Wet etching process and method for providing uniform etching of materials formed in features having different critical dimensions (CD) - Patent Application 20070122997

Abstract

Embodiments of wet etching processes and methods are disclosed for providing uniform etching of materials formed within features (e.g., trenches, holes, slits, etc.) having different critical dimensions (CDs). By combining non-aqueous organic-based and aqueous-based etching solutions (either sequentially or in parallel) in a wet etching process, the disclosed embodiments take advantage of the opposing effects of CD-dependent etching to provide uniform etching of materials regardless of CD.

Description

[Technical Field]

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS This application claims priority to and the benefit of the filing date of U.S. Non-Provisional Patent Application No. 17 / 942,359, filed September 12, 2022, which is incorporated herein by reference in its entirety. [Background technology]

[0002] The present disclosure relates to processing of substrates. In particular, the present disclosure provides a method for adjusting the etch rate of a wet etching process used to remove material from features having different critical dimensions (CD).

[0003] The formation of semiconductor devices typically involves a series of manufacturing techniques for forming, patterning, and removing layers of material on a substrate. During typical semiconductor manufacturing, various materials formed on a substrate may be removed by patterned etching, chemical-mechanical polishing, and other techniques. Various techniques are known for etching layers on a substrate, including plasma-based or gas-phase etching (also called dry etching) and liquid-based etching (also called wet etching).

[0004] Wet etching generally involves dispensing a chemical solution over the surface of a substrate or immersing the substrate in a chemical solution. The chemical solution (also referred to herein as an etching solution) often contains a solvent and an etchant chemical designed to react with material on the substrate surface and promote dissolution of the reaction products. When the substrate surface is exposed to the etching solution, material is removed from the substrate. The composition and temperature of the etching solution can be controlled to control the etching rate, specificity, and residual material on the surface of the substrate after etching.

[0005] As substrate structure geometries continue to shrink and the types of structures evolve, substrate etching presents increasing challenges. One such challenge is CD-dependent etching of materials formed within narrow features (e.g., trenches, holes, slits, etc.). In many applications, features with different critical dimensions (CDs) may be formed across a substrate. When a wet etching process is utilized to remove material from within such features, the etch rate of material within features with smaller CDs differs from the etch rate of material within features with larger CDs and blanket regions of the substrate. This CD-dependent etching results in non-uniform etch rates and non-uniform removal of material across the substrate. Summary of the Invention [Means for solving the problem]

[0006] This disclosure provides various embodiments of wet etching processes and methods for providing uniform etching of materials formed within features (e.g., trenches, holes, slits, etc.) having different critical dimensions (CDs). When an etching solution is used to remove material within the features, the rate at which material is removed from one or more of the features (i.e., the etch rate) depends on various factors, such as the CD of the feature, the etchant chemistry used in the etching solution, the solvent used in the etching solution, the ratio of the etchant chemistry to the solvent used in the etching solution, the pH of the etching solution, and the wall material adjacent to the material being etched. The difference in etch rate across features of different CDs is known in the art as CD-dependent etching.

[0007] Embodiments described in the present disclosure provide for uniform etching of materials formed within features of different CDs by exposing a substrate comprising the features to an aqueous-based etching solution and a non-aqueous organic-based etching solution, either sequentially or in parallel. An aqueous-based etching solution is a solution comprising one or more etchant chemicals and an aqueous solvent. In contrast, a non-aqueous organic-based etching solution comprises one or more etchant chemicals and an organic solvent. In some embodiments, the wet etching processes and methods disclosed herein may provide for uniform etching of materials within features of different CDs by exposing the substrate to a single etching solution comprising an etchant chemical, an aqueous solvent, and an organic solvent, instead of exposing the substrate to an aqueous-based etching solution and a non-aqueous organic-based etching solution (either sequentially or in parallel).

[0008] When a substrate is exposed to a non-aqueous organic-based etching solution, material may etch faster in features with smaller CDs and slower in features with larger CDs. In other words, when a non-aqueous organic-based etching solution is used, the etch rate may increase in features with smaller CDs and decrease in features with larger CDs. When a substrate is exposed to an aqueous-based etching solution, the etch rate may decrease in features with smaller CDs and increase in features with larger CDs. Thus, in some embodiments, non-aqueous organic-based etching solutions and aqueous-based etching solutions may have opposite effects on the etch rate.

[0009] The present disclosure takes advantage of the difference in etch rates that occurs when non-aqueous organic-based and aqueous-based etching solutions are used to etch materials formed in features with different CDs (e.g., trenches, holes, slits, etc.). The disclosed embodiments take advantage of the opposing effects of CD-dependent etching by combining non-aqueous organic-based and aqueous-based etching solutions (either sequentially or in parallel) in a wet etching process to provide uniform etching of materials regardless of CD. In some embodiments, the ratio of etchant chemicals to solvent used in the etching solution and / or the pH of the etching solution can also be controlled to provide uniform etching of materials formed in features of different CDs.

[0010] According to one embodiment, a method of etching utilizing the techniques described in this disclosure is provided. In some embodiments, the method may begin by providing a substrate having a plurality of features. The critical dimensions (CDs) of the plurality of features may be different for one or more of the features, such that the plurality of features includes at least a first feature having a smaller CD and a second feature having a larger CD.

[0011] The method may then include exposing the substrate to one or more etching solutions, either sequentially or in parallel, to etch material formed within the plurality of features. The one or more etching solutions may generally include an etchant chemical, an aqueous solvent, and an organic solvent, where the organic solvent is an alcohol, a polyhydric alcohol, acetic acid, or a ketone. The methods described herein provide uniform etching of material formed within the plurality of features, regardless of CD, by exposing the substrate to one or more etching solutions, either sequentially or in parallel.

[0012] In some embodiments, the material formed in the features may be an oxide, a dielectric material, silicon, or a metal. In one exemplary embodiment, the material formed in the features (i.e., the material to be etched) may be silicon dioxide (SiO2). In some embodiments, the wall material of the features may include a silicon-containing material, which exhibits a negative surface potential when exposed to aqueous solutions in a particular pH range. For example, the wall material may include amorphous silicon (a-Si), polysilicon (poly-Si), silicon nitride (SiCN), or silicon oxynitride (SiON).

[0013] In some embodiments, exposing the substrate to one or more etching solutions may include exposing the substrate to a first etching solution comprising an etchant chemical and an organic solvent, and exposing the substrate to a second etching solution comprising an etchant chemical and an aqueous solvent. In some embodiments, the etchant chemical may include one or more of hydrofluoric acid (HF), ammonium hydroxide (NH4OH), hydrochloric acid (HCl), hydrogen peroxide (HO), nitric acid (HNO3), phosphoric acid (H3PO4), potassium hydroxide (KOH), and tetramethylammonium hydroxide (TMAH). The aqueous solvent may be water, and the organic solvent may be isopropyl alcohol (C3H8O), propylene carbonate (C4H6O3), acetic acid (CH3COOH), or ethylene glycol (C2H6O2).

[0014] In some embodiments, the etchant chemistry can include anions as the primary reactive species. When anions are utilized as the primary reactive species, exposing the substrate to a first etching solution etches the material formed in the first feature faster than the material formed in the second feature, while exposing the substrate to a second etching solution etches the material formed in the first feature slower than the material forming the second feature. Thus, exposing the substrate to the first etching solution and then exposing the substrate to the second etching solution etches the material formed in the first feature and the material formed in the second feature at a uniform etch rate.

[0015] When a substrate is exposed to a first etching solution and an etchant chemistry utilized in the first etching solution includes anions as the primary reactive species, the etch rate of the material formed in the first feature and the second feature increases. In this case, the increase in etch rate may be more pronounced in the first feature having a smaller CD and less pronounced in the second feature having a larger CD. When a substrate is exposed to a second etching solution and an etchant chemistry utilized in the second etching solution includes anions as the primary reactive species, the etch rate of the material formed in the first feature and the second feature decreases. In this case, the decrease in etch rate may be more pronounced in the first feature having a smaller CD and less pronounced in the second feature having a larger CD.

[0016] In other embodiments, the etchant chemistry may include cations instead of anions as the primary reactive species. When cations are utilized as the primary reactive species, exposing the substrate to a first etching solution etches the material formed in the first feature slower than the material formed in the second feature, while exposing the substrate to a second etching solution etches the material formed in the first feature faster than the material forming the second feature. Thus, exposing the substrate to the first etching solution and then exposing the substrate to the second etching solution etches the material formed in the first feature and the material formed in the second feature at a uniform etch rate.

[0017] When a substrate is exposed to a first etching solution and an etchant chemistry utilized in the first etching solution includes cations as the primary reactive species, the etch rate of the material formed in the first feature and the second feature decreases. In this case, the decrease in etch rate may be more pronounced in the first feature having a smaller CD and less pronounced in the second feature having a larger CD. When a substrate is exposed to a second etching solution and an etchant chemistry utilized in the second etching solution includes cations as the primary reactive species, the etch rate of the material formed in the first feature and the second feature increases. In this case, the increase in etch rate may be more pronounced in the first feature having a smaller CD and less pronounced in the second feature having a larger CD.

