JPH06128529A - Silica-film-forming coating fluid and base material coated therewith - Google Patents

Abstract

PURPOSE:To obtain silica-film-forming coating fluid capable of extensively leveling an uneven surface coated therewith by using a modified polysilazane obtd. by reacting a specific polysilazane with an alkanolamine. CONSTITUTION:At least one polysilazane having at least recurring units of formula I (wherein R1, R2 and R3 are each H or 1-8C alkyl) is mixed with an alkanolamine of formula II (wherein R4 is 1-8C alkyl; and n is 0 to 2) (e.g. monoethanolamine) in an org. solvent to effect a reaction between Si-N bonds of the polysilazane ad the alkanolamine to thereby yield a modified polysilazane product having Si-N bonds of the polysilazane cleaved. The reaction mixture is subjected to vacuum distillation or the like to remove thereform the solvent. The resulting resinous substance is dissolved in an org. solvent to prepare a silica-film-forming coating fluid having a desired solid content.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a coating liquid for forming a silica-based coating film, and more specifically, it has excellent chemical resistance such as adhesion to a surface to be coated, mechanical strength, and alkali resistance, and at the same time is dense and resistant to cracking. A coating liquid for forming a silica-based coating capable of forming an insulating film having excellent properties at a firing temperature of 350 ° C. or lower, and capable of highly flattening the unevenness of the surface to be coated, and a coating on which such a silica-based coating is formed With respect to the attached base material.

[0002]

BACKGROUND OF THE INVENTION Conventionally, silica coatings have been used in the following fields. 1) Semiconductor Device In a semiconductor device, an insulating film is provided between a semiconductor substrate and a metal wiring layer such as an aluminum wiring layer or in order to insulate between metal wiring layers. Further, in order to protect the PN junction semiconductor provided on the semiconductor substrate and various elements such as a capacitor element and a resistance element, these elements are covered with an insulating film.

When a metal wiring layer or the like is provided on the semiconductor substrate, the metal wiring layer or the like causes unevenness on the semiconductor substrate. Even if a metal wiring layer or the like is further formed on this uneven surface, disconnection may occur due to uneven steps. Therefore, in the insulating film formed between the semiconductor substrate and the metal wiring layer as described above, between the metal wiring layers, and the insulating film covering various elements, the metal wiring layer and various elements described above are generated. It is necessary to highly flatten the uneven surface.

In such a semiconductor device, a silica coating is used as an insulating film. 2) Liquid crystal display device In a liquid crystal display cell in a liquid crystal display device, a transparent electrode plate having an ITO film on a glass substrate is often used.
In a liquid crystal display cell using such a transparent electrode plate, during use, an alkaline component such as Na contained in the glass substrate migrates into the ITO film, or even ITO is used.
It may elute into the liquid crystal through the membrane. In order to prevent such an alkali component from migrating into the ITO film, a transparent electrode plate provided with an alkali passivation film between the glass substrate and the ITO film is also used.

Further, in order to improve the orientation of the liquid crystal material enclosed in the liquid crystal display cell, an orientation film is further formed on the transparent electrode of the transparent electrode plate, for example, the transparent electrode made of ITO film. There is. In a transparent electrode plate having such an alignment film, an insulating film may be provided between the transparent electrode and the alignment film in order to extend the life of the alignment film.

As a color liquid crystal display device, an electrode plate having a pixel electrode composed of a TFT (thin film transistor) or the like on a glass substrate, and a counter electrode plate on which a color filter and a transparent electrode are sequentially formed on a glass substrate. A matrix type color liquid crystal display device having a liquid crystal display cell having a liquid crystal layer filled between an electrode plate and a counter electrode plate is known.

In the liquid crystal display cell as described above, the pixel electrode projects from the electrode plate and the color filter projects from the counter electrode plate, and each electrode surface has a step. When there is a step on the electrode surface in this way, the cell gap becomes non-uniform, and the alignment of the liquid crystal material enclosed inside the liquid crystal display cell is disturbed or the displayed image is not displayed as compared with the case where the cell gap is uniform. There is a tendency that pixel unevenness such as color unevenness easily occurs.

Therefore, in JP-A-2-242226, a polyimide resin coating, an acrylic resin coating or a silica coating is formed on the pixel electrode of the electrode plate and the color filter of the counter electrode plate by a coating method. However, it has been proposed to flatten the uneven surface generated by the pixel electrode or the color filter.

