Etching solution for silicon, etching method, and method for manufacturing semiconductor substrate

Abstract

In one aspect, provided is an etching solution for silicon capable of suppressing the formation of micro pyramids which lead to deterioration of the surface roughness of a silicon substrate.　One embodiment of the present disclosure relates to an etching solution for silicon, comprising a primary diamine (Component A) and a quaternary ammonium salt (Component B), wherein the content of Component B is 12 mass% or more.

Description

Etching solution for silicon, etching method, and method for manufacturing semiconductor substrates

[0001] This disclosure relates to an etching solution for silicon, an etching method, and a method for manufacturing a semiconductor substrate.

[0002] In the manufacturing process of semiconductor devices using silicon, wet etching and dry etching are used for purposes such as processing and foreign matter removal. For example, etching can be used to fabricate complex three-dimensional MEMS (Micro Electro Mechanical Systems) devices and to thin silicon substrates (silicon wafers).

[0003] Conventional wet etching uses alkaline aqueous solutions. For example, Japanese Patent Publication No. 6577446 (Patent Document 1) proposes a composition useful for etching semiconductor substrates, comprising, in terms of effective etching amount, about 25 to 86% by mass of water, about 0 to 60% by mass of a water-miscible organic solvent, about 1 to 30% by mass of a quaternary ammonium compound, about 1 to 50% by mass of an amine compound selected from monoethanolamine, secondary amines, tertiary amines and mixtures thereof, about 0 to 5% by mass of a buffer, and about 0 to 15% by mass of a corrosion inhibitor, which gives a sigma shape profile. Japanese Patent Application Publication No. 2023-152834 (Patent Document 2) proposes a silicon etching solution containing quaternary ammonium hydroxide (component A), amines (component B), and a solvent (component C), wherein component B is at least one selected from polyamines and alkanolamines.

[0004] This disclosure relates, in one embodiment, to an etching solution for silicon comprising a primary diamine (component A) and a quaternary ammonium salt (component B), wherein the content of component B is 12% by mass or more.

[0005] This disclosure relates, in one embodiment, to an etching method that includes the step of etching silicon using an etching solution of this disclosure.

[0006] This disclosure relates, in one embodiment, to a method for manufacturing a semiconductor substrate, which includes a step of etching a silicon-containing substrate using an etching solution of this disclosure.

[0007] Figure 1A is a photograph showing an example of the appearance of a silicon substrate after etching using the etching solution of Example 1, and Figure 1B is a photograph showing an example of the appearance of a silicon substrate after etching using the etching solution of Comparative Example 1.

[0008] In recent years, the semiconductor field has seen increasing integration, leading to demands for more complex and miniaturized wiring, and thus requiring even higher precision in etching technology. In recent years, the demands on the surface quality of silicon substrates have become increasingly stringent, and etching methods that can suppress deterioration of flatness, surface roughness, and haze are desired. Alkaline etching solutions are known to have etching rates that depend on the crystal orientation of the silicon substrate. For example, when the 100th crystal orientation plane of silicon, which is mainly used as the etching surface, is wet-etched with an alkaline etching solution, a problem arises in that protrusions (also called micropyramids) are generated, leading to deterioration of surface roughness. It is thought that micropyramids are generated due to differences in etching rates depending on the 100th, 110th, and 111th crystal orientation planes of silicon.

[0009] Therefore, this disclosure provides an etching solution for silicon, an etching method, and a method for manufacturing a semiconductor substrate that suppress the generation of micropyramids, which lead to deterioration of the surface roughness of the silicon substrate.

[0010] According to this disclosure, in one embodiment, an etching solution for silicon can be provided that suppresses the generation of micropyramids, which lead to deterioration of the surface roughness of the silicon substrate.

[0011] This disclosure is based on the finding that, in one embodiment, by using an etching solution containing a primary diamine (component A) and a quaternary ammonium salt (component B), wherein the content of component B is above a predetermined value, for etching 100 crystal orientation planes of silicon, the generation of micropyramids can be suppressed without impairing the etching rate, for example, compared to the case of combining monoethanolamine and a quaternary ammonium salt.

[0012] In one embodiment, this disclosure relates to an etching solution for silicon (hereinafter also referred to as "the etching solution of this disclosure") comprising a primary diamine (component A) and a quaternary ammonium salt (component B), wherein the content of component B is 12% by mass or more.

[0013] The etching solution of this disclosure can suppress the generation of micropyramids, which can lead to deterioration of the surface roughness of a silicon substrate.

[0014] The etching solution of this disclosure can be used in one or more embodiments for anisotropic etching such as etching of silicon substrates (wafers), etching in thinning of silicon substrates (wafers), etching in micromachining (MEMS) technology, and etching in solar cell manufacturing.

