Method for producing silicon nitride film on substrate having grooves

Abstract

1. A method for producing a silicon nitride film on a substrate having grooves, comprising the steps of: (a) applying a silicon nitride composition to a substrate having grooves to form a composition layer; (b) irradiating the composition layer with light having a wavelength of 200 to 229 nm; and (c) heating the substrate in a non-oxidizing atmosphere, wherein the silicon nitride film has a refractive index of 1.70 to 2.40 for light having a wavelength of 633 nm.

Description

[Technical field]

[0001] The present invention relates to a method for producing a silicon nitride film on a substrate having grooves. [Background technology]

[0002] Silicon nitride films are typically used as dielectric or sacrificial films in the manufacture of electronic devices, particularly semiconductor devices. Traditionally, silicon nitride films have been formed by chemical vapor deposition (CVD) or atomic layer deposition (ALD). In the field of electronic devices, device rules are gradually becoming finer, and there is a demand for forming silicon nitride films with finer groove structures. As miniaturization progresses, defects occurring during film formation are increasing, causing problems with reduced efficiency in the manufacture of electronic devices. In particular, the occurrence of seam defects and void defects during film formation is a problem.

[0003] Therefore, it has been proposed to form a silicon nitride film using a liquid composition containing a silicon-containing polymer. For example, a method has been proposed in which a silicon nitride stress layer is formed by filling a groove with a liquid composition containing polysilazane and heating the liquid composition at a high temperature in a nitrogen atmosphere (Patent Document 1). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] US 2009 / 0289284 A1 Summary of the Invention [Problem to be solved by the invention]

[0005] The present inventors have recognized that there are one or more problems that remain to be solved in the process for producing silicon nitride films on substrates having grooves, including, for example: Defects such as seams and voids occur during silicon nitride film formation; the silicon nitride film has low density at the bottom of the trench; the silicon nitride film has low resistance to chemical solutions; trenches with high aspect ratios cannot be filled efficiently; there is room for improvement in the quality of the silicon nitride film; and device manufacturing efficiency is low. [Means for solving the problem]

[0006] The method for producing a silicon nitride film on a substrate having grooves according to the present invention comprises the following steps: (a) applying a silicon nitride based composition to a substrate having a groove thereon to form a composition layer; (b) irradiating the composition layer with light having a wavelength of 200 to 229 nm; and (c) heating the substrate in a non-oxidizing atmosphere. The silicon nitride film has a refractive index of 1.70 to 2.40 with respect to light having a wavelength of 633 nm.

[0007] A method for producing an electronic device according to the present invention comprises the method described above. Effect of the Invention

[0008] According to the present invention, one or more of the following effects can be achieved. The occurrence of defects can be suppressed when forming the silicon nitride film; the silicon nitride film has high density even at the bottom of the trench; the silicon nitride film has high resistance to chemical solutions; trenches with high aspect ratios can be filled efficiently; the quality of the silicon nitride film is improved; and device manufacturing efficiency is high. [Brief description of the drawings]

