Etching solution

Abstract

In one embodiment, an etching solution with excellent storage stability is provided. [Solution] In one embodiment, this disclosure relates to an etching solution comprising the following components A, B, and C. Component A: Phosphate Component B: Titanium compound represented by the following formula (I) Ingredient C: Silica TIFF2026168726000010.tif21170

Description

TECHNICAL FIELD

[0001] The present disclosure relates to an etchant for silicon carbonitride (SiCN), an etching method using the same, and a method for manufacturing a semiconductor substrate.

BACKGROUND ART

[0002] In recent years, along with the high integration of semiconductors, a wide variety of materials such as silicon oxide (SiO₂), silicon nitride (Si₃N₄), polysilicon (Poly-Si), tungsten (W), molybdenum (Mo), silicon carbonitride (SiCN), and titanium nitride (TiN) are used in the manufacture of semiconductor devices. In the manufacturing process of semiconductor devices, a step of selectively etching and removing only a specific material is performed.

[0003] For example, Patent Document 1 discloses a treatment method for treating an object to be treated using an atomized or dropletized treatment agent. In paragraphs 0012 to 0014 of the same document, an etching agent such as phosphoric acid and a surface modifier such as a titanate coupling agent are disclosed as the treatment agent. Patent Document 2 discloses a method for removing silicon nitride (SiN) using a liquid composition containing an etching component such as phosphoric acid, a solvent, and fine particles such as silica. Paragraph 0028 of the same document describes that a surface treatment agent such as a titanate-based coupling agent may be added to the liquid composition.

PRIOR ART DOCUMENTS

PATENT DOCUMENTS

[0004]

PATENT DOCUMENT 1

PATENT DOCUMENT 2

SUMMARY OF THE INVENTION

PROBLEMS TO BE SOLVED BY THE INVENTION

[0005] A wide variety of materials are used in the manufacture of semiconductor devices, but silicon carbonitride (SiCN) is attracting particular attention. In the manufacturing process of three-dimensional semiconductor devices such as three-dimensional NAND flash memory, for example, a process is sometimes required to selectively etch silicon carbonitride (SiCN) from among silicon oxide (SiO2) and silicon carbonitride (SiCN). However, etching with commonly used phosphoric acid also etches silicon dioxide, so there is a need for an etching solution that can selectively etch silicon carbonitride while suppressing the etching of silicon dioxide. Furthermore, if the etching solution contains silica, there is a problem in that the silica particle size increases over time, leading to a deterioration in the quality of the etching solution.

[0006] Therefore, in one embodiment, this disclosure provides an etching solution with excellent storage stability, an etching method using the same, and a method for manufacturing a semiconductor substrate. [Means for solving the problem]

[0007] This disclosure relates, in one embodiment, to an etching solution comprising the following components A, B, and C. Component A: Phosphate Component B: Titanium compound represented by the following formula (I) Ingredient C: Silica [ka] In the above equation (I), R 1 R is a hydrogen atom or a saturated alkyl group having 1 to 10 carbon atoms, and n is an integer from 0 to 2. In the above formula (I), R 2 This is an alkyl group having 2 to 20 carbon atoms and having at least one selected from an ester group, a carboxyl group, a ketone group, a hydroxyl group, and an amino group, wherein at least one carbon atom of the alkyl group may be substituted with S, N, or O.

[0008] This disclosure relates, in one embodiment, to an etching method that includes the step of etching silicon carbonitride (SiCN) using an etching solution of this disclosure.

[0009] This disclosure relates, in one embodiment, to a method for manufacturing a semiconductor substrate, including the etching method of this disclosure. [Effects of the Invention]

[0010] According to this disclosure, in one embodiment, an etching solution with excellent storage stability can be provided. [Modes for carrying out the invention]

[0011] This disclosure is based on the finding that, in one embodiment, by blending phosphoric acid and a titanium compound in a specific mass ratio into an etching solution containing silica, it is possible to suppress the increase in silica particle size in the etching solution over time and improve storage stability.

[0012] In other words, in one embodiment, this disclosure relates to an etching solution comprising the following components A, B, and C (hereinafter also referred to as "the etching solution of this disclosure"). Component A: Phosphate Component B: Titanium compound represented by the above formula (I) Ingredient C: Silica Here, "formulated by combining" means that not only components A, B, and C, but also optional components (components D, E, and other components described later) can be added as needed.

[0013] According to this disclosure, it is possible to suppress the increase in silica particle size in the etching solution over time and to provide an etching solution with excellent storage stability. In one or more embodiments, the etching solution of this disclosure can selectively etch silicon carbonitride while suppressing the etching of silicon oxide.

