Etching composition

Abstract

The present invention provides an etching composition having a high etching selectivity of a silicon nitride film to a silicate silicon oxide film as compared with conventional silane-based etching compositions without requiring a silicate and even with a small amount of an additive, and provides a method for manufacturing the same. The etching composition according to the present invention contains phosphoric acid, allyltriethoxysilane, and a solvent. The method for producing the etching composition according the present invention includes heat-treating an aqueous solution containing allyltriethoxysilane and phosphoric acid at 80°C or more and less than 160°C.

Description

Etching composition

[0001] The present disclosure relates to etching compositions, and more particularly to etching compositions suitable for selectively etching silicon nitride films.

[0002] NAND flash memory is made of silicon dioxide (SiO ２ ) film and silicon nitride (Si ３ N ４ NAND flash memories are manufactured by a manufacturing method including an etching process that selectively removes only the silicon nitride film from a substrate on which silicon nitride films such as silicon nitride films and silicon nitride films are alternately stacked. To achieve higher speeds and larger capacities, NAND flash memories are undergoing a transition from planar to 3D circuit structures and are becoming increasingly miniaturized. To fabricate NAND flash memories with finer structures, etching compositions that can more selectively etch away silicon nitride films are required in the etching process. Phosphoric acid-based etching compositions containing a silane compound as an additive are being investigated.

[0003] For example, Patent Document 1 discloses an etching composition for silicon nitride containing a silane coupling agent and water. The etching composition is said to exhibit high selectivity for silicon nitride films, with the etching rate for silicon nitride films being 1000 or more relative to the etching rate for silicon oxide films, due to the inclusion of inorganic silicate. Non-Patent Document 1 also reports a phosphoric acid-based etching composition containing allylmethoxysilane as an additive.

[0004] JP 2020-145343 A

[0005] Applied Surface Science, Vol. 608, 155143 (2023)

[0006] In Patent Document 1, the addition of silicate increases etching selectivity. However, etching compositions containing silicate are contaminated with counter cations, particularly metal counter cations such as sodium, after etching. On the other hand, the etching composition disclosed in Non-Patent Document 1 did not have sufficient selectivity, with an etching selectivity ratio of only about 120 to 280, even when the additive content was a relatively high 0.1 M (0.95 mass%).

[0007] An object of the present disclosure is to provide at least one of an etching composition that does not require silicate and that has a high etching selectivity for silicon nitride films relative to silicon oxide films compared to conventional silane-based etching compositions, even when the additive content is small, and a method for producing the same.

[0008] In this disclosure, we have investigated phosphoric acid-based etching compositions containing silane compounds. As a result, we have found that phosphoric acid-based etching compositions containing specific silane compounds as additives exhibit excellent etching selectivity even with small amounts of the additive, and in particular, exhibit etching selectivity equal to or higher than that of allyltrimethoxysilane disclosed in Non-Patent Document 1.

[0009] That is, the present invention is as defined in the claims, and the gist of the present disclosure is as follows. [1] An etching composition containing phosphoric acid, allyltriethoxysilane, and a solvent. [2] The etching composition according to [1] above, wherein the content of the allyltriethoxysilane is 0.005% by mass or more and 10% by mass or less. [3] The etching composition according to [1] or [2] above, wherein the content of the allyltriethoxysilane is 0.01% by mass or more and 0.5% by mass or less. [4] The etching composition according to any one of [1] to [3] above, wherein the concentration of the phosphoric acid is 60% by mass or more and 95% by mass or less. [5] The etching composition according to any one of [1] to [4] above, wherein the solvent contains water. [6] The etching composition according to any one of [1] to [5] above, wherein the solvent is a water-alcohol mixed solvent. [7] The etching composition according to any one of [1] to [6] above, wherein the decomposition product of allyltriethoxysilane is included. [8] A method for producing the etching composition according to any one of [1] to [7] above, which comprises heat treating an aqueous solution containing allyltriethoxysilane and phosphoric acid at a temperature of 80° C. or higher but lower than 160° C. [9] A method for etching a silicon nitride film using the etching composition according to any one of [1] to [7] above.

[10] A method for producing a semiconductor memory, which comprises etching using the etching composition according to any one of [1] to [7] above.

[0010] According to the present disclosure, it is possible to provide at least one of an etching composition that does not require silicate and has a high etching selectivity for silicon nitride films relative to silicon oxide films, compared to conventional silane-based etching compositions, even when the additive content is small, and a method for producing the same.

