JPH11105187A - Method for forming high purity siliceous film and high purity siliceous film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To avoid to incorporate substantially SiOH bondings in a high purity siliceous film by a method wherein after an aluminum-contg. polysilazane film is formed on the surface of a substrate, preliminary heating is performed at a specified temp. in an atmosphere contg. steam and then, it is fired at a specified temp. in an atmosphere contg. oxygen. SOLUTION: After an aluminum-contg. polysilazane film is formed on the surface of a substrate, preliminary heating is performed at 50-500 deg.C in an atmosphere contg. steam and then, it is fired at 500 deg.C or higher in an atmosphere contg. oxygen. The polysilazane has a silazane structure of formula in the molecular chain. In the formula, R<1> , R<2> and R<3> are each hydrogen atom, a hydrocarbon group, a hydrocarbon group-contg. silyl group, a hydrocarbon group-contg. amino group or a hydrocarbon oxy group and at least one of R<1> and R<2> is hydrogen atom. The polysilazane contg. the silazane structure of the formula in the molecular chain is a linear, cyclic or crosslinked polysilazane and it can be a mixture thereof.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to a method for forming a siliceous film.

[0002]

2. Description of the Related Art When a polysilazane thin film is fired in the air, it is converted into silica, but it is difficult to convert it to an ideal high-purity SiO ₂ film. As a method of accelerating the conversion reaction from polysilazane to silica, addition of a catalyst to polysilazane, introduction of steam into a firing atmosphere, or a combination thereof has already been proposed (Japanese Patent Application No. 06-29918).
8, Japanese Patent Application No. 06-306329, Japanese Patent Application No. 07-1969.
86, Japanese Patent Application No. 19-031333, Japanese Patent Application No. 09-157
544 etc.). Since these are methods for accelerating the reaction between polysilazane and water vapor mainly by the action of a catalyst, hydrogen and nitrogen components in polysilazane can be effectively reduced,
Essentially, water-derived Si-OH groups remain. For this reason,
In these methods, although a dense siliceous film can be obtained at a low temperature, it has been difficult to convert to a high-purity silica having a density exceeding 2.2.

[0003]

SUMMARY OF THE INVENTION An object of the present invention is to provide a method for forming a high-purity siliceous film substantially containing no SiOH bond.

[0004]

Means for Solving the Problems The present inventors have made intensive studies to solve the above-mentioned problems, and as a result, have completed the present invention. That is, according to the present invention, after an aluminum-containing polysilazane film is formed on a substrate surface, the film is preheated at 50 to 500 ° C. in an atmosphere containing water vapor, and then heated to a temperature of 500 ° C. or more in an atmosphere containing oxygen. And a method for forming a high-purity siliceous film characterized by firing. Further, according to the present invention, after forming an aluminum-containing polysilazane film on a substrate surface, the film is preheated at 50 to 500 ° C. in an atmosphere containing water vapor, and then heated to a temperature of 500 ° C. or more in an atmosphere containing water vapor. And a method for forming a high-purity siliceous film characterized by firing.

[0005]

BEST MODE FOR CARRYING OUT THE INVENTION The siliceous film according to the present invention is formed from a polysilazane film containing aluminum. Hereinafter, the method for forming the siliceous film will be described in detail. The polysilazane used as a material for forming the siliceous film has a silazane structure represented by the following general formula (1) in its molecular chain.

