Silicon etching solution, etching method, and method for manufacturing semiconductor substrate

Abstract

To provide an etching solution for silicon that suppresses the formation of micro-pyramids, which leads to deterioration of the surface roughness of a silicon substrate.SOLUTION: The present disclosure relates, in one aspect, to an etching solution for silicon, which contains primary alkanolamine (Component A) and quaternary ammonium salt (Component B), in which the content of component A is 50 mass percent or more but not more than 80 mass percent, and in which the content of component B is 20% by mass or more relative to the total content of all components other than component A.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to a silicon etching solution, 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 the purposes of processing, removing foreign matter, etc. For example, etching can be used to create MEMS (Micro Electro Mechanical Systems) devices with complex three-dimensional structures and to thin silicon substrates (silicon wafers).

[0003] Conventional wet etching uses an alkaline aqueous solution. For example, Patent Document 1 proposes a composition useful for etching semiconductor substrates, which contains, in effective etching amounts, 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, about 0 to 5% by mass of a buffering agent, and about 0 to 15% by mass of a corrosion inhibitor, and which gives a sigma-shaped profile. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 2017-108122 Summary of the Invention [Problem to be solved by the invention]

[0005] In recent years, the semiconductor industry has seen increasing integration, which has led to demands for more complex and finer wiring, and therefore for even higher precision in etching technology. In recent years, requirements for the surface quality of silicon substrates have become increasingly stringent, and an etching method that can suppress deterioration of flatness, surface roughness, haze, etc. is desired. It is known that alkaline etching solutions have an etching rate that depends on the crystal orientation of the silicon substrate. For example, when wet etching the 100 crystal orientation of silicon, which is the most commonly used etching surface, with an alkaline etching solution, convex portions (also called micropyramids) are generated, leading to a deterioration in surface roughness. It is thought that the micropyramids are generated due to differences in etching rate depending on the 100, 110, and 111 crystal orientations of silicon.

[0006] Therefore, the present disclosure provides a silicon etching solution, an etching method, and a method for manufacturing a semiconductor substrate that suppress the generation of micropyramids that lead to deterioration of the surface roughness of a silicon substrate. [Means for solving the problem]

[0007] In one aspect, the present disclosure relates to a silicon etching solution comprising a primary alkanolamine (component A) and a quaternary ammonium salt (component B), in which the content of component A is 50% by mass or more and 80% by mass or less, and the content of component B relative to the total content of components other than component A is 20% by mass or more.

[0008] In one aspect, the present disclosure relates to an etching method comprising etching silicon using the etching solution of the present disclosure.

[0009] In one aspect, the present disclosure relates to a method for manufacturing a semiconductor substrate, comprising using the etching solution of the present disclosure.

[0010] In one aspect, the present disclosure relates to a method for manufacturing a semiconductor substrate, including the etching method of the present disclosure.

[0011] In one aspect, the present disclosure relates to a method for etching a silicon substrate, comprising the step of etching a silicon substrate using an etching solution, wherein the etching rate ratio between the 100 surface and the 110 surface of the silicon substrate [(etching rate for the 100 surface) / (etching rate for the 110 surface)] is 0.25 or more and 0.46 or less, and the etching rate ratio between the 100 surface and the 111 surface of the silicon substrate [(etching rate for the 100 surface) / (etching rate for the 111 surface)] is 1.50 or more and 2.35 or less.

[0012] In one aspect, the present disclosure relates to a method for manufacturing a semiconductor substrate, including the disclosed method for etching a silicon substrate.

[0013] In one aspect, the present disclosure relates to an etching solution for etching a silicon substrate, wherein the etching rate ratio of the 100 surface to the 110 surface of the silicon substrate [(etching rate of the 100 surface) / (etching rate of the 110 surface)] is 0.25 or more and 0.46 or less, and the etching rate ratio of the 100 surface to the 111 surface of the silicon substrate [(etching rate of the 100 surface) / (etching rate of the 111 surface)] is 1.50 or more and 2.35 or less. [Effects of the Invention]

[0014] According to one aspect of the present disclosure, it is possible to provide a silicon etching solution that suppresses the generation of micropyramids that lead to deterioration of the surface roughness of a silicon substrate. [Brief explanation of the drawings]

[0015] [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 2, 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. DETAILED DESCRIPTION OF THE INVENTION

[0016] In one aspect, the present disclosure is based on the finding that the generation of micropyramids can be suppressed by using an etching solution containing a primary alkanolamine (component A) and a quaternary ammonium salt (component B), in which the content of component B relative to the total content of components other than component A is equal to or greater than a predetermined value, for etching silicon in the 100 crystal orientation plane.

[0017] In one aspect, the present disclosure relates to a silicon etching solution (hereinafter also referred to as the "etching solution of the present disclosure") that contains a primary alkanolamine (component A) and a quaternary ammonium salt (component B), in which the content of component A is 50% by mass or more and 80% by mass or less, and the content of component B relative to the total content of components other than component A is 20% by mass or more.