[0015] Although the detailed mechanism of the effect of this disclosure is not clear, it is presumed to be as follows: When the 100-plane (Si(100)) of silicon is etched with an alkali, pyramidal protrusions called micropyramids are generated. As etching progresses, the micropyramids grow and increase, and the surface roughness deteriorates as pyramidal irregularities are formed on the surface. These micropyramids are composed of the 100-plane (Si(100)) at the base, the 110-plane (Si(110)) at the edges, and the 111-plane (Si(111)) at the sides, with the apex of the pyramid being masked by foreign matter, etc. It is thought that micropyramids are generated because general alkaline etching solutions have different etching rates for each of the Si(100), Si(110), and Si(111) crystal planes. However, this disclosure hypothesizes that by using a primary diamine (component A) and a specific amount of a quaternary ammonium salt (component B), the difference in etching rates between the Si(100), Si(110), and Si(111) crystal planes can be reduced, thereby suppressing the formation of micropyramids. However, this disclosure does not have to be interpreted as being limited to these mechanisms.

[0016] [Component A: Primary Diamine] The etching solution of this disclosure contains a primary diamine (hereinafter also referred to as "Component A"). Component A may be one type or a combination of two or more types. In one or more embodiments, the primary diamine in this disclosure is a primary diamine having two nitrogen atoms.

[0017] From the viewpoint of suppressing the formation of micropyramids, the number of carbon atoms in component A is preferably 3 to 6, more preferably 3 to 5, and even more preferably 3 to 4.

[0018] As component A, from the viewpoint of suppressing the formation of micropyramids, the compound represented by (II) below is preferred. In formula (II), R 5 R is a hydrogen or hydroxyl group, 6 R is a straight-chain alkylene group having 1 to 4 carbon atoms. 6 The number of carbon atoms is preferably 1 or more and 3 or less, and more preferably 1 or 2, from the viewpoint of suppressing the formation of micropyramids.

[0019] As component A, in one or more embodiments, from the viewpoint of suppressing the generation of micropyramids, the compound represented in (II) above is preferred, for example, at least one selected from 1,3-diamino-2-propanol, 1,4-diamino-2-butanol, 1,4-diamino-3-butanol, and 1,3-propanediamine is preferred. As component A, in one or more embodiments, from the viewpoint of low volatility and ease of handling, primary diamines having hydroxyl groups are recommended, for example, at least one selected from 1,3-diamino-2-propanol, 1,4-diamino-2-butanol, and 1,4-diamino-3-butanol is preferred, and at least one selected from 1,3-diamino-2-propanol and 1,4-diamino-2-butanol is more preferred.

[0020] From the perspective of suppressing the generation of micro-pyramids, the content of component A in the etching solution of the present disclosure is preferably 5% by mass or more, more preferably 10% by mass or more, still more preferably 15% by mass or more, and from the perspective of productivity, it is preferably 40% by mass or less, more preferably 35% by mass or less, and still more preferably 30% by mass or less. More specifically, the content of component A in the etching solution of the present disclosure is preferably 5% by mass or more and 40% by mass or less, more preferably 10% by mass or more and 35% by mass or less, and still more preferably 15% by mass or more and 30% by mass or less. When component A is a combination of two or more kinds, the content of component A refers to their total content.

[0021] [Component B: Quaternary ammonium salt] The etching solution of the present disclosure contains a quaternary ammonium salt (hereinafter also referred to as "component B"). As component B, in one or more embodiments, from the perspective of suppressing the generation of micro-pyramids, aliphatic quaternary ammonium salts and quaternary ammonium salts having a hydroxyalkyl group can be mentioned. Component B may be one kind or a combination of two or more kinds.

[0022] As component B, in one or more embodiments, the compound represented by the following formula (I) can be mentioned. In the above formula (I), R 1 、R 2 、R 3 and R 4 are each independently at least one selected from a methyl group, an ethyl group, a propyl group, a hydroxymethyl group, a hydroxyethyl group, and a hydroxypropyl group. In the above formula (I), R 1 、R 2 、R 3 and R 4 are preferably each independently at least one selected from a methyl group, an ethyl group, and a propyl group from the perspective of suppressing the generation of micro-pyramids, more preferably a methyl group or an ethyl group, and still more preferably a methyl group.

[0023] The compound represented by formula (I) above is a salt consisting of a quaternary ammonium cation and a hydroxide, and examples include at least one selected from tetramethylammonium hydroxide (TMAH), tetraethylammonium hydroxide (TEAH), tetrapropylammonium hydroxide, 2-hydroxyethyltrimethylammonium hydroxide (choline), 2-hydroxyethyltriethylammonium hydroxide, 2-hydroxyethyltripropylammonium hydroxide, 2-hydroxypropyltrimethylammonium hydroxide, 2-hydroxypropyltriethylammonium hydroxide, 2-hydroxypropyltripropylammonium hydroxide, dimethylbis(2-hydroxyethyl)ammonium hydroxide, diethylbis(2-hydroxyethyl)ammonium hydroxide, dipropylbis(2-hydroxyethyl)ammonium hydroxide, tris(2-hydroxyethyl)methylammonium hydroxide, tris(2-hydroxyethyl)ethylammonium hydroxide, tris(2-hydroxyethyl)propylammonium hydroxide, tetrakis(2-hydroxyethyl)ammonium hydroxide, and tetrakis(2-hydroxypropyl)ammonium hydroxide.

