JP2005247678A - Method for forming silicon oxide film, and silicon oxide film - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for forming a silicon oxide film by which a silicon oxide film can be easily formed at low temperature and to provide the silicon oxide film. <P>SOLUTION: The method for forming the silicon oxide film includes a step of forming a silicone polymer film 16 on a substrate 28 and a step of converting the silicone polymer film into a silicon oxide film by irradiating the silicone polymer film with high energy rays in an oxygen atmosphere containing at least either oxygen or an oxygen compound. The silicone polymer film is polymerized by plasma polymerization of silicone monomers and/or silicone oligomers having an organosiloxane bond. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a method for forming a silicon oxide film and a silicon oxide film.

  As a method for forming a silicon oxide film, there are vapor deposition and sputtering methods, but all have poor step coverage and are not very suitable for forming a coating film on a substrate having a complicated shape. In addition, although the silicon oxide film with high purity can be obtained by the thermal oxidation method, a high temperature of 900 to 1100 ° C. is required for the thermal oxidation, and it can be deposited only on a silicon substrate having high heat resistance. At present, the chemical vapor deposition (CVD) method most used in the semiconductor industry requires a temperature of about 450 to 650 ° C., and it is difficult to deposit a silicon oxide film on a substrate having low heat resistance. In addition, a highly flammable gas such as tetraethoxysilane (TEOS) is used as a raw material, and a large facility is required.

In addition, as in the technique disclosed in Japanese Patent Laid-Open No. 6-80879, in a method for producing a silicon oxide film using a polysiloxane liquid containing a Si—O—C bond as a raw material, conversion from the polysiloxane film to the silicon oxide film is performed. In this case, not only heating at about 160 ° C. is required, but also the chemical stability of the raw material is low.
JP-A-6-80879

  An object of the present invention is to provide a silicon oxide film forming method and a silicon oxide film that can form a silicon oxide film at a low temperature and with a simple method.

The method for forming a silicone polymer film according to the present invention includes:
Forming a silicone polymer film on a substrate;
A step of changing the silicone polymer film to a silicon oxide film by irradiating the silicone polymer film with high energy rays in an oxygen-containing atmosphere containing at least one of oxygen and an oxygen compound;
including.

  According to this formation method, a silicon oxide film can be formed without heating the substrate by irradiating the silicone polymer film with high energy rays in an oxygen-containing atmosphere. As a result, a silicon oxide film can be formed not only on a substrate having high heat resistance but also on a substrate made of a material having low heat resistance, such as plastic, glass, paper, or a low melting point metal.

  In the forming method according to the present invention, the oxygen-containing atmosphere may contain oxygen or an oxygen compound, or may contain both oxygen and an oxygen compound. As the oxygen compound, water, ozone, or the like can be used.

  In the forming method according to the present invention, the high energy beam can be at least one selected from ultraviolet rays, electron beams and X-rays, and ultraviolet rays can be particularly preferably used.

  In the forming method according to the present invention, the oxygen-containing atmosphere may be an oxygen partial pressure of 0.1 Pa or more. When using an oxygen compound, the partial pressure when the oxygen compound is converted to oxygen can be adopted as the oxygen partial pressure.

  In the forming method according to the present invention, the silicone polymer film can be obtained by polymerizing a silicone monomer and / or a silicone oligomer having an organosiloxane bond (hereinafter also referred to as “silicone raw material”) by plasma polymerization.

  Even if it is heated at normal temperature or heated by the plasma polymerization, a silicone polymer film with good step coverage can be formed at a temperature of preferably 500 ° C. or lower, more preferably 250 ° C. or lower. Therefore, a silicon oxide film with good coverage can be formed even on the surface of a substrate having a complicated shape. In addition, since plasma polymerization can use a plasma polymerization apparatus having a simple configuration as compared with, for example, a CVD film forming apparatus that requires complicated piping and a temperature control device, the cost required for equipment can be reduced.

  The silicone monomer and / or silicone oligomer is preferably liquid at normal temperature. Such liquid silicone monomers and / or silicone oligomers are easy to handle when polymerized using plasma polymerization.

  In the forming method according to the present invention, the silicone monomer and / or the silicone oligomer may be at least one selected from compounds represented by the following general formula (1) and the following general formula (2).

(In the general formula (1), R _{1 to} R ₁₀ are the same or different, and each is a monovalent organic group or a hydrogen atom, and m and n are the same or different and represent an integer of 0 to 100.)

