Silicon etching solution

Abstract

To provide a silicon etching solution that can simultaneously improve the solubility of a silicon (100) surface during etching and suppress deterioration of the surface roughness of the silicon (100) surface after etching.SOLUTION: In an embodiment, the present disclosure relates to a silicon etching solution including a primary alkanolamine (component A), the content of component A is 50 weight% or more, and no quaternary ammonium (component B) or less than 1 weight% of quaternary ammonium (component B).SELECTED DRAWING: None

Description

Technical Field

[0001] The present disclosure relates to an etching solution for silicon.

Background Art

[0002] In the manufacturing process of semiconductor devices using silicon, wet etching and dry etching for the purposes of processing, foreign matter removal, etc. are used. For example, it is possible to fabricate MEMS (Micro Electro Mechanical Systems) devices with complex three-dimensional structures using etching, or to thin silicon wafers.

[0003] In conventional wet etching, an alkaline aqueous solution containing potassium hydroxide, tetramethylammonium hydroxide (TMAH), etc. is used. For example, Patent Document 1 proposes a method for manufacturing a light-emitting element, which includes a step of forming a scribe groove by irradiating a back surface of a substrate made of a group III nitride semiconductor having a plurality of light-emitting element structures formed on a surface with a laser along a planned element division line, and a step of removing a modified layer formed in the scribe groove by alternately repeating wet etching using a hydrofluoric acid-based solution and wet etching using an alkaline solution, and a step of dividing the substrate along the scribe groove to divide it into each light-emitting element. Patent Document 2 proposes a composition containing 2-(2-aminoethylamino)-ethanol and water and substantially free of a polar organic solvent, which can remove residues of organic, organometallic, and metal oxides from a substrate containing a part and / or layer of a metal and / or a metal alloy. Patent Document 3 proposes a composition for etching a silicon-containing substrate, which contains, in terms of the 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 (MEA), 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, and provides a sigma-shaped profile. Patent Document 4 proposes an anisotropic etching agent composition for silicon microfabrication, which contains (1) an organic alkali compound and (2) at least one reducing compound selected from hydroxylamines, hypophosphites, reducing sugars, ascorbic acid, glyoxylic acid, and pyrocatechin, and derivatives thereof.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Patent Document 2

Patent Document 3

Patent Document 4

Summary of the Invention

Problems to be Solved by the Invention

[0005] In recent years, in the semiconductor field, high integration has been progressing, the wiring has become more complex and finer, and higher precision in etching technology is required. In recent years, the requirements for the surface quality of silicon substrates have become increasingly strict, and an etching method that can suppress deterioration in flatness, surface roughness, haze, etc. is desired. Alkaline etching solutions are known to have an etching rate that depends on the crystal plane orientation of a silicon substrate. For example, when wet etching a silicon (100) plane, which is mainly used as an etching surface, with an alkaline etching solution, convex portions (also called micropyramids) are generated due to the difference in etching rate depending on the crystal plane orientation of the silicon substrate, leading to a problem of deterioration of the surface roughness.

[0006] Therefore, the present disclosure provides an etching solution for silicon that can achieve both an improvement in the solubility of the silicon (100) plane in etching and a suppression of the deterioration of the surface roughness of the silicon (100) plane after etching.

Means for Solving the Problems

[0007] In one aspect, the present disclosure relates to an etching solution for silicon that contains a primary alkanolamine (Component A), the content of Component A is 50% by mass or more, and does not contain a quaternary ammonium (Component B), or contains a quaternary ammonium (Component B) of less than 1% by mass.

Effects of the Invention

[0008] According to the present disclosure, in one aspect, an etching solution can be provided that can achieve both an improvement in the solubility of the silicon (100) plane in etching and a suppression of the deterioration of the surface roughness of the silicon (100) plane of the silicon substrate after etching.

Modes for Carrying Out the Invention

[0009] Based on the finding that by using an etching solution in which the content of the primary alkanolamine is 50% by mass or more and the content of the quaternary ammonium is less than 1% by mass for etching the silicon (100) plane, the solubility (etching rate) of the silicon (100) plane can be improved and the surface roughness after etching can be suppressed from deteriorating.

