Classifications

• • C—CHEMISTRY; METALLURGY
  • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
  • C09K—MATERIALS FOR MISCELLANEOUS APPLICATIONS, NOT PROVIDED FOR ELSEWHERE
  • C09K13/00—Etching, surface-brightening or pickling compositions
  • C09K13/04—Etching, surface-brightening or pickling compositions containing an inorganic acid
• • H—ELECTRICITY
  • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
  • H10P—GENERIC PROCESSES OR APPARATUS FOR THE MANUFACTURE OR TREATMENT OF DEVICES COVERED BY CLASS H10
  • H10P50/00—Etching of wafers, substrates or parts of devices
• • H—ELECTRICITY
  • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
  • H10P—GENERIC PROCESSES OR APPARATUS FOR THE MANUFACTURE OR TREATMENT OF DEVICES COVERED BY CLASS H10
  • H10P50/00—Etching of wafers, substrates or parts of devices
  • H10P50/69—Etching of wafers, substrates or parts of devices using masks for semiconductor materials
  • H10P50/691—Etching of wafers, substrates or parts of devices using masks for semiconductor materials for Group V materials or Group III-V materials

Definitions

• the present disclosure relates to an etching composition, and more particularly to an etching composition suitable for selectively etching silicon nitride films.
• NAND type flash memory is manufactured by a manufacturing method having an etching process for selectively removing only silicon nitride film from a substrate in which silicon oxide films such as silicon dioxide (SiO 2 ) films and silicon nitride films such as silicon nitride (Si 3 N 4 ) films are alternately laminated.
• silicon oxide films such as silicon dioxide (SiO 2 ) films
• silicon nitride films such as silicon nitride (Si 3 N 4 ) films are alternately laminated.
• Si 3 N 4 silicon nitride
• an etching composition that can more selectively etch and remove silicon nitride film is required in the etching process, and in particular, a phosphoric acid-based etching composition containing a silane compound as an additive has been studied.
• Patent Document 1 discloses an etching composition for silicon nitride that contains a silane coupling agent and water.
• the etching composition is said to contain an inorganic silicate, and thus exhibits high selectivity for silicon nitride films, with the etching rate of the silicon nitride film relative to the etching rate of the silicon oxide film being 1000 or more.
• Non-Patent Document 1 reports a phosphoric acid-based etching composition that contains allylmethoxysilane as an additive.
• Patent Document 1 the addition of silicate increases the etching selectivity.
• etching compositions containing silicate are contaminated with counter cations, particularly metal counter cations such as sodium, after etching.
• the etching composition disclosed in Non-Patent Document 1 does not have sufficient selectivity, with an etching selectivity ratio of only about 120 to 280, even though the additive content is a relatively high concentration of 0.1 M (0.95 mass%).
• the present disclosure aims to provide at least one of an etching composition that does not require silicate and has a high etching selectivity ratio of silicon nitride film to silicon oxide film compared to conventional silane-based etching compositions, even with a small amount of additives, and a method for producing the same.
• An etching composition comprising phosphoric acid, allyltrimethoxysilane, a decomposition product of allyltrimethoxysilane, and a solvent.
• etching composition according to any one of the above [1] to [6], wherein the decomposition product of allyltrimethoxysilane is a silane compound represented by the general formula (CH 2 ⁇ CHCH 2 )Si(OH) n (OMet) 3-n (wherein Met is a methyl group, and n is an integer of 1 to 3).
• the present disclosure makes it possible to provide at least one of an etching composition and a method for producing the same that does not require silicate and has a high etching selectivity for silicon nitride film relative to silicon oxide film compared to conventional silane-based etching compositions, even with a small amount of additives.
• the present embodiment is an etching composition containing phosphoric acid, allyltrimethoxysilane, a decomposition product of allyltrimethoxysilane, and a solvent.
• the etching composition of the present embodiment can be used for selective etching of a silicon nitride film, particularly for selective etching of a silicon nitride film from a substrate having a silicon oxide film and a silicon nitride film.
• the etching composition of the present embodiment contains phosphoric acid, which promotes etching of the silicon nitride film.
• the phosphoric acid contained in the etching composition of the present embodiment is at least one selected from the group consisting of orthophosphoric acid (H 3 PO 4 ), pyrophosphoric acid (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).
• the content of phosphoric acid in the etching composition of this embodiment is, as the 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.
• this mass ratio is preferably 60 mass% or more and 95 mass% or less, or 80 mass% or more and 90 mass% or less.
• the content of phosphoric acid in the etching composition of this embodiment is the mass ratio of phosphoric acid to the mass of the etching composition.
• the etching composition of the present embodiment contains allyltrimethoxysilane. Allyltrimethoxysilane is included as a silane compound additive. As a result, the etching composition of the present embodiment exhibits a high etching selectivity.
