Etching liquid

Abstract

The present application provides, in one embodiment, an etching solution that can inhibit the deposition of silicon dioxide generated in an etching process from adhering to a silicon oxide film. The present application relates, in one embodiment, to an etching solution that is an etching solution used in a process for removing a silicon nitride film from a substrate having a silicon nitride film and a silicon oxide film, which contains a siloxane compound modified by a compound having an alkyleneoxy group, phosphoric acid, and water.

Description

Technical Field

[0001] This invention relates to an etching solution for silicon nitride films, an etching method using the same, and a method for manufacturing semiconductor substrates. Background Technology

[0002] In the manufacturing process of semiconductor devices, a step is performed to selectively etch away the SiN film from a substrate having a silicon nitride film (hereinafter also referred to as "SiN film") and a silicon oxide film (hereinafter also referred to as "SiO2 film"). Conventionally, as an etching method for SiN film, a method using phosphoric acid at a high temperature of 150 degrees Celsius or higher is known.

[0003] In recent years, the semiconductor industry has been advancing towards high integration, which requires more complex and miniaturized wiring. Methods to improve the etching rate ratio of SiN film to SiO2 film have been disclosed.

[0004] Japanese Patent Application Publication No. 2016-29717 (Patent Document 1) discloses an etching composition comprising a first inorganic acid, at least one silane inorganic acid salt produced by reacting a second inorganic acid with a silane compound, and a solvent.

[0005] Japanese Patent Application Publication No. 2018-85513 (Patent Document 2) discloses an etching composition comprising an inorganic acid, a siloxane compound, an ammonium compound, and a solvent.

[0006] Japanese Patent Application Publication No. 2020-96162 (Patent Document 3) discloses an etching solution that is made by combining an organophosphonic acid compound, phosphoric acid, and water.

[0007] In addition, as a method for selectively removing SiN film from SiO2 film and SiN film, for example, International Publication No. 2021 / 242755 (Patent Document 4) discloses a polishing fluid composition comprising cerium oxide coated inorganic oxide particles, a silicone compound having at least one group selected from ethyleneoxy (EO) and propyleneoxy (PO) and substituted ethylenediamino, a nonionic organic molecule having at least two hydroxyl groups, and a solvent. Summary of the Invention

[0008] In one aspect, the present invention relates to an etching solution for a process of removing a silicon nitride film from a substrate having a silicon nitride film and a silicon oxide film, comprising a siloxane compound modified with a compound having an alkylene oxide, phosphoric acid, and water.

[0009] In one aspect, the present invention relates to an etching method comprising a step of removing a silicon nitride film from a substrate having a silicon nitride film and a silicon oxide film using an etching solution of the present invention.

[0010] In one aspect, the present invention relates to a method for manufacturing a semiconductor substrate, comprising a step of removing a silicon nitride film from a substrate having a silicon nitride film and a silicon oxide film using an etching solution of the present invention, wherein the substrate is a semiconductor substrate. Detailed Implementation

[0011] In recent years, the semiconductor industry has been advancing towards higher integration, demanding more complex and miniaturized wiring, and requiring more efficient removal of silicon nitride films. Especially in the manufacturing process of three-dimensional semiconductor devices such as 3D NAND flash memory, from a productivity and yield perspective, there is a need to further improve the etching rate ratio between SiN films and SiO2 films. Furthermore, in conventional etching methods using phosphoric acid at temperatures above 150°C, a portion of the SiN film decomposes into silicic acid (Si(OH)4) and ammonium phosphate ((NH4)3PO4), while some silicic acid undergoes a dehydration reaction to generate silicon dioxide (SiO2), which precipitates and adheres to the SiO2 film. Therefore, there is a particular need for an etching solution that can suppress the precipitation and adhesion of silicon dioxide to the SiO2 film even when the concentration of silicon dioxide generated during the etching process is high (e.g., 200 ppm).

[0012] Therefore, the present invention provides an etching solution that can suppress the precipitation of silicon dioxide generated in the etching process, an etching solution that adheres to the silicon oxide film, an etching method using the same, and a method for manufacturing a semiconductor substrate.

[0013] According to one aspect of the present invention, an etching solution is provided that can suppress the precipitation of silicon dioxide generated during the etching process and its adhesion to the silicon oxide film.