In such a liquid crystal display device, a silica-based coating is used as the above-mentioned insulating film and alkali passivation film. 3) Photomask with phase shifter In order to form a high-resolution uneven pattern on the substrate by the lithographic method, a phase shifter that shifts the phase of the irradiation light is provided on the photomask, so that the uneven pattern formed on the substrate can be formed. There is a method for improving the resolution (Nikkei Microdevice No. 71, 52-58, (5), 199.
1).

A silica-based coating is used as such a phase shifter. A silica-based coating used in the above fields is generally formed on a substrate by a vapor deposition method such as a CVD method or a sputtering method or a coating method for forming a silica-based coating using a coating liquid for forming a silica-based coating. Has been formed.

However, the method of forming a silica-based coating by the vapor phase epitaxy is labor-intensive and requires a large facility, and when the silica-based coating is formed on the uneven surface, the silica-based coating is used. The uneven surface cannot be flattened.

On the other hand, since the above-mentioned problems can be solved by forming the silica-based coating by the coating method, in recent years, the silica-based coating is widely formed by the coating method.

Conventionally, when forming a silica-based coating film by such a coating method, a coating liquid for forming a silica-based coating film has been used in which the film-forming component is a condensation polymer of an alkoxysilane partial hydrolyzate. It was The polycondensation product of the partial alkoxysilane hydrolyzate is prepared by dissolving the alkoxysilane in an organic solvent such as alcohol, ketone, or ester, and then adding water or an acid or a base as a catalyst to the alkoxysilane to form the partial alkoxysilane. Hydrolysis,
Then, it can be obtained by polycondensation.

However, when a coating liquid for forming a silica-based coating film whose coating-forming component is a polycondensation product of an alkoxysilane partial hydrolyzate is applied onto a substrate and dried, alkoxysilane is contained in the resulting coating film. It remains. Therefore, when this coating is baked, organic groups such as alkyl groups and alkoxy groups contained in alkoxysilane molecules are decomposed in the coating during baking, and the decomposition of the organic groups causes pinholes and voids in the coating. It occurs and it is difficult to obtain a dense silica coating. Further, in the process in which the partial alkoxysilane hydrolyzate is condensed, silanol groups perform a dehydration reaction other than at the ends of the condensate, and the crosslinking of the condensate proceeds. Therefore, in the process of forming the silica-based coating, the shrinkage stress of the coating increases according to the degree of cross-linking of the condensate, and cracks occur in the coating. That is, it is difficult to obtain a silica-based coating having excellent crack resistance when using a coating liquid for forming a silica-based coating in which the coating-forming component is a polycondensation product of a partial hydrolyzed alkoxysilane.

On the other hand, in recent years, a coating solution for forming a silica-based coating film containing a cyclosilazane polymer or polysilazane has been proposed (see JP-A-62-88327, JP-A-1-203476, etc.). When a silica-based coating is formed using these coating solutions, the denseness and crack resistance of the silica-based coating can be improved to some extent.

However, the silica-based coating film formed from the coating liquid containing the above-mentioned cyclosilazane polymer or polysilazane has the following problems. The cyclosilazane polymer or polysilazane has a silazane skeleton represented by the following formula [I].

[0017]

[Chemical 2]

When the coating liquid thus obtained is coated on a substrate and the coating film obtained is heated and baked to obtain a silica-based coating film, the silazane skeleton is oxidized to give a siloxane skeleton.

[0019]

[Chemical 3]

Changes to. However, if the silazane skeleton remains in the silica-based coating obtained by not sufficiently performing the above-mentioned oxidation reaction, the denseness of the silica-based coating is decreased depending on the remaining amount of the silazane skeleton, or the silica-based coating is May absorb moisture. Further, when the silica-based coating film in which the silazane skeleton remains is baked, the silazane skeleton is decomposed and ammonia gas may be released.

The silica-based coating formed from the coating solution containing the cyclosilazane polymer or polysilazane as described above has insufficient denseness, and the ammonia gas released from the silica-based coating causes the above-mentioned In such a semiconductor device, the metal wiring layer may be corroded, and in the liquid crystal display device, the liquid crystal material in the liquid crystal display cell may be deteriorated. Furthermore, if the silazane skeleton remains in the silica-based coating, the phase shifter may be gradually deteriorated by the exposure light.