[0018] In some embodiments of the described methods, the substrate may be sequentially exposed to one or more etching solutions. In some embodiments, for example, exposing the substrate to one or more etching solutions may include exposing the substrate to a first etching solution for a first period of time, followed by exposing the substrate to a second etching solution for a second period of time that occurs at least partially after the first period of time. In other embodiments, exposing the substrate to one or more etching solutions may include exposing the substrate to a second etching solution for a first period of time, followed by exposing the substrate to the first etching solution for a second period of time that occurs at least partially after the first period of time.

[0019] In other embodiments of the methods described herein, the substrate can be exposed to one or more etching solutions concurrently. In some embodiments, for example, exposing the substrate to one or more etching solutions can include exposing the substrate to a first etching solution and exposing the substrate to a second etching solution substantially simultaneously or during overlapping periods. In other embodiments, exposing the substrate to one or more etching solutions can include exposing the substrate to a single etching solution comprising an etchant chemical, an aqueous solvent, and an organic solvent, whereby the materials in the first feature and the second feature are etched at a uniform etch rate.

[0020] According to another embodiment, another method of etching is provided that utilizes the techniques described in this disclosure. In some embodiments, the method may begin by providing a substrate having a plurality of features, the plurality of features having critical dimensions (CDs) that vary with respect to one or more of the features, such that the plurality of features includes at least a first feature having a smaller CD and a second feature having a larger CD.

[0021] The method may then include sequentially exposing the substrate to a first etching solution and a second etching solution to etch material formed within the plurality of features. The first etching solution includes an etchant chemical mixed with an organic solvent. The second etching solution includes an etchant chemical mixed with an aqueous solvent. By sequentially exposing the substrate to the first etching solution and the second etching solution, the methods described herein provide uniform etching of material formed within the plurality of features, regardless of CD.

[0022] In some embodiments, sequentially exposing the substrate to a first etching solution and a second etching solution can include exposing the substrate to the first etching solution for a first period of time, followed by exposing the substrate to the second etching solution for a second period of time that occurs at least partially after the first period of time. By exposing the substrate to the first etching solution, the material formed in the first feature is etched faster than the material formed in the second feature. When the substrate is subsequently exposed to the second etching solution, the second etching solution etches the material formed in the first feature slower than the material forming the second feature. Thus, the methods described herein etch the material formed in the first feature and the material formed in the second feature at a uniform etch rate by exposing the substrate to the first etching solution and subsequently exposing the substrate to the second etching solution.

[0023] In other embodiments, sequentially exposing the substrate to a first etching solution and a second etching solution can include exposing the substrate to the second etching solution for a first period of time, followed by exposing the substrate to the first etching solution for a second period of time that occurs at least partially after the first period of time. By exposing the substrate to the second etching solution, the material formed in the first feature is etched slower than the material forming the second feature. However, by exposing the substrate to the first etching solution, the material formed in the first feature is etched faster than the material formed in the second feature. Thus, the methods described herein etch the material formed in the first feature and the material formed in the second feature at a uniform etch rate by exposing the substrate to the second etching solution followed by exposing the substrate to the first etching solution.

[0024] In some embodiments, the methods described herein may further include providing a time delay between the first time period and the second time period to prevent mixing of the first etching solution and the second etching solution on the surface of the substrate. In other embodiments, the second time period may overlap with the first time period, resulting in mixing between the first etching solution and the second etching solution on the surface of the substrate.

[0025] A wide variety of etchant chemicals may be used in the first and second etching solutions. In some embodiments, the etchant chemicals may include one or more of hydrofluoric acid (HF), ammonium hydroxide (NH4OH), hydrochloric acid (HCl), hydrogen peroxide (HO), nitric acid (HNO3), phosphoric acid (H3PO4), potassium hydroxide (KOH), tetramethylammonium hydroxide (TMAH), and other etchant chemicals that contain anions (negatively charged ions) as the primary reactive species. In other embodiments, the etchant chemicals utilized in the first and second etching solutions may contain cations (positively charged ions) as the primary reactive species.

[0026] A wide variety of organic solvents can also be used in the first etching solution. Examples of organic solvents that can be included in the first etching solution include methanol (CHO), ethanol (CHO), isopropyl alcohol (CHO), benzyl alcohol (CHO), ethylene glycol (CHO), acetic acid (CHCOOH), acetone (CHO), propylene carbonate (CHO), n-hexane (CHO), and the like. 14 ), cyclohexane (CH 12 ), diethyl ether (C4H 10 O), tetrahydrofuran (C4H8O), benzene (C6H6), toluene (C7H8), dichloromethane (CH2Cl2), trichloroethylene (C2HCl3), 1,1,1-trichloroethane (C2H3Cl3), 1,2-dichloroethane (C2H4Cl2), N-methyl-2-pyrrolidone (C5H9NO), dimethyl sulfoxide (C2H6OS), ethyl lactate (C5H 10 O3), ethanolamine (C2H7NO), and propylene glycol methyl ether acetate (C6H 12 In some embodiments, the organic solvent included in the first etching solution can be isopropyl alcohol (C3H8O), propylene carbonate (C4H6O3), acetic acid (CH3COOH), or ethylene glycol (C2H6O2).

[0027] A more complete understanding of the present invention and its advantages will be obtained by referring to the following description in conjunction with the accompanying drawings, in which like reference numerals indicate like features, and in which it should be noted, however, that the accompanying drawings illustrate only exemplary embodiments of the disclosed concepts and are not intended to limit the scope of the present invention, as the disclosed concepts may encompass other embodiments that are equally effective. [Brief explanation of the drawings]

[0028] [Figure 1A]1 is a cross-sectional view through a substrate having features of different critical dimensions (CDs) illustrating CD-dependent etching of material within the features when the substrate is exposed to a non-aqueous organic-based etching solution. [Figure 1B] 1 is a cross-sectional view through a substrate having features of different critical dimensions (CDs) illustrating CD-dependent etching of material within the features when the substrate is exposed to an aqueous-based etching solution. [Figure 2] 1 is a graph showing normalized etch rate versus feature CD when a substrate is exposed to a non-aqueous organic-based etch solution and an aqueous-based etch solution. [Figure 3] FIG. 1 is a schematic diagram illustrating the zeta potential and the electric double layer (EDL) that exists between the charged wall surface and the etching solution. [Figure 4] 1 is a graph showing zeta potential versus pH for various wall materials. [Figure 5] 1 is a graph showing zeta potential versus pH for various etching solutions and wall materials. [Figures 6A-6D] FIG. 1 illustrates one embodiment of a wet etching process that can be used to provide uniform etch rates within features having different CDs by sequentially exposing a substrate having features formed thereon to aqueous-based and non-aqueous organic-based etching solutions. [Figures 7A-7D] FIG. 1 illustrates another embodiment of a wet etching process that can be used to provide uniform etch rates within features having different CDs by sequentially exposing a substrate having features formed thereon to aqueous-based and non-aqueous organic-based etching solutions. [Figure 8] FIG. 7B is a graph showing normalized etch rate versus trench CD (expressed in nm) when using a non-aqueous organic-based etchant solution and an aqueous-based etchant solution sequentially as shown in FIGS. 7A-7D to etch silicon dioxide (SiO) material formed in trenches of various CDs. [Figure 9]FIG. 1 is a cross-sectional view through a substrate having a silicon dioxide (SiO 2 ) nanoslit sandwiched between and formed adjacent to wall material (e.g., a-Si). [Figure 10] 10 is a graph showing normalized SiO etch rate (ER) versus SiO thickness (or CD, expressed in nm) when a non-aqueous organic-based etchant and an aqueous-based etchant are used sequentially to etch the SiO nanoslit shown in FIG. [Figures 11A-11C]

[0023] An embodiment of a wet etching process that can be used to provide uniform etch rates within features (e.g., trenches or holes) having different CDs is shown by exposing a substrate with the features formed thereon to a single etching solution that includes one or more etchant chemicals, an aqueous solvent, and an organic solvent. [Figure 12] 11A-11C are graphs showing normalized etch rate versus trench CD (expressed in nm) when a single etching solution having one or more etchant chemicals, an aqueous solvent, and an organic solvent is used to etch silicon dioxide (SiO) material formed in trenches of various CDs when the SiO material is adjacent to a SiCN wall material. [Figure 13] FIG. 1 is a flow chart diagram illustrating one embodiment of an etching method utilizing techniques described herein. [Figure 14] FIG. 10 is a flow chart diagram illustrating another embodiment of an etching method utilizing techniques described herein. DETAILED DESCRIPTION OF THE INVENTION

[0029] This disclosure provides various embodiments of wet etching processes and methods for providing uniform etching of materials formed within features (e.g., trenches, holes, slits, etc.) having different critical dimensions (CDs). When an etching solution is used to remove material within the features, the rate at which material is removed from one or more of the features (i.e., the etch rate) can vary depending on various factors, such as the CD of the feature, the etchant chemistry used in the etching solution, the solvent used in the etching solution, the ratio of the etchant chemistry to the solvent used in the etching solution, the pH of the etching solution, and the wall material adjacent to the material being etched. The difference in etch rate across features of different CDs is known in the art as CD-dependent etching.

