Etchant

Abstract

To provide etchant capable of suppressing etching of polysilicon film while maintaining etching speed of silicon nitride film in one aspect.SOLUTION: The present disclosure, in one aspect, relates to an etchant for the process of removing a silicon nitride film from a substrate having a silicon nitride film, a silicon oxide film, and a polysilicon film, and containing a compound having a diketone moiety, phosphoric acid, and water.SELECTED DRAWING: None

Description

[Technical field]

[0001] The present disclosure relates to an etching solution for silicon nitride films, an etching method using the same, and a method for manufacturing a semiconductor substrate. [Background technology]

[0002] In the manufacturing process of semiconductor devices, silicon nitride film (hereinafter also referred to as "SiN film") and silicon oxide film (hereinafter referred to as "SiO 2 In the present invention, a process is performed in which the SiN film is selectively etched and removed from a substrate having a SiN film (also referred to as a "SiN film"). Conventionally, a method of etching a SiN film using phosphoric acid at a high temperature of 150° C. or higher is known.

[0003] In recent years, the semiconductor industry has become highly integrated, and there is a demand for more complex and finer wiring. 2 Methods for increasing the ratio of the etching rate of the SiN film to the etching rate of the silicon nitride film have been proposed (for example, Patent Documents 1 and 2).

[0004] Patent Document 1 proposes an etching chemical composition containing water, phosphoric acid, and a colloidal silica growth inhibitor having at least one -COOH group. Patent Document 2 proposes a composition for etching silicon nitride films, which contains phosphoric acid, a composite silane consisting of two or three silane compounds, and water. The document also discloses that the composition may further contain a carboxylic acid compound such as malonic acid or oxalic acid. Patent Document 3 proposes an etching solution composition containing at least one selected from a hydroxyl group-containing organic compound, a carbonyl group-containing organic compound, an inorganic acid, and an inorganic acid salt, hydrofluoric acid, ammonium fluoride, and an organic acid. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Special Publication No. 2019-511842 [Patent Document 2] JP 2018-182312 A [Patent Document 3] JP 2013-51371 A Summary of the Invention [Problem to be solved by the invention]

[0006] In recent years, the semiconductor industry has become highly integrated, and wiring is required to become more complex and finer, which has led to a demand for more efficient removal of silicon nitride films (SiN films). In particular, in the manufacturing process of three-dimensional semiconductor devices such as three-dimensional NAND-type flash memories, there is a demand for further improvement in the etching speed of SiN films from the viewpoints of productivity and yield. Furthermore, the etching speed of silicon nitride films (SiN films) and silicon oxide films (SiO 2 When a SiN film is selectively etched and removed from a substrate having a polysilicon film (hereinafter also referred to as a "Poly-Si film"), a SiO 2 It is necessary to suppress not only the etching of the film but also the etching of the Poly-Si film.

[0007] In view of this, the present disclosure provides an etching solution capable of suppressing etching of a polysilicon film while maintaining the etching rate of a silicon nitride film, an etching method using the same, and a method for manufacturing a semiconductor substrate. [Means for solving the problem]

[0008] In one aspect, the present disclosure relates to an etching solution for a process of removing a silicon nitride film from a substrate having a silicon nitride film, a silicon oxide film, and a polysilicon film, the etching solution comprising a compound having a diketone moiety, phosphoric acid, and water.

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

[0010] In one aspect, the present disclosure relates to a method for manufacturing a semiconductor substrate, the method including a step of removing a silicon nitride film from a substrate having a silicon nitride film, a silicon oxide film, and a polysilicon film, using an etching solution of the present disclosure, the substrate being a substrate for use in semiconductors. Effect of the Invention

[0011] According to one aspect of the present disclosure, it is possible to provide an etching solution capable of suppressing etching of a polysilicon film while maintaining an etching rate of a silicon nitride film. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] In one or more embodiments, the present disclosure relates to an etching solution for a process of removing a silicon nitride film from a substrate having a silicon nitride film, a silicon oxide film, and a polysilicon film, the etching solution containing a compound having a diketone moiety, phosphoric acid, and water (hereinafter, also referred to as the "etching solution of the present disclosure"). The etching solution of the present disclosure can suppress etching of a polysilicon film while maintaining the etching rate of a silicon nitride film.