Embedded image In the above formula, R ¹ , R ² and R ³ are a hydrogen atom, a hydrocarbon group,
It represents a hydrocarbon group-containing silyl group, a hydrocarbon group-containing amino group or a hydrocarbon oxy group. At least one of R ¹ and R ² represents a hydrogen atom. A substituent may be bonded to the hydrocarbon group, and such a substituent may be chlorine, bromine,
Halogen such as fluorine, alkoxy group, alkoxycarbonyl group, amino group and the like are included. The hydrocarbon group includes an aliphatic hydrocarbon group and an aromatic hydrocarbon group, and the aliphatic hydrocarbon group includes a chain group and a cyclic group. Examples of such a hydrocarbon group include an alkyl group, an alkenyl group, a cycloalkyl group, a cycloalkenyl group, an aryl group, and an arylalkyl group. The number of carbon atoms in these hydrocarbon groups is not particularly limited, but is usually 20 or less, preferably 10 or less.
In the present invention, in particular, it has 1 to 8 carbon atoms, preferably 1 carbon atom.
It is preferably an alkyl group of from 4 to 4. Among the hydrocarbon-containing silyl groups, preferred hydrocarbon groups are those having 1 to 2 carbon atoms.
0, preferably 1 to 6 alkyl groups. The number of the hydrocarbon groups bonded to Si is 1 to 3. In a hydrocarbon amino group or a hydrocarbon oxy group, the number of carbon atoms in the hydrocarbon group is 1 to 3.

The polysilazane having a silazane structure represented by the above general formula (1) in a molecular chain can be a polysilazane having a chain, cyclic or bridged structure, or a mixture thereof. . Its number average molecular weight is 100 to 100,000, preferably 300 to 1000.
0. Such polysilazanes include not only ordinary perhydropolysilazanes and organopolysilazanes but also modified products thereof. The modified polysilazane in this case includes platinum or palladium-containing polysilazane, alcohol-containing polysilazane, HMDS (hexamethyldisilazane)
Polysilazane, amine-containing polysilazane, organic acid-containing polysilazane, and the like. These modified polysilazanes are described, for example, in JP-A-9-31333, JP-A-8-176512, and JP-A-8-176.
511 and JP-A-5-345826.

[0007] The siliceous film according to the present invention uses an organic solvent solution containing a polysilazane containing an aluminum compound as a coating composition (coating solution).
The composition is formed by applying and drying the coating composition on a required substrate surface, followed by heating and baking.

The aluminum contained in the polysilazane may be any aluminum compound that is soluble in an organic solvent. Such soluble aluminum compounds include alkoxides, chelates, organoaluminum,
Halides and the like.

The alkoxide of aluminum can be represented by the following general formula (2).

Embedded image

In the above formula, R ⁴ , R ⁵ and R ⁶ represent a hydrocarbon group. The hydrocarbon group in this case includes an aliphatic hydrocarbon group and an aromatic hydrocarbon group. The aliphatic hydrocarbon group includes a chain and a cyclic group. Examples of the aliphatic hydrocarbon group include an alkyl group, an alkenyl group, a cycloalkyl group, and a cycloalkenyl group. The number of carbon atoms is not particularly limited, but is usually 20 or less, preferably 8 or less. Specific examples of such an aliphatic hydrocarbon group include methyl, ethyl, propyl, butyl, pentyl, octyl, dodecyl, octadecyl, dodecenyl, cyclohexyl, cyclohexenyl and the like. The aromatic hydrocarbon group includes an aryl group and an arylalkyl group. Specific examples of such an aromatic hydrocarbon group include phenyl, tolyl, xylyl, naphthyl, benzyl, phenethyl, naphthylmethyl and the like.

Examples of the chelating compound of aluminum include aluminum acetylacetonate, aluminum ethyl acetoacetate and the like. As the organic aluminum, those represented by the following general formula (3) can be shown.

Embedded image In the above formula, R ⁴ , R ⁵ and R ⁶ represent a hydrocarbon group. As such a hydrocarbon group, those shown in connection with the general formula (2) can be shown.

The aluminum halide may be represented by the following general formula (4).

Embedded image AlX ₃ (4) In the formula, X is a halogen. Halogen in this case includes chlorine, bromine, iodine and fluorine. The organic solvent-soluble aluminum compounds described above can be used alone or in the form of a mixture.