• the etching composition of this embodiment contains allyltrimethoxysilane as well as a decomposition product of allyltrimethoxysilane (hereinafter also referred to as a "partial decomposition product").
• the partial decomposition product is a silane compound formed by partial decomposition of allyltrimethoxysilane 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 allyltrimethoxysilane. 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 allyltrimethoxysilane.
• the partial decomposition product is, for example, a silane compound represented by the general formula (CH 2 ⁇ CHCH 2 )Si(OH) n (OMet) 3-n (wherein Met is a methyl group, and n is an integer of 1 to 3).
• the content of allyltrimethoxysilane is 0.005 mass% or more, 0.01 mass% or more, 0.02 mass% or more, 0.05 mass% or more, or 0.1 mass% or more, and can 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, 0.25 mass% or less, 0.2 mass% or less, or 0.175 mass% or less.
• the content of allyltrimethoxysilane is 0.005 mass% or more and 10 mass% or less, 0.005 mass% or more and 3 mass% or less, 0.005 mass% or more and 0.8 mass% or less, 0.01 mass% or more and 0.8 mass% or less, 0.01 mass% or more and 0.5 mass% or less, 0.02 mass% or more and 0.5 mass% or less, 0.02 mass% or more and 0.3 mass% or less.
• the etching selectivity is likely to be high, and precipitates derived from allyltrimethoxysilane are suppressed.
• the etching composition of this embodiment can be applied to etching of laminated substrates having finer structures.
• the etching selectivity does not increase as the content of allyltrimethoxysilane increases, and in order to obtain a high etching selectivity, the content of allyltrimethoxysilane is preferably 0.3 mass% or less, 0.25 mass% or less, 0.2 mass% or less, or 0.175 mass% or less.
• the total content of the partial decomposition product and allyltrimethoxysilane may be regarded as the content of allyltrimethoxysilane.
• the etching composition of this embodiment contains a solvent.
• the solvent may be at least one of water and alcohol, and may further be water.
• the water may be one or more selected from the group consisting of ion-exchanged water, distilled water, pure water, and ultrapure water.
• the solvent of this solution can function as the solvent of the etching composition of this embodiment.
• the solvent is preferably water and alcohol, more preferably water and methanol, or even a water-alcohol mixed solvent.
• the solvent is particularly preferably water and methanol produced by hydrolysis of allyltrimethoxysilane.
• the etching composition of the present embodiment may contain additives other than allyltrimethoxysilane, for example, at least one of a silicon compound other than allyltrimethoxysilane and a fluorine compound, as long as the effect of the composition is not impaired.
• the etching composition of this embodiment does not necessarily require silicate. Therefore, the etching composition of this embodiment can have a low concentration of counter cations, particularly metal counter cations such as sodium.
• 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 more than 0 mass% and 0.00001 mass% or more.
• composition (content) The composition (content) of the etching composition of this embodiment can be measured by a known method.
• the phosphoric acid content can be measured by molybdenum blue absorptiometry
• the water content can be measured by a Karl Fischer moisture meter
• the allyltrimethoxysilane content can be measured by nuclear magnetic resonance analysis.
• the metal ion concentration can be measured by ICP-MASS.
• a preferred method for producing the etching composition of this embodiment includes a production method including heat-treating an aqueous solution containing allyltrimethoxysilane and phosphoric acid at 80° C. or more and less than 160° C. (hereinafter also referred to as a "heat treatment step").
• This heat treatment partially decomposes allyltrimethoxysilane to produce a partial decomposition product.
• the partial decomposition product is considered to have a high ability to form a protective layer for the silicon oxide film, and thus shows a high etching selectivity.
• methanol is produced together with the partial decomposition product, and the solvent becomes a mixed solvent of water and alcohol.
• the "aqueous solution” means a solution in which the solvent contains 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 99% by mass or less, 98% by mass or less, or 95% by mass or less.
• the water content in the aqueous solution can be, for example, from 1% by mass to 99% by mass, from 10% by mass to 98% by mass, or from 50% by mass to 95% by mass.
• the aqueous solution containing allyltrimethoxysilane and phosphoric acid (hereinafter also referred to as the "raw aqueous solution") to be subjected to the heat treatment step may contain phosphoric acid and allyltrimethoxysilane, and may further contain water as a solvent.
• the raw aqueous solution is preferably in a state obtained by mixing an aqueous phosphoric acid solution with allyltrimethoxysilane, and more preferably in a state obtained by adding allyltrimethoxysilane to an aqueous phosphoric acid solution.
• the phosphoric acid content in the raw aqueous solution is 60% by mass or more, or 80% by mass or more, and 95% by mass or less, or 90% by mass or less. This content is preferably 60% by mass or more and 95% by mass or less, or 80% by mass or more and 90% by mass or less.
