JP3229418B2 - Method for forming silicon oxide film - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of forming a silicon oxide film on the surface of a substrate, and more particularly, to a method of forming a thick film having no cracks and pinholes on the surface of the substrate and insoluble in an organic solvent. The present invention relates to a method for forming a silicon oxide film.

[0002]

2. Description of the Related Art Generally, a protective film is formed on a surface of a substrate to protect the surface of the substrate. In particular, in the electric and electronic industries, with the recent increase in the degree of integration and multilayering of semiconductor devices, the complexity of semiconductor devices and the unevenness of the surface of semiconductor devices have become remarkable. To protect against electrical damage, electrostatic damage, ionic contamination, nonionic contamination and radiation contamination,
And for the purpose of flattening irregularities on the semiconductor device surface,
A passivation film or an interlayer insulating film for the purpose of insulating and flattening between wirings is formed on the surface of a semiconductor device as a multilayer of a circuit is formed.

As a passivation film and an interlayer insulating film formed on the surface of a semiconductor device, a silicon oxide film is generally used. Examples of a method for forming a silicon oxide film on a semiconductor device surface include a CVD (chemical vapor deposition) method and a spin coating method. Examples of a method for forming a silicon oxide film on a semiconductor device surface by a spin coating method include: , Inorganic SOG (spin on glass) and organic SOG.

However, a silicon oxide film formed by inorganic SOG causes cracks when the film thickness exceeds 0.3 μm. Therefore, in order to fill a step on a device substrate having irregularities of 1 μm or more, overcoating is required. And, in particular,
Since the film itself has poor flattening ability, a flattening step by etch back after the film formation was necessary.

On the other hand, a silicon oxide film formed by organic SOG can form a film having a thickness of 1 μm or more without cracks in a single application, but like the inorganic SOG, the film itself has a flattening ability. Therefore, a flattening step by etch back after the formation of the film was required. Further, since a large amount of silanol groups and alkoxy groups remain in the silicon oxide film, the hygroscopicity is high, and a problem of carbon poison (carbon contamination) due to the remaining alkoxy groups occurs during the oxygen plasma treatment. There was a problem that electrical reliability was poor.

[0006] Therefore, as a method of improving the problem of the silicon oxide film formed by the inorganic SOG and the organic SOG, for example, a method of forming a silicon oxide film by using hydrogen silsesquioxane has been proposed (Japanese Patent Laid-Open Publication No. HEI 9-26186). 3-18
No. 3675). This method does not require an etch-back step because the resin itself is heated and melted and has excellent ability to flatten a step. Further, since there is no organic group in the structural unit, there is an advantage that there is no fear of carbon poison during oxygen plasma treatment.

However, in the method of forming a silicon oxide film proposed in Japanese Patent Application Laid-Open No. 3-183675, 0.8 μm
(8000 angstroms) or more, it is impossible to form a silicon oxide film having a thickness of more than (8000 angstroms). There is a problem that it cannot be flattened. Further, when an attempt is made to obtain a thick silicon oxide film by this method, cracks and pinholes may be generated in the silicon oxide film, and there has been a problem that the reliability of the semiconductor device is significantly reduced.

[0008]

DISCLOSURE OF THE INVENTION The present inventors have developed a film containing a silicon resin as a main component in an amount of 0 to 20% by volume of oxygen gas.
(However, 20% by volume is not included.) By heating and melting in a gas atmosphere containing 1 μm or more, a step of 1 μm or more on the substrate is flattened, and cracks and pinholes are eliminated.
a silicon oxide film having a thickness far exceeding μm, and having no silanol group or alkoxy group which causes moisture absorption and carbon poison in the formed silicon oxide film, and which is insoluble in an organic solvent. The present inventors have intensively studied a method of forming a GaN layer, and have finally reached the present invention.

That is, an object of the present invention is to provide a method for forming a ceramic silicon oxide film which is insoluble in an organic solvent and which is thick and has no cracks and pinholes on the surface of a substrate.

[0010]

Means for Solving the Problems and Action Thereof The present invention relates to a method for producing a compound of the formula: (HR ₂ SiO _1/2 ) _X (SiO _4/2 ) _1.0 (where R is a hydrogen atom, alkyl X is a group selected from the group consisting of a group and an aryl group, wherein X is 0.1 ≦ X ≦
2.0. A) forming a film mainly comprising the silicon resin represented by
A method for forming a silicon oxide film, characterized by heating in a gas atmosphere containing 0 to 20% by volume of oxygen gas (but not including 20% by volume) to convert the film into a ceramic silicon oxide film. About.