[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. It is presumed that the diketone moiety of the compound having a diketone moiety bonds and coordinates with polysilicon, thereby protecting the polysilicon film and suppressing the etching of the silicon nitride film. However, the present disclosure need not be construed as being limited to these mechanisms.

[0014] In one or more embodiments, the etching solution of the present disclosure can be prepared by blending a compound having a diketone moiety, phosphoric acid, water, and, if necessary, any optional components. That is, in one or more embodiments, the etching solution of the present disclosure is prepared by blending a compound having a diketone moiety, phosphoric acid, and water. In the present disclosure, "blended" means that not only the compound having a diketone moiety, phosphoric acid, and water, but also any other component can be blended as necessary. In addition, in the present disclosure, the blending amount of each component in the etching solution can be interpreted as the content in the etching solution.

[0015] [Compounds containing diketone moieties] In one or more embodiments, the etching solution of the present disclosure contains a compound having a diketone moiety. In one or more embodiments, the etching solution of the present disclosure contains a compound having a diketone moiety. The compound having a diketone moiety may be used alone or in combination of two or more kinds.

[0016] The compound having a diketone moiety has at least one diketone moiety, and may have a plurality of diketone moieties. In one or more embodiments, the diketone moiety is preferably a structure in which two ketone groups (-CO-) are adjacent to each other (-CO-CO- group) or a structure in which two ketone groups are bonded via one carbon atom (-CO-C-CO- group) from the viewpoint of suppressing etching of a polysilicon film while maintaining the etching rate of a silicon nitride film. In one or more embodiments of the present disclosure, the -CO-C-CO- group is preferably -CO-CH 2 Includes -CO- and -CO-CHR-CO- (wherein R represents an alkyl group having 1 to 24 carbon atoms, an alkenyl group having 1 to 24 carbon atoms, or an aromatic group).

[0017] From the viewpoint of suppressing etching of a polysilicon film while maintaining the etching rate of a silicon nitride film, the compound having a diketone moiety is preferably at least one selected from a compound having a structure in which two ketone groups are adjacent to each other and a compound having a structure in which two ketone groups are bonded via one carbon atom. For example, the compound having a diketone moiety is at least one selected from a dicarboxylic acid having a structure in which two carboxy groups are adjacent to each other or a structure in which two carboxy groups are bonded via one carbon atom, an α-diketone compound (1,2-diketone), a β-diketone compound (1,3-diketone), and derivatives thereof. Examples of dicarboxylic acids having a structure in which two carboxy groups are adjacent to each other or are bonded via one carbon atom include oxalic acid, malonic acid, and phenylmalonic acid. Examples of α-diketone compounds (1,2-diketones) include 1,2-cyclohexanedione. An example of the β-diketone compound (1,3-diketone) is acetylacetone.

[0018] The amount of the compound having a diketone moiety in the etching solution of the present disclosure 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 from the viewpoint of suppressing etching of the Poly-Si film, and is preferably 0.5% by mass or less, more preferably 0.3% by mass or less, more preferably 0.2% by mass or less, even more preferably 0.1% by mass or less, and even more preferably less than 0.1% by mass from the viewpoint of suppressing etching of the Poly-Si film. From the same viewpoint, the amount of the compound having a diketone moiety in the etching solution of the present disclosure is preferably 0.01% by mass or more and 0.5% by mass or less, more preferably 0.01% by mass or more and 0.3% by mass or less, more preferably 0.02% by mass or more and 0.2% by mass or less, even more preferably 0.03% by mass or more and 0.1% by mass or less, and even more preferably 0.03% by mass or more and 0.1% by mass or less. When two or more kinds of the compound having a diketone moiety are combined, the blending amount of the compound having a diketone moiety refers to the total blending amount of the compounds.

[0019] [phosphoric acid] The amount of phosphoric acid blended in the etching solution of the present disclosure is determined from the viewpoint of suppressing etching of a polysilicon film while maintaining the etching rate of a silicon nitride film, and from the viewpoint of the ratio of the etching rate of a silicon nitride film to that of a silicon oxide film (hereinafter referred to as "SiN / SiO 2 From the viewpoint of improving the selectivity ratio (also referred to as "selectivity rate ratio"), the content is preferably 50 mass% or more, more preferably 70 mass% or more, and even more preferably 80 mass% or more, and from the same viewpoint, the content is preferably 95 mass% or less, more preferably 90 mass% or less, and even more preferably 85 mass% or less. From the same viewpoint, the content of phosphoric acid in the etching solution of the present disclosure is preferably 50 mass% or more and 95 mass% or less, more preferably 70 mass% or more and 90 mass% or less, and even more preferably 80 mass% or more and 85 mass% or less.

