Patent Application
20240258116
The present technology relates to semiconductor processes and equipment. More specifically, the present technology relates to selectively etching titanium-containing structures.
Integrated circuits are made possible by processes which produce intricately patterned material layers on substrate surfaces. Producing patterned material on a substrate requires controlled methods for removal of exposed material. Chemical etching is used for a variety of purposes including transferring a pattern in photoresist into underlying layers, thinning layers, or thinning lateral dimensions of features already present on the surface. Often it is desirable to have an etch process that etches one material faster than another facilitating, for example, a pattern transfer process. Such an etch process is said to be selective to the first material. As a result of the diversity of materials, circuits, and processes, etch processes have been developed with a selectivity towards a variety of materials.
Etch processes may be termed wet or dry based on the materials used in the process. For example, a wet etch may preferentially remove some oxide dielectrics over other dielectrics and materials. However, wet processes may have difficulty penetrating some constrained trenches and also may sometimes deform the remaining material. Dry etches produced in local plasmas formed within the substrate processing region can penetrate more constrained trenches and exhibit less deformation of delicate remaining structures. However, local plasmas may damage the substrate through the production of electric arcs as they discharge.
Thus, there is a need for improved systems and methods that can be used to produce high quality devices and structures. These and other needs are addressed by the present technology.
Exemplary semiconductor processing methods may include flowing an etchant precursor into a processing region of a semiconductor processing chamber. A substrate may be housed within the processing region. The substrate may define an exposed region of a titanium-containing material. The methods may include contacting the substrate with the etchant precursor. The methods may include removing at least a portion of the titanium-containing material.
In some embodiments, the etchant precursor may be or include a halogen-containing precursor. The etchant precursor may be or include a chlorine-containing precursor. The chlorine-containing precursor may be or include thionyl chloride (SOCl2). Removing the portion of the titanium-containing material may be performed plasma-free. Removing the portion of the titanium-containing material may be performed at a temperature less than or about 450° C. Removing the portion of the titanium-containing material may be performed at a pressure greater than or about 0.1 Torr. Removing the portion of the titanium-containing material may be performed at a pressure less than or about 50 Torr. The methods may include a pre-treatment performed prior to flowing the etchant precursor. The pre-treatment may include contacting the substrate with a plasma comprising one or more of oxygen, hydrogen, or nitrogen. The methods may include a post-treatment performed subsequent removing the portion of the titanium-containing material. The post-treatment may include contacting the substrate with a plasma comprising one or more of oxygen, hydrogen, or nitrogen.
Some embodiments of the present technology may encompass semiconductor processing methods. The methods may include forming a plasma of a treatment precursor comprising one or more of oxygen, hydrogen, or nitrogen to produce treatment plasma effluents. The methods may include flowing the treatment plasma effluents into a processing region of a semiconductor processing chamber. A substrate may be housed within the processing region. The substrate may define an exposed region of a titanium-containing material. The methods may include contacting the substrate with the treatment plasma effluents. The treatment plasma effluents may be configured to remove a residue from a surface of the titanium-containing material. The methods may include flowing an etchant precursor into the processing region of the semiconductor processing chamber. The methods may include contacting the substrate with the etchant precursor. The methods may include removing at least a portion of the titanium-containing material.
In some embodiments, the methods may include halting formation of the plasma of the treatment precursor prior to flowing the etchant precursor. The etchant precursor may be or include thionyl chloride (SOCl2). Removing the portion of the titanium-containing material may be performed at a temperature less than or about 400° C. Removing the portion of the titanium-containing material may be performed at a pressure less than or about 30 Torr. The methods may include a post-treatment performed subsequent removing the portion of the titanium-containing material. The post-treatment may include contacting the substrate with a plasma comprising one or more of oxygen, hydrogen, or nitrogen.
Some embodiments of the present technology may include semiconductor processing methods. The methods may include flowing an etchant precursor into a processing region of a semiconductor processing chamber. A substrate may be housed within the processing region. The substrate may define an exposed region of a titanium-containing material. The methods may include contacting the substrate with the etchant precursor. The methods may include removing at least a portion of the titanium-containing material. The methods may include forming a plasma of a treatment precursor comprising one or more of oxygen, hydrogen, or nitrogen to produce treatment plasma effluents. The methods may include contacting the substrate with the treatment plasma effluents.