The method for forming a silicon oxide film of the present invention will be described in detail.

In the present invention, the coating on the surface of the base material is mainly composed of a silicon resin represented by the general formula: (HR ₂ SiO _1/2 ) _x (SiO _4/2 ) _1.0 . In the above formula, R is a group selected from the group consisting of a hydrogen atom, an alkyl group and an aryl group, and specific examples of the alkyl group of R include a methyl group, an ethyl group, a propyl group and a butyl group; As the aryl group for R, a phenyl group, a tolyl group,
An xylyl group is exemplified, and preferably, R is a methyl group or a phenyl group. In the above formula, X is 0.1 ≦ X ≦
2.0, preferably 0.2 ≦ X ≦ 1.0.
This is because, when X is less than 0.1, the silicon resin tends to gel when synthesizing it, and even if it does not gel during synthesis, the resin itself tends to have a high molecular weight during storage in a solution state. When X exceeds 2.0, sufficient film hardness of the silicon oxide film cannot be obtained or the organic group content in the silicon resin becomes relatively large. This is because sufficient etching resistance cannot be obtained in the oxygen plasma processing step.

Although the molecular weight of such a silicon resin is not particularly limited, it is preferable that the resin has a weight-average molecular weight in order to exhibit the property of flattening a step of a semiconductor device substrate by melting and flowing at the time of heating. 100,
000 or less, and its physical properties such as viscosity and softening point are not particularly limited, but the softening point is preferably 400 ° C. or less.

The method for producing such a silicon resin is not particularly limited. For example, pure silicon is dissolved in alcohol, and a mixed solution of tetraalkoxysilane and dimethylmonochlorosilane is added dropwise to the solution. And a method in which 1,1,3,3-tetramethyldisiloxane is dissolved in a cosolvent of alcohol and hydrochloric acid, and tetraalkoxysilane is added dropwise to form the silicon resin. Can be

In the present invention, the coating on the surface of the base material comprises the above-mentioned silicon resin as a main component, and other components are not particularly limited.
Platinum compounds such as chloroplatinic acid, complexes of platinum and alkenes, complexes of platinum and vinylsiloxane, alcohol solutions of chloroplatinic acid; acidic catalysts such as hydrochloric acid and acetic acid; alcohols such as methanol and ethanol; The low molecular siloxane which has is illustrated.

In the present invention, there is no particular limitation on the method for forming a film containing the above-mentioned silicon resin as a main component on the surface of a substrate, and specifically, this method includes the step of converting the liquid silicon resin or the silicon resin into an organic solvent. Spin-coat or spray the solution resulting from the dissolution, or dipping the substrate into the silicon resin or the solution, and then remove the solvent as necessary to form a film containing the silicon resin as the main component on the substrate surface Or a method in which the silicon resin in a solid state at room temperature is heated and softened on a substrate to form a film mainly composed of the silicon resin on the surface of the substrate. In the former method, the organic solvent used for dissolving the silicon resin is not particularly limited as long as it can uniformly dissolve the silicon resin, and specific examples of such an organic solvent include methanol, Alcohol solvents such as ethanol; cellosolve solvents such as methyl cellosolve and ethyl cellosolve; ketone solvents such as methyl ethyl ketone and methyl isobutyl ketone; butyl acetate, isoamyl acetate;
Ester solvents such as methyl cellosolve acetate and ethyl cellosolve acetate; chain siloxanes such as 1,1,1,3,3,3-hexamethyldisiloxane and 1,1,3,3-tetramethyldisiloxane; 1,3,3,3
Examples include silicone solvents such as cyclic siloxanes such as 5,5,7,7-octamethyltetracyclosiloxane and 1,3,5,7-tetramethyltetracyclosiloxane, and silane compounds such as tetramethylsilane and dimethyldiethylsilane. Further, two or more of the above organic solvents can be used in combination.

Further, in the present invention, the substrate for forming a film containing the above-mentioned silicon resin as a main component is not particularly limited, and specific examples of such a substrate include a glass substrate,
Examples include a ceramic substrate, a metal substrate, and a semiconductor device, and a semiconductor device is particularly preferable. Such a semiconductor device may have irregularities on the surface. According to the method for forming a silicon oxide film of the present invention, such irregularities on the surface of the semiconductor device can be flattened.