[0030] Embodiments described in the present disclosure provide for uniform etching of materials formed within features of different CDs by exposing a substrate comprising the features to an aqueous-based etching solution and a non-aqueous organic-based etching solution, either sequentially or in parallel. An aqueous-based etching solution is a solution comprising one or more etchant chemicals and an aqueous solvent. In contrast, a non-aqueous organic-based etching solution comprises one or more etchant chemicals and an organic solvent. In some embodiments, the wet etching processes and methods disclosed herein may provide for uniform etching of materials within features of different CDs by exposing the substrate to a single etching solution comprising one or more etchant chemicals, an aqueous solvent, and an organic solvent, instead of exposing the substrate to an aqueous-based etching solution and a non-aqueous organic-based etching solution (either sequentially or in parallel).

[0031] 1A-1B and 2 illustrate CD-dependent etching of materials deposited within features having different CDs and across planar regions of a substrate when the substrate is exposed to a non-aqueous organic-based etching solution 130 (FIGS. 1A and 2) and an aqueous-based etching solution 140 (FIGS. 1B and 2). As used herein, an aqueous-based etching solution 140 is a solution that includes one or more etchant chemicals mixed with an aqueous solvent (e.g., water (HO) or deionized water). In contrast, a non-aqueous organic-based etching solution 130 is a solution that includes one or more etchant chemicals mixed with an organic solvent. In some embodiments, the non-aqueous organic-based etching solution 130 may include a water-containing etchant chemical (e.g., hydrofluoric acid (HF) containing, by weight, e.g., 49% HF and 51% water, or ammonium hydroxide (NHOH) containing, by weight, e.g., 29% NHOH and 71% water) and thus may include a minimal amount of water.

[0032] 1A-1B illustrates a substrate 100 having a plurality of structures 105 (e.g., metal lines, fins, etc.) extending above the surface of the substrate. Each of the plurality of structures 105 is separated by a feature 115 (e.g., a gap, trench, hole, etc.). The critical dimensions (CDs) of the features 115 may be the same or different, as illustrated in FIGS. 1A-1B. In the exemplary embodiment illustrated in FIGS. 1A-1B, the substrate 100 is shown as having a first feature 115a having a smaller CD (CD1) and a second feature 115b having a larger CD (CD2). The CDs of the plurality of features 115 are relatively small (e.g., less than 100 nm) compared to a planar region 120 of the substrate 100 that surrounds the plurality of structures 105.

[0033] A material 125 to be etched is deposited on the surface of the substrate 100, on the plurality of structures 105, and within the features 115 formed between the plurality of structures 105. The material 125 may include a wide variety of semiconductor materials. For example, the material 125 may be an oxide, a dielectric material, silicon, or a metal. In one example, the material 125 may be a silicon oxide (e.g., silicon dioxide, SiO2, etc.). Other oxides and dielectric materials, including low-k dielectric materials, may also be formed and etched within the plurality of features 105.

[0034] 1A, the substrate 100 is exposed to a non-aqueous organic-based etching solution 130 that includes one or more etchant chemicals and an organic solvent. Examples of etchants that may be included in the non-aqueous organic-based etching solution 130 include, but are not limited to, hydrofluoric acid (HF), ammonium hydroxide (NH4OH), hydrochloric acid (HCl), hydrogen peroxide (HO2), nitric acid (HNO3), phosphoric acid (H3PO4), potassium hydroxide (KOH), tetramethylammonium hydroxide (TMAH), and other etchant chemicals that contain anions (negatively charged ions) as the primary reactive species.

[0035] A wide variety of organic solvents can be used in the non-aqueous organic-based etching solution 130 described herein. Examples of organic solvents that can be included in the non-aqueous organic-based etching solution 130 include various alcohols (e.g., methanol (CHO), ethanol (CHO), isopropyl alcohol (CHO), benzyl alcohol (CHO), etc.), polyhydric alcohols (e.g., ethylene glycol (CHO)), acetic acid (CHCOOH), ketones (e.g., acetone (CHO), propylene carbonate (CHO), etc.), and the like. 14 O3), alkanes (e.g., n-hexane (C6H 14 ), cyclohexane (CH 12 ), ethers (e.g., diethyl ether (CH 10O), tetrahydrofuran (C4H8O), etc.), aromatic hydrocarbons (e.g., benzene (C6H6), toluene (C7H8), etc.), halogen compounds (e.g., dichloromethane (CH2Cl2), trichloroethylene (C2HCl3), 1,1,1-trichloroethane (C2H3Cl3), 1,2-dichloroethane (C2H4Cl2), etc.), nitrogen compounds (e.g., N-methyl-2-pyrrolidone (C5H9NO), etc.), sulfuric acid compounds (e.g., dimethyl sulfoxide (C2H6OS), etc.), and ethyl lactate (C5H 10 O3), ethanolamine (C2H7NO) and propylene glycol methyl ether acetate (C6H 12 Other volatile carbon-based solvents such as, but not limited to, HCl, HCl, HClO ...

[0036] In some embodiments, the non-aqueous organic-based etching solution 130 may include an etchant chemical containing anions as the primary reactive species (e.g., hydrofluoric acid, ammonium hydroxide, or hydrochloric acid) mixed with an alcohol (e.g., isopropyl alcohol, IPA), a polyhydric alcohol (e.g., ethylene glycol, EG), acetic acid, AA, or a ketone (e.g., propylene carbonate, PC). In at least one preferred embodiment, the non-aqueous organic-based etching solution 130 may include hydrofluoric acid mixed with IPA, AA, EG, or PC. Other organic solvents described herein may also be mixed with hydrofluoric acid or other etchant chemicals containing anions as the primary reactive species (such as NH4OH or HCl). The etchant chemicals described herein may be mixed with many different organic solvents, although the compatibility and solubility of the etchant chemical with the organic solvent must be carefully considered.

[0037] When substrate 100 is exposed to a non-aqueous organic-based etching solution 130 containing anions as the primary reactive species, the portion of feature 115 exposed to non-aqueous organic-based etching solution 130 may exhibit a positive surface potential, as shown in Figure 1A, depending on the pH of the etching solution and the wall material 110 used to form feature 115. For example, when substrate 100 is exposed to a non-aqueous organic-based etching solution 130 containing hydrofluoric acid mixed with an organic solvent (e.g., IPA, AA, EG, or PC), the exposed portion of feature 115 may exhibit a positive surface potential (as shown in Figure 1A), and the wall material 110 comprises a silicon-containing material such as amorphous silicon (a-Si), polysilicon (poly-Si), silicon nitride (SiN), silicon carbonitride (SiCN), or silicon oxynitride (SiON).

[0038] As shown in FIG. 1A and described above, when substrate 100 is exposed to non-aqueous, organic-based etching solution 130, anions in the etchant chemical are attracted to the positively charged surface. This increases the local concentration of anions within feature 115, which in turn increases the etch rate of material 125 deposited within feature 115 compared to flatter regions 120 of substrate 100. Thus, material 125 etches faster within features 115 and slower within flatter regions 120 of substrate 100 surrounding structures 105. This is shown schematically in FIG. 1A and in graph 200 shown in FIG. 2. When features 115 of different CDs are formed within structures 105, as shown in FIG. 1A, the increase in etch rate is more pronounced within features with smaller CDs (e.g., feature 115a) and less pronounced within features with larger CDs (e.g., feature 115b). However, the etch rate within feature 115 is significantly faster than the etch rate achieved over the flatter regions 120 of substrate 100 .

[0039] 1B, the substrate 100 is exposed to an aqueous-based etching solution 140, which includes one or more etchant chemicals and an aqueous solvent. As described above, the aqueous-based etching solution 140 is a solution including etchant chemicals mixed with an aqueous solvent (e.g., water (H2O) or deionized water). Examples of etchant chemicals that may be included in the aqueous-based etching solution 140 include, but are not limited to, hydrofluoric acid (HF), ammonium hydroxide (NH4OH), hydrochloric acid (HCl), hydrogen peroxide (H2O2), nitric acid (HNO3), phosphoric acid (H3PO4), potassium hydroxide (KOH), tetramethylammonium hydroxide (TMAH), and other etchant chemicals that contain anions (negatively charged ions) as the primary reactive species.

[0040] When substrate 100 is exposed to an aqueous-based etching solution 140 containing anions as the primary reactive species, the portion of feature 115 exposed to the aqueous-based etching solution 140 may exhibit a negative surface potential, as shown in FIG. 1B, depending on the pH of the etching solution and the wall material 110 used to form feature 115. For example, when substrate 100 is exposed to an aqueous-based etching solution 140 containing hydrofluoric acid mixed with water, the exposed portion of feature 115 may exhibit a positive surface potential (as shown in FIG. 1B), and the wall material 110 includes a silicon-containing material such as amorphous silicon (a-Si), polysilicon (poly-Si), silicon carbonitride (SiCN), or silicon oxynitride (SiON). However, when substrate 100 is exposed to an aqueous-based etching solution 140 containing hydrofluoric acid mixed with water, other silicon-containing materials, such as silicon nitride (SiN), may exhibit a positive surface potential (not shown in FIG. 1B). This is illustrated in FIG. 5 and described in more detail below.