• the content of allyltrimethoxysilane in the raw aqueous solution is preferably 0.005% by mass or more, 0.01% by mass or more, 0.02% by mass or more, 0.05% by mass or more, or 0.1% by mass or more, and is preferably 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, 0.25% by mass or less, 0.2% by mass or less, or 0.175% by mass or less.
• this content is 0.005 mass% or more and 10 mass% or less, 0.005 mass% or more and 3 mass% or less, 0.005 mass% or more and 0.8 mass% or less, 0.01 mass% or more and 0.8 mass% or less, 0.01 mass% or more and 0.5 mass% or less, 0.02 mass% or more and 0.5 mass% or less, 0.02 mass% or more and 0.3 mass% or less, 0.0 It is preferable that the content is 2% by mass or more and 0.25% by mass or less, 0.02% by mass or more and 0.175% by mass or less, 0.05% by mass or more and 0.5% by mass or less, 0.05% by mass or more and 0.3% by mass or less, 0.05% by mass or more and 0.2% by mass or less, 0.05% by mass or more and 0.175% by mass or less, or 0.1% by mass or more and 0.3% by mass or less.
• the raw material aqueous solution is heat treated at 80° C. or more and less than 160° C. This is believed to cause local decomposition of allyltrimethoxysilane. As a result, it is believed that methanol is generated and allyltrimethoxysilane is in a state where it is more likely to form a protective layer on the silicon oxide film. It is preferable to perform the heat treatment in a sealed state. On the other hand, at 160° C. or more, the decomposition of allyltrimethoxysilane proceeds excessively, the generation of partial decomposition products is inhibited, and the etching selectivity ratio decreases. The following conditions are preferable as heat treatment conditions.
• Heat treatment atmosphere oxidizing atmosphere or inert atmosphere, preferably air atmosphere
• Heat treatment temperature 80°C or more, 100°C or more, 110°C or more, 115°C or more, or 120°C or more, and less than 160°C, 155°C or less, 150°C or less, 140°C or less, or 130°C or less (for example, 80°C or more and less than 160°C, 100°C or more and 155°C or less, 110°C or more and 150°C or less, 115°C or more and 140°C or less, or 120°C or more and 130°C or less)
• Heat treatment pressure Autogenous pressure
• the heat treatment time may be adjusted appropriately depending on the amount of etching composition to be produced and the scale of the production equipment, 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, examples of the heat treatment time include 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.
• the etching composition of the present embodiment can be used for etching a silicon nitride film, particularly for selective etching of a silicon nitride film on a substrate having a silicon oxide film and a silicon nitride film.
• the etching of a silicon nitride film using the etching composition of the present embodiment may be performed by an etching method including contacting the etching composition of the present 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").
• the etching process provides a substrate having a silicon nitride film.
• the substrate may be any substrate used as a semiconductor, and more particularly, a semiconductor used in a NAND memory, and may be one or more substrates selected from the group consisting of silicon substrates, SiC substrates, sapphire substrates, and glass substrates, with a silicon substrate being preferred.
• the substrate has a silicon nitride film on its surface.
• the silicon nitride film 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).
• LPCVD low pressure chemical vapor deposition
• PECVD plasma enhanced chemical vapor deposition
• ALD atomic layer deposition
• the substrate may have a silicon oxide film in addition to the silicon nitride film (hereinafter, a substrate having at least one of a silicon nitride film and a silicon oxide film is also referred to as a "film-coated substrate").
• the method for forming the silicon oxide film is arbitrary, 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), and silicon oxide films formed by at least one of PECVD and thermal oxidation.
• LPCVD low pressure chemical vapor deposition
• PECVD plasma enhanced chemical vapor deposition
• ALD atomic layer deposition
• the substrate may be a substrate having a silicon nitride film and a silicon oxide film, in particular a substrate having a laminated film in which a silicon nitride film and a silicon oxide film are stacked.
• the etching composition of this embodiment is brought into contact with a substrate having a silicon nitride film. This etches the silicon nitride film.
• the method of bringing the etching composition into contact with the substrate is arbitrary, and examples of the method include immersing the substrate having a silicon nitride film in the etching composition of this embodiment, passing the etching composition of this embodiment over the substrate having a silicon nitride film, spraying the etching composition of this embodiment onto the substrate having a silicon nitride film, and the like.
• the contact temperature may be any temperature at which etching with phosphoric acid proceeds, and may be, for example, 100°C or more, 120°C or more, 140°C or more, or 150°C or more, and may be 200°C or less, 180°C or less, 170°C or less, or 160°C or less.
• This temperature is, for example, 100°C or more and 200°C or less, or 120°C or more and 180°C or less, and is preferably 140°C or more and 170°C or less, or 150°C or more and 160°C or less.