In some embodiments, the etchant precursor may include chlorine. The treatment plasma effluents may be configured to remove residual chlorine from one or more of the substrate or the semiconductor processing chamber. Removing the portion of the titanium-containing material may be performed at a temperature less than or about 380° C. and at a pressure less than or about 30 Torr.
Such technology may provide numerous benefits over conventional systems and techniques. For example, the processes may allow dry etching to be performed that may protect features of the substrate. Additionally, the processes may selectively remove titanium-containing films relative to other exposed materials on the substrate. These and other embodiments, along with many of their advantages and features, are described in more detail in conjunction with the below description and attached figures.
A further understanding of the nature and advantages of the disclosed technology may be realized by reference to the remaining portions of the specification and the drawings.
Several of the figures are included as schematics. It is to be understood that the figures are for illustrative purposes, and are not to be considered of scale unless specifically stated to be of scale. Additionally, as schematics, the figures are provided to aid comprehension and may not include all aspects or information compared to realistic representations, and may include additional or exaggerated material for illustrative purposes.
In the appended figures, similar components and/or features may have the same reference label. Further, various components of the same type may be distinguished by following the reference label by a letter that distinguishes among the similar components. If only the first reference label is used in the specification, the description is applicable to any one of the similar components having the same first reference label irrespective of the letter.
Diluted acids may be used in many different semiconductor processes for cleaning substrates and removing materials from those substrates. For example, diluted hydrofluoric acid (“DHF”) can be an effective etchant for silicon oxide, aluminum oxide, titanium oxide, and other materials, and may be used to remove these materials from substrate surfaces. After the etching or cleaning operation is complete, the acid may be dried from the wafer or substrate surface. Using DHF may be termed a “wet” etch where the diluent is often water. Additional etching processes may be used that utilize precursors delivered to the substrate. For example, plasma enhanced processes may also selectively etch materials by enhancing precursors through the plasma to perform a dry etch.
Although wet etchants using aqueous solutions or water-based processes may operate effectively for certain substrate structures, the water may pose challenges in a variety of conditions. For example, utilizing water during etch processes may cause issues when disposed on substrates including metal materials. For example, certain later fabrication processes, such as recessing gaps, removing oxide dielectric, or other processes to remove oxygen-containing materials, may be performed after an amount of metallization has been formed on a substrate. If water is utilized in some fashion during the etching, an electrolyte may be produced, which when contacting the metal material, may cause galvanic corrosion to occur between dissimilar metals, and the metal may be corroded or displaced in various processes. In addition, because of the surface tension of the water diluent, pattern deformation and collapse may occur with minute structures. The water-based material may also be incapable of penetrating some high aspect ratio features due to surface tension effects. Plasma etching may overcome the issues associated with water-based etching, although additional issues may occur. For example, a reactive ion etch process may expose the metal to ion activity, which through bombardment can damage the structure, and affect electrical characteristics.
The present technology overcomes these issues by performing a dry etch process that may passivate a number of materials relative to a material to be etched, and in some embodiments a process may be plasma free during the etching. By utilizing particular precursors that may facilitate halogen dissociation to provide etchant materials, an etch process may be performed that may protect the surrounding structures. Additionally, the materials and conditions used may allow improved etching relative to conventional techniques.
Although the remaining disclosure will routinely identify specific etching processes utilizing the disclosed technology, it will be readily understood that the systems and methods are equally applicable to deposition and cleaning processes as may occur in the described chambers, as well as other etching technology and other etching that may be performed with a variety of exposed materials that may be maintained or substantially maintained. Accordingly, the technology should not be considered to be so limited as for use with the exemplary etching processes or chambers alone. Moreover, although an exemplary chamber is described to provide foundation for the present technology, it is to be understood that the present technology can be applied to virtually any semiconductor processing chamber that may allow the operations described.
The substrate processing chambers 108a-f may include one or more system components for depositing, annealing, curing and/or etching a dielectric film on the substrate wafer. In one configuration, two pairs of the processing chambers, e.g., 108c-d and 108e-f, may be used to deposit dielectric material on the substrate, and the third pair of processing chambers, e.g., 108a-b, may be used to etch the deposited dielectric. In another configuration, all three pairs of chambers, e.g., 108a-f, may be configured to etch a dielectric film on the substrate. Any one or more of the processes described may be carried out in chamber(s) separated from the fabrication system shown in different embodiments. It will be appreciated that additional configurations of deposition, etching, annealing, and curing chambers for dielectric films are contemplated by system 100.
