JPH0995646A - Coating composition for silica-based coating film and base material with silica-based coating film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain the subject composition capable of forming a coating film hardly causing remaining stress, dense and excellent in cracking resistance, highly flattening the unevenness on the surface to be coated. SOLUTION: This coating composition for silica-based coating film comprises a modified polysilazane obtained by reacting (A) one or more polysilazanes having a repeating unit of the formula (R<1> to R<3> are each H, a 1-8C alkyl or aryl) with (B) a boron compound of the formula R<4> n B(OR<5> )3-n (R<4> is H, a 1-8C alkyl or aryl; R<5> is H, a 1-8C alkyl, alkoxyalkyl or acyl; (n) is 0-2). The component B is used so as to make the amount of boron atom 0.1-20wt.% based on the weight of the modified polysilazane.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a coating composition for forming a silica-based coating and a substrate with a silica-based coating. More specifically, the residual stress is small, and it is dense and has excellent crack resistance, and moreover, the surface to be coated. The present invention relates to a coating composition for forming a silica-based coating capable of forming a silica-based coating capable of highly flattening the unevenness, and a coated substrate having the silica-based coating having the above characteristics.

[0002]

BACKGROUND OF THE INVENTION Silica-based coatings have hitherto been used in various fields. For example, in semiconductor devices,
It is used as an insulating film between a semiconductor substrate and a metal wiring layer such as an aluminum wiring layer, or between metal wiring layers. Further, it is also used as a PN junction semiconductor provided on a semiconductor substrate and as a protective film for various elements such as a capacitor element and a resistance element.

Further, when a metal wiring layer or the like is provided on a semiconductor substrate, unevenness occurs on the semiconductor substrate due to the metal wiring layer or the like. Even if a metal wiring layer or the like is further formed on this uneven surface, disconnection may occur due to uneven steps. Therefore, as described above, the silica-based insulating film is also formed on the uneven surface formed by the metal wiring layer and the various elements to play a role of flattening.

The silica-based coating used in the above fields is generally a vapor phase growth method such as a CVD method or a sputtering method, or a coating method for forming a silica-based coating using a coating composition for forming a silica-based coating. Formed on the substrate.

Of these, the method of forming the silica-based coating by the vapor phase growth method 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 required. Therefore, the uneven surface cannot be flattened.

On the other hand, when the silica-based coating is formed by the coating method, the above problems can be solved.
In recent years, forming a silica-based coating film by a coating method has been widely performed.

As a coating liquid for forming such a silica-based coating film, a coating liquid containing a partial hydrolyzate such as alkoxysilane or halogenated silane can be mentioned. In recent years, the wiring step of the multi-layer wiring layer on the semiconductor substrate has become large, and therefore the film thickness must be increased in order to flatten it. However, it has been difficult to increase the thickness of the conventional silica coating as described above.

On the other hand, if a silica-based coating is formed by using a coating liquid for forming a silica-based coating containing a cyclosilazane polymer or polysilazane, a thick film can be formed, and an insulation having a fine and flat surface can be obtained. A film can be formed.
However, as the film becomes thicker, shrinkage stress of the coating remains when the Si—N bond or Si—R bond is oxidized to form the Si—O bond, and thus the silica-based coating obtained has cracks and voids. It happened. . For example, when a conventional silica-based coating is formed on an aluminum wiring layer, problems such as disconnection due to stress migration of wiring and warpage of the wafer still remain.

As a result of various investigations for solving the above problems, the present inventors have found that a silica-based composition containing a specific modified polysilazane obtained by reacting polysilazane with a specific boron compound is used. It has been found that if a film is formed, a residual stress is low even if the film is thickened, and a silica-based film excellent in flatness and compactness can be obtained.

JP-A-6-326082 discloses a method of forming a borosilicate film on an electronic substrate by using a coating solution containing a borosilazane polymer, but to reduce residual stress of the film. Method is not described.

