JP3912697B2 - Interlayer insulating film forming coating solution and insulating film forming method using the same - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a coating liquid for forming an interlayer insulating film and a method for forming an insulating film using the same. More specifically, the present invention contains a solvent that has excellent storage stability and coating properties, can form a dense and good surface shape film with good reproducibility, and has little influence on the human body. The present invention relates to a coating liquid for forming an interlayer insulating film that is preferably used in manufacturing liquid crystal display elements and the like, and a method for efficiently forming an interlayer insulating film using this coating liquid.
[0002]
[Prior art]
In manufacturing various electronic component materials such as semiconductor elements and liquid crystal display elements, it is often necessary to form an interlayer insulating film on a solid surface. As a coating solution for forming such an interlayer insulating film, various coating solutions using a highly inorganic polysilazane resin have been reported [[Electronic Materials], December, pp. 50-55 (1994). ), JP-A-4-341705, JP-A-6-73340, JP-A-6-128529, JP-A-6-142600).
[0003]
These interlayer insulating film forming coating solutions have a lower content of organic components in the film-forming material than coating solutions using conventional alkoxysilane, so that the coating solution is applied onto a substrate, dried, In forming an insulating film by a baking treatment, attention has been paid in recent years because the amount of organic components burned off during baking is small, and as a result a dense film is formed.
[0004]
However, since the coating liquid using the polysilazane resin is inferior in storage stability and has variations in quality, it is difficult to form a dense and good-shaped film with good reproducibility. Polysilazane sublimates during drying (100 to 300 ° C.), which adheres to the inner wall of the baking treatment apparatus and contaminates the inside of the apparatus, or the film contracts due to sublimation of polysilazane and causes cracks. There were drawbacks. Sublimation of these polysilazanes is considered to be caused by a relatively low molecular weight polysilazane contained in the coating solution.
[0005]
In addition, in the preparation of this coating solution, xylene is mainly used as an organic solvent because of its good storage stability. However, since xylene has a problem with safety to the human body, it is a non-xylene type for practical use. In addition, it is necessary to study a low toxicity solvent having good storage stability and coating properties.
[0006]
[Problems to be solved by the invention]
Under such circumstances, the present invention is excellent in storage stability and coating characteristics, and has a specific resistance value of 10 required for an interlayer insulating film.^Ten-10¹⁷It has an insulating property of about Ω · cm, does not generate cracks even when applied to a substrate with a step, forms a coating with good step coverage and good surface shape with good reproducibility. The present invention has been made for the purpose of providing a coating solution for forming an interlayer insulating film using a solvent that can be used and that has little influence on the human body, and a method for efficiently forming an insulating film using the coating solution.
[0007]
[Means for Solving the Problems]
  As a result of intensive studies to achieve the above object, the present inventors haveOrganicSiH in polysilazane_Three And SiCH _Three Was adjusted to a predetermined ratioTheA solution obtained by dissolving in an inert organic solvent can be used as a coating solution for forming an interlayer insulating film, and can be adapted to the purpose, and this coating solution is applied on a substrate and baked in a humidified atmosphere. The present inventors have found that an interlayer insulating film can be formed efficiently, and have completed the present invention based on this finding.
[0008]
  That is, the present invention¹H-NMR spectrumIn SiH ₁ , SiH ₂ , SiH _Three And SiCH _Three Polysilazanes having the peaks of and thoseTo the peak area ratioabout, SiH₁And SiH₂SiH for the sum of_ThreeThe ratio of 0.15-0.45, SiH ₁ And SiH ₂ SiCH for the sum of _Three The ratio of 0.30 to 0.55A coating liquid for forming an interlayer insulating film comprising an inert organic solvent solution of polysilazane prepared in the above, and a wet gas having a relative humidity of 45% or more in the firing zone after the coating liquid is applied on a substrate and dried, or Provided is a method for forming an interlayer insulating film, characterized by firing at a temperature in the range of 300 to 800 ° C. while flowing a humidified gas mixed with 0.001 to 0.1 g of water into 1 liter of carrier gas. To do.