[0011] The present disclosure will be described with reference to an example embodiment. The terms used in this embodiment are as follows. The configurations and parameters disclosed in this specification can be combined in any desired manner, and the upper and lower limits of the values ​​disclosed in this specification can be combined in any desired manner.

[0012] [Etching Composition] This embodiment is an etching composition containing phosphoric acid, allyltriethoxysilane, and a solvent. The etching composition of this embodiment can be used for selectively etching a silicon nitride film, particularly a silicon oxide film and a silicon nitride film from a substrate having the silicon nitride film.

[0013] (Phosphoric Acid) The etching composition of this embodiment contains phosphoric acid, which promotes etching of the silicon nitride film.

[0014] The phosphoric acid contained in the etching composition of the present embodiment is orthophosphoric acid (H ３ P.O. ４ ), pyrophosphate (H ４ P ２ O ７ ), metaphosphoric acid (HPO ３ ) ｎ (n is a positive integer), and polyphosphoric acid (HO(HPO ３ ) ｎ H) (n is a positive integer).

[0015] The content of phosphoric acid in the etching composition of this embodiment is, as a mass ratio of phosphoric acid to the mass of the etching composition, 60 mass% or more, or 80 mass% or more, and 95 mass% or less, or 90 mass% or less, for example, and this mass ratio is preferably 60 mass% or more and 95 mass% or less, or 80 mass% or more and 90 mass% or less.

[0016] The content of phosphoric acid in the etching composition of the present embodiment is the mass ratio of phosphoric acid to the mass of the etching composition.

[0017] (Allyltriethoxysilane) The etching composition of this embodiment contains allyltriethoxysilane. Allyltriethoxysilane is included as a silane compound additive. As a result, the etching composition of this embodiment exhibits a high etching selectivity even with a lower additive content, compared to phosphoric acid-based etching compositions containing other silane compounds, particularly phosphoric acid-based etching compositions containing allyltrimethoxysilane. One of the reasons for the high etching selectivity even with a low additive content is that, compared to other silane compounds, particularly allyltrimethoxysilane, allyltriethoxysilane is more likely to selectively form a protective layer on a silicon oxide film, and the formation of such a protective layer is thought to suppress etching of the silicon oxide film.

[0018] Furthermore, the etching composition of this embodiment may contain, in addition to allyltriethoxysilane, a decomposition product of allyltriethoxysilane (hereinafter also referred to as a "partial decomposition product"). The partial decomposition product is a silane compound obtained by partial decomposition of allyltriethoxysilane by hydrolysis or the like, and is considered to have a higher film-forming ability, i.e., a higher protective layer-forming ability, on silicon oxide films than allyltriethoxysilane. Therefore, by including the partial decomposition product, etching of silicon oxide films is further suppressed. Furthermore, the partial decomposition product is considered to be preferable for suppressing precipitates derived from allyltriethoxysilane.

[0019] The partial decomposition product is a compound represented by the general formula (CH ２ =CHCH ２ )Si(OH) ｎ (OEt) ３－ｎ (wherein Et is an ethyl group, and n is an integer of 1 to 3)

[0020] The content of allyltriethoxysilane, expressed as the mass ratio of allyltriethoxysilane to the mass of the etching composition, is 0.005 mass% or more, 0.01 mass% or more, 0.05 mass% or more, or 0.1 mass% or more, and may be 10 mass% or less, 5 mass% or less, 3 mass% or less, 1 mass% or less, 0.8 mass% or less, 0.5 mass% or less, 0.3 mass% or less, or 0.25 mass% or less. The content of allyltriethoxysilane is preferably 0.005% by mass to 10% by mass, 0.005% by mass to 3% by mass, 0.005% by mass to 0.8% by mass, 0.01% by mass to 0.8% by mass, 0.01% by mass to 0.5% by mass, 0.01% by mass to 0.3% by mass, 0.05% by mass to 0.3% by mass, 0.05% by mass to 0.25% by mass, 0.1% by mass to 0.3% by mass, or 0.1% by mass to 0.25% by mass. When the content of allyltriethoxysilane satisfies this range, the etching selectivity is likely to be high, and precipitates derived from allyltriethoxysilane can be suppressed. By suppressing the precipitates, the etching composition of this embodiment can be used to etch laminated substrates having finer structures. Furthermore, the etching selectivity does not necessarily increase with an increase in the content of allyltriethoxysilane, and in order to obtain a high etching selectivity, the content of allyltriethoxysilane is preferably 0.3 mass% or less, or 0.25 mass% or less. When the etching composition of the present embodiment contains a partial decomposition product, for convenience, the total content of the partial decomposition product and allyltriethoxysilane may be regarded as the content of allyltriethoxysilane.