The amount of the aluminum compound to be added is 0.001 to 10% by weight, preferably 0.03% by weight, based on the polysilazane, in terms of aluminum metal, although it depends on the kind of the aluminum compound.
It is 1 to 10% by weight, more preferably 0.1 to 1% by weight. If the addition amount of the aluminum compound is more than the above range, the density and homogeneity of the obtained siliceous film are undesirably reduced. On the other hand, if it is less than the above range, the effect of adding the aluminum compound becomes insufficient.

In order to obtain aluminum-containing polysilazane, polysilazane and an aluminum compound are stirred and mixed in an organic solvent. The stirring and mixing in this case is 0 to
200 ° C, preferably at a temperature of 0 to 100 ° C and normal pressure to 1
It is carried out under a pressure of 0 kg / cm ² G, preferably at normal pressure. The polysilazane concentration in the organic solvent is 0.1 to
It is 80% by weight, preferably 5 to 50% by weight. As the organic solvent for dissolving the polysilazane and the aluminum compound, an inert organic solvent having no active hydrogen is used. Examples of such an organic solvent include aromatic hydrocarbon solvents such as benzene, toluene, xylene, ethylbenzene, diethylbenzene, trimethylbenzene, and triethylbenzene; cyclohexane, cyclohexene, decapidronaphthalene, ethylcyclohexane, methylcyclohexane, and p-menthine. And alicyclic hydrocarbon solvents such as dipentene (limonene); ether solvents such as dipropyl ether and dibutyl ether; ketone solvents such as methyl isobutyl ketone.

[0015] By stirring and mixing the polysilazane and the aluminum compound in the organic solvent, an aluminum-containing polysilazane mixed or added with the aluminum compound is produced. The aluminum-containing polysilazane in this case is
Usually, it does not reach the structure of aluminopolysilazane in which aluminum and silicon are firmly bonded.
The organic solvent solution containing aluminum-containing polysilazane obtained as described above is used as it is or after adjusting the concentration of polysilazane, used as a coating composition, applied and dried on the substrate surface, and then heated. Thus, a siliceous film is formed on the substrate surface. in this case,
The thickness of the siliceous film formed on the substrate surface varies depending on the use of the substrate surface, but is usually 0.01 to 5 μm,
Preferably it is 0.1 to 2 μm. In particular, when used as a semiconductor interlayer insulating film, the thickness is 0.1 to 2 μm.

As a method for applying the coating composition containing the aluminum-containing polysilazane to the surface of the substrate, a conventionally known method, for example, a spin coating method, a dipping method, a spraying method, a transfer method and the like can be mentioned.

The heating for converting the aluminum-containing polysilazane film formed on the substrate surface into a siliceous film is performed as follows.
It is performed by two steps of a preheating step and a firing step. The preheating step is performed at 50 to 500 ° C., preferably at 10 ° C.
The heating is performed at 0 to 300 ° C., and an atmosphere containing water vapor such as air, humidified air, or humidified nitrogen gas is used as the heating atmosphere. The water vapor content in the atmosphere is 0.1 vol%
The above is preferably 0.5 vol% or more, and the upper limit is the dew point. The preheating time is from 10 seconds to 60 minutes, preferably from 0.5 minutes to 10 minutes. The firing step is 500 ° C
The above is preferably carried out at 600 ° C. or higher, and the upper limit of the firing temperature is usually 120 ° C. As the firing atmosphere, an oxygen-containing dry atmosphere or a steam-containing atmosphere is employed. As the oxygen-containing dry atmosphere, dry air,
Dry oxygen and the like, and the water vapor content thereof is 0.5 vol.
1% or less, preferably 0 to 0.05 vol%. Examples of the water vapor-containing atmosphere include air (air), humidified air (humidified air), and humidified nitrogen. The water vapor content is 0.1 vol% or more, preferably 0.5 vol% or more, and the upper limit thereof is Dew point. Baking time is 5 minutes to 10
Time, preferably 10 minutes to 3 hours. When converting the aluminum-containing polysilazane film into a siliceous film in a water vapor-containing atmosphere, the preheating step and the firing step can be performed continuously.