[0024] As for component B, from the viewpoint of suppressing the formation of micropyramids, at least one selected from tetramethylammonium hydroxide (TMAH), tetraethylammonium hydroxide (TEAH), and dimethylbis(2-hydroxyethyl)ammonium hydroxide is preferred, and at least one of tetramethylammonium hydroxide (TMAH) and dimethylbis(2-hydroxyethyl)ammonium hydroxide is more preferred.

[0025] From the viewpoint of productivity, the content of component B in the etching solution of this disclosure is preferably 12% by mass or more, 13% by mass or more, or 14% by mass or more, more preferably 15% by mass or more, even more preferably 17% by mass or more, and even more preferably 20% by mass or more. From the viewpoint of suppressing the generation of micropyramids, it is preferably 40% by mass or less, more preferably 35% by mass or less, and even more preferably 30% by mass or less. More specifically, the content of component B in the etching solution of this disclosure is preferably 12% by mass or more and 40% by mass or less, 13% by mass or more and 40% by mass or less, more preferably 15% by mass or more and 40% by mass or less, even more preferably 17% by mass or more and 35% by mass or less, and even more preferably 20% by mass or more and 30% by mass or less. When component B is a combination of two or more types, the content of component B refers to the total content of those types.

[0026] The total content of component A and component B in the etching solution of this disclosure is preferably 20% by mass or more, more preferably 33% by mass or more, even more preferably 34% by mass or more, and even more preferably 35% by mass or more, from the viewpoint of suppressing the generation of micropyramids, and from the viewpoint of productivity, it is preferably 80% by mass or less, and more preferably 60% by mass or less. More specifically, the total content of component A and component B is preferably 20% by mass or more and 80% by mass or less, and more preferably 33% by mass or more and 60% by mass or less.

[0027] In the etching solution of this disclosure, the mass ratio A / B of component A to component B is preferably 0.6 or higher, more preferably 0.9 or higher, and preferably 1.8 or lower, and more preferably 1.5 or lower, from the viewpoint of suppressing the generation of micropyramids. More specifically, the mass ratio A / B is preferably 0.6 or higher and 1.8 or lower, or 0.9 or higher and 1.8 or lower, and more preferably 0.9 or higher and 1.5 or lower. In this disclosure, the mass ratio A / B is a value calculated by dividing the mass (content) of component A by the mass (content) of component B.

[0028] [Water] In one or more embodiments, the etching solution of this disclosure may further contain water as a medium. Examples of water include distilled water, deionized water, pure water, and ultrapure water. From the viewpoint of productivity, the water content in the etching solution of this disclosure is preferably 20% by mass or more, more preferably 30% by mass or more, and even more preferably 40% by mass or more. From the viewpoint of suppressing the generation of micropyramids, it is preferably 75% by mass or less, more preferably 70% by mass or less, and even more preferably 65% ​​by mass or less. More specifically, the water content in the etching solution of this disclosure is preferably 20% by mass or more and 75% by mass or less, more preferably 30% by mass or more and 70% by mass or less, and even more preferably 40% by mass or more and 65% by mass or less.

[0029] From the viewpoint of suppressing the generation of micropyramids, the total content of component A, component B, and water in the etching solution of this disclosure is preferably 90% by mass or more, more preferably 95% by mass or more, and even more preferably 100% by mass.

[0030] In one or more embodiments, the mass ratio of component A to water in the etching solution of this disclosure [content of component A / content of water] is preferably 0.01 or higher, more preferably 0.1 or higher, and even more preferably 0.2 or higher, from the viewpoint of suppressing the generation of micropyramids. Furthermore, in one or more embodiments, from the viewpoint of suppressing the generation of micropyramids, it is preferably 2 or less, more preferably 1 or less, and even more preferably 0.8 or less. More specifically, in one or more embodiments, the mass ratio of component A to water [content of component A / content of water] is preferably 0.01 or higher and 2 or less, more preferably 0.1 or higher and 1 or less, and even more preferably 0.2 or higher and 0.8 or less. In one or more embodiments, the mass ratio of component B to water in the etching solution of this disclosure [content of component B / content of water] is preferably 0.01 or higher, more preferably 0.1 or higher, and even more preferably 0.2 or higher, from the viewpoint of suppressing the generation of micropyramids. Furthermore, in one or more embodiments, from the viewpoint of suppressing the generation of micropyramids, it is preferably 2 or less, more preferably 1 or less, and even more preferably 0.5 or less. More specifically, the mass ratio of component B to water [content of component B / content of water] is preferably 0.01 or more and 2 or less, more preferably 0.1 or more and 1 or less, and even more preferably 0.2 or more and 0.5 or less in one or more embodiments.