[0014] Although the detailed mechanism of how the effects of this disclosure are realized is not clear, it is presumed to be as follows. The reaction formulas in the etching of silicon nitride (Si3N4) and silicon oxide (SiO2) by phosphoric acid are shown below. [Equation] As shown in the above formula (1), hydrated silica (H2SiO3) is generated in the etching of silicon nitride (Si3N4) by phosphoric acid. According to Le Chatelier's principle, when the silica concentration in the system increases, the reaction from silica (SiO2) to hydrated silica via the equilibrium reaction of formula (2) becomes less likely to proceed. Furthermore, it is considered that adding silica in the form of orthosilicic acid (Si(OH)4) also makes it possible to suppress the reaction from hydrated silica to orthosilicic acid. It is inferred that the etching of silicon carbonitride (SiCN) by phosphoric acid also causes a reaction similar to that of the above-described silicon nitride (Si3N4). That is, it is considered that adding silica or orthosilicic acid to phosphoric acid can suppress the etching of silicon oxide (SiO2), and enable selective etching of only silicon carbonitride (SiCN). On the other hand, orthosilicic acid generates silica through a dehydration condensation reaction under strongly acidic conditions. It is inferred that the particle size of the silica generated by this reaction increases over time due to the molecular structure of orthosilicic acid. Accordingly, in the present disclosure, by blending a specific titanium compound with phosphoric acid, the orthosilicic acid reacts with the specific titanium compound, which can suppress the increase in particle size, that is, the storage stability is considered to be improved. However, the present disclosure should not be construed as being limited to these mechanisms.

[0015] [Component A: Phosphoric acid] From the viewpoint of improving the etching rate of SiCN, the amount of phosphoric acid (hereinafter also referred to as "component A") in the etching solution of this disclosure is preferably 50% by mass or more, more preferably 70% by mass or more, and even more preferably 80% by mass or more. From the same viewpoint, it is preferably 95% by mass or less, more preferably 90% by mass or less, and even more preferably 85% by mass or less. More specifically, the amount of component A in the etching solution of this disclosure is preferably 50% by mass or more and 95% by mass or less, more preferably 70% by mass or more and 95% by mass or less, even more preferably 70% by mass or more and 90% by mass or less, and even more preferably 80% by mass or more and 85% by mass or less.

[0016] [Component B: Titanium compound] The titanium compound (hereinafter also referred to as "component B") blended into or contained in the etching solution of this disclosure is a titanium compound represented by the following formula (I). Component B may be one type or a combination of two or more types. [ka]

[0017] In the above equation (I), R 1 is a hydrogen atom or a saturated alkyl group having 1 to 10 carbon atoms, n is an integer from 0 to 2, and R 2 This is an alkyl group having 2 to 20 carbon atoms and having at least one selected from an ester group, a carboxyl group, a ketone group, a hydroxyl group, and an amino group, wherein at least one carbon atom of the alkyl group may be substituted with S, N, or O. In the above equation (I), R 1 From the viewpoint of suppressing the increase in silica particle size and improving storage stability, it is preferable that the material contains a hydrogen atom or an isopropyl group, and more preferably a hydrogen atom or an isopropyl group. In the above formula (I), n is preferably an integer between 1 and 2 from the viewpoint of suppressing the increase in silica particle size and improving storage stability. In the above equation (I), R 2From the viewpoint of suppressing particle size increase of silica and improving storage stability, at least one selected from a C3 alkyl group having a carboxyl group, a C6 alkyl group having a hydroxyl group and a nitrogen atom, and a C6 alkyl group having an ester group and a ketone group is preferred. 2 From a similar viewpoint, it is preferable that it contains a carboxyethyl group, a bis(hydroxyethyl)aminoethyl group, an aminoethyl group, a hydroxyethyl group, a bis(aminoethyl)aminoethyl group, or an ethoxybutyldione group, and more preferably a carboxyethyl group, a bis(hydroxyethyl)aminoethyl group, a bis(aminoethyl)aminoethyl group, or an ethoxybutyldione group. 2 Specifically, these include -CH(CH3)COOH, -C2H4NHC2H4NH2, -C2H4N(C2H4NH2)2, and -CH2COCH2COOCH2CH3.

[0018] As for component B, from the viewpoint of suppressing the increase in silica particle size and improving storage stability, in one or more embodiments, at least one selected from dihydroxybis(acetact)titanium(IV), dihydroxybis(lactate)titanium(IV), bis(isopropoxy)bis(N,N-di(2-hydroxyethyl)aminoethanolate)titanium(IV), tris((aminoethyl)aminoethanolate)mono(isopropoxy)titanium(IV), and bis(isopropoxy)bis(2-ethylacetacetate)titanium(IV) is included.

[0019] The amount of component B in the etching solution of this disclosure is preferably 0.001% by mass or more, more preferably 0.01% by mass or more, and even more preferably 0.05% by mass or more, from the viewpoint of suppressing the increase in silica particle size and improving storage stability. From the same viewpoint, it is preferably 20% by mass or less, more preferably 10% by mass or less, and even more preferably 5% by mass or less. More specifically, the amount of component B in the etching solution of this disclosure is preferably 0.001% by mass or more and 20% by mass or less, more preferably 0.01% by mass or more and 10% by mass or less, and even more preferably 0.05% by mass or more and 5% by mass or less. If component B is a combination of two or more types, the amount of component B is the total amount of those types.

