Etching solution for silicon

Abstract

In one aspect, an etching solution capable of improving the solubility of the (111) plane of silicon in etching is provided.SOLUTION: In one aspect, the present disclosure relates to an etching solution for silicon, comprising a cationic surfactant (component A), wherein the component A is at least one of a quaternary ammonium or a salt thereof having two or more alkyl groups having 10 to 18 carbon atoms in a molecule (component A1), and a quaternary phosphonium or a salt thereof having one or more alkyl groups having 10 to 18 carbon atoms in a molecule (component A2).SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present disclosure relates to a silicon etching solution and an etching method using the same. [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.

[0003] Conventional wet etching uses an alkaline aqueous solution containing potassium hydroxide, tetramethylammonium hydroxide (TMAH), or the like. For example, Patent Document 1 proposes a method for etching a silicon wafer using an etching solution prepared by adding a cationic surfactant, an amphoteric surfactant, or an organic polymer having a polar group to an alkaline aqueous solution. Patent Document 2 proposes an anisotropic silicon etching solution in the field of micromachining technology, which contains an alkaline compound, which is a mixture of an organic alkali and an inorganic alkali, and a silicon-containing compound. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2004-48026 [Patent Document 2] Japanese Patent Application Laid-Open No. 2009-206335 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. For example, Patent Document 1 proposes an etching method for improving flatness and surface roughness. However, in recent years, requirements for the surface quality of silicon substrates have become increasingly stringent, and there is a demand for an etching method that can suppress deterioration of flatness, surface roughness, haze, etc. In wet etching of silicon, the etching rate is thought to be slower for the (111) plane than for the (100) and (110) planes due to the dependence of the etching rate on the crystal orientation. For example, when a (100) single-crystal silicon substrate is etched with an alkaline solution containing hydroxy ions, the difference in etching rate between the (111) and (100) planes present on the surface creates convex portions, which causes problems such as worsening surface roughness and haze. Furthermore, in the wet etching process for MEMS devices, improved etching speed for the (111) plane is expected to improve the processing accuracy of surface shapes and productivity.

[0006] Therefore, the present disclosure provides a silicon etching solution that can improve the solubility of the (111) plane of silicon during etching, and a silicon etching method using the same. [Means for solving the problem]

[0007] In one aspect, the present disclosure provides a silicon ester containing a cationic surfactant (component A), wherein component A is at least one of a quaternary ammonium having two or more alkyl groups having 10 to 18 carbon atoms in the molecule or a salt thereof (component A1), and a quaternary phosphonium having one or more alkyl groups having 10 to 18 carbon atoms in the molecule or a salt thereof (component A2). Regarding etching solutions.

[0008] In one aspect, the present disclosure relates to a silicon etching method including a step of etching silicon using the etching solution of the present disclosure or a mixture of an existing chemical agent and the etching solution of the present disclosure. [Effects of the Invention]

[0009] According to one aspect of the present disclosure, an etching solution capable of improving the solubility of the (111) plane of silicon during etching can be provided. DETAILED DESCRIPTION OF THE INVENTION

[0010] [Etching solution] 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 includes a cationic surfactant (component A), where component A is at least one of a quaternary ammonium having two or more alkyl groups having from 10 to 18 carbon atoms in the molecule or a salt thereof (component A1), and a quaternary phosphonium having one or more alkyl groups having from 10 to 18 carbon atoms in the molecule or a salt thereof (component A2).

[0011] The etching solution of the present disclosure can improve the solubility of the (111) plane of silicon during etching.

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

[0013] Although the details of the mechanism by which the effects of the present disclosure are manifested are not clear, it is presumed as follows. In the present disclosure, at least one cationic surfactant is used, which is a quaternary ammonium or salt thereof having two or more long alkyl chains (component A1) and a quaternary phosphonium or salt thereof having one or more long alkyl chains (component A2). The hydrophobic long alkyl chains are adsorbed onto the hydrophobic (111) surface, and the positively charged cationic portion (N + , P + ) attracts the negatively charged hydroxyl ions, which act as a dissolving agent, and It is believed that etching proceeds or is etched by the cationic surfactant. Furthermore, it is believed that the etching reaction proceeds more rapidly as the hydrophobicity of the cationic surfactant increases and the amount of adsorption to the (111) surface increases. Therefore, it is believed that highly hydrophobic cationic surfactants with two or more long alkyl chains have better etching performance than those with one long alkyl chain. However, the present disclosure need not be construed as being limited to these mechanisms.