[0018] The etching solution of the present disclosure can suppress the generation of micropyramids, which lead to deterioration of the surface roughness of silicon substrates.

[0019] In one or more embodiments, the etching solution of the present disclosure can be used for anisotropic etching such as etching of silicon substrates (wafers), etching for thinning silicon substrates (wafers), etching in micromachining (MEMS) technology, and etching in solar cell manufacturing.

[0020] Although the details of the mechanism by which the effects of the present disclosure are manifested are not clear, it is presumed as follows. When silicon crystal orientation 100 plane (Si(100)) is etched with alkali, pyramid-shaped convex portions called micropyramids are generated. As etching progresses, the micropyramids grow and increase, forming pyramidal irregularities on the surface, worsening the surface roughness. The bottom of this micropyramid is composed of crystal orientation 100 plane (Si(100)), the sides are crystal orientation 110 plane (Si(110)), and the sides are crystal orientation 111 plane (Si(111)). The apex of the pyramid is masked by foreign matter, etc. It is believed that micropyramids occur when using a typical alkaline etching solution due to differences in etching rates for the Si(100), Si(110), and Si(111) crystal planes. However, in this disclosure, it is estimated that the use of a specific amount of primary alkanolamine (component A) and a specific amount of quaternary ammonium (component B) reduces the difference in etching rates for the Si(100), Si(110), and Si(111) crystal planes, thereby suppressing the occurrence of micropyramids. However, the present disclosure need not be construed as being limited to these mechanisms.

[0021] [Component A: Primary alkanolamine] The etching solution of the present disclosure contains a primary alkanolamine (amino alcohol) (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 alkanolamine of the present disclosure is a primary alkanolamine having one nitrogen atom.

[0022] The number of carbon atoms in component A is preferably 2 or more and 10 or less, more preferably 2 or more and 6 or less, and even more preferably 2 or more and 4 or less, from the viewpoint of suppressing the generation of micropyramids.

[0023] Examples of component A include at least one selected from 2-hydroxyethylamine, monopropanolamine (3-amino-1-propanol), monoisopropanolamine (1-amino-2-propanol), and monobutanolamine (4-amino-1-butanol). Among these, from the viewpoint of suppressing the generation of micropyramids, at least one of 2-hydroxyethylamine and monopropanolamine (3-amino-1-propanol) is preferred, and 2-hydroxyethylamine is more preferred.

[0024] From the viewpoint of suppressing the generation of micropyramids, the content of component A in the etching solution of the present disclosure is 50% by mass or more, preferably 54% by mass or more, more preferably 55% by mass or more, and even more preferably 60% by mass or more. From the same viewpoint, it is 80% by mass or less, preferably 75% by mass or less, and more preferably 70% by mass or less. More specifically, the content of component A in the etching solution of the present disclosure is 50% by mass or more and 80% by mass or less, preferably 54% by mass or more and 75% by mass or less, more preferably 55% by mass or more and 70% by mass or less, and even more preferably 60% by mass or more and 70% 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 thereof.

[0025] [Component B: Quaternary ammonium salt] The etching solution of the present disclosure contains a quaternary ammonium salt (hereinafter also referred to as "component B"). In one or more embodiments, component B may be an aliphatic quaternary ammonium salt or a quaternary ammonium salt having a hydroxyalkyl group, from the viewpoint of suppressing the generation of micropyramids. Component B may be one type or a combination of two or more types.

[0026] In one or more embodiments, Component B includes a compound represented by the following formula (I): [ka] In the 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 formula (I), R 1 , R 2 , R 3 and R 4 From the viewpoint of suppressing the generation of micropyramids, each of the groups is preferably at least one selected from a methyl group, an ethyl group, and a propyl group, more preferably a methyl group or an ethyl group, and even more preferably a methyl group.

[0027] The compound represented by the above formula (I) is a salt consisting of a quaternary ammonium cation and a hydroxide, and examples thereof 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.

[0028] From the viewpoint of suppressing the generation of micropyramids, Component B is more preferably at least one selected from tetramethylammonium hydroxide (TMAH), tetraethylammonium hydroxide (TEAH), 2-hydroxyethyltrimethylammonium hydroxide (choline), and dimethylbis(2-hydroxyethyl)ammonium hydroxide, and even more preferably at least one of tetramethylammonium hydroxide (TMAH) and tetraethylammonium hydroxide (TEAH).