[0020] The mass ratio A / B (amount of component A (mass%) / amount of component B (mass%)) of component A to component B in the etching solution of this disclosure is preferably 5 or more, more preferably 10 or more, and even more preferably 20 or more, from the viewpoint of suppressing particle size increase of silica and improving storage stability. From the viewpoint of improving the etching rate of SiCN and suppressing the etching rate of silicon oxide, it is preferably 8500 or less, more preferably 5000 or less, even more preferably 2500 or less, even more preferably 1000 or less, even more preferably 100 or less, and even more preferably 50 or less. More specifically, the mass ratio A / B in the etching solution of this disclosure is preferably 5 or more and 8500 or less, more preferably 10 or more and 5000 or less, even more preferably 20 or more and 2500 or less, even more preferably 20 or more and 1000 or less, even more preferably 20 or more and 100 or less, and even more preferably 20 or more and 50 or less.

[0021] [Component C: Silica] From the viewpoint of suppressing the etching of silicon dioxide, it is preferable that at least a portion of the silica (hereinafter also referred to as "component C") blended or contained in the etching solution of this disclosure is dissolved in the etching solution of this disclosure. In one or more embodiments, an alkali can be used to dissolve the silica (component C). Therefore, from the viewpoint of suppressing the etching of silicon dioxide, it is preferable that the silica (component C) used in the preparation of the etching solution of this disclosure is blended in a solution containing silica and an alkali. In other words, the etching solution of the present disclosure may, in one or more other embodiments, contain or be a mixture of a solution containing component A, component B, silica (component C), and alkali. Here, "a mixture of" means that not only a solution containing component A, component B, silica, and alkali may be mixed, but any other components may be mixed as needed.

[0022] <Solution containing silica and alkali> In one or more embodiments, the solution containing silica and alkali is preferably a silica solution (hereinafter also simply referred to as "silica solution") in which at least a portion of the silica is dissolved in alkali, from the viewpoint of suppressing the etching of silicon dioxide. The silica dissolving solution is, in one or more embodiments, a silica dissolving solution in which silica is dissolved to a level below the detection limit by various particle size measuring instruments or by visual inspection. As will be described later, the silica dissolving solution may contain undissolved silica. The silica dissolving solution can be obtained, for example, by mixing silica with an alkali and dissolving the silica. Examples of methods for dissolving silica include heating, pressurizing, or mechanical grinding, and these may be used in combination. For example, heating conditions can be set to 60-100°C. For example, pressurizing conditions can be set to 0-3 MPa. Mechanical grinding can be performed, for example, using a ball mill. Furthermore, ultrasonic vibration may be applied when dissolving silica in alkali. The state of silica before mixing with alkali is not particularly limited, and examples include powder, sol, or gel.

[0023] Examples of silica used in preparing the silica solution (silica before dissolution) include crystalline silica, amorphous silica, fumed silica, wet silica, and colloidal silica. From the viewpoint of suppressing the etching of silicon dioxide, fumed silica and colloidal silica are preferred. Examples of colloidal silica include those obtained by a particle growth method using an aqueous alkali silicate solution as a raw material (hereinafter also referred to as the "water glass method") and a method by condensation of hydrolysates of alkoxysilanes (hereinafter also referred to as the "sol-gel method"). Silica particles obtained by the water glass method and the sol-gel method can be manufactured by conventionally known methods. Component C can be used in combination of one or two or more types.

[0024] In one or more embodiments, the alkali used in preparing the silica solution may be an organic alkali or an inorganic alkali. The organic alkali used in preparing the silica solution can be any alkali capable of dissolving silica, such as quaternary ammonium salts like tetraalkylammonium hydroxide. Specific examples of quaternary ammonium salts include at least one selected from tetramethylammonium hydroxide (TMAH), tetraethylammonium hydroxide (TEAH), and trimethylethylammonium hydroxide (ETMAH). Among these, TMAH is preferred from the viewpoint of suppressing the etching of silicon dioxide. The inorganic alkali used in preparing the silica solution can be any alkali capable of dissolving silica, such as sodium hydroxide or potassium hydroxide. In one or more embodiments, the alkali used in preparing the silica solution is preferably at least one selected from tetramethylammonium hydroxide (TMAH), trimethylethylammonium hydroxide (ETMAH), sodium hydroxide, and potassium hydroxide, with TMAH being more preferred among these.