[0014] In one or more embodiments, the present invention relates to an etching solution (hereinafter also referred to as "the etching solution of the present invention"), which is used in a process of removing a silicon nitride film from a substrate having a silicon nitride film and a silicon oxide film, and contains a siloxane compound modified by a compound having an alkylene oxide, phosphoric acid, and water.

[0015] The etching solution of the present invention can suppress the precipitation of silicon dioxide generated in the etching process and its adhesion to the silicon oxide film.

[0016] The details of the mechanism by which the effects of this invention are manifested are not yet clear, but the following can be speculated.

[0017] It can be considered that, in this invention, a siloxane compound modified with a compound having an alkylene oxide group, such as the siloxane compound represented by formula (II), is adsorbed onto the surface of the Si(OH)4, silicon dioxide, or SiO2 film generated during the etching process. Furthermore, when adsorbed onto the surface of the SiO2 film, the precipitation and adhesion of silicon dioxide are suppressed by the protective film effect; when adsorbed onto silicon dioxide, the adhesion of silicon dioxide is suppressed by the repulsion between the aforementioned siloxane compound adsorbed on the surface of the SiO2 film.

[0018] However, the present invention may also be interpreted in ways that are not limited to these mechanisms.

[0019] In one or more embodiments, the etching solution of the present invention can be prepared by combining a siloxane compound modified with a compound having an alkylene oxide, phosphoric acid, water, and optional components as needed. That is, in one or more embodiments, the etching solution of the present invention is prepared by combining a siloxane compound modified with a compound having an alkylene oxide, phosphoric acid, and water.

[0020] In this invention, "composed of..." means that in addition to siloxane compounds modified with compounds having alkylene oxides, phosphoric acid, and water, optional components may be added as needed. Furthermore, in this invention, the amount of each component in the etching solution can be referred to as its content in the etching solution.

[0021] [Siloxane compounds modified by compounds having alkylene oxides]

[0022] In one or more embodiments, the etching solution of the present invention contains a siloxane compound modified with a compound having an alkylene oxide group. In one or more embodiments, the etching solution of the present invention incorporates a siloxane compound modified with an alkylene oxide group. The siloxane compound modified with an alkylene oxide group may be used alone or in combination with two or more. Examples of alkylene oxide groups include at least one selected from ethylene oxide (EO) and propylene oxide (PO), with EO being preferred from the viewpoint of suppressing silica precipitation and adhesion to the SiO2 film.

[0023] From the viewpoint of suppressing the precipitation and adhesion of silicon dioxide to the SiO2 film, the siloxane compound modified by the compound having an alkylene oxide in the present invention is preferably a siloxane compound having the structure represented by the following formula (I), and more preferably a siloxane compound represented by the following formula (II).

[0024] [Chemical Formula 1]

[0025]

[0026] In formula (I) above, R is an alkyl group with 1 or more carbon atoms and 5 or less, a hydroxyalkyl group with 1 or more carbon atoms and 5 or less, an alkoxy group with 1 or more carbon atoms and 5 or less, or an anionic group. t is 1 or more and 50 or less, and r is 1 or more and 30 or less.

[0027] [Chemical Formula 2]

[0028]

[0029] In formula (II) above, R is an alkyl group with 1 or more carbon atoms and 5 or less, a hydroxyalkyl group with 1 or more carbon atoms and 5 or less, an alkoxy group with 1 or more carbon atoms and 5 or less, or an anionic group. t / (s+t)×100 is 4 or more, and r is 1 or more and 30 or less.

[0030] In the above formulas (I) and (II), anionic groups include, for example, phosphonic acid groups, sulfate groups, carboxylic acid groups or phosphate groups (-O-PO-(OH)2).

[0031] From the viewpoint of suppressing the precipitation of silica and its adhesion to the SiO2 film, R in the above formulas (I) and (II) is preferably an alkyl group with 1 or more and 5 or less carbon atoms, an alkoxy group with 1 or more and 5 or less carbon atoms, or an anionic group, more preferably a methyl group, a methoxy group, or a phosphate group, and even more preferably a phosphate group.

[0032] In formula (II) above, from the viewpoint of suppressing silicon dioxide precipitation and adhesion to the SiO2 film, t / (s+t)×100 is 4 or more, preferably 7 or more, more preferably 10 or more, even more preferably 15 or more, even more preferably 20 or more, even more preferably 30 or more, even more preferably 40 or more, and preferably 100 or less, more preferably 80 or less, even more preferably 70 or less, even more preferably 60 or less. From the same viewpoint, t / (s+t)×100 is preferably 4 or more and 100 or less, more preferably 7 or more and 100 or less.