[0009] [Figure 1] Electron microscope photograph of Example 3 after application of hydrofluoric acid. [Diagram 2] Electron microscope photograph of Comparative Example 1 after application of hydrofluoric acid. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] [Definition] In this specification, unless otherwise specifically stated, the definitions and examples set forth in this paragraph shall be followed. The singular includes the plural, and "a" or "the" means "at least one." An element of a concept may be expressed by a plurality of species, and when an amount thereof (e.g., mass % or mole %) is stated, the amount refers to the sum of the plurality of species. "And / or" includes all combinations of the elements as well as its use alone. When a numerical range is indicated using "~" or "-", it includes both endpoints and the units are the same. For example, 5 to 25 mol % means 5 mol % or more and 25 mol % or less. Alkyl means a group obtained by removing one arbitrary hydrogen from a linear, branched or cyclic saturated hydrocarbon, and includes linear alkyl, branched alkyl and cyclic alkyl, and optionally includes a linear or branched alkyl as a side chain in a cyclic structure. Aryl means a group obtained by removing one arbitrary hydrogen from an aromatic hydrocarbon. "C x-y ", "C x ~C y " and "C x " refers to the number of carbons in a molecule or substituent. For example, C 1-6 Alkyl refers to an alkyl chain having from 1 to 6 carbons (methyl, ethyl, propyl, butyl, pentyl, hexyl, etc.). When a polymer has multiple types of repeating units, these repeating units are copolymerized. These copolymerizations may be alternating copolymerization, random copolymerization, block copolymerization, graft copolymerization, or a mixture of these. When polymers or resins are shown by structural formulas, the n or m in parentheses indicates the number of repeats. Temperature is measured in degrees Celsius. For example, 20 degrees means 20 degrees Celsius. The wavelength refers to the peak wavelength at which the light emission intensity is maximum. The additive refers to a compound having that function (for example, in the case of a base generator, it is a compound that generates a base). The compound may be dissolved or dispersed in a solvent and added to the composition. In one embodiment of the present invention, such a solvent is preferably contained in the composition of the present invention as a solvent or other component.

[0011] Hereinafter, an embodiment of the present invention will be described in detail.

[0012] <Method for producing silicon nitride film> A method for producing a silicon nitride film on a substrate having grooves according to the present invention comprises the following steps. (a) applying a silicon nitride based composition to a substrate having a groove thereon to form a composition layer; (b) irradiating the composition layer with light having a wavelength of 200 to 229 nm; and (c) heating the substrate in a non-oxidizing atmosphere.

[0013] Process (a) Step (a) is a step of applying a silicon nitride based composition to a substrate having a groove to form a composition layer. In the present invention, the substrate may be a single layer or a laminate. The shape of the groove is not particularly limited, but in the present invention, since it is characterized in that it can easily penetrate into narrow grooves and form a uniform silicon nitride film even inside the groove, a substrate having grooves or holes with a high aspect ratio is preferred. Here, the shape of the groove is not particularly limited, and the cross section may be any shape such as a rectangle, a forward tapered shape, a reverse tapered shape, a curved shape, etc. In addition, both ends of the groove may be open or closed. The depth of the groove is preferably 150 to 500 nm, and more preferably 180 to 500 nm. In one embodiment of the present invention, for grooves deeper than 500 nm, steps (a) to (c) may be performed once, and then steps (a) to (c) may be performed again to form a silicon nitride film. The ratio of the groove depth to the groove width, ie, the aspect ratio, is preferably 10-100, and more preferably 15-50.

[0014] Examples of substrates having grooves include substrates for electronic devices equipped with transistor elements, bit lines, capacitors, etc. The manufacture of such electronic devices may include a through-hole formation process for forming holes that vertically penetrate the filling material of the fine grooves, following a process for forming an insulating film called PMD between a transistor element and a bit line, between a transistor element and a capacitor, between a bit line and a capacitor, or between a capacitor and a metal wiring, an insulating film called IMD between a plurality of metal wirings, or filling an isolation groove.

[0015] The silicon nitride composition is applied to the grooves of the substrate by any method, including, but not limited to, conventional coating methods such as spin coating, dipping, spraying, transfer coating, and slit coating. Preferred silicon nitride compositions are described below. A composition layer is formed by applying the silicon nitride composition, and at this time, a drying step such as spin drying, reduced pressure, pre-baking, etc. may be carried out as necessary. In a preferred embodiment, the method further comprises a step (pre-baking) of heating the substrate on which the composition layer has been formed at 70 to 300°C, preferably 75 to 250°C, prior to the step (b).

