JPH03188179A - Coating liquid for forming silica film, preparation of semiconductor substrate and semiconductor device - Google Patents

Abstract

PURPOSE:To obtain the title coating liq. with which a thicker coating film can be formed and which has improved storage stability by forming at first a siloxane polymer using only a tetraalkoxysilane compd. and then reacting a alkoxysilane and furthermore a dialkoxysilane compd. CONSTITUTION:A silica film forming coating liq. contg. a siloxane polymer obtd. by synthesizing at first a siloxane polymer by performing hydrolysis and polycondensation of a tetraalkoxysilane compd. of formula I (wherein R is an alkyl or an aryl), incorporating therein a trialkoxysilane compd. of formula II (wherein R and R' are each an alkyl or an aryl) (e.g. methytrimethoxysilane), performing hydrolysis and polycondensation thereof, and furthermore incorporating therein a dialkoxysilane of formula III (wherein R and R' are as defined above) (e.g. dimethydimethoxysilane), and performing hydrolysis and polycondensation thereof is obtd. As it is possible to form a silica film with a large thickness by using this coating liq. and the storage stability thereof is high, it is possible to manufacture a device with high reliability by using this film as an interlaminar insulation film of a semiconductor device, etc.

Description

Detailed Description of the Invention (Field of Industrial Application) The present invention relates to insulating films used in semiconductor devices, etc., and relates to a coating liquid for forming a silica-based film that can be thickened and has high storage stability. The present invention relates to a method for manufacturing a semiconductor substrate and a semiconductor device.

(Conventional technology) Semiconductor insulating films are made of polysilicon and aluminum (AJ)
Between wiring layers, AI! In addition to being used for insulation between wiring layers, it is also widely used for purposes such as PN junction protection, element surface protection, and filling of trenches for isolation between elements. Vapor phase growth and coating film methods are generally known as methods for forming insulating films, and the former is generally used, but this method requires special equipment and is difficult to process. There are problems such as restrictions on the size of the material and difficulty in mass production.

Furthermore, as semiconductor devices become more highly integrated, the grooves between patterns tend to become narrower and the device surface becomes more uneven, making conventional vapor phase growth methods too dependent on the surface structure. , it has become difficult to guarantee insulation. From this point of view, coating film methods with excellent flatness are being reconsidered.

Many coating films have been proposed to date. Typical organic materials include polyimide and polyimide silicone, but these are flat.

Although it has excellent crack resistance, its major drawback is that it partially decomposes at temperatures above 450°C.

On the other hand, silica glass-based coatings, typically made of polycondensates of tetraethoxysilane, have excellent heat resistance and adhesion to substrates, but have the problem of being prone to cracking if the film is thick. be. In order to improve this crack resistance, a silica-based coating containing an organic group is used. Using an alkoxysilane compound as a raw material having an organic group such as an alkyl group or an aryl group, the organic group is introduced into the siloxane polymer produced by hydrolytic polycondensation. Therefore, even if a silica-based film is formed, the organic groups remain and relax the stress in the film, making it difficult for cracks to form. However, since the ends of the siloxane polymer in the coating solution for forming a silica-based film are covered with hydroxyl groups other than organic groups, the polycondensation reaction progresses over time. Therefore, the viscosity of the coating solution for forming a silica-based film increases, and furthermore, it becomes gelled. As a result, problems such as changes in the thickness of the silica-based coating formed by coating using the spin-coating method, for example, occur.

(Problem to be solved by the invention) The present invention has been made in view of the current situation.

It is possible to sufficiently fill the grooves between patterns of semiconductor devices, etc., and prevents cracks from forming even if the film is thick.
Furthermore, the present invention provides a coating liquid for forming a silica-based film with improved liquid storage stability, a method for manufacturing a semiconductor substrate using the same, and a semiconductor device.

(Means for solving the problem) The poor storage stability of the silica-based film forming coating solution is due to the dehydration condensation of the hydroxyl groups of the siloxane polymer, as described above.In order to improve the storage stability, All that is needed is to reduce the number of hydroxyl groups.