Therefore, when a silica-based coating is formed from a coating solution containing a cyclosilazane polymer or polysilazane, the coating is heated with oxygen plasma so that the silazane skeleton does not remain in the obtained silica-based coating. It was carried out under irradiation or in a steam atmosphere, and then the coating film was baked in air at a temperature of 500 ° C. or higher. Further, in the case of forming a silica-based coating from a coating solution containing cyclosilazane, it was not possible to obtain a silica-based coating containing almost no silazane skeleton if the coating was baked at a temperature of 900 ° C. or higher. .

If it is attempted to form a silica-based coating film under such severe oxidizing conditions, the semiconductor device, the transparent electrode, etc. are also exposed to high temperatures, which is not preferable. On the other hand, the present applicant has proposed that silica using a specific polysilazane in which R _{1 to} R ₃ in the above formula [I] are each independently a hydrogen atom or an alkyl group having 1 to 8 carbon atoms as a film-forming component. By applying the coating liquid for forming a coating film on the surface to be coated, drying the obtained coating film in air at a low temperature of about 150 ° C., and then baking at a temperature of 800 ° C. or less, a low nitrogen content is obtained. It has been found that a silica-based coating can be obtained. In particular, when all of R _{1 to} R ₃ are hydrogen atoms, the coating film is baked at a temperature of about 450 ° C. to obtain a silica coating film having a low nitrogen content.

As a result of further research based on the above findings, the present inventors have found that: a) a coating liquid containing a modified polysilazane obtained by modifying such a specific polysilazane with a specific alkanolamine. When a silica-based coating is formed in the same manner from a coating liquid containing only polysilazane as a coating-forming component when the coating is dried on the surface to be coated, dried, and then baked to form a silica-based coating. That a silica-based coating having a low nitrogen content can be obtained at a lower firing temperature as compared with, b) This silica-based coating containing almost no nitrogen atoms is
Excellent adhesion to the surface to be coated, mechanical strength, chemical resistance such as alkali resistance, moisture resistance and crack resistance, and at the same time a dense insulating film with almost no voids or pinholes. When a coating film is formed by applying a coating liquid containing the above-described two specific types of film-forming components on the surface to form a film, the uneven surface is highly flattened as in the case where the film-forming component is only polysilazane. D) Therefore, when a coated substrate as described above is produced by using a coating liquid containing the above-mentioned specific two kinds of film-forming components together, it is possible to produce They have found that a product with even better performance can be obtained, and completed the present invention.

[0025]

SUMMARY OF THE INVENTION The present invention is intended to solve the above-mentioned problems in the prior art, and is excellent in adhesiveness to a surface to be coated, mechanical strength, chemical resistance such as alkali resistance, At the same time, a dense insulating film with excellent crack resistance is used.
To provide a coating liquid for forming a silica-based coating film which can be formed at a firing temperature of 0 ° C. or less and which can highly flatten the unevenness of a coated surface, and a coated substrate having such excellent properties. Has an aim.

[0026]

SUMMARY OF THE INVENTION The coating solution for forming a silica-based coating film according to the present invention has the following general formula [I].

[0027]

[Chemical 4]

(In the formula, R ₁ , R ₂ and R ₃ are each independently a hydrogen atom or an alkyl group having 1 to 8 carbon atoms.) One type of polysilazane having at least a repeating unit Or two or more kinds and the following general formula [II] NH _n (R ₄ OH) _3-n ... [II] (In the formula, R ₄ is an alkyl group having 1 to 8 carbon atoms, and n is 0. The modified polysilazane obtained by reacting with an alkanolamine represented by the formula (1) is contained.

Further, the coated substrate according to the present invention is characterized by having a silica-based coating formed by using the above coating solution.

[0030]

DETAILED DESCRIPTION OF THE INVENTION The coating solution for forming a silica-based coating film according to the present invention will be specifically described below. Silica-based coating film forming coating liquid The silica-based coating film forming coating liquid according to the present invention contains one or more polysilazanes having at least a repeating unit represented by the general formula [I] as described above. It contains a modified polysilazane modified with an alkanolamine represented by [II].