[0016] Process (b) The step (b) is a step of irradiating the composition layer with light having a wavelength of 200 to 229 nm. The wavelength of the irradiated light is preferably 200 to 226 nm. In a preferred embodiment of the present invention, a KrCl excimer lamp that emits ultraviolet light with a peak wavelength of 222 nm is used for the light irradiation. The illuminance is not particularly limited, but is preferably 2 to 80 mW / cm. 2 and more preferably 4 to 50 mW / cm 2 The irradiation dose is preferably 4 to 100 J / cm. 2 and more preferably 7 to 80 J / cm 2 It is. During light irradiation, the substrate may be heated, but is preferably heated to 200° C. or less, more preferably 100° C. or less, and even more preferably not heated. The atmosphere during light irradiation is not particularly limited, but is preferably a non-oxidizing atmosphere. It is believed that the light irradiation in this process causes condensation between polymers, resulting in a polymer with a high molecular weight.

[0017] Process (c) Step (c) is a step of heating the light-irradiated substrate in a non-oxidizing atmosphere. The heating temperature in this step is preferably 400 to 1,200° C., more preferably 400 to 1,100° C. The heating time is preferably 1 minute to 10 hours, more preferably 1 to 180 minutes. The heating atmosphere is a non-oxidizing atmosphere, which means an atmosphere with an oxygen concentration of 1% or less and a dew point of -20°C or less. The atmosphere is preferably N2, Ar, He, Ne, H2, or a mixed gas atmosphere of two or more of these, and more preferably N2.

[0018] After step (c), the composition layer becomes a silicon nitride film. The silicon nitride film refers to a film containing nitrogen atoms and silicon atoms, in which the ratio of the number of nitrogen atoms to the number of silicon atoms (N / Si) is 0.68 to 1.1, preferably 0.70 to 1.0, and may contain other atoms such as carbon, hydrogen, and oxygen, and also includes a silicon carbonitrogenous film.

[0019] The refractive index of the silicon nitride film with respect to light having a wavelength of 633 nm is 1.70 to 2.40, preferably 1.76 to 2.20, and more preferably 1.78 to 2.20.

[0020] According to the method of the present invention, a substrate having a silicon nitride film in a groove has a uniform and dense silicon nitride film formed throughout the groove. In particular, a uniform and dense film quality is achieved even at the bottom of the groove. This provides high resistance to chemicals, particularly to hydrofluoric acid.

[0021] The method for producing an electronic device according to the present invention comprises the method described above. The electronic device is preferably a semiconductor device, a solar cell chip, an organic light emitting diode, an inorganic light emitting diode, and more preferably a semiconductor device.

[0022] [Silicon nitride composition] The silicon nitride composition (hereinafter sometimes simply referred to as the composition) used in the present invention is not particularly limited as long as it contains components capable of forming a silicon nitride film. The viscosity of the silicon nitride composition, as measured at 25° C. with a capillary viscometer, is preferably 0.55 to 1.80 mPa·s, more preferably 0.55 to 1.70 mPa·s, and even more preferably 0.57 to 1.60 mPa·s.

[0023] (Silicon-containing polymer) The composition according to the present invention preferably comprises a silicon-containing polymer selected from polysilazanes, polycarbosilazanes, and mixtures thereof.

[0024] The mass average molecular weight of the silicon-containing polymer is preferably 1,000 to 30,000, more preferably 2,000 to 30,000, and further preferably 3,000 to 30,000. In the present invention, the mass average molecular weight is a weight average molecular weight converted into polystyrene and can be measured by gel permeation chromatography using polystyrene as a standard. The same applies to other polymers.

[0025] The content of the silicon-containing polymer is preferably large in order to prevent the vaporization of low molecular weight components and suppress the volume change when filling fine grooves, while it is preferable that the viscosity is low in order to obtain good coating properties and to fill trenches with high aspect ratios well. For these reasons, the content of the silicon-containing polymer is preferably 0.1 to 40 mass%, more preferably 0.2 to 30 mass%, based on the total mass of the composition. Without being bound by theory, the content of the silicon-containing polymer in the above range can suppress the decrease in density of the bottom of the groove due to the shrinkage of the coating film formed on the groove when heated, and is effective in increasing the density of the silicon nitride film at the bottom of the groove.

