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

Abstract

In one embodiment, an etching solution for silicon is provided that suppresses the generation of micropyramids, which lead to deterioration of the surface roughness of the silicon substrate. [Solution] In one embodiment, this 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% by mass or more.

Description

[Technical Field]

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

[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, 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. Patent Document 2 proposes a silicon etching solution containing a 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. [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] Patent No. 6577446 [Patent Document 2] Japanese Patent Publication No. 2023-152834 [Overview of the project] [Problems that the invention aims to solve]

[0005] In recent years, the semiconductor field has seen increasing integration, leading to a demand 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, haze, etc., 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 100-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 a deterioration of surface roughness. It is thought that micropyramids are generated due to differences in etching rates depending on the 100-plane, 110-plane, and 111-plane of silicon crystal orientation.

[0006] 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. [Means for solving the problem]

[0007] 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.

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

[0009] 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. [Effects of the Invention]

[0010] According to the present disclosure, in one aspect, an etching solution for silicon can be provided that suppresses the generation of micro-pyramids leading to deterioration of the surface roughness of a silicon substrate.

Brief Description of the Drawings

[0011] [Figure 1] FIG. 1A is a photograph showing an example of the appearance of a silicon substrate after etching using the etching solution of Example 1, and FIG. 1B is a photograph showing an example of the appearance of a silicon substrate after etching using the etching solution of Comparative Example 1.

Modes for Carrying Out the Invention

[0012] In one aspect, the present disclosure is based on the finding that by using an etching solution containing a primary diamine (component A) and a quaternary ammonium salt (component B), with the content of component B being a predetermined value or more, for etching the 100 plane of the crystal orientation of silicon, the generation of micro-pyramids can be suppressed without sacrificing the etching rate, for example, more effectively than in the case of combining monoethanolamine and a quaternary ammonium salt.

[0013] In one aspect, the present disclosure relates to an etching solution for silicon (hereinafter, also referred to as "the etching solution of the present disclosure") that contains a primary diamine (component A) and a quaternary ammonium salt (component B), and the content of component B is 12% by mass or more.

[0014] According to the etching solution of the present disclosure, the generation of micro-pyramids leading to deterioration of the surface roughness of a silicon substrate can be suppressed.

[0015] In one or more embodiments, the etching solution of the present disclosure can be used for anisotropic etching such as etching of a silicon substrate (wafer), etching in thinning of a silicon substrate (wafer), etching in micro-machining (MEMS) technology, and etching in solar cell manufacturing.

[0016] Although the details of the mechanism of the effect manifestation of the present disclosure are not clear, it is presumed as follows. When the 100 plane of the crystal orientation of silicon (Si(100)) is etched with an alkali, convex portions in the shape of pyramids called micropyramids are generated. As the etching progresses, the micropyramids grow and increase, and the surface roughness deteriorates due to the formation of pyramid-shaped irregularities on the surface. This micropyramid is composed of a bottom surface with a crystal orientation of 100 plane (Si(100)), sides with a crystal orientation of 110 plane (Si(110)), and side surfaces with a crystal orientation of 111 plane (Si(111)), and the apex of the pyramid is masked by foreign matter or the like. Since general alkaline etching solutions have differences in the etching rates of the crystal planes of Si(100), Si(110), and Si(111), it is considered that micropyramids are generated. However, in the present disclosure, it is presumed that by using a primary diamine (component A) and a specific amount of a quaternary ammonium salt (component B), the difference in the etching rates of the crystal planes of Si(100), Si(110), and Si(111) becomes small, and the generation of micropyramids can be suppressed. However, the present disclosure may not be construed as being limited to these mechanisms.

[0017] [Component A: Primary diamine] The etching solution of the present disclosure contains a primary diamine (hereinafter also referred to as "component A"). Component A may be one kind or a combination of two or more kinds. The primary diamine in the present disclosure is a primary diamine having 2 nitrogen atoms in one or more embodiments.

[0018] From the viewpoint of suppressing the generation of micropyramids, the carbon number of component A is preferably 3 or more and 6 or less, more preferably 3 or more and 5 or less, and still more preferably 3 or more and 4 or less.

[0019] From the viewpoint of suppressing the generation of micropyramids, the compounds represented by the following (II) are preferably mentioned as component A. <​​​​​5 R is a hydrogen or hydroxyl group, 6 This is a linear alkylene group having 1 to 4 carbon atoms. R 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.

[0020] In one or more embodiments, as component A, from the viewpoint of suppressing the formation of micropyramids, the compound represented in (II) above is preferred, and 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. In one or more embodiments, component A is a primary diamine having a hydroxyl group, from the viewpoint of low volatility and ease of handling. 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.

[0021] From the viewpoint of suppressing the generation of micropyramids, the content of component A in the etching solution of this disclosure is preferably 5% by mass or more, more preferably 10% by mass or more, and even more preferably 15% by mass or more. From the viewpoint of productivity, 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 A in the etching solution of this 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 even more preferably 15% by mass or more and 30% by mass or less. When component A is a combination of two or more types, the content of component A refers to the total content of those types.