[0021] (Solvent) The etching composition of this embodiment contains a solvent. The solvent may be at least one of water and alcohol, or even water. The water may be one or more selected from the group consisting of ion-exchanged water, distilled water, pure water, and ultrapure water. Furthermore, when the raw materials of phosphoric acid and allyltriethoxysilane are in the form of a solution, the solvent of this solution can function as the solvent for the etching composition of this embodiment. The solvent is preferably water and alcohol, more preferably water and ethanol, or even a water-alcohol mixed solvent. The solvent is particularly preferably water and ethanol produced by hydrolysis of allyltriethoxysilane.

[0022] (Other Components) The etching composition of the present embodiment may contain additives other than allyltriethoxysilane, for example, at least one of a silicon compound other than allyltriethoxysilane and a fluorine compound, as long as the effect of the etching composition is not impaired.

[0023] As described above, the etching composition of this embodiment does not necessarily contain silicate. Therefore, the etching composition of this embodiment can have a low concentration of counter cations, particularly metal counter cations such as sodium. For example, the etching composition of this embodiment may have a metal ion concentration of 1.00 mass% or less, 0.50 mass% or less, 0.10 mass% or less, 0.05 mass% or less, 0.01 mass% or less, 0.005 mass% or less, 0.001 mass% or less, 0.0005 mass% or less, or 0.0001 mass% or less (1 ppm). The lower limit of the metal ion concentration may be greater than 0 mass% and greater than or equal to 0.00001 mass%.

[0024] (Composition (Content)) The composition (content) of the etching composition of this embodiment can be measured by known methods. For example, the phosphoric acid content can be determined by molybdenum blue absorptiometry, the water content can be determined by a Karl Fischer moisture meter, and the allyltriethoxysilane content can be determined by nuclear magnetic resonance analysis. The metal ion concentration can be determined by ICP-MASS.

[0025] [Method for Producing Etching Composition] A preferred method for producing the etching composition of this embodiment includes heat-treating an aqueous solution containing allyltriethoxysilane and phosphoric acid at 80°C or higher but lower than 160°C (hereinafter also referred to as the "heat treatment step"). This heat treatment partially decomposes allyltriethoxysilane to produce a partial decomposition product. The partial decomposition product is thought to have a high ability to form a protective layer for the silicon oxide film, thereby exhibiting a high etching selectivity. In addition, ethanol is produced along with the partial decomposition product, and the solvent becomes a mixed solvent of water and alcohol. Note that, in this embodiment, the term "aqueous solution" refers to a solution containing at least water, particularly a solution in which 1% by mass or more, 3% by mass or more, 5% by mass or more, 10% by mass or more, 20% by mass or more, 30% by mass or more, 40% by mass or more, 50% by mass or more, 60% by mass or more, 70% by mass or more, 80% by mass or more, or 90% by mass or more of the solvent is water. The upper limit of the water content in the aqueous solution can be, for example, 99% by mass or less, 98% by mass or less, or 95% by mass or less, and the water content in the aqueous solution can be, for example, 1% by mass to 99% by mass, 10% by mass to 98% by mass, or 50% by mass to 95% by mass.

[0026] The aqueous solution containing allyltriethoxysilane and phosphoric acid (hereinafter also referred to as "raw aqueous solution") to be subjected to the heat treatment step may contain phosphoric acid and allyltriethoxysilane, and may also contain water as a solvent. The raw aqueous solution is preferably in a state obtained by mixing an aqueous phosphoric acid solution with allyltriethoxysilane, and more preferably in a state obtained by adding allyltriethoxysilane to an aqueous phosphoric acid solution.

[0027] The content of phosphoric acid in the raw material aqueous solution is, for example, 60% by mass or more or 80% by mass or more, and 95% by mass or less or 90% by mass or less, and preferably 60% by mass or more and 95% by mass or less, or 80% by mass or more and 90% by mass or less.