[0011]

SUMMARY OF THE INVENTION The present invention is intended to solve the above-mentioned problems in the prior art. The residual stress of the coating is small, and the adhesion to the surface to be coated, the mechanical strength and the alkali resistance are high. A coating for forming a silica-based coating that has chemical resistance such as, and is dense and excellent in crack resistance, and that can obtain a silica-based coating having a film thickness capable of highly flattening the irregularities of the coated surface. The present invention provides a composition, a substrate, and a silica-based coated substrate having the above silica coating formed thereon.

[0012]

SUMMARY OF THE INVENTION A coating composition for forming a silica-based film according to the present invention comprises one or more polysilazanes having a repeating unit represented by the following general formula [I],

[0013]

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(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;
It is a group selected from an aryl group. ) It is characterized by containing a modified polysilazane obtained by reacting with a boron compound represented by the following general formula [II].

R ⁴ _n B (OR ⁵ ) _3-n ... [II] (wherein R ⁴ Is a hydrogen atom or a group selected from an alkyl group having 1 to 8 carbon atoms and an aryl group, and R ⁵ Is a hydrogen atom or a group selected from an alkyl group having 1 to 8 carbon atoms, an alkoxyalkyl group and an acyl group, and n is 0 to
2. ) In the coating composition for forming a silica-based coating film according to the present invention, the boron compound is contained in the modified polysilazane in an amount of 0.1 to 20% by weight based on the total modified polysilazane. It is characterized in that it is contained. The total peak area observed in the chemical shift range of 60 to 90 ppm in the ¹⁵ N-NMR spectrum of the modified polysilazane is ^{10 to} 90 ppm.
Is preferably 20% or less of the total peak area observed in the range of
The polystyrene reduced number average molecular weight measured by gel chromatography is 1,000 to 10,000, and the total peak area of the modified polysilazane having a molecular weight of 700 or less is
10% of the total peak area of all modified polysilazanes
Below, and dispersity (weight average molecular weight / number average molecular weight)
Is preferably 3.5 or less.

Further, the silica-coated base material according to the present invention has a residual stress formed on the base material.
It is characterized by comprising a silica-based coating film having a density of less than × 10 ⁹ dyne / cm ² .

[0017]

DETAILED DESCRIPTION OF THE INVENTION The coating composition for forming a silica-based coating and the substrate with a silica-based coating according to the present invention will be specifically described below. <Silica-based film-forming coating composition> The silica-based film-forming coating composition according to the present invention is one or two having a repeating unit represented by the following general formula [I].
With more than one species of polysilazane,

[0018]

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(Wherein R ¹ , R ² and R ³ are each independently a hydrogen atom or an alkyl group having 1 to 8 carbon atoms,
It is a group selected from an aryl group. ) It contains a modified polysilazane obtained by reacting with a boron compound represented by the following general formula [II].

[0020] _{^{R 4 n B (OR 5)}} 3-n ... [II] ( wherein, R ⁴ Is a hydrogen atom or a group selected from an alkyl group having 1 to 8 carbon atoms and an aryl group, and R ⁵ Is a hydrogen atom or a group selected from an alkyl group having 1 to 8 carbon atoms, an alkoxyalkyl group and an acyl group, and n is 0 to
2. ) R ¹ in the general formula [I] , R ² And R ³ Is preferably one selected from a methyl group, an ethyl group and a propyl group as the alkyl group, and particularly R ¹ , R ² And R ³ Is preferably a hydrogen atom. In this case,
When the modified polysilazane described below is fired to form a silica-based coating, there is no alkyl group or aryl group that decomposes, so there is less shrinkage of the film and the residual stress of the resulting film is even smaller, resulting in cracks. A free coating is obtained.

The boricilazane having the repeating unit represented by the above general formula [I] may be linear or cyclic, and a mixture of linear polysilazane and cyclic polysilazane is used. Good.