[0031] [Component C: Nonionic Water-Soluble Polymer] In one or more embodiments, the etching solution of this disclosure may further contain a nonionic water-soluble polymer (hereinafter also referred to as "Component C") from the viewpoint of adjusting the dissolution rate. Component C may be one type or a combination of two or more types. In this disclosure, "water-soluble" means having a solubility of 0.5 g / 100 mL or more in water (20°C), preferably 2 g / 100 mL or more. From the viewpoint of adjusting the dissolution rate, Component C is preferably a nonionic water-soluble polymer having an alkylene oxy group in the molecule in one or more embodiments. Examples of alkylene oxy groups include at least one selected from ethylene oxy group (EO) and propylene oxy group (PO), and EO is preferred from the viewpoint of adjusting the dissolution rate. Examples of Component C include polyethylene glycol (PEG) and polypropylene glycol. If the etching solution of this disclosure contains component C, the content of component C in the etching solution of this disclosure is preferably 0.0001% by mass or more, more preferably 0.0005% by mass or more, even more preferably 0.001% by mass or more, and from the viewpoint of adjusting the dissolution rate, preferably 0.5% by mass or less, more preferably 0.1% by mass or less, and even more preferably 0.01% by mass or less. If component C is a combination of two or more types, the content of component C refers to the total content of those types.

[0032] [Component D: Chelating Agent] From the perspective of removing metal foreign substances, the etching solution of the present disclosure may further contain a chelating agent (hereinafter also referred to as "Component D"). Component D may be one type or a combination of two or more types. In one or more embodiments, Component D is a compound having at least two acid groups selected from carboxy groups and phosphonic acid groups, and from the perspective of removing metal foreign substances, it is preferably a compound having 4 or fewer of the above acid groups. Examples of Component D include at least one selected from maleic acid, picolinic acid, and ethylenediaminetetraacetic acid (EDTA). From the perspective of removing metal foreign substances, at least one selected from maleic acid and picolinic acid is preferred. When the etching solution of the present disclosure contains Component D, the content of Component D in the etching solution of the present disclosure is preferably 0.01% by mass or more, more preferably 0.05% by mass or more, still more preferably 0.1% by mass or more from the perspective of removing metal foreign substances, and preferably 5.0% by mass or less, more preferably 2.5% by mass or less, still more preferably 1.0% by mass or less from the perspective of adjusting the dissolution rate. When Component D is a combination of two or more types, the content of Component D refers to their total content.

[0033] [Inorganic Alkali (Component E)] In one or more embodiments, the etching solution of the present disclosure may further contain an inorganic alkali (hereinafter also referred to as "Component E") from the perspective of suppressing deterioration of surface roughness. Component E may be one type or a combination of two or more types. Examples of Component E include ammonia; alkali metal hydroxides such as potassium hydroxide and sodium hydroxide. When the etching solution of the present disclosure contains Component E, the content of Component E in the etching solution of the present disclosure is preferably 0.01% by mass or more, more preferably 0.1% by mass or more, still more preferably 0.5% by mass or more from the perspective of adjusting the dissolution rate and suppressing deterioration of surface roughness, and preferably 50% by mass or less, more preferably 30% by mass or less, still more preferably 20% by mass or less from the same perspective. When Component E is a combination of two or more types, the content of Component E refers to their total content.

[0034] [Other Components] The etching solution of the present disclosure may further contain or be formulated with other components as long as the effects of the present disclosure are not impaired. Examples of other components include alkali agents other than components A, B, and E, pH adjusters other than components A, B, and E, water-soluble polymers other than component C, surfactants, high-temperature stabilizers, solubilizers, preservatives, rust inhibitors, bactericides, antibacterial agents, antioxidants, defoamers, and the like.

[0035] In one or more embodiments, the etching solution of the present disclosure can be substantially free of amine compounds selected from monoethanolamine, secondary amines, tertiary amines, and mixtures thereof. For example, the content of amine compounds selected from monoethanolamine, secondary amines, tertiary amines, and mixtures thereof in the etching solution of the present disclosure is preferably less than 1% by mass, more preferably 0.1% by mass or less, and still more preferably 0% by mass.

[0036] [Method for Producing Etching Solution] In one or more embodiments, the etching solution of the present disclosure can be obtained by formulating component A, component B, water, and, if necessary, any of the above-mentioned optional components (component C, component D, component E, other components). Therefore, in one aspect, the present disclosure relates to a method for producing an etching solution (hereinafter, also referred to as "the method for producing the etching solution of the present disclosure") including a step of formulating component A, component B, water, and, if necessary, any of the above-mentioned optional components (component C, component D, component E, other components) (hereinafter, also referred to as "the formulation step"). In the present disclosure, "formulating" includes mixing component A, component B, water, and, if necessary, any of the above-mentioned optional components (component C, component D, component E, other components) simultaneously or sequentially. The mixing order may not be particularly limited. The formulation can be performed, for example, using a mixer such as a homomixer, homogenizer, ultrasonic disperser, and wet ball mill. In the method for producing the etching solution of the present disclosure, the preferable formulation amounts of each component can be the same as the preferable content amounts of each component in the etching solution of the present disclosure described above.