[0009]
As the inert organic solvent in the interlayer insulating film forming coating solution, a dialkyl ether of an alkyl group having 4 or more carbon atoms is particularly suitable.
[0010]
DETAILED DESCRIPTION OF THE INVENTION
The polysilazane used in the coating solution of the present invention is not particularly limited, and a known one, for example, the polysilazane resin described in the above-mentioned prior art can be used. For the following reasons, the molecular weight of this polysilazane is in a narrow range. It is desirable.
[0011]
It is desired that an interlayer insulating film used for manufacturing a semiconductor element for forming a fine pattern can always form a film having a constant film thickness within a range of several tens of nm on tens of thousands of substrates. However, it is extremely difficult to control the film thickness, a slight difference in coating conditions greatly affects the film thickness, and due to the change over time of the coating liquid, a film formed using the coating liquid immediately after preparation, There may be a difference in film thickness between the film formed using a coating solution that has passed for several months. Therefore, it is indispensable to prepare a coating solution that has little change over time as long as possible, that is, has a good storage stability. For that purpose, it is important to define the molecular weight of polysilazane within a narrow range.
[0012]
In particular, polysilazane has an active hydrogen group (hydrogen bonded to nitrogen atom or silicon atom) inside, and this crosslinks easily to cause thickening and gelation. In order to obtain a desired film thickness or to easily adjust the concentration of the coating solution, a high molecular weight material is not preferred. On the other hand, if a large amount of low molecular weight is included, the crosslinkability is poor, the surface of the film becomes distorted, sublimates increase when the film dries, the film shrinks and the film thickness decreases, and cracks occur. Problems arise. Therefore, it is important to set the molecular weight range strictly.
[0013]
For these reasons, the polysilazane used in the present invention preferably has a polystyrene-equivalent weight average molecular weight (Mw) measured by gel permeation chromatography (GPC) in the range of 1500 to 5000, particularly 1700 to 1500. Those in the range of 3000 are preferred. The dispersity (Mw / Mn) is preferably in the range of 1 to 4.
[0014]
  In the present invention, in order to improve the storage stability and coating characteristics of the coating solution, and to form a dense and good-coated film with good reproducibility,¹SiH in H-NMR spectral area ratio₁And SiH₂SiH for the sum of_ThreeThe ratio of 0.15 to 0.45And SiH ₁ And SiH ₂ SiCH for the sum of _Three In the range of 0.30 to 0.55It is necessary to adjust. This adjustment can be performed, for example, by selecting the amount of raw material used and the reaction conditions when producing polysilazane, but the produced polysilazane is treated with hexamethyldisilazane, and a part of the active hydrogen of polysilazane is trimethylsilylated. It is advantageous to do so by substitution with groups.
[0015]
The treatment of polysilazane with hexamethyldisilazane is¹In the peak area ratio of the H-NMR spectrum (proton nuclear magnetic resonance spectrum), SiH₁And SiH₂SiH for the sum of_ThreeContinue until it is in the range of 0.15 to 0.45. If this ratio is less than 0.15, the coating characteristics deteriorate, pinholes are generated, the surface of the coating becomes distorted, and it becomes difficult to form a dense and surface-shaped coating. If it exceeds 1, the storage stability of the coating solution will deteriorate, and it will be difficult to form a film with good reproducibility. SiH in the peak area ratio of the polysilazane after treatment in terms of coating characteristics and storage stability₁And SiH₂SiH for the sum of_ThreeA particularly desirable ratio of is in the range of 0.22 to 0.32.
[0016]
  In addition, when polysilazane is treated with hexamethyldisilazane¹SiH in peak area ratio of H-NMR spectrum₁And SiH₂SiCH for the sum of_ThreeAbout the ratio ofIsIf this ratio exceeds 0.55, the storage stability will not be improved so much, but it will be economically disadvantageous.AndIn addition, if this ratio is too small, the storage stability of the coating solution is not improved, so in terms of storage stability and economy, SiH₁And SiH₂SiCH for the sum of_Three ofThe ratio is0.30 to 0.55, preferablyIt is chosen to be in the range of 0.30 to 0.50.