The hydrolytic condensation reaction of an alkoxysilane compound is generally carried out in a solvent in the presence of an acid or alkali catalyst and water. A siloxane polymer having an organic group usually has the following general formula (I) as its raw material.

It is synthesized by mixing two or more types of alkoxysilane compounds represented by (Ill or Cl1l) from the initial stage of synthesis and subjecting them to hydrolytic polycondensation.

5i (ORI') 4 (I) R81 (OR), (Il
(R and W represent an alkyl group or an aryl group.) The synthesized siloxane polymer is not a chain polymer but has a network or particulate shape. Therefore, the organic groups are uniformly distributed and bonded within the network or particulate siloxane polymer. The present inventors investigated increasing the density of organic groups on the surface of the siloxane polymer and decreasing the amount of hydroxyl groups, and formed a siloxane polymer using only the tetrafunctional alkoxysilane compound represented by the general formula (I1). rear.

By adding and reacting a trifunctional alkoxysilane compound represented by the general formula (I[), and further reacting with a difunctional alkoxysilane compound represented by the general formula (III), a coating liquid for forming a liquified film is prepared. I just started it.

It has been found that the resulting coating solution for forming a silica-based film has better viscosity stability than that obtained by conventional synthesis methods.

One possible means of increasing the density of organic groups bonded to a siloxane polymer is to increase the proportion of trifunctional or difunctional alkoxysilane compounds in the alkoxysilane compound used as a raw material. If the proportion of the silane compound becomes too large, repelling will easily occur when the prepared coating solution for forming a silica-based film is applied to a semiconductor substrate such as a silicon wafer.

The present invention is.

General formula (I) % formula %) (I) Si(OR' represents an alkyl group or an aryl group.

) After synthesizing a siloxane polymer by hydrolyzing and polycondensing the tetraalkoxysilane compound represented by

General formula (It) R8i (ORI')s (n) Si(
OR and blur indicate an alkyl group or an aryl group. ) is added and subjected to hydrolytic condensation, and then the general formula (I[I) RzSi(0bi)! (I)Si(OR
and R' represents an alkyl group or an aryl group. ) A coating liquid for forming a silica-based film, which contains a siloxane polymer obtained by adding a dialkoxysilane compound represented by the following formula and subjecting it to hydrolytic condensation polymerization.

The present invention relates to a method for manufacturing a semiconductor substrate and a semiconductor device using the same.

A specific example of the tetraalkoxysilane compound represented by general formula (I) is tetramethoxysilane.

Tetraethoxysilane, tetrapropoxysilane.

Tetraisopropoxysilane, Tetrabutoxysilane,
Examples include tetrabutoxysilane and tetraphenoxysilane. In particular, tetramethoxysilane and tetraethoxysilane are preferably used.

A specific example of the trialkoxysilane compound represented by the general formula (■) is methyltrimethoxysilane.

Methyltriethoxysilane, methyltripropoxysilane, methyltriisopropoxysilane, ethyltrimethoxysilane, ethyltriethoxysilane, ethyltripropoxysilane, ethyltriisopropoxysilane, phenyltrimethoxysilane, phenyltriethoxysilane, phenyltripropoxy Examples include silane, phenyltriynepropoxysilane, and the like. %, methyltrimethoxysilane, methyltriethoxysilane, methyltripropoxysilane, and methyltriynepropoxysilane are preferably used.

A specific example of the dialkoxysilane compound represented by the general formula (DI+) is dimethyldimethoxysilane.

Dimethyljethoxysilane, dimethyldipropoxysilane, dimethyldiisopropoxysilane, diethyldimethoxysilane, diethyljethoxysilane, diethyldigloboxysilane, diethyldiisoproboxysilane, diphenyldimethoxysilane, diphenyljethoxysilane, diphenyldiglobo Examples include xysilane and diphenyldiisogloboxysilane 7. In particular, dimethyldimethoxysilane, dimethyljethoxysilane, dimethyldipropoxysilane, and dimethyldiimpropoxysilane are preferably used. General formula (I1, (II) or (I
Two or more types of the alkoxysilane compounds represented by n) may be used in combination.