[0041] As shown in FIG. 1B and described above, when substrate 100 is exposed to aqueous-based etching solution 140, the negative surface potential of wall material 110 repels anions in the etchant chemical, reducing their local concentration within feature 115 and therefore reducing the etch rate of material 125 deposited within feature 115. When features 115 of different CDs are formed within a plurality of structures 105, as shown in FIG. 1B, the reduction in etch rate is more pronounced within features with smaller CDs (e.g., feature 115a) and less pronounced within features with larger CDs (e.g., feature 115b). As a result, material 125 etches slower in features with smaller CDs (e.g., feature 105a) and faster in features with larger CDs (e.g., feature 105b). As shown in FIG. 1B, the etch rate across flatter regions 120 of the substrate is significantly faster than the etch rate within feature 115.

[0042] When etching material 125 formed in multiple features 115, the etch rate of material 125 may depend on various factors, including the critical dimension (CD) of feature 115, the particular etchant chemical and / or reactive species used in the etching solution, the particular solvent used in the etching solution, the ratio of etchant chemical to solvent used in the etching solution, and / or the pH of the etching solution. In addition to these factors, depending on the etching solution used, the electrical potential of wall material 110 adjacent to the material 125 being etched may also affect the etch rate of material 125.

[0043] 1A-1B and 2, non-aqueous organic-based etching solution 130 and aqueous-based etching solution 140 can sometimes have opposite effects on etch rate. When non-aqueous organic-based etching solution 130 is used to etch material 125, the etch rate increases in features with smaller CDs (such as feature 115a) and decreases in features with larger CDs (such as feature 115b). However, the opposite is true when aqueous-based etching solution 140 is used to etch material 125. This may be due, at least in part, to the zeta potential and the electrical double layer (EDL) that exists between wall material 110 and the etching solution.

[0044] Figure 3 is a schematic diagram illustrating the zeta potential and the electric double layer that exists between the wall material and the etching solution. The etching solution contains cations (positively charged ions) and anions (negatively charged ions). As shown in Figure 3, when the etching solution contacts a wall material with a negative surface potential, the cations in the etching solution are attracted to the wall material by electrostatic and / or van der Waals forces and adsorbed onto the wall material. The opposite is true when the etching solution contacts a wall material with a positive surface potential (i.e., the anions in the etching solution are attracted to the wall material and adsorbed onto the wall material). This attractive force creates an electric double layer (i.e., a layer that is not electrically neutral) between the wall material and the etching solution.

[0045] According to the Stern model, the electric double layer (EDL) is divided into two parts separated by a plane called the Stern plane. The centers of adsorbed ions are located within the Stern layer between the wall and the Stern plane. Ions with centers beyond the Stern plane form a diffuse layer of the EDL. As shown in Figure 3, the potential (Ψ) near the wall is divided into Ψ and Ψ δ (potential at the Stern plane), and within the diffusion layer and beyond, Ψ δThe zeta potential (ζ) is the potential that exists at the shear plane between the charged wall and the etching solution. The zeta potential (ζ) can be positive, zero, or negative, depending on the wall material and the pH of the etching solution.

[0046] FIG. 4 shows a graph 400 illustrating zeta potential (expressed in mV) versus pH for various wall materials. As shown in FIG. 4, zeta potential generally increases with decreasing pH and decreases with increasing pH. In some embodiments, the zeta potential between the charged wall surface and the etching solution can be changed by changing the pH of the etching solution (e.g., by changing the etchant chemicals used in the etching solution or by adding an acid or base to the etching solution), as shown in FIG. 4. In other embodiments, the zeta potential between the charged wall surface and the etching solution can be changed by adding a surfactant to the etching solution. In yet another embodiment, the zeta potential between the charged wall surface and the etching solution can be changed by utilizing an organic solvent instead of an aqueous solvent in the etching solution (depending on the pH of the etching solution). This is illustrated in graph 500 shown in FIG. 5.

[0047] Graph 500 shown in FIG. 5 illustrates the zeta potential versus pH for various etching solutions and wall materials (e.g., SiN, a-Si, and SiCN). When hydrofluoric acid (HF) is mixed with an aqueous solvent and used as the etching solution, the zeta potential (denoted by Δ) between the etching solution and the wall material is (a) negative for a-Si and SiCN (resulting in a negatively charged wall surface), and (b) positive for SiN (resulting in a positively charged wall surface). When hydrofluoric acid is mixed with an organic solvent instead of an aqueous solvent, the zeta potential (denoted by ●) is positive for a-Si, SiCN, and SiN (resulting in a positively charged wall surface). Graph 500 shown in FIG. 5 illustrates that while the organic solvent has little or no effect on the zeta potential between the etching solution and the already positively charged wall surface, the zeta potential between the etching solution and the negatively charged wall surface can (sometimes) be changed to a positive surface potential by using an organic solvent instead of an aqueous solvent in the etching solution. This difference in zeta potential may at least partially explain the opposing effects that aqueous-based etching solutions and non-aqueous organic-based solutions have on etch rates when etching features with different CDs.

[0048] In graph 500 shown in FIG. 5, an organic solvent is utilized in an HF etching solution to change the zeta potential of negatively charged a-Si or SiCN wall surfaces to a positive surface potential. However, the use of an organic solvent may not be sufficient to shift the zeta potential from a negative surface potential to a positive surface potential for all wall surfaces. In some cases, the pH of the organic etching solution can be adjusted (e.g., by changing the etchant chemistry used in the etching solution or by adding an acid or base to the etching solution) to further adjust the zeta potential and thereby achieve a positive surface potential and the desired CD-dependent etching results. If the pH cannot be changed (e.g., due to compatibility concerns), a surfactant can be added to the organic etching solution to adjust the zeta potential and achieve the desired CD-dependent etching results. In some cases, all three methods (organic solvents, pH adjustment, and surfactant addition) can be used to provide or enhance the CD-dependent trend.

[0049] In the discussion above, organic-based etching solutions (with or without pH adjustment and surfactant addition) are used to increase the etch rate of materials formed in features with smaller CDs when (a) the organic-based etching solution contains anions as the primary reactive species and (b) the material being etched is adjacent to a wall material that exhibits a negative surface potential in aqueous solution. However, organic-based etching solutions may not provide the desired CD-dependent etching results in all embodiments. In some embodiments, when cations are used as the primary reactive species, aqueous-based etching solutions may be used to increase the etch rate of materials formed in features with smaller CDs. In some embodiments, the pH may be adjusted and / or a surfactant may be added to aqueous-based etching solutions containing cations as the primary reactive species to produce the desired CD-dependent etching results.

[0050] As described herein, one mechanism that can cause etch rate variations when using different etching solutions, different wall materials, and different CDs is a mechanism related to surface potential. However, the techniques described herein are not strictly limited to such techniques. Thus, the CD-dependent etch rates described herein may be achieved by other mechanisms, and the etch rate advantages described and obtained by the techniques provided herein are not limited to a particular surface potential mechanism. Rather, other mechanisms can also be utilized to advantage.

[0051] The present disclosure takes advantage of the difference in etch rates that occurs when non-aqueous organic-based and aqueous-based etching solutions are used to etch materials formed in features with different CDs (e.g., trenches, holes, slits, etc.). The disclosed embodiments utilize the opposing effects of CD-dependent etching by combining non-aqueous organic-based and aqueous-based etching solutions (either sequentially or in parallel) in a wet etching process to provide uniform etching of materials regardless of CD. In some embodiments, the etchant chemistry used in the etching solution, the ratio of etchant chemistry to solvent used in the etching solution, and / or the pH of the etching solution may also be selected or controlled to provide uniform etching of materials formed in features of various CDs.

[0052] 6A-6D illustrate one embodiment of a wet etching process 600 that can be used to provide uniform etch rates within features having different CDs by sequentially exposing a substrate having features formed thereon to aqueous-based and non-aqueous, organic-based etching solutions. In some embodiments, the wet etching process 600 illustrated in FIGS. 6A-6D can be performed on a substrate having trenches or holes with different CDs, such as the substrate 100 illustrated in FIGS. 1A and 1B.

[0053] As shown in FIG. 6A , a wet etching process 600 may generally begin by providing (at step 610) a substrate 100 having a plurality of features 115 (e.g., trenches or holes), one or more of the features 115 having different CDs. Next, the wet etching process 600 may expose the substrate 100 to an aqueous-based etching solution 140 (at step 620 of FIG. 6B ), followed by exposing the substrate to a non-aqueous organic-based etching solution 130 (at step 630 of FIG. 6C ). In some embodiments, the wet etching process 600 may expose the substrate 100 to the aqueous-based etching solution 140 for a first period of time (at step 620), followed by exposing the substrate to the non-aqueous organic-based etching solution 130 for a second period of time that occurs at least partially after the first period of time (at step 630), to provide a desired amount of etching during each step.