[0010] 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 alkanolamine (Component A) with a content of Component A being 50% by mass or more and does not contain a quaternary ammonium (Component B), or contains a quaternary ammonium (Component B) of less than 1% by mass.

[0011] According to the etching solution of the present disclosure, it is possible to achieve both an improvement in the solubility of the silicon (100) surface during etching and a suppression of the deterioration of the surface roughness of the silicon (100) surface after etching.

[0012] In one or more embodiments, the etching solution of the present disclosure can be used for anisotropic etching such as etching of a silicon wafer, etching in thinning of a silicon wafer, etching in microfabrication (MEMS) technology, and etching manufacturing in solar cell manufacturing.

[0013] Although the details of the mechanism for the expression of the effects of the present disclosure are not clear, it is speculated as follows. When the silicon (100) surface 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 pyramidal irregularities are formed on the surface, resulting in deterioration of the surface roughness. This micropyramid has a bottom surface of (100), sides of (110), and side surfaces of (111) planes, and it is considered that when the apex of the pyramid is masked by foreign matter or the like and there is a difference in the etching rate of each crystal plane, it is generated in a pyramid shape. Although the detailed mechanism is not clear, general alkaline etching agents have a difference in the etching rate of each of the (100), (110), and (111) crystal planes, so micropyramids are generated. However, by using a specific amine compound at a specific concentration or higher, the difference in the etching rate of each of the (100), (110), and (111) crystal planes becomes smaller and the generation of micropyramids can be suppressed. Therefore, it is presumed that the deterioration of the surface roughness can be suppressed without reducing the etching rate. However, the present disclosure may not be construed as being limited to these mechanisms.

[0014] [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 kind or a combination of two or more kinds. The primary alkanolamine in the present disclosure is, in one or more embodiments, a primary alkanolamine having 1 nitrogen atom.

[0015] From the viewpoint of achieving both improved solubility of the silicon (100) surface and suppression of deterioration of surface roughness, the number of carbon atoms of Component A is preferably 2 or more and 10 or less, more preferably 2 or more and 6 or less, and still more preferably 2 or more and 4 or less.

[0016] 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 achieving both improved solubility of the silicon (100) surface and suppression of deterioration of surface roughness, at least one of 2-hydroxyethylamine and monopropanolamine (3-amino-1-propanol) is preferred, and 2-hydroxyethylamine is more preferred.

[0017] From the viewpoint of achieving both improved solubility of the silicon (100) surface and suppression of deterioration of surface roughness, 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 from the same viewpoint, preferably 90% by mass or less, more preferably 80% by mass or less, and still more preferably 70% by mass or less. From the same viewpoint, the content of Component A in the etching solution of the present disclosure is preferably 50% by mass or more and 90% by mass or less, more preferably 50% by mass or more and 80% by mass or less, still more preferably 54% by mass or more and 70% by mass or less, and still more preferably 55% by mass or more and 70% by mass or less. When Component A is a combination of two or more kinds, the content of Component A refers to their total content.

[0018] [Water] In one or more embodiments, the etching solution of the present disclosure contains water as a medium. Examples of the water include distilled water, ion-exchanged water, pure water, and ultrapure water. From the viewpoint of achieving both improved solubility of the silicon (100) surface and suppression of deterioration of the surface roughness, 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, still more preferably 30% by mass or more, and from the same viewpoint, preferably 50% by mass or less, more preferably 48% by mass or less, still more preferably 45% by mass or less. From the same viewpoint, preferably 10% by mass or more and 50% by mass or less, more preferably 20% by mass or more and 48% by mass or less, still more preferably 30% by mass or more and 45% by mass or less.