Solvents include alcohols such as methanol, ethanol, gropanol, butanol, and acetone.

Ketones such as methyl ethyl ketone, dihydric alcohols, 2
Monoethers, diethers, etc. of alcohols are used. Dihydric alcohols include ethylene glycol, diethylene glycol, and cyfropylene glycol. Monoethers of dihydric alcohols include ethylene glycol 7-methyl ether, ethylene glycol 7-methyl ether, ethylene glycol monopropyl ether, ethylene glycol motubutyl ether, and ethylene glycol. Monoisobutyl ether, ethylene glycol 7-hexyl ether, ethylene glycol monophenyl ether, fluoropylene gelicol monomethyl ether, propylene glycol monopropyl ether, propylene glycol motubutyl ether, fluoropylene gelicol monomethyl ether, diethylene glycol monomethyl ether, diethylene glycol monomethyl ether ethyl ether.

Diethylene glycol monobutyl ether, diethylene glycol monoisobutyl ether, diethylene glycol monohexyl ether, triethylene glycol monomethyl ether, triethylene glycol monobutyl ether, dipropylene glycol monomethyl ether, dipropylene glycol monopropyl ether, dipropylene glycol monobutyl ether, tripropylene glycol Monomethyl ether, etc.

Examples of diethers of dihydric alcohols include ethylene glycol dimethyl ether, ethylene glycol diethyl ether, ethylene glycol dipropyl ether, ethylene glycol dibutyl ether, and diethylene glycol dimethyl ether.

Diethylene glycol diethyl ether, diethylene glycol diptyle ether, etc. are used.

Catalysts include formic acid, maleic acid, and fumaric acid.

Organic acids such as acetic acid, inorganic acids such as hydrochloric acid, phosphoric acid, nitric acid, and phosphoric acid, and alkalis such as ammonia and trimethylammonium are used. These catalysts are used in an appropriate amount depending on the amount of the alkoxysilane compound as a raw material, but preferably an alkoxysilane/compound (a tetraalkoxysilane compound represented by the general formula (I), a tetraalkoxysilane compound represented by the general formula (II) trialkoxysilane compound and dialkoxysilane compound represented by general formula (Ill)) 0.
It is used in a range of 0.001 to 0.5 mol.

The amount of water used for hydrolyzing the alkoxysilane compound is also appropriately selected, but if it is too small or too large, there will be problems such as decreased storage stability of the coating solution. Therefore, water is used as a coating solution for forming a silica-based film using an alkoxysilane compound (a tetraalkoxysilane compound represented by the general formula (I1).

It is preferably used in an amount of 0.5 to 4 mol per mol of the trialkoxysilane compound represented by the general formula (II) and the dialkoxysilane compound represented by the general formula (III).

The coating liquid of the present invention can be applied to semiconductor devices in general, and is used, for example, for interlayer insulating films, passivation films, etc. in memories, logic, etc.

A metal wiring such as aluminum is provided, and P-8iO is placed on it.
Film (silicon oxide film formed by plasma CVD method), T
E01 film (film formed from tetraethoxysilane)
etc. on a semiconductor substrate.

The coating liquid for forming a silica-based film of the present invention is applied and cured by heating to form a silica-based film on the P-8iO film or the like on the semiconductor substrate.

(Examples) The present invention will be described below with reference to Examples, but the present invention is not limited to these Examples.

Example 1 Tetramethoxysilane 509 and diethylene glycol diethyl ether 3009 were placed in a No. 11 four-bottle flask and stirred. In addition, an aqueous solution of phosphoric acid 39 dissolved in 60 G of pure water as a catalyst is prepared and slowly dropped into a flask containing tetramethoxysilane and diethylene glycol diethyl ether. During this time, stirring is continued, and the phosphoric acid aqueous solution is added dropwise over a period of 1 hour. Maximum liquid temperature is 35℃
reached. Next, methyltrimethoxysilane 659 was added, and the temperature was raised to 50° C. and held for 10 minutes. This reaction solution of alkoxysilane compound was applied to a silicon wafer and 15
After heat treatment at 0°C for 30 minutes and at 450°C for 1 hour, an infrared absorption spectrum was measured.