[0025] In one or more embodiments, the silica solution contains orthosilicic acid. The silica dissolving solution may, in one or more embodiments, contain silica that did not dissolve in the alkali. That is, the etching solution of this disclosure may, in one or more embodiments, contain undissolved silica. From the viewpoint of suppressing the etching of silicon oxide, the undissolved silica is preferably fine silica. As for the average particle size of fine silica, for example, the volume-average particle size Dv50 is preferably 1 nm to 100 nm, and the volume-average particle size Dv90 is preferably 1 nm to 150 nm. In this disclosure, the volume-average particle size of silica is the average particle size based on the scattering intensity distribution measured at a detection angle of 175° using dynamic light scattering. Dv50 means the particle size at which the cumulative volume ratio from the smaller diameter side of the particle size distribution, determined based on the scattering intensity distribution measured by dynamic light scattering (DLS), is 50%. Dv90 means the particle size at which the cumulative volume ratio from the smaller diameter side of the particle size distribution, determined based on the scattering intensity distribution measured by dynamic light scattering (DLS), is 90%. Specifically, it can be measured by the method described in the examples.

[0026] The amount of component C in the etching solution of this disclosure (total amount of dissolved silica and undissolved silica) is preferably 0.001% by mass or more, more preferably 0.01% by mass or more, and even more preferably 0.02% by mass or more, from the viewpoint of suppressing the etching rate of silicon dioxide, and from the viewpoint of improving the etching rate of SiCN and suppressing the etching rate of silicon dioxide, it is preferably 1% by mass or less, more preferably 0.5% by mass or less, and even more preferably 0.1% by mass or less. More specifically, the amount of component C in the etching solution of this disclosure is preferably 0.001% by mass or more and 1% by mass or less, more preferably 0.01% by mass or more and 0.5% by mass or less, and even more preferably 0.02% by mass or more and 0.1% by mass or less. When component C is a combination of two or more types, the amount of component C is the total amount of those types.

[0027] When the etching solution of this disclosure contains a solution containing silica and alkali, the amount of alkali in the etching solution of this disclosure is preferably 0.005% by mass or more, more preferably 0.05% by mass or more, even more preferably 0.1% by mass or more, and from the same viewpoint, preferably 6% by mass or less, more preferably 3% by mass or less, and even more preferably 0.65% by mass or less. More specifically, the amount of alkali in the etching solution of this disclosure is preferably 0.005% by mass or more and 6% by mass or less, more preferably 0.05% by mass or more and 3% by mass or less, and even more preferably 0.1% by mass or more and 0.65% by mass or less. When there is a combination of two or more alkalis, the amount of alkali is the total amount of those alkalis.

[0028] The total amount of component A, component B, and component C in the etching solution of this disclosure is preferably 70% by mass or more, more preferably 75% by mass or more, and even more preferably 80% by mass or more, from the viewpoint of improving the etching rate of silicon carbonitride, suppressing the increase in silica particle size, and improving storage stability. Furthermore, from the viewpoint of improving the etching rate of silicon carbonitride, it is preferably 95% by mass or less, more preferably 90% by mass or less, and even more preferably 85% by mass or less.

[0029] [Component D: Fluorine compound] In one or more embodiments, the etching solution of this disclosure further comprises or contains a fluorine compound (hereinafter also referred to as "component D") from the viewpoint of improving SiCN etching selectivity. Component D includes at least one selected from hydrogen fluoride, monofluorophosphate, hexafluorophosphate, and ammonium fluoride, among which hydrogen fluoride and ammonium fluoride are preferred, and hydrogen fluoride is more preferred. Component D may be one type or a combination of two or more types. The mechanism by which fluorine compounds improve SiCN etching selectivity is thought to be as follows. The reaction equation for etching silicon nitride (Si3N4) and silicon oxide (SiO2) with hydrogen fluoride (HF) is shown below.

number

[0030] When component D is included in the etching solution of this disclosure, the amount of component D in the etching solution of this disclosure is preferably 0.001% by mass or more, more preferably 0.01% by mass or more, and even more preferably 0.02% by mass or more, from the viewpoint of improving SiCN etching selectivity and improving the etching rate of SiCN, and preferably 5% by mass or less, more preferably 1% by mass or less, and even more preferably 0.1% by mass or less, from the viewpoint of improving the etching rate of SiCN and suppressing the increase in silica particle size. More specifically, the amount of component D in the etching solution of this disclosure is preferably 0.001% by mass or more and 5% by mass or less, more preferably 0.01% by mass or more and 1% by mass or less, and even more preferably 0.02% by mass or more and 0.1% by mass or less. When component D is a combination of two or more types, the amount of component D is the total amount of those types.

[0031] [Ingredient E: Water] In one or more embodiments, the etching solution of this disclosure further comprises or contains water (hereinafter also referred to as "component E"). Examples of component E include distilled water, deionized water, pure water, and ultrapure water. If component E is included in the etching solution of this disclosure, the amount of component E in the etching solution of this disclosure is preferably 5% by mass or more, more preferably 7.5% by mass or more, and even more preferably 10% by mass or more, from the viewpoint of improving the etching rate of SiCN, and similarly, preferably 30% by mass or less, more preferably 25% by mass or less, and even more preferably 20% by mass or less. More specifically, the amount of component E in the etching solution of this disclosure is preferably 5% by mass or more and 30% by mass or less, more preferably 7.5% by mass or more and 25% by mass or less, and even more preferably 10% by mass or more and 20% by mass or less.