[0033] In the above formulas (I) and (II), from the same point of view, t is preferably 1 or more and 50 or less, and more preferably 1 or more and 30 or less.

[0034] In the above formulas (I) and (II), r is 1 or more and 30 or less. From the same point of view, it is preferred to be 1 or more and 25 or less, and more preferably 3 or more and 20 or less.

[0035] From the viewpoint of suppressing silica precipitation and adhesion to the SiO2 film, the HLB of the siloxane compound modified with the aforementioned compound having alkylene oxides is preferably 4 or more, more preferably 5 or more, and even more preferably 10 or more. Here, HLB is a base number determined using the functional groups described in Davis, JT; Proc. Intern. Congr. Surface Activity, 2nd, London, 1, 426 (1957), and the HLB value is defined as "7 + the sum of the base numbers of hydrophilic groups - the sum of the base numbers of lipophilic groups".

[0036] Examples of siloxane compounds modified with compounds having alkylene oxides include at least one selected from PEG-7 polydimethylsiloxane phosphate (HLB: 14.6), PEG-3 polydimethylsiloxane (HLB: 4.5), PEG-10 polydimethylsiloxane (HLB: 4.5 or 14), and trisiloxane ethoxide (HLB: 5.4).

[0037] From the viewpoint of suppressing silica precipitation and adhesion to the SiO2 film, the amount of the siloxane compound modified with the alkylene oxide compound in the etching solution of the present invention is preferably 0.03% by mass or more, more preferably 0.04% by mass or more, and even more preferably 0.05% by mass or more. Furthermore, from the same viewpoint, it is preferably 0.2% by mass or less, more preferably 0.15% by mass or less, and even more preferably 0.1% by mass or less. Similarly, the amount of the siloxane compound modified with the alkylene oxide compound in the etching solution of the present invention is preferably 0.03% by mass or more and 0.2% by mass or less, more preferably 0.04% by mass or more and 0.15% by mass or less, and even more preferably 0.05% by mass or more and 0.1% by mass or less. When the siloxane compound modified with the alkylene oxide compound is a combination of two or more, the amount of the siloxane compound modified with the alkylene oxide compound refers to their total amount.

[0038] From the viewpoint of improving the etching rate ratio (SiN / SiO2 selective rate ratio) of silicon nitride film to silicon oxide film, the amount of the siloxane compound modified with the alkylene oxide compound in the etching solution of the present invention is preferably 0.01% by mass or more, more preferably 0.02% by mass or more, and even more preferably 0.03% by mass or more. Furthermore, from the same viewpoint, it is preferably 0.2% by mass or less, more preferably 0.1% by mass or less, even more preferably 0.08% by mass or less, and even more preferably 0.05% by mass or less. Similarly, from the same viewpoint, the amount of the siloxane compound modified with the alkylene oxide compound in the etching solution of the present invention is preferably 0.01% by mass or more and 0.2% by mass or less, more preferably 0.02% by mass or more and 0.1% by mass or less, even more preferably 0.03% by mass or more and 0.08% by mass or less, and even more preferably 0.03% by mass or more and 0.05% by mass or less.

[0039] [Phosphoric acid]

[0040] From the viewpoint of improving the etching rate ratio of silicon nitride film to silicon oxide film (hereinafter also referred to as "SiN / SiO2 selective rate ratio"), the amount of phosphoric acid in the etching solution of the present invention is preferably 50% by mass or more, more preferably 70% by mass or more, and even more preferably 80% by mass or more. Furthermore, from the same viewpoint, it is preferably 95% by mass or less, more preferably 90% by mass or less, and even more preferably 85% by mass or less. From the same viewpoint, the amount of phosphoric acid in the etching solution of the present invention is preferably 50% by mass or more and 95% by mass or less, more preferably 70% by mass or more and 90% by mass or less, and even more preferably 80% by mass or more and 85% by mass or less.

[0041] [water]

[0042] Examples of water contained in the etching solution of the present invention include distilled water, ion-exchanged water, pure water, and ultrapure water. The amount of water in the etching solution of the present invention is preferably 2% by mass or more, more preferably 5% by mass or more, even more preferably 7% by mass or more, and preferably 30% by mass or less, more preferably 25% by mass or less, and even more preferably 20% by mass or less.

