JP3229419B2 - 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 for forming a silicon oxide film on a substrate surface, and more particularly to a method for forming a dense ceramic oxide film having no cracks and pinholes on the substrate surface.

[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 and an interlayer insulating film for the purpose of insulating and flattening between wirings are formed on the surface of the semiconductor device as the circuit is multi-layered.

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: , A method using inorganic SOG (spin-on-glass), a method using organic SOG, and a method using hydrogen silsesquioxane resin (JP-A-3-18367)
No. 5).

However, if the silicon oxide film formed by inorganic SOG has a thickness of more than 0.3 μm, cracks occur. Therefore, it is necessary to repeatedly coat a device substrate having irregularities of 1 μm or more in order to fill the steps. In addition, since the film itself has poor flattening ability, a flattening step by etch back after forming the film was necessary. In addition, organic SO
The silicon oxide film formed by G can form a film having a thickness of 1 μm or more without cracks in a single coating, but like the inorganic SOG, the film itself has poor flattening ability. A flattening step by post-etchback is required, especially because the coating has functional groups such as silanol groups and alkoxy groups, the film quality is not dense,
In particular, since it has an organic functional group such as an alkoxy group, when it is subjected to oxygen plasma treatment, there is a problem that carbon poisoning (carbon contamination) occurs due to volatilization of the organic functional group. In the method proposed in JP-A-3-183675, 0.8 μm (8000 Å) is used.
A silicon oxide film having the above thickness could not be formed, and overcoating was necessary to fill the steps of a device substrate having irregularities of 1 μm or more, like inorganic SOG.

Further, when a silicon oxide film formed on a device substrate by a conventional method is subjected to plasma etching with a haloalkane gas in a contact hole forming step, the etching rate of the silicon oxide film and that of a plasma CVD film are reduced. Therefore, there is a problem that a contact hole having a good shape cannot be formed. The present inventors have studied the above problem and found that in the plasma etching treatment using a haloalkane gas, the difference between the etching rate of the silicon oxide film and that of the plasma CVD film is caused by the denseness of these silicon oxide films. .

[0006]

The inventors of the present invention have conducted intensive studies to solve the above-mentioned problems, and as a result, have found that a film containing a specific silicon resin as a main component can be formed under a gas atmosphere containing 20% by volume or more of oxygen gas. By heating, a method for forming a dense ceramic silicon oxide film having no cracks and pinholes and having a similar etching rate to a film without plasma CVD during a plasma etching process using a haloalkane gas was found, The present invention has been reached.

That is, an object of the present invention is to provide a method for forming a dense ceramic silicon oxide film having no cracks and pinholes on the surface of a substrate.

[0008]

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
The present invention relates to a method for forming a silicon oxide film, which comprises heating the film in a gas atmosphere containing 20% by volume or more of oxygen gas to convert the film into a ceramic silicon oxide film.

Hereinafter, 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 substrate 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 if 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, so that after the film formation, This is because sufficient etching resistance cannot be obtained in the oxygen plasma treatment 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 water 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 of forming a film containing the above-mentioned silicon resin as the main component on the surface of the base material. Specifically, this method includes, for example, adding the liquid silicon resin or the silicon resin to 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.

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.

Then, 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 20% by volume or more of oxygen gas to form a dense ceramic silicon oxide film. Can be. This is achieved by heating the substrate on which the coating containing the silicon resin as a main component is formed under a gas atmosphere in which the concentration of oxygen gas in the heating atmosphere gas is 20% by volume or more or substantially under an oxygen gas atmosphere. A dense ceramic silicon oxide film can be obtained, and the obtained ceramic silicon oxide film is subjected to plasma etching using a mixed gas of 90% by volume of tetrafluoromethane and 10% by volume of oxygen gas.
The inventors have found that the etching rate is almost the same as that of the plasma CVD film, and have achieved the present invention. 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 desirable to heat at a temperature of 100 ° C. or higher for 30 minutes or more, more preferably at a temperature of 300 ° C. or higher, 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 of 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 spectrometer 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.

[0019]

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 synthesized according to the following Reference Examples, but the method for synthesizing the silicon resin is not limited to the following Reference Examples. In addition,
The conditions of the plasma etching are as follows.

Plasma etching conditions: A substrate having a silicon oxide film formed on its surface is inserted into a parallel electrode type reactive ion etching apparatus, and tetrafluoromethane 45 is added.
Plasma etching was performed using a mixed gas of sccm and oxygen 5 sccm at a reaction pressure of 3.2 pa, a frequency of a high-frequency power supply of 13.56 MHz, a power per unit area of 0.24 W / cm ² , and an etching time of 3 minutes. When the plasma CVD film was subjected to plasma etching under these conditions, the etching rate was 500 Å / min. Met.