[0020] [water] Examples of water contained in the etching solution of the present disclosure include distilled water, ion-exchanged water, pure water, and ultrapure water. The amount of water in the etching solution of the present disclosure is preferably 2% by mass or more, more preferably 5% by mass or more, and even more preferably 7% by mass or more, from the viewpoint of suppressing etching of the polysilicon film while maintaining the etching rate of the silicon nitride film, and from the same viewpoint, it is preferably 30% by mass or less, more preferably 25% by mass or less, and even more preferably 20% by mass or less. From the same viewpoint, the amount of water in the etching solution of the present disclosure is preferably 2% by mass or more and 30% by mass or less, more preferably 5% by mass or more and 25% by mass or less, and even more preferably 7% by mass or more and 20% by mass or less.

[0021] [Siloxane compound modified with a compound having an alkyleneoxy group] In one or more embodiments, the etching solution of the present disclosure has a feature of suppressing etching of a polysilicon film while maintaining an etching rate of a silicon nitride film, and / or a feature of suppressing etching of a polysilicon film by reducing the amount of silica such as SiO 2From the viewpoint of suppressing deposition and adhesion to the film, the composition may further contain or be blended with a siloxane compound modified with a compound having an alkyleneoxy group. The siloxane compound modified with a compound having an alkyleneoxy group may be used alone or in combination of two or more kinds, but from the viewpoint of suppressing etching of the polysilicon film while maintaining the etching rate of the silicon nitride film, it is preferable to use one kind alone. The alkyleneoxy group may be, for example, at least one selected from an ethyleneoxy group (EO) and a propyleneoxy group (PO), and the SiO of silica may be used. 2 From the viewpoint of suppressing deposition and adhesion to the film, EO is preferred.

[0022] The siloxane compound modified with a compound having an alkyleneoxy group in the present disclosure is SiO 2 From the viewpoint of suppressing deposition and adhesion to the film, a siloxane compound having a structure represented by the following formula (I) is preferable, and a siloxane compound represented by the following formula (II) is more preferable.

[0023] [ka] In the formula (I), R is an alkyl group having 1 to 5 carbon atoms, a hydroxyalkyl group having 1 to 5 carbon atoms, an alkoxy group having 1 to 5 carbon atoms, or an anionic group. t is 1 to 50, and r is 1 to 30.

[0024] [ka] In the formula (II), R is an alkyl group having 1 to 5 carbon atoms, a hydroxyalkyl group having 1 to 5 carbon atoms, an alkoxy group having 1 to 5 carbon atoms, or an anionic group. t / (s+t)×100 is 4 or more, and r is 1 or more and 30 or less.

[0025] In the formula (I) and formula (II), examples of the anionic group include a phosphonic acid group, a sulfate group, a carboxylic acid group, and a phosphoric acid group (-O-PO-(OH)2 ) are mentioned. In the formula (I) and the formula (II), R is SiO 2 From the viewpoint of suppressing deposition and adhesion to the film, an alkyl group having 1 to 5 carbon atoms, an alkoxy group having 1 to 5 carbon atoms, or an anionic group is preferable, a methyl group, a methoxy group, or a phosphate group is more preferable, and a phosphate group is even more preferable. In the formula (II), t / (s+t)×100 is the SiO 2 From the viewpoint of suppressing deposition and adhesion to the film, it 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, and even more preferably 60 or less. From the same viewpoint, t / (s+t)×100 is preferably 4 or more and 100 or less, and more preferably 7 or more and 100 or less. In the formulae (I) and (II), t is preferably 1 or more and 50 or less, and more preferably 1 or more and 30 or less, from the same viewpoint. In the formulae (I) and (II), r is 1 or more and 30 or less, and from the same viewpoint, r is preferably 1 or more and 25 or less, and more preferably 3 or more and 20 or less. In the present disclosure, r, s, and t can be calculated, for example, by calculating the modification rate and the number of moles of EO added r by H-NMR (nuclear magnetic resonance apparatus) and measuring the average molecular weight by size exclusion chromatography (SEC), and then calculating s and t from these values.