[0037] In this disclosure, "content of each component in the etching solution" means, in one or more embodiments, the content of each component in the etching solution at the time of use in the etching process, i.e., at the start of use in the etching process. In one or more embodiments, the content of each component in the etching solution composition of this disclosure can be considered as the amount of each component blended in the etching solution composition of this disclosure. However, the blended amount and content may differ when affected by neutralization.

[0038] Embodiments of the etching solution of this disclosure may be a so-called one-component type, in which all components are supplied to the market in a pre-mixed state, or a so-called two-component type, in which the components are mixed at the time of use.

[0039] In one or more embodiments, the etching solution of this disclosure is preferably a neutral or alkaline etching solution. For example, the pH of the etching solution of this disclosure is preferably 9 or higher, more preferably 10 or higher, and even more preferably 12 or higher, from the viewpoint of suppressing the generation of micropyramids. 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.

[0040] The etching solution of this disclosure may be stored and supplied in a concentrated state, to the extent that its stability is not impaired. This is preferable in that it can reduce manufacturing and transportation costs. This concentrated solution can then be used in the etching process after being appropriately diluted with water or the like as needed. A dilution ratio of 1.2 to 100 times is preferred.

[0041] The etching solution of this disclosure can be applied in one or more embodiments to anisotropic etching such as etching of silicon substrates (wafers), etching in micromachining (MEMS) technology, etching in solar cell manufacturing, and etching in thinning of silicon substrates (wafers). Etching using the etching solution of this disclosure can be used in one or more embodiments in a slicing process, lapping process, polishing process, CMP process, rinsing process, heat treatment process, cleaning process, and photoresist process.

[0042] [Kit] In one embodiment, 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 a kit (two-component etching solution) which contains a solution containing component A (first solution) and a solution containing component B (second solution) in an unmixed state, and which is mixed at the time of use. After the first and second solutions are mixed, they may be diluted with water as needed. The first or second solution may contain all or part of the water used to prepare the etching solution. The first and second solutions may optionally contain the above-mentioned optional components (component C, component D, component E, and other components). According to the Kit of this Disclosure, it is possible to manufacture an etching solution for silicon that can suppress the generation of protrusions and micropyramids due to etching rate differences dependent on the crystal orientation of the substrate, which leads to deterioration of the surface roughness of the silicon substrate.

[0043] [Workpiece to be etched] In one or more embodiments, the workpiece to be etched using the etching solution of this disclosure is silicon such as single-crystal silicon, polycrystalline silicon, polysilicon, and patterned silicon. Among these, at least one selected from single-crystal silicon, polycrystalline silicon, and polysilicon is preferred, at least one of single-crystal silicon and polysilicon is more preferred, single-crystal silicon or polysilicon with a crystal orientation of 100 planes is even more preferred, and single-crystal silicon with a crystal orientation of 100 planes is even more preferred. Examples of workpieces include silicon substrates (silicon wafers), silicon substrates having a silicon oxide film and a silicon nitride film, and silicon-containing substrates such as silicon-patterned structures.

[0044] [Etching Method] In one embodiment, this disclosure relates to an etching method (hereinafter also referred to as "the etching method of this disclosure") which includes a step of etching silicon using the etching solution of this disclosure or a mixture of an existing chemical agent and the etching solution of this disclosure (hereinafter also referred to as "the etching step"). By using the etching method of this disclosure, the generation of micropyramids can be suppressed, thereby improving the productivity of semiconductor substrates with improved quality. Examples of existing chemical agents include ammonia, potassium hydroxide, SC-1 (an aqueous solution containing ammonia and hydrogen peroxide), etc. The mixture can be prepared in one or more embodiments by compounding an existing chemical agent and the etching solution of this disclosure. For example, in one or more embodiments, the mixture can be obtained by adding ammonia, hydrogen peroxide and the etching solution of this disclosure to ultrapure water. In one or more embodiments, the mixture can be obtained by mixing SC-1 prepared by mixing ultrapure water, ammonia and hydrogen peroxide with the etching solution of this disclosure. The etching solution of this disclosure used in preparing the aforementioned mixture is preferably formulated such that the concentration of component A in the mixture is 5% by mass or more and 40% by mass or less.

[0045] In one or more embodiments, the etching process is an etching process for a silicon substrate (wafer), an etching process in micromachining (MEMS) technology, an anisotropic etching process such as etching in solar cell manufacturing, or an etching process for thinning a silicon substrate (wafer). In one or more embodiments, the etching process includes etching at least a portion of the silicon substrate to reduce the thickness of the silicon substrate.

[0046] In one or more embodiments, the etching step includes contacting the workpiece described above with the etching solution of the present disclosure. Examples of etching methods or methods for contacting the workpiece with the etching solution of the present disclosure in the etching step include immersion etching and single-wafer etching.