[0054] As described above, when etching features 115 with different CDs, aqueous-based and non-aqueous organic-based solutions can have opposite effects on etch rates. When substrate 100 is exposed to aqueous-based etch solution 140 (step 620), features with smaller CDs (e.g., feature 115a) etch slower than features with larger CDs (e.g., feature 115b). Subsequently, when substrate 100 is exposed to non-aqueous organic-based etch solution 130 (step 630), features with smaller CDs (e.g., feature 115a) etch faster than features with larger CDs (e.g., feature 115b). By sequentially exposing substrate 100 to aqueous-based etch solution 140 and non-aqueous organic-based etch solution 130 as shown in FIGS. 6B-6C, wet etching process 600 provides uniform etch rates and uniform etching of material 125 formed within feature 115, as shown in step 640 of FIG. 6D.

[0055] In the embodiment shown in FIGS. 6A-6D , the wet etching process 600 exposes the substrate 100 to the aqueous-based etching solution 140 for a first period of time (at step 620) and then exposes the substrate 100 to the non-aqueous organic-based etching solution 130 for a second period of time that occurs at least partially after the first period of time (at step 630). In some embodiments, a time delay (or drying step) may be provided between the first and second periods of time to prevent mixing of the aqueous-based etching solution 140 and the non-aqueous organic-based etching solution 130 on the surface of the substrate 100. In other embodiments, the second period of time may partially overlap with the first period of time, resulting in mixing between the aqueous-based etching solution 140 and the non-aqueous organic-based etching solution 130 on the surface of the substrate. In still other embodiments, the substrate 100 may be exposed to the non-aqueous organic-based etching solution 130 before being exposed to the aqueous-based etching solution 140, as shown, for example, in FIGS. 7A-7D .

[0056] 7A-7D illustrate another embodiment of a wet etching process 700 that can be used to provide uniform etch rates within features having different CDs by sequentially exposing a substrate having features formed thereon to an aqueous-based etching solution and a non-aqueous organic-based etching solution. Similar to the previous embodiment illustrated in FIGS. 6A-6D, the wet etching process 700 illustrated in FIGS. 7A-7D is performed on a substrate having trenches or holes with different CDs, such as the substrate 100 illustrated in FIGS. 1A and 1B. However, unlike the previous embodiment illustrated in FIGS. 6A-6D, the wet etching process 700 illustrated in FIGS. 7A-7D exposes the substrate 100 to a non-aqueous organic-based etching solution 130 before exposing the substrate 100 to an aqueous-based etching solution 140.

[0057] As shown in FIG. 7A, a wet etching process 700 may generally begin by providing (at step 710) a substrate 100 having a plurality of features 115 (e.g., trenches or holes), one or more of the features 115 having different CDs. Next, the wet etching process 700 may expose the substrate 100 to a non-aqueous organic-based etching solution 130 (at step 720 of FIG. 7B), followed by subsequent exposure of the substrate 100 to an aqueous-based etching solution 140 (at step 730 of FIG. 7C). The wet etching process 700 may expose the substrate 100 to the non-aqueous organic-based etching solution 130 for a first period of time (at step 720), followed by subsequent exposure of the substrate 100 to the aqueous-based etching solution 140 for a second period of time that occurs at least partially after the first period of time (at step 730), to provide a desired amount of etching during each step.

[0058] When substrate 100 is exposed (at step 720) to non-aqueous organic-based etching solution 130, features with smaller CDs (such as feature 115a) etch faster than features with larger CDs (such as feature 115b). Subsequently, when substrate 100 is exposed (at step 730) to aqueous-based etching solution 140, features with smaller CDs (such as feature 115a) etch slower than features with larger CDs (such as feature 115b). By sequentially exposing substrate 100 to non-aqueous organic-based etching solution 130 and aqueous-based etching solution 140 as shown in Figures 7B-7C, wet etching process 700 provides a uniform etch rate and uniform etching of material 125 formed within feature 115, as shown in step 740 of Figure 7D.

[0059] 7A-7D , the wet etching process 700 exposes the substrate 100 to the non-aqueous organic-based etching solution 130 for a first period of time (at step 720), followed by exposing the substrate 100 to the aqueous-based etching solution 140 for a second period of time that occurs at least partially after the first period of time (at step 730). In some embodiments, a time delay (or drying step) may be provided between the first and second periods of time to prevent mixing of the non-aqueous organic-based etching solution 130 and the aqueous-based etching solution 140 on the surface of the substrate 100. In other embodiments, the second period of time may partially overlap with the first period of time, resulting in mixing between the non-aqueous organic-based etching solution 130 and the aqueous-based etching solution 140 on the surface of the substrate.

[0060] Graph 800 shown in FIG. 8 illustrates normalized etch rate versus trench CD (expressed in nm) when an etching solution having an organic solvent (e.g., non-aqueous organic etching solution 130) and an etching solution having an aqueous solvent (e.g., aqueous etching solution 140) are sequentially used to etch silicon dioxide (SiO) materials formed in trenches of various CDs, as shown in FIGS. 7A-7D. In graph 800, the "normalized etch rate" is the ratio of the etch rate in the trench having the smaller CD to the etch rate in the trench having the larger CD. As shown in graph 800, the normalized etch rate increases with decreasing CD when using an etching solution having an organic solvent and decreases with decreasing CD when using an etching solution having an aqueous solvent. By exposing the substrate to an etching solution having an organic solvent followed by an etching solution having an aqueous solvent, the wet etching process 700 shown in FIGS. 7A-7D provides a uniform etch rate (e.g., a normalized etch rate close to "1") within trenches of various CDs.

[0061] In the exemplary embodiments shown in FIGS. 1A-1B, 6A-6D, and 7A-7D, the etchant chemicals utilized in the non-aqueous organic-based etching solution 130 and the aqueous-based etching solution 140 include anions (negatively charged ions) as the primary reactive species. In an alternative embodiment (not shown) of the present disclosure, the etchant chemicals utilized in the non-aqueous organic-based etching solution 130 and the aqueous-based etching solution 140 may contain cations (positively charged ions) as the primary reactive species. When cations are used as the primary reactive species, the non-aqueous organic-based etching solution 130 and the aqueous-based etching solution 140 may provide etching effects opposite to those shown in FIGS. 1A-1B, 6A-6D, and 7A-7D. For example, when cations are used as the primary reactive species, non-aqueous organic-based etching solution 130 may etch material 125 more slowly in features with smaller CDs (such as feature 115a) and more quickly in features with larger CDs (such as feature 115b). Similarly, when cations are used as the primary reactive species, aqueous-based etching solution 140 may etch material 125 more quickly in features with smaller CDs (such as feature 115a) and more slowly in features with larger CDs (such as feature 115b).

[0062] In the exemplary embodiments shown in Figures 1A-1B, 6A-6D, and 7A-7D, the techniques described herein are used to provide uniform etching of materials formed in trenches or holes of various CDs. However, it will be appreciated that the techniques described herein are not strictly limited to etching materials formed in trenches or holes, but instead may be implemented on any substrate having features of various CDs.

[0063] For example, the techniques described herein can also be used to provide uniform etching of materials formed within nanoslits of various thicknesses, as shown in Figures 9 and 10. Figure 9 provides a cross-sectional view through a substrate 900 having a nanoslit 910 formed adjacent to and sandwiched between wall materials 920 (e.g., a-Si, poly-Si, SiCN, or SiON, etc.). In one embodiment, the nanoslit 910 may comprise silicon dioxide (SiO2), and the wall material 920 may comprise amorphous silicon (a-Si). In some embodiments, the thickness or critical dimension (CD) of the nanoslit 910 may be in the range of, for example, 5 nm to 55 nm.

[0064] Graph 1000 shown in Figure 10 illustrates the normalized SiO2 etch rate (ER) versus SiO2 thickness (or CD, expressed in nm) when an etching solution having an organic solvent (e.g., non-aqueous organic-based etching solution 130) and an etching solution having an aqueous solvent (e.g., aqueous-based etching solution 140) are sequentially used to etch SiO2 nanoslits 910 of various CDs, as shown in Figure 9. Graph 1000 shows that the normalized SiO2 etch rate increases with decreasing CD when using an etching solution having an organic solvent (e.g., hydrofluoric acid (HF) mixed with ethylene glycol (EG) in a 1:5 ratio) and decreases with decreasing CD when using an etching solution having an aqueous solvent (e.g., a dilute HF solution formed by mixing HF and water in a 1:100 ratio). However, when the substrate 900 is sequentially exposed to a HG:EG solution (1:5) followed by a dilute HF solution (1:100), uniform etch rates (e.g., normalized etch rates close to "1") are provided within the SiO2 nanoslits of various CDs.

[0065] 9-10, when the SiO2 nanoslits 910 are etched using the non-aqueous organic etching solution 130 and the aqueous etching solution 140 sequentially, the absolute etching rate of the SiO2 nanoslits 910 when exposed to the aqueous etching solution 140 is much higher than when the SiO2 nanoslits 910 are exposed to the non-aqueous organic etching solution 130 at the same chemical concentration. A higher chemical concentration is used in the non-aqueous organic etching solution 130 to provide equivalent process times for the first and second periods in the processing sequence.