Among these, in the polysilazane used in the present invention, R ₁ , R ₂ and R _{3 in} the above formula [I] are each a hydrogen atom or an alkyl group having 1 to 8 carbon atoms, and among the alkyl groups, A methyl group, an ethyl group or a propyl group is preferred.

As the polysilazane used in the present invention, R ₁ , R ₂ and R _{3 in} the above formula [I] are all hydrogen atoms, and 55 to 65 wt% of silicon atoms and 20 nitrogen atoms are contained in one molecule. ~ 30 wt%, hydrogen atom 10 ~ 1
Especially preferred is the inorganic polysilazane present in an amount such that it is 5% by weight. Such an inorganic polysilazane can be produced according to the method disclosed in, for example, Japanese Patent Publication No. 63-16325 and US Pat. No. 4,397,828.

The polysilazane having the repeating unit represented by the above formula [I] may be linear or cyclic, and the linear polysilazane and the cyclic polysilazane are contained as a mixture. May be.

The weight average molecular weight of the polysilazane used in the present invention is 500 to 10,000, preferably 1,0.
It is preferably in the range of 00 to 4,000. When the weight average molecular weight is less than 500, the low molecular weight compound is volatilized in the drying step when forming the silica-based coating from the coating liquid, and the coating is largely shrunk in the subsequent firing step. On the other hand, when the molecular weight exceeds 10,000, the fluidity of the coating solution decreases. Therefore, in any of the above cases, when the uneven surface is covered with the coating, it is difficult to sufficiently flatten the uneven surface with the coating. Further, the Si / N weight ratio of this polysilazane is preferably in the range of 1.0 to 1.3.

Furthermore, in the coating liquid for forming a silica-based coating film according to the present invention, polysilazane in which 10 to 40% by weight, preferably 15 to 40% by weight of the total polysilazane is a low molecular weight polysilazane having a molecular weight of 1,000 or less. Is preferred. When the low molecular weight polysilazane is less than 10% by weight, the fluidity of the coating liquid may be reduced, and the surface smoothness of the silica-based insulating film obtained from the coating liquid may be reduced. On the other hand, when the low molecular weight polysilazane exceeds 40% by weight, a large amount of low molecular weight compounds volatilize in the drying step when forming the silica-based coating from the coating liquid, and the coating shrinks greatly in the subsequent firing step. The surface smoothness of the silica-based coating film obtained from the coating solution may decrease.

The alkanolamine used in the present invention is also called amino alcohol, and means a saturated aliphatic amine having a hydroxyl group in the molecule as represented by the above general formula [II]. As such alkanolamine,
Specific examples include monoethanolamine (aminoethanol), aminobutanol, aminopropanol and the like.

The coating liquid for forming a silica-based coating film according to the present invention is prepared as follows. i) Mixing the polysilazane and the alkanolamine as described above in an organic solvent.

The organic solvent is not particularly limited as long as it can dissolve polysilazane and alkanolamine, and specifically, alcohols such as methanol and ethanol, ketones such as methyl isobutyl ketone,
Examples thereof include glycol ethers such as methyl cellosolve, cyclic hydrocarbons such as cyclohexane, toluene, xylene and mesitylene, and ethers such as ethylbutyl ether, dioxane and tetrahydrofuran. These organic solvents may be used alone or in admixture of two or more.

When polysilazane and alkanolamine are mixed in an organic solvent as described above, S of polysilazane is mixed.
The i-N bond part reacts with the alkanolamine to form a polysilazane modified product in which the Si-N bond part of the polysilazane is cleaved.

The reaction between the polysilazane and the alkanolamine is carried out at any temperature from 0 ° C. to the boiling point of the solvent or lower. The compounding ratio of polysilazane to alkanolamine used in this reaction is 99.9 / molar ratio.
It is desirable to adjust to the range of 0.1-50 / 50.
If the blending molar ratio exceeds 99.9 / 0.1, the polysilazane modification effect is almost absent, whereas if it is less than 50/50, the preferable properties of polysilazane tend to be impaired. ii) After completion of the polysilazane reforming reaction as described above, the solvent is removed from the liquid containing the polysilazane reformed product by a method such as vacuum distillation to obtain a resinous substance. iii) By dissolving the obtained resinous substance in an organic solvent so that the solid content concentration becomes 3 to 40% by weight, the coating liquid for forming a silica-based coating film according to the present invention is basically obtained.