Next, the substrate on which the coating containing the above-mentioned silicon resin as a main component is formed is heated in a gas atmosphere containing 0 to 20% by volume (but not 20% by volume) of oxygen gas. A ceramic silicon oxide film can be formed. This is achieved by heating the substrate on which the coating mainly composed of the silicon resin is formed under a gas atmosphere in which the concentration of oxygen gas in the heating atmosphere gas is less than 20% by volume or substantially does not contain oxygen gas. It has been found that the cross-link density of the ceramic silicon oxide film can be sufficiently controlled, and in particular, the internal stress of the obtained ceramic silicon oxide film can be sufficiently relaxed, whereby the film thickness far exceeds 1 μm. And a ceramic silicon oxide film free of cracks and pinholes was able to be formed. In the present invention, the gas other than the oxygen gas in the heating atmosphere gas is not particularly limited, but may be an inert gas with respect to the silicon oxide film or the silicon resin film in the process of forming the ceramic silicon oxide film. Preferably, specific examples of such a gas include a nitrogen gas, an argon gas, and a helium gas. In the present invention, the temperature and the heating time for heating the substrate on which the coating containing the silicon resin as the main component is formed are not particularly limited, but preferably, the conditions under which the coating containing the silicon resin as the main component is insolubilized in a solvent, for example, It is preferable to heat at a temperature of 100 ° C. or more for 30 minutes or more, more preferably at a temperature of 300 ° C. or more, in which SiH groups, silanol groups and alkoxy groups hardly remain in the formed silicon oxide film. It is desirable to heat for 30 minutes or more.

In the method for forming a silicon oxide film of the present invention, as a method for confirming whether or not a ceramic silicon oxide film can be formed, a silicon resin formed on a substrate surface by an infrared spectrophotometer is used as a base material. SiH groups (910 cm ^-1 and 2150 cm ^-1)
A sharp strong absorption peak derived from an SiH group, an alkoxy group (a sharp weak absorption peak derived from an alkoxy group at 2870 cm ^-1 ) and a silanol group (35
It can be confirmed by measuring the content of each of the broad medium absorption peaks derived from silanol groups around 00 cm ^-1 and then measuring and comparing those of the silicon oxide film after heating. . In addition, the silicon oxide film after heating can be immersed in various organic solvents, and it can be confirmed whether the silicon oxide film is insoluble in the organic solvent.

According to the method for forming a silicon oxide film of the present invention, a ceramic silicon oxide film having a thickness of 1 μm or more can be formed without generating cracks and pinholes. By adjusting the content, the internal stress of the resulting ceramic silicon oxide film can be reduced. Furthermore, according to the method for forming a silicon oxide film of the present invention, a ceramic silicon oxide film can be formed at a temperature much lower than the melting point of aluminum, so that aluminum used for circuit wiring of a semiconductor device is melted. Since the silicon oxide film is not deteriorated, the method for forming a silicon oxide film of the present invention is useful as a method for forming a passivation film and an interlayer insulating film on the surface of a semiconductor device. Since a silicon oxide film and an organic resin film can be further formed, it is useful as a method for forming an interlayer insulating film of a multilayer semiconductor device.

[0021]

EXAMPLES The present invention will be described in detail with reference examples, examples and comparative examples. The silicon resin used in the present invention was prepared according to the following Reference Examples, but the method for synthesizing the silicon resin is not limited to the following Reference Examples.

[0022]