  In order to replace the active hydrogen of polysilazane with a trimethylsilyl group, a trimethylsilylating agent other than hexamethyldisilazane can also be used.
[0017]
Polysilazane¹In the H-NMR spectrum chart, SiH₁And SiH₂Is 4.5 to 5.3 ppm, SiCH_ThreeIs 0.0-0.2 ppm, SiH_ThreeAre attributed to peaks appearing at 4.3 to 4.5 ppm, respectively, so that the peak area ratio can be determined from the ratio of protons (hydrogen) based on the respective integral curves.
[0018]
The polysilazane used in the present invention can be produced by, for example, a method of performing polymerization by supplying ammonia or a method of performing polymerization by applying heat or pressure, but the polysilazane obtained by the latter method is stable over time. Since it is excellent in property, it is preferable.
[0019]
As the inert organic solvent used in the coating liquid of the present invention, the boiling point is about 50 to 200 ° C. from the viewpoint of fire fighting and drying, and the hygroscopicity is low from the viewpoint of storage stability of the coating liquid. Those having little influence are preferred. Examples of such compounds include dialkyl ethers of alkyl groups having 4 or more carbon atoms, cyclohexene, dimethylcyclohexane, ethylcyclohexane, p-menthane, decalin, 2,2,5-trimethylhexane, dipentene, decane, isononane, and octane. Of these, dialkyl ethers of alkyl groups having 4 or more carbon atoms are preferred, and dibutyl ether is particularly preferred. This inert organic solvent may be used independently and may be used in combination of 2 or more type.
[0020]
If necessary, a polysilazane sublimation inhibitor can be added to the coating solution of the present invention. In the coating drying process, relatively low molecular weight polysilazane is likely to sublime, but the sublimation inhibitor has a function of reacting with low molecular weight polysilazane to increase its molecular weight and suppress its sublimation. As such a sublimation inhibitor, for example, a trialkylamine can be preferably exemplified. When this trialkylamine remains unreacted, it is desirable to be removed together with the solvent in the drying step, and therefore, the boiling point is preferably about 200 to 300 ° C. As such a trialkylamine, those having a linear or branched alkyl group having 4 to 8 carbon atoms are preferable. For example, tributylamine, tripentylamine, trihexylamine, triheptylamine, trioctylamine, mono Examples thereof include butyldipentylamine and monohexyldipentylamine. Among these, tripentylamine is preferable in terms of storage stability and reactivity, and tri-n-pentylamine is particularly preferable. Moreover, these may be used independently and may be used in combination of 2 or more type.
[0021]
If the addition amount of the sublimation inhibitor is too small, the sublimation inhibitory effect is not sufficiently exerted, and if it is too much, the storage stability of the coating solution is lowered, or the molecular weight is increased during coating, and the coating unnecessary part is peeled off. In a process, the solubility with respect to peeling liquid worsens, and problems, such as being unable to perform a peeling process, arise. Therefore, the addition amount of the sublimation inhibitor is usually selected in the range of 1 to 10% by weight, preferably 3 to 5% by weight, based on the solid content.
[0022]
In contrast to hexamethyldisilazane, this sublimation inhibitor functions to increase the molecular weight of polysilazane. Therefore, it is necessary to consider the amount of hexamethyldisilazane added. Generally, about 0.7 to 1.5% by weight is appropriate for the amount of hexamethyldisilazane involved in the reaction.
[0023]
The solid content concentration of the coating solution of the present invention is not particularly limited, but if it is too high, the storage stability is lowered and it becomes difficult to control the film thickness. Inconveniences such as requiring repeated coating many times until a desired film thickness is obtained. Therefore, the solid content concentration is preferably in the range of 10 to 40% by weight, and particularly preferably in the range of 15 to 25% by weight.
[0024]
Next, a method of forming an insulating film using this interlayer insulating film forming coating solution will be described.