A cooling plate 203, faceplate 217, ion suppressor 223, showerhead 225, and a pedestal 265 or substrate support, having a substrate 255 disposed thereon, are shown and may each be included according to embodiments. The pedestal 265 may have a heat exchange channel through which a heat exchange fluid flows to control the temperature of the substrate, which may be operated to heat and/or cool the substrate or wafer during processing operations. The wafer support platter of the pedestal 265, which may include aluminum, ceramic, or a combination thereof, may also be resistively heated in order to achieve relatively high temperatures, such as from up to or about 100° C. to above or about 1100° C., using an embedded resistive heater element.
The faceplate 217 may be pyramidal, conical, or of another similar structure with a narrow top portion expanding to a wide bottom portion. The faceplate 217 may additionally be flat as shown and include a plurality of through-channels used to distribute process gases. Plasma generating gases and/or plasma excited species, depending on use of the RPS 201, may pass through a plurality of holes, shown in
Exemplary configurations may include having the gas inlet assembly 205 open into a gas supply region 258 partitioned from the first plasma region 215 by faceplate 217 so that the gases/species flow through the holes in the faceplate 217 into the first plasma region 215. Structural and operational features may be selected to prevent significant backflow of plasma from the first plasma region 215 back into the supply region 258, gas inlet assembly 205, and fluid supply system 210. The faceplate 217, or a conductive top portion of the chamber, and showerhead 225 are shown with an insulating ring 220 located between the features, which allows an AC potential to be applied to the faceplate 217 relative to showerhead 225 and/or ion suppressor 223. The insulating ring 220 may be positioned between the faceplate 217 and the showerhead 225 and/or ion suppressor 223 enabling a capacitively coupled plasma (CCP) to be formed in the first plasma region. A baffle (not shown) may additionally be located in the first plasma region 215, or otherwise coupled with gas inlet assembly 205, to affect the flow of fluid into the region through gas inlet assembly 205.
The ion suppressor 223 may comprise a plate or other geometry that defines a plurality of apertures throughout the structure that are configured to suppress the migration of ionically-charged species out of the first plasma region 215 while allowing uncharged neutral or radical species to pass through the ion suppressor 223 into an activated gas delivery region between the suppressor and the showerhead. In embodiments, the ion suppressor 223 may comprise a perforated plate with a variety of aperture configurations. These uncharged species may include highly reactive species that are transported with less reactive carrier gas through the apertures. As noted above, the migration of ionic species through the holes may be reduced, and in some instances completely suppressed. Controlling the amount of ionic species passing through the ion suppressor 223 may advantageously provide increased control over the gas mixture brought into contact with the underlying wafer substrate, which in turn may increase control of the deposition and/or etch characteristics of the gas mixture. For example, adjustments in the ion concentration of the gas mixture can significantly alter its etch selectivity. In alternative embodiments in which deposition is performed, it can also shift the balance of conformal-to-flowable style depositions for dielectric materials.
The plurality of apertures in the ion suppressor 223 may be configured to control the passage of the activated gas, i.e., the ionic, radical, and/or neutral species, through the ion suppressor 223. For example, the aspect ratio of the holes, or the hole diameter to length, and/or the geometry of the holes may be controlled so that the flow of ionically-charged species in the activated gas passing through the ion suppressor 223 is reduced. The holes in the ion suppressor 223 may include a tapered portion that faces the plasma excitation region 215, and a cylindrical portion that faces the showerhead 225. The cylindrical portion may be shaped and dimensioned to control the flow of ionic species passing to the showerhead 225. An adjustable electrical bias may also be applied to the ion suppressor 223 as an additional means to control the flow of ionic species through the suppressor.
The ion suppressor 223 may function to reduce or eliminate the amount of ionically charged species traveling from the plasma generation region to the substrate. Uncharged neutral and radical species may still pass through the openings in the ion suppressor to react with the substrate. It should be noted that the complete elimination of ionically charged species in the reaction region surrounding the substrate may not be performed in embodiments. In certain instances, ionic species are intended to reach the substrate in order to perform the etch and/or deposition process. In these instances, the ion suppressor may help to control the concentration of ionic species in the reaction region at a level that assists the process.
Showerhead 225 in combination with ion suppressor 223 may allow a plasma present in first plasma region 215 to avoid directly exciting gases in substrate processing region 233, while still allowing excited species to travel from chamber plasma region 215 into substrate processing region 233. In this way, the chamber may be configured to prevent the plasma from contacting a substrate 255 being etched. This may advantageously protect a variety of intricate structures and films patterned on the substrate, which may be damaged, dislocated, or otherwise warped if directly contacted by a generated plasma. Additionally, when plasma is allowed to contact the substrate or approach the substrate level, the rate at which oxide species etch may increase. Accordingly, if an exposed region of material is oxide, this material may be further protected by maintaining the plasma remotely from the substrate.