(In General Formula (2), R _{1 to} R ₈ are the same or different, and each is a monovalent organic group or a hydrogen atom, and m and n are the same or different and represent an integer of 0 to 100.)
In the general formulas (1) and (2), examples of R _{1 to} R ₁₀ include an alkyl group such as a methyl group and an ethyl group, a phenyl group, and an alkylphenyl group.

  Examples of the compound represented by the general formula (1) include octamethyltrisiloxane, hexamethyltrisiloxane, decamethylpentasiloxane, decamethyltetrasiloxane, and the like.

  Examples of the compound represented by the general formula (2) include octamethylcyclotetrasiloxane, hexamethylcyclotetrasiloxane, decamethylcyclohexasiloxane, decamethylcyclopentasiloxane and the like.

  In the forming method according to the present invention, after the silicone polymer film is formed, heat treatment can be performed at a temperature lower than a temperature at which the silicone polymer film is decomposed. By performing such heat treatment, impurities such as organic components and moisture in the obtained silicon oxide film can be more reliably removed.

  In the formation method according to the present invention, heat treatment can be performed after the silicone polymer film is changed to the silicon oxide film by irradiating the high energy beam in the oxygen-containing atmosphere. Such heat treatment can be performed, for example, at a temperature of 500 ° C. or lower, preferably 300 to 500 ° C. By performing such heat treatment, moisture and silanol groups present in the silicon oxide film can be more reliably removed.

  In the forming method according to the present invention, the silicone polymer film may be changed into a silicon oxide film in whole or in part. That is, by controlling the type, intensity, time, etc. of the high energy rays applied to the silicone polymer film, the entire silicone polymer film may be changed to a silicon oxide film depending on the application. Alternatively, only the surface, for example, the surface may be changed to a silicon oxide film.

  The silicon oxide film concerning this invention is obtained by the formation method concerning this invention mentioned above. As described above, the silicon oxide film can be formed not only on a substrate having high heat resistance but also on a substrate having low heat resistance, so that the silicon oxide film can be applied to various fields such as electronic devices and various machine parts and plastic products. .

  Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings.

1. Film Forming Apparatus and Silicone Polymer Film Forming Method First, a film forming apparatus for forming a silicone polymer film using plasma polymerization will be described.

  Film formation of the silicone polymer film by plasma polymerization is performed by, for example, a film forming apparatus 40 shown in FIG. The film forming apparatus 40 has a vacuum chamber 42 provided with a vacuum pump 52. Inside the vacuum chamber 42, a processing stage 50 for mounting the base 28 is provided below the vacuum chamber 42. The processing stage 50 is preferably formed to be temperature adjustable. In addition, a high-frequency electrode 46 is provided above the vacuum chamber 42 via an insulator 44. The high frequency electrode 46 is connected to a high frequency power supply 48.

  Further, the above-described raw material gas supply means 70 for supplying the silicone raw material and a carrier gas supply means 54 for supplying an inert gas such as argon gas are connected to the vacuum chamber 42. The raw material gas supply means 70 includes a container 56 that stores the raw material 58 and a heater 60 that heats the container 56. The container 56 is connected to the vacuum chamber 42 by a raw material supply path 66 through a flow rate control valve 62. The carrier gas supply means 54 is connected to the vacuum chamber 42 by a carrier gas supply path 64 via a flow rate control valve 62. The vacuum chamber 42 is grounded by a ground part 68.

  In such a film forming process by the film forming apparatus 40, first, the substrate 28 is placed on the processing stage 50. At this time, if the temperature of the processing stage 50 can be adjusted, the polymerization of the silicone polymer can be promoted by keeping the substrate 28 at room temperature or higher (for example, 25 to 500 ° C., preferably 25 to 250 ° C.). . Next, the inside of the vacuum chamber 42 is set to a negative pressure in order to favorably accelerate the polymerization reaction of the silicone polymer and suppress reactions other than the polymerization reaction. The pressure of the vacuum chamber 42 can be 0.1-0.2 Pa, for example.

  Using the film forming apparatus 40 set under the above conditions, a silicon polymer film is formed by a plasma polymerization reaction. As the silicone raw material 58, those existing as a liquid at normal temperature, for example, the aforementioned octamethyltrisiloxane, hexamethyltrisiloxane, or the like can be used. The silicon raw material 58 is gasified by being heated by the heater 60 and is introduced into the vacuum chamber 42 having a negative pressure through the raw material supply path 66. When the gasified raw material is introduced into the vacuum chamber 42, a heater (not shown) may be provided in the raw material supply path 66, and the raw material gas may be introduced after being heated. At the same time, argon gas is also introduced into the vacuum chamber 42 via the carrier gas supply path 64.