By the heating of the aluminum-containing polysilazane film, SiH and SiR (R:
The bond between the (hydrocarbon group) and SiN is oxidized and converted into a SiO bond, forming a siliceous film. In this case, Si
-OH bonds are not substantially formed. Generally, when heating a polysilazane film, its SiH, SiR and SiN
The bond is usually oxidized almost simultaneously, though depending on the firing conditions. This is confirmed by measuring the IR spectrum of the fired product, since the absorptions by SiH, SiR and SiN disappear almost simultaneously. On the other hand, according to the study of the present inventors, in the case of heating the aluminum-containing polysilazane film used in the present invention, SiH and S
It was confirmed that the oxidation of the SiN bond, ie, the reaction of substituting N for O, proceeded preferentially over the oxidation of the iR bond. Therefore, in the preheating step, the formed siliceous film contains SiO bonds formed by selectively oxidizing SiN bonds and unoxidized SiH and SiR bonds. A siliceous film can be obtained. When the siliceous film obtained in the preheating step is heated in the next firing step, the Si—H bonds and Si—R bonds present in the film are gradually oxidized and converted into SiO bonds. As a result, a high-purity SiO ₂ film is formed.

[0019] The properties of high-purity siliceous film according to the present invention, a density of 2.0~2.4g / cm ^3, preferably 2.3 g / cm ³ or more, its crack limiting film thickness 1.
It is 0 μm or more, preferably 1.5 μm or more and its internal stress is 3.0 × 10 ⁹ dyne / cm ² or less, preferably 2.0 × 10 ⁹ dyne / cm ² or less. Further, this siliceous film is a high-purity silica film substantially composed of only SiO ₂ , and the content of Si present as SiR (R: hydrogen or hydrocarbon) is reduced by the total number of Si atoms contained in the film. On the other hand, the content is 1 atomic% or less, and the content of Si present as Si-NR (R: hydrogen or hydrocarbon group) is 1 atomic% or less.

The siliceous film according to the present invention has a low density as described above, and its crack limit film thickness, that is,
There is an advantage that the maximum film thickness that can be formed without causing film cracking is as high as 1.5 μm or more. In the case of a conventional siliceous film, its crack limit film thickness is about 0.5 to 0.8 μm. Therefore, the siliceous film of the present invention shows a great technical effect as compared with the conventional siliceous film.

The method for forming a siliceous film according to the present invention can be carried out very easily, because the precursor, animinium-containing polysilazane, can be easily converted to siliceous by the catalytic action of aluminum. it can. In addition, in the case of the present invention, since the content of SiN bonds can be reduced to substantially zero% by the catalytic action of aluminum, the film is a very stable SiO ₂ film, It does not deteriorate when left in the air.

The siliceous film of the present invention can be advantageously used as an interlayer insulating film in a semiconductor device. In this case, the siliceous film is formed on a plane including the metal wiring or the metal wiring coated with the ceramic film. In the semiconductor device including the siliceous film of the present invention, the siliceous film has excellent insulating properties and the dielectric constant is small,
It has excellent electrical characteristics.

According to the present invention, a siliceous film can be formed on a solid surface of various materials such as metal, ceramics, and wood. According to the present invention, a metal substrate (silicon, SUS, tungsten, iron, copper, zinc, brass, aluminum, etc.) having a siliceous film formed on its surface, or a ceramic substrate (silica,
Alumina, magnesium oxide, titanium oxide, zinc oxide,
In addition to metal oxides such as tantalum oxide, metal nitrides such as silicon nitride, boron nitride, and titanium nitride, and silicon carbide are provided.