The processing system may further include a power supply 240 electrically coupled with the processing chamber to provide electric power to the faceplate 217, ion suppressor 223, showerhead 225, and/or pedestal 265 to generate a plasma in the first plasma region 215 or processing region 233. The power supply may be configured to deliver an adjustable amount of power to the chamber depending on the process performed. Such a configuration may allow for a tunable plasma to be used in the processes being performed. Unlike a remote plasma unit, which is often presented with on or off functionality, a tunable plasma may be configured to deliver a specific amount of power to the plasma region 215. This in turn may allow development of particular plasma characteristics such that precursors may be dissociated in specific ways to enhance the etching profiles produced by these precursors.
A plasma may be ignited either in chamber plasma region 215 above showerhead 225 or substrate processing region 233 below showerhead 225. Plasma may be present in chamber plasma region 215 to produce the radical precursors from an inflow of, for example, a fluorine-containing precursor or other precursor. An AC voltage typically in the radio frequency (RF) range may be applied between the conductive top portion of the processing chamber, such as faceplate 217, and showerhead 225 and/or ion suppressor 223 to ignite a plasma in chamber plasma region 215 during deposition. An RF power supply may generate a high RF frequency of 13.56 MHz but may also generate other frequencies alone or in combination with the 13.56 MHz frequency.
The gas distribution assemblies such as showerhead 225 for use in the processing chamber section 200 may be referred to as dual channel showerheads (DCSH) and are additionally detailed in the embodiments described in
The showerhead 225 may comprise an upper plate 214 and a lower plate 216. The plates may be coupled with one another to define a volume 218 between the plates. The coupling of the plates may be so as to provide first fluid channels 219 through the upper and lower plates, and second fluid channels 221 through the lower plate 216. The formed channels may be configured to provide fluid access from the volume 218 through the lower plate 216 via second fluid channels 221 alone, and the first fluid channels 219 may be fluidly isolated from the volume 218 between the plates and the second fluid channels 221. The volume 218 may be fluidly accessible through a side of the showerhead 225.
The chamber discussed previously may be used in performing exemplary methods including etching methods. Turning to
Method 400 may or may not involve optional operations to develop the semiconductor structure to a particular fabrication operation. It is to be understood that method 400 may be performed on any number of semiconductor structures or substrates 505, as illustrated in
It is to be understood that the noted structure is not intended to be limiting, and any of a variety of other semiconductor structures including titanium-containing materials are similarly encompassed. Other exemplary structures may include two-dimensional and three-dimensional structures common in semiconductor manufacturing, and within which a titanium-containing material such as titanium nitride is to be removed relative to one or more other materials, as the present technology may selectively remove titanium-containing materials relative to other exposed materials, such as silicon-containing materials, metal-containing materials, oxides, and other nitrides, as well as any of the other materials discussed elsewhere. Additionally, although a high-aspect-ratio structure may benefit from the present technology, the technology may be equally applicable to lower aspect ratios and any other structures.
For example, layers of material according to the present technology may be characterized by any aspect ratios or the height-to-width ratio of the structure, although in some embodiments the materials may be characterized by larger aspect ratios, which may not allow sufficient etching utilizing conventional technology or methodology. For example, in some embodiments the aspect ratio of any layer of an exemplary structure may be greater than or about 10:1, greater than or about 20:1, greater than or about 30:1, greater than or about 40:1, greater than or about 50:1, or greater. Additionally, each layer may be characterized by a reduced width or thickness less than or about 100 nm, less than or about 80 nm, less than or about 60 nm, less than or about 50 nm, less than or about 40 nm, less than or about 30 nm, less than or about 20 nm, less than or about 10 nm, less than or about 5 nm, less than or about 1 nm, or less, including any fraction of any of the stated numbers, such as 20.5 nm, 1.5 nm, etc. This combination of high aspect ratios and minimal thicknesses may frustrate many conventional etching operations, or require substantially longer etch times to remove a layer, along a vertical or horizontal distance through a confined width. Moreover, damage to or removal of other exposed layers may occur with conventional technologies as well.