[0026] The HLB of the siloxane compound modified with the compound having an alkyleneoxy group is SiO 2 From the viewpoint of suppressing deposition and adhesion to the membrane, the HLB value is preferably 4 or more, more preferably 5 or more, and even more preferably 10 or more. Here, the HLB value is a value defined as "7 + sum of the number of hydrophilic group groups - sum of the number of lipophilic group groups" using the number of groups determined by the functional group described in Davis, JT; Proc. Intern. Congr. Surface Activity, 2nd, London, 1, 426 (1957).

[0027] Examples of the siloxane compound modified with a compound having an alkyleneoxy group include at least one selected from PEG-7 dimethicone phosphate (HLB: 14.6), PEG-3 dimethicone (HLB: 4.5), PEG-10 dimethicone (HLB: 4.5 or 14), and trisiloxane ethoxylate (HLB: 5.4).

[0028] The amount of the siloxane compound modified with the compound having an alkyleneoxy group in the etching solution of the present disclosure is SiO 2 From the viewpoint of suppressing deposition and adhesion to the film, the amount is preferably 0.03 mass% or more, more preferably 0.04 mass% or more, and even more preferably 0.05 mass% or more, and from the same viewpoint, the amount is preferably 0.2 mass% or less, more preferably 0.15 mass% or less, and even more preferably 0.1 mass% or less. From the same viewpoint, the amount of the siloxane compound modified with the compound having an alkyleneoxy group in the etching solution of the present disclosure is preferably 0.03 mass% or more and 0.2 mass% or less, more preferably 0.04 mass% or more and 0.15 mass% or less, and even more preferably 0.05 mass% or more and 0.1 mass% or less. When the siloxane compound modified with the compound having an alkyleneoxy group is a combination of two or more kinds, the amount of the siloxane compound modified with the compound having an alkyleneoxy group refers to the total amount of them.

[0029] [High temperature stabilizer] In one or more embodiments, the etching solution of the present disclosure is a SiN / SiO 2 From the viewpoint of suppressing clogging of the filter during circulating use while maintaining the selective velocity ratio, the high-temperature stabilizer may be further contained or blended. The high-temperature stabilizer may be at least one selected from sulfonic acid compounds, maleic acid, and oxalic acid. Examples of the sulfonic acid compounds include paratoluenesulfonic acid and benzenesulfonic acid.

[0030] [Organophosphonic acid compounds] In one or more embodiments, the etching solution of the present disclosure is a SiN / SiO 2 From the viewpoint of improving the selectivity ratio, and / or SiO 2 From the viewpoint of further suppressing deposition and adhesion to the film, an organic phosphonic acid compound may be further contained or blended. The organic phosphonic acid compound is SiN / SiO 2 Improved selectivity ratio and SiO 2 From the viewpoint of suppressing deposition and adhesion to the film, examples of the material include phosphoric acid polymers such as polyvinyl phosphonic acid (PVPA), alkyl phosphonic acids, alkenyl phosphonic acids, and alkyl ether phosphonic acids.

[0031] [Nonionic surfactants] In one or more embodiments, the etching solution of the present disclosure is a silica SiO 2 From the viewpoint of further suppressing deposition and adhesion to the film, a nonionic surfactant may be further contained or blended. As the nonionic surfactant, SiO 2 From the viewpoint of suppressing deposition and adhesion to the film, polyoxyalkylene alkyl ethers are used, and examples thereof include at least one selected from polyoxyethylene lauryl ether, polyoxyethylene oleyl ether, and polyoxyethylene polyoxypropylene lauryl myristyl ether.

[0032] [Other ingredients] The etching solution of the present disclosure may further contain or be blended with other components within the scope of not impairing the effects of the present disclosure. Examples of other components include acids other than phosphoric acid, chelating agents, surfactants other than the above-mentioned nonionic surfactants, solubilizers, preservatives, rust inhibitors, bactericides, antibacterial agents, antioxidants, etc.