[0043] [High-temperature stabilizer]

[0044] In one or more embodiments of the etching solution of the present invention, from the viewpoint of maintaining the SiN / SiO2 selectivity ratio while suppressing filter clogging during repeated use, it may further contain a high-temperature stabilizer or be formulated with a high-temperature stabilizer. Examples of high-temperature stabilizers include at least one selected from sulfonic acid compounds, maleic acid, and oxalic acid. Examples of sulfonic acid compounds include, for instance, p-toluenesulfonic acid and benzenesulfonic acid.

[0045] [Organophosphonic acid compounds]

[0046] In one or more embodiments of the etching solution of the present invention, from the viewpoint of improving the SiN / SiO2 selectivity ratio and / or further suppressing silicon dioxide precipitation and adhesion to the SiO2 film, it may further contain an organophosphonic acid compound or a combination thereof. Examples of organophosphonic acid compounds that, from the viewpoint of improving the SiN / SiO2 selectivity ratio and suppressing silicon dioxide precipitation and adhesion to the SiO2 film, include, for example, phosphoric acid polymers such as polyvinylphosphonic acid (PVPA), alkylphosphonic acids, alkenylphosphonic acids, and alkyl ether phosphonic acids.

[0047] [Nonionic surfactants]

[0048] In one or more embodiments of the etching solution of the present invention, from the viewpoint of further suppressing the precipitation and adhesion of silica to the SiO2 film, it may further contain a nonionic surfactant or be formulated with a combination of nonionic surfactants. As a nonionic surfactant, from the viewpoint of suppressing the precipitation and adhesion of silica to the SiO2 film, examples include polyoxyalkylene ethers, such as at least one selected from polyoxyethylene lauryl ether, polyoxyethylene oil ether, and polyoxyethylene polyoxypropylene lauryl myristate ether.

[0049] [Other ingredients]

[0050] The etching solution of the present invention may contain other components or be formulated with other components without compromising the effects of the present invention. Examples of other components include acids other than phosphoric acid, chelating agents, surfactants other than the nonionic surfactants mentioned above, solubilizers, preservatives, rust inhibitors, bactericides, antibacterial agents, antioxidants, etc.

[0051] [Etching solution manufacturing method]

[0052] In one aspect, the present invention relates to a method for manufacturing an etching solution (hereinafter also referred to as "the etching solution manufacturing method of the present invention"), which includes a step of combining the above-mentioned siloxane compound modified with a compound having an alkylene oxide, phosphoric acid, water, and the above-mentioned optional components as needed (hereinafter also referred to as "combining step").

[0053] In this invention, "combination" includes simultaneously or sequentially mixing the siloxane compound modified with a compound having an alkylene oxide group, phosphoric acid, water, and any other optional components as needed. The order of mixing is not particularly limited. The above-mentioned combination can be performed, for example, using a homogenizer, homogenizer, ultrasonic disperser, or wet ball mill.

[0054] From the viewpoint of improving the SiN / SiO2 selectivity ratio, the pH value of the etching solution of the present invention is preferably 0.1 or higher, more preferably 0.2 or higher, even more preferably 0.3 or higher, and preferably 2 or lower, more preferably 1.5 or lower, and even more preferably 1 or lower. Similarly, from the viewpoint of the present invention, the pH value of the etching solution is preferably 0.1 or higher and 2 or lower, more preferably 0.2 or higher and 1.5 or lower, and even more preferably 0.3 or higher and 1 or lower. In the present invention, the pH value 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, it can be measured using the method described in the examples.

[0055] The etching solution of the present invention is used in one or more embodiments for etching at a temperature of 110°C or higher and 250°C or lower.

[0056] The etching solution of the present invention can be stored and supplied in a concentrated state without compromising its stability. This is preferable in terms of reducing manufacturing and transportation costs. Furthermore, the concentrated solution can be appropriately diluted with water, an aqueous phosphoric acid solution, or the like for use in the etching process. A dilution ratio of 5 to 100 times is preferred.

[0057] [Set]

[0058] In one embodiment, the present invention relates to a kit for manufacturing the etching solution of the present invention (hereinafter also referred to as "the kit of the present invention").