^{15 of the} polysilazane represented by the general formula [I]
In the N-NMR spectrum, a chemical shift of 10
Peak is observed in the range of ~ 60ppm, but 10 ~ 33p
The total peak area in the pm range is preferably 30% or less of the total peak area in the 10-60 ppm range.

In the measurement of the ¹⁵ N-NMR spectrum of the present invention, hexamethylsilazane was used as a reference substance for measurement.
The chemical shift of the peak of the spectrum of this substance is 28
ppm was set.

Further, the Si / N ratio of the above polysilazane is preferably 1.00 to 1.30. R ⁴ in the general formula [II] is preferably one selected from a hydrogen atom, a methyl group, an ethyl group and a propyl group, and R ⁵ is preferably one selected from a methyl group, an ethyl group and a propyl group.

Specific examples include dihydroxymethoxyborane, hydroxydimethoxyborane, dimethylmethoxyborane, methyldimethoxyborane, trimethoxyborane, ethyldimethoxyborane, diethylmethoxyborane, triethoxyborane, ethyldiethoxyborane, diethylethoxyborane. , Propyldimethoxyborane and the like. Among these, especially trimethoxyborane,
Triethoxyborane is preferred.

Examples of the method for producing the modified polysilazane of the present invention include a method in which a predetermined amount of the above polysilazane and a boron compound are dissolved in an organic solvent and reacted. The reaction temperature is 0 to 200 ° C, preferably 100 to 200 ° C. As a result, it is considered that the N-bridged portion of polysilazane reacts with the alkoxy group of the boron compound to obtain a modified polysilazane.

The content of the boron compound in the modified polysilazane is such that the weight of boron atoms in the boron compound is 0.1 to 20% by weight of the total modified polysilazane.
The amount is preferably 1 to 10% by weight. If it is less than 0.1% by weight, the residual stress of the resulting coating may not be reduced, whereas if it exceeds 20% by weight, the film-forming property may be poor and a dense coating may not be obtained when the film thickness is increased. .

Of the modified polysilazane obtained by the above method
^{When the 15} N-NMR spectrum is measured, peaks are observed in the chemical shift range of 10 to 90 ppm. In the present invention, the smaller the total peak area in the range of 60 to 90 ppm, the smaller the residual stress. That is, it is preferable that the total peak area in the range of 60 to 90 ppm of chemical shift is 20% or less of the total peak area in the range of 10 to 90 ppm.

The molecular weight of such modified polysilazane is
The total peak area of the modified polysilazane having a polystyrene-reduced number average molecular weight of 1,000 to 10,000 and a molecular weight of 700 or less by gel chromatography is
10% of the total peak area of all modified polysilazanes
It is preferable that the dispersity (weight average molecular weight / number average molecular weight) is 3.5 or less.

By using such a modified polysilazane having a molecular weight distribution, a coating having excellent flatness can be formed. The coating composition for forming a silica-based coating film according to the present invention is preferably prepared by dissolving the modified polysilazane in an organic solvent so that the solid content concentration is 3 to 40% by weight. The organic solvent used in this case is not particularly limited as long as it disperses or dissolves the modified polysilazane and imparts fluidity to the coating liquid,
Specifically, hydrocarbons such as cyclohexane, toluene, xylene, ethyl ether, ethyl butyl ether,
Examples thereof include ethers such as dibutyl ether, dioxane and tetrahydrofuran, and esters such as cyclohexyl acetate. These organic solvents are used alone or in combination of two or more.

Further, as the above-mentioned organic solvent used in the coating composition for forming a silica-based coating film according to the present invention,
The water solubility is preferably 0.5% by weight or less.
By using such an organic solvent in the coating liquid, it is possible to prevent hydrolysis of the modified polysilazane and the like in the coating liquid, and thereby a silica-based coating film forming coating composition having a long pot life can be obtained. <Silica-based film-coated substrate> The silica-based film-coated substrate according to the present invention has a silica-based film having a residual stress of less than 2 × 10 ⁹ dyne / cm ² , preferably less than 1 × 10 ⁹ dyne / cm ² on the surface. Is formed in. Residual stress of silica coating is 2 × 10
^When it is less than ⁹ dyne / cm ² , cracks are hardly generated during drying or heating, and a film having excellent denseness can be obtained.