[0024]

Next, the present invention will be described in more detail by way of examples. In addition, the evaluation method of the physical property shown below about the siliceous film is as follows. (Film Density) The weight of a silicon wafer having a diameter of 4 inches and a thickness of 0.5 mm was measured with an electronic balance. After the polysilazane solution was formed into a film by a spin coating method, the film was converted into a siliceous film according to the methods of Examples and Comparative Examples, and the weight of the silicon wafer with the film was measured again by an electronic balance. The film weight was the difference between these. The film thickness was measured using a stylus-type film thickness measuring device (Dektak IIA, manufactured by Sloan) in the same manner as in the evaluation of the relative dielectric constant. The film density was calculated by the following equation. Film density [g / cm ³ ] = (film weight [g]) / (film thickness [μ
m]) / 0.008 (Internal stress) A warp of a silicon wafer having a diameter of 4 inches and a thickness of 0.5 mm was input to a laser internal stress meter FLX-2320 manufactured by Tencor. After forming a polysilazane solution on this silicon wafer by spin coating,
Converted to a siliceous membrane according to the methods of Examples and Comparative Examples,
After returning to room temperature (23 ° C.), the internal stress was measured with a laser internal stress meter FLX-2320 manufactured by Tencor. The film thickness was measured using a stylus-type film thickness measuring device (manufactured by Sloan,
Dektak IIA). (Crack Limit Film Thickness) A polysilazane solution was formed on a silicon wafer having a diameter of 4 inches and a thickness of 0.5 mm by spin coating, and then converted into a siliceous film according to the methods of Examples and Comparative Examples. By adjusting the polysilazane concentration of the polysilazane solution or the rotation speed of the spin coater,
Samples were prepared in which the film thickness was changed in a range from about 0.5 μm to about 3 μm. Microscopic observation of the fired thin film (× 120)
Then, the presence or absence of cracks was examined. The maximum film thickness without crack generation was defined as the crack limit film thickness.

Reference Example 1 [Synthesis of perhydropolysilazane] A gas blowing tube, a mechanical stirrer and a dewar condenser were attached to a four-necked flask having an inner volume of 2 L. After the inside of the reactor was replaced with dry nitrogen, 1500 ml of dry pyridine was put into a four-necked flask, and this was cooled with ice. Next, when 100 g of dichlorosilane was added, a white solid adduct (SiH ₂ Cl ₂ .2C ₅ H ₅ N) was formed. The reaction mixture was ice-cooled, and 70 g of ammonia was blown in while stirring. Subsequently, dry nitrogen was blown into the liquid layer for 30 minutes to remove excess ammonia. The resulting product was filtered under reduced pressure using a Buchner funnel under a dry nitrogen atmosphere.
200 ml were obtained. When pyridine was distilled off using an evaporator, 40 g of perhydropolysilazane was obtained. The number average molecular weight of perhydropolysilazane obtained GPC (eluent: CDC1 ₃₎ was measured by,
It was 800 in terms of polystyrene. When its IR (infrared absorption) spectrum is measured, a wave number (cm ^-1 ) of 335 is obtained.
Absorption based on NH near 0 and 1200: 2170
Based on Si-H: 1024-820 Si-N
It was confirmed to exhibit absorption based on -Si. FIG. 1 shows an IR spectrum of the perhydropolysilazane.

Comparative Example 1 20 g of perhydropolysilazane synthesized in Reference Example 1 was dissolved in 80 g of xylene to prepare a polysilazane solution.
And Advantech PTF with a filtration accuracy of 0.2 μm
The solution was filtered with an E syringe filter. This was applied on a silicon wafer having a diameter of 4 inches and a thickness of 0.5 mm using a spin coater (1500 rpm, 20 seconds) and dried at room temperature (10 minutes). Then, the silicon plate coated with polysilazane is placed in an air atmosphere (25 ° C., relative humidity 40).
%) On a hot plate at 150 ° C. and then 220 ° C. for 3 minutes each. Next, it was baked at 700 ° C. for 1 hour in a dry air atmosphere. Looking at the infrared absorption spectrum (IR spectrum) of the obtained siliceous film, the wave number (c
m ^-1 ) 1045 and 440 were found to be based on Si-O. Further, the absorption of unconverted polysilazane, that is, the absorption based on N—H at a wave number (cm ⁻¹ ) of 3380: 22
An absorption based on Si-H of 10 was observed. When the obtained film was evaluated, the density was 2.1 g / cm ³ , the internal stress was 2.8 × 10 ⁹ dyne / cm ² , and the crack limit film thickness was 1.8 μm. FIG. 2 shows an IR spectrum of the siliceous film.