[0059] As a kit of the present invention, examples include a kit containing a solution (first solution) of a siloxane compound modified with an alkylene oxide compound and a solution containing phosphoric acid (second solution) in an immiscible state, which are mixed during use (a two-solution etching solution). After the first solution and the second solution are mixed, they can be diluted with water or an aqueous solution of phosphoric acid as needed. The first solution or the second solution may contain all or part of the water used to prepare the etching solution. The phosphoric acid contained in the second solution may be all or part of the phosphoric acid used to prepare the etching solution. The first solution and the second solution may each contain the optional components described above as needed.

[0060] According to the kit of the present invention, an etching solution can be obtained that can suppress the precipitation of silicon dioxide generated in the etching process and adhere to the SiO2 film.

[0061] [Substrate to be processed]

[0062] In one or more embodiments, the substrate to be etched using the etching solution of the present invention is a substrate having a silicon nitride film and a silicon oxide film. In one or more embodiments, the substrate having the silicon nitride film and silicon oxide film may be a substrate with a three-dimensional structure consisting of alternating layers of multiple silicon nitride films and multiple silicon oxide films. Examples of substrates include semiconductor substrates and flat panel display substrates. Examples of silicon nitride films include those formed using low-pressure chemical vapor deposition (LPCVD), plasma-assisted chemical vapor deposition (PECVD), and atomic layer deposition (ALD). Examples of silicon oxide films include those formed using thermal oxidation, LPCVD, PECVD, and ALD.

[0063] In one or more embodiments, the etching solution of the present invention can be suitably used to manufacture three-dimensional semiconductor devices such as 3D NAND flash memory. For example, in one or more embodiments, the etching solution of the present invention can be used to etch a substrate having a three-dimensional structure formed by alternating layers of multiple silicon nitride films and multiple silicon oxide films.

[0064] [Etching Method]

[0065] In one aspect, the present invention relates to an etching method (hereinafter also referred to as "the etching method of the present invention"), which includes a step of removing a silicon nitride film from a substrate having a silicon nitride film and a silicon oxide film using the etching solution of the present invention (hereinafter also referred to as "the etching step").

[0066] By using the etching method of the present invention, the precipitation and adhesion of silicon dioxide generated during the etching process to the SiO2 film can be suppressed, thereby improving the productivity of the semiconductor substrate and enhancing its quality. The etching method and conditions in the above-described etching process are the same as those in the etching process of the semiconductor substrate manufacturing method of the present invention, which will be described later.

[0067] [Semiconductor substrate manufacturing method]

[0068] In one aspect, the present invention relates to a method for manufacturing a semiconductor substrate (hereinafter also referred to as "the semiconductor substrate manufacturing method of the present invention"), which includes a step (etching step) of removing a silicon nitride film from a substrate having a silicon nitride film and a silicon oxide film using an etching solution of the present invention, wherein the substrate is a substrate for semiconductors.

[0069] According to the semiconductor substrate manufacturing method of the present invention, the precipitation and adhesion of silicon dioxide generated in the etching process to the SiO2 film can be suppressed, thereby achieving the effect of efficiently manufacturing semiconductor substrates with improved quality.

[0070] In the above etching process, examples of etching methods include immersion etching and single-piece etching.

[0071] In the above etching process, from the viewpoint of improving the SiN / SiO2 selectivity ratio, the etching temperature of the etchant is preferably 110°C or higher, more preferably 120°C or higher, even more preferably 140°C or higher, even more preferably 150°C or higher, and preferably 250°C or lower, more preferably 230°C or lower, even more preferably 200°C or lower, and even more preferably 180°C or lower. Similarly, from the same viewpoint, the etching temperature of the etchant is preferably 110°C or higher and 250°C or lower, more preferably 120°C or higher and 230°C or lower, even more preferably 140°C or higher and 200°C or lower, and even more preferably 150°C or higher and 180°C or lower.

[0072] In the above etching process, the etching time can preferably be set to 30 minutes or more, more preferably 60 minutes or more, and preferably 270 minutes or less, more preferably 180 minutes or less.

[0073] In the above etching process, from the viewpoint of improving productivity, the etching rate of the silicon nitride film is preferably [missing information]. / minute or more, preferably / minute or more, further optimized / minute or more.

[0074] In the above etching process, from the viewpoint of improving productivity, the etching rate of the silicon oxide film is preferably [missing information]. Below / minute, preferably Below / minute, further preferred / minute or less.

[0075] In the above etching process, from the viewpoint of improving productivity, the SiN / SiO2 selection rate ratio is preferably 150 or more, more preferably 200 or more, and even more preferably 300 or more.

