity of films in wet etching), and a skilled artisan in the art can determine conditions and/structures necessary for conducting processes (a) and (b) in view of the present disclosure, especially with the guidance disclosed herein, as a matter of routine experimentation, without undue burden.
Among various embodiments, a first exemplary embodiment involves a method wherein the dielectric layer is constituted by a first dielectric layer deposited on the substrate and a second dielectric layer deposited on and in contact with the first dielectric layer, wherein the second dielectric layer has a turned resistance to fluorine and/or chlorine radicals in a manner that an etch selectivity of the second dielectric layer over the first dielectric layer is at least 5 (e.g., at least 10, 50, 100, 500, or 1,000) wherein the etch selectivity is defined as a ratio of etch rate of the second dielectric layer to etch rate of the first dielectric layer under the first dry-etching conditions.
In some embodiments of the method, the first dielectric layer is constituted by an oxide film, and the second dielectric layer is constituted by silicon nitride film. In some embodiments of the method, the first dielectric layer and the second dielectric layer are of a same type wherein primary chemical bonds constituting the first and second dielectric layers are the same.
A second exemplary embodiment involves a method wherein a first portion of the dielectric layer deposited on the side face and a second portion of the dielectric layer deposited on the lateral face have different resistances to fluorine and/or chlorine radicals under the first dry-etching conditions in a manner that an etch selectivity of one of the first and second portions, whichever has a lower etch rate than that of another of the first and second portions under the first dry-etching conditions, is at least 1.5 (e.g., at least 1.7, 2.0, 2.5, or 3.0), wherein the etch selectivity of the one of the first and second portions is defined as a ratio of etch rate of the one of the first and second portions to etch rate of another of the first and second portions under the first dry-etching conditions. In the first exemplary embodiment, the dielectric layer is constituted by the first and second dielectric layers which are laminated and have different dry etch selectivity, whereas in the second exemplary embodiment, the dielectric layer is constituted by the first portion (side portion) and the second portion (lateral portion) which have different dry etch selectivity. However, these embodiments can be practiced in any combination.
A third exemplary embodiment involves a method wherein a portion of the dielectric layer deposited on the side face and a portion of the dielectric layer deposited on the lateral face have different thicknesses. Although the first and second exemplary embodiments utilize the difference in etch selectivity to achieve the target topology profile of the final layer structure, the third exemplary embodiment can achieve the target topology profile of the final layer structure without requiring the difference in etch selectivity. However, the third exemplary embodiment can be practiced in any combination with the first and/or second exemplary embodiment(s).
A fourth exemplary embodiment involves a method wherein process (a) and process (b) are conducted in a same chamber. In some embodiments of the method, the fluorine and/or chlorine radicals are fluorine radicals generated remotely or within the same chamber, from a gas containing fluorine and nitrogen and a noble gas. This exemplary embodiment can be conducted in combination with any one or more of the disclosed embodiments.
For purposes of summarizing aspects of the invention and the advantages achieved over the related art, certain objects and advantages of the invention are described in this disclosure. Of course, it is to be understood that not necessarily all such objects or advantages may be achieved in accordance with any particular embodiment of the invention. Thus, for example, those skilled in the art will recognize that the invention may be embodied or carried out in a manner that achieves or optimizes one advantage or group of advantages as taught herein without necessarily achieving other objects or advantages as may be taught or suggested herein.
Further aspects, features and advantages of this invention will become apparent from the detailed description which follows.
These and other features of this invention will now be described with reference to the drawings of preferred embodiments which are intended to illustrate and not to limit the invention. The drawings are greatly simplified for illustrative purposes and are not necessarily to scale.
The patent or application file contains at least one drawing executed in color. Copies of this patent or patent application publication with color drawing(s) will be provided by the Office upon request and payment of necessary fee.
In this disclosure, a SiN is a film characterized or recognized as a silicon nitride film which may include other elements such as oxygen, carbon, hydrogen, etc. and unavoidable impurities to the extent that such elements do not materially change the characteristics of the silicon nitride film, wherein a SiN film includes not only SiN films, but also SiNC films, SiNO films, SiNCO films, or the like, depending on the process recipe, wherein these film names are commonly accepted abbreviations in the art, indicating merely the film types (indicating simply by primary constituent elements), in a non-stoichiometric manner unless described otherwise. In some embodiments, a SiN has a dielectric constant of about 2 to 10, typically about 4 to 8. Similarly, a SiO film is a film characterized or recognized as a silicon oxide film which may include other elements such as nitrogen, carbon, hydrogen, etc. and unavoidable impurities to the extent that such elements do not materially change the characteristics of the silicon oxide film, wherein a SiO film includes not only SiO films, but also SiOC films, SiON films, SiOCN films, or the like.