Comparative Example 2 To 20 g of perhydropolysilazane synthesized in Reference Example 1, 2 g of tri-n-pentylamine was added and dissolved in 80 g of xylene to prepare a polysilazane solution. Then, the solution was filtered with a PTFE syringe filter manufactured by Advantech having a filtration accuracy of 0.2 μm. This was applied on a silicon wafer having a diameter of 4 inches and a thickness of 0.5 mm using a spin coater (1500 rpm, 20 seconds) and dried at room temperature (10 minutes). Then, the silicon plate coated with polysilazane is placed in an air atmosphere (25 ° C., relative humidity 40%) for 1 hour.
3 on a hot plate at 50 ° C and then at 220 ° C
Heated for minutes. Next, this was fired at 700 ° C. for 1 hour in a dry air atmosphere containing water vapor having a partial pressure of () kPa or less. Looking at the IR spectrum of the obtained siliceous film, absorptions based on Si—O having wave numbers (cm ⁻¹ ) of 1020 and 450 are mainly observed, and absorption of unconverted polysilazane, that is, wave number (cm ⁻¹ ) of 3380 Near NH-based absorption:
Absorption based on Si-H near 2210 and 860 were almost disappeared, but absorption based in H ₂ O absorption and 3000 to 3800 based on the SiO-H wavenumber 3800 was observed. When the obtained film was evaluated, the density was 2.1 g.
/ cm ³ , the internal stress was 2.0 × 10 ⁹ dyne / cm ² , and the critical crack thickness was 2.0 μm. FIG. 3 shows an IR spectrum of the siliceous film.

Example 1 25 g of perhydropolysilazane synthesized in Reference Example 1 was dissolved in 55 g of xylene to prepare a polysilazane solution.
Next, 0.1 g of tri (isopropoxy) aluminum was mixed with 20 g of xylene and dissolved well. Then, this was mixed with the polysilazane solution and poured into a four-necked flask equipped with a stirrer and a condenser having a capacity of 300 ml. The flask was heated to 60 ° C. while injecting dry nitrogen into the four-necked flask, held for 3 hours, and allowed to cool. Subsequently, the solution after cooling was filtered with a PTFE syringe filter manufactured by Advantech having a filtration accuracy of 0.2 μm. This was applied on a silicon wafer having a diameter of 4 inches and a thickness of 0.5 mm using a spin coater (1500 rpm, 20 seconds) and dried at room temperature (10 minutes). Then, the silicon plate coated with polysilazane is placed in an air atmosphere (25 ° C., relative humidity 40%) for 1 hour.
3 on a hot plate at 50 ° C and then at 220 ° C
Heated for minutes. Next, this is placed in a dry air atmosphere at 700 ° C.
For 1 hour. Looking at the IR spectrum of the obtained siliceous film, it can be seen that the wave number (cm ^-1 ) of
-O based absorption is predominant, with wave numbers 2250 and 85
Absorption based on Si-H near 0, N near wavenumber 3350
The absorption based on -H disappeared. Si with wave number around 3800
O-H is based on absorption and absorption based on of H ₂ O 3000 to 3800 was not observed. When the obtained film was evaluated, the density was 2.4 g / cm ³ , and the internal stress was 1.5 ×
10 ⁹ dyne / cm ² , crack limit film thickness is 1.5 μm
Met. FIG. 4 shows an IR spectrum of the siliceous film.