[0076] Example

[0077] The present invention is illustrated in detail below by way of examples, but the present invention is not limited to these examples.

[0078] 1. Preparation of etching solution (Examples 1 to 7 and Comparative Examples 1 to 4)

[0079] The etching solutions (pH 0.45) of Examples 1 to 7 and Comparative Examples 1 to 4 were obtained by combining the siloxane compound or additive represented by formula (II) shown in Table 1, an aqueous solution of phosphoric acid, and water as needed. The amounts (mass%, active ingredient) of the siloxane compound or additive, phosphoric acid, and water in each etching solution are shown in Table 1.

[0080] The following components are used in the preparation of the etching solution.

[0081] (The siloxane compound represented by formula (II))

[0082] PEG-7 polydimethylsiloxane phosphate [“PS-100” manufactured by Phoenix Chemical, HLB: 14.6]

[0083] PEG-3 polydimethylsiloxane [Shin-Etsu Chemical Co., Ltd. "KF-6015", HLB: 4.5]

[0084] PEG-10 polydimethylsiloxane [Shin-Etsu Chemical Co., Ltd. "KF-6017", HLB: 4.5]

[0085] PEG-10 polydimethylsiloxane [Shin-Etsu Chemical Co., Ltd. "KF-6043", HLB: 14]

[0086] Trisiloxane ethoxide [SILWET L-77 manufactured by Biomedical Science, HLB: 5.4]

[0087] (additive)

[0088] PVPA (polyvinylphosphonic acid) [Maruzen Petrochemical Co., Ltd.]

[0089] 3-[[3-aminopropyl(dimethyl)silyl]oxy-dimethylsilyl]propane-1-amine [Manufactured by Fujifilm and Kagaku Pure Chemicals Co., Ltd.]

[0090] Dimethyldimethoxysilane [manufactured by Tokyo Chemical Industry Co., Ltd.]

[0091] (Phosphoric acid)

[0092] Phosphoric acid aqueous solution [85% phosphoric acid concentration, manufactured by Phosphoric Chemical Industry Company]

[0093] 2. Measurement methods for each parameter

[0094] [pH value of the etching solution]

[0095] The pH value of the etching solution at 25°C is measured using a pH meter (manufactured by Toa DKK Corporation), and is the value after immersing the electrode of the pH meter in the etching solution for 1 minute.

[0096] [The method for calculating r, s, and t of siloxane compounds represented by formula (II)]

[0097] The modification rate and the number of moles of EO addition r were calculated using H-NMR (nuclear magnetic resonance device), and the average molecular weight was determined by size exclusion chromatography (SEC). Based on these values, s and t were calculated.

[0098] <Conditions for H-NMR>

[0099] Device: JNM-ESC400 (manufactured by Nippon Electronics Corporation)

[0100] Total number of times: 8

[0101] Relaxation time: 30s

[0102] Pulse angle: 45°

[0103] <SEC Conditions>

[0104] Column: K-806L+K-806L (manufactured by Showa Denko Co., Ltd.)

[0105] Elution buffer: 1 mmol / L Farmin DM20 / CHCl3

[0106] Flow rate: 1.0 mL / min

[0107] Column temperature: 40℃

[0108] Detector: RI

[0109] Injection volume: 100μL

[0110] Molecular weight standard: Polystyrene

[0111] 3. Evaluation of Etching Solution

[0112] [Etching speed and selectable speed ratio]

[0113] Colloidal silica (PL-1, manufactured by Fuso Chemical Industry Co., Ltd.) was added to the etching solutions prepared in each composition (Examples 1 to 7 and Comparative Examples 1 to 4) at a Si concentration of 200 ppm. A 1 cm × 1 cm silicon nitride wafer with a pre-measured thickness of the silicon nitride film (SiN film) was impregnated in the solution and etched at 160°C to 170°C for 90 minutes. After cooling and rinsing with water, the thickness of the silicon nitride film was measured again, and the difference was taken as the etching amount. The film thickness was measured using an optical interferometry film thickness measuring device (SCREEN, "Random Ace VM-100").

[0114] In addition, using 1.5cm×1cm LP-TEOS as a silicon oxide film (SiO2 film), the etching amount of the silicon oxide film was determined under the same conditions as that of the silicon nitride film.