[0029] The content of component B relative to the total content of components other than component A in the etching solution of the present disclosure is 20% by mass or more, preferably 22% by mass or more, more preferably 25% by mass or more, from the viewpoint of suppressing the generation of micropyramids, and from the same viewpoint, is preferably 60% by mass or less, more preferably 55% by mass or less, and even more preferably 50% by mass or less. More specifically, the content of component B relative to the total content of components other than component A in the etching solution of the present disclosure is preferably 20% by mass or more and 60% by mass or less, more preferably 22% by mass or more and 55% by mass or less, and even more preferably 25% by mass or more and 50% by mass or less. When component B is an aliphatic quaternary ammonium salt, the content of component B relative to the total content of components other than component A in the etching solution of the present disclosure is, from the same viewpoint, preferably 22 mass% or more and preferably 60 mass% or less, more preferably 55 mass% or less, even more preferably 40 mass% or less, and still more preferably 30 mass% or less. When component B is a quaternary ammonium salt having a hydroxyalkyl group, the content of component B relative to the total content of components other than component A in the etching solution of the present disclosure is, from the same viewpoint, preferably 30% by mass or more, more preferably 40% by mass or more, and preferably 60% 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 thereof.

[0030] From the viewpoint of suppressing the generation of micropyramids, the mass ratio B / A of component A to component B in the etching solution of the present disclosure is preferably 0.1 or more, more preferably 0.15 or more, and preferably 0.5 or less, more preferably 0.4 or less. More specifically, the mass ratio B / A is preferably 0.1 or more and 0.5 or less, more preferably 0.15 or more and 0.4 or less. When component B is an aliphatic quaternary ammonium salt, the mass ratio B / A is, from the same viewpoint, preferably 0.1 or more and 0.25 or less, and more preferably 0.2 or less. When component B is a quaternary ammonium salt having a hydroxyalkyl group, the mass ratio B / A is, from the same viewpoint, preferably 0.1 or more, more preferably 0.2 or more, and preferably 0.5 or less. In the present disclosure, the mass ratio B / A is a value calculated by dividing the mass (content) of component B by the mass (content) of component A.

[0031] The total content of Component A and Component B in the etching solution of the present disclosure is preferably 60% by mass or more, more preferably 65% ​​by mass or more, from the viewpoint of suppressing the generation of micropyramids, and from the same viewpoint, is preferably 95% by mass or less, more preferably 90% by mass or less. More specifically, the total content of Component A and Component B is preferably 60% by mass or more and 95% by mass or less, more preferably 65% ​​by mass or more and 90% by mass or less.

[0032] [water] In one or more embodiments, the etching solution of the present disclosure may further contain water as a medium. Examples of water include distilled water, ion-exchanged water, pure water, and ultrapure water. From the viewpoint of suppressing the generation of micropyramids, the water content in the etching solution of the present disclosure is preferably 10% by mass or more, more preferably 20% by mass or more, and from the same viewpoint, it is preferably 50% by mass or less, more preferably 45% by mass or less, and even more preferably 40% by mass or less. More specifically, the water content in the etching solution of the present disclosure is preferably 10% by mass or more and 50% by mass or less, and even more preferably 20% by mass or more and 40% by mass or less.

[0033] The total content of Component A, Component B, and water in the etching solution of the present disclosure is preferably 90% by mass or more, and more preferably 95% by mass or more, from the viewpoint of suppressing the generation of micropyramids.

[0034] [Component C: Nonionic water-soluble polymer] In one or more embodiments, the etching solution of the present 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 the present disclosure, "water-soluble" refers to a solubility in water (20°C) of 0.5 g / 100 mL or more, preferably 2 g / 100 mL or more. In one or more embodiments, from the viewpoint of adjusting the dissolution rate, Component C is preferably a nonionic water-soluble polymer having an alkyleneoxy group in the molecule. Examples of the alkyleneoxy group include at least one selected from an ethyleneoxy group (EO) and a propyleneoxy group (PO), and from the viewpoint of adjusting the dissolution rate, EO is preferred. Examples of component C include polyethylene glycol (PEG) and polypropylene glycol.

[0035] When the etching solution of the present disclosure contains component C, the content of component C in the etching solution of the present disclosure is preferably 0.0001% by mass or more, more preferably 0.0005% by mass or more, and even more preferably 0.001% by mass or more, from the viewpoint of adjusting the dissolution rate, and from the same viewpoint, is 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. When component C is a combination of two or more types, the content of component C refers to the total content thereof.

[0036] [Component D: Chelating agent] From the viewpoint of removing metal foreign matter, 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 two or more acid groups of at least one type selected from carboxy groups and phosphonic acid groups, and from the viewpoint of removing metallic foreign matter, it is preferable that the compound have four or less such acid groups. Component D is, for example, at least one selected from maleic acid, picolinic acid, and ethylenediaminetetraacetic acid (EDTA), and from the viewpoint of removing metal foreign matter, at least one selected from maleic acid and picolinic acid is preferred.

[0037] 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, and even more preferably 0.1% by mass or more from the viewpoint of removing metal foreign matter, and is preferably 5.0% by mass or less, more preferably 2.5% by mass or less, and even more preferably 1.0% by mass or less from the viewpoint of adjusting the dissolution rate. When component D is a combination of two or more types, the content of component D refers to the total content thereof.