[0047] In the etching process, the temperature of the etching solution used (etching temperature) is preferably 30°C or higher, more preferably 40°C or higher, and even more preferably 50°C or higher, from the viewpoint of solubility, and from the viewpoint of etching solution life, it is preferably 100°C or lower, more preferably 90°C or lower, and even more preferably 85°C or lower. More specifically, the temperature of the etching solution used is preferably 30°C to 100°C, more preferably 40°C to 90°C, and even more preferably 50°C to 85°C. In the etching process, the etching time (etching treatment time) can be appropriately set according to the structure, material, and etching treatment conditions of the silicon substrate.

[0048] In one or more embodiments, the etching method of this disclosure may include, in addition to the etching step, a cleaning step, a rinsing step, a drying step, etc. The cleaning step and / or rinsing step may be performed before, after, or both (before and after) the etching step. The drying step may be performed after the cleaning step and / or rinsing step. For example, the etching method of this disclosure may include, after the etching step, a rinsing step in which the silicon after etching is rinsed with water or the like, and a drying step in which the silicon after rinsing is dried.

[0049] [Method for Manufacturing Semiconductor Substrates] The etching solution and etching method of the present disclosure described above can be suitably used for manufacturing semiconductor substrates. Accordingly, in one embodiment, the present disclosure relates to a method for manufacturing semiconductor substrates (hereinafter also referred to as "the semiconductor substrate manufacturing method of the present disclosure") which includes a step of etching a silicon-containing substrate (workpiece) using the etching solution of the present disclosure (hereinafter also referred to as "etching step"). The etching method and conditions in the etching step of the semiconductor substrate manufacturing method of the present disclosure include the same etching treatment method and treatment conditions (etching temperature, etching time) as in the etching step of the etching method of the present disclosure described above. The workpiece can be the workpiece described above.

[0050] This disclosure further relates to one or more embodiments described below: <1> An etching solution for silicon comprising a primary diamine (component A) and a quaternary ammonium salt (component B), wherein the content of component B is 12% by mass or more. <2> The etching solution according to <1>, wherein the number of carbon atoms of component A is 3 to 6, 3 to 5, or 3 to 4. <3> The etching solution according to <1> or <2>, wherein component B is a compound represented by the following formula (I). In the above formula (I), R 1 , R 2 , R 3 and R 4Each of these groups is independently at least one selected from a methyl group, an ethyl group, a propyl group, a hydroxymethyl group, a hydroxyethyl group, and a hydroxypropyl group. <4> The etching solution according to any one of <1> to <3>, wherein component B is at least one selected from tetramethylammonium hydroxide (TMAH), tetraethylammonium hydroxide (TEAH), tetrapropylammonium hydroxide, 2-hydroxyethyltrimethylammonium hydroxide (choline), 2-hydroxyethyltriethylammonium hydroxide, 2-hydroxyethyltripropylammonium hydroxide, 2-hydroxypropyltrimethylammonium hydroxide, 2-hydroxypropyltripropylammonium hydroxide, dimethylbis(2-hydroxyethyl)ammonium hydroxide, diethylbis(2-hydroxyethyl)ammonium hydroxide, dipropylbis(2-hydroxyethyl)ammonium hydroxide, tris(2-hydroxyethyl)methylammonium hydroxide, tris(2-hydroxyethyl)ethylammonium hydroxide, tris(2-hydroxyethyl)propylammonium hydroxide, tetrakis(2-hydroxyethyl)ammonium hydroxide, and tetrakis(2-hydroxypropyl)ammonium hydroxide. <5> The etching solution according to any one of <1> to <4>, wherein component A is a primary diamine having a hydroxyl group. <6> The etching solution according to any one of <1> to <5>, wherein component A is a compound represented by (II) below. In formula (II), R 5 R is a hydrogen or hydroxyl group, 6<7> The etching solution according to any one of <1> to <6>, wherein component A is at least one selected from 1,3-diamino-2-propanol, 1,4-diamino-2-butanol, 1,4-diamino-3-butanol, and 1,3-propanediamine. <8> The etching solution according to any one of <1> to <7>, wherein the content of component B is 12% by mass or more, 13% by mass or more, 14% by mass or more, 15% by mass or more, 17% by mass or more, or 20% by mass or more, or 40% by mass or less, 35% by mass or less, or 30% by mass or less, or 12% by mass or more and 40% by mass or less, 13% by mass or more and 40% by mass or less, 14% by mass or more and 40% by mass or less, 15% by mass or more and 40% by mass or less, 17% by mass or more and 35% by mass or less, or 20% by mass or more and 30% by mass or less. <9> The etching solution according to any one of <1> to <8>, wherein the content of component A is 5% by mass or more, 10% by mass or more, or 15% by mass or more, or 40% by mass or less, 35% by mass or less, or 30% by mass or less, or 5% by mass or more and 40% by mass or less, 10% by mass or more and 35% by mass or less, or 15% by mass or more and 30% by mass or less. <10> The etching solution according to any one of <1> to <9>, wherein the total content of component A and component B in the etching solution is 20% by mass or more, 33% by mass or more, 34% by mass or more, or 35% by mass or more, or 80% by mass or less, or 60% by mass or less, or 20% by mass or more and 80% by mass or less, or 33% by mass or more and 60% by mass or less. <11> An etching solution according to any one of <1> to <10>, wherein the mass ratio A / B of component A to component B is 0.6 or more, or 0.9 or more, or 1.8 or less, or 1.5 or less, or 0.6 or more and 1.8 or less, 0.9 or more and 1.8 or less, or 0.9 or more and 1.5 or less. <12> An etching solution according to any one of <1> to <11>, further comprising water. <13> An etching solution according to <12>, wherein the water content is 20% by mass or more and 75% by mass or less.<14> The etching solution according to <12> or <13>, wherein the mass ratio of component A to water [content of component A / content of water] is 0.01 or more, 0.1 or more, or 0.2 or more, or 2 or less, 1 or less, or 0.8 or less, or 0.01 or more and 2 or less, 0.1 or more and 1 or less, or 0.2 or more and 0.8 or less. <15> The etching solution according to any one of <12> to <14>, wherein the mass ratio of component B to water [content of component B / content of water] is 0.01 or more, 0.1 or more, or 0.2 or more, or 2 or less, 1 or less, or 0.5 or less, or 0.01 or more and 2 or less, 0.1 or more and 1 or less, or 0.2 or more and 0.5 or less. <16> The etching solution according to any one of <1> to <15>, wherein the pH of the etching solution is 9 or more, 10 or more, or 12 or more. <17> An etching method comprising the step of etching silicon using an etching solution described in any of <1> to <16>. <18> A method for manufacturing a semiconductor substrate comprising the step of etching a silicon-containing substrate using an etching solution described in any of <1> to <16>.