[0033] In one or more embodiments, the etching solution of the present disclosure preferably does not contain hydrofluoric acid. For example, the amount of hydrofluoric acid in the etching solution of the present disclosure is preferably less than 0.5 mass%, more preferably 0.1 mass% or less, and even more preferably 0 mass% (i.e., not contained). In one or more embodiments, the etching solution of the present disclosure preferably does not contain ammonium fluoride. For example, the amount of ammonium fluoride in the etching solution of the present disclosure is preferably less than 5 mass%, more preferably 1 mass% or less, even more preferably 0.1 mass% or less, and even more preferably 0 mass% (i.e., not contained).

[0034] [Method of manufacturing the etching solution] In one aspect, the present disclosure relates to a method for producing an etching solution (hereinafter also referred to as the "etching solution producing method of the present disclosure"), which includes a step of blending (hereinafter also referred to as the "blending step") the compound having the diketone moiety, phosphoric acid, water, and, as necessary, the optional components described above. In the present disclosure, "blending" includes simultaneously or sequentially mixing the compound having a diketone moiety, phosphoric acid, water, and the optional components described above as necessary. The order of mixing is not particularly limited. The blending can be performed using a mixer such as a homomixer, a homogenizer, an ultrasonic disperser, or a wet ball mill.

[0035] The pH of the etching solution of the present disclosure is determined from the viewpoint of suppressing etching of the polysilicon film while maintaining the etching rate of the silicon nitride film, and from the viewpoint of suppressing etching of the SiN / SiO 2From the viewpoint of improving the selectivity ratio, the pH is preferably 0.1 or more, more preferably 0.2 or more, even more preferably 0.3 or more, and preferably 2 or less, more preferably 1.5 or less, and even more preferably 1 or less. From the same viewpoint, the pH of the etching solution of the present disclosure is preferably 0.1 or more and 2 or less, more preferably 0.2 or more and 1.5 or less, and even more preferably 0.3 or more and 1 or less. In the present disclosure, the pH of the etching solution is the value of the etching solution at 25°C during use, and can be measured using a pH meter, specifically, can be measured by the method described in the Examples.

[0036] In one or more embodiments, the etching solution of the present disclosure is intended to be used for etching at an etching temperature of 110° C. or higher and 250° C. or lower.

[0037] The etching solution of the present disclosure may be stored and supplied in a concentrated state to the extent that its stability is not impaired. In this case, it is preferable in that the manufacturing and transportation costs can be reduced. The concentrated solution can be appropriately diluted with water, an aqueous phosphoric acid solution, or the like as necessary and used in the etching process. The dilution ratio is preferably 5 to 100 times.

[0038] [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"). The kit of the present disclosure may be, for example, a kit (two-liquid etching solution) that contains a solution (first liquid) containing a compound having a diketone moiety and a solution (second liquid) containing phosphoric acid 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 aqueous phosphoric acid solution as necessary. The first liquid or the second liquid may contain all or a part of the water used to prepare the etching solution. The phosphoric acid contained in the second liquid may be all or a part of the phosphoric acid used to prepare the etching solution. The first liquid and the second liquid may each contain the above-mentioned optional components as necessary. According to the kit of the present disclosure, it is possible to obtain an etching solution that can suppress etching of a polysilicon film while maintaining the etching rate of a silicon nitride film.

[0039] [Substrate to be processed] In one or more embodiments, the substrate to be etched using the etching solution of the present disclosure is a substrate having a silicon nitride film, a silicon oxide film, and a polysilicon film. In one or more embodiments, the substrate having a silicon nitride film, a silicon oxide film, and a polysilicon film may have a three-dimensional structure in which a plurality of silicon nitride films and a plurality of silicon oxide films are alternately stacked, and further have a polysilicon film. For example, the polysilicon film may be formed by opening a hole in a substrate in which a plurality of silicon nitride films and a plurality of silicon oxide films are alternately stacked, and pouring Poly-Si into the hole. Examples of the substrate include substrates for use in semiconductors and substrates for use in flat panel displays. Examples of the silicon nitride film include nitride films formed by low pressure chemical vapor deposition (LPCVD), plasma enhanced chemical vapor deposition (PECVD), atomic layer deposition (ALD), and the like. The silicon oxide film may be, for example, an oxide film formed by a thermal oxidation method, an LPCVD method, a PECVD method, an ALD method, or the like. Examples of the polysilicon film include polysilicon films formed by low pressure chemical vapor deposition (LPCVD), plasma enhanced chemical vapor deposition (PECVD), atomic layer deposition (ALD), and the like. In one or more embodiments, the etching solution of the present disclosure can be suitably used for manufacturing a three-dimensional semiconductor device such as a three-dimensional NAND flash memory, etc. For example, in one or more embodiments, the etching solution of the present disclosure can be used for etching a substrate having a three-dimensional structure in which a plurality of silicon nitride films and a plurality of silicon oxide films are alternately stacked.