[0026] (Polysilazane) The structure of the polysilazane used in the present invention is not particularly limited, and may be selected from any suitable ones depending on the purpose. The polysilazane has a Si-N bond as the main skeleton, and may be either an inorganic compound or an organic compound, and may be linear, branched, or have a cyclic structure in part.

[0027] Preferably, the polysilazane contains 20 or more, preferably 20 to 350, repeating units selected from the group consisting of the following formulas (1-i) to (1-vi). In this case, it is preferable that each repeating unit is directly bonded to the other repeating units than (1-i) to (1-vi) without being connected via any other repeating units than (1-i) to (1-vi). [ka] (In the formula, R 1a ~R 1i are each independently hydrogen or C 1-4 (It is alkyl)

[0028] More preferably, the polysilazane used in the present invention is perhydropolysilazane (hereinafter referred to as PHPS). PHPS is a silicon-containing polymer that contains Si-N bonds as repeating units and is composed only of Si, N, and H. In this PHPS, all elements bonded to Si and N, except for the Si-N bonds, are H, and other elements such as carbon and oxygen are not substantially included. The simplest structure of perhydropolysilazane is a chain structure having the following repeating units. [ka]

[0029] The structure of PHPS is not limited, and it can have various structures other than those exemplified above, so long as it is a silicon-containing polymer that contains Si-N bonds as repeating units and is composed only of Si, N, and H. PHPS preferably has a cyclic structure or a crosslinked structure, particularly preferably a crosslinked structure.

[0030] From the viewpoints of solubility in a solvent and reactivity, the mass average molecular weight of the polysilazane is preferably from 1,000 to 30,000, more preferably from 2,000 to 25,000, and even more preferably from 3,000 to 20,000.

[0031] (Polycarbosilazane) The structure of the polycarbosilazane used in the present invention is not particularly limited and can be selected from any structure depending on the purpose. The polycarbosilazane has a C-Si-N structure as the main skeleton, and preferably contains a repeating unit represented by the following formula (2-i) and a repeating unit represented by the following formula (2-ii). [ka] Where: R 2a , R 2b , and R 2c are each independently a single bond, hydrogen, or C 1-4 It is alkyl, preferably a single bond or hydrogen. R 2d , R 2e and R 2f are each independently a single bond or hydrogen. However, R 2a , R 2b , R 2d and R 2e When is a single bond, it bonds to N in another repeating unit, and R 2c and R 2f When is a single bond, it bonds to Si contained in another repeating unit. n and m each independently represent 1 to 3, preferably 1 or 2, and more preferably 1. The polycarbosilazane is preferably polyperhydrocarbosilazane. The polyperhydrocarbosilazane is represented by the formula R 2a , R 2b , and R 2c is a single bond or hydrogen, and (CH2) in formula (2-i) n and (CH2) m Additionally, it does not have any hydrocarbon groups. The end groups of the polycarbosilazane are preferably -SiH3.

[0032] The polycarbosilazane according to the present invention preferably consists essentially of repeating units represented by formula (2-i) and repeating units represented by formula (2-ii). In the present invention, "substantially" means that 95% by mass or more of all the constituent units contained in the polycarbosilazane are repeating units represented by formula (2-i) and repeating units represented by formula (2-ii). More preferably, the polycarbosilazane does not contain any repeating units other than the repeating units represented by formula (2-i) and the repeating units represented by formula (2-ii).

[0033] The mass average molecular weight of the polycarbosilazane according to the present invention is preferably 1,000 to 25,000, and more preferably 2,000 to 20,000.