[0066] The wet etching processes described thus far have sequentially exposed a substrate to aqueous-based and non-aqueous organic-based etching solutions to provide uniform etching of materials within features of various CDs. However, it will be appreciated that the techniques described herein are not strictly limited to wet etching processes that sequentially expose a substrate to aqueous-based and non-aqueous organic-based etching solutions. In an alternative embodiment, a wet etching process according to the present disclosure may expose a substrate to aqueous-based and non-aqueous organic-based etching solutions in parallel, such that the aqueous-based and non-aqueous organic-based etching solutions are delivered to the substrate substantially simultaneously or during overlapping periods. In another alternative embodiment, a wet etching process according to the present disclosure may expose a substrate to a single etching solution that includes one or more etchant chemicals, an aqueous solvent, and an organic solvent.

[0067] 11A-11C illustrate one embodiment of a wet etching process 1100 that can be used to provide uniform etch rates within features having different CDs by exposing a substrate having features formed thereon to a single etching solution that includes one or more etchant chemistries, an aqueous solvent, and an organic solvent. The wet etching process 1100 illustrated in FIGS. 11A-11C is performed on a substrate 100 having trenches or holes with different CDs, such as the substrate 100 illustrated in FIGS. 1A and 1B. Although so illustrated, the wet etching process 1100 is not strictly limited to etching material formed within trenches or holes, but instead can be performed on any substrate having features of varying CDs.

[0068] 6A-6D and 7A-7D, the wet etching process 1100 shown in Figures 11A-11C may generally begin by providing (at step 1110 of Figure 11A) a substrate 100 having multiple features 115 (e.g., trenches or holes), one or more of the features 115 having different CDs. The wet etching process 1100 may then expose (at step 1120 of Figure 11B) the substrate 100 to a single etching solution 1125 that includes one or more etchant chemicals, an aqueous solvent, and an organic solvent. By combining etchant chemistries with aqueous solvents (which provide slower etch rates for features with smaller CDs and faster etch rates for features with larger CDs) and organic solvents (which provide faster etch rates for features with smaller CDs and slower etch rates for features with larger CDs), the wet etching process 1100 provides a uniform etch rate and uniform etching of the material 125 formed within the feature 115, as shown in step 1130 of FIG. 11C.

[0069] When combining organic solvents with aqueous solvents, the compatibility and solubility of the organic solvent and aqueous solvent must be considered. For example, some organic solvents are immiscible with water. Some organic solvents can be mixed with water at any concentration. Other organic solvents can be mixed with water up to a certain concentration (e.g., X%), beyond which the organic solvent is no longer water-soluble. While various organic solvents can be utilized in the techniques described herein, organic solvents such as alcohols, polyhydric alcohols, and ketones may be preferred due to their compatibility and solubility with water. In some embodiments, isopropyl alcohol (IPA), acetic acid (AA), ethylene glycol (EG), or propylene glycol carbonate (PC) can be utilized as the organic solvent, which is mixed with one or more etchant chemicals (such as HF) and an aqueous solvent (HO) at various concentrations.

[0070] Graph 1200 shown in FIG. 12 illustrates normalized etch rate versus trench CD (expressed in nm) when a single etching solution 1125 having one or more etchant chemistries, an aqueous solvent, and an organic solvent, as shown in FIGS. 11A-11C, is used to etch silicon dioxide (SiO) material formed in trenches of various CDs when the SiO material is adjacent to a SiCN wall material. In graph 1200, the "normalized etch rate" is the ratio of the etch rate in a trench having a smaller CD to the etch rate in a trench having a larger CD. As shown in graph 1200, the normalized etch rate increases with decreasing CD when an etching solution having an organic solvent (e.g., HO:AA:HF=0:100:10) is used, and decreases with decreasing CD when an etching solution having an aqueous solvent (e.g., HO:AA:HF=100:0:10) is used. However, when the substrate is exposed to a single etching solution 1125 having both aqueous and organic solvents, the wet etching process 1100 shown in Figures 11A-11C provides a uniform etch rate (e.g., a normalized etch rate close to "1") within trenches of various CDs.

[0071] 12 shows a graph 1200 illustrating normalized etch rate versus trench CD for various different etching solutions that combine at least one etchant chemical with an aqueous solvent and an organic solvent. For example, graph 1200 illustrates normalized etch rate versus trench CD for (a) a first etching solution (denoted by ◇) that combines water (HO), acetic acid (AA), and hydrofluoric acid (HF) in a ratio of 35:65:10, (b) a second etching solution (denoted by △) that combines HO, AA, and HF in a ratio of 75:25:10, (c) a third etching solution (denoted by ○) that combines HO, AA, and HF in a ratio of 85:15:10, and (d) a fourth etching solution (denoted by ×) that combines HO, AA, and HF in a ratio of 95:5:10. Among these etching solutions, the third etching solution (indicated by O) and the fourth etching solution (indicated by X) meet the process window requirement for uniform etch rate in trenches of various CDs.

[0072] The wet etching processes disclosed herein provide uniform etching of material within features of different CDs formed on a substrate. The wet etching processes disclosed herein can be utilized during the processing of a wide variety of substrates. The substrate can be any substrate for which patterning of the substrate is desired. For example, in one embodiment, the substrate can be a semiconductor substrate having one or more semiconductor processing layers formed thereon (all of which together can comprise the substrate). Thus, in one embodiment, the substrate can be a semiconductor substrate that has undergone multiple semiconductor processing steps resulting in a wide variety of structures, features, and layers, all of which are known in the substrate processing art and can be considered part of the substrate. For example, in one embodiment, the substrate can be a semiconductor wafer having one or more semiconductor processing layers formed thereon. The concepts disclosed herein can be utilized at any stage in a substrate process flow.

[0073] 13-14 illustrate an exemplary method utilizing the techniques described herein to provide uniform etching of material within features of different CDs formed on a substrate. It will be understood that the embodiments illustrated in FIGS. 13-14 are merely exemplary, and that additional methods may utilize the techniques described herein. Furthermore, the described processing steps are not intended to be exclusive, and additional processing steps may be added to the methods illustrated in FIGS. 13-14. Furthermore, the order of steps is not limited to the order shown in the figures, as steps may occur in different orders and / or various steps may be combined or performed simultaneously.

[0074] 13 illustrates a method 1300 of etching according to one embodiment of the present disclosure. In some embodiments, the method 1300 illustrated in FIG. 13 may begin by providing (at step 1310) a substrate having a plurality of features, the plurality of features having different critical dimensions (CDs) with respect to one or more of the features. For example, the plurality of features may include at least a first feature having a smaller CD and a second feature having a larger CD.

[0075] In the embodiment shown in FIG. 13 , method 1300 exposes (in step 1320) a substrate to one or more etching solutions, either sequentially or in parallel, to etch material formed within multiple features. The one or more etching solutions may generally include an etchant chemical, an aqueous solvent, and an organic solvent. In method 1300 shown in FIG. 13 , the organic solvent utilized in the one or more etching solutions may be an alcohol, a polyhydric alcohol, acetic acid, or a ketone. Method 1300 shown in FIG. 13 provides uniform etching of material formed within multiple features, regardless of CD, by exposing the substrate to one or more etching solutions, either sequentially or in parallel.

[0076] In some embodiments, the material formed in the features may be an oxide, a dielectric material, silicon, or a metal. In one exemplary embodiment, the material formed in the features (i.e., the material to be etched) may be silicon dioxide (SiO2). In some embodiments, the wall material of the features may include a silicon-containing material, which exhibits a negative surface potential when exposed to aqueous solutions in a particular pH range. For example, the wall material may include amorphous silicon (a-Si), polysilicon (poly-Si), silicon nitride (SiCN), or silicon oxynitride (SiON).

[0077] In some embodiments, exposing the substrate to one or more etching solutions (Step 1320) may include exposing the substrate to a first etching solution comprising an etchant chemical and an organic solvent, and exposing the substrate to a second etching solution comprising an etchant chemical and an aqueous solvent.

[0078] In some embodiments, the etchant chemistry can include anions as the primary reactive species. When anions are utilized as the primary reactive species, exposing the substrate to a first etching solution etches the material formed in the first feature faster than the material formed in the second feature, while exposing the substrate to a second etching solution etches the material formed in the first feature slower than the material forming the second feature. Thus, exposing the substrate to the first etching solution and then exposing the substrate to the second etching solution etches the material formed in the first feature and the material formed in the second feature at a uniform etch rate.

[0079] In some embodiments, the wall material of the plurality of features may have a positive surface potential when the substrate is exposed to the first etching solution and a negative surface potential when the substrate is exposed to the second etching solution. For example, the wall material may include amorphous silicon (a-Si), polysilicon (poly-Si), silicon nitride (SiCN), or silicon oxynitride (SiON).

[0080] When the substrate is exposed to the first etching solution, the positive surface potential attracts anions in the etchant chemical, increasing the etch rate of the material formed in the first and second features. In this case, the increase in etch rate may be more pronounced in the first feature with the smaller CD and less pronounced in the second feature with the larger CD.

[0081] When the substrate is exposed to a second etching solution, the negative surface potential repels anions in the etchant chemical, reducing the etch rate of the material formed in the first and second features, where the reduction in etch rate may be more pronounced in the first feature with the smaller CD and less pronounced in the second feature with the larger CD.