The film thickness is usually 0.05 to 2 μm, preferably 0.1 to 1 μm. Such a film having a small stress can be formed by using, for example, the above-mentioned coating composition for forming a silica-based film according to the present invention. Depending on the purpose, the coating composition for forming a silica-based coating film may be applied to a surface to be coated such as a metal plate or a substrate on which various elements are mounted by spraying, spin coating, dipping, roll coating, or screen. It can be obtained by applying by various methods such as a printing method and a transfer printing method, then drying the obtained coating film, and then performing heat curing treatment such as baking in air. When the coating film is heat-cured, a curing process in a humidified atmosphere or an ammonia atmosphere, or a curing process using ultraviolet rays or electron beams may be used together.

As such a silica-based coated substrate,
For example, a semiconductor device in which a silica-based coating is formed as a protective film for an insulating film between a semiconductor substrate and a metal wiring layer, a PN junction semiconductor provided on a semiconductor substrate, various elements such as a capacitor element and a resistance element, Further, an LSI element having a multilayer wiring structure and a printed circuit board, a hybrid IC, an electronic component such as an alumina substrate, a three-layer resist, and the like can be mentioned.

Further, a liquid crystal display device in which a silica-based coating is formed between the transparent substrate of the transparent electrode plate and the ITO film, and between the transparent electrode and the alignment film of the transparent electrode plate having the alignment film on the transparent electrode. Further, a liquid crystal display cell in a color liquid crystal display device in which a silica-based coating is formed on the pixel electrode of the electrode plate and the color filter of the counter electrode plate can be mentioned.

[0035]

EFFECT OF THE INVENTION By using the coating composition for forming a silica-based coating film according to the present invention, the residual stress of the coating film is small, and it has chemical resistance such as adhesion to the surface to be coated, mechanical strength and alkali resistance. And, it is dense and has excellent crack resistance,
Moreover, it is possible to obtain a silica-based coating having a film thickness capable of highly flattening the unevenness of the surface to be coated.

The silica-based coated substrate according to the present invention has a silica-based coating with a small residual stress formed on its surface. Therefore, the film-coated substrate has no cracks due to stress, has almost no voids, is dense, has excellent adhesion to various substrates, and has unevenness on the surface to be coated that is highly flattened. Therefore, by using such a silica-based coated substrate, it is possible to obtain a semiconductor device or the like in which wire breakage due to stress migration and wafer warpage are prevented.

[0037]

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

[0038]

[Production 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 whose temperature was 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 5 hours and then depressurized to remove xylidine from the filtrate to obtain a resinous polysilazane in the reactor. This polysilazane was dissolved in xylene to give a number average molecular weight of 14
A polysilazane A having a concentration of 20% by weight was obtained.

2) Synthesis of polysilazane B In the same manner as in the method of synthesizing polysilazane A, 600 ml of pyridine was placed in a reactor installed in a thermostat at a temperature of 0 ° C., and 28.3 g of dichlorosilane was added with stirring to obtain a complex. (Pyridine adduct) was formed. 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 12 hours and then decompressed to remove pyridine from the filtrate to obtain a resinous polysilazane in the reactor. This polysilazane was dissolved in xylene to obtain polysilazane B having a number average molecular weight of 2000 and a concentration of 20% by weight.

3) Synthesis of polysilazane C 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. This polysilazane was dissolved in xylene to obtain polysilazane C having a number average molecular weight of 500 and a concentration of 20% by weight.