[0014] [Cationic surfactant (ingredient A)] The etching solution of the present disclosure contains a cationic surfactant (hereinafter also referred to as "component A"). Component A is at least one of a quaternary ammonium having two or more alkyl groups having from 10 to 18 carbon atoms in the molecule or a salt thereof (hereinafter also referred to as "component A1"), and a quaternary phosphonium having one or more alkyl groups having from 10 to 18 carbon atoms in the molecule or a salt thereof (hereinafter also referred to as "component A2"). Component A1 may be one type or a combination of two or more types. Component A2 may be one type or a combination of two or more types. Component A may be one type or a combination of two or more types. In the present disclosure, "quaternary ammonium having two or more alkyl groups having 10 to 18 carbon atoms in the molecule" means, in one or more embodiments, that at least two alkyl groups having 10 to 18 carbon atoms are bonded to a nitrogen atom. In the present disclosure, "quaternary phosphonium having one or more alkyl groups having 10 to 18 carbon atoms in the molecule" means, in one or more embodiments, that at least two alkyl groups having 10 to 18 carbon atoms are bonded to a nitrogen atom. In one or more embodiments, the term "aluminum" means that at least one alkyl group having 10 to 18 carbon atoms is bonded to the phosphorus atom. From the viewpoint of improving the solubility of the silicon (111) plane, the number of carbon atoms in the alkyl group is 10 or more, preferably 11 or more, more preferably 12 or more, and 18 or less, preferably 16 or less, and more preferably 15 or less. From the same viewpoint, the number of carbon atoms in the alkyl group is 10 or more and 18 or less, preferably 11 or more and 18 or less, preferably 12 or more and 18 or less, more preferably 12 or more and 16 or less, and even more preferably 12 or more and 15 or less. In the case of component A1, the number of alkyl groups having 10 to 18 carbon atoms in the molecule can be 2 or more, 3 or more, or 4, preferably 2 or 3, and more preferably 2. In the case of component A2, the number can be 1 or more, 2 or more, 3 or more, or 4, preferably 1 or 2.

[0015] From the viewpoint of improving the solubility of the silicon (111) plane, the total number of carbon atoms in the molecule of component A is preferably 22 or more, more preferably 24 or more, even more preferably 26 or more, and is preferably 38 or less, more preferably 34 or less, and even more preferably 32 or less. From the same viewpoint, the total number of carbon atoms in the molecule of component A is preferably 22 or more and 38 or less, more preferably 24 or more and 38 or less, even more preferably 26 or more and 38 or less, even more preferably 26 or more and 34 or less, and even more preferably 26 or more and 32 or less.

[0016] In one or more embodiments, from the viewpoint of improving the solubility of the silicon (111) plane, Component A is preferably a compound having a structure represented by the following formula (I) or (II): [ka]

[0017] In the formula (I), R 1 are the same or different and represent alkyl groups having 10 to 18 carbon atoms. and R 2 are the same or different and are hydrocarbon groups having 1 to 6 carbon atoms or -(CH2CH2O) nH (where n is 1 to 3), Z is a phosphorus atom, and X - is the counterion. In the formula (II), R 1 are the same or different and each represents an alkyl group having 10 to 18 carbon atoms. indicates R 2 are the same or different and are hydrocarbon groups having 1 to 6 carbon atoms or -(CH2CH2O ) n H (where n is 1 to 3), Z is a nitrogen atom or a phosphorus atom, and X - is the counterion. In the formulas (I) and (II), R 2 The reason for this is the improvement of the solubility of the (111) surface of silicon. From this viewpoint, a hydrocarbon group having 1 to 6 carbon atoms is preferable. Examples of the counter ion include a chloride ion (Cl - ), bicarbonate ion (HCO3 - ), bromide ion (Br - ) etc.