In this disclosure, a “step” refers to any structure having a top surface, a sidewall, and a bottom surface formed on a substrate, which may continuously be arranged in series in a height direction or may be a single step, and which may constitute a trench, a via hole, or other recesses.
In some embodiments, the trench has a width of 10 to 50 nm (typically 15 to 30 nm) (wherein when the trench has a length substantially the same as the width, it is referred to as a hole/via, and a diameter thereof is 10 to 50 nm), a depth of 30 to 200 nm (typically 50 to 150 nm), and an aspect ratio of 3 to 20 (typically 3 to 10).
In this disclosure, “gas” may include vaporized solid and/or liquid and may be constituted by a single gas or a mixture of gases. In this disclosure, a process gas introduced to a reaction chamber through a showerhead may be comprised of, consist essentially of, or consist of a precursor gas and an additive gas. The precursor gas and the additive gas are typically introduced as a mixed gas or separately to a reaction space. The precursor gas can be introduced with a carrier gas such as a noble gas. The additive gas may be comprised of, consist essentially of, or consist of a reactant gas and a dilution gas such as a noble gas. The reactant gas and the dilution gas may be introduced as a mixed gas or separately to the reaction space. A precursor may be comprised of two or more precursors, and a reactant gas may be comprised of two or more reactant gases. The precursor is a gas chemisorbed on a substrate and typically containing a metalloid or metal element which constitutes a main structure of a matrix of a dielectric film, and the reactant gas for deposition is a gas reacting with the precursor chemisorbed on a substrate when the gas is excited to fix an atomic layer or monolayer on the substrate. “Chemisorption” refers to chemical saturation adsorption. A gas other than the process gas, i.e., a gas introduced without passing through the showerhead, may be used for, e.g., sealing the reaction space, which includes a seal gas such as a noble gas. In some embodiments, “film” refers to a layer continuously extending in a direction perpendicular to a thickness direction substantially without pinholes to cover an entire target or concerned surface, or simply a layer covering a target or concerned surface. In some embodiments, “layer” refers to a structure having a certain thickness formed on a surface or a synonym of film or a non-film structure. A film or layer may be constituted by a discrete single film or layer having certain characteristics or multiple films or layers, and a boundary between adjacent films or layers may or may not be clear and may be established based on physical, chemical, and/or any other characteristics, formation processes or sequence, and/or functions or purposes of the adjacent films or layers.
In this disclosure, “annealing” refers to a process during which a material is treated to get into its stable form, e.g., a terminal group (such as an alcohol group and hydroxyl group) present in a component is replaced with a more stable group (such as a Si—Me group) and/or forms a more stable form (such as a Si—O bond), typically causing densification of a film.
Further, in this disclosure, the article “a” or “an” refers to a species or a genus including multiple species unless specified otherwise. The terms “constituted by” and “having” refer independently to “typically or broadly comprising”, “comprising”, “consisting essentially of”, or “consisting of” in some embodiments. Also, in this disclosure, any defined meanings do not necessarily exclude ordinary and customary meanings in some embodiments.
Additionally, in this disclosure, any two numbers of a variable can constitute a workable range of the variable as the workable range can be determined based on routine work, and any ranges indicated may include or exclude the endpoints. Additionally, any values of variables indicated (regardless of whether they are indicated with “about” or not) may refer to precise values or approximate values and include equivalents, and may refer to average, median, representative, majority, etc. in some embodiments.
In the present disclosure where conditions and/or structures are not specified, the skilled artisan in the art can readily provide such conditions and/or structures, in view of the present disclosure, as a matter of routine experimentation. In all of the disclosed embodiments, any element used in an embodiment can be replaced with any elements equivalent thereto, including those explicitly, necessarily, or inherently disclosed herein, for the intended purposes. Further, the present invention can equally be applied to apparatuses and methods.
The embodiments will be explained with respect to preferred embodiments. However, the present invention is not limited to the preferred embodiments.