Method 400 may be performed to remove an exposed titanium-containing material in embodiments, although any number of nitride or titanium-containing materials may be removed in any number of structures in embodiments of the present technology. The methods may include specific operations for the removal of titanium-containing materials, and may include one or more optional operations to prepare or treat the titanium-containing materials. For example, an exemplary substrate structure may have previous processing residues on a film to be removed, such as titanium nitride. For example, residual photoresist or byproducts from previous processing may reside on the titanium nitride layer. These materials may prevent access to the titanium nitride, or may interact with etchants differently than a clean titanium nitride surface, which may frustrate one or more aspects of the etching. Accordingly, in some embodiments an optional pre-treatment of the titanium-containing film or material may occur at optional operation 405. Exemplary pre-treatment operations may include a thermal treatment, wet treatment, or plasma treatment, for example, which may be performed in chamber 200 as well as any number of chambers that may be included on system 100 described above.
In one exemplary plasma treatment, a remote or local plasma may be developed from a precursor intended to interact with residues in one or more ways. For example, utilizing chambers such as chamber 200 described above, either a remote or local plasma may be produced from one or more precursors. For example, an oxygen-containing precursor, a hydrogen-containing precursor, a nitrogen-containing precursor, a helium-containing precursor, or some other precursor may be flowed into a remote plasma region or into the processing region, where a plasma may be struck. The plasma effluents may be flowed to the substrate, and may contact the residue material. The plasma process may be either physical or chemical depending on the material to be removed to expose the titanium-containing material. For example, plasma effluents may be flowed to contact and physically remove the residue, such as by a sputtering operation, or the precursors may be flowed to interact with the residues to produce volatile byproducts that may be removed from the chamber.
Exemplary precursors used in the pre-treatment may be or include hydrogen, a hydrocarbon, water vapor, an alcohol, hydrogen peroxide, or other materials that may include hydrogen as would be understood by the skilled artisan. Exemplary oxygen-containing precursors may include molecular oxygen, ozone, nitrous oxide, nitric oxide, or other oxygen-containing materials. Nitrogen gas may also be used, or a combination precursor having one or more of hydrogen, oxygen, and/or nitrogen may be utilized to remove particular residues. Once the residue or byproducts have been removed, a clean titanium nitride surface may be exposed for etching. The halogen-containing precursor may be flowed through a remote plasma region of the processing chamber, such as region 215 described above, although in some embodiments method 400 may not utilize plasma effluents during the etching operations. For example, method 400 may flow a fluorine-containing or other halogen-containing precursor to the substrate without exposing the precursor to a plasma, and may perform the removal of the titanium-containing material without production of plasma effluents. In some embodiments the halogen-containing precursor may be plasma enhanced, which may occur in a remote plasma region to protect materials on the substrate from contact with plasma effluents. The halogen-containing precursor may contact a semiconductor substrate including an exposed titanium-containing material, and may produce a fluorinated material, such as titanium fluoride or an titanium halide material, which may remain on the semiconductor substrate. The halogen-containing precursor may donate one or more fluorine atoms, while accepting one or more oxygen atoms in some embodiments. Some halogen-containing precursors, such as plasma enhanced precursors, may provide fluorine radicals, while other plasma radicals may accept oxygen from the film.
Method 400 may include flowing an etchant precursor into the substrate processing region of a semiconductor processing chamber housing the described substrate, or some other substrate, at operation 410. The etchant precursor may be flowed through a remote plasma region of the processing chamber, such as region 215 described above, although in some embodiments method 400 may not utilize plasma effluents during the etching operations. For example, method 400 may flow the etchant precursor to the substrate without exposing the precursor to a plasma, and may perform the removal of the titanium-containing material without production of plasma effluents. In some embodiments, the etchant precursor may be plasma enhanced, which may occur in a remote plasma region to protect materials on the substrate from contact with plasma effluents. The etchant precursor may contact a semiconductor substrate including an exposed region of titanium-containing material, and may produce a chlorinated material, such as titanium chloride fluoride or a titanium halide material, which may remain on the semiconductor substrate or may volatize. The halogen-containing precursor may donate one or more chlorine atoms, while accepting one or more nitrogen atoms in some embodiments. Some halogen-containing precursors, such as plasma enhanced precursors, may provide chlorine radicals, while other plasma radicals may accept nitrogen from the film. Accordingly, the etchant precursor may etch or remove the titanium-containing material at operation 415, as shown in
As noted above, the present technology may be performed without plasma development during the etching operations 410-415. By utilizing particular precursors, and performing the etching within certain process conditions, a plasma-free removal may be performed, and the removal may also be a dry etch. Accordingly, techniques according to aspects of the present technology may be performed to remove titanium nitride from narrow features, as well as high aspect ratio features, and thin dimensions that may otherwise be unsuitable for wet etching. An optional operation may be performed to clear the substrate or chamber of residues and may include a post-treatment at optional operation 420. The post-treatment may include similar operations as the pre-treatment, and may include any of the precursors or operations discussed above for the pre-treatment. The post-treatment may clear residual etchant, such as chlorine, from the substrate or chamber in some embodiments. It is to be understood that although the pre-treatment and/or post-treatment operations may include plasma generation and plasma effluent delivery to the substrate, plasma may not be formed during the etching operations 410-415. For example, in some embodiments no plasma may be generated while the etchant precursor or precursors are being delivered into the processing chamber.