[0040] [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 removing a silicon nitride film from a substrate having a silicon nitride film, a silicon oxide film, and a polysilicon film by using an 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 suppress the etching of the polysilicon film while maintaining the etching rate of the silicon nitride film, and therefore it is possible to improve the productivity of semiconductor substrates with improved quality. The etching method and conditions in the etching step can be the same as those in the etching step in the semiconductor substrate manufacturing method of the present disclosure described below.

[0041] [Method of manufacturing semiconductor substrate] In one aspect, the present disclosure relates to a method for manufacturing a semiconductor substrate (hereinafter also referred to as the "semiconductor substrate manufacturing method of the present disclosure"), which includes a step of removing a silicon nitride film from a substrate having a silicon nitride film, a silicon oxide film, and a polysilicon film, using an etching solution of the present disclosure (etching step), the substrate being a substrate for use in semiconductors. According to the semiconductor substrate manufacturing method of the present disclosure, it is possible to suppress etching of the polysilicon film while maintaining the etching rate of the silicon nitride film, and therefore it is possible to achieve the effect of efficiently manufacturing semiconductor substrates with improved quality.

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

[0043] In the etching step, the etching temperature of the etching solution is set to a value that satisfies the requirements for maintaining the etching rate of the silicon nitride film while suppressing the etching of the polysilicon film, and for preventing the etching of the SiN / SiO 2From the viewpoint of improving the selectivity ratio, the etching temperature 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. From the same viewpoint, the etching temperature of the etching solution 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.

[0044] In the etching step, the etching time can be set, for example, preferably 30 minutes or more, more preferably 60 minutes or more, and preferably 270 minutes or less, more preferably 180 minutes or less.

[0045] In the etching step, the etching rate of the silicon nitride film is preferably 40 Å / min or more, more preferably 50 Å / min or more, and even more preferably 60 Å / min or more, from the viewpoint of improving productivity.

[0046] In the etching step, the etching rate of the silicon oxide film is preferably 1 Å / min or less, more preferably 0.5 Å / min or less, and even more preferably 0.3 Å / min or less, from the viewpoint of improving quality.

[0047] In the etching step, SiN / SiO 2 From the viewpoint of improving quality, the selection velocity ratio is preferably 150 or more, more preferably 200 or more, and even more preferably 300 or more. EXAMPLES

[0048] The present disclosure will be specifically described below with reference to examples, but the present disclosure is not limited to these examples in any way.

[0049] 1. Preparation of Etching Solution (Preparation of Etching Solutions for Examples 1 to 10 and Comparative Examples 1 to 3) The compounds or additives having a diketone moiety shown in Table 1, an aqueous phosphoric acid solution, and water were mixed to obtain etching solutions (pH: 0.45) of Examples 1 to 10 and Comparative Examples 1 to 3. The amount of each component (mass %, active content) in each etching solution is shown in Table 1. (Preparation of Etching Solutions for Examples 11 to 16 and Comparative Examples 4 to 7) The compound having a diketone moiety shown in Table 2, the siloxane compound or additive shown in Table 2, an aqueous phosphoric acid solution, and water were mixed to obtain etching solutions (pH: 0.45) of Examples 11 to 16 and Comparative Examples 4 to 7. The amount of each component in each etching solution (mass %, active content) is shown in Table 2.