[0019] (Component B: Quaternary ammonium) From the viewpoint of achieving both improved solubility of the silicon (100) surface and suppression of deterioration of the surface roughness, the etching solution of the present disclosure does not contain quaternary ammonium (hereinafter also referred to as "Component B") or contains less than 1% by mass of quaternary ammonium (Component B). Examples of Component B include quaternary ammonium hydroxides, and for example, quaternary ammonium hydroxides represented by the following formula (I). Component B may be one kind or a combination of two or more kinds. [Chemical formula]

[0020] In the above formula (I), R 1 , R 2 , R 3 and R 4 are each independently at least one selected from a methyl group, an ethyl group, a propyl group, a hydroxymethyl group, a hydroxyethyl group, a hydroxypropyl group, and a benzene ring.

[0021] The quaternary ammonium hydroxide represented by the above formula (I) is a salt composed of a quaternary ammonium cation and hydroxide. For example, 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, tetrakis(2-hydroxypropyl)ammonium hydroxide, and benzyltrimethylammonium hydroxide. Among these, as component B, tetraethylammonium hydroxide (TEAH) is preferable from the viewpoint of achieving both improved solubility of the silicon (100) surface and suppression of deterioration of surface roughness.

[0022] When the etching solution of the present disclosure contains component B, the content of component B in the etching solution of the present disclosure is less than 1% by mass, preferably 0.5% by mass or less, and more preferably 0.1% by mass or less, from the viewpoint of achieving both improved solubility of the silicon (100) surface and suppression of deterioration of surface roughness. When component B is a combination of two or more kinds, the content of component B refers to their total content.

[0023] When the etching solution of the present disclosure contains Component B, the mass ratio B / A of Component A to Component B in the etching solution of the present disclosure is preferably 0.01 or less, more preferably 0.005 or less, and still more preferably 0.002 or less from the viewpoint of achieving both improved solubility of the silicon (100) surface and suppression of deterioration of the surface roughness. The mass ratio B / A is a value calculated by dividing the mass (content) of Component B by the mass (content) of Component A.

[0024] [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 (nonionic 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" means having a solubility of 0.5 g / 100 mL or more, preferably 2 g / 100 mL or more, in water (20 °C). From the viewpoint of adjusting the dissolution rate, in one or more embodiments, 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 EO is preferred from the viewpoint of adjusting the dissolution rate. Examples of Component C include polyethylene glycol (PEG), polypropylene glycol, and the like.

[0025] From the viewpoint of adjusting the dissolution rate, the weight average molecular weight of Component C is preferably 100 or more, more preferably 150 or more, and still more preferably 200 or more, and from the viewpoint of adjusting the dissolution rate, it is preferably 5000 or less, more preferably 2000 or less, and still more preferably 1000 or less. From the same viewpoint, the weight average molecular weight of Component C is preferably 100 or more and 5000 or less, preferably 150 or more and 2000 or less, and still more preferably 200 or more and 1000 or less. The weight average molecular weight of Component C can be measured by the method described in the examples below.

[0026] 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, still more preferably 0.001% by mass or more, from the viewpoint of adjusting the dissolution rate, and, from the same viewpoint, preferably 0.5% by mass or less, more preferably 0.1% by mass or less, still more preferably 0.01% by mass or less. From the same viewpoint, the content of component C in the etching solution of the present disclosure is preferably 0.0001% by mass or more and 0.5% by mass or less, more preferably 0.0005% by mass or more and 0.1% by mass or less, still more preferably 0.001% by mass or more and 0.01% by mass or less. When component C is a combination of two or more, the content of component C refers to their total content.

[0027] [Component D: Chelating agent] The etching solution of the present disclosure can further contain a chelating agent (hereinafter, also referred to as "component D") from the viewpoint of removing metal 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 at least two acid groups selected from carboxy groups and phosphonic acid groups, and from the viewpoint of removing metal foreign matter, it is preferably a compound having 4 or less of the above acid groups. Examples of component D include 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 preferable.

[0028] When the etching solution of the present disclosure contains component D, the content of component D in the etching solution of the present disclosure is preferably 0.01% by mass or more, more preferably 0.05% by mass or more, still more preferably 0.1% by mass or more from the viewpoint of removing metal foreign substances, and preferably 5.0% by mass or less, more preferably 2.5% by mass or less, still more preferably 1.0% by mass or less from the viewpoint of adjusting the dissolution rate. From the same viewpoint, the content of component D in the etching solution of the present disclosure is preferably 0.01% by mass or more and 5.0% by mass or less, more preferably 0.05% by mass or more and 2.5% by mass or less, still more preferably 0.1% by mass or more and 1.0% by mass or less. When component D is a combination of two or more, the content of component D refers to their total content.