[0034] (solvent) The composition used in the present invention may contain a solvent. The solvent is selected from those that uniformly dissolve or disperse each component contained in the composition. Specifically, the solvent may be, for example, ethylene glycol monoalkyl ethers such as ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monopropyl ether, and ethylene glycol monobutyl ether; diethylene glycol dialkyl ethers such as diethylene glycol dimethyl ether, diethylene glycol diethyl ether, diethylene glycol dipropyl ether, and diethylene glycol dibutyl ether; ethylene glycol alkyl ether acetates such as methyl cellosolve acetate and ethyl cellosolve acetate; propylene glycol monomethyl ether (PGME), propylene glycol monoethyl ether, and the like; Examples of the alkyl ether include glycol monoalkyl ethers, propylene glycol alkyl ether acetates such as propylene glycol monomethyl ether acetate (PGMEA), propylene glycol monoethyl ether acetate, and propylene glycol monopropyl ether acetate, aromatic hydrocarbons such as benzene, toluene, xylene, and mesitylene, ethers such as propylene glycol dimethyl ether, dipropyl ether, dibutyl ether, and anisole, ketones such as methyl ethyl ketone, acetone, methyl amyl ketone, methyl isobutyl ketone, and cyclohexanone, alcohols such as isopropanol and propanediol, and alicyclic hydrocarbons such as cyclooctane and decalin. Xylene, dibutyl ether, and propylene glycol dimethyl ether are preferred. These solvents may be used alone or in combination of two or more. The content of the solvent is preferably 60 to 99.9 mass %, more preferably 70.0 to 99.8 mass %, based on the total mass of the composition.

[0035] The composition used in the present invention can be combined with further optional components as necessary. The optional components include, for example, surfactants. The content of the optional components, excluding the solvent, in the entire composition is preferably 10% by mass or less, more preferably 5% by mass or less, and even more preferably 1% by mass or less, based on the total mass. In one embodiment of the present invention, the composition used in the present invention does not contain any components other than the silicon-containing polymer and the solvent.

[0036] [Example] The present invention will now be described with reference to examples, which are for illustrative purposes only and are not intended to limit the scope of the present invention.

[0037] [Synthesis Example 1: Synthesis of Polysilazane 1] After replacing the inside of a 10L reaction vessel equipped with a cooling condenser, a mechanical stirrer and a temperature control device with dry nitrogen, 7,500 ml of dry pyridine is added to the reaction vessel and cooled to 0°C. Next, 500 g of dichlorosilane is added to produce a white solid adduct (SiH2Cl2·2C5H5N). After confirming that the reaction mixture has reached 0°C or lower, 350 g of ammonia is slowly blown into it while stirring. After continuing to stir for 30 minutes, dry nitrogen is blown into the liquid layer for 30 minutes to remove excess ammonia. The resulting slurry-like product is pressure-filtered using a 0.2 μm Teflon (registered trademark) filter under a dry nitrogen atmosphere to obtain 6,000 ml of filtrate. Pyridine is distilled off using an evaporator, and dibutyl ether is added to obtain a 20.4 mass% dibutyl ether solution of polysilazane 1. The mixture is filtered using a 0.05 μm Teflon (registered trademark) filter to obtain a silicon nitride composition. The weight average molecular weight (hereinafter referred to as Mw) of the obtained polysilazane 1 was measured by gel permeation chromatography (GPC) and was found to be 1,580 in terms of polystyrene.

[0038] GPC is performed using an allianceTM e2695 high-speed GPC system (manufactured by Nihon Waters K.K.) and a Super Multipore HZ-N GPC column (manufactured by Tosoh Corporation). Measurements are performed using monodisperse polystyrene as a standard sample, chloroform as a developing solvent, and under measurement conditions of a flow rate of 0.6 milliliters / minute and a column temperature of 40°C, and the mass average molecular weight is calculated as the relative molecular weight to the standard sample. The same measurement method is applied to Mw below.