REFERENCE EXAMPLE 1 40 g of methanol and 19.0 g of water were weighed into a 200 ml-four-necked flask equipped with a dropping tube with a straight tube, a coiled condenser and a thermometer, and cooled with ice to lower the liquid temperature to 2 ° C. or lower. The system was lowered and nitrogen was passed through the system at a very small flow rate. While stirring the solution in this state, a mixture of 13.2 g (0.14 mol) of dimethylchlorosilane and 60.8 g (0.4 mol) of methyl orthosilicate was dropped from the straight dropping tube over 40 minutes. On the way, the liquid temperature was 13 due to heat generation.
° C, but dropped to 8 ° C at the end of the dropping.
After further stirring for 15 minutes in an ice-cooled state, the mixture was stirred at room temperature for 4 hours. The reaction solution was colorless and transparent. Next, 200 ml of methyl isobutyl ketone (hereinafter abbreviated as MIBK) was added to the reaction solution, and 200 ml of water was further added. The lower layer was collected, 100 ml of MIBK was added thereto, and the mixture was shaken, followed by phase separation. The upper layer was collected and combined with the upper layer. When 400 ml of water was added and shaken, the mixture became emulsified. 700 ml of diethyl ether was added and the mixture was allowed to stand, and the phases were separated (approximately 1
0 hours). The upper layer was collected, magnesium sulfate was added thereto, and the mixture was allowed to stand for 6 hours. Thereafter, the magnesium sulfate was separated by filtration, and the filtrate was collected (hereinafter, this filtrate was filtrate A).
Call. ). The filtrate A was weighed on an aluminum dish, and the solid content% by weight was determined to be 6.35%. Next, filtrate A
Was weighed in a high-density polyethylene wide-mouthed bottle in an amount of 125 milliliters, and was blown with nitrogen to obtain a solid content% by weight.
= 30.3%. At this time, the odor of diethyl ether or methanol could not be detected from the concentrate. A predetermined amount of MIBK was added to this concentrate to dilute it to 30.0% by weight of solid content (hereinafter, this solution is referred to as solution A). The solution A was directly diluted in tetrahydrofuran to prepare a solution having a solid concentration of 0.2% by weight, and the solution was injected into a gel permeation chromatography using tetrahydrofuran as a carrier solvent. 6260, the weight average molecular weight was 9890, and the degree of dispersion was 1.58.
As a result of ²⁹ Si-nuclear magnetic resonance spectrum analysis, this dissolved component was confirmed to be a silicon resin represented by the following structural formula. [H (CH ₃ ) ₂ SiO _1/2 ] _0.35 (SiO _4/2 ) _1.0

The solution A was dropped on a silicon wafer and allowed to stand at room temperature in the air to dry the solvent, thereby forming a film having a solid content of about 1 μm. The structure of this film was analyzed by a Fourier transform infrared spectrometer in transmission mode. A broad strong absorption peak derived from a siloxane bond near 1100 cm ⁻¹ and a sharp strong peak derived from a Si—CH ₃ group at 1260 cm ^−1. Absorption peak,
910 cm ^-1 and from SiH groups 2150 cm ^-1 sharp strong absorption peaks, sharp weak absorption peak derived from the alkoxy group to 2870cm ^-1, 2960
sharp medium absorption peak derived from C-H groups in cm ^-1, absorption peaks moderate broad derived from silanol group near 3500 cm ^-1 was observed. Solution A
When sealed and stored at room temperature in a 25-ml high-density polyethylene wide-mouth bottle, no visual change such as a change in viscosity was observed after one month, and the number average molecular weight was 62.
60, the weight average molecular weight was 9890, and the dispersity was 1.58.

[0024]

Example 1 The solution A prepared in Reference Example 1 was spin-coated on a semiconductor device substrate (step difference: 1.0 μm) to form a silicon resin film having a maximum thickness of 1.60 μm. After forming the film, insert this semiconductor device substrate into a cylindrical annular furnace,
In a nitrogen gas atmosphere, heated at 400 ° C. for 1 hour,
The mixture was gradually cooled in a nitrogen gas atmosphere and cooled to room temperature. When the characteristics of the ceramic silicon oxide film formed on the semiconductor device substrate were measured, the maximum thickness was 1.39 μm,
The irregularities on the surface of the semiconductor device were evenly flattened.
As a result of microscopic observation, it was confirmed that the silicon oxide film had no crack and no pinhole. When the structure was analyzed by a Fourier transform infrared spectrometer in transmission mode, the peak of the SiH group in the silicon oxide film (91
0 cm ^-1 and 2150 cm ^-1), the peak of the silanol groups (3500 cm ^-1 vicinity) and peak alkoxy groups (2870cm ^-1) was confirmed to be lost completely any. Further, the obtained silicon oxide film was prepared by using MIB
It was confirmed that it was insoluble in organic solvents such as K and acetone.

[0025]

Example 2 The solution A prepared in Reference Example 1 was spin-coated on a semiconductor device substrate (step difference: 1.0 μm) to form a silicon resin film having a maximum thickness of 1.52 μm. After forming the film, the semiconductor device substrate is inserted into a cylindrical annular furnace, and heated at 400 ° C. for 1 hour in a mixed gas atmosphere composed of 10% by volume of oxygen gas and 90% by volume of nitrogen gas.
The mixture was gradually cooled under the mixed gas atmosphere and cooled to room temperature. When the characteristics of the ceramic silicon oxide film formed on the semiconductor device substrate were measured, the maximum thickness was 1.32 μm, and the unevenness of the semiconductor device surface was uniformly flattened. As a result of microscopic observation, it was confirmed that the silicon oxide film had no crack and no pinhole. When the structure was analyzed by a Fourier transform infrared spectrometer in transmission mode, the peaks of the SiH group (910 cm ^-1 and 2150 cm ^-1 ), the peak of the silanol group (around 3500 cm ^-1 ), and the alkoxy It was confirmed that all of the group peaks (2870 cm ^-1 ) completely disappeared. Also, the obtained silicon oxide film is
It was confirmed that it was insoluble in organic solvents such as MIBK and acetone.