[0022] [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, an aliphatic quaternary ammonium salt and a quaternary ammonium salt having a hydroxyalkyl group can be mentioned. Component B may be one kind or a combination of two or more kinds.

[0023] As Component B, in one or more embodiments, a compound represented by the following formula (I) can be mentioned.

Chemical formula

[0024] 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.

[0025] 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.

[0026] 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.

[0027] 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.

[0028] 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.

[0029] [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.

[0030] 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, from the viewpoint of suppressing the generation of micropyramids.

[0031] 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, it is preferably 2 or less, more preferably 1 or less, and even more preferably 0.8 or less, from the viewpoint of suppressing the generation of micropyramids. 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 lower, more preferably 0.1 or higher and 1 or lower, and even more preferably 0.2 or higher and 0.8 or lower. 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, it is preferably 2 or less, more preferably 1 or less, and even more preferably 0.5 or less, from the viewpoint of suppressing the generation of micropyramids. More specifically, in one or more embodiments, the mass ratio of component B to water [content of component B / content of water] is preferably 0.01 or higher and 2 or lower, more preferably 0.1 or higher and 1 or lower, and even more preferably 0.2 or higher and 0.5 or lower.

[0032] [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 the alkylene oxy group 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.

[0033] [Ingredient D: Chelating agent] The etching solution of this disclosure may further contain a chelating agent (hereinafter also referred to as "component D") from the viewpoint of removing metallic foreign matter. 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 two or more acidic groups selected from carboxyl groups and phosphonic acid groups, and from the viewpoint of removing metallic foreign matter, it is preferable that the compound has four or fewer of the acidic groups. Component D can be, for example, at least one selected from maleic acid, picolinic acid, and ethylenediaminetetraacetic acid (EDTA), and from the viewpoint of removing metallic foreign matter, at least one selected from maleic acid and picolinic acid is preferred. If the etching solution of this disclosure contains component D, the content of component D in the etching solution of this disclosure is preferably 0.01% by mass or more, more preferably 0.05% by mass or more, and still preferably 0.1% by mass or more, from the viewpoint of removing metallic foreign matter, and preferably 5.0% by mass or less, more preferably 2.5% by mass or less, and still preferably 1.0% by mass or less, from the viewpoint of adjusting the dissolution rate. If component D is a combination of two or more types, the content of component D refers to the total content of those types.

[0034] [Inorganic alkali (component E)] In one or more embodiments, the etching solution of this disclosure may further contain an inorganic alkali (hereinafter also referred to as "component E") from the viewpoint 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; and others. If the etching solution of this disclosure contains component E, the content of component E in the etching solution of this disclosure is preferably 0.01% by mass or more, more preferably 0.1% by mass or more, even more preferably 0.5% by mass or more, and from the viewpoint of adjusting the dissolution rate and suppressing deterioration of surface roughness, preferably 50% by mass or less, more preferably 30% by mass or less, and even more preferably 20% by mass or less. If component E is a combination of two or more types, the content of component E refers to the total content of those types.

[0035] [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 alkaline 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, disinfectants, antibacterial agents, antioxidants, defoamers, and the like.

[0036] In one or more embodiments, the etching solution of this disclosure may 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 this disclosure is preferably less than 1% by mass, more preferably 0.1% by mass or less, and even more preferably 0% by mass.

[0037] [Method for manufacturing etching solution] The etching solution of this disclosure can be obtained in one or more embodiments by blending component A, component B, water, and optionally the above-mentioned optional components (component C, component D, component E, and other components). Accordingly, this disclosure relates in one embodiment to a method for producing an etching solution (hereinafter also referred to as "the etching solution manufacturing method of this disclosure") which includes a step of blending component A, component B, water, and optionally the above-mentioned optional components (component C, component D, component E, and other components) (hereinafter also referred to as the "blending step"). In this disclosure, "compounding" includes mixing component A, component B, water, and optionally the aforementioned optional components (component C, component D, component E, and other components) simultaneously or sequentially. The order of mixing is not particularly limited. The compounding can be carried out using, for example, a homomixer, homogenizer, ultrasonic disperser, and wet ball mill. In the etching solution manufacturing method of this disclosure, the preferred blending amounts of each component can be the same as the preferred content of each component in the etching solution of this disclosure described above.

[0038] 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, i.e., at the start of use for the etching process. The content of each component in the etching solution composition of this disclosure can be considered as the blending amount of each component in the etching solution composition of this disclosure in one or more embodiments. However, the blending amount and content may differ when neutralization is involved.

[0039] 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.

[0040] 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.

[0041] 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 because 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.

[0042] 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 step, lapping step, polishing step, CMP step, rinsing step, heat treatment step, cleaning step, and photoresist step.

[0043] [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 a solution containing component A (first solution) and a solution containing component B (second solution), which are not mixed with each other and are mixed at the time of use (a two-component etching solution). 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 disclosed herein, it is possible to manufacture an etching solution for silicon that can suppress the generation of protrusions and micropyramids caused by differences in etching rates dependent on the crystal orientation of the silicon substrate, which can lead to deterioration of the surface roughness of the silicon substrate.