[0050] The following components were used to prepare the etching solution. (Compounds having a diketone moiety) Oxalic acid [Fujifilm Wako Pure Chemical Industries, Ltd.] Malonic acid [Fujifilm Wako Pure Chemical Industries, Ltd.] Acetylacetone [Fujifilm Wako Pure Chemical Industries, Ltd.] Phenylmalonic acid [Fujifilm Wako Pure Chemical Industries, Ltd.] 1,2-Cyclohexanedione [Fujifilm Wako Pure Chemical Industries, Ltd.] (Siloxane compound represented by formula (II)) PEG-7 Dimethicone Phosphate [Phoenix Chemical Company's "PS-100", HLB: 14.6] PEG-10 Dimethicone ["KF-6017" manufactured by Shin-Etsu Chemical Co., Ltd., HLB: 4.5] (Additives) Ethylene glycol [Fujifilm Wako Pure Chemical Industries, Ltd.] Glycolic acid [Fujifilm Wako Pure Chemical Industries, Ltd.] Silicon orthophosphate [Sigma-Aldrich] 3-Aminopropyltriethoxysilane [Sigma-Aldrich] (phosphoric acid) Phosphoric acid aqueous solution [phosphoric acid concentration 85%, manufactured by Rinkagaku Kogyo Co., Ltd.]

[0051] 2. How to measure parameters [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. The modification rate and the number of moles of EO added r were calculated by H-NMR (nuclear magnetic resonance apparatus), and the average molecular weight was measured by size exclusion chromatography (SEC), and s and t were calculated from these values.

[0052] 3. Evaluation of Etching Solutions of Examples 1 to 10 and Comparative Examples 1 to 3 [Silicon nitride film etching rate] A 1 cm×1 cm silicon nitride film wafer, whose silicon nitride film (SiN film) thickness had been measured in advance, was immersed in the etching solution prepared to each composition (Examples 1 to 10 and Comparative Examples 1 to 3) and etched at 165° C. for 90 minutes. After cooling and washing with water, the thickness of the silicon nitride film was measured again, and the difference was taken as the amount of etching. An optical interference film thickness measuring device (SCREEN, "Random Ace VM-100") was used to measure the film thickness. The etching rate of the silicon nitride film was calculated by the following formula. The calculation results are shown in Table 1. Silicon nitride film (SiN film) etching rate (Å / min) = silicon nitride film etching amount (Å) / 90 (min)

[0053] [Polysilicon film etching rate] A 2 cm x 1 cm Poly-Si film substrate, whose polysilicon film (Poly-Si film) thickness had been measured in advance, was immersed in the etching solution (Examples 1 to 10 and Comparative Examples 1 to 3) prepared to each composition. Next, the substrate was immersed in a 0.5% concentration aqueous hydrofluoric acid solution for 120 seconds, and then etched at 165°C for 60 minutes. After that, the substrate was cooled and washed with water, and the thickness of the polysilicon film was measured again, and the difference was taken as the amount of etching. An optical interference type film thickness measuring device (SCREEN, "Random Ace VM-100") was used to measure the film thickness. The etching rate of the polysilicon film was calculated by the following formula. The calculation results are shown in Table 1. Etching rate of polysilicon film (Poly-Si film) (Å / min) = Polysilicon film etching amount (Å) / 60 (min)

[0054] [Table 1]

[0055] As shown in Table 1, the etching solutions of Examples 1 to 8 containing a compound having a diketone moiety were able to suppress the etching of the polysilicon film while maintaining the etching rate of the silicon nitride film, compared to Comparative Examples 1 to 3 which did not contain a compound having a diketone moiety.

[0056] 4. Evaluation of Etching Solutions of Examples 11 to 16 and Comparative Examples 4 to 7 [Silicon nitride and silicon oxide film etching rates] Colloidal silica (PL-1, Fuso Chemical Co., Ltd.) was added to the etching solution prepared for each composition (Examples 11 to 16 and Comparative Examples 4 to 7) so that the Si concentration was 200 ppm, and a 1 cm x 1 cm silicon nitride film wafer whose silicon nitride film (SiN film) thickness had been measured in advance was immersed and etched at 165°C for 90 minutes. After cooling and washing with water, the thickness of the silicon nitride film was measured again, and the difference was taken as the amount of etching. An optical interference film thickness measurement device (SCREEN, "Random Ace VM-100") was used to measure the film thickness. In addition, silicon oxide (SiO 2 The etching amount of the silicon oxide film was calculated by etching LP-TEOS of 1.5 cm x 1 cm under the same conditions as for the silicon nitride film. The etching rate of the silicon nitride film, the etching rate of the silicon oxide film, and the selectivity ratio were calculated by the following formulas. The calculation results are shown in Table 2. Silicon nitride film (SiN film) etching rate (Å / min) = silicon nitride film etching amount (Å) / 90 (min) Silicon oxide film (SiO 2 Etching rate of silicon oxide film (Å / min) = amount of silicon oxide film etched (Å) / 90 (min)