[0039] [Synthesis of intermediate (A)] After replacing the inside of a 10L reaction vessel equipped with a cooling condenser, a mechanical stirrer and a temperature control device with dry nitrogen, 7,500 ml of dry pyridine is added to the reaction vessel and cooled to -3°C. Next, 500 g of dichlorosilane is added to produce a white solid adduct (SiH2Cl2·2C5H5N). After confirming that the reaction mixture has reached -3°C or lower, 350 g of ammonia is slowly blown into it while stirring. After continuing to stir for 30 minutes, dry nitrogen is blown into the liquid layer for 30 minutes to remove excess ammonia. The resulting slurry-like product is pressure-filtered using a 0.2 μm Teflon (registered trademark) filter under a dry nitrogen atmosphere to obtain 6,000 ml of filtrate. Pyridine is distilled off using an evaporator, and xylene is added to obtain a xylene solution of 39.8 mass% polysilazane. The Mw of the obtained polysilazane is 1,220. The polysilazane obtained by this recipe is hereinafter referred to as intermediate (A).

[0040] [Synthesis Example 2: Synthesis of Polysilazane 2] After replacing the inside of a 10 L reaction vessel equipped with a cooling condenser, a mechanical stirrer and a temperature control device with dry nitrogen, 4700 g of dry pyridine, 150 g of dry xylene and 1650 g of the 39.8 mass% intermediate (A) obtained above are added, and the mixture is stirred to be homogenous while bubbling with nitrogen gas at 0.5 NL / min. The mixture is then subjected to a modification reaction at 100°C for 10.5 hours to obtain polysilazane 2. Polysilazane 2 has an Mw of 3,200. After distilling off the xylene, dibutyl ether is added to obtain a 19.8 mass% dibutyl ether solution of polysilazane 2. The mixture is filtered using a 0.05 μm Teflon (registered trademark) filter to obtain a silicon nitride composition. The relative value (R(SiH 1,2 ) is 0.245, and the relative value of the amount of NH based on the aromatic ring hydrogen of xylene (R(NH)) is 0.058.

[0041] [Synthesis Example 3: Synthesis of Polysilazane 3] The synthesis was carried out under the modified reaction conditions of 110° C. for 10.5 hours in comparison with Synthesis Example 2, to obtain a 19.2 mass% dibutyl ether solution of polysilazane 3. The solution was filtered using a 0.05 μm Teflon (registered trademark) filter to obtain a silicon nitride composition. Polysilazane 3 had an Mw of 8,600 and an R(SiH 1,2 ) is 0.198 and R(NH) is 0.043.

[0042] [Synthesis Example 4: Synthesis of polycarbosilazane] After replacing the inside of a 1L reaction vessel equipped with a cooling condenser, a mechanical stirrer and a temperature control device with dry nitrogen, 500 ml of dry pyridine is added to the reaction vessel and cooled to -3°C. Then, 12.3 g of dichlorosilane and 2.75 g of 1,1,3,3-tetrachloro-1,3-disilacyclobutane are added. After confirming that the reaction mixture has reached 0°C or lower, 11.3 g of ammonia is slowly blown into it while stirring. After continuing to stir for 30 minutes, dry nitrogen is blown into the liquid layer for 30 minutes to remove excess ammonia. The obtained slurry-like product is pressure-filtered using a 0.2 μm Teflon (registered trademark) filter under a dry nitrogen atmosphere to obtain 400 ml of filtrate. After distilling off the pyridine from the filtrate, xylene is added to obtain a xylene solution of polycarbosilazane with a concentration of 19.2 mass%. Filtration is performed using a 0.05 μm Teflon (registered trademark) filter to obtain a silicon nitride composition. Polycarbosilazane's Mw is 5,400.

[0043] [Example 1] The silicon nitride composition of polysilazane 1 obtained in Synthesis Example 1 is dropped onto a silicon wafer (8 inches) on which a pattern (groove with a width of 20 nm, a length of 2 mm, and a depth of 500 nm) is formed, and spin-coated at a rotation speed of 1000 rpm to form a coating film. The coating film is pre-baked on a hot plate under conditions of 80°C / N2 / 3 minutes to dry. An excimer 222 nm irradiation unit MEUTA-1-200-222-M (MDCOM Co., Ltd.) is used to perform irradiation at 222 nm and illuminance of 50 mW / cm. 2 The film is irradiated with light of 450°C for 30 minutes. The irradiated film is annealed under the conditions of 450°C / N2 / 60 minutes to obtain a silicon nitride film. -1 A peak was observed at 1.78, and the Rutherford backscattering analysis revealed that the N / Si ratio was 0.78 and the refractive index was 1.78, indicating that the resulting film was a silicon nitride film. When the bottom of the groove was evaluated for resistance to hydrofluoric acid, no seams or voids were observed.