4) Synthesis of polysilazane D In the same manner as in the method of synthesizing polysilazane A, 600 ml of pyridine was placed in a reactor installed in a thermostat at a temperature of 0 ° C., and 28.3 g of dichlorosilane was added with stirring to obtain a complex. (Pyridine adduct) was formed. 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 2 hours and then decompressed to remove pyridine from the filtrate to obtain a resinous polysilazane in the reactor. Dissolve this polysilazane in xylene,
Polysilazane D having a number average molecular weight of 1000 and a concentration of 20% by weight was obtained.

Table 1 shows the results of elemental analysis of the above polysilazanes A, B, C and D, molecular weight analysis data by gel chromatography, and ¹⁵ N-NMR spectrum data. In addition, these molecular weights are polystyrene conversion values measured by gel chromatography.

[0044]

[Table 1]

[0045]

Example 1 To 100 g of polysilazane A was added 20 g of trimethoxyborane (molar ratio: 1 / 6.7), and the mixture was mixed at 50 ° C. for 1 hour.
Allowed to react for hours. This reaction liquid was diluted to 5% by weight with pyridine, filled in a pressure resistant reactor, and heat-polymerized at 120 ° C. for 10 hours. Then, pyridine was removed by distillation under reduced pressure to obtain a resin-like modified polysilazane E.
The molecular weight data of the obtained modified polysilazane E is shown in Table 2.

The resinous modified polysilazane E obtained as described above was dissolved in xylene to obtain a coating composition for forming a silica-based film having a solid content concentration of 20% by weight. This silica-based coating composition for forming a coating film is
It was applied on a semiconductor substrate formed on an inch wafer by a spin coating method. After drying the obtained coating film at 250 ° C for 2 minutes, it is baked in air at 400 ° C for 1 hour,
A semiconductor device as a silica-coated base material was obtained.

The following items were evaluated for the above semiconductor device. Silica-based film stress: Measured with a thin film stress measuring device (manufactured by Scientific Measurement System Co.).

Stress-induced crack: A scanning electron micrograph of the cross section of the substrate was observed. Stress migration: The presence or absence of disconnection of the wiring layer was confirmed. Etching rate: The substrate was immersed in HF / NH ₄ F-based buffered hydrofluoric acid, and the difference in the thickness of the coating before and after the immersion was calculated as the etching rate.

Flatness: A scanning electron micrograph of the cross section of the substrate was observed. The results are shown in Table 3.

[0050]

Example 2 To 100 g of polysilazane B, 50 g of trimethoxyborane (molar ratio 1 / 16.8) was added and reacted at 50 ° C. for 2 hours. Diluted to 5% by weight with pyridine in the same manner as in Example 1, heat-polymerized in a pressure resistant reactor at 100 ° C. for 10 hours, and then removed by pyridine under reduced pressure to obtain modified polysilazane F. The molecular weight data of the obtained modified polysilazane F is shown in Table 2.

The resinous modified polysilazane obtained as described above was dissolved in cyclohexyl acetate to obtain a coating composition for forming a silica-based film having a solid content of 20% by weight.

A semiconductor device was obtained by coating and baking on a semiconductor substrate in the same manner as in Example 1 to obtain a silica-based coated substrate.
The above semiconductor device was evaluated in the same manner as in Example 1 and the results are shown in Table 3.

[0053]

Example 3 To 100 g of polysilazane C was added 50 g of triethoxyborane (molar ratio: 1 / 8.6), and the mixture was mixed at 50 ° C. for 5 hours.
Allowed to react for hours. 5% by weight of pyridine as in Example 1
Was diluted with water, heated and polymerized at 100 ° C. for 20 hours in a pressure resistant reactor, and pyridine was removed by distillation under reduced pressure to obtain modified polysilazane G. The molecular weight data of the obtained modified polysilazane G is shown in Table 2.

The resinous modified polysilazane obtained as described above was dissolved in cyclohexyl acetate to obtain a coating composition for forming a silica-based film having a solid content of 20% by weight.