[0021]

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 having the following structural formula. [H (CH ₃ ) ₂ SiO _1/2 ] _0.35 (SiO _4/2 ) _1.0

Further, 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 solid film having a thickness of about 1 μm. The structure of this film was analyzed using a Fourier transform infrared spectrometer in transmission mode. A broad strong absorption peak derived from a siloxane bond was observed at about 1100 cm ⁻¹ , and 1260 cm ^−1.
Sharp, strong absorption peak assigned to the Si-CH ₃ group, a sharp, strong absorption peak assigned to the SiH groups 910 cm ^-1 and 21 50cm ^-1, 2870cm ^- sharp weak absorption peak derived from the alkoxy group in ^1, 2
A sharp moderate absorption peak derived from the CH group was observed at 960 cm ^-1 and a broad moderate absorption peak derived from the silanol group was observed near 3500 cm ^-1 . When solution A was sealed and stored at room temperature in a 125 ml high-density polyethylene wide-mouth bottle, no visual change such as a change in viscosity was observed after one month, the number average molecular weight was 6260, and the weight average molecular weight was 9890, the degree of dispersion is 1.
58.

[0023]

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 1.32 μm. After forming the film, the semiconductor device substrate was inserted into a cylindrical annular furnace, heated at 400 ° C. for 1 hour in an oxygen gas atmosphere, and then gradually cooled to a room temperature in an oxygen gas atmosphere. When the characteristics of the silicon oxide film formed on the semiconductor device substrate were measured, the maximum thickness was 1.10 μm, and the irregularities on the semiconductor device surface 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 the transmission mode, the peak of the SiH group in the silicon oxide film (910 cm ^{−1) was obtained.}
And 2150 cm ^-1 ), the peak of the silanol group (35
00cm ^-1 ) and the peak of the alkoxy group (287
0 cm ^-1 ) was completely disappeared. Further, it was confirmed that the obtained silicon oxide film was insoluble in organic solvents such as MIBK and acetone. Next, the silicon oxide film was plasma-etched under the above conditions. The etching rate of the silicon oxide film is 650 Å / min. This was 1.3 times the etching rate of the plasma CVD film under the same conditions.

[0024]

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 1.35 μm. 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. When the characteristics of the silicon oxide film formed on the semiconductor device substrate were measured, the maximum thickness was 1.15 μm, and the irregularities on the semiconductor device surface 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, it was found that S
iH group peaks (910 cm ^-1 and 2150c
m ^-1 ), peak of silanol group (around 3500 cm ^-1 )
Also, it was confirmed that the peak of the alkoxy group (2870 cm ^-1 ) had completely disappeared. Further, it was confirmed that the obtained silicon oxide film was insoluble in organic solvents such as MIBK and acetone. Next, the silicon oxide film was plasma-etched under the above conditions. The etching rate of the silicon oxide film is 730 angstroms / mi.
n. This was 1.46 times the etching rate of the plasma CVD film under the same conditions.

[0025]

EXAMPLE 3 Reference Example 1 the following structure was prepared in the same manner as in _{formula: [H (CH 3) 2} SiO 1/2] 1.0 30 wt% of the silicone resin represented by [SiO _{4/2] 1.0} - The MIBK solution was spin-coated on a semiconductor device substrate (step 1.0 μm) to form a silicon resin film having a maximum thickness of 1.35 μm. After forming the film, the semiconductor device substrate was inserted into a cylindrical annular furnace, heated at 400 ° C. for 1 hour in an oxygen gas atmosphere, and then gradually cooled to a room temperature in an oxygen gas atmosphere. When the characteristics of the silicon oxide film formed on the semiconductor device substrate were measured, the maximum thickness was 1.11 μm,
The irregularities on the surface of the semiconductor device were 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 peak (910) of the SiH group in the silicon oxide film was found.
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. Next, the silicon oxide film was plasma-etched under the above conditions. The etching rate of the silicon oxide film is 70
0 angstroms / min. This was 1.4 times the etching rate of the plasma CVD film under the same conditions.

[0026]

Comparative Example 1 An organic SOG (trade name: OCD-type7) manufactured by Tokyo Ohka Kogyo Co., Ltd. was used for a semiconductor device substrate (step 1.
0 μm) to form a silicon resin film having a maximum thickness of 0.72 μm. After forming the film, the semiconductor device substrate is inserted into a cylindrical annular furnace, and is heated at 400 ° C. in air.
For 1 hour, and then gradually cooled in air to cool to room temperature. When the characteristics of the silicon oxide film formed on the semiconductor device substrate were measured, the silicon oxide film had a maximum thickness of 0.56 μm, and as a result of microscopic observation, it was confirmed that the silicon oxide film had no cracks or pinholes. Structural analysis was performed using a Fourier transform infrared spectrometer in a transmission mode, and a peak of a silanol group (around 3500 cm ⁻¹ ) was obtained.
And the peak of the alkoxy group (2870 cm ^-1 ) were both confirmed. 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. Next, the silicon oxide film was plasma-etched under the above conditions. The etching rate of the silicon oxide film is 12
40 angstroms / min. Which is 2.48 times the etching rate of the plasma CVD film under the same conditions.
It was twice.

[0027]

[0028]

The method for forming a silicon oxide film of the present invention has a feature that a dense ceramic silicon oxide film having no cracks and pinholes can be formed.

──────────────────────────────────────────────────続 き Continuing 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 Chikami Coast, 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-6-236872 (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, comprising heating the film in a gas atmosphere containing 20% by volume or more of oxygen gas to convert the film into a ceramic silicon oxide film.