[0028] The content of allyltriethoxysilane in the raw material aqueous solution is preferably 0.005% by mass or more, 0.01% by mass or more, 0.05% by mass or more, or 0.1% by mass or more, and 10% by mass or less, 5% by mass or less, 3% by mass or less, 1% by mass or less, 0.8% by mass or less, 0.5% by mass or less, 0.3% by mass or less, or 0.25% by mass. Furthermore, this content is preferably 0.005% by mass or more and 10% by mass or less, 0.005% by mass or more and 3% by mass or less, 0.005% by mass or more and 0.8% by mass or less, 0.01% by mass or more and 0.8% by mass or less, 0.01% by mass or more and 0.5% by mass or less, 0.01% by mass or more and 0.3% by mass or less, 0.05% by mass or more and 0.3% by mass or less, 0.05% by mass or more and 0.25% by mass or less, 0.1% by mass or more and 0.3% by mass or less, or 0.1% by mass or more and 0.25% by mass or less.

[0029] In the heat treatment step, for example, the raw material aqueous solution is heat treated at a temperature of 80°C or higher and lower than 160°C. This is thought to cause local decomposition of allyltriethoxysilane. As a result, ethanol is produced and allyltriethoxysilane is more likely to form a protective layer on the silicon oxide film. The heat treatment is preferably carried out in a sealed state. On the other hand, at temperatures above 160°C, the decomposition of allyltriethoxysilane proceeds excessively, resulting in a decrease in the etching selectivity. Preferred heat treatment conditions include the following: Heat treatment atmosphere: oxidizing atmosphere or inert atmosphere, preferably air atmosphere Heat treatment temperature: 80°C or higher, 100°C or higher, 110°C or higher, 115°C or higher, or 120°C or higher, and lower than 160°C, 155°C or lower, 150°C or lower, 140°C or lower, or 130°C or lower (for example, 80°C or higher and lower than 160°C, 100°C or higher and 155°C or lower, 110°C or higher and 150°C or lower, 115°C or higher and 140°C or lower, or 120°C or higher and 130°C or lower) Heat treatment pressure: autogenous pressure

[0030] The heat treatment time may be adjusted appropriately depending on the amount of etching composition to be produced and the scale of the production apparatus, and may be, for example, 5 minutes or more, or 7 minutes or more, and may be 120 hours or less, 30 minutes or less, or 15 minutes or less. In addition, the heat treatment time may be, for example, 5 minutes or more and 120 hours or less, 5 minutes or more and 30 minutes or less, or 7 minutes or more and 15 minutes or less.

[0031] Note that other examples of the method for producing the etching composition of this embodiment include a production method that does not include a heat treatment step. That is, for example, examples of the method for producing the etching composition of this embodiment include a production method that includes mixing at least one of allyltriethoxysilane and a solution containing allyltriethoxysilane, and at least one of phosphoric acid and a solution containing phosphoric acid, with a solvent, and further examples of the method for producing the etching composition of this embodiment include a production method that includes mixing a solution containing phosphoric acid and allyltriethoxysilane.

[0032] [Etching Method] The etching composition of this embodiment can be used for etching a silicon nitride film, particularly for selectively etching a silicon nitride film on a substrate having a silicon oxide film and a silicon nitride film. Etching of a silicon nitride film using the etching composition of this embodiment may be performed by an etching method including contacting the etching composition of this embodiment with a substrate having a silicon nitride film, particularly a substrate having a silicon oxide film and a silicon nitride film (hereinafter also referred to as an "etching step").

[0033] The etching step provides a substrate having a silicon nitride film. The substrate may be any substrate used as a semiconductor, particularly a semiconductor used in a NAND memory, and may be one or more selected from the group consisting of a silicon substrate, a SiC substrate, a sapphire substrate, and a glass substrate, with a silicon substrate being preferred.

[0034] The substrate has a silicon nitride film on its surface, which may be formed by one or more methods selected from the group consisting of low-pressure chemical vapor deposition (LPCVD), plasma-enhanced chemical vapor deposition (PECVD), and atomic layer deposition (ALD).

[0035] The substrate may have a silicon oxide film in addition to a silicon nitride film (hereinafter, a substrate having at least one of a silicon nitride film and a silicon oxide film will also be referred to as a "film-coated substrate"). The silicon oxide film may be formed by any method, but examples of the silicon oxide film include silicon oxide films formed by one or more methods selected from the group consisting of thermal oxidation, low-pressure chemical vapor deposition (LPCVD), plasma-enhanced chemical vapor deposition (PECVD), and atomic layer deposition (ALD), as well as silicon oxide films formed by at least one of PECVD and thermal oxidation. Silicon oxide films formed by thermal oxidation are less susceptible to etching by the etching composition of this embodiment.