[0051] 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.

[0052] 1. Preparation of Etching Solutions (Examples 1-7 and Comparative Examples 1-2) Etching solutions for Examples 1-7 and Comparative Examples 1-2 were prepared by mixing the components shown in Table 1 with water (ultrapure water). The pH of the prepared etching solutions was 14. The content of each component in Table 1 is the content of each component (mass %) at the time of use of the etching solution. The water content is the residue obtained by subtracting component A or non-component A and component B from the total amount of etching solution (100 mass%). The water content also includes the water content contained in the aqueous solution of component B.

[0053] The following components were used to prepare the etching solution: (Component A) 1,3-diamino-2-propanol [manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.] 1,3-propanediamine [manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.] 1,4-diamino-2-butanol [manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.] (Non-Component A) MEA: 2-hydroxyethylamine [manufactured by Tokyo Chemical Industry Co., Ltd.] (Component B) TMAH・5H2O [tetramethylammonium hydroxide pentahydrate, Fujifilm Wako Pure Chemical Industries, Ltd.] TEAH [tetraethylammonium hydroxide, 35% by mass aqueous solution, manufactured by Seichem Japan LLC] Dimethylbis(2-hydroxyethyl)ammonium hydroxide [50% by mass aqueous solution, manufactured by Shikoku Chemicals Co., Ltd.]

[0054] [pH of the 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 is the value obtained one minute after immersing the pH meter electrode in the etching solution.

[0055] 2. Evaluation of Etching Solutions Etching was performed with each etching solution under the following conditions, and the presence or absence of micropyramid formation was observed and evaluated as described below.

[0056] [Etching Method] A silicon substrate with 100 crystal orientations as shown below was cut into 4 x 2 cm pieces using a diamond cutter to prepare test specimens. Then, the entire surface of the test specimen was immersed in acetone for 1 minute, followed by rinsing with ultrapure water. Next, the entire surface of the test specimen was immersed in ammonium hydrofluoride diluted to 1% with ultrapure water for 1 minute, followed by rinsing with ultrapure water, and then dried with an air blower. 30 g of the prepared etching solution was weighed into a 30 ml PE plastic container, and the entire surface of the test specimen was immersed in it. The specimen was then placed in a constant temperature bath (ESPEC, model: PU-4J) set to 60°C for 1 hour to perform etching. Next, the test specimen was removed from the constant temperature bath, rinsed with ultrapure water, and dried with an air blower. [Silicon Substrate] The silicon substrate used is as follows. Type: (100) Single-sided mirror wafer (single-crystal silicon with 100 crystal orientations) Resistance: ≤1Ω·cm Thickness: 1000±25μm Orientation flat: Notched Particles: Not specified

[0057] [Etching Rate] The etching rate was determined by calculating the etched film thickness from the weight change of the substrate before and after etching the crystal plane (100 planes). The results are shown in Table 1. Etching rate (nm / min) = (Weight of substrate before etching (g) - Weight of substrate after etching (g)) / Density (g / cm³) 3 ) / Area of ​​the front and back surfaces of the circuit board (cm²) 2 ) / Etching time (minutes) × 10 7 Density of a silicon substrate with crystal orientation 100: 2.33 g / cm³ 3