The organic solvent used in this case is not particularly limited as long as it disperses or dissolves the above resinous substance and imparts fluidity to the coating liquid, but specifically,
Hydrocarbons such as cyclohexane, toluene, xylene, mesitylene, ethyl butyl ether, dibutyl ether,
Examples include ethers such as dioxane and tetrahydrofuran. These organic solvents may be used alone or in admixture of two or more.

The organic solvent used in the coating solution according to the present invention is preferably an organic solvent having a water solubility of 0.5% by weight or less. When such an organic solvent is used as the coating liquid, it is prevented that the coating liquid absorbs moisture and causes hydrolysis of polysilazane or the like in the coating liquid, whereby a coating liquid having a long pot life can be obtained.

The resinous substance obtained by the above method has a weight average molecular weight of 500 to 10,000, preferably 1,000 to 4,000.
When the weight average molecular weight is less than 500, the low molecular weight compound is volatilized in the drying step when forming the silica-based coating from the coating liquid, and the coating is largely shrunk in the subsequent firing step. Further, when the molecular weight exceeds 10,000, the fluidity of the coating solution decreases. Therefore, in any case, when the uneven surface is covered with the coating, it is difficult to sufficiently flatten the uneven surface with the coating. Further, the Si / N weight ratio of this resinous substance is similar to that of polysilazane.
It is preferably in the range of 1.0 to 1.3.

When a silica-based coating film is formed using the above-described coating liquid for forming a silica-based coating film according to the present invention, when a silica-based coating film is formed using a conventional coating liquid containing only polysilazane as a film-forming component Compared with, the coating film obtained from the coating liquid is excellent in compactness even when dried and then baked at a lower temperature than in the case of the conventional polysilazane-based coating liquid, and is excellent in flatness with less shrinkage stress and voids. A film obtained.

Particularly, the coating liquid for forming a silica-based coating film according to the present invention is represented by the above formula [I], and R ₁ and R in the formula [I] are represented.
_In the case of a coating solution containing a modified polysilazane obtained by modifying an inorganic polysilazane in which all of ₂ and R ₃ are hydrogen atoms with an alkanolamine, a coating film that is more dense and has excellent crack resistance can be obtained.

That is, when a silica-based coating film is formed from a coating solution in which most of the film-forming components are the above-mentioned modified inorganic polysilazane, the amount of alkyl groups contained in the film-forming components is small, Less shrinkage of the coating or generation of voids due to thermal decomposition of alkyl groups. Therefore, as described above, the silica-based coating film formed from the coating liquid having a film-forming component having a small number of alkyl groups has a smaller shrinkage than the silica-based coating film formed from the coating liquid having a film-forming component having a large amount of alkyl groups. Few. Therefore, the stress generated in the film due to the contraction of the film is small, and the cracks in the film caused by the contraction stress are reduced.
In addition, the number of voids associated with the decomposition of the alkyl group is small, and therefore the compactness is excellent.

Furthermore, the shrinkage of the coating film that occurs in the drying / baking process when forming the silica-based coating film is suppressed by the volume expansion when the Si—H bond in the modified polysilazane changes to the Si—O bond. For this reason, when a coating film is formed from a coating solution in which most of the film-forming components are the above-mentioned modified inorganic polysilazane, shrinkage stress at the time of film formation is reduced, and cracking is suppressed. Therefore, it is preferable to use the coating liquid in which most of the film-forming components are the modified inorganic polysilazane as described above, especially when forming a thick silica-based insulating film.

Coated Substrate As the coated substrate according to the present invention, specifically, the above-mentioned semiconductor device, liquid crystal display device, photomask with phase shifter, LSI element having a multilayer wiring structure, and Examples include printed circuit boards, hybrid ICs, electronic components such as alumina substrates, and three-layer resists.

That is, in the semiconductor device as described above,
Between the semiconductor substrate and the metal wiring layer, a silica-based coating is formed between the metal wiring layers, and a PN junction semiconductor provided on the semiconductor substrate and various elements such as a capacitor element and a resistance element are coated with the silica-based coating. The uneven surface formed by these elements is flattened.