Some embodiments involve dry-etching of different metal-containing materials for performing conformal etching, or for creating top- or side-remaining structures, by using fluorine radicals. A difference in etch selectivity between different metal compounds manifests and varies depending on the substrate temperature and the volatility of their resultant reaction products. Etch selectivity can therefore be tuned by the substrate temperature and appropriate choice of the reaction chemistry. In this disclosure, the term “metal” may include a metalloid element such as silicon depending on the context. Also, in this disclosure, the term “material” in the above context refers to elements, constituents, or substance of which a film is composed, wherein different materials may include materials which are elementally different, materials which are elementally the same but compositionally different, and materials which are elementally and compositionally the same but have different physical and/or chemical properties.
Top- and/or side-remaining structures can be created by (1) changing the deposition conditions of the material next subjected to dry etching. In some embodiments, the etch rates which can be achieved are in a range of 0.1-1 nm/s, allowing good control for the etching while maintaining good throughput. (2) Changing the dry etch conditions may also be conducted in combination with (1) or as an alternative to (1). The proposed dry-etching process flow can also make it possible to perform both deposition and etching in a same chamber or in a same cluster tool (with multiple chambers) to create a side- or top/bottom-remaining patterned film. This can increase throughput and avoid the problem associated with surface contamination as a result of exposure to the air.
Since the etch-selectivity varies depending on the deposited material properties, the selectivity also is expected to be a proxy for wet-etching, despite the fact that the actual selectivity difference between different-metal compounds and/or different-quality materials (including those of an elementally and/or compositionally same type) may differently manifest in the dry-etching process and in the wet-etching process. However, etch rate and wafer-to-wafer uniformity are more easily controllable for the dry-etch process.
Some embodiments involve highly selective dry-etching of SiN film for performing conformal etching or for creating top- or side-remaining structures by using fluorine radicals. This makes it possible to replace a wet-etching step that is typically used, by a dry-etching step. The dry-etch rate of SiN film is determinable as a function of the density, for example. A difference in dry-etching selectivity between SiN films with different film properties is required to create top-or side-remaining structures, as in wet-etching. Thus, by changing the density of SiN film on vertical surfaces and that on horizontal surfaces, the desired topology profile can be obtained (side- or top/bottom-remaining or a combination thereof). In dry-etching processes including conventionally used processes, oxides (SiO2, TiO2 and ZrO2) also can manifest such high etching selectivity.
Further, the proposed dry-etching process can also make it possible to perform both deposition of SiN and etching in a same chamber or in a same cluster tool with multiple chambers, increasing throughput and avoid the problem associated with surface oxide formation as a result of exposure to the air. Also, etch rate and wafer-to-wafer uniformity can be more easily controllable in a dry etch process than in a wet etch process.
Additionally, some embodiments involve performing a deposition process and a dry-etching process in a single chamber or reactor, thereby resolving at least one of the problems discussed in this disclosure. Typically, such a method comprises: (1) depositing an insulating film on a patterned structure of a substrate by plasma-enhanced chemical vapor deposition (PECVD) or plasma-enhanced atomic layer deposition (PEALD) in a reaction chamber, wherein a portion of the film deposited on a horizontal surface and a portion of the film deposited on a vertical surface have different chemical resistance properties (in this disclosure, the “vertical” and “horizontal”, or any similar words, are used as relative terms and are not intended to be limited to the exact direction of gravity and the exact direction orthogonal thereto, respectively, but they are referred to as any general direction substantially parallel to the direction of anisotropic ion bombardment or the direction of film thickness, and any general direction substantially orthogonal thereto, respectively); and then (2) in the same reaction chamber as in process (1), exposing the film deposited in process (1) to a remote plasma using a remote plasma system and performing isotropic dry etching to remove a part (a portion other than a target film-maintaining portion) of the film, thereby leaving a portion of the film substantially only on sidewalls of the patterned structure or only on top/bottom surfaces of the patterned structure.
In some aspects of the disclosed embodiments, by utilizing differences in etch selectivity between the first and second dielectric layers and by controlling directionality of etching, the target topology profile of the final layer structure can be achieved, whereas in some aspects of the disclosed embodiment, by utilizing differences in in-plane etch selectivity of the dielectric layer, the target topology profile of the final layer structure can be achieved.
