JP3826194B2 - Method for forming silicon oxide film by light irradiation to compound containing Si-O-Si bond - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for forming a silicon oxide film by photoirradiation of a compound containing a Si—O—Si bond for the purpose of photonics, and particularly a compound containing a Si—O—Si bond (eg, polysiloxane). The present invention relates to a film forming method in which a silicon oxide film is chemically vapor-deposited by using a gas emitted from a light source including light having a wavelength of 200 nm or less and released from the same compound, and is affected by heat effects that have been considered difficult in the past. Films can be formed on easy substrates (polymer materials, biomaterials, low-melting-point materials, heat-diffusing materials, etc.), and their uses are useful not only for electricity and electronics but also in all fields.
[0002]
[Prior art]
There are many methods for forming a silicon oxide film, but a silicon substrate is mainly installed in a high-temperature electric furnace and thermally oxidized in an atmosphere of oxygen gas, water vapor, etc. The method is roughly divided into a method of thermally decomposing a reaction gas on a heated substrate to form a film.
[0003]
[Problems to be solved by the invention]
All the conventional methods require a high temperature for forming a silicon oxide film, and therefore, the use of the substrate is limited. That is, it has been difficult to form a film on a substrate (polymer material, biomaterial, low melting point material, material that easily diffuses heat, etc.) that is easily affected by heat. When a film is formed at a low temperature, defects and impurities are mixed in the film, and it is difficult to obtain a high quality film. Furthermore, in order to form a film in an arbitrary pattern, a chemical or physical etching process is required.
[0004]
In view of the above points, the present invention provides a method for forming a silicon oxide film by light irradiation to a compound containing a Si—O—Si bond that can form a high-quality silicon oxide film free from carbon contamination at room temperature (room temperature). The purpose is to do.
[0005]
Other objects and novel features of the present invention will be clarified in embodiments described later.
[0006]
[Means for Solving the Problems]
In order to achieve the above object, a method for forming a silicon oxide film by irradiating a compound containing a Si—O—Si bond according to the invention of claim 1 of the present invention is a Si—O—Si placed in a decompressed container. A compound containing a bond is exposed to a laser ablation threshold value or less by a light source containing light having a wavelength of 200 nm or less, and is oxidized on a substrate placed in the light path of the light source using a gas released from the compound. It is characterized by chemical vapor deposition of a silicon film .
[0007]
The method for forming a silicon oxide film according to the invention of claim 2 is characterized in that, in claim 1 , the silicon oxide film is formed on the substrate at room temperature.
[0008]
The method for forming the silicon oxide film according to the invention of claim 3 is Oite to claim 1 or 2, by irradiating the substrate with light of the light source is transmitted through a mask, the silicon oxide film, the substrate A predetermined pattern is formed on the top.
The method for forming the silicon oxide film according to the invention of claim 4 is Oite to claim 1, 2 or 3, wherein the substrate is a flat substrate, inclined or disposed parallel to the optical axis of the light source It is characterized by having.
[0009]
DETAILED DESCRIPTION OF THE INVENTION
DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of a method for forming a silicon oxide film by irradiating a compound containing a Si—O—Si bond according to the present invention will be described below with reference to the drawings.
[0010]
FIG. 1 shows an embodiment of a method for forming a silicon oxide film by irradiating a compound containing a Si—O—Si bond according to the present invention with light. In this figure, reference numeral 1 denotes a vacuum container as a decompressed container, which is evacuated by a vacuum pump 2. A light transmission window 3 of MgF ₂ is formed in the vacuum container 1. In the vacuum vessel 1, an organic polysiloxane 10 (for example, plate-shaped) is disposed as a compound containing a Si—O—Si bond, and a silicon substrate 20 (substrate for depositing a silicon oxide film) is disposed. Has been. A light source 30 (including light having a wavelength of 200 nm or less) is provided outside the light transmission window 3 of MgF ₂ , and the laser light is irradiated to the organic polysiloxane 10 through the light transmission window 3 and a silicon substrate. 20 is also arranged to be irradiated. When a silicon oxide film having a predetermined pattern is formed on the silicon substrate 20, the metal mask 21 is disposed on the front side of the substrate 20.
[0011]
The reason why it is necessary to include light having a wavelength of 200 nm or less as the light irradiated to the organic polysiloxane 10 is that a gas for forming SiO ₂ cannot be generated at a wavelength exceeding 200 nm. It is necessary to include light having a wavelength of 200 nm or less that can completely remove the side chain constituting the siloxane by photocleavage. For example, a laser apparatus capable of generating laser light having a wavelength of vacuum ultraviolet or shorter can be preferably used.