In the liquid crystal display cell of the liquid crystal display device, between the transparent substrate of the transparent electrode plate and the transparent electrode, and between the transparent electrode and the alignment film of the transparent electrode plate having the alignment film on the transparent electrode, In a liquid crystal display cell in a color liquid crystal display device in which a silica-based coating is formed, a silica-based coating is formed on the pixel electrode of the electrode plate and the color filter of the counter electrode plate, and the uneven surface formed by the pixel electrode and the color filter is formed. Are flattened by the silica-based coating.

Further, the phase shifter of the photomask with a phase shifter and the intermediate layer of the three-layer resist are made of a silica-based coating, and the electronic component is also provided with the silica-based coating in the same manner as the semiconductor device, and the silica-based insulating film is covered. The coated surface is flattened by the silica coating.

The coated substrate according to the present invention has a silica-based coating formed by using a coating solution containing a modified polysilazane obtained by reacting one or more polysilazanes with an alkanolamine. ing. The thickness of the silica-based coating is usually 0.05 to 2 μ, preferably 0.1 to 1
It is about μ.

Such a silica-based coating is formed by applying the coating liquid for forming a silica-based coating according to the present invention as described above to the coated surface of a base material, for example, a transparent electrode plate when manufacturing a liquid crystal display device. It can be obtained by applying various methods such as a spray method, a spin coating method, a dipping method, a roll coating method, a screen printing method and a transfer printing method to the transparent electrode surface of, and then drying and baking the obtained coating film. it can.

[0054]

According to the coating solution for forming a coating film of the present invention, it has excellent adhesiveness to the surface to be coated, mechanical strength, chemical resistance such as alkali resistance, and at the same time has almost no voids or pinholes. A dense insulating film excellent in crack resistance can be formed at a firing temperature of 350 ° C. or lower, and furthermore, the unevenness of the coated surface can be highly flattened.

That is, when a silica-based coating is formed from a conventional coating solution containing only polysilazane as a coating-forming component, the thermal decomposition temperature of Si--N--Si bond is high and 350.degree.
When dried and calcined at the following temperatures, nitrogen atoms remain in the obtained silica-based coating, but a silica-based coating at the same drying / firing temperature from the coating liquid for forming a coating according to the present invention is used. When formed, almost no nitrogen atoms remain in the obtained silica coating. Further, the silica-based coating film thus obtained from the coating liquid for forming a coating film according to the present invention has higher density and alkali resistance as compared with the silica-based coating film obtained from the conventional coating liquid containing only polysilazane. Has excellent chemical resistance.

Thus, even if the coating liquid for forming a coating film according to the present invention is applied to the coated surface and the obtained coating film is dried and baked at a relatively low temperature of 350 ° C. or less, almost no nitrogen atoms remain. The reason why the silica-based coating is obtained is presumed as follows.

That is, when the polysilazane is modified with an alkanolamine as described above, the nitrogen atom portion firmly bonded to the silicon atom in the polysilazane molecule is replaced with the alkanolamine, and the nitrogen atom and two adjacent silicon atoms are substituted. The bond formed between and is cleaved. This is probably because the Si—N—Si bond having a relatively large bond energy disappears.

That is, according to the present invention, a silica-based coating is formed between the semiconductor substrate and the metal wiring layer, between the metal wiring layers, and a PN junction semiconductor provided on the semiconductor substrate, a capacitor element, a resistance element, etc. Various elements of the above are covered with a silica-based coating, and the uneven surface formed by these elements is flattened, and Na between the glass substrate and the transparent electrode is contained in the glass substrate. A liquid crystal formed with a silica-based film as a so-called alkaline passivation film, which can prevent the alkali component from migrating into the transparent electrode or eluting through the transparent electrode into the liquid crystal enclosed between the transparent electrodes. A display device and a transparent electrode plate having a silica-based coating between the transparent electrode and the alignment film A liquid crystal display device including a liquid crystal display cell, an electrode plate having a silica-based coating formed on a pixel electrode and a counter electrode plate having a silica-based coating formed on a color filter, and formed by the pixel electrode and the color filter A color liquid crystal display device including a liquid crystal display cell in which the formed uneven surface is flattened by the silica-based coating, a photomask with a phase shifter such that the phase shifter is a silica-based coating, and the intermediate layer is a silica-based coating. Such a three-layer resist, and an electronic component in which a silica-based coating is provided like the semiconductor device, and the coated surface of the silica-based insulating film is flattened by the silica-based coating, such as an LSI element having a multilayer wiring structure, and A coated substrate such as a printed circuit board, a hybrid IC, or an alumina substrate can be provided with high yield.