In some embodiments, by manipulating process (a) and process (b) as shown in Table 1 below by way of example only, by controlling the directionality of deposition and also the directionality of etching, respectively, the desired target topology profile can be achieved as shown in Table 1. As shown in Table 1, in some embodiments, different operation schemes, or different combinations, in processes (a) and (b) may lead to the same or similar final topology profile type (a side-dominant type, conformal, type or top/bottom-dominant type, although the actual profile may be different), wherein there are multiple ways (combinations) to achieve the same or similar results with regard to a topology profile of the final layer structure. In Table 1, “T”, “B”, and “S” refer to “top”, “bottom”, and “side”, respectively, and “Fig. #” denotes a figure number showing a final layer structure formed using the corresponding scheme. The term “conformal” refers a high conformality such as more than approximately 70% to 130% (e.g., 80% to 120%, 90% to 110%, most typically about 100%) in some embodiments. The term “predominant” refers to a substantial difference which is not conformal or is a material difference for the intended purposes such as a predominance by at least 40%, 50%, 100%, 200%, 500%, 1000%, or any ranges thereof in some embodiments. Also, the term “remaining” refers to the meaning of “predominant” in some embodiments. The term “low quality” refers to lower chemical resistance, e.g., higher dry etch rate, or lower density, relative to reference quality, in some embodiments. In this disclosure, any number which defines a numeric range, for example, is a representative number, average number, randomly selected number, median number, conventionally or commonly defined number, or any number equivalent thereto, depending on the context.
As discussed above, some embodiments provide a method for fabricating a layer structure having a target topology profile in a step which has a side face and a lateral face, comprising processes of: (a) depositing a dielectric layer on a preselected area of the substrate under first deposition conditions, wherein the dielectric layer has a portion whose resistance to fluorine and/or chlorine radicals under first dry-etching conditions is tuned; and (b) exposing the dielectric layer obtained in process (a) to the fluorine and/or chlorine radicals under the first dry-etching conditions, thereby removing at least a part of the portion of the dielectric layer, thereby forming a layer structure having the target topology profile on the substrate. In this disclosure, the chemical “resistance” of film can be evaluated based on etched thickness of the film per unit time under given dry-etching conditions, and “etch selectivity” (which may be referred to also as “etching rate selectivity”) of a first film (or a first portion) relative to a second film (or a second portion) can be evaluated based on a ratio of the chemical resistance of the first film to that of the second film.
In some embodiments, the method further comprises processes of, prior to process (a): (i) providing reference deposition conditions and reference dry-etching conditions under which a layer structure having a reference topology profile is formed in the step on the substrate by conducting process (a) and process (b); (ii) upon comparing the thus-obtained reference topology profile with the target topology profile, changing at least one parameter of the reference deposition conditions and/or at least one parameter of the reference dry-etching conditions in a manner forming a layer structure having a topology profile in the step on the substrate, which is more similar to the target topology profile than is the reference topology profile; (iii) conducting process (a) and process (b) under the changed deposition/dry-etching conditions; and optionally (iv) repeating processes (ii) and (iii) until the thus-obtained topology profile is substantially equivalent to the target topology profile.
In some embodiments, the at least one parameter of the reference deposition conditions changed in process (ii) is at least one of plasma power, gas selection, gas flow rate, pressure, and temperature in a reaction space where process (a) is conducted. In some embodiments, the at least one parameter of the reference dry-etching conditions changed in process (ii) is at least temperature of a reaction space where process (b) is conducted.
The technology disclosed herein is widely applicable in various industries, which includes, but is not limited to, an application wherein the step having the side face and the lateral face is constituted by a trench having sidewalls as the side face, and a bottom face and a top face as the lateral face; an application wherein the step having the side face and the lateral face is a part of 3D NAND structure provided with a horizontal recess having a depth-direction face as the side face, and height-direction lower and upper faces as the lateral face; and an application wherein the step having the side face and the lateral face is a part of staircase having a height face as the side face and a depth face as the lateral face.
As discussed in this disclosure, the technology disclosed herein include various embodiments, and each embodiment can include one or two or more of the following features in any combination. Further, in this disclosure, in all of the explicitly, implicitly, or inherently disclosed features, any one or more of them used in an embodiment can interchangeably (or alternatively) or additionally be used in another embodiment unless stated otherwise or such a replacement or addition is not feasible or causes adverse effect or does not work for its intended purposes.