[0025]
First, the coating solution is usually applied at room temperature (about 20 to 25 ° C.) by a conventionally used means such as a spinner method, a spray method or a dipping method on a desired substrate, and then about 100 to 300 ° C. The polysilazane-based film is formed by removing the solvent in the coating solution by drying at a temperature of 5 ° C. In order to efficiently suppress sublimation of polysilazane, it is advantageous to wait for at least 1 minute at a temperature of 25 to 100 ° C., preferably 40 to 70 ° C. before the drying treatment. This is for sufficiently reacting the sublimation inhibitor and polysilazane to suppress sublimation of the low molecular weight substance, and it is preferable to wait at a temperature of 70 ° C. or lower for 3 minutes or longer. If it is carried out at a temperature exceeding 100 ° C., suppression of sublimation may not be sufficient, and smoke may be generated due to sublimation of polysilazane during drying. The reason for this is not necessarily clear, but it is presumably because the reaction between the polysilazane and the sublimation inhibitor is accelerated by heating, and unevenness is formed in the reaction portion, so that unreacted low molecular weight polysilazane remains.
[0026]
Therefore, it seems that it is preferable to carry out the reaction at a low temperature and based on the reactivity of the sublimation inhibitor itself without leaving unevenness in the reaction part. In addition, this operation may be performed by changing the temperature stepwise. For example, after application, the temperature may be set to 50 ° C. for 1 minute, 60 ° C. for 1 minute, and 90 ° C. for 1 minute. .
[0027]
The waiting time is preferably 1 minute or longer, and when it is less than 1 minute, sublimation of polysilazane tends to occur in the next drying step. Sublimated polysilazane is deposited on the dry indoor wall with SiO.₂These crystals are deposited and fall on the coating film to cause deterioration of the quality of the film, or the film shrinks due to the sublimation of polysilazane, and the film thickness tends to decrease. By waiting for 1 minute or longer, such a phenomenon is eliminated, and a film having a stable quality can always be formed.
[0028]
During the standby time, it can be performed in a dry atmosphere or a humidified atmosphere. However, if the film is placed in an excessively humidified state, the film absorbs moisture in the air, so that the atmosphere has a relative humidity of about 45 to 55%. It is appropriate to do. In addition, since the effect of a sublimation inhibitor tends to increase in a humidified state, it can be performed in an atmosphere exceeding 55% in anticipation of the effect.
[0029]
Furthermore, the standby may be performed in the coating chamber where the coating is performed, but during the standby, the application operation to the next substrate cannot be performed, and the throughput decreases and the set temperature needs to be changed. Specifically, it is preferable to perform a flow work by providing a standby chamber or a hot plate maintained at a set temperature.
[0030]
Next, the thus-formed polysilazane-based film is a humidified gas in which 0.001 to 0.1 g of moisture is mixed with 1 liter of a humidified gas or a carrier gas having a relative humidity of 45% or more in the firing zone. The polysilazane coating is baked for about 15 to 60 minutes at a temperature in the range of 300 to 800 ° C.₂) By converting into a film, an interlayer insulating film is formed. At this time, if necessary, it is not necessary to convert all of the polysilazane into silicon oxide, and the firing time, firing temperature, and firing atmosphere can be appropriately selected according to the purpose. The carrier gas is preferably oxygen gas.
[0031]
The interlayer insulating film thus formed is a film substantially made of silicon oxide having a good film quality without cracks and having a film thickness of about 0.1 to 1.2 μm with respect to an uneven substrate.
[0032]
【The invention's effect】
The coating liquid for forming an interlayer insulating film of the present invention is excellent in storage stability and coating characteristics, and forms a dense and surface-shaped film with good reproducibility that has sufficient resistance as an interlayer insulating film in terms of electrical characteristics. It contains a solvent that has little influence on the human body, and is suitably used in the production of various electronic component materials such as semiconductor elements and liquid crystal display elements.
[0033]
【Example】
EXAMPLES Next, although an Example demonstrates this invention still in detail, this invention is not limited at all by these examples.
[0034]
Example 1
(1) Preparation of coating solution
Add hexamethyldisilazane to polysilazane synthesized according to a conventional method using dichlorosilane and ammonia as raw materials.¹By calculating the peak area ratio of the H-NMR spectrum (SiH₁+ SiH₂) / SiCH_Three/ SiH_Three100 g of a 20 wt% dibutyl ether solution (coating solution A) of polysilazane (weight average molecular weight = 2200, number average molecular weight = 950) having a ratio of 1 / 0.45 / 0.40 was prepared.