[0032] [Other ingredients] The etching solution of this disclosure may further contain or be formulated with other components, to the extent that the effects of this disclosure are not impaired. Examples of other components include at least one selected from acids other than phosphoric acid, alkalis, chelating agents, high-temperature stabilizers, organic phosphonic acids, surfactants, solubilizers, preservatives, rust inhibitors, bactericides, antimicrobial agents, and antioxidants.

[0033] [Method for manufacturing etching solution] The etching solution of this disclosure is obtained in one or more embodiments by compounding component A, component B, component C and optionally the above-mentioned optional components (component D, component E, and other components) in a known manner. Accordingly, this disclosure relates in one embodiment to a method for manufacturing an etching solution, which includes the step of compounding at least component A, component B, and component C. In this embodiment, "compounding" includes, in one or more embodiments, simultaneously or sequentially mixing component A, component B, component C, and any optional components (component D, component E, and other components) as described above. The order of mixing is not particularly limited. The compounding can be carried out using a mixer such as a homomixer, homogenizer, ultrasonic disperser, and wet ball mill.

[0034] In one or more other embodiments, the etching solution of this disclosure is obtained by compounding component A, component B, a solution containing silica and alkali, and optionally the above-mentioned optional components (component D, component E, and other components) in a known manner. In one or more embodiments, the solution containing silica and alkali is a silica dissolving solution obtained by mixing silica and alkali. Therefore, in other embodiments, this disclosure relates to a method for producing an etching solution, which includes at least the step of compounding component A, component B, and a solution containing silica and alkali. In one or more embodiments, the method for producing an etching solution of this embodiment may further include the step of preparing a silica dissolving solution by mixing silica and alkali. In this embodiment, "compounding" means, in one or more other embodiments, simultaneously or sequentially mixing component A, component B, a solution containing silica and alkali, and optionally the aforementioned optional components (component D, component E, and other components). The order of mixing is not particularly limited. The compounding can be carried out, for example, using a mixer such as a homomixer, homogenizer, ultrasonic disperser, and wet ball mill.

[0035] In this disclosure, "amount of each component in the etching solution" means, in one or more embodiments, the amount of each component in the etching solution used in the etching process, i.e., at the time of use when the etching process begins. The amounts of each component in the etching solution of this disclosure can be considered as the content of each component in the etching solution of this disclosure in one or more embodiments. However, the amounts of each component and the content may differ when neutralization is involved.

[0036] From the viewpoint of improving the etching rate of SiCN, the pH of the etching solution of this disclosure is preferably 2 or less, more preferably 1.5 or less, and even more preferably 1 or less. In this disclosure, the pH of the etching solution is the value of the etching solution at 25°C at the time of use, and can be measured using a pH meter, specifically by the method described in the examples.

[0037] The etching solutions of this disclosure are, in one or more embodiments, for use in etching where the etching temperature is 110°C or higher and 250°C or lower.

[0038] The etching solution of this disclosure may be stored and supplied in a concentrated state, provided that its stability is not compromised. This is preferable because it reduces manufacturing and transportation costs. This concentrated solution can then be used in the etching process after being appropriately diluted with water, an aqueous phosphoric acid solution, or the like as needed. A dilution ratio of 5 to 100 times is preferred.

[0039] [kit] In one aspect, this disclosure relates to a kit for manufacturing the etching solution of this disclosure (hereinafter also referred to as the "Kit of this Disclosure"). In one or more embodiments, the kit of this disclosure includes, for example, a kit containing a solution containing component A (first solution), a solution containing component B (second solution), and a solution containing silica (component C) and alkali (third solution), which are mixed separately and mixed at the time of use. After the first, second, and third solutions are mixed, they may be diluted with water or an aqueous phosphoric acid solution as needed. The first, second, or third solution may contain all or part of the water used to prepare the etching solution. The phosphoric acid contained in the first solution may be all or part of the phosphoric acid used to prepare the etching solution. The first, second, and third solutions may each contain the optional components described above as needed. In one or more other embodiments of the present disclosure, a kit may be provided that includes, for example, a solution containing component A (liquid 1), a solution containing component B (liquid 2), a solution containing silica (component C) and alkali (liquid 3), and a solution containing component D (liquid 4), all of which are mixed separately and mixed at the time of use. After the first, second, third, and fourth liquids are mixed, they may be diluted with water or an aqueous phosphoric acid solution as needed. The first, second, third, or fourth liquids may contain all or part of the water used to prepare the etching solution. The phosphoric acid contained in the first liquid may be all or part of the phosphoric acid used to prepare the etching solution. The first, second, third, and fourth liquids may each contain the optional components described above as needed. According to the kit of this disclosure, in one or more embodiments, an etching solution can be obtained that can selectively etch SiCN while suppressing the etching of silicon oxide, and which also has excellent storage stability.