In an aspect, embodiments include, but are not limited to, at least one of the following features or two or more of the following features in any sensical combinations:
1) A method of selective dry-etching of two different materials (a first material and a second material) in terms of chemical resistance or etch selectivity, which materials are deposited on a patterned surface of a substrate, wherein the dry-etch etching process comprises exposing the patterned surface conformally to fluorine and/or chlorine radicals that are generated from an etching gas.
2) The method of 1) wherein the etch selectivity of the first and that of the second materials are differently adjusted by changing:
3) The method of 2) wherein the material quality is adjusted by varying material deposition parameters including:
4) The method of 1) wherein the first and/or second material are/is constituted by a metal-oxide, metal-nitride, metal-carbide, or a combination thereof (e.g., TiO, ZrO, TiN, MoO, MoC, TiCO, etc.).
5) The method of 1) wherein the first material is constituted by a metal-compound material and the second material is constituted by SiO.
6) The method of 1) wherein the first material is constituted by TiO and the second material is constituted by SiO or SiN.
7) The method of 1) wherein the first material has lower quality than the second material in terms of chemical resistance.
8) The method of 1) wherein the process gas contains F and Ar.
9) The method of 1) wherein the process gas contains F, N, and O.
10) The method of 1) wherein the process gas contains Cl.
11) The method of 1) wherein the radicals are generated using:
12) The method of 1) wherein a reaction chamber for the etching process is clustered with the reaction chamber for the deposition process, and the deposition process and the etching process are sequentially and continuously conducted without breaking a vacuum.
13) The method of 1) wherein the deposition process and the etching process are performed in a same reaction chamber.
In another aspect, embodiments include, but are not limited to, at least one of the following features or two or more of the following features in any sensical combinations:
1) A method of highly-selective dry-etching of SiN film relative to another film constituted by another material, which films are deposited on a patterned surface of a substrate, wherein the dry-etching process comprises exposing the patterned surface conformally to fluorine and/or chlorine radicals that are generated from an etching gas.
2) The method of 1) wherein the other material is SiN which is different from SiN constituting the SiN film in terms of film quality such as the film density and/or film composition, and the etching gas is a fluorine-containing gas such as SF6 or NF3.
3) The method of 1) wherein the highly selective dry-etching is conducted to the SiN film deposited on a step structure of the patterned surface, and a desired portion of the SiN film is selectively removed relative to the remaining portion of the SiN film due to their difference of film quality.
4) The method of 1) wherein the other material is a dielectric material such as SiO2, SiC, SiCO, Ti oxide, Hf oxide, and/or Zr oxide.
5) The method of 1) wherein the etching gas contains F and Ar.
6) The method of 1) wherein the etching gas contains F, N and O.
7) The method of 1) wherein the etching process uses Cl radicals, rather than F radicals.
8) The method of 1) wherein the radicals are generated using:
9) The method of 2) wherein the etch selectivity of the SiN constituting the SiN film and that of the SiN constituting the another film are differently adjusted by changing the following process conditions:
10) The method of 1) wherein the etch selectivity of the SiN film relative to that of the another film which is oxide (SiO, TiO, ZrO) is adjusted by changing the following conditions:
11) The method of 1) wherein a reaction chamber for the etching process is clustered with the reaction chamber for the deposition process, and the deposition process and the etching process are sequentially and continuously conducted without breaking a vacuum.
12) The method of 4) wherein the etch selectivity of the SiN and that of the another film are adjusted by changing the process temperature during the deposition process.
In yet another aspect, embodiments include, but are not limited to, at least one of the following features or two or more of the following features in any sensical combinations:
1) A method of tuning a topology profile of a film formed on a patterned surface of a substrate, which patterned surface is constituted by a step structure composed of a horizontal surface (typically a top surface and a bottom surface of a recess) and a vertical surface (typically sidewalls of the recess), the method comprising: (1) depositing a film on the patterned surface of the substrate in a reaction chamber in a manner that a portion of the film deposited on the horizontal surface and a portion of the film deposited on the vertical surface have different chemical resistance properties; and (2) subjecting the film to isotropic dry etching in the reaction chamber in a manner (a) removing predominantly the portion of the film deposited on the horizontal surface so as to leave predominantly or substantially solely the portion of the film deposited on the vertical surface, or (b) removing predominantly the portion of the film deposited on the vertical surface so as to leave predominantly or substantially solely the portion of the film deposited on the horizontal surface.
2) The method of 1) wherein the isotropic dry etching is conducted using a remote plasma system.