[0038] [Inorganic alkali (ingredient 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 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 the like.

[0039] 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, and even more preferably 0.5% by mass or more, from the viewpoints of adjusting the dissolution rate and suppressing deterioration of surface roughness, and from the same viewpoints, is preferably 50% by mass or less, more preferably 30% by mass or less, and even more preferably 20% by mass or less. When component E is a combination of two or more types, the content of component E refers to the total content thereof.

[0040] [Other ingredients] The etching solution of the present disclosure may further contain or be blended with other components to the extent that the effects of the present 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, and antifoaming agents.

[0041] [Method of manufacturing etching solution] In one or more embodiments, the etching solution of the present disclosure can be obtained by blending component A, component B, water, and, as necessary, the optional components described above (component C, component D, component E, and other components). Therefore, in one aspect, the present disclosure relates to a method for producing an etching solution (hereinafter also referred to as the "etching solution production method of the present disclosure"), which includes a step of blending component A, component B, water, and, as needed, the above-mentioned optional components (component C, component D, component E, and other components) (hereinafter also referred to as the "blending step"). In the present disclosure, "blending" includes simultaneously or sequentially mixing component A, component B, water, and, if necessary, the optional components described above (component C, component D, component E, and other components). The order of mixing is not particularly limited. The blending can be carried out using a mixer such as a homomixer, a homogenizer, an ultrasonic disperser, or a wet ball mill. In the method for producing an etching solution according to the present disclosure, the preferred amount of each component to be blended can be the same as the preferred content of each component in the etching solution according to the present disclosure described above.

[0042] In the present disclosure, in one or more embodiments, the "content of each component in the etching solution" refers to the content of each component in the etching solution used in the etching step, i.e., at the time of starting use in the etching treatment (at the time of use).

[0043] The etching liquid according to the present disclosure may be a so-called one-component type, in which all components are premixed and supplied to the market, or may be a so-called two-component type, in which components are mixed at the time of use.

[0044] In one or more embodiments, the etching solution of the present disclosure is preferably a neutral or alkaline etching solution. For example, the pH of the etching solution of the present 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 the present disclosure, the pH of the etching solution is the value of the etching solution at 25°C during use, and can be measured using a pH meter, specifically, by the method described in the Examples.

[0045] The etching solution of the present disclosure may be stored and supplied in a concentrated state as long as its stability is not impaired. This is preferable because it reduces production and transportation costs. The concentrated solution can then be used in the etching process after being diluted appropriately with water or the like, as needed. The dilution ratio is preferably 1.2 to 100 times.

[0046] In one or more embodiments, the etching solution of the present disclosure can be applied to anisotropic etching such as etching of silicon substrates (wafers), etching in micromachining (MEMS) technology, etching in solar cell manufacturing, and etching for thinning silicon substrates (wafers). In one or more embodiments, etching using the etching solution of the present disclosure can be used in a slicing process, a lapping process, a polishing process, a CMP process, a rinsing process, a heat treatment process, a cleaning process, and a photoresist process.

[0047] When etching a silicon substrate using the etching solution of the present disclosure, in one or more embodiments, the etching rate of the 100th surface of the silicon substrate is preferably 60 nm / min or more, more preferably 70 nm / min or more, and even more preferably 74 nm / min or more, from the viewpoint of productivity. In one or more embodiments, the etching rate of the (110) plane of the silicon substrate is preferably 130 nm / min or more, and more preferably 150 nm / min or more, from the viewpoint of suppressing the generation of micropyramids. In one or more embodiments, the etching rate of the (111) plane of the silicon substrate is preferably 25 nm / min or more, and more preferably 27 nm / min or more, from the viewpoint of suppressing the generation of micropyramids. In one or more embodiments, the etching rate ratio of the 100 surface to the 110 surface of a silicon substrate [(etching rate of the 100 surface) / (etching rate of the 110 surface)] is preferably 0.25 or more, more preferably 0.30 or more, from the viewpoint of suppressing the generation of micropyramids, and is preferably 0.46 or less, more preferably 0.42 or less, and even more preferably 0.40 or less, from the viewpoint of suppressing the generation of micropyramids. In one or more embodiments, the etching rate ratio of the 100 plane to the 111 plane of a silicon substrate [(etching rate of the 100 plane) / (etching rate of the 111 plane)] is preferably 1.50 or more, more preferably 1.70 or more, and even more preferably 1.85 or more, from the viewpoint of suppressing the generation of micropyramids. From the viewpoint of suppressing the generation of micropyramids, it is preferably 2.35 or less, more preferably 2.20 or less, and even more preferably 2.15 or less. More specifically, the etching rate ratio [(etching rate of the 100 plane) / (etching rate of the 111 plane)] is preferably 1.50 or more and 2.35 or less, more preferably 1.70 or more and 2.20 or less, and even more preferably 1.85 or more and 2.15 or less. In one or more embodiments, the etching rate ratio of the 110 surface to the 111 surface of the silicon substrate [(etching rate of the 110 surface) / (etching rate of the 111 surface)] is preferably 5.15 or more and 6.00 or less, more preferably 5.20 or more and 5.90 or less, from the viewpoint of suppressing the generation of micropyramids. In one or more embodiments, it is preferable that the etching rate ratio [(etching rate of 100 surface) / (etching rate of 110 surface)] is 0.25 or more and 0.46 or less, and the etching rate ratio between the 100 surface and the 111 surface of the silicon substrate [(etching rate of 100 surface) / (etching rate of 111 surface)] is 1.50 or more and 2.35 or less. Therefore, in one or more embodiments, the etching liquid of the present disclosure can be an etching liquid for etching a silicon substrate, in which the etching rate ratio of the 100 surface to the 110 surface of the silicon substrate [(etching rate of the 100 surface) / (etching rate of the 110 surface)] is 0.25 or more and 0.46 or less, and the etching rate ratio of the 100 surface to the 111 surface of the silicon substrate [(etching rate of the 100 surface) / (etching rate of the 111 surface)] is 1.50 or more and 2.35 or less. In one or more embodiments of the present disclosure, the etching rate of each crystal plane can be adjusted by the content of the components of the etching solution, and can be measured by the method described in the examples.