The etchant precursor during the etching operations 410-415 may include halogen-containing precursors, and may include one or more of fluorine or chlorine in some embodiments. The specific precursors may be based on bonding or stability of the precursors. An exemplary etchant precursor may include thionyl chloride (SOCl2), as well as halogen-containing precursors such as other chlorine-containing precursors or fluorine-containing precursors. The etchant may also be flown together with a variety of other precursors. In some embodiments, in addition to the etchant precursor, boron trichloride (BCl3), nitrogen trifluoride (NF3), tungsten hexafluoride (WF6), or other halogen-containing precursors may optionally be delivered to a remote plasma region to be plasma enhanced prior to being flowed to the processing region. In embodiments, the etchant precursor may be provided with a hydrogen-containing precursor, such as molecular hydrogen (H2). The etchant precursor may also be provided with any number of carrier gases, which may include nitrogen, helium, argon, or other noble, inert, or useful precursors. The carrier gases may serve to dilute the etchant precursor, which may control etch rate, as well as distribute the etchant precursor.
As a non-limiting example, thionyl chloride (SOCl2) may readily donate a chlorine atom or two as well as an oxygen atom at elevated temperatures, and accept a nitrogen atom, such as from the titanium nitride, and be maintained in a gas phase. Accordingly, titanium-containing materials may be developed as reaction byproducts, which may be gas molecules and may be pumped or removed from the processing chamber. For example, chlorine from the etchant precursor may combine with the titanium nitride to form titanium tetrachloride (TiCl4), titanium(III) chloride (TiCl3), or titanium oxychloride (TiOCl2). Additionally, nitrogen-containing materials may be developed as reaction byproducts, which may be gas molecules and may be pumped or removed from the processing chamber. For example, nitrogen from the titanium nitride may form stable byproducts such as diatomic nitrogen (N2), nitrous oxide (N2O), or nitrogen dioxide (NO2). Further, sulfur-containing materials may be developed as reaction byproducts, which may be gas molecules and may be pumped or removed from the processing chamber. For example, remaining sulfur from the etchant precursor may exist as sulfur dioxide (SO2), sulfur monoxide (SO), or disulfur dichloride (S2Cl2). Accordingly, the process may remove titanium nitride under processing conditions configured to exchange chlorine and nitrogen between the etchant precursor and the exposed region of titanium nitride, which may produce volatile byproducts. Because of the controlled delivery and processing, chlorine-containing materials may not etch or may minimally interact with other exposed surfaces, while readily removing titanium nitride, which may produce enhanced selectivity over conventional techniques.
Processing conditions may impact and facilitate etching according to the present technology. Because the etch reaction may proceed based on thermal dissociation of a halogen from the etchant precursor, the temperatures may be at least partially dependent on the particular halogen and/or other atoms of the etchant precursor in order to initiate dissociation. As temperature increases above or about 250° C., for example, etching begins to occur or increase, which may indicate dissociation of the precursor, and/or activation of the reaction with titanium nitride. As temperature continues to increase, dissociation may be further facilitated as may the reaction with titanium nitride.
Accordingly, in some embodiments of the present technology, etching methods may be performed at substrate, pedestal, and/or chamber temperatures less than or about 450° C., and may be performed at temperatures less than or about 440° C., less than or about 430° C., less than or about 420° C., less than or about 410° C., less than or about 400° C., less than or about 390° C., less than or about 380° C., less than or about 370° C., less than or about 360° C., less than or about 350° C., or lower. The temperature may also be maintained at any temperature within these ranges, within smaller ranges encompassed by these ranges, or between any of these ranges. In some embodiments the method may be performed on substrates that may have a number of produced features, which may produce a thermal budget. In embodiments, a greater temperature may increase etching of the titanium-containing material 425. Accordingly, in some embodiments, the methods may be performed at temperatures greater than or about 300° C., and may be performed at temperatures greater than or about 310° C., greater than or about 320° C., greater than or about 330° C., greater than or about 340° C., greater than or about 350° C., greater than or about 360° C., or higher.