3) The method of 1) wherein the film is an insulating film.
4) The method of 3) wherein the insulating film is constituted by SiN or SiO.
5) The method of 3) wherein the insulating film is deposited using a capacitively coupled plasma (CCP).
6) The method of 4) wherein the insulating film is a SiN film which is deposited using at least one precursor selected from the group consisting of aminosilane, halogenated silane, mono-silane, and di-silane.
7) The method of 3) wherein the insulating film is subjected to the dry etching in process (b) which uses a fluorine-containing dry gas such as NF3 and/or CF4 as an etchant, and a dilution gas such as Ar, N2, and/or He.
8) The method of 1) wherein the film is deposited in process (a) by plasma-enhanced chemical vapor deposition (PECVD), plasma-enhanced atomic layer deposition (PEALD), or high-density plasma chemical vapor deposition (HDPCVD).
In some embodiments, a remote plasma is used for dry etching of the film in process (b), which is commonly or conventionally used for chamber cleaning. The use of a remote plasma for dry etching of the film yields significant advantages including high productivity, i.e., high etch rate which is remarkably higher than that of wet etching. Since the etch rate of the remote plasma dry etching is high, in order to improve controllability of etch rate of the remote plasma dry etching, the concentration or flow rate of an etchant such as NF3, for example, may be set at a value lower than (e.g., 10% to 90%, 30% to 70%, or about 50% of) that normally used for chamber cleaning. Further, when the film is deposited along surfaces of a trench, the aspect ratio of the trench may affect controllability of isotropic dry etching. In order to alleviate such a problem, etch selectivity of the sidewall portion relative to the top/bottom portion of the film deposited in the trench, for example, may be tuned by adjusting the film quality of these portions, differently, by changing the deposition pressure, for example, in process (a) (deposition process).
Some aspects and/or embodiments of the present invention will be explained in detail with reference to the drawings by way of examples, but the present invention is not intended to be limited thereto.
In step S14, upon completion of deposition of the second dielectric layer in the reaction chamber 1, the substrate is transferred to a reaction chamber 2 (“Transfer to RC2”) for dry etching which may be attached to a wafer transfer chamber with a wafer handling robot, to which the reaction chamber 1 is also attached, so that the substrate may be transferred to the reaction chamber 2 without being exposed to the air. In step S15, the second dielectric layer is exposed to the fluorine and/or chlorine radicals under dry-etching conditions (“Radical Etch”), thereby removing at least a part of the second dielectric layer without removing the first dielectric layer, thereby forming a layer structure having a topology profile on the substrate. Radical etching may be isotropic etching using primarily or predominantly radicals rather than ions (preferably substantially no or little ions) so that substantially conformal etching can be performed (i.e., substantially no or little directionality of etching) when the second dielectric layer is conformal and has homogenous (in-plane quality uniformity), resulting in a conformal final layer structure, whereas radical etching may function as anisotropic etching when the second dielectric layer is not conformal (e.g., top-predominant deposition) and/or has an in-plane quality variation (e.g., side-low quality), resulting in a final layer structure having a top-remaining topology profile or a side-remaining topology profile. Radical etching is similar to wet etching but is much faster etching than wet etching.
In process scheme (b) in
Process scheme (b) can be achieved using the following reactor design in some embodiments, which is shown solely by way of example. For radical etching, a plasma is not in direct contact with a substrate in a reaction chamber. In some embodiments, a possible plasma source is a remote plasma which may be a capacitively coupled plasma (CCP), inductively coupled plasma (ICP), or microwave plasma (MWP). Thus, an in-situ CCP, where two electrodes are parallelly provided in a chamber and a substrate is placed between the two electrodes, is not suitable for radical etching.
For conducting radical etching, the apparatus illustrated in
In some embodiments which are illustrated in (b) in
For etching, in
In some embodiments, the combined process of deposition and dry etching utilizing effective dry etch selectivity of two layers may be suitably applied to 3DNAND fabrication.
A skilled artisan will appreciate that the apparatus includes one or more controller(s) (not shown) programmed or otherwise configured to cause the deposition and reactor cleaning processes described elsewhere herein to be conducted. The controller(s) are communicated with the various power sources, heating systems, pumps, robotics, and gas flow controllers or valves of the reactor, as will be appreciated by the skilled artisan.