Example 2 25 g of perhydropolysilazane synthesized in Reference Example 1 was dissolved in 55 g of xylene to prepare a polysilazane solution.
Next, tri (ethyl acetoacetate) aluminum 0.1.
1 g was mixed with 20 g of xylene and dissolved well. This was mixed with the polysilazane solution. Subsequently, the mixture was filtered with a PTFE syringe filter manufactured by Advantech having a filtration accuracy of 0.2 μm. This is 4 inches in diameter and 0.5 inch thick
It was applied on a 1 mm silicon wafer using a spin coater (1500 rpm, 20 seconds) and dried at room temperature (10 minutes). Then, the silicon plate coated with polysilazane is placed in an air atmosphere (25 ° C., 40% relative humidity) for 150 minutes.
And then on a hot plate at 220 ° C. for 3 minutes each. Next, this was placed in a dry O ₂ atmosphere at 700 ° C. for 1 hour.
Fired for hours. Wave number (cm ^-1 ) 1065, and absorption based on Si-O at 460, Si-H at 2250 and 830
Only absorption based on the wave number (cm ^-1 ) 3350,
And 1200 absorption based on N—H almost disappeared. When the obtained film was evaluated, the density was 2.4 g.
/ Cm ³ , the internal stress is 1.2 × 10 ⁹ dyne / cm ² ,
The crack limit film thickness was 1.3 μm. FIG. 5 shows an IR spectrum of the siliceous film.

[0030]

The siliceous film of the present invention has a low density in addition to the chemical contact resistance, gas and ion barrier properties, abrasion resistance, heat resistance and flattening properties of a polysilazane-derived siliceous film. It has. In addition, the siliceous film of the present invention is characterized in that the film stress is small and the film thickness limit is high.
The siliceous film of the present invention can be used as an insulating film in the electric and electronic fields such as an undercoat film (insulating flattening film) of liquid crystal glass and a gas barrier film of film liquid crystal in addition to being used as an interlayer insulating film of a semiconductor. Can be Further, the method for forming a siliceous film of the present invention can be applied as a method of hard coating, heat resistant, acid resistant coating, stain resistant coating, water repellent coating or the like on a solid surface of metal, glass, plastic, wood or the like. further,
The present invention can also be applied as a gas barrier coating for a plastic film, an ultraviolet cut coating for glass, plastic, wood, and the like, a coloring coating method, and the like.

[Brief description of the drawings]

FIG. 1 shows an infrared absorption spectrum of perhydropolysilazane obtained in Reference Example 1.

FIG. 2 shows an infrared absorption spectrum of the siliceous film obtained in Comparative Example 1.

FIG. 3 shows an infrared absorption spectrum of the siliceous film obtained in Comparative Example 2.

FIG. 4 shows an infrared absorption spectrum of the siliceous film obtained in Example 1.

5 shows an infrared absorption spectrum of the siliceous film obtained in Example 2. FIG.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Rinko Aoki 1-3-1 Nishitsurugaoka, Oi-machi, Iruma-gun, Saitama Prefecture Inside the Tonen Research Institute (72) Inventor Yuji Tashiro 1 Nishi-Tsurugaoka, Oi-machi, Iruma-gun, Saitama Chome 3-1, Tonen Co., Ltd. (72) Inventor Toru Funayama 1-3-1, Nishitsurugaoka, Oimachi, Iruma-gun, Saitama Prefecture Tonen Co., Ltd.

Claims (3)

[Claims] After forming an aluminum-containing polysilazane film on a substrate surface, the film is formed in an atmosphere containing water vapor.
A method for forming a high-purity siliceous film, comprising preheating at a temperature of about 500 ° C. and then firing at a temperature of 500 ° C. or more in an atmosphere containing oxygen. 2. After forming an aluminum-containing polysilazane film on the surface of a substrate, the film is placed in an atmosphere containing water vapor.
A method for forming a high-purity siliceous film, comprising preheating at a temperature of about 500 ° C. and then firing at a temperature of 500 ° C. or more in an atmosphere containing steam. 3. A high-purity siliceous film comprising substantially only SiO ₂ obtained by the method according to claim 1.