[0018] Examples of component A1 include didecyl dimethyl ammonium salt, dialkyl dimethyl ammonium salt (C12-C18 mixed product), and distearyl dimethyl ammonium salt. At least one selected from the following can be mentioned. Examples of component A2 include trihexyltetradecylphosphonium salts.

[0019] The content of component A in the etching solution of the present disclosure is preferably 5 ppm or more, more preferably 20 ppm or more, even more preferably 50 ppm or more, and still more preferably 80 ppm or more from the viewpoint of improving the solubility of the silicon (111) plane, and is preferably 100,000 ppm or less, more preferably 10,000 ppm or less, and even more preferably 1,000 ppm or less from the viewpoint of solution stability. From the viewpoint of improving the solubility of the silicon (111) plane and the solution stability, the content of component A in the etching solution of the present disclosure is 5 ppm or more and 100,000 ppm or less. Preferably, 20 ppm or more and 10,000 ppm or less is more preferable, and 80 ppm or more is more preferable. It is more preferable that the content of Component A is 1,000 ppm or less. The content refers to the total content of these. In the present disclosure, 10,000 ppm is equal to 1% by mass (the same applies hereinafter).

[0020] [water] In one or more embodiments, the etching solution of the present disclosure contains water as a medium. Examples of water include distilled water, ion-exchanged water, pure water, and ultrapure water. The water content in the etching solution of the present disclosure is preferably 50% by mass or more, more preferably 70% by mass or more, and even more preferably 80% by mass or more, from the viewpoint of solution stability, and is preferably 99.9995% by mass or less, more preferably 99.9990% by mass or less, and even more preferably 99.9980% by mass or less, from the viewpoint of improving the solubility of the silicon (111) plane.

[0021] [Alkaline agent (ingredient B)] In one or more embodiments, the etching solution of the present disclosure may further contain an alkaline agent (hereinafter also referred to as "component B") from the viewpoint of further improving the solubility of the silicon (111) plane. In one or more embodiments, component B does not contain component A. In one or more embodiments, Component B includes at least one selected from inorganic alkalis and organic alkalis, with inorganic alkalis being preferred. Examples of the inorganic alkali include ammonia; alkali metal hydroxides such as potassium hydroxide and sodium hydroxide; and the like. Examples of the organic alkali include hydroxyalkylamines, quaternary ammonium salts, etc. Examples of the hydroxyalkylamines include monoethanolamine, diethanolamine, methylethanolamine, methyldiethanolamine, aminoethylethanolamine, etc. Examples of the quaternary ammonium salts include tetramethylammonium hydroxide (TMAH), tetraethylammonium hydroxide (TEAH), etc. Component B may be one type or a combination of two or more types.

[0022] In one or more embodiments, the content of component B in the etching solution of the present disclosure can be set so that the pH of the etching solution falls within a specific range.

[0023] [Other ingredients] The etching solution of the present disclosure may further contain or be blended with other components, provided that the effects of the present disclosure are not impaired. Examples of other components include surfactants other than Component A, pH adjusters other than Component B, high-temperature stabilizers, chelating agents, solubilizers, preservatives, rust inhibitors, disinfectants, antibacterial agents, antioxidants, and antifoaming agents.

[0024] [Method of manufacturing etching solution] In one or more embodiments, the etching solution of the present disclosure can be obtained by mixing component A, water, and, as necessary, the above-described optional components (component B 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, water, and, as necessary, the above-described optional components (component B, other components) (hereinafter also referred to as the "blending step"). In the present disclosure, "blending" includes simultaneously or sequentially mixing component A, water, and, if necessary, the optional components described above (component B, 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.

[0025] 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).

[0026] An embodiment 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 components are mixed at the time of use. One embodiment of a two-component etching solution is one that is composed of an additive solution (first component) containing component A and an alkaline aqueous solution (second component) containing component B, and the first and second components are mixed at the time of use. The first and second components may each contain the optional components described above as necessary.