[0059]

EXAMPLES The present invention will be described below with reference to examples, but the present invention is not limited to these examples.

[0060]

[Manufacturing example]

1) Synthesis of polysilazane A Polysilazane A was synthesized by the following production method according to the production method described in JP-B-63-16325.

600 ml of pyridine was placed in a reactor installed in a thermostat having a temperature of 0 ° C., and 28.3 g of dichlorosilane was added with stirring to form a complex (pyridine adduct). Next, ammonia was blown into the liquid containing the pyridine adduct for 2 hours to cause precipitation. After removing this precipitate by filtration, the filtrate was heated at 80 ° C. for 10 hours and then depressurized to remove pyridine from the filtrate to obtain a resinous polysilazane A in the reactor. 2) Synthesis of polysilazane B A 1-liter four-necked flask containing 300 ml of methylene chloride was cooled to -5 ° C. Next, 34.2 g of methyldichlorosilane was added to the four-necked flask, and ammonia was further blown into the four-necked flask for 2 hours while stirring to cause precipitation in the liquid. After removing this precipitate by filtration, the filtrate was decompressed to remove methylene chloride from the filtrate to obtain a resinous polysilazane B.

Table 1 shows the results of elemental analysis of the above polysilazanes A and B, the Si / N weight ratio and the weight average molecular weight. The weight average molecular weights are polystyrene equivalent values measured by gel chromatography.

[0063]

Example 1 A 5 wt% xylene solution of polysilazane A and a 10 wt% methanol solution of monoethanolamine were mixed at a polysilazane A / monoethanolamine molar ratio of 95/5, and the mixture was heated at a temperature of 50 ° C. And reacted for 5 hours. Then, the solvent was removed under reduced pressure to obtain a resin-like modified polysilazane. Table 1 shows the elemental analysis results, Si / N weight ratio, and weight average molecular weight of the obtained modified polysilazane. The weight average molecular weight of the obtained modified polysilazane was measured in the same manner as the weight average molecular weight of the polysilazanes A and B.

The modified polysilazane obtained as described above was dissolved in xylene to obtain a silica-based coating film-forming coating liquid having a solid content concentration of 20% by weight. This coating solution was applied onto a 4-inch silicon wafer by a spin coating method, the resulting coating film was heated at 150 ° C. for 2 minutes to be dried, and then baked in air at 350 ° C. for 1 hour to obtain a silica-based coating film. Was formed. Table 2 shows the ESCA analysis results of the formed silica coating and the measurement results of crack resistance, denseness, and alkali resistance. The crack resistance, denseness and alkali resistance were measured as follows. a) Crack resistance A silica-based coating having a thickness of 2 µ was formed, and the presence or absence of cracks in the silica-based coating was observed with a microscope. b) Denseness A mixed solution of HF and HNO ₃ (HF / HNO ₃ = 1/1
It was calculated from the amount of change in film thickness before and after the silica-based coating film formed as described above was dipped for 2 minutes in an etching solution consisting of (00 weight ratio). The smaller the change in film thickness per unit time is, the higher the denseness is evaluated. c) Alkali resistance It was calculated from the amount of change in film thickness before and after the silica-based film formed as described above was immersed in a 5 wt% NaOH aqueous solution at 40 ° C. for 20 minutes. Note that the smaller the amount of change in film thickness,
It is evaluated to have excellent alkali resistance.

[0065]

Example 2 A solution of polysilazane A in 5% by weight of methyl isobutyl ketone and a solution of diethanolamine in 5% by weight of ethanol were mixed so that the molar ratio of polysilazane A / diethanolamine was 99/1, and then this mixed solution was mixed. After heating at 80 ° C. for 10 hours to react polysilazane A with diethanolamine, the solvent in the liquid was removed under reduced pressure to obtain a resin-like modified polysilazane. Elemental analysis results of the obtained modified polysilazane, Si
The / N weight ratio and the weight average molecular weight are shown in Table 1. The weight average molecular weight of the obtained modified polysilazane was measured in the same manner as the weight average molecular weight of the polysilazanes A and B.

Using the modified polysilazane thus obtained, a coating solution for forming a silica-based coating and a silica-based coating were obtained in the same manner as in Example 1, and the silica-based coating obtained in the same manner as in Example 1 ESCA analysis and measurement of crack resistance, denseness, and alkali resistance.