  Thereafter, a high-frequency voltage is applied to the inside of the vacuum chamber 42 by the high-frequency electrode 46, whereby the silicon raw material gas is ionized to become plasma and polymerized on the surface of the substrate 28, thereby forming a silicone polymer. Thus, the silicone polymer film 16 can be formed on the substrate 50 by forming the silicone polymer by plasma polymerization.

  After the silicone polymer film is formed, heat treatment can be performed at a temperature lower than the temperature at which the silicone polymer film decomposes. Specifically, the silicone polymer film formed as described above is subjected to an annealing treatment at 25 to 400 ° C. in an inert gas atmosphere such as air or nitrogen, so that the inside of the formed silicone polymer is As a result, the raw material contained in the material evaporates, impurities in the silicone polymer film are reduced, and the polymer film can be further cured.

2. Method for forming silicon oxide film By irradiating the silicone polymer film formed by the film forming method described above in ultraviolet rays with a high energy ray such as an excimer lamp in an oxygen-containing atmosphere, the polymer of the silicone polymer film is changed to silicon oxide. A film is formed. Such an oxygen-containing atmosphere may have an oxygen partial pressure of 0.1 Pa or more, and may be under atmospheric pressure, under pressure, or under reduced pressure. Such an oxygen-containing atmosphere includes, for example, oxygen and / or an oxygen compound in an inert gas such as nitrogen or argon. That is, the oxygen-containing atmosphere can contain oxygen or an oxygen compound, or may contain both oxygen and an oxygen compound. As the oxygen compound, water, ozone, or the like can be used. The oxygen-containing atmosphere may be an oxygen partial pressure of 0.1 Pa or more. When using an oxygen compound, the partial pressure when the oxygen compound is converted to oxygen can be adopted as the oxygen partial pressure. When water is used as the oxygen compound, for example, an atmosphere having a water dew point of −80 ° C. or higher can be used.

  The mechanism by which the silicone polymer is changed to silicon oxide is considered as follows. That is, oxygen molecules present in the oxygen-containing atmosphere and the film are changed to active species such as O radicals and OH radicals by high energy rays. These active species oxidize by replacing the organic groups of the silicone polymer film (for example, organic groups such as alkyl groups of silicone raw materials) with silanol groups, and the silanol groups form a siloxane bond through a dehydration reaction and crosslink. It becomes silicon.

  By performing heat treatment after irradiating high energy rays in an oxygen-containing atmosphere, moisture and silanol groups remaining in the silicon oxide film can be more reliably removed. The temperature of heat processing is 500 degrees C or less, for example, Preferably it can carry out at 300-500 degreeC. Water remaining in the film can be eliminated at about 300 ° C., and silanol groups in the film can be removed at about 500 ° C. By performing such dehydration treatment, moisture components such as moisture and silanol that are present in the silicon oxide film can be reduced, so that moisture adhering to the surface of the silicon oxide film is absorbed into the silicon oxide film. As a result, moisture absorption resistance can be imparted to the silicon oxide film. Such a silicon oxide film is suitable as an insulating film or a protective film of an electronic device, for example.

  The silicone polymer film can be entirely changed to a silicon oxide film, or only a part (for example, the surface) of the silicone polymer film can be changed to a silicon oxide film. In the former case, the silicon oxide film can be used, for example, as an insulating film of an electronic device. In the latter case, the silicon oxide film formed on the surface of the silicone polymer film is intended to make the silicone polymer film hydrophilic or hardened. It can have a function as a modified film.

3. Example 3.1. Example 1
An example in which a silicon oxide film is formed over a silicon substrate in accordance with the above film formation method will be described.

  A 5-inch CZ wafer (1 Ωcm or more, manufactured by Komatsu Electronic Metals) was used as the silicon substrate, and octamethyltrisiloxane was used as the silicone raw material.

  Plasma polymerization conditions for forming the silicone polymer film are as follows.