[0115] Then, the etching rate of the silicon nitride film, the etching rate of the silicon oxide film, and the selectivity ratio were calculated using the following formulas. The calculation results are shown in Table 1. Furthermore, the effect of suppressing silicon dioxide precipitation and adhesion to the silicon oxide film can be evaluated based on the etching rate value of the silicon oxide film. If the etching rate value of the silicon oxide film is negative, it can be determined that silicon dioxide is precipitating and adhering to the silicon oxide film. The closer the values ​​are to the desired value... If the value is measured in seconds per minute, it can be determined that the effect of inhibiting silica precipitation on the silica film is better.

[0116]

[0117]

[0118] Select speed ratio = silicon nitride film etching speed / silicon oxide film etching speed

[0119] [Table 1]

[0120]

[0121] As shown in Table 1, the etching solutions of Examples 1 to 7 containing the siloxane compound represented by Formula (II) suppressed the precipitation of silicon dioxide and its adhesion to the SiO2 film compared with those of Comparative Examples 1 to 4 which did not contain the siloxane compound represented by Formula (II). Furthermore, the SiN / SiO2 selectivity ratio was improved.

[0122] Industrial availability

[0123] The etching solution of the present invention can be used in the manufacturing method of semiconductor substrates for high density or high integration.

Claims

1. An etching solution for use in a process of removing a silicon nitride film from a substrate having a silicon nitride film and a silicon oxide film. The etching solution contains a siloxane compound modified with a compound having an alkylene oxide group, phosphoric acid, and water. The amount of the siloxane compound modified with an alkylene oxide in the etching solution is 0.03% by mass or more and 0.2% by mass or less. The amount of phosphoric acid in the etching solution is 50% by mass or more. The siloxane compound modified by a compound having an alkylene oxide group is a siloxane compound represented by the following formula (II): In the formula (II), R is an alkyl group with 1 or more carbon atoms and 5 or less, a hydroxyalkyl group with 1 or more carbon atoms and 5 or less, or an anionic group; t / (s+t)×100 is 4 or more, and r is 1 or more and 30 or less.

2. The etching solution according to claim 1, wherein it is prepared in combination with a siloxane compound modified with a compound having an alkylene oxide, phosphoric acid, and water.

3. The etching solution according to claim 1 or 2, wherein, The amount of the siloxane compound modified with a compound having an alkylene oxide in the etching solution is 0.03% by mass or more and 0.1% by mass or less.

4. The etching solution according to claim 1 or 2, wherein, The amount of phosphoric acid in the etching solution is more than 50% by mass and less than 95% by mass.

5. The etching solution according to claim 1 or 2, wherein, The amount of phosphoric acid in the etching solution is above 80% by mass and below 85% by mass.

6. The etching solution according to claim 1 or 2, wherein, In the formula (II), t / (s+t)×100 is greater than 10 and less than 80.

7. The etching solution according to claim 1 or 2, wherein, In the formula (II), t / (s+t)×100 is greater than 20 and less than 60.

8. The etching solution according to claim 1 or 2, wherein, In formula (II), R is a methyl group or a phosphate group.

9. The etching solution according to claim 1 or 2, wherein, In formula (II), R is a phosphate group.

10. The etching solution according to claim 1 or 2, wherein, The pH value of the etching solution is below 2.

11. The etching solution according to claim 1 or 2, used for etching at an etching temperature of 110°C or higher and 250°C or lower.

12. An etching solution for a process of removing a silicon nitride film from a substrate having a silicon nitride film and a silicon oxide film. The etching solution contains a siloxane compound modified with a compound having an alkylene oxide group, phosphoric acid, and water. The amount of the siloxane compound modified with an alkylene oxide in the etching solution is 0.03% by mass or more and 0.2% by mass or less. The amount of phosphoric acid in the etching solution is 50% by mass or more. The siloxane compound modified by the compound having an alkylene oxide group is a siloxane compound having the structure represented by the following formula (II): In formula (II), R is a phosphate group; t / (s+t)×100 is 10 or more and 80 or less, and r is 1 or more and 30 or less.

13. An etching method comprising the step of removing a silicon nitride film from a substrate having a silicon nitride film and a silicon oxide film using an etching solution according to any one of claims 1 to 12.

14. A method for manufacturing a semiconductor substrate, comprising the step of removing a silicon nitride film from a substrate having a silicon nitride film and a silicon oxide film using an etching solution according to any one of claims 1 to 12, and The substrate is a substrate used for semiconductors.

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