The pressure within the chamber may also affect the operations performed as well as affect at what temperature the etchant precursor may dissociate, such as what temperature the sulfur, oxygen, and chlorine may dissociate when thionyl chloride (SOCl2) is used as the etchant precursor. Accordingly, in some embodiments the pressure may be maintained above or about 0.5 Torr, above or about 1 Torr, above or about 2 Torr, above or about 3 Torr, above or about 4 Torr, above or about 5 Torr, above or about 6 Torr, above or about 7 Torr, above or about 8 Torr, above or about 9 Torr, above or about 10 Torr, above or about 15 Torr, above or about 20 Torr, above or about 25 Torr, above or about 30 Torr, or higher. Additionally, the pressure may be maintained below or about 50 Torr, below or about 40 Torr, below or about 30 Torr, below or about 25 Torr, below or about 20 Torr, below or about 15 Torr, below or about 10 Torr, below or about 9 Torr, below or about 8 Torr, below or about 7 Torr, below or about 6 Torr, below or about 5 Torr, below or about 4 Torr, below or about 3 Torr, below or about 2 Torr, below or about 1 Torr, below or about 0.1 Torr, or less. The pressure may also be maintained at any pressure within these ranges, within smaller ranges encompassed by these ranges, or between any of these ranges. In some embodiments, etch amount may be facilitated and may initiate as pressure increases above about 0.5 Torr. Additionally, as pressure continues to increase, etching may improve up to a point before beginning to reduce, and eventually cease as pressure continues to increase.
Without being bound to any particular theory, pressure within the chamber may affect processing with precursors described above. At low pressures, flow across a substrate may be reduced, and dissociation may similarly be reduced. As pressure increases, interactions between the etchant precursor and the substrate may increase, which may increase reactions and etch rates. However, as pressure continues to increase, recombination of the dissociated etchant precursor atoms may increase due to the relative stability of the molecules. Thus, the precursors may effectively be pumped back out of the chamber without reacting with the substrate. Additionally, interactions with the titanium nitride surface may be suppressed as pressure continues to increase, or byproduct titanium chloride may be reintroduced to the film being etched, further limiting removal. Accordingly, in some embodiments, pressure within the processing chamber may be maintained below or about 30 Torr in some embodiments.
Flow rates of the etchant precursor may be tuned, including in situ, to control the etch process. For example, a flow rate of the etchant precursor may be reduced, maintained, or increased during the removal operations. By increasing the flow rate of the etchant precursor, etch rates may be increased up to a point of saturation. During any of the operations of method 400, the flow rate of the etchant precursor may be between about 5 sccm and about 1,000 sccm. Additionally, the flow rate of the etchant precursor may be maintained below or about 900 sccm, below or about 800 sccm, below or about 700 sccm, below or about 600 sccm, below or about 500 sccm, below or about 400 sccm, below or about 300 sccm, below or about 200 sccm, below or about 100 sccm, or less. The flow rate may also be between any of these stated flow rates, or within smaller ranges encompassed by any of these numbers.
Adding further control to the etch process, the etchant precursor may be pulsed in some embodiments, and may be delivered throughout the etch process either continually or in a series of pulses, which may be consistent or varying over time. The pulsed delivery may be characterized by a first period of time during which the etchant precursor is flowed, and a second period of time during which the etchant precursor is paused or halted. In some embodiments, during the second period of time, a purge gas may be flowed during the second period of time. The purge gas may be or include nitrogen, helium, argon, or other noble, inert, or useful purge gases. The time periods for any pulsing operation may be similar or different from one another with either time period being longer. In embodiments either period of time or a continuous flow of precursor may be performed for a time period greater than or about 1 second, and may be greater than or about 2 seconds, greater than or about 3 seconds, greater than or about 4 seconds, greater than or about 5 seconds, greater than or about 6 seconds, greater than or about 7 seconds, greater than or about 8 seconds, greater than or about 9 seconds, greater than or about 10 seconds, greater than or about 11 seconds, greater than or about 12 seconds, greater than or about 13 seconds, greater than or about 14 seconds, greater than or about 15 seconds, greater than or about 20 seconds, greater than or about 30 seconds, greater than or about 45 seconds, greater than or about 60 seconds, or longer. The times may also be any smaller range encompassed by any of these ranges. For example, in some embodiments, either period of time or a continuous flow of precursor may be performed for a time period less than or about 60 seconds, and may be less than or about 45 seconds, less than or about 30 seconds, less than or about 20 seconds, less than or about 15 seconds, less than or about 10 seconds, less than or about 5 seconds, less than or about 4 seconds, less than or about 3 seconds, less than or about 2 seconds, less than or about 1 seconds, less than or about 0.5 seconds, less than or about 0.1 seconds, or less. In some embodiments as delivery of the precursor occurs for longer periods of time, etch rate may increase.