[0035]
(2) Formation of insulating film
Application obtained in (1) above on a silicon wafer having a circuit pattern [step difference: 1 μm, line and space (L / S); 1.2 μm / 0.7-10.0 μm] formed of aluminum on the surface When the liquid A was spin-coated at 2000 rpm for 20 seconds under the conditions of a room temperature of 23 ° C. and a humidity of 45%, the coating property was good. Next, dibutyl ether was sprayed at 1500 rpm from the wafer edge cleaning nozzle of the apparatus at 50 ml / min for 5 seconds. As a result, the polysilazane coating solution at the peripheral edge was completely removed and the peelability was good. Thereafter, drying is performed at 250 ° C. for 3 minutes, and then, the silicon oxide film is baked at a temperature of 450 ° C. for 30 minutes in a baking chamber in which a humidified gas containing oxygen as a carrier gas and having a relative humidity of about 90% is supplied. An insulating film was formed. This silicon oxide film was a coating with good insulating properties, no cracks on the surface, excellent flatness and extremely uniform properties. Further, when the coating time was changed to 10 seconds on the bare wafer and the film was formed in the same manner, the film thickness was 0.36 μm. The film thickness at this time was measured using an ellipsometer.
[0036]
Examples 2 and 3
(1) Preparation of coating solution
In Example 1 (1), the amount of hexamethyldisilazane added was¹By calculating the peak area ratio of the H-NMR spectrum (SiH₁+ SiH₂) / SiCH_Three/ SiH_ThreeCoating liquids B and C were prepared in the same manner as in Example 1 (1) except that the ratio was changed to 1 / 0.30 / 0.40 and 1 / 0.50 / 0.40.
[0037]
(2) Formation of insulating film
Except that the coating solutions B and C obtained in (1) above were used, the coating solution was carried out in the same manner as in Example 1 (2), and the coating properties, peelability, surface shape, and insulation were examined. Good results were obtained for both B and C.
[0038]
Examples 4 and 5
(1) Preparation of coating solution
In Example 1 (1), the amount of hexamethyldisilazane added was¹By calculating the peak area ratio of the H-NMR spectrum (SiH₁+ SiH₂) / SiCH_Three/ SiH_ThreeThe coating liquids D and E were adjusted in the same manner as in Example 1 (1) except that the ratio was changed to 1 / 0.45 / 0.30 and 1 / 0.45 / 0.45.
[0039]
(2) Formation of insulating film
Except that the coating solutions D and E obtained in (1) above were used, the coating solution was carried out in the same manner as in Example 1 (2), and the coating properties, peelability, surface shape, and insulation were examined. Good results were obtained for all E.
The coating solution D was slightly inferior in coating properties, and slight striation was observed, but the surface shape did not change and was a good film.
[0040]
Examples 6-8
(1) Preparation of coating solution
Coating solutions F, G and H were prepared in the same manner as in Example 1 (1) except that the solvent was changed from dibutyl ether to octane, isononane or n-decane in Example 1 (1).
(2) Formation of insulating film
Except for using the coating liquids F, G and H obtained in (1) above, the same as in Example 1 (2) was carried out, and the coating property, peelability, surface shape, and insulation were examined. Coating solutions F, G, and H were slightly inferior in coating properties, and slight striation was observed, but the surface shape did not change and was a good film.
[0041]
Example 9
(1) Preparation of coating solution
In Example 1 (1), the amount of hexamethyldisilazane added was¹By calculating the peak area ratio of the H-NMR spectrum (SiH₁+ SiH₂) / SiCH_Three/ SiH_ThreeThe coating liquid I was prepared in the same manner as in Example 1 (1) except that the ratio of A was changed to 1 / 0.45 / 0.27 and 1.0 g of tri-n-pentylamine was added. .