[0027] 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 4 or higher, more preferably 5 or higher, and even more preferably 6 or higher, from the viewpoint of improving the solubility of the silicon (111) plane. In the present disclosure, the pH of the etching solution is the value at 25°C of the etching solution during use, and can be measured using a pH meter, specifically, by the method described in the Examples.

[0028] 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 5 to 100 times.

[0029] 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 micromachining (MEMS) technology, and etching in solar cell manufacturing. 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.

[0030] [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 including an additive solution containing component A. The additive solution may contain the optional components described above, as necessary. In one or more embodiments, the kit of the present disclosure includes a kit (two-component etching solution) that contains an additive solution (first liquid) containing component A and an alkaline aqueous solution (second liquid) containing component B in a mutually unmixed state, and that is mixed at the time of use. After the first liquid and the second liquid are mixed, they may be diluted with water or an alkaline aqueous solution as needed. The first or second liquid may contain all or part of the water used to prepare the etching liquid. The first and second liquids may each contain the optional components described above, as necessary. The kit of the present disclosure makes it possible to produce an etching solution that can improve the solubility of the (111) plane of silicon during etching.

[0031] [Processing object] 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 polycrystalline silicon is more preferred, and single crystal silicon is even more preferred. Examples of the workpiece include 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.

[0032] [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 mixed solution of an existing chemical and the etching solution of the present disclosure. Use of the etching method of the present disclosure can improve the solubility of the (111) plane of silicon during etching, thereby improving the productivity of semiconductor substrates with improved quality. Existing chemicals include ammonia, TMAH, potassium hydroxide, SC-1( Examples include aqueous solutions containing ammonia and hydrogen peroxide. In one or more embodiments, the mixed solution can be prepared by blending an existing chemical 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 existing drug used in preparing the mixed solution is preferably blended so that the proportion of the existing drug in the mixed solution is 90 mass % or more, for example. 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 5 ppm to 10 mass %.

[0033] In the etching step, examples of the etching method include immersion etching and single wafer etching. In the etching step, the etching temperature of the etching solution is not particularly limited, and may be, for example, 25°C or higher and 80°C or lower. In the etching step, the etching time can be appropriately set depending on the structure and material of the silicon substrate and the etching treatment conditions, and may be, for example, from 1 minute to 120 minutes.

[0034] 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. [Example]

[0035] The present disclosure will be specifically described below using examples, but the present disclosure is not limited to these examples in any way.

[0036] 1. Preparation of Etching Solution (Examples 1 to 12 and Comparative Examples 1 to 3) (Examples 1 to 10, Comparative Example 3) The cationic surfactant (component A or non-component A) shown in Table 1 and ultrapure water were mixed to obtain etching solutions of Examples 1 to 10 and Comparative Example 3. (Examples 11 to 12) The cationic surfactant (component A), ammonia (component B), and ultrapure water shown in Table 1 were mixed to obtain the etching solutions of Examples 11 and 12. (Comparative Example 1) The etching solution used in Comparative Example 1 was ultrapure water. (Comparative Example 2) An etching solution of Comparative Example 2 was obtained by mixing ammonia (component B) and ultrapure water. The content of each component in Table 1 is the content (ppm, active ingredient) of each component at the time of use of the polishing composition. The content of water is the remainder excluding component A or non-component A and component B.

[0037] The following components were used to prepare the etching solution. (Component A) Didecyldimethylammonium chloride [Kao Corporation, Kotamin D10E] (in formula (II), R 1 :C 10 H 21 , R 2 :CH3, Z:N, X:Cl - ) Dialkyl (C12-18) dimethyl ammonium chloride [Kao Corporation, Kohtamin D2345P] (in formula (II), R 1 : C12-18 alkyl group, R 2 :CH3, Z:N, X:Cl - ) Distearyldimethylammonium chloride [manufactured by Tokyo Chemical Industry Co., Ltd.] (in formula (II), R 1 :C 18 H 37 , R 2 :CH3, Z:N, X:Cl - ) Didecyldimethylammonium bicarbonate [Carboquat HE, manufactured by Lonza Japan] (in formula (II), R 1 :C 10 H 21 , R 2 :CH3, Z:N, X:HCO3 - ) Trihexyltetradecylphosphonium bromide [manufactured by Tokyo Chemical Industry Co., Ltd.] (in formula (I), R 1 :C 14 H 29 , R 2 :C6H 13 , Z:P, X:Br - ) (Non-ingredient A) Lauryltrimethylammonium chloride [Kao Corporation, Kotamin 24P] (Component B) NH3: Ammonia [28% by mass ammonia water, manufactured by Kishida Chemical Co., Ltd., special grade reagent]

[0038] 2.Measuring methods for each parameter [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.