[0029] [Inorganic alkali (component E)] In one or more embodiments, the etching solution of the present disclosure may further contain an inorganic alkali (hereinafter also referred to as "component E") from the 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.

[0030] When the etching solution of the present disclosure contains component E, the content of component E in the etching solution of the present disclosure is preferably 0.01% by mass or more, more preferably 0.1% by mass or more, still more preferably 0.5% by mass or more from the viewpoints of adjusting the dissolution rate and suppressing deterioration of surface roughness, and preferably 50% by mass or less, more preferably 30% by mass or less, still more preferably 20% by mass or less from the same viewpoints. From the same viewpoints, the content of component E in the etching solution of the present disclosure is preferably 0.01% by mass or more and 50% by mass or less, more preferably 0.1% by mass or more and 30% by mass or less, still more preferably 0.5% by mass or more and 20% by mass or less. When component E is a combination of two or more, the content of component E refers to their total content.

[0031] [Other components] The etching solution of the present disclosure may further contain or be formulated with other components as long as the effects of the present disclosure are not impaired. Examples of other components include alkali agents other than components A, B, and E, pH adjusters other than components A, B, and E, water-soluble polymers other than component B, surfactants, high-temperature stabilizers, solubilizers, preservatives, rust inhibitors, bactericides, antibacterial agents, antioxidants, defoamers, and the like.

[0032] In one or more embodiments, the etching solution of the present disclosure can be substantially free of 2-(2-aminoethylamino)ethanol. For example, the content of 2-(2-aminoethylamino)ethanol in the etching solution of the present disclosure is preferably less than 1% by mass, more preferably 0.1% by mass or less, and still more preferably 0% by mass (i.e., not contained). In one or more embodiments, the etching solution of the present disclosure can be substantially free of at least one reducing compound selected from hypophosphites, reducing sugars, ascorbic acid, glyoxylic acid, and (+)-catechin, and derivatives thereof. For example, the content of the reducing compound in the etching solution of the present disclosure is preferably less than 0.1% by mass, more preferably 0.01% by mass or less, and still more preferably 0% by mass (i.e., not contained).

[0033] [Method for Producing Etching Solution] In one or more embodiments, the etching solution of the present disclosure can be obtained by blending component A, water, and, if necessary, any of the above-described optional components (component B, component C, component D, component E, other components). Accordingly, in one aspect, the present disclosure relates to a method for producing an etching solution (hereinafter, also referred to as "the method for producing an etching solution of the present disclosure") including a step of blending component A, water, and, if necessary, any of the above-described optional components (component B, component C, component D, component E, other components) (hereinafter, also referred to as "the blending step"). In the present disclosure, "formulating" includes simultaneously or sequentially mixing component A, water, and, if necessary, any of the above-described optional components (component B, component C, component D, component E, and other components). The order of mixing does not particularly need to be limited. The formulating can be performed using a mixer such as a homomixer, homogenizer, ultrasonic disperser, and wet ball mill, for example. In the method for manufacturing an etching solution of the present disclosure, the preferred formulation amounts of the respective components can be the same as the preferred contents of the respective components in the etching solution of the present disclosure described above.

[0034] In the present disclosure, "the content of each component in the etching solution" means, in one or more embodiments, the content of each component in the etching solution used in the etching process, that is, at the time when the use for the etching treatment is started (at the time of use).

[0035] Embodiments of the etching solution of the present 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 they are mixed at the time of use. As an embodiment of the two-component type etching solution, it is composed of a solution containing component A (first solution) and a solution containing at least one selected from component B, component C, component D, component E, and other components (second solution), and the first solution and the second solution are mixed at the time of use. The first solution can contain any of the above-described optional components as necessary.