[0048] [kit] In one aspect, the present disclosure relates to a kit for producing the etching solution of the present disclosure (hereinafter also referred to as the "kit of the present disclosure"). In one or more embodiments, the kit of the present disclosure includes a kit (two-component etching solution) that contains a solution containing component A (first liquid) and a solution containing component B (second liquid) in a mutually unmixed state, which are mixed at the time of use. After the first liquid and the second liquid are mixed, they may be diluted with water as needed. The first liquid or the second liquid may contain all or a part of the water used to prepare the etching solution. The first liquid and the second liquid may contain the above-mentioned optional components (component C, component D, component E, other components) as needed. The kit disclosed herein can produce a silicon etching solution that can suppress the generation of convex portions and micropyramids due to differences in etching rate depending on the crystal orientation of the substrate, which leads to deterioration of the surface roughness of the silicon substrate.

[0049] [Material to be processed] In one or more embodiments, the workpiece to be etched using the etching solution of the present disclosure may be silicon such as single crystal silicon, polycrystalline silicon, polysilicon, or 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 100 crystal orientation is even more preferred, and single crystal silicon with a 100 crystal orientation is even more preferred. Examples of the object to be processed include a silicon substrate (silicon wafer), a silicon substrate having a silicon oxide film and a silicon nitride film, and a structure in which silicon is patterned.

[0050] [Etching method] In one aspect, the present disclosure relates to an etching method (hereinafter also referred to as the "etching method of the present disclosure") that includes a step (hereinafter also referred to as the "etching step") of etching silicon using the etching solution of the present disclosure or a mixture of an existing chemical and the etching solution of the present disclosure. Use of the etching method of the present disclosure can suppress the generation of micropyramids, thereby improving the productivity of semiconductor substrates with improved quality. Existing chemicals include, for example, ammonia, potassium hydroxide, and SC-1 (aqueous solution containing ammonia and hydrogen peroxide). In one or more embodiments, the mixed solution can be prepared by blending an existing chemical agent with the etching solution of the present disclosure. For example, in one or more embodiments, the mixed solution can be obtained by adding ammonia, hydrogen peroxide, and the etching solution of the present disclosure to ultrapure water. In one or more embodiments, the mixed solution can be obtained by mixing SC-1, which is prepared by mixing ultrapure water, ammonia, and hydrogen peroxide, with the etching solution of the present disclosure. The etching solution of the present disclosure used to prepare the mixed solution is preferably formulated so that the concentration of component A in the mixed solution is 50% by mass or more and 80% by mass or less.

[0051] 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 step includes etching at least a portion of the silicon substrate to reduce the thickness of the silicon substrate.

[0052] In one or more embodiments, the etching step includes contacting the above-described object to be treated with the etching solution of the present disclosure. In the etching step, examples of the etching method or the method of contacting the etching solution of the present disclosure with the object to be treated include immersion etching and single wafer etching.

[0053] In the etching step, the temperature of the etching solution during use (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 is preferably 100° C. or lower, more preferably 90° C. or lower, and even more preferably 85° C. or lower, from the viewpoint of etching solution life. More specifically, the temperature of the etching solution during use 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 step, the etching time (etching treatment time) can be appropriately set depending on the structure and material of the silicon substrate and the etching treatment conditions.