[0082] In other embodiments, the etchant chemistry may include cations instead of anions as the primary reactive species. When cations are utilized as the primary reactive species, exposing the substrate to a first etching solution etches the material formed in the first feature slower than the material formed in the second feature, while exposing the substrate to a second etching solution etches the material formed in the first feature faster than the material forming the second feature. Thus, exposing the substrate to the first etching solution and then exposing the substrate to the second etching solution etches the material formed in the first feature and the material formed in the second feature at a uniform etch rate.

[0083] In some embodiments, method 1300 may sequentially expose the substrate to one or more etching solutions (in step 1320). In some embodiments, for example, exposing the substrate to one or more etching solutions (step 1320) may include exposing the substrate to a first etching solution for a first period of time, followed by subsequently exposing the substrate to a second etching solution for a second period of time that occurs at least partially after the first period of time. In other embodiments, exposing the substrate to one or more etching solutions (step 1320) may include exposing the substrate to a second etching solution for a first period of time, followed by subsequently exposing the substrate to the first etching solution for a second period of time that occurs at least partially after the first period of time.

[0084] In other embodiments, method 1300 may expose the substrate to one or more etching solutions in parallel (in step 1320). In some embodiments, for example, exposing the substrate to one or more etching solutions (step 1320) may include exposing the substrate to a first etching solution and exposing the substrate to a second etching solution substantially simultaneously or during overlapping periods. In other embodiments, exposing the substrate to one or more etching solutions (step 1320) may include exposing the substrate to a single etching solution including an etchant chemical, an aqueous solvent, and an organic solvent, whereby the material in the first feature and the second feature is etched at a uniform etch rate.

[0085]

[0013] Figure 14 illustrates a method 1400 of etching according to another embodiment of the present disclosure. Similar to method 1300 illustrated in Figure 13, method 1400 illustrated in Figure 14 may begin by providing (at step 1410) a substrate having a plurality of features, the plurality of features having different critical dimensions (CDs) with respect to one or more of the features. For example, the plurality of features may include at least a first feature having a smaller CD and a second feature having a larger CD.

[0086] In the embodiment shown in Figure 14, method 1400 sequentially exposes (at step 1420) a substrate to a first etching solution and a second etching solution to etch material formed within the plurality of features. The first etching solution includes an etchant chemical mixed with an organic solvent. The second etching solution includes an etchant chemical mixed with an aqueous solvent. By sequentially exposing the substrate to the first etching solution and the second etching solution, method 1400 provides uniform etching of material formed within the plurality of features, regardless of CD.

[0087] In some embodiments, sequentially exposing the substrate to the first etching solution and the second etching solution (Step 1420) may include exposing the substrate to the first etching solution for a first period of time, followed by exposing the substrate to the second etching solution for a second period of time that occurs at least partially after the first period of time. By exposing the substrate to the first etching solution, the material formed in the first feature is etched faster than the material formed in the second feature. When the substrate is subsequently exposed to the second etching solution, the second etching solution etches the material formed in the first feature slower than the material forming the second feature. Thus, the method 1400 etches the material formed in the first feature and the material formed in the second feature at a uniform etch rate by exposing the substrate to the first etching solution and subsequently exposing the substrate to the second etching solution.

[0088] In other embodiments, sequentially exposing the substrate to the first etching solution and the second etching solution (Step 1420) may include exposing the substrate to the second etching solution for a first period of time, followed by exposing the substrate to the first etching solution for a second period of time that occurs at least partially after the first period of time. By exposing the substrate to the second etching solution, the material formed in the first feature is etched slower than the material forming the second feature. However, by exposing the substrate to the first etching solution, the material formed in the first feature is etched faster than the material formed in the second feature. Thus, the method 1400 etches the material formed in the first feature and the material formed in the second feature at a uniform etch rate by exposing the substrate to the second etching solution followed by exposing the substrate to the first etching solution.

[0089] 14 may further include providing a time delay between the first time period and the second time period to prevent mixing of the first etching solution and the second etching solution on the surface of the substrate. In other embodiments, the second time period may overlap with the first time period, resulting in mixing between the first etching solution and the second etching solution on the surface of the substrate.

[0090] 13 and 14, a wide variety of etchants may be used in the first and second etching solutions. In some embodiments, the etchant chemicals may include one or more of hydrofluoric acid (HF), ammonium hydroxide (NH4OH), hydrochloric acid (HCl), hydrogen peroxide (HO), nitric acid (HNO3), phosphoric acid (H3PO4), potassium hydroxide (KOH), tetramethylammonium hydroxide (TMAH), and other etchant chemicals that contain anions (negatively charged ions) as the primary reactive species. In other embodiments, the etchant chemicals utilized in the first and second etching solutions may contain cations (positively charged ions) as the primary reactive species.

[0091] A wide variety of organic solvents can also be used in the first etching solution. Examples of organic solvents that can be included in the first etching solution include methanol (CHO), ethanol (CHO), isopropyl alcohol (CHO), benzyl alcohol (CHO), ethylene glycol (CHO), acetic acid (CHCOOH), acetone (CHO), propylene carbonate (CHO), n-hexane (CHO), and the like. 14 ), cyclohexane (CH 12 ), diethyl ether (C4H 10 O), tetrahydrofuran (C4H8O), benzene (C6H6), toluene (C7H8), dichloromethane (CH2Cl2), trichloroethylene (C2HCl3), 1,1,1-trichloroethane (C2H3Cl3), 1,2-dichloroethane (C2H4Cl2), N-methyl-2-pyrrolidone (C5H9NO), dimethyl sulfoxide (C2H6OS), ethyl lactate (C5H 10 O3), ethanolamine (C2H7NO), and propylene glycol methyl ether acetate (C6H 12 In some embodiments, the organic solvent used in the first etching solution can be isopropyl alcohol (C3H8O), propylene carbonate (C4H6O3), acetic acid (CH3COOH), or ethylene glycol (C2H6O2).

[0092] It should be noted that throughout this specification, references to "one embodiment" or "an embodiment" mean that a particular feature, structure, material, or characteristic described in connection with this embodiment is included in at least one embodiment of the invention, but do not necessarily mean that it is present in all embodiments. Thus, the appearances of the phrase "in one embodiment" or "in an embodiment" in various places throughout this specification do not necessarily refer to the same embodiment of the invention. Furthermore, particular features, structures, materials, or characteristics may be combined in any suitable manner in one or more embodiments. In other embodiments, various additional layers and / or structures may be included and / or described features may be omitted.

[0093] As used herein, the term "substrate" refers to and includes a base material or structure upon which a material is formed. It will be understood that a substrate can include a single material, multiple layers of different materials, or one or more layers having regions of different materials or structures therein. These materials can include semiconductors, insulators, conductors, or combinations thereof. For example, the substrate can be a semiconductor substrate, a base semiconductor layer on a supporting structure, a metal electrode, or a semiconductor substrate with one or more layers, structures, features, or regions formed thereon. The substrate can be a conventional silicon substrate or other bulk substrate containing a layer of semiconducting material. As used herein, the term "bulk substrate" refers to and includes not only silicon wafers, but also silicon-on-insulator ("SOI") substrates such as silicon-on-sapphire ("SOS") and silicon-on-glass ("SOG") substrates, epitaxial layers of silicon on a base semiconductor substrate, and other semiconductor or optoelectronic materials such as silicon germanium, germanium, gallium arsenide, gallium nitride, and indium phosphide. The substrate may be doped or undoped.

[0094] Wet etching processes and methods for processing a substrate are described in various embodiments. The substrate may include any material portion or structure of a device, particularly a semiconductor or other electronic device, and may be, for example, a base substrate structure such as a semiconductor substrate, or a layer on or overlying the base substrate structure, such as a thin film. Thus, the term "substrate" is not intended to be limited to any particular base structure, underlying layer, or overlying layer, patterned or unpatterned, but rather is intended to include any such layer or base structure and any combination of layers and / or base structures.

[0095] Those skilled in the art will understand that various embodiments may be practiced without one or more of the specific details, or with other alternative and / or additional methods, materials, or components. In other instances, well-known structural, material, or operational details have not been shown or described to avoid obscuring aspects of the various embodiments of the invention. Similarly, for purposes of explanation, specific numbers, materials, and configurations are set forth to provide a thorough understanding of the invention. However, the invention may be practiced without the specific details. Furthermore, it should be understood that the various embodiments shown in the figures are illustrative representations and are not necessarily drawn to scale.

[0096] Further modifications and alternative embodiments of the described wet etching processes and methods will be apparent to those skilled in the art upon review of this specification. Accordingly, it will be understood that the described wet etching processes and methods are not limited by the examples set forth herein. It should be understood that the forms of the processes and methods shown and described herein are to be construed as exemplary embodiments. Various modifications may be made in implementation. Thus, while the present invention is described herein with reference to specific embodiments, various modifications and changes can be made without departing from the scope of the present invention. Accordingly, this specification and the accompanying drawings should be regarded in an illustrative rather than a restrictive sense, and such modifications are intended to be included within the scope of the present invention. Furthermore, any benefits, advantages, or solutions to problems described herein with respect to particular embodiments are not intended to be construed as critical, necessary, or essential features or elements of any or all of the claims.