The present invention is further explained with reference to working examples below. However, the examples are not intended to limit the present invention. In the examples where conditions and/or structures are not specified, the skilled artisan in the art can readily provide such conditions and/or structures, in view of the present disclosure, as a matter of routine experimentation. For example, in the following examples, any suitable precursors used for depositing dielectric films constituted by TiO2, TiN, or the like, such as those disclosed in U.S. Pat. No. 9,556,516 issued Jan. 31, 2017, and/or U.S. Pat. No. 9,171,716 issued Oct. 27, 2015, can be selected and used by the skilled artisan as a matter of routine experimentation, each disclosure of which is herein incorporated by reference in its entirety. Also, for example, in the following examples, any suitable precursors used for depositing dielectric films constituted by SiO2-, SiN, or the like, such as those disclosed in U.S. Pat. No. 8,197,915 issued Jun. 12, 2012 and U.S. Pat. No. 9,824,881 issued Nov. 21, 2017, can be selected and used by the skilled artisan as a matter of routine experimentation, each disclosure of which is herein incorporated by reference in its entirety. Also, the numbers applied in the specific examples can be modified by a range of at least±50% in some embodiments, and the numbers are approximate.
A TiO2 film was deposited on each substrate by PEALD under the following deposition conditions:
Next, one of the substrates with the TiO2 film was exposed to a NF3 remote CCP plasma (NF3 radicals) at a temperature of 100° C., and another of the substrate with the TiO2 film was exposed to a NF3 remote CCP plasma (NF3 radicals) at a temperature of 200° C. The NF3 remote plasma unit (PRU) was set at the following conditions (hereinafter referred to as “XP5”):
A TiO2 film was deposited (referred to as “TiO-1”) on a substrate by PEALD under the deposition conditions which were the same as in Reference Example 1. Another TiO2 film was deposited (referred to as “TiO-2”) on a substrate by PEALD under the deposition conditions which were the same as in Reference Example 1 except that the feed time of the precursor during the ALD process was 0.05 s for TiO-1 and that was 0.4 s for TiO-2, and the film thickness of TiO-1 was 24 nm, and that of TiO-2 was 18 nm.
A SiO2 film was deposited (referred to as “SiO-1”) on a substrate by PEALD under the following deposition conditions:
Plasma: O2 Plasma (Reaction gas: O2; Power: 500 W, 13.56 MHz); Deposition temperature: 200° C.; Deposition pressure: 400 Pa; Film thickness: 30 nm.
Another SiO2 film was deposited (referred to as “SiO-2”) on a substrate by PEALD under the deposition conditions which were the same as those for SiO-1 except that the deposition temperature was 75° C., and the RF power was 50 W.
Next, the substrates with TiO-1, TiO-2, SiO-1, and SiO-2 were exposed to a NF3 remote CCP plasma (NF3 radicals) at a temperature of 200° C. for 40 s. The NF3 PRU was set at condition XP5.
A TiO2 film was deposited on a substrate having trenches by PEALD in the same manner as in Reference Example 1. This TiO2 film corresponded to TiO-1 in Reference Example 2.
Next, the substrates with the TiO-1 film was exposed to a NF3 remote CCP plasma (NF3 radicals) at a temperature of 200° C. The NF3 remote plasma unit (PRU) was set at the XP5 conditions.
A TiO2 film was deposited on a substrate having trenches by PEALD in the same manner as in Reference Example 2. This TiO2 film corresponded to TiO-2 in Reference Example 2.
Next, the substrates with the TiO-2 film was exposed to a NF3 remote CCP plasma (NF3 radicals) at a temperature of 200° C. The NF3 remote plasma unit (PRU) was set at the XP5 conditions.
TiO-1 and TiO-2 had a similar etch rate for the used etching conditions as shown in
Various SiN films (SiN-1 to SiN-7) and a SiO film were deposited on substrates, respectively, under the following deposition conditions:
SiN-5 (PEALD): Deposition temperature 450° C.; Deposition pressure: 3 Ton; Plasma: NH3 plasma (Reaction gas: NH3; Power: 125 W); Film thickness: 50 nm.
SiO (PEALD): Same as those for SiO-1 (Reference Example 2); Film thickness: 40 nm.