[0054] In one or more embodiments, the etching rate of the 100th face of the silicon substrate in the etching step is preferably 60 nm / min or more, more preferably 70 nm / min or more, and even more preferably 74 nm / min or more, from the viewpoint of productivity. In one or more embodiments, the etching rate of the (110) plane of the silicon substrate in the etching step is preferably 130 nm / min or more, more preferably 150 nm / min or more, from the viewpoint of suppressing the generation of micropyramids. In one or more embodiments, the etching rate of the (111) plane of the silicon substrate in the etching step is preferably 25 nm / min or more, more preferably 27 nm / min or more, from the viewpoint of suppressing the generation of micropyramids. In one or more embodiments, in the etching step, the etching rate ratio of the 100 surface to the 110 surface of the silicon substrate [(etching rate of the 100 surface) / (etching rate of the 110 surface)] is preferably 0.25 or more, more preferably 0.30 or more, from the viewpoint of suppressing the generation of micropyramids, and is preferably 0.46 or less, more preferably 0.42 or less, and even more preferably 0.40 or less, from the viewpoint of suppressing the generation of micropyramids. In one or more embodiments, the etching rate ratio of the 100 plane to the 111 plane of the silicon substrate [(etching rate of the 100 plane) / (etching rate of the 111 plane)] is preferably 1.50 or more, more preferably 1.70 or more, and even more preferably 1.85 or more, from the viewpoint of suppressing the generation of micropyramids. From the viewpoint of suppressing the generation of micropyramids, the etching rate ratio is preferably 2.35 or less, more preferably 2.20 or less, and even more preferably 2.15 or less. More specifically, the etching rate ratio [(etching rate of the 100 plane) / (etching rate of the 111 plane)] is preferably 1.50 or more and 2.35 or less, more preferably 1.70 or more and 2.20 or less, and even more preferably 1.85 or more and 2.15 or less. In one or more embodiments, in the etching step, the etching rate ratio of the 110 surface to the 111 surface of the silicon substrate [(etching rate of the 110 surface) / (etching rate of the 111 surface)] is preferably 5.15 or more and 6.00 or less, more preferably 5.20 or more and 5.90 or less, from the viewpoint of suppressing the generation of micropyramids. In one or more embodiments, it is preferable that the etching rate ratio in the etching step [(etching rate of 100 surface) / (etching rate of 110 surface)] is 0.25 or more and 0.46 or less, and the etching rate ratio between the 100 surface and the 111 surface of the silicon substrate [(etching rate of 100 surface) / (etching rate of 111 surface)] is 1.50 or more and 2.35 or less. Therefore, in one or more embodiments, the etching method of the present disclosure is a method for etching a silicon substrate, comprising the step of etching a silicon substrate using an etching solution, wherein the etching rate ratio between the 100 surface and the 110 surface of the silicon substrate [(etching rate for the 100 surface) / (etching rate for the 110 surface)] is 0.25 or more and 0.46 or less, and the etching rate ratio between the 100 surface and the 111 surface of the silicon substrate [(etching rate for the 100 surface) / (etching rate for the 111 surface)] is 1.50 or more and 2.35 or less.

[0055] In one or more embodiments, the etching method of the present disclosure may include a cleaning step, a rinsing step, a drying step, etc. in addition to the etching step. 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 the present disclosure may include, after the etching step, a rinsing step in which the silicon after the etching process is rinsed with water or the like, and a drying step in which the silicon after the rinsing is dried.

[0056] [Method of manufacturing semiconductor substrate] The etching solution and etching method of the present disclosure described above can be suitably used in the manufacture of semiconductor substrates. Therefore, in one aspect, the present disclosure relates to a method for manufacturing a semiconductor substrate, which includes using the etching solution of the present disclosure. In one or more embodiments, using the etching solution of the present disclosure means etching a workpiece using the etching solution of the present disclosure. The etching method and conditions include the same etching method and conditions (etching temperature, etching time) as those in the etching step of the etching method of the present disclosure described above. The workpiece can be any of the above-mentioned workpieces. In another aspect, the present disclosure relates to a method for manufacturing a semiconductor substrate, including the etching method of the present disclosure. [Example]

[0057] The present disclosure will be specifically described below using examples, but the present disclosure is not limited to these examples in any way.

[0058] <Test 1> 1-1. Preparation of Etching Solution (Examples 1 to 8 and Comparative Examples 1 and 2) The etching solutions of Examples 1 to 8 and Comparative Examples 1 and 2 were prepared by mixing the components and water (ultrapure water) shown in Table 1. The pH of the prepared etching solutions was 14. The content of each component in Table 1 is the content (mass %, active content) of each component when the etching solution is used. The water content is the remainder after subtracting components A and B from the total amount of the etching solution (100 mass %). The water content also includes the content of water contained in the aqueous solution of component B.