Table 2 shows the above analysis and measurement results.

[0068]

Example 3 A 3 wt% butyl ether solution of polysilazane B and a 20 wt% ethanol solution of triethanolamine were mixed so that the polysilazane B / triethanolamine molar ratio was 96/4, and the temperature was 40 ° C. 20
After reacting for a time, a resin-like modified polysilazane was obtained. Table 1 shows the elemental analysis results, Si / N weight ratio, and weight average molecular weight of the obtained modified polysilazane. The weight average molecular weight of the obtained modified polysilazane was measured in the same manner as the weight average molecular weight of the polysilazanes A and B.

Using the modified polysilazane thus obtained, a coating solution for forming a silica-based coating and a silica-based coating were obtained in the same manner as in Example 1, and the silica-based coating obtained in the same manner as in Example 1 ESCA analysis and measurement of crack resistance, denseness, and alkali resistance.

Table 2 shows the above analysis and measurement results.

[0071]

Comparative Example 1 A silica-based coating was obtained in the same manner as in Example 1, using a 20 wt% xylene solution of polysilazane A as a coating liquid for forming a silica-based coating to obtain a silica-based coating. ESCA analysis and measurement of crack resistance, denseness, and alkali resistance.

Table 2 shows the above analysis and measurement results.

[0073]

[Table 1]

[0074]

[Table 2]

[0075]

Examples 4 to 6 and Comparative Example 2 The silica-based coating film-forming coating solutions obtained in Examples 1 to 3 and Comparative Example 1 were used to form aluminum wiring as a model with line and space having 0.5 μ steps. It was applied on an inch silicon semiconductor substrate by spin coating.

The obtained coating film was dried at 150 ° C. for 2 minutes and then baked in dry air at 350 ° C. for 1 hour to form an insulating silica-based coating film. Next, a contact hole is formed by a lithographic method and an etching method, the obtained perforated silica-based coated semiconductor substrate is left in the air for one week, and then an upper aluminum wiring is formed on the silica-based coating by a sputtering method to form a Then, the semiconductor devices of Examples 4 to 6 and Comparative Example 2 were created. The above etching was performed by dry etching using a mixed gas of carbon tetrafluoride and oxygen.

The cross section of the obtained semiconductor device was observed by a scanning electron microscope to check the flatness and the presence of cracks of the silica-based coating formed on the semiconductor device, and the etching rate at the time of contact hole formation and the upper and lower aluminum wiring The change in resistance value before and after energization for 1000 hours was measured.

The results are shown in Table 3.

[0079]

[Table 3]

[0080]

Examples 7 to 9 and Comparative Example 3 The glass-based coating liquids obtained in Examples 1 to 3 and Comparative Example 1 were formed on a glass substrate on which aluminum wiring was modeled with a line and space of 1 μ step. Was applied by spin coating.

The obtained coating film was dried at 150 ° C. for 2 minutes and then baked at 350 ° C. for 1 hour in dry air to form an insulating silica-based coating film. Then, the coated base materials of Examples 7 to 9 and Comparative Example 3 thus obtained were subjected to HF and HN.
Mixed solution with O ₃ (HF / HNO ₃ = 1/100 weight ratio)
The etching rate of the silica-based coating film was calculated from the silica-based coating film after being dipped in the etching solution consisting of 2 minutes, and the coated substrates of Examples 7 to 9 and Comparative Example 3 were obtained as described above. The cross section was observed with a scanning electron microscope to measure the level difference on the surface of the coating and to check the presence or absence of cracks.

The results are shown in Table 4.

[0083]

[Table 4]

Claims (2)

[Claims] 1. The following general formula [I]: (In the formula, R ₁ , R ₂ and R ₃ are each independently a hydrogen atom or an alkyl group having 1 to 8 carbon atoms.)
And at least one polysilazane having at least a repeating unit represented by the following general formula [II] NH _n (R ₄ OH) _3-n ... [II] (In the formula, R ₄ has 1 carbon atom Is an alkyl group of 8 to 8, and n is an integer of 0 to 2), and contains a modified polysilazane obtained by reacting with an alkanolamine. . 2. A coated substrate comprising a silica-based coating formed by using the coating solution according to claim 1.