[0044] [Examples 2-6 and Comparative Examples 1 and 2] A silicon nitride film is obtained by the same procedure as in Example 1, except that the silicon nitride composition, the wavelength of the irradiated light, and the annealing conditions are changed as shown in Tables 1-1 and 1-2. The evaluation results are summarized in Tables 1-1 and 1-2. [Table 1-1] [Table 1-2]

[0045] [Refractive index] The refractive index is measured at a wavelength of 633 nm at room temperature in the atmosphere using a spectroscopic ellipsometer M-2000V (manufactured by JA Woollam Co., Ltd.).

[0046] [Fourier transform infrared spectroscopy] Measurements are performed at room temperature by a transmission method using a Fourier transform infrared spectrophotometer FTIR-6600FV (manufactured by JASCO Corporation).

[0047] [Rutherford backscattering analysis] The N / Si ratio is measured by elemental analysis using a Pelletron 3SDH (manufactured by National Electrostatics Corporation) by Rutherford backscattering spectrometry.

[0048] [Resistance of the groove bottom to hydrofluoric acid] The annealed pattern substrate is split perpendicularly to the groove direction, immersed in an aqueous solution containing 0.05% by mass of hydrofluoric acid for 30 seconds, washed with pure water, dried, and then observed under a scanning electron microscope Regulus8230 (manufactured by Hitachi High-Tech Fielding) and evaluated according to the following criteria. Electron microscope photographs of the grooves observed in Example 3 and Comparative Example 1 are shown in Figures 1 and 2, respectively. In Figure 1, no seams or voids are observed, and it can be seen that a dense film has been formed in the grooves. In Figure 2, it can be seen that the grooves are not resistant to hydrofluoric acid and are hollow. A: No seams or voids are observed at the bottom of the groove. B: A seam or void is observed at the bottom of the groove. C: Seams or voids are significantly observed at the bottom of the groove.

Claims

1. The following steps: (a) Applying a silicon nitride composition to a substrate having grooves to form a composition layer; (b) Irradiating the composition layer with light of a wavelength of 200 to 229 nm; and (c) Heating the substrate in a non-oxidizing atmosphere. A method for producing a silicon nitride film on a substrate having grooves comprising, A method wherein the silicon nitride film has a refractive index of 1.70 to 2.40 for light with a wavelength of 633 nm.

2. The method according to claim 1, wherein the depth of the groove is 150 to 500 nm.

3. The method according to claim 1 or 2, wherein the silicon nitride composition comprises a silicon-containing polymer selected from polysilazanes, polycarbosilazanes, and mixtures thereof.

4. The method according to claim 3, wherein the mass-average molecular weight of the silicon-containing polymer is 1,000 to 30,000.

5. The method according to claim 1 or 2, wherein the silicon nitride composition further comprises a solvent.

6. The method according to claim 3, wherein the silicon nitride composition further comprises a solvent, and the content of the silicon-containing polymer is 0.1 to 40% by mass based on the total amount of the silicon nitride composition.

7. The method according to claim 1 or 2, wherein the viscosity of the silicon nitride composition, as measured by a capillary viscometer at 25°C, is 0.55 to 1.80 mPa·s.

8. The method according to claim 1 or 2, further comprising the step of heating the substrate on which the composition layer is formed to 70 to 300°C before step (b).

9. The method according to claim 1 or 2, wherein the heating in step (c) is carried out at 400 to 1,200°C.

10. A substrate having a silicon nitride film in the grooves, obtained by the method described in claim 1 or 2.

11. A method for manufacturing an electronic device comprising the method according to claim 1 or 2.

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