By performing operations according to embodiments of the present technology, titanium nitride or other titanium-containing materials may be etched selectively relative to other materials, including other oxides or nitrides. For example, the present technology may selectively etch titanium oxide relative to exposed regions of metals, dielectrics including silicon-containing materials including silicon oxide, or other materials. Embodiments of the present technology may etch titanium nitride relative to silicon oxide or any of the other materials at a rate of at least about 2:1, and may etch titanium nitride relative to silicon oxide or other materials noted at a selectivity greater than or about 3:1, greater than or about 4:1, greater than or about 5:1, greater than or about 6:1, greater than or about 7:1, greater than or about 8:1, greater than or about 9:1, greater than or about 10:1, greater than or about 15:1, greater than or about 20:1, greater than or about 25:1, greater than or about 30:1, greater than or about 35:1, greater than or about 40:1, greater than or about 45:1, greater than or about 50:1, or more. For example, etching performed according to some embodiments of the present technology may etch titanium nitride while substantially or essentially maintaining silicon oxide or other materials, such as nitrides or oxides of silicon, aluminum, or hafnium, metals such as tungsten or molybdenum, or materials such as polysilicon for example.
Selectivity may be based in part on precursors used and the ability to dissociate at more controlled temperature ranges. Conventional dry etchants may be incapable of producing etch selectivities of embodiments of the present technology. Similarly, because wet etchants readily remove silicon oxide, wet etchants may also be incapable of etching selectively at rates comparable to embodiments of the present technology.
The previously discussed methods may allow the removal of titanium-containing materials relative to a number of other exposed materials. By utilizing etchants at operating conditions as previously described, improved etching of titanium nitride may be performed, which may both increase selectivity over conventional techniques, as well as improve etching access in small pitch features.
In the preceding description, for the purposes of explanation, numerous details have been set forth in order to provide an understanding of various embodiments of the present technology. It will be apparent to one skilled in the art, however, that certain embodiments may be practiced without some of these details, or with additional details.
Having disclosed several embodiments, it will be recognized by those of skill in the art that various modifications, alternative constructions, and equivalents may be used without departing from the spirit of the embodiments. Additionally, a number of well-known processes and elements have not been described in order to avoid unnecessarily obscuring the present technology. Accordingly, the above description should not be taken as limiting the scope of the technology. Additionally, methods or processes may be described as sequential or in steps, but it is to be understood that the operations may be performed concurrently, or in different orders than listed.
Where a range of values is provided, it is understood that each intervening value, to the smallest fraction of the unit of the lower limit, unless the context clearly dictates otherwise, between the upper and lower limits of that range is also specifically disclosed. Any narrower range between any stated values or unstated intervening values in a stated range and any other stated or intervening value in that stated range is encompassed. The upper and lower limits of those smaller ranges may independently be included or excluded in the range, and each range where either, neither, or both limits are included in the smaller ranges is also encompassed within the technology, subject to any specifically excluded limit in the stated range. Where the stated range includes one or both of the limits, ranges excluding either or both of those included limits are also included.
As used herein and in the appended claims, the singular forms “a”, “an”, and “the” include plural references unless the context clearly dictates otherwise. Thus, for example, reference to “a precursor” includes a plurality of such precursors, and reference to “the material” includes reference to one or more materials and equivalents thereof known to those skilled in the art, and so forth.
Also, the words “comprise(s)”, “comprising”, “contain(s)”, “containing”, “include(s)”, and “including”, when used in this specification and in the following claims, are intended to specify the presence of stated features, integers, components, or operations, but they do not preclude the presence or addition of one or more other features, integers, components, operations, acts, or groups.