[0044] [Object to be processed] In one or more embodiments, the workpiece to be etched using the etching solution of this disclosure includes 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 materials to be processed include silicon substrates (silicon wafers), silicon substrates having silicon oxide films and silicon nitride films, and silicon-containing substrates such as structures with silicon patterns formed on them.

[0045] [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 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 chemicals include ammonia, potassium hydroxide, and SC-1 (an aqueous solution containing ammonia and hydrogen peroxide). The mixture can be prepared in one or more embodiments by combining an existing agent with the etching solution of the Disclosure. For example, the mixture can be obtained in one or more embodiments by adding ammonia, hydrogen peroxide, and the etching solution of the Disclosure to ultrapure water. The mixture can also be obtained in one or more embodiments by mixing SC-1, which is prepared by mixing ultrapure water, ammonia, and hydrogen peroxide, with the etching solution of the 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.

[0046] The etching process is, in one or more embodiments, 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 step includes etching at least a portion of the silicon substrate to reduce the thickness of the silicon substrate.

[0047] 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 this disclosure in the etching process include immersion etching and single-wafer etching.

[0048] 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 or higher and 100°C or lower, more preferably 40°C or higher and 90°C or lower, and even more preferably 50°C or higher and 85°C or lower. In the etching process described above, the etching time (etching treatment time) can be set appropriately according to the structure, material, and etching treatment conditions of the silicon substrate.

[0049] 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 etched silicon is rinsed with water or the like, and a drying step in which the rinsed silicon is dried.

[0050] [Manufacturing method for semiconductor substrates] The etching solution and etching method described above can be suitably used in the manufacture of semiconductor substrates. 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 a step of etching a silicon-containing substrate (workpiece) using the etching solution of this disclosure (hereinafter also referred to as "etching step"). The etching method and conditions in the etching step of the semiconductor substrate manufacturing method of this disclosure include the same etching treatment method and treatment conditions (etching temperature, etching time) as described above for the etching step of the etching method of this disclosure. The workpiece is the workpiece described above. [Examples]

[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 solution (Examples 1-7 and Comparative Examples 1-2) Etching solutions for Examples 1-7 and Comparative Examples 1-2 were prepared by mixing each component 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 represents the content (mass %) of each component 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-ingredient 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 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.

[0055] 2. Evaluation of etching solution For each etching solution, etching was performed 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 sections using a diamond cutter to prepare test specimens. The specimens were then immersed in acetone for 1 minute, ensuring the entire surface was submerged, followed by rinsing with ultrapure water. Next, the specimens were immersed in ammonium hydrofluoride diluted to 1% with ultrapure water for 1 minute, again ensuring the entire surface was submerged, followed by rinsing with ultrapure water, and finally drying 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 compressed air. [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 ± 25 μm Original Flat: Notch design Particles: Not specified

[0057] [Etching speed] The etched film thickness was calculated from the weight change of the substrate before and after etching of the crystal planes (100 planes), and the etching rate was determined. 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 a crystal orientation of 100 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 interferometry. Here, Figure 1 shows an example of a photograph of the surface appearance of a 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. [Method for evaluating micropyramids] Ten fields of view were examined, and if at least one micropyramid was present in a field of view, it was counted. A was assigned for 0-1 fields of view, B for 2 fields, C for 3-5 fields, and D for 6 or more fields. The results are shown in Table 1.

[0059] [Volatile] The amount of component A in each etching solution was analyzed using NMR after heating at the etching temperature (60°C) shown in Table 1 for 120 minutes, and the reduction rate of component A due to heating was calculated. The reduction rate is an indicator of how much component A 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 of 15% or more from the amount of component A before heating. 2: The reduction rate from the amount of component A before heating is 10% or more but less than 15%. 3: The reduction rate from the amount of component A before heating is 5% or more but less than 10%. 4: The reduction rate from the amount of component A before heating is 2% or more but less than 5%. 5: Reduction rate from the amount of component A before heating is less than 2%

[0060] [Table 1]

[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. [Industrial applicability]

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

Claims

1. It contains a primary diamine (component A) and a quaternary ammonium salt (component B), An etching solution for silicon, having a content of component B of 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). 【Chemistry 1】 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 claim 1 or 2, wherein component A is a primary diamine having a hydroxyl group.

5. The etching solution according to claim 1 or 2, wherein component A is a compound represented by (II) below. 【Chemistry 2】 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 claim 1 or 2, 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 claim 1 or 2, wherein the content of component B is 40% by mass or less.

8. The etching solution according to claim 1 or 2, wherein the content of component A is 5% by mass or more and 40% by mass or less.

9. The etching solution according to claim 1 or 2, 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 claim 1 or 2, 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 claim 1 or 2, 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 claim 1 or 2, further comprising water.

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

14. An etching method comprising the step of etching silicon using the etching solution described in claim 1 or 2.

15. A method for manufacturing a semiconductor substrate, comprising the step of etching a silicon-containing substrate using the etching solution described in claim 1 or 2.

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