[0036] In one or more embodiments, the etching solution of the present disclosure is preferably a neutral or alkaline etching solution. For example, from the viewpoint of achieving both an improvement in the solubility of the (100) plane of silicon and suppression of deterioration of the surface roughness, the pH of the etching solution of the present disclosure is preferably 9 or more, more preferably 10 or more, and still more preferably 12 or more. In the present disclosure, the pH of the etching solution is the value at 25°C of the etching solution at the time of use, and can be measured using a pH meter, specifically, by the method described in the examples.

[0037] The etching solution of the present disclosure may be stored and supplied in a concentrated state as long as its stability is not impaired. In this case, it is preferable in terms of reducing manufacturing and transportation costs. And this concentrated solution can be appropriately diluted with water or the like as needed and used in the etching process. A dilution ratio of 1.2 to 100 times is preferable.

[0038] In one or more embodiments, the etching solution of the present disclosure can be applied to anisotropic etching such as etching of silicon wafers, etching in microfabrication (MEMS) technology, etching in solar cell manufacturing, etc., and etching in thinning of silicon wafers. In one or more embodiments, the 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.

[0039] [Kit] In one aspect, the present disclosure relates to a kit for manufacturing the etching solution of the present disclosure (hereinafter, also referred to as "the kit of the present disclosure"). In one or more embodiments, examples of the kit of the present disclosure include a kit containing a solution containing component A. The solution may contain, as needed, any of the above-described components (component B, component C, component D, component E, and other components). In one or more embodiments, examples of the kit of the present disclosure include a kit (two-component type etching solution) that contains a solution containing component A (first liquid) and a solution containing at least one selected from component B, component C, component D, component E, and other components (second liquid) in a state where they are not mixed with each other, and these are mixed at the time of use. After the first liquid and the second liquid are mixed, they may be diluted with water or an aqueous alkali solution as needed. The first liquid or the second liquid may contain all or part of the total amount of water used for preparing the etching solution. The first liquid may contain, as needed, any of the above-described components (component B, component C, component D, component E, and other components). According to the kit of the present disclosure, an etching solution capable of achieving both an improvement in the solubility of the (100) plane of silicon in etching and suppression of deterioration in the surface roughness of the silicon substrate after etching can be produced.

[0040] [Object to be processed] In one or more embodiments, the object to be processed that is etched using the etching solution of the present disclosure includes silicon such as single-crystalline silicon, polycrystalline silicon, polysilicon, and patterned silicon. Among these, at least one selected from single-crystalline silicon, polycrystalline silicon, and polysilicon is preferable, at least one of single-crystalline silicon and polysilicon is more preferable, single-crystalline silicon or polysilicon having a crystal orientation of the (100) plane is still more preferable, and single-crystalline silicon having a crystal orientation of the (100) plane is still more preferable. Examples of the object to be processed include, for example, a silicon wafer, a silicon substrate, a silicon substrate having a silicon oxide film and a silicon nitride film, and a structure in which silicon is patterned.

[0041] [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") including a step of etching silicon using the etching solution of the present disclosure or a mixed solution of an existing chemical and the etching solution of the present disclosure (hereinafter, also referred to as "the etching step"). By using the etching method of the present disclosure, it is possible to achieve both an improvement in the solubility of the (100) plane of silicon in etching and suppression of deterioration in the surface roughness of the silicon substrate after etching, so that the productivity of a semiconductor substrate with improved quality can be improved. Examples of the existing chemicals include, for example, ammonia, TMAH, potassium hydroxide, SC-1 (aqueous solution containing ammonia and hydrogen peroxide), and the like. In one or more embodiments, the mixed solution can be prepared by mixing an existing chemical and 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 prepared by mixing ultrapure water, ammonia, and hydrogen peroxide and the etching solution of the present disclosure. The etching solution of the present disclosure used for preparing the mixed solution is preferably formulated such that the concentration of component A in the mixed solution is 50% by mass or more.

[0042] In the etching step, examples of the etching treatment method include immersion etching and single-wafer etching.