[0036] The substrate may be a substrate having a silicon nitride film and a silicon oxide film, particularly a substrate having a laminated film in which a silicon nitride film and a silicon oxide film are stacked.

[0037] In the etching step, the etching composition of the present embodiment is brought into contact with a substrate having a silicon nitride film. This etches the silicon nitride film. The etching composition can be brought into contact with the substrate by any method, for example, by immersing the substrate having a silicon nitride film in the etching composition of the present embodiment, by passing the etching composition of the present embodiment over the substrate having a silicon nitride film, or by spraying the etching composition of the present embodiment onto the substrate having a silicon nitride film.

[0038] The temperature for contact may be any temperature at which etching with phosphoric acid proceeds, and may be, for example, 100° C. or higher, 120° C. or higher, 140° C. or higher, or 150° C. or higher, and may be 200° C. or lower, 180° C. or lower, 170° C. or lower, or 160° C. or lower. This temperature is, for example, 100° C. or higher and 200° C. or lower, or 120° C. or higher and 180° C. or lower, and is preferably 140° C. or higher and 170° C. or lower, or 150° C. or higher and 160° C. or lower.

[0039] The contact time can be adjusted appropriately depending on the size of the substrate to be subjected to the etching process, the shape of the silicon nitride film, and the desired etching degree. The longer the contact time, the more the etching progresses. The contact time may be, for example, 1 minute or more, or 5 minutes or more, and may be 1,440 minutes or less, or 240 minutes or less. This time may be, for example, 1 minute or more and 1,440 minutes or less, or even 5 minutes or more and 240 minutes or less.

[0040] The etching composition of the present embodiment can be applied to a method for manufacturing a semiconductor memory, which includes etching using the etching composition, and further, the etching composition of the present embodiment can be applied to a method for manufacturing a semiconductor memory having a 3D structure, which includes etching using the etching composition.

[0041] The present disclosure will be described in detail below with reference to examples, but the present disclosure is not limited to these examples.

[0042] (Film Thickness Measurement) Using a diamond cutter, silicon substrates having a silicon nitride film or a silicon oxide film (hereinafter also referred to as "film-coated substrates") were cut into 10 mm x 10 mm square plates to serve as measurement samples. Using a microspectrophotometer (device name: OPTM-F1, manufactured by Otsuka Electronics Co., Ltd.), the film thickness of the film-coated wafers was measured under the following conditions. Measurements were made at five points per sample, and the average value was taken as the film thickness of the measurement sample. Number of measurements: 20 Exposure time: 100 msec Wavelength range: 230 to 800 nm

[0043] Examples 1 to 10 Allyltriethoxysilane (product name: Allyltriethoxysilane, manufactured by Tokyo Chemical Industry Co., Ltd.) was weighed and filled into a 100 mL plastic container so as to obtain the composition shown in Table 1 below, and then an 85% aqueous phosphoric acid solution (product name: EL-S, manufactured by Rinkagaku Kogyo Co., Ltd.) was gradually added to obtain a mixed aqueous solution. The obtained mixed aqueous solution was stirred and then heat-treated together with the plastic container in an air atmosphere at 120°C for 10 minutes, thereby obtaining an etching composition of this example.

[0044] Example 11 An etching composition of this example was obtained in the same manner as in Example 3, except that the heat treatment in an air atmosphere at 120° C. for 10 minutes was not carried out.

[0045] Comparative Example 1 An etching composition of this comparative example was obtained in the same manner as in Example 7, except that 0.250 g of n-octyltrimethoxysilane was used instead of 0.250 g of allyltriethoxysilane.

[0046] The etching compositions of the Examples and Comparative Examples obtained as described above did not substantially contain metal ions.

[0047] [Etching Treatment] Silicon nitride film-coated silicon substrates having silicon nitride films formed by PECVD and silicon oxide film-coated silicon substrates having silicon oxide films formed by PECVD were immersed in the etching compositions of Examples 1 to 8 and 11 and Comparative Example 1, respectively, and then etched by heating at 157°C. The etching time for the silicon nitride film-coated silicon substrates was 5 minutes. On the other hand, the silicon oxide film was not etched at all when the etching time was 10 minutes. Therefore, the etching time for the silicon oxide film-coated silicon substrates was 240 minutes.