Claims

1. 1. A method of etching comprising the steps of: providing a substrate having a plurality of features, wherein a critical dimension (CD) of the plurality of features varies for one or more of the features, the plurality of features including at least a first feature having a smaller CD and a second feature having a larger CD; exposing the substrate, in sequence or in parallel, to one or more etching solutions to etch material formed within the plurality of features, the one or more etching solutions comprising an etchant chemical, an aqueous solvent, and an organic solvent, the organic solvent being an alcohol, a polyhydric alcohol, acetic acid, or a ketone; and wherein exposing the substrate to the one or more etching solutions, in sequence or in parallel, provides uniform etching of the material formed within the plurality of features, regardless of CD.

2. the etchant chemistry includes anions as the primary reactive species; exposing the substrate to one or more etching solutions exposing the substrate to a first etching solution comprising the etchant chemical and the organic solvent, wherein exposing the substrate to the first etching solution etches the material formed in the first feature faster than the material formed in the second feature; exposing the substrate to a second etching solution comprising the etchant chemical and the aqueous solvent, wherein exposing the substrate to the second etching solution etches the material formed in the first feature slower than the material formed in the second feature; and 10. The method of claim 1, wherein exposing the substrate to the first etching solution and exposing the substrate to the second etching solution etches the material formed in the first feature and the material formed in the second feature at a uniform etch rate.

3. The etchant chemicals include hydrofluoric acid (HF), ammonium hydroxide (NH ４ OH), hydrochloric acid (HCl), hydrogen peroxide (H ２ O ２ ), nitric acid (HNO ３ ), phosphoric acid (H ３ P.O. ４ ), potassium hydroxide (KOH), and tetramethylammonium hydroxide (TMAH); the aqueous solvent is water, The organic solvent is isopropyl alcohol (C ３ H ８ O), propylene carbonate (C ４ H ６ O ３ ), acetic acid (CH ３ COOH), or ethylene glycol (C ２ H ６ O ２ 3. The method of claim 2, comprising one or more of:

4. exposing the substrate to the first etching solution increases an etch rate of the material formed in the first feature and the second feature; 3. The method of claim 2, wherein the increase in etch rate is more significant in the first feature having the smaller CD and less significant in the second feature having the larger CD.

5. exposing the substrate to the second etching solution reduces an etch rate of the material formed in the first feature and the second feature; 3. The method of claim 2, wherein the etch rate reduction is more pronounced in the first feature having the smaller CD and less pronounced in the second feature having the larger CD.

6. exposing the substrate to one or more etching solutions comprises exposing the substrate to the first etching solution for a first period of time followed by subsequently exposing the substrate to the second etching solution for a second period of time; The method of claim 2 , wherein the second period of time occurs at least in part after the first period of time.

7. exposing the substrate to one or more etching solutions comprises exposing the substrate to the second etching solution for a first period of time followed by subsequently exposing the substrate to the first etching solution for a second period of time; The method of claim 2 , wherein the second period of time occurs at least in part after the first period of time.

8. 3. The method of claim 2, wherein exposing the substrate to one or more etching solutions comprises exposing the substrate to the first etching solution and exposing the substrate to the second etching solution substantially simultaneously or during overlapping periods.

9. the etchant chemistry includes cations as the primary reactive species; The step of exposing the substrate to one or more etching solutions comprises: exposing the substrate to a first etching solution comprising the etchant chemical and the organic solvent, wherein exposing the substrate to the first etching solution etches the material formed in the first feature slower than the material formed in the second feature; exposing the substrate to a second etching solution comprising the etchant chemical and the aqueous solvent, wherein exposing the substrate to the second etching solution etches the material formed in the first feature faster than the material formed in the second feature; and 10. The method of claim 1, wherein exposing the substrate to the first etching solution and exposing the substrate to the second etching solution etches the material formed in the first feature and the material formed in the second feature at a uniform etch rate.

10. exposing the substrate to one or more etching solutions comprises exposing the substrate to a single etching solution comprising the etchant chemical, the aqueous solvent, and the organic solvent; The method of claim 1 , wherein exposing the substrate to the single etching solution etches the material in the first feature and the second feature at a uniform etch rate.

11. The etchant chemicals include hydrofluoric acid (HF), ammonium hydroxide (NH ４ OH), hydrochloric acid (HCl), hydrogen peroxide (H ２ O ２ ), nitric acid (HNO ３ ), phosphoric acid (H ３ P.O. ４ ), potassium hydroxide (KOH), and tetramethylammonium hydroxide (TMAH); the aqueous solvent is water, The organic solvent is isopropyl alcohol (C ３ H ８ O), propylene carbonate (C ４ H ６ O ３ ), acetic acid (CH ３ COOH), and ethylene glycol (C ２ H ６ O ２ 10. The method of claim 1, comprising one or more of:

12. The method of claim 1 , wherein the material formed in the plurality of features comprises an oxide, a dielectric material, silicon, or a metal.

13. 1. A method of etching comprising the steps of: providing a substrate having a plurality of features, wherein a critical dimension (CD) of the plurality of features varies for one or more of the features, the plurality of features including at least a first feature having a smaller CD and a second feature having a larger CD; sequentially exposing the substrate to a first etching solution and a second etching solution to etch material formed within the plurality of features; the first etching solution comprises an etchant chemical mixed with an organic solvent; the second etching solution comprising the etchant chemical mixed with an aqueous solvent; and wherein sequentially exposing the substrate to the first etching solution and the second etching solution provides uniform etching of material formed within the plurality of features, regardless of CD.

14. Sequentially exposing the substrate to the first etching solution and the second etching solution comprises: exposing the substrate to the first etching solution for a first period of time, wherein exposing the substrate to the first etching solution etches the material formed in the first feature faster than the material formed in the second feature; subsequently exposing the substrate to the second etching solution for a second period of time, the second period of time occurring at least in part after the first period of time, wherein the subsequently exposing the substrate to the second etching solution etches the material formed in the first feature more slowly than the material formed in the second feature; and 14. The method of claim 13, wherein exposing the substrate to the first etching solution and subsequently exposing the substrate to the second etching solution etches the material formed in the first feature and the material formed in the second feature at a uniform etch rate.

15. 15. The method of claim 14, further comprising providing a time delay between the first period of time and the second period of time, wherein the first etching solution and the second etching solution do not mix at the surface of the substrate.

16. 15. The method of claim 14, wherein the second period of time overlaps with the first period of time, and mixing occurs between the first etching solution and the second etching solution at the surface of the substrate.

17. Sequentially exposing the substrate to the first etching solution and the second etching solution comprises: exposing the substrate to the second etching solution for a first period of time, wherein exposing the substrate to the second etching solution etches the material formed in the first feature slower than the material formed in the second feature; subsequently exposing the substrate to the first etching solution for a second period of time, the second period of time occurring at least in part after the first period of time, wherein exposing the substrate to the first etching solution etches the material formed in the first feature faster than the material formed in the second feature; and 14. The method of claim 13, wherein exposing the substrate to the second etching solution and subsequently exposing the substrate to the first etching solution etches the material formed in the first feature and the material formed in the second feature at a uniform etch rate.

18. 20. The method of claim 17, further comprising providing a time delay between the first time period and the second time period, wherein the first etching solution and the second etching solution do not mix at the surface of the substrate.

19. 20. The method of claim 17, wherein the second period of time overlaps with the first period of time, causing mixing between the first etching solution and the second etching solution at the surface of the substrate.

20. The etchant chemicals include hydrofluoric acid (HF), ammonium hydroxide (NH ４ OH), hydrochloric acid (HCl), hydrogen peroxide (H ２ O ２ ), nitric acid (HNO ３ ), phosphoric acid (H ３ P.O. ４ 14. The method of claim 13, wherein the solvent comprises one or more of: potassium hydroxide (KOH), and tetramethylammonium hydroxide (TMAH).

21. The organic solvent is methanol (CH ４ O), ethanol (C ２ H ６ O), isopropyl alcohol (C ３ H ８ O), benzyl alcohol (C ７ H ８ O), ethylene glycol (C ２ H ６ O ２ ), acetic acid (CH ３ COOH), acetone (C ３ H ６ O), propylene carbonate (C ４ H ６ O ３ ), n-hexane (C ６ H １４ ), cyclohexane (C ６ H １２ ), diethyl ether (C ４ H １０ O), tetrahydrofuran (C ４ H ８ O), benzene (C ６ H ６ ), toluene (C ７ H ８ ), dichloromethane (CH ２ Cl ２ ), trichloroethylene (C ２ HCl ３ ), 1,1,1-trichloroethane (C ２ H ３ Cl ３ ), 1,2-dichloroethane (C ２ H ４ Cl ２ ), N-methyl-2-pyrrolidone (C ５ H ９ NO), dimethyl sulfoxide (C ２ H ６ OS), ethyl lactate (C ５ H １０ O ３ ), ethanolamine (C ２ H ７ NO), and propylene glycol methyl ether acetate (C ６ H １２ O ３ 14. The method of claim 13, comprising one or more of:

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