[0058] [Micropyramid Observation Conditions] The appearance of the silicon substrate with 100 crystal orientations after etching was observed as follows. Using a Keyence VHX-7100 microscope, the non-mirror surface after etching was observed at 100x magnification using differential interference contrast. Here, Figure 1 shows an example of a photograph of the surface appearance of the silicon substrate etched using the etching solutions of Example 1 and Comparative Example 1. As shown in Figure 1A, no micropyramids were observed on the surface of the silicon substrate etched using the etching solution of Example 1. On the other hand, as shown in Figure 1B, multiple micropyramids (areas that appear as black spots in Figure 1B) were observed on the surface of the silicon substrate etched using the etching solution of Comparative Example 1. [Micropyramid Evaluation Method] Ten fields of view were checked, and if there was even one micropyramid in a field of view, it was counted. 0 to 1 field of view was classified as A, 2 fields as B, 3 to 5 fields as C, and 6 or more fields as D. The results are shown in Table 1.

[0059] [Volatility] The amount of component A after heating each etching solution at the etching temperature (60°C) shown in Table 1 for 120 minutes was analyzed using NMR, and the reduction rate of component A due to heating was calculated. The reduction rate is an indicator of how much component A has volatilized (decreased) from the amount before heating (initial), and was calculated using the following formula: Reduction rate (%) = (Amount of component A before heating (mass%) - Amount of component A after heating (mass%)) / (Amount of component A before heating (mass%)) × 100 Then, the volatility was evaluated according to the following criteria, and the results are shown in Table 1. <Evaluation Criteria> 1: Reduction rate from the amount of component A before heating is 15% or more 2: Reduction rate from the amount of component A before heating is 10% or more and less than 15% 3: Reduction rate from the amount of component A before heating is 5% or more and less than 10% 4: Reduction rate from the amount of component A before heating is 2% or more and less than 5% 5: Reduction rate from the amount of component A before heating is less than 2%

[0060]

[0061] As shown in Table 1, the etching solutions of Examples 1 to 7, which contained a primary diamine (component A) and 15% by mass or more of a quaternary ammonium salt (component B), suppressed the formation of micropyramids compared to Comparative Example 1, which did not contain a primary diamine (component A), and Comparative Example 2, which contained 10% by mass of component B. Furthermore, the etching solutions of Examples 1 to 7 suppressed the formation of micropyramids without significantly reducing the etching rate compared to Comparative Examples 1 and 2.

[0062] The etching solution of this disclosure is useful as an etching solution that can suppress the generation of micropyramids.

Claims

1. An etching solution for silicon comprising a primary diamine (component A) and a quaternary ammonium salt (component B), wherein the content of component B is 12% by mass or more.

2. The etching solution according to claim 1, wherein the number of carbon atoms in component A is 3 or more and 6 or less.

3. The etching solution according to claim 1 or 2, wherein component B is a compound represented by the following formula (I). In the above formula (I), R 1 , R 2 , R 3 and R 4 Each of these groups is independently at least one selected from a methyl group, an ethyl group, a propyl group, a hydroxymethyl group, a hydroxyethyl group, and a hydroxypropyl group.

4. The etching solution according to any one of claims 1 to 3, wherein component A is a primary diamine having a hydroxyl group.

5. The etching solution according to any one of claims 1 to 4, wherein component A is a compound represented by (II) below. In formula (II), R 5 R is a hydrogen or hydroxyl group, 6 This is a straight-chain alkylene group having 1 to 4 carbon atoms.

6. The etching solution according to any one of claims 1 to 5, wherein component A is at least one selected from 1,3-diamino-2-propanol, 1,4-diamino-2-butanol, and 1,4-diamino-3-butanol.

7. The etching solution according to any one of claims 1 to 6, wherein the content of component B is 40% by mass or less.

8. The etching solution according to any one of claims 1 to 7, wherein the content of component A is 5% by mass or more and 40% by mass or less.

9. The etching solution according to any one of claims 1 to 8, wherein the total content of component A and component B in the etching solution is 20% by mass or more and 80% by mass or less.

10. The etching solution according to any one of claims 1 to 9, wherein the mass ratio A / B of component A to component B is 0.6 or more and 1.8 or less.

11. The etching solution according to any one of claims 1 to 10, wherein the mass ratio A / B of component A to component B is 0.9 or more and 1.8 or less.

12. The etching solution according to any one of claims 1 to 11, further comprising water.

13. The etching solution according to claim 12, wherein the water content is 20% by mass or more and 75% by mass or less.

14. An etching method comprising the step of etching silicon using an etching solution according to any one of claims 1 to 13.

15. A method for manufacturing a semiconductor substrate, comprising the step of etching a silicon-containing substrate using an etching solution according to any one of claims 1 to 13.

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