[0043] In the etching step, from the viewpoint of solubility, the temperature of the etching solution during use (etching temperature) is preferably 30°C or higher, more preferably 40°C or higher, still more preferably 50°C or higher, and from the viewpoint of the etching solution life, it is preferably 100°C or lower, more preferably 90°C or lower, still more preferably 80°C or lower. 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, still more preferably 50°C or higher and 80°C or lower. In the etching step, the etching time (etching treatment time) can be appropriately set according to the structure, material, and etching treatment conditions of the silicon substrate. For example, from the viewpoints of improving solubility and suppressing deterioration of the surface roughness, the etching time is preferably 1 minute or longer, more preferably 10 minutes or longer, still more preferably 30 minutes or longer, and from the viewpoint of productivity, it is preferably 120 minutes or shorter, more preferably 90 minutes or shorter, still more preferably 60 minutes or shorter. More specifically, the etching time is preferably 1 minute or longer and 120 minutes or shorter, more preferably 10 minutes or longer and 90 minutes or shorter, still more preferably 30 minutes or longer and 60 minutes or shorter.

[0044] In one or more embodiments, the etching method of the present disclosure may include, in addition to the above etching process, a cleaning process, a rinsing process, a drying process, etc. The cleaning process and / or the rinsing process may be performed before, after, or both (before and after) the etching process. The drying process may be performed after the cleaning process and / or the rinsing process. For example, the etching method of the present disclosure may include, after the etching process, a rinsing process of rinsing the silicon after the etching treatment with water or the like, and a drying process of drying the rinsed silicon.

Example

[0045] Hereinafter, the present disclosure will be specifically described by way of examples, but the present disclosure is not limited by these examples in any way.

[0046] 1. Preparation of etching solution (Examples 1 to 9 and Comparative Examples 1 to 5) The etching solutions of Examples 1 to 9 and Comparative Examples 1 to 5 were prepared by mixing the respective components shown in Table 1 and water (ultrapure water). The pH of the prepared etching solution was 12 to 14. The content of each component in Table 1 is the content of each component (mass%, active ingredient) at the time of use of the etching solution. The content of water is the remainder excluding component A or non-component A, component B, and the additive. The content of water also includes the content of water contained in the TEAH aqueous solution or aqueous ammonia.

[0047] The following components were used for the preparation of the etching solution. (Component A) 2-Hydroxyethylamine [Tokyo Chemical Industry Co., Ltd.] (Non-component A) Aminoethylethanolamine [Tokyo Chemical Industry Co., Ltd.] (Component B) TEAH: Tetraethylammonium hydroxide [35 mass% TEAH aqueous solution, Tokyo Chemical Industry Co., Ltd.] (Component C) PEG: Polyethylene glycol [manufactured by Tokyo Chemical Industry Co., Ltd., weight average molecular weight 200] (Non-component C) Propylene glycol [manufactured by Tokyo Chemical Industry Co., Ltd.] (Component D) Maleic acid [manufactured by FUJIFILM Wako Pure Chemical Corporation] Picolinic acid [manufactured by Tokyo Chemical Industry Co., Ltd.] (Component E) Ammonia [28 mass% aqueous ammonia, manufactured by Kishida Chemical Co., Ltd., special grade reagent]

[0048] 2. Measurement method for each parameter [pH of the etching solution] The pH value of the etching solution at 25 °C is the value measured using a pH meter (manufactured by TOA DKK Corporation), and is the value after 1 minute of immersing the electrode of the pH meter in the etching solution.

[0049] [Weight average molecular weight of the water-soluble polymer (Component C)] The weight average molecular weight of the water-soluble polymer (Component C) was calculated based on the peak in the chromatogram obtained by applying the gel permeation chromatography (GPC) method under the following conditions. <Measurement conditions> Apparatus: HLC-8320 GPC (manufactured by Tosoh Corporation, detector integrated type) Column: α-M + α-M Eluent: 0.15 mol / L Na 2 SO 4 , 1 mass% acetic acid, solvent: water Flow rate: 1.0 mL / min Column temperature: 40 °C Detector: Shodex RI SE-61 differential refractive index detector Standard substance: Pullulan with known molecular weight