[0059] The following components were used to prepare the etching solution. (Component A) 2-Hydroxyethylamine [Tokyo Chemical Industry Co., Ltd.] (Component B) TMAH·5H2O [Tetramethylammonium hydroxide pentahydrate, Fujifilm Wako Pure Chemical Industries, Ltd.] TEAH [tetraethylammonium hydroxide, 35% by weight aqueous solution, manufactured by Seichem Japan LLC] Choline [2-hydroxyethyltrimethylammonium hydroxide, 50% by mass aqueous solution, manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.] Dimethylbis(2-hydroxyethyl)ammonium hydroxide [50% by mass aqueous solution, manufactured by Shikoku Chemical Industries, Ltd.]

[0060] [pH of etching solution] The pH value of the etching solution at 25° C. was measured using a pH meter (manufactured by DKK-Toa Corporation), and was the value measured one minute after the electrode of the pH meter was immersed in the etching solution.

[0061] 1-2.Evaluation of etching solutions Etching was carried out using each etching solution under the conditions below, and the presence or absence of micropyramids was observed and evaluated as follows.

[0062] [Etching method] A silicon substrate with the 100 crystal orientation shown below was cut into 4 x 2 cm pieces using a diamond cutter to prepare test pieces. The test pieces were then immersed in acetone for 1 minute so that the entire surface was immersed, then rinsed with ultrapure water, then immersed in ammonium hydrofluoride diluted to 1% with ultrapure water for 1 minute so that the entire surface was immersed, then rinsed 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 test piece was immersed so that the entire surface was immersed, and then left to stand in a thermostatic chamber (ESPEC, model: PU-4J) set to 60°C for 1 hour to perform etching. Next, the test piece was removed from the thermostatic chamber, and the entire surface was rinsed with ultrapure water and dried with an air blower. [Silicon substrate] The silicon substrates used were as follows: Type: (100) Single-sided mirror wafer (single crystal silicon with 100 crystal orientation) Resistance: ≦1Ω·cm Thickness: 1000±25μm Orientation flat: Notch specification Particles: Any

[0063] [Micropyramid observation conditions] The appearance of the silicon substrate with a crystal orientation of 100 after the above etching was observed as follows. The surface that was not the mirror surface after etching was observed at 100x magnification by differential interference contrast using a Keyence VHX-7100 microscope. FIG. 1 shows examples of photographs of the appearance of the surface of a silicon substrate etched using the etching solutions of Example 2 and Comparative Example 1. As shown in FIG. 1A, no micropyramids were observed on the surface of the silicon substrate etched using the etching solution of Example 2. On the other hand, as shown in FIG. 1B, multiple micropyramids (areas that look like black spots in FIG. 1B) were observed on the surface of the silicon substrate etched using the etching solution of Comparative Example 1. [Method for evaluating micropyramids] Ten visual fields were checked, and if at least one micropyramid was found in the field, it was counted. 0 to 1 visual field was rated A, 2 visual fields was rated B, 3 to 5 visual fields was rated C, and 6 or more visual fields was rated D. The results are shown in Table 1.

[0064] [Table 1]

[0065] As shown in Table 1, the etching solutions of Examples 1 to 8, which contain predetermined amounts of primary alkanolamine (component A) and quaternary ammonium (component B), suppressed the generation of micropyramids compared to Comparative Example 1, in which the content of component A was 40 mass%, and Comparative Example 2, in which the content of component B relative to the total content of components other than component A was 17.5 mass%. Furthermore, the etching solutions of Examples 1 to 7, in which component A was 60 mass% or more, suppressed the generation of micropyramids more than the etching solution of Example 8, in which component A was 50 mass%.

[0066] <Test 2> 2-1. Preparation of Etching Solution (Examples 11 to 17 and Comparative Examples 11 to 12) The etching solutions of Examples 11 to 17 and Comparative Examples 11 and 12 were prepared by mixing the components and water (ultrapure water) shown in Table 2. The pH of the prepared etching solutions was 14. The components used to prepare the etching solutions of Examples 11 to 17 and Comparative Examples 11 to 12 were the same as those used to prepare the etching solutions of Examples 1 to 5, 7 to 8 and Comparative Examples 1 to 2, respectively.

[0067] 2-2.Evaluation of etching solutions Etching was carried out using each etching solution under the conditions below, and the etching rate for each crystal plane (100 plane, 110 plane, 111 plane) and the occurrence of micropyramids on the 100 plane were observed and evaluated.