By coating and baking on a semiconductor substrate in the same manner as in Example 1, a semiconductor device as a silica-based coated substrate was obtained. The above semiconductor device was evaluated in the same manner as in Example 1 and the results are shown in Table 3.

[0056]

Comparative Example 1 100 g of polysilazane D was diluted to 5% by weight with pyridine and heat-polymerized at 80 ° C. for 5 hours in a pressure resistant reactor. Pyridine was removed in the same manner as in Example 1,
Polysilazane H was obtained. The molecular weight data of the obtained polysilazane H are shown in Table 2.

The resinous polysilazane obtained as described above was dissolved in xylene to obtain a coating composition for forming a silica-based film having a solid content of 20% by weight. By coating and baking on a semiconductor substrate in the same manner as in Example 1, a semiconductor device as a silica-based coated substrate was obtained.

The above semiconductor device was evaluated in the same manner as in Example 1 and the results are shown in Table 3.

[0059]

Comparative Example 2 To 100 g of polysilazane D, 50 g of trimethoxyborane (molar ratio 1 / 16.8) was added and reacted at 50 ° C. for 2 hours. Diluted to 5% by weight with pyridine in the same manner as in Example 1, heat-polymerized in a pressure resistant reactor at 100 ° C. for 10 hours, and removed pyridine by vacuum distillation to obtain modified polysilazane I. Table 2 shows the molecular weight data of the obtained modified polysilazane I.

The resinous modified polysilazane obtained as described above was dissolved in cyclohexyl acetate to obtain a coating composition for forming a silica-based film having a solid content concentration of 20% by weight.

A semiconductor device was obtained by coating and baking on a semiconductor substrate in the same manner as in Example 1 to obtain a silica-coated base material.
The above semiconductor device was evaluated in the same manner as in Example 1 and the results are shown in Table 3.

[0062]

[Table 2]

[0063]

[Table 3]

Claims (6)

[Claims] 1. One or more kinds of polysilazanes having a repeating unit represented by the following general formula [I]; (In the formula, R ¹ , R ² and R ³ are each independently a hydrogen atom or a group selected from an alkyl group having 1 to 8 carbon atoms and an aryl group.) Represented by the following general formula [II]. A coating composition for forming a silica-based coating, which comprises a modified polysilazane obtained by reacting with a boron compound. R ⁴ _n B (OR ⁵ ) _3-n ... [II] (wherein R ⁴ Is a hydrogen atom or a group selected from an alkyl group having 1 to 8 carbon atoms and an aryl group, and R ⁵ Is a hydrogen atom or a group selected from an alkyl group having 1 to 8 carbon atoms, an alkoxyalkyl group and an acyl group, and n is 0 to
2. ) 2. The modified polysilazane contains a boron compound in an amount such that the weight of boron atoms is 0.1 to 20% by weight based on the total modified polysilazane. The coating composition for forming a silica-based film as described above. 3. The total peak area observed in the chemical shift range of 60 to 90 ppm in the ¹⁵ N-NMR spectrum of the modified polysilazane is 10 to 90 chemical shifts.
The coating composition for forming a silica-based coating film according to claim 1 or 2, which has a total peak area of 20% or less in the ppm range. 4. The modified polysilazane has a polystyrene reduced number average molecular weight measured by gel chromatography of 1,000 to 10,000, and the total peak area of the modified polysilazanes having a molecular weight of 700 or less is the total modified polysilazane. 4. The silica-based coating film forming method according to claim 1, which has a polydispersity (weight average molecular weight / number average molecular weight) of 3.5 or less with respect to the total of the peak areas. Coating composition. 5. A base material and residual stress of 2 × 10 on the base material.
A silica-based coated substrate, wherein a silica-based coating of less than ⁹ dyne / cm ² is formed. 6. The substrate with a silica-based coating according to claim 5, wherein the silica-based coating is formed by the coating composition for forming a silica-based coating according to any one of claims 1 to 4.