[0039] 3.Evaluation of etching solutions [111-plane dissolution amount] An 8-inch (111) plane single crystal silicon is cut into 4 x 4 cm pieces using a diamond cutter to prepare a test piece. The mass (g) of the test piece is measured to 4 decimal points using an electronic balance (manufactured by Sartorius). The test piece was 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, then dried with air blower. and dried. 100 g of the prepared etching solution was weighed into a disposable cup, and the test piece was immersed so that the entire surface was immersed. The test piece was then placed in a thermostatic chamber (manufactured by ESPEC, model: PU-4J) set at 60°C for 24 hours to perform etching. The test piece was then removed from the thermostatic chamber, the entire surface was rinsed with ultrapure water, and the test piece was dried with an air blower. The mass (g) of the test piece was then measured using an electronic balance (manufactured by Sartorius) to the nearest tenth of a decimal point. The weight of the test piece after immersion was subtracted from the weight before immersion, and the difference was taken as the amount of 111 surface dissolved (mg). The silicon wafers used were as follows: Type: (111) 4°off single-sided mirror wafer Resistance: ≦1Ω·cm Thickness: 1000±25μm Orientation flat: Notch specification Particles: Any

[0040] [Table 1]

[0041] As shown in Table 1, the etching solutions of Examples 1 to 12 containing a specific cationic surfactant (component A) had improved solubility of the silicon (111) plane compared to Comparative Examples 1 to 3 which did not contain component A. The etching solutions of Examples 11 and 12 containing a specific cationic surfactant (component A) and an alkaline agent (component B) had improved solubility of the silicon (111) plane compared to Examples 1 to 10 which did not contain component B. The solubility of the (111) surface of silicon was further improved. [Industrial Applicability]

[0042] The etching solution of the present disclosure is useful as an etching solution that can improve the solubility of the (111) plane of silicon.

Claims

1. containing a cationic surfactant (component A), Component A is at least one of a quaternary ammonium or a salt thereof having two or more alkyl groups having from 10 to 18 carbon atoms in the molecule (component A1), and a quaternary phosphonium or a salt thereof having one or more alkyl groups having from 10 to 18 carbon atoms in the molecule (component A2).

2. 2. The etching solution according to claim 1, wherein the total number of carbon atoms in the molecule of component A is 22 or more and 38 or less.

3. 3. The etching solution according to claim 1, wherein component A is a compound having a structure represented by the following formula (I) or (II): 【Chemistry 1】 In the formula (I), R 1 are the same or different and represent alkyl groups having 10 to 18 carbon atoms. S, R 2 are the same or different and each represents a hydrocarbon group having 1 to 6 carbon atoms or -(CH 2 CH 2 O) n H (where n is 1 to 3), Z is a phosphorus atom, and X - is the counterion. In the formula (II), R 1 are the same or different and each represents an alkyl group having 10 to 18 carbon atoms. Show, R 2 are the same or different and each represents a hydrocarbon group having 1 to 6 carbon atoms or -(CH 2 CH 2 O ) n H (where n is 1 to 3), Z is a nitrogen atom or a phosphorus atom, and X - is the counterion.

4. The etching solution according to claim 1 , further comprising an alkaline agent (component B).

5. The etching solution according to claim 1 , which is a neutral or alkaline etching solution.

6. A silicon etching method comprising the step of etching silicon using the etching solution according to any one of claims 1 to 5 or a mixed solution of an existing chemical agent and the etching solution according to any one of claims 1 to 5.

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