[0048] After the etching treatment, the film thickness was measured for the film-coated substrate after washing with pure water and air-drying, and for the film-coated substrate before the etching treatment. From the results obtained, the etching rate and etching selectivity were calculated using the following formulas.

[0049] ER = (T ＢＦ -T ＡＦ ) / E ｔ (1) In the above formula, ER is the etching rate [nm / min], T ＡＦ is the film thickness after etching [nm], T ＢＦ is the film thickness [nm] before etching, and E ｔ is the etching processing time [min].

[0050] ES = ER ＳｉＮ / ER ＳｉＯ２(2) In the above formula, ES is the etching selectivity, ER ＳｉＮ is the etching rate of the silicon nitride film [nm / min], and ER ＳｉＯ２ is the etching rate of the silicon oxide film [nm / min]. The results are shown in Table 1.

[0051]

[0052] From the above table, it was confirmed that, up to a certain content of allyltriethoxysilane, the etching selectivity tends to increase as the content of allyltriethoxysilane increases, and in particular, the etching selectivity tends to increase due to a decrease in the etching rate of the silicon oxide film. On the other hand, since Example 7, in which the content of allyltriethoxysilane was 0.250 mass%, had a higher etching selectivity than Example 8, in which the content of allyltriethoxysilane was 0.500 mass%, it was confirmed that there is an appropriate range for the content of allyltriethoxysilane in order to obtain a high etching selectivity.

[0053] Furthermore, the etching selectivity of the etching composition of Example 1, in which the content of allyltriethoxysilane was 0.010 mass%, was 250, and it was confirmed that this selectivity was comparable to the etching selectivity disclosed in Non-Patent Document 1. Furthermore, Example 4, in which the additive content (0.100 mass%) was about 1 / 10 of the additive concentration (0.1 M) disclosed in Non-Patent Document 1, had an etching selectivity of 1400, which was confirmed to be an extremely high etching selectivity compared to the etching composition of Non-Patent Document 1 containing allyltrimethoxysilane as an additive.

[0054] Comparing Example 7 with Comparative Example 1, it was confirmed that Example 7 had a lower etching rate for the silicon oxide film, and therefore the etching selectivity of Example 7 (25,000) was significantly larger (227 times) than the etching selectivity of Comparative Example 1 (110). This confirmed that the inclusion of allyltriethoxysilane increased the etching selectivity.

[0055] By comparing Example 3, which was subjected to heat treatment in an air atmosphere at 120°C for 10 minutes, with Example 11, which was not subjected to this heat treatment, it was confirmed that the etching composition that was not heat-treated also had an etching selectivity ratio equivalent to that of the etching composition that was heat-treated.

[0056] Furthermore, using the etching composition of Example 7, etching treatment was carried out on a silicon substrate having a silicon oxide film formed by a PECVD method, as well as on a silicon substrate having a silicon oxide film formed by a thermal oxidation method. The results are shown in Table 2 below.

[0057]

[0058] It was confirmed that the etching rate of the silicon oxide film formed by thermal oxidation is slower than that of the silicon oxide film formed by PECVD. This confirms that etching with a higher etching selectivity can be achieved by forming the silicon oxide film by thermal oxidation and the silicon nitride film by PECVD.

Claims

1. An etching composition containing phosphoric acid, allyltriethoxysilane, and a solvent.

2. The etching composition according to claim 1, wherein the content of the allyltriethoxysilane is 0.005% by mass or more and 10% by mass or less.

3. The etching composition according to claim 1 or 2, wherein the content of the allyltriethoxysilane is 0.01 mass % or more and 0.5 mass % or less.

4. An etching composition according to any one of claims 1 to 3, wherein the concentration of the phosphoric acid is 60 mass% or more and 95 mass% or less.

5. The etching composition of any one of claims 1 to 4, wherein the solvent comprises water.

6. The etching composition according to any one of claims 1 to 5, wherein the solvent is a water-alcohol mixed solvent.

7. The etching composition according to any one of claims 1 to 6, comprising a decomposition product of allyltriethoxysilane.

8. A method for producing the etching composition according to any one of claims 1 to 7, comprising heat-treating an aqueous solution containing allyltriethoxysilane and phosphoric acid at a temperature of 80°C or higher and lower than 160°C.

9. A method for etching a silicon nitride film, comprising using an etching composition according to any one of claims 1 to 7.

10. A method for manufacturing a semiconductor memory, comprising etching with the etching composition according to any one of claims 1 to 7.

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