[0042]
(2) Formation of insulating film
The coating liquid I obtained in (1) above was applied at room temperature on a silicon wafer having a circuit pattern [step difference: 1 μm, L / S; 1.2 μm / 0.7-10.0 μm] formed on the surface with aluminum. When spin coating was performed at 2000 rpm for 10 seconds under the conditions of ° C. and humidity of 45%, the coating property was good. Next, dibutyl ether was sprayed at 1500 rpm from the wafer edge cleaning nozzle of the apparatus at 50 ml / min for 5 seconds. As a result, the polysilazane coating solution at the peripheral edge was completely removed and the peelability was good. Thereafter, it was waited at 50 ° C. for 3 minutes, and then dried at 250 ° C. for 3 minutes.
[0043]
Next, an insulating film made of a silicon oxide film was formed by baking at a temperature of 450 ° C. for 30 minutes in a baking chamber in which a humidified gas containing moisture containing oxygen as a carrier gas and having a relative humidity of about 90% was flowed. This silicon oxide film was a film having excellent flatness, excellent uniformity, and no insulation on the surface. Further, when a film was formed on the bare wafer under the same conditions, the film thickness was 0.36 μm. The film thickness at this time was measured using an ellipsometer.
[0044]
Examples 10 and 11
(1) Preparation of coating solution
In Example 9 (1), coating solutions J and K were used in the same manner as in Example 9 (1) except that tri-n-butylamine and tri-n-hexylamine were used instead of tri-n-pentylamine. Was prepared.
(2) Formation of insulating film
Except for using the coating liquids J and K obtained in (1) above, this was carried out in the same manner as in Example 9 (2), and the coating property, peelability, smoke generation status, surface shape, and insulation were examined. However, good results were obtained in both cases.
[0045]
Example 12
(1) Preparation of coating solution
A coating liquid L was prepared in the same manner as in Example 9 (1) except that the amount of tri-n-pentylamine added was changed to 2.5 g in Example 9 (1).
(2) Formation of insulating film
Except that the coating liquid L obtained in the above (1) was used, it was carried out in the same manner as in Example 9 (2), and the coating property, peelability, smoke generation state, surface shape, and insulation were examined. The coating solution at the peripheral edge could not be removed sufficiently. For all other evaluations, good results were obtained.
[0046]
Examples 13-16
Except for changing the standby temperature to 20 ° C., 30 ° C., 70 ° C., 90 ° C., it was carried out in the same manner as in Example 9 (2), and the smoke generation situation, surface shape, and insulation were examined. Smoke was slightly seen, but the surface shape did not change. Regarding other temperatures, good results were obtained in the same manner as in Example 9 (2).
[0047]
Example 17
Except that the standby temperature was changed to 120 ° C., it was carried out in the same manner as in Example 9 (2), and when the smoke generation status, surface shape, and insulation were examined, a small amount of smoke was observed, and SiO 2 was found on the inner wall of the drying chamber.₂A faint deposit was detected. Further, no abnormality was observed in the surface shape.
[0048]
Examples 18-20
Except that the waiting time was changed to 2 minutes, 7 minutes, and 10 minutes, it was carried out in the same manner as in Example 9 (2), and the smoke generation status, surface shape, and insulation were examined. However, the surface shape was not changed. Regarding other times, as in Example 9 (2), good results were obtained in all cases.
[0049]
Example 21
Except for changing the waiting time to 1 minute, it was carried out in the same manner as in Example 9 (2), and when the smoke generation status, surface shape, and insulation were examined, a small amount of smoke was observed, and SiO2 was found on the inner wall of the drying chamber.₂A faint deposit was detected. Further, no abnormality was observed in the surface shape.
[0050]
Example 22
Example 9 (2) is the same as Example 9 (2) except that a humidified gas in which 0.02 g of water is mixed with 1 liter of oxygen gas is used instead of the humidified gas having a relative humidity of about 90%. When the operation was repeated and the surface shape and the insulating properties were examined, good results were obtained in both cases.
[0051]
Comparative Example 1
(1) Preparation of coating solution
In Example 1 (1), the amount of hexamethyldisilazane added was¹By calculating the peak area ratio of the H-NMR spectrum (SiH₁+ SiH₂) / SiCH_Three/ SiH_ThreeA coating solution X was prepared in the same manner as in Example 1 (1) except that the ratio was changed to 1/0 / 0.10.