[0026]

Example 3 30% by weight of a silicon resin represented by the structural formula: [H (CH ₃ ) ₂ SiO _1/2 ] _1.0 (SiO _4/2 ) _1.0 prepared by the same method as in Reference Example 1-MIBK The solution was spin-coated on a semiconductor device substrate (step 1.0 μm) to form a silicon resin film having a maximum thickness of 2.40 μm. After forming the film, the semiconductor device substrate was inserted into a cylindrical annular furnace and heated at 400 ° C. for 1 hour in a nitrogen gas atmosphere, and then gradually cooled to a room temperature in a nitrogen gas atmosphere. When the characteristics of the ceramic silicon oxide film formed on the semiconductor device substrate were measured, the maximum thickness was 1.96.
μm, and the unevenness on the surface of the semiconductor device was uniformly flattened. As a result of microscopic observation, it was confirmed that the silicon oxide film had no crack and no pinhole. When the structure was analyzed by a Fourier transform infrared spectrometer in transmission mode, the peaks of the SiH group (910 cm ^-1 and 2150 cm ^-1 ), the peak of the silanol group (around 3500 cm ^-1 ), and the alkoxy It was confirmed that all of the group peaks (2870 cm ^-1 ) completely disappeared. Further, it was confirmed that the obtained silicon oxide film was insoluble in organic solvents such as MIBK and acetone.

[0027]

Comparative Example 1 Inorganic SOG (trade name: OCD-type II) manufactured by Tokyo Ohka Kogyo Co., Ltd. was spin-coated on a semiconductor device substrate (step difference: 1.0 μm), and the maximum thickness was 0.55 μm.
m of resin coating was formed. After forming the film, the semiconductor device substrate was inserted into a cylindrical annular furnace, heated in air at 400 ° C. for 1 hour, and then gradually cooled in air and cooled to room temperature. An attempt was made to measure the characteristics of the silicon oxide film formed on the semiconductor device substrate. However, many cracks were observed with the naked eye, and the film thickness could not be measured.

[0028]

Comparative Example 2 Hydrogen silsesquioxane was dissolved in MIBK solution to prepare a 30% by weight solution. This solution is spin-coated on a semiconductor device substrate (step difference 1.0 μm),
A silicon resin film having a maximum thickness of 1.15 μm was formed. After forming the film, the semiconductor device substrate was inserted into a cylindrical annular furnace, heated in air at 400 ° C. for 1 hour, and then gradually cooled in air and cooled to room temperature. Although the maximum thickness of the silicon oxide film formed on the semiconductor device substrate was 0.98 μm, observation with a microscope confirmed that a large number of microcracks had occurred in the silicon oxide film.

[0029]

[0030]

According to the method for forming a silicon oxide film of the present invention, it is possible to form a thick silicon oxide film having no cracks and pinholes on the surface of a substrate and insoluble in an organic solvent. Having.

──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Takashi Nakamura 2-2 Chikusa Beach, Ichihara City, Chiba Prefecture Toray Dow Corning Silicone Co., Ltd. Research and Development Headquarters (72) Inventor Katsutoshi Mine Chikusa Beach, Ichihara City, Chiba Prefecture No.2 Toray Dow Corning Silicone Co., Ltd. Research and Development Division (56) References JP-A-1-108109 (JP, A) JP-A-5-86330 (JP, A) JP-A-6-240455 (JP, A) Patent 3188772 (JP, B2) (58) Fields investigated (Int. Cl. ⁷ , DB name) C01B 33/12 C08G 77/02 C09D 183/05 H01L 21/312-21/316

Claims (1)

(57) [Claims] 1. The method according to claim 1, wherein on the surface of the substrate, a general formula: (HR ₂ SiO _1/2 ) _X (SiO _4/2 ) _1.0 (wherein, R is selected from the group consisting of hydrogen, alkyl and aryl X is 0.1 ≦ X ≦
2.0. A) forming a film mainly comprising the silicon resin represented by
A method for forming a silicon oxide film, characterized by heating in a gas atmosphere containing 0 to 20% by volume of oxygen gas (but not including 20% by volume) to convert the film into a ceramic silicon oxide film. .