RF frequency: 13.56 MHz
RF output: 300W
Silicone raw material-Argon mixed gas flow rate: 60 sccm
Pressure in the chamber: 6Pa
Stage temperature: 25 ° C
In this example, the formed silicone polymer film was further annealed at 200 ° C. for 2 minutes on a hot plate. When the film thickness and average film density of the silicone polymer film formed under these conditions were evaluated using an X-ray reflectivity measuring apparatus (“ATX-G” manufactured by Rigaku Corporation), the film thickness was 204 nm and the film density was 1.25 g. / Cm ³ .

FIG. 2 shows an infrared absorption spectrum of the silicone polymer film measured using a Fourier transform infrared absorption spectrometer (“Magna 750” manufactured by Nicolet). From FIG. 2, it was confirmed that the silicone polymer film contained CH ₃ groups, Si—CH ₃ bonds, and Si—O bonds.

Next, in a nitrogen atmosphere containing oxygen, the silicone polymer film was irradiated with ultraviolet light having a wavelength of 172 nm with an excimer lamp to form a silicon oxide film. FIG. 3 shows the ultraviolet irradiation time dependence of the film thickness and the average film density. In this example, the oxygen partial pressure in the nitrogen atmosphere was 0.8 Pa. The atmospheric pressure was 101 kPa. FIG. 3 shows that the film thickness of the silicone polymer film decreases and the average film density increases as the irradiation time of ultraviolet rays increases. The average film density of the film after 90 minutes of ultraviolet irradiation was 1.90 g / cm ³ , and this average film density was confirmed to be approximately equal to the general silicon oxide density of 2.2 g / cm ³ .

FIG. 4 is an infrared absorption spectrum of the film after the silicone polymer film is irradiated with ultraviolet rays for 90 minutes. Compared with the infrared absorption spectrum of the silicone polymer film not irradiated with ultraviolet rays shown in FIG. 2, it is clear that the CH ₃ group and the Si—CH ₃ bond disappear in the spectrum shown in FIG. That is, it was confirmed that the silicon polymer film formed by plasma polymerization was irradiated with ultraviolet rays to deprive the organic group of the silicone polymer, thereby forming a silicon oxide film.

Further, FIG. 5 shows the concentration distribution in the film thickness direction of carbon and nitrogen in the film after being irradiated with ultraviolet rays for 90 minutes, measured using a secondary ion mass spectrometer (“IMS-4F” manufactured by CAMECA). The concentrations of carbon and nitrogen in the film were found to be 3 × 10 ^{19 to} 3 × 10 ²⁰ atoms / cm ³ and 5 × 10 ¹⁹ to 2 × 10 ²⁰ atoms / cm ³ , respectively. Considering that the atomic density of silica glass is 7 × 10 ²² pieces / cm ³ , the silicon oxide film obtained in this example contains only an impurity level concentration of 1 at% or less. I understood that.

  From the above examples, the following was confirmed. That is, a silicone polymer film can be formed on a substrate by polymerizing a silicone raw material by plasma polymerization. Further, the polymer film can be converted into a silicon oxide film by irradiating the silicone polymer film with ultraviolet rays in an oxygen-containing atmosphere.

3.2. Example 2
A silicone polymer film was formed on a silicon substrate having a width of 10 mm and a length of 30 mm under the same silicone raw material and plasma polymerization conditions as in Example 1.

The silicone polymer film was irradiated with ultraviolet light having a wavelength of 172 nm for 5 minutes in an air atmosphere with an excimer lamp, and then annealed. The annealing temperature was 300 ° C. and 450 ° C. The infrared absorption spectrum of the obtained film is shown in FIG. From FIG. 6, it can be seen that the CH ₃ group and Si—CH ₃ bonds remain approximately the same in both the film after the ultraviolet ray irradiation for 5 minutes and the film subjected to annealing treatment at 300 ° C. and 450 ° C. I found out. That is, it was confirmed that the silicone polymer film was partially changed to a silicon oxide film in both the film after being irradiated with ultraviolet rays for 5 minutes and the film subjected to annealing treatment at 300 ° C. and 450 ° C. It was.

  Further, from FIG. 6, in the film subjected to annealing at 300 ° C. and 450 ° C. after being irradiated with ultraviolet rays for 5 minutes, water and water are increased as the treatment temperature is increased as compared with the film after being irradiated with ultraviolet rays for 5 minutes. It is clear that silanol groups are decreasing. That is, it was confirmed that water and silanol groups remaining in the film after irradiation with ultraviolet rays were removed by the annealing treatment.