[0040] [Object to be processed] In one or more embodiments, the etching target of the etching solution of this disclosure is silicon carbonitride (SiCN). Examples of materials to be processed include substrates containing silicon carbonitride (SiCN). Examples of substrates containing silicon carbonitride (SiCN) include substrates having a silicon carbonitride (SiCN) layer and a silicon oxide (SiO2) layer, and substrates having a silicon carbonitride (SiCN) layer. In one or more embodiments, the substrate having the silicon carbonitride (SiCN) layer and the silicon oxide (SiO2) layer may be a substrate having a three-dimensional structure in which multiple silicon carbonitride (SiCN) layers and multiple silicon oxide (SiO2) layers are alternately stacked. Examples of the aforementioned substrates include substrates for use in semiconductors and substrates for use in flat panel displays. Examples of substrates for use in semiconductors include silicon wafers. Examples of substrates for use in semiconductors include substrates for use in three-dimensional semiconductor devices such as three-dimensional NAND flash memory. Examples of the silicon carbonitride (SiCN) layer include silicon carbonitride layers (films) formed by methods such as low-pressure chemical vapor deposition (LPCVD), plasma chemical vapor deposition (PECVD), and atomic layer deposition (ALD). Examples of the silicon oxide (SiO2) layer include silicon oxide layers (films) formed by thermal oxidation, LPCVD, PECVD, ALD, and the like. The etching solution of this disclosure can be suitably used in the manufacture of three-dimensional semiconductor devices such as three-dimensional NAND flash memory in one or more embodiments. For example, the etching solution of this disclosure can be used in one or more embodiments to etch a substrate having a three-dimensional structure in which multiple silicon carbonitride (SiCN) layers and multiple silicon oxide (SiO2) layers are alternately stacked.

[0041] [Etching method] This disclosure relates, in one embodiment, to an etching method (hereinafter also referred to as "the etching method of this disclosure") which includes a step of etching silicon carbonitride (SiCN) using the etching solution of this disclosure (hereinafter also referred to as "the etching step"). The etching step, in one or more embodiments, is a step of removing the silicon carbonitride (SiCN) layer from a substrate having a silicon carbonitride (SiCN) layer and a silicon oxide (SiO2) layer. In one or more embodiments, the etching step is a step of removing a silicon carbonitride (SiCN) layer from a substrate having a silicon carbonitride (SiCN) layer. By using the etching method of this disclosure, in one or more embodiments, it is possible to selectively etch SiCN while suppressing the etching of silicon oxide, thereby improving the productivity of semiconductor substrates with improved quality.

[0042] Examples of etching methods in the etching process include immersion etching and single-wafer etching.

[0043] The etching temperature of the etching solution in the etching process is preferably 110°C or higher, more preferably 120°C or higher, even more preferably 140°C or higher, even more preferably 150°C or higher, and preferably 250°C or lower, more preferably 230°C or lower, even more preferably 200°C or lower, and even more preferably 180°C or lower, from the viewpoint of improving the etching rate of SiCN and suppressing the etching rate of silicon oxide. From a similar viewpoint, the etching temperature of the etching solution is preferably 110°C or higher and 250°C or lower, more preferably 120°C or higher and 230°C or lower, even more preferably 140°C or higher and 200°C or lower, and even more preferably 150°C or higher and 180°C or lower.

[0044] The etching time in the etching process is preferably 5 minutes or more, more preferably 15 minutes or more, even more preferably 30 minutes or more, and can be set to preferably 270 minutes or less, more preferably 180 minutes or less.

[0045] From the viewpoint of improving productivity, the etching rate of silicon carbonitride (SiCN) in the etching process is preferably 3 nm / min or more, more preferably 4 nm / min or more, and even more preferably 5 nm / min or more. In the etching process described above, the etching rate of silicon dioxide (SiO2) is preferably 0.08 nm / min or less, more preferably 0.07 nm / min or less, even more preferably 0.05 nm / min or less, even more preferably 0.04 nm / min or less, even more preferably 0.03 nm / min or less, even more preferably 0.02 nm / min or less, and even more preferably 0.01 nm / min or less, from the viewpoint of improving productivity.

[0046] In the etching process described above, the etching rate ratio of silicon carbonitride to silicon oxide (SiCN / SiO2) is preferably 250 or higher, more preferably 300 or higher, and even more preferably 500 or higher, from the viewpoint of improving productivity.