(2) Formation of insulating film
Except that the coating solution X obtained in (1) above was used, the coating properties and the surface shape were examined in the same manner as in Example 1 (2). It was skin-like. Further, when the film composition was examined by FT-IR after the drying process, SiO 2₂Progressed and the stability over time was low.
[0052]
Comparative Example 2
(1) Preparation of coating solution
In Example 1 (1), the amount of hexamethyldisilazane added was¹By calculating the peak area ratio of the H-NMR spectrum (SiH₁+ SiH₂) / SiCH_Three/ SiH_ThreeA coating solution Y was prepared in the same manner as in Example 1 (1) except that the ratio was changed to 1 / 0.45 / 0.10.
(2) Formation of insulating film
Except that the coating solution Y obtained in (1) above was used, the coating solution and the surface shape were examined in the same manner as in Example 1 (2). It was skin-like.
[0053]
Reference example
The coating liquids A to L, X, and Y obtained in Examples 1 (1) to 12 (1) and Comparative Examples 1 (1) and 2 (1) were sealed at 40 ° C. in a glass container sealed in the atmosphere. As a result of storage for months, the coating liquids B and L showed a slight increase in viscosity and molecular weight, and the weight average molecular weight (Mw) increased by about 100 to 200.
In addition, the coating solution X had a marked increase in viscosity and an increase of 1500 in weight average molecular weight.
[0054]
Example 23
A film with a thickness of 5000 mm was formed on the coated substrate formed in Examples 1 to 22 by a plasma CVD method using tetraethoxysilane as a raw material.
As a result, when the coated substrate of Examples 1 to 8 was used, the surface was slightly roughened on the tetraethoxysilane coating, but it was a substantially flat and good quality film. When the coated substrate of Examples 9 to 22 was used, it was a very smooth and good quality coating.
[0055]
Comparative Example 3
A coating film was formed in the same manner as in Example 22 except that the coated substrate formed in Comparative Examples 1 and 2 was used.
As a result, in each of the tetraethoxysilane coatings, a large number of irregularities thought to be caused by particles on the underlying polysilazane coating were generated, and remarkable surface roughness was observed.
As described above, when an interlayer insulating film is formed using the coating liquids A to L, a high-quality film with little surface roughness can be formed on the interlayer insulating film.

Claims (7)

In ¹ H-NMR spectrum, a polysilazane having a peak of SiH _1, SiH _2, SiH ₃ and SiCH _3, and with their peak area ratio, the ratio of SiH ₃ to the sum of SiH ₁ and SiH ₂ 0 A coating solution for forming an interlayer insulating film comprising an inert organic solvent solution of polysilazane in which the ratio of SiCH _{3 to} the sum of SiH ₁ and SiH ₂ is adjusted to 0.30 to 0.55 . An interlayer insulating film-forming coating solution as claimed in claim 1, wherein the adjustment is performed with hexamethyldisilazane treatment. The coating liquid for forming an interlayer insulating film according to claim 1 or 2, wherein the inert organic solvent has a boiling point of 50 to 200 ° C. 4. The coating liquid for forming an interlayer insulating film according to claim 1, wherein the inert organic solvent is a dialkyl ether having an alkyl group having 4 or more carbon atoms.   The coating liquid for interlayer insulation film formation in any one of Claim 1 thru | or 4 containing a sublimation inhibitor.   The coating liquid for forming an interlayer insulating film according to any one of claims 1 to 5 is applied onto a substrate and dried, and then 300 to 800 while a humidified gas having a relative humidity of 45% or more is allowed to flow in the firing zone. A method for forming an interlayer insulating film, comprising firing at a temperature in the range of ° C.   The coating liquid for forming an interlayer insulating film according to any one of claims 1 to 5 is applied on a substrate, dried, and then 0.001 to 0.1 g of moisture per 1 liter of carrier gas in a firing zone. A method for forming an interlayer insulating film, characterized by firing at a temperature in the range of 300 to 800 ° C. while flowing a humidified gas mixed with.