• the contact time can be adjusted as appropriate depending on the size of the substrate to be subjected to the etching process, the shape of the silicon nitride film, and the desired degree of etching. 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 1440 minutes or less, or 240 minutes or less. Examples of this time include 1 minute or more and 1440 minutes or less, and further 5 minutes or more and 240 minutes or less.
• the etching composition of this embodiment can be applied to a method for manufacturing a semiconductor memory, which includes etching using the etching composition of this embodiment, and further, the etching composition of this embodiment can be applied to a method for manufacturing a semiconductor memory having a 3D structure, which includes etching using the etching composition of this embodiment.
• film thickness measurement 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 prepare measurement samples.
• 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 performed at five points per sample, and the average value was taken as the film thickness of the measurement sample. Accumulation count: 20 times Exposure time: 100 msec Wavelength range: 230 to 800 nm
• Comparative Example 1 An etching composition of this comparative example was obtained in the same manner as in Example 8, except that 0.500 g of n-octyltrimethoxysilane was used instead of 0.500 g of allyltrimethoxysilane.
• Comparative Example 2 An etching composition of this comparative example was obtained in the same manner as in Example 8, except that 0.500 g of hexadecyltriethoxysilane was used instead of 0.500 g of allyltrimethoxysilane.
• Comparative Example 3 An etching composition of this comparative example was obtained in the same manner as in Example 2, except that the heat treatment in the air at 120° C. for 10 minutes was not performed.
• etching compositions of the examples and comparative examples obtained as described above did not substantially contain metal ions.
• a silicon substrate with a silicon nitride film having a silicon nitride film formed by a PECVD method and a silicon substrate with a silicon oxide film having a silicon oxide film formed by a PECVD method were immersed in the etching compositions of Examples 1 to 9 and Comparative Examples 1 to 3, respectively, and etched by heating at 157° C.
• the etching time for the silicon substrate with a silicon nitride film was 5 minutes.
• the silicon oxide film was not etched at all when the etching time was 10 minutes. Therefore, the etching time for the silicon substrate with a silicon oxide film was 240 minutes.
• the film thickness was measured on the film-coated substrate after washing with pure water and air drying, and on the film-coated substrate before the etching process. From the results, the etching rate and etching selectivity were calculated using the following formula.
• ER (T BF - T AF )/E t (1)
• ER is the etching rate [nm/min]
• T AF is the film thickness after etching [nm]
• TBF is the film thickness before etching [nm]
• Et is the etching time [min]. It is.
• ES ERSiN / ERSiO2 (2)
• ES is the etching selectivity
• ER SiN is the etching rate of the silicon nitride film [nm/min]
• ER SiO2 is the etching rate of the silicon oxide film [nm/min]. The results are shown in Table 1. .
• Example 7 since the etching selectivity of Example 7, in which the allyltrimethoxysilane content is 0.175 mass%, is higher than that of Examples 8 and 9, in which the allyltrimethoxysilane content is 0.500 mass% and 2.500 mass%, respectively, it was confirmed that there is an appropriate range for the allyltrimethoxysilane content in order to obtain a high etching selectivity.
• Comparative Example 1 and Comparative Example 2 confirmed that the shorter the alkyl chain of the silane compound, the higher the etching selection option. Furthermore, it was confirmed that, although Comparative Example 1 and Example 8 have the same alkyl chain of the silane compound and the same amount of silane compound, the etching selectivity ratio of Example 8 (13,000) is significantly larger (100 times or more) than the etching selectivity ratio of Comparative Example 1 (113). Furthermore, it was confirmed that Example 5, which has an additive content (0.100 mass%) of about 1/10 of the additive concentration (0.1 M) disclosed in Non-Patent Document 1, has an etching selectivity ratio of 1700, which is extremely higher than the etching composition of Non-Patent Document 1.
• Example 2 which was heat-treated in an air atmosphere at 120°C for 10 minutes, with Comparative Example 3, which was not heat-treated, it was confirmed that the etching composition that was not heat-treated had a lower etching selectivity than the etching composition that was heat-treated. This confirmed that decomposition products of allyltrimethoxysilane were present as a result of the heat treatment, which improved the etching selectivity.
• Example 7 Furthermore, using the etching composition of Example 7, an etching process was performed on a silicon substrate with a silicon oxide film formed by a PECVD method, as well as an etching process on a silicon substrate with a silicon oxide film formed by a thermal oxidation method. The results are shown in Table 3 below.
• the etching selectivity ratio when using a silicon oxide film formed by thermal oxidation is approximately the same as the etching selectivity ratio when using a silicon oxide film formed by PECVD.
• the etching composition of this example can perform etching with a high etching selectivity ratio regardless of the method of forming the silicon oxide film.

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