[0057] [Polysilicon film etching rate] Colloidal silica (PL-1, manufactured by Fuso Chemical Co., Ltd.) was added to the etching solution prepared for each composition (Examples 11 to 16 and Comparative Examples 4 to 7) so that the Si concentration was 200 ppm, and a 2 cm x 1 cm Poly-Si film substrate, whose polysilicon film (Poly-Si film) thickness had been measured in advance, was immersed in the solution. Next, the solution was immersed in a 0.5% concentration aqueous hydrofluoric acid solution for 120 seconds, and then etched at 165°C for 60 minutes. After that, the solution was cooled and washed with water, and the thickness of the polysilicon film was measured again, and the difference was taken as the amount of etching. An optical interference film thickness measuring device (SCREEN, "Random Ace VM-100") was used to measure the film thickness. The etching rate of the polysilicon film was calculated by the following formula. The calculation results are shown in Table 2. Etching rate of polysilicon film (Poly-Si film) (Å / min) = Polysilicon film etching amount (Å) / 60 (min)

[0058] [Silica deposition on silicon oxide film] Colloidal silica (PL-1, Fuso Chemical Co., Ltd.) was added to the etching solution prepared for each composition so that the Si concentration was 200 ppm, and a silicon oxide film (SiO 2 A 2cm x 1cm thermal oxide wafer with the thickness of the silicon oxide film measured was immersed in the solution and etched at 165°C for 90 minutes. It was then cooled and washed with water, after which the thickness of the silicon oxide film was measured again, and the difference was taken as the amount of precipitation. An optical interference type film thickness measuring device (SCREEN, "Random Ace VM-100") was used to measure the film thickness. The results are shown in Table 2. Amount of silica precipitation (Å) = (thickness of silicon oxide film after immersion in etching solution) - (thickness of silicon oxide film before immersion in etching solution)

[0059] [Table 2]

[0060] As shown in Table 2, the etching solutions of Examples 11 to 12, which contain a compound having a diketone moiety, and Examples 13 to 16, which contain a compound having a diketone moiety and a siloxane compound represented by formula (II), were able to suppress etching of the polysilicon film while maintaining the etching rate of the silicon nitride film, compared to Comparative Examples 4 to 7, which do not contain a compound having a diketone moiety and / or a siloxane compound represented by formula (II). In addition, Examples 13 to 16, which contain a siloxane compound represented by formula (II), have a higher SiO 2 Deposition and adhesion to the film were suppressed. [Industrial Applicability]

[0061] The etching solution of the present disclosure is useful in a method for manufacturing semiconductor substrates for high density or high integration.

Claims

1. An etching solution for removing a silicon nitride film from a substrate having a silicon nitride film, a silicon oxide film, and a polysilicon film, An etching solution comprising a compound having a diketone moiety, phosphoric acid, and water.

2. The etching solution according to claim 1 , wherein the etching solution is a mixture of a compound having a diketone moiety, phosphoric acid, and water.

3. 2. The etching solution according to claim 1, wherein the compound having a diketone moiety is at least one selected from a compound having a structure in which two ketone groups are adjacent to each other and a compound having a structure in which two ketone groups are bonded via one carbon atom.

4. The etching solution according to claim 1 , wherein the compound having a diketone moiety is blended in an amount of 0.01% by mass or more and 0.5% by mass or less.

5. The etching solution according to claim 1 , further comprising a siloxane compound modified with a compound having an alkyleneoxy group.

6. The etching solution according to claim 1 , wherein the pH of the etching solution is 2 or less.

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

8. 8. An etching method comprising the step of removing a silicon nitride film from a substrate having a silicon nitride film, a silicon oxide film, and a polysilicon film, using the etching solution according to claim 1.

9. a step of removing a silicon nitride film from a substrate having a silicon nitride film, a silicon oxide film, and a polysilicon film by using the etching solution according to any one of claims 1 to 7, The method for manufacturing a semiconductor substrate, wherein the substrate is a substrate for use in a semiconductor.