  FIG. 7 shows the red film measured before and after boiling the above-mentioned ultraviolet ray for 5 minutes and the film obtained by annealing the film at 300 ° C. and 450 ° C. in a pure water bath at 90 ° C. for 10 hours. An external absorption spectrum is shown. In FIG. 7, the graph indicated by the symbol “a” indicates the spectrum before boiling with pure water, and the graph indicated by the symbol “b” indicates the spectrum after boiling with pure water. From FIG. 7, it is clear that the amount of water contained in the film decreases as the annealing temperature increases, even after pure water boiling. This is due to the fact that water in the film and hydrophilic components such as silanol in the film were reduced by the annealing treatment after the ultraviolet irradiation, so that the water in the pure water bath was suppressed from being absorbed into the silicon oxide film. That is, the silicon oxide film could be provided with moisture absorption resistance by the annealing treatment after the ultraviolet irradiation.

  From the above examples, the following was confirmed. That is, the polymer film can be partially converted into a silicon oxide film by appropriately selecting the irradiation conditions of the ultraviolet rays that irradiate the silicone polymer film formed on the substrate by plasma polymerization from the silicone raw material. Further, the silicon oxide film can be provided with moisture absorption resistance by performing an annealing treatment on the partially formed silicon oxide film.

4). Application Examples Silicon oxide films according to the present invention include, for example, interlayer insulating films and protective films for elements such as TFTs (Thin Film Transistors) and MOSFETs, surface modification films for various electronic equipment and machine parts, and plastics such as optical parts. It can be suitably applied to surface modification films of products.

The figure which shows typically the film-forming apparatus used for plasma polymerization. The figure which shows the infrared absorption spectrum of a silicone polymer film. The figure which shows the state from which the film thickness and average film density change by ultraviolet irradiation. The figure which shows the infrared absorption spectrum of a silicon oxide film. The figure which shows the density distribution of carbon and nitrogen of a silicon oxide film. The figure which shows the infrared spectrum of the partial silicon oxide film before and behind a dehydration process. The figure which shows the infrared spectrum of the partial silicon oxide film before and behind a pure water boiling process.

Explanation of symbols

  16 silicon oxide film, 28 substrate, 40 film forming apparatus, 42 vacuum chamber, 50 processing stage, 70 source gas supply means

Claims (10)

Forming a silicone polymer film on a substrate;
A step of changing the silicone polymer film to a silicon oxide film by irradiating the silicone polymer film with high energy rays in an oxygen-containing atmosphere containing at least one of oxygen and an oxygen compound;
A method of forming a silicon oxide film. In claim 1,
The method for forming a silicon oxide film, wherein the high energy beam is at least one selected from ultraviolet rays, electron beams and X-rays. In claim 1 or 2,
The method for forming a silicon oxide film, wherein the oxygen-containing atmosphere is an atmosphere having an oxygen partial pressure of 0.1 Pa or more. In either of claims 1 or 3,
The silicone polymer film is a method for forming a silicon oxide film, in which a silicone monomer and / or a silicone oligomer having an organosiloxane bond is polymerized by plasma polymerization. In claim 4,
The method for forming a silicon oxide film, wherein the silicone monomer and / or silicone oligomer is liquid at room temperature. In claim 4 or 5,
The method for forming a silicon oxide film, wherein the silicone monomer and / or the silicone oligomer is at least one selected from compounds represented by the following general formula (1) and the following general formula (2).

(In the general formula (1), R _{1 to} R ₁₀ are the same or different, and each is a monovalent organic group or a hydrogen atom, and m and n are the same or different and represent an integer of 0 to 100.)

(In General Formula (2), R _{1 to} R ₈ are the same or different, and each is a monovalent organic group or a hydrogen atom, and m and n are the same or different and represent an integer of 0 to 100.) In any one of Claims 1 thru | or 6.
A method of forming a silicon oxide film, wherein after forming the silicone polymer film, heat treatment is performed at a temperature lower than a temperature at which the silicone polymer film decomposes. In any one of Claims 1 thru | or 7,
A method for forming a silicon oxide film, comprising performing heat treatment after changing the silicone polymer film to the silicon oxide film by irradiating the high energy beam. In any of claims 1 to 8,
The silicone polymer film is a method for forming a silicon oxide film, wherein all or part of the silicone polymer film is changed to a silicon oxide film.   A silicon oxide film formed on a substrate by the forming method according to claim 1.

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