[0068] [Etching method] The same procedure as in Test 1 was carried out except that silicon substrates with the following crystal planes (100 plane, 110 plane, 111 plane) were used. [Silicon substrate] The silicon substrates used were as follows: <Silicon substrate with 100 crystal orientation> Type: (100) Single-sided mirror wafer (single crystal silicon with 100 crystal orientation) Resistance: ≦1Ω·cm Thickness: 1000±25μm Orientation flat: Notch specification Particles: Any <Silicon substrate with 110 crystal orientation> Type: (110) Single-sided mirror wafer (single crystal silicon with 110 crystal orientation) Resistance: ≦1Ω·cm Thickness: 1000±25μm Orientation flat: Notch specification Particles: Any <Silicon substrate with 111 crystal orientation> Type: (111) single-sided mirror wafer (single crystal silicon with 111 crystal orientation) Resistance: ≦1Ω·cm Thickness: 1000±25μm Orientation flat: Notch specification Particles: Any

[0069] [Etching rate and etching rate ratio] The etched film thickness was calculated from the weight change before and after etching of the substrate for each crystal plane (100 plane, 110 plane, 111 plane), and the etching rate and etching rate ratio were determined. The results are shown in Table 2. Etching rate (nm / min) = (weight of substrate before etching (g) - weight of substrate after etching (g)) / density (g / cm 3 ) / area of ​​the front and back surfaces of the board (cm 2 ) / etching time (min) x 10 7 Density of silicon substrate with 100 crystal orientation: 2.33 g / cm 3 Density of silicon substrate with 110 crystal orientation: 2.33 g / cm 3 Density of silicon substrate with 111 crystal orientation: 2.33 g / cm 3

[0070] [Micropyramid observation conditions and evaluation method] The micropyramids were observed and evaluated in the same manner as in Test 1. The results are shown in Table 2.

[0071] [Table 2]

[0072] As shown in Table 2, the etching solutions of Examples 11 to 17, in which the etching rate ratio [(100) / (110)] was 0.25 or more and 0.46 or less, and the etching rate ratio [(100) / (111)] was 1.50 or more and 2.35 or less, suppressed the generation of micropyramids compared to Comparative Example 11, in which the etching rate ratio [(100) / (110)] was 0.24 and the etching rate ratio [(100) / (111)] was 1.48, and Comparative Example 12, in which the etching rate ratio [(100) / (110)] was 0.48. Examples 12, 13, 15, and 16, in which the etching rate ratio [(100) / (110)] was 0.40 or less, suppressed the generation of micropyramids more than Examples 11, 14, and 17, in which the etching rate ratio [(100) / (110)] was more than 0.40. [Industrial Applicability]

[0073] The etching solution of the present disclosure is useful as an etching solution that can suppress the generation of micropyramids.

Claims

1. Contains a primary alkanolamine (component A) and a quaternary ammonium salt (component B), The content of component A is 50% by mass or more and 80% by mass or less, A silicon etching solution, in which the content of component B is 20 mass% or more relative to the total content of components other than component A.

2. The etching solution according to claim 1, wherein component A has 2 or more and 6 or less carbon atoms.

3. 2. The etching solution according to claim 1, wherein component B is a compound represented by the following formula (I): 【Chemical 1】 In the 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.

4. The etching solution of claim 1 further comprising water.

5. The etching solution according to claim 4, wherein the total content of component A, component B, and water in the etching solution is 90 mass% or more.

6. 2. The etching solution according to claim 1, wherein the silicon is single crystal silicon having a (100) crystal orientation.

7. 2. The etching solution according to claim 1, wherein the temperature of the etching solution during use is 40° C. or higher.

8. An etching method comprising the step of etching silicon using the etching solution according to any one of claims 1 to 7.

9. A method for manufacturing a semiconductor substrate, comprising using the etching solution according to any one of claims 1 to 7.

10. A method for manufacturing a semiconductor substrate, comprising the etching method according to claim 8.

11. Etching a silicon substrate using an etching solution, the etching rate ratio of the 100 surface to the 110 surface of the silicon substrate [(etching rate of the 100 surface) / (etching rate of the 110 surface)] is 0.25 or more and 0.46 or less; A method for etching a silicon substrate, wherein the etching rate ratio between the 100 surface and the 111 surface of the silicon substrate [(etching rate of the 100 surface) / (etching rate of the 111 surface)] is 1.50 or more and 2.35 or less.

12. 12. The method for etching a silicon substrate according to claim 11, wherein the etching rate ratio of the (110) plane to the (111) plane of the silicon substrate [(etching rate of the (110) plane) / (etching rate of the (111) plane)] is 5.15 or more and 6.00 or less.

13. The method for etching a silicon substrate according to claim 11 , wherein the etching solution comprises a primary alkanolamine.

14. The method for etching a silicon substrate according to claim 11 , wherein the etching solution contains a quaternary ammonium salt.

15. A method for manufacturing a semiconductor substrate, comprising the method for etching a silicon substrate according to any one of claims 11 to 14.

16. An etching solution for etching a silicon substrate, An etching solution for silicon substrates, in which the etching rate ratio between the 100 surface and the 110 surface of a silicon substrate [(etching rate of the 100 surface) / (etching rate of the 110 surface)] is 0.25 or more and 0.46 or less, and the etching rate ratio between the 100 surface and the 111 surface of a silicon substrate [(etching rate of the 100 surface) / (etching rate of the 111 surface)] is 1.50 or more and 2.35 or less.

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