As a result, absorption of 84-CH3 was confirmed at 1273 cm7''.

Furthermore, 209 ml of dimethyldimethoxysilane was added.

After 10 minutes, stop heating and allow to cool.

The coating liquid for forming a silica-based film prepared by the above method was coated with a T E G (Te5t Eleme) with a step difference of 2.0 μm.
ntGroup) and heat-cured on a hot plate at 150° C. and 250° C. for 1 minute each. This was further heat-treated at 450°C for 30 minutes in a drying oven.
A silica-based film was formed. Using a scanning electron microscope, T
The thickness of the silica-based coating formed in the EG groove was estimated to be 1.9 μm, and no cracks were observed. The kinematic viscosity of this silica-based film-forming coating liquid was measured using an Ubbelohde viscometer at 25°C.
X 10-'m"/s. The coating solution for forming a silica-based film was placed in a sample bottle and maintained at 40° C. in a constant temperature bath.

Three months later, the kinematic viscosity was measured under the same conditions and found to be 4 x 10-
'm''/s.

Comparative Example 1 50 g of tetramethoxysilane, 65 g of methyltrimethoxysilane, 209 g of dimethyldimethoxysilane and 300 g of diethylene glycol diethyl ether were placed in 11.04 round flasks and stirred.

A water bath solution was prepared by dissolving 3 g of phosphoric acid in 60 g of pure water, and the solution was slowly dropped into the flask containing the alkoxysilane compound and diethylene glycol diethyl ether. During this time, stirring was continued, and the phosphoric acid aqueous solution was added dropwise over a period of 1 hour.

The liquid temperature reached a maximum of 50°C. It was further allowed to cool to room temperature.

The coating solution for forming a silica-based film prepared by the above method was applied by TEGK spin coating with a step difference of 20 μm in the same manner as in Example 1.
It was heated and cured on a hot plate at 150"C and 250°C for 1 minute each. This was then cured at 450"C in a dry base for 3 minutes.
A silica-based film was formed by heat treatment for 0 minutes. Using a scanning electron microscope.

The thickness of the silica-based coating formed in the TEG groove was estimated to be 1.9 μm, and no sick rack was observed. The kinematic viscosity of this silica-based film-forming coating liquid was measured using an Ubbelohde viscometer at 25°C.
．． It was 2×10”m”/s. A coating liquid for forming a silica-based film was put into a sample pin and kept at 40° C. in a constant temperature bath, and the sample turned into a gel after two months.

(Effects of the Invention) According to the present invention, a thick silica-based coating can be formed, and
It becomes possible to produce a coating solution for forming a silica-based film that has high storage stability. By using this silica-based film-forming coating liquid for interlayer insulating films and the like of semiconductor devices, highly reliable devices can be manufactured.

Claims (1)

[Claims] 1. Hydrolytic condensation of a tetraalkoxysilane compound represented by the general formula (I) Si(OR')_4(I) (wherein R' represents an alkyl group or an aryl group) After synthesizing a siloxane polymer, a trialkoxysilane compound represented by the general formula (II) RSi(OR')_3(II) (wherein R and R' represent an alkyl group or an aryl group) is added. Hydrolytic condensation is carried out, and further a dialkoxysilane compound represented by the general formula (III) R_2Si(OR')_2(III) (in the formula, R and R' represent an alkyl group or an aryl group) is added and hydrated. A coating liquid for forming a silica film containing a siloxane polymer obtained by decomposition and condensation polymerization. 2. Provide metal wiring, and on top of that, P-SiO film and TEOS
A method for manufacturing a semiconductor substrate on which a silica-based film is formed, by applying the coating liquid for forming a silica-based film according to claim 1 onto a semiconductor substrate on which a film or the like is formed, and curing the coating solution by heating. 3. A semiconductor device having a silica-based film obtained from the coating liquid for forming a silica-based film according to claim 1.