[0047] [Manufacturing method for semiconductor substrates] The etching solution and etching method of the present disclosure described above can be suitably used in the manufacture of semiconductor substrates in one or more embodiments. Accordingly, this disclosure relates in one embodiment to a method for manufacturing a semiconductor substrate (hereinafter also referred to as the "semiconductor substrate manufacturing method of this disclosure"), which includes the etching method of this disclosure. Including the etching method of this disclosure means etching a workpiece using the etching solution of this disclosure in one or more embodiments. The etching method and conditions include etching methods and processing conditions (etching temperature, etching time) similar to those of the etching step of the etching method of this disclosure described above. The workpieces to be processed include the workpieces described above. The workpieces to be processed include the workpieces described above. The semiconductor substrate manufacturing method of the present disclosure is a method for manufacturing a semiconductor substrate, comprising, in one or more embodiments, a step of removing a silicon carbonitride (SiCN) layer from a substrate having a silicon carbonitride (SiCN) layer, wherein the substrate is a substrate for use in semiconductors. The semiconductor substrate manufacturing method of this disclosure can selectively etch SiCN while suppressing silicon oxide etching, thereby potentially improving the productivity of semiconductor substrates with improved quality. [Examples]

[0048] The present disclosure will be specifically described below with reference to examples, but the present disclosure is not limited in any way by these examples.

[0049] 1. Preparation of etching solution (Formulas 1-5) A silica solution was obtained by mixing an aqueous silica solution with an alkaline (TMAH) solution and heating it at 60°C for more than 12 hours. After adding a titanium compound (component B) to an 85% phosphoric acid solution (component A), a silica dissolving solution was added, followed by the addition of a fluorine compound (component D) to obtain etching solutions (pH=-1) of formulations 1 to 5 shown in Table 2. The amount of each component (mass %) in each etching solution is shown in Table 2.

[0050] The following components were used to prepare the etching solution. (Component A) Phosphoric acid [Phosphoric acid concentration 85%, manufactured by Phosphorus Chemical Industry Co., Ltd.] (Component B) TC-310 [Orgatics TC-310, manufactured by Matsumoto Fine Chemical Co., Ltd., dihydroxybis(lactate)titanium(IV)] TC-400 [“Orgatics TC-400” manufactured by Matsumoto Fine Chemical Co., Ltd., bis(isopropoxy)bis(N,N-di(2-hydroxyethyl)aminoethanolate)titanium(IV)] TC-510 [Orgatics TC-510 manufactured by Matsumoto Fine Chemical Co., Ltd., Tris((aminoethyl)aminoethanolate)mono(isopropoxy)titanium(IV)] TC-750 [“Orgatics TC-750” manufactured by Matsumoto Fine Chemical Co., Ltd., bis(isopropoxy)bis(2-ethylacetoacetate)titanium(IV)] (Component C) Silica [PL-1, 12% silica, manufactured by Fuso Chemical Industries Co., Ltd.] (Component D) Fluorine compound [49% hydrofluoric acid, manufactured by Hirota Chemical Industries Co., Ltd.] (Component E) Water [ultra pure water] (alkali) TMAH [Tetramethylammonium hydroxide 25%, manufactured by Seichem Asia Co., Ltd.]

[0051] Table 1 shows the structural formula of the titanium compound (component B) used in the preparation of the etching solution. [Table 1]

[0052] [Table 2]

[0053] 2. Method for measuring parameters [pH of etching solution] The pH value of the etching solution at 25°C was measured using a pH meter (manufactured by Toa DKK Co., Ltd.), and the value was obtained one minute after immersing the pH meter's electrode in the etching solution.

[0054] 3. Evaluation of etching solution The following etching tests were performed using each prepared etching solution, and the following evaluations were conducted.

[0055] 4. Evaluation of etching rate (Examples 1-1 to 1-4, Reference Example 1-1) [Etching test] Evaluation wafers (SiCN wafers, SiO2 wafers) measuring 1.5 × 1.5 cm were immersed in etching solutions (formulas 1-5) heated to 165°C. The immersion time for SiCN wafers was 5 minutes, and the immersion time for SiO2 wafers was 30 minutes. A constant temperature bath was used for the etching test. 100g of etching solution in a PFA (perfluoroalkoxyalkane) container was placed in the constant temperature bath and left to stand for 60 minutes to stabilize the temperature. Then, the evaluation wafer was placed in the etching solution and etching was started. After etching was complete, the evaluation wafer was removed, washed with water, and dried with air.

[0056] [Evaluation wafer] The evaluation SiCN wafer is a uniform blanket wafer in which a silicon carbonitride (SiCN) film is deposited on a silicon wafer. The evaluation SiO2 wafer is a uniform blanket wafer in which a silicon oxide (SiO2) film is deposited on a silicon wafer.