SiN-1, SiN-2, SiN-3, and SiN-6 used a same first precursor, and SiN-4 and SiN-5 used a same second precursor which was different from the first precursor. The thickness of the deposited SiN films ranged between 25 nm and 55 nm, which were deposited on silicon substrates, respectively, by PEALD or other processes with different precursors and plasma conditions. The standard sample of SiN film (SiN-7) was deposited with NH3 and SiH2Cl2 by low-pressure CVD. The density of the SiN-7 film was 3.18 g/cm3. The essence here was that each film had a different density and/or a different hydrogen content, etc., and these differences determined its etch rate and/or RI (refractive index). The RI of the film can thus be used to estimate the etch rate (as discussed in relation to
Next, each substrate with the above SiN film was exposed to a NF3 remote CCP plasma (NF3 radicals) under condition XP5 except that the chamber temperature was 25° C. The substrate with the SiO film was exposed to SF6 radicals, in place of NF3 radicals. It should be noted that it was confirmed in a separate experiment that not only SF6 radicals but also NF3 radicals worked for SiO film.
It should be noted that films constituted by TiO2, ZrO2, or the like were deposited by PEALD in a manner similar to SiO2, and showed etch selectivity similar to that of SiO2.
The films of SiN-1 to SiN-6 and SiO were formed on substrates, respectively, in the same manner as in Reference Example 3, and then, instead of radical dry etching used in Reference Example 3, the films were subjected to wet etching (dHF 100:1).
By using SF6, in place of NF3, generated in a remote microwave plasma (2.45 GHz, 50 W, 2 Pa), the difference in etch rate between the SiN films can further be increased to a maximum of 100. The etch selectivity of a SiN film relative to SiO2 or other oxide was at least 25 for SiN-1 and at least 4000 for SiN-2 (after taking the measurement error into account). It should be noted that the longer the experiment duration, the lower the measurement error becomes, meaning that the etch selectivity is likely to be close to perfect (infinite).
Reference Example 5
The SiN films constituted by SiN-1 to SiN-7, respectively, described in Reference Example 3 were subjected to further analysis, wherein their refractive indexes were measured.
The SiN films constituted by SiN-1 to SiN-6, respectively, described in Reference Example 3 were subjected to further analysis, wherein their compositions/densities were analyzed.
A SiN-4 film was deposited on a substrate having trenches (250 nm in depth, 150 nm in opening width) by PEALD in the same manner as in Reference Example 3. The thickness of the SiN-4 film on the top surface of the substrate was 26 nm. Also, a SiN-3 film was deposited on a substrate having trenches (250 nm in depth, 150 nm in opening width) by PEALD in the same manner as in Reference Example 3. The thickness of the SiN-3 film on the top surface of the substrate was 29 nm. A target topology profile of a final layer structure using the SiN-4 film was a side-remaining topology profile, whereas that using the SiN-3 film was a top/bottom-remaining topology profile.
The deposition conditions for the SiN-4 film had been turned to perform top/bottom low-quality (low density) deposition by manipulating the process parameters as discussed in this disclosure, as follows:
Similarly, the deposition conditions for the SiN-3 film had been turned to perform side low-quality (low density) deposition by manipulating the process parameters as discussed in this disclosure.
Next, the substrates with the SiN-4 film and the SiN-3 film were exposed to a NF3 remote CCP plasma (NF3 radicals) at a temperature of 25° C., respectively. The NF3 remote plasma unit (PRU) was set at the XP5 conditions.
SiN films A, B, and C were deposited on substrates having trenches, respectively, by PEALD under deposition conditions shown in
Next, SiN films A, B, and C were exposed to a NF3 remote CCP plasma (NF3 radicals) under the dry-etching conditions shown in
It will be understood by those of skill in the art that numerous and various modifications can be made without departing from the spirit of the present invention. Therefore, it should be clearly understood that the forms of the present invention are illustrative only and are not intended to limit the scope of the present invention.
This application is a continuation of, and claims priority to, U.S. patent application Ser. No. 17/192,865 filed Mar. 4, 2021 titled METHOD FOR FABRICATING LAYER STRUCTURE HAVING TARGET TOPOLOGIAL PROFILE, which claims the benefit of U.S. Provisional Patent Application No. 62/988,907, filed on Mar. 12, 2020, in the United States Patent and Trademark Office, the disclosures of which are incorporated herein in their entirety by reference.
| Number | Date | Country | |
|---|---|---|---|
| 62988907 | Mar 2020 | US |
| Number | Date | Country | |
|---|---|---|---|
| Parent | 17192865 | Mar 2021 | US |
| Child | 18530759 | US |