[0050] 3. Evaluation of the etching solution [Dissolution rate (etching rate) of the silicon (100) surface] The silicon wafer was cut into 4×2 cm pieces using a diamond cutter to prepare test specimens. The mass (g) of the test specimens was measured to four decimal places using an electronic balance (manufactured by Sartorius). Then, the specimens were immersed in acetone for 1 minute so that the entire surface was submerged, then rinsed thoroughly with ultrapure water, then immersed in ammonium hydrogen fluoride diluted to 1% with ultrapure water for 1 minute so that the entire surface was submerged, then rinsed thoroughly with ultrapure water, and then dried with an air blow. 30 g of the prepared etching solution was weighed into a 30 ml plastic container made of PE, and the test specimens were immersed so that the entire surface was submerged. They were left standing in a constant temperature bath (manufactured by ESPEC, model: PU-4J) set at 60 °C for 1 hour for etching. Then, the test specimens were taken out of the constant temperature bath, rinsed thoroughly with ultrapure water, and dried with an air blow. And the mass (g) of the test specimens was measured to four decimal places using an electronic balance (manufactured by Sartorius). The weight of the test specimen after immersion was subtracted from the weight of the test specimen before immersion, and the difference was taken as the (100) surface dissolution amount (mg). And the value obtained by dividing the (100) surface dissolution amount (mg) by the immersion time (min) was taken as the dissolution rate (mg / min). The results are shown in Table 1. The silicon wafers used are as follows. Type: (100) single-sided mirror wafer (single-crystalline silicon with a crystal orientation of the 100 plane) Resistance: ≤1 Ω·cm Thickness: 1000 ± 25 μm Oriental flat: Notch specification Particles: Irrespective

[0051] [Surface roughness] The surface roughness of the sample pieces after the above etching process was measured. The surface roughness was measured using an AFM (manufactured by BRUKER, model: Dimension Icon) under the conditions shown below with the center of the mirror side. The results are shown in Table 1. (Measurement conditions of AFM) Mode: Scan Asyst Area: 10×10 μm Scan rate: 1.0 Hz Cantilever: RTESPA-300 (manufactured by BRUKER) Line: 512×512

[0052] [Dissolution rate / surface roughness of silicon (100) plane] The ratio of the dissolution rate to the surface roughness of the silicon (100) plane obtained above (dissolution rate / surface roughness) was calculated, and the results are shown in Table 1. The higher the value of the ratio (dissolution rate / surface roughness), the better the etching solution can be evaluated as an etching solution with excellent effects of improving the etching rate and suppressing the deterioration of the surface roughness.

[0053]

Table 1

[0054] As shown in Table 1, the etching solutions of Examples 1 to 9 in which the content of the primary alkanolamine (Component A) is 50% by mass or more and the content of the quaternary ammonium (Component B) is less than 1% by mass are compared with the etching solutions of Comparative Examples 1 to 2 in which the content of Component B is 1% by mass or more, the etching solution of Comparative Example 3 in which the content of Component A is less than 50% by mass and the content of Component B is 1% by mass or more, and the etching solutions of Comparative Examples 4 to 5 containing aminoethyl ethanolamine (non-Component A) as the amine. The solubility of the silicon (100) plane was improved, and the deterioration of the surface roughness of the silicon (100) plane was suppressed.

Industrial applicability

[0055] The etching solution of the present disclosure is useful as an etching solution capable of achieving both improvement in solubility of the silicon (100) plane and suppression of deterioration of surface roughness.

Claims

Claim 1 containing a primary alkanolamine (Component A), the content of Component A is 50% by mass or more, an etching solution for silicon that does not contain a quaternary ammonium (Component B) or contains less than 1% by mass of a quaternary ammonium (Component B). Claim 2 The etching solution according to claim 1, wherein Component A is 2-hydroxyethylamine. Claim 3 The etching solution according to claim 1 or 2, wherein the silicon is single-crystalline silicon having a crystal orientation of the 100 plane. Claim 4 The etching solution according to any one of claims 1 to 3, wherein the temperature of the etching solution during use is 40°C or higher.

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