[0057] [Calculation of etching amount and etching rate] The film thickness of evaluation wafers before and after the etching test was measured by spectroscopic ellipsometry, and the difference was defined as the etching amount. The equipment and measurement conditions used are shown below. <Measurement conditions> Equipment: JAWoollam M-2000D Measurement temperature: room temperature (25℃) Measurement angles: 65°, 70°, 75° Sample size: 1.5cm square Acq. Time: 2.0 seconds Sample Thickness: 1.0mm The sample size must be larger than the diameter of the light source of the instrument. Therefore, a size of 1.0 cm square or larger is desirable, and 1.5 cm square or larger is preferable for ease of operation. The analysis was performed using CompleteEASE. The fitting model used for the SiCN film was Cauchy, and the fitting model used for the SiO2 film was SiO2-JAW+INTR_JAW. The method for calculating the thickness of the SiO2 film is shown below. The calculation was performed by fitting the measurement results to the aforementioned fitting model under the condition that the value of INTR_JAW is fixed at 1.0 nm. The method for calculating the thickness of a SiCN film is shown below. Film thickness fitting was performed on a blank wafer before etching. The parameters determined by the blank wafer fitting were fixed, and the wafer after etching was fitted to these parameters to calculate the film thickness. The etching rate was calculated by dividing the amount etched by the etching time. The calculation formula is shown below. Etching rate (nm / min) = Amount etched (nm) / Etching time (min) The etching rate results are shown in Table 3.

[0058] [Table 3]

[0059] As shown in Table 3, the etching solutions in Examples 1-1 to 1-4, which contain a titanium compound (component B), all exhibited good etching performance for SiCN and suppressed the etching rate of SiO2. Therefore, it is considered possible to achieve both good etching performance for SiCN and suppression of etching for SiO2.

[0060] 5. Evaluation of storage stability (Examples 2-1 to 2-4, Comparative Example 2-1) [Measurement of the average particle size of silica particles] After preparing the etching solutions (Formulas 1-5), the particle size of silica particles in the etching solutions was measured using a zetasizing machine after a specified storage period (shown in Table 4), and the Dv50 and Dv90 values ​​were calculated. Here, Dv50 is the maximum particle size below 50% of the sample volume, and Dv90 is the maximum particle size below 90% of the sample volume. The equipment and measurement conditions used are shown below. <Measurement conditions> Equipment: MALVERN Zetasizer Nano ZS Measurement type: Size Sample: SiO2 [Refractive index: 1.457, Absorbency: 0.000] Dispersion medium: Phosphorous acid (85%) [Temperature: 25℃, Viscosity: 40.0cP, RI: 1.430] Temperature: 25℃ [Equilibration time: 120 seconds] Cell: Polystyrene cell Measurement angle: 175° Number of executions: 10 Execution time: 5 seconds Number of measurements: 2 The results for silica particle size (Dv50 and Dv90) are shown in Table 4.

[0061] [Table 4]

[0062] As shown in Table 4, the etching solutions of Examples 2-1 to 2-4, which contained phosphoric acid (component A) and a specific titanium compound (component B), showed improved storage stability and suppressed silica particle size increase even over longer storage periods compared to Comparative Example 2-1, which did not contain the specific titanium compound (component B). [Industrial applicability]

[0063] The etching solution of this disclosure is useful in a method for manufacturing semiconductor substrates for high density or high integration.

Claims

1. An etching solution comprising the following components A, B, and C. Component A: Phosphate Component B: Titanium compound represented by the following formula (I) Component C: Silica 【Chemistry 1】 In the above formula (I), R 1 R is a hydrogen atom or a saturated alkyl group having 1 to 10 carbon atoms, and n is an integer from 0 to 2. In the above formula (I), R 2 This is an alkyl group having 2 to 20 carbon atoms and having at least one selected from an ester group, a carboxyl group, a ketone group, a hydroxyl group, and an amino group, wherein at least one carbon atom of the alkyl group may be substituted with S, N, or O.

2. The etching solution according to claim 1, which is an etching solution for etching silicon carbonitride (SiCN).

3. The etching solution according to claim 1, wherein the mass ratio A / B of component A to component B is 5 or more and 8500 or less.

4. In the above formula (I), R 1 The etching solution according to claim 1, wherein n comprises a hydrogen atom or an isopropyl group, and n is an integer from 1 to 2.

5. In the above formula (I), R 2 The etching solution according to claim 1, comprising a carboxyethyl group, a bis(hydroxyethyl)aminoethyl group, a bis(aminoethyl)aminoethyl group, or an ethoxybutyldione group.

6. The etching solution according to claim 1, wherein component B is at least one selected from dihydroxybis(acetact)titanium (IV), dihydroxybis(lactate)titanium (IV), bis(isopropoxy)bis(N,N-di(2-hydroxyethyl)aminoethanolate)titanium (IV), tris((aminoethyl)aminoethanolate)mono(isopropoxy)titanium (IV), and bis(isopropoxy)bis(2-ethylacetacetate)titanium (IV).

7. The etching solution according to claim 1, further comprising a fluorine compound (component D).

8. The etching solution according to claim 7, wherein component D is at least one selected from hydrogen fluoride, monofluorophosphate, hexafluorophosphate, and ammonium fluoride.

9. The etching solution according to claim 1, further comprising water (component E).

10. The etching solution according to claim 1, wherein the amount of component A is 70% by mass or more and 95% by mass or less.

11. An etching method comprising the step of etching silicon carbonitride (SiCN) using an etching solution according to any one of claims 1 to 10.

12. A method for manufacturing a semiconductor substrate, comprising the etching method described in claim 11.

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