[0012]
In the configuration of FIG. 1, an F ₂ laser device is used as the light source 30, an organic polysiloxane 10 is placed in a vacuum container 1 that is substantially decompressed to a vacuum, and vacuum ultraviolet F ₂ laser light (wavelength 157 nm) is applied to the surface. Irradiation was performed at an ablation threshold value (about 140 mJ / cm ² ) or less. At that time, the silicon substrate 20 having a metal mask 21 (30 μm mesh) in close contact with a part of the optical path of the F ₂ laser light was placed perpendicular to the laser light. The laser energy density on the substrate 20 at that time was about 9 mJ / cm ² , the pulse repetition frequency was 20 Hz, and the irradiation time was 15 minutes. As a result, gas (gaseous silicon compound and oxygen) is released from the exposed portion of the organic polysiloxane 10, and a silicon oxide film is formed on the silicon substrate 20 placed in the optical path of the laser beam using this gas. Chemical vapor deposition. That is, a silicon oxide film was deposited by photolysis in the vicinity of the gaseous silicon substrate 20. The chemical vapor deposition does not require heating or cooling of the silicon substrate 20 and can be performed at room temperature (normal temperature).
[0013]
FIG. 2 shows an atomic force micrograph of the silicon oxide film formed on the silicon substrate. It can be seen that the silicon oxide film is formed only on the light-irradiated portion (30 × 30 μm ² ) transmitted through the metal mask (30 μm mesh) provided in close contact with the silicon substrate, and the surface thereof is extremely smooth.
[0014]
Further, in FIG. 1, the silicon substrate 20 is disposed perpendicular to the optical axis of the laser beam, but when the silicon substrate is disposed in the optical path of the laser beam and inclined or parallel to the optical axis, A similar silicon oxide film formation was confirmed. This is advantageous when it is desired to increase the area where the silicon oxide film is formed on the silicon substrate.
[0015]
Furthermore, it was found that the same silicon oxide film can be formed even if the silicon substrate is replaced with a germanium substrate. This indicates that a silicon oxide film can be formed on a substrate made of any material.
[0016]
FIG. 3 is an analysis result of the formed film by Fourier transform infrared spectroscopy (FT-IR), and is a Fourier transform infrared absorption spectrum diagram. In FIG. 3, curve (a) is a film deposited on a silicon substrate, and curve (b) is a film deposited on a germanium substrate. In any case, an absorption peak showing a Si—O—Si bond at 1060 to 1070 cm ⁻¹ was determined. This peak position coincides with the case of the thermal silicon oxide film (SiO ₂ ). Therefore, it was found that the formed film was SiO ₂ having a stoichiometric composition.
[0017]
When the formed film was analyzed by X-ray photoelectron spectroscopy (XPS), it was found that the XPS spectrum of Si 2p had a peak at 103.2 to 103.3 eV. Also in this case, it was in agreement with the spectrum of the thermally oxidized silicon film (SiO ₂ ).
[0018]
FIG. 4 is an X-ray photoelectron spectroscopic spectrum diagram showing the analysis result in the depth direction of the formed film by XPS. The substrate is a silicon substrate. The horizontal axis in FIG. 4 is the sputtering time by argon gas (the time when the formed film is cut by sputtering; that is, the depth), and the vertical axis is the atomic concentration. The atomic concentration of oxygen and silicon in the formed film was uniform in the depth direction, and the ratio was about 2: 1. Therefore, it was found that the chemical composition of the formed film was SiO ₂ in the depth direction. Further, from the XPS spectrum of C 1s, no carbon was found in the formed film.
[0019]
In order to further confirm the presence or absence of carbon in the formed film, Raman spectroscopic analysis was performed. As a result, two broad peaks of 1350 cm ^-1 and 1580 cm ^-1 indicating the presence of carbon was observed. Therefore, it was found that the formed film was carbon-free SiO ₂ .
[0020]
According to this embodiment, the following effects can be obtained.
[0021]
(1) By exposing the organic polysiloxane 10 installed in the vacuum vessel 1 substantially depressurized to a vacuum with a light source 30 including light having a wavelength of 200 nm or less, and utilizing a gas released from the organic polysiloxane 10 A good quality silicon oxide film can be chemically deposited on the substrate placed in the optical path of the light source 30.
[0022]
(2) When the silicon oxide film is chemically deposited, it is not necessary to heat or cool the substrate, and it can be formed on a substrate at room temperature. Therefore, it is possible to form a film on a substrate (polymer material, biomaterial, low melting point material, material that easily diffuses heat, etc.) that has been conventionally difficult to be affected by heat.
[0023]
(3) A silicon oxide film having a desired pattern can be formed on the substrate by providing a mask formed with a predetermined pattern that transmits light from the light source 30 in close contact with the substrate. Therefore, a high-quality silicon oxide film for manufacturing an optical integrated circuit based on the SiO ₂ optical waveguide can be formed.
[0024]
In the embodiment of the present invention, a flat plate is shown as the substrate 20 on which the silicon oxide film is deposited in FIG. 1, but the substrate 20 is not limited to the flat substrate, and is oxidized on a substrate having a curved surface or the like. It is possible to deposit a silicon film.
[0025]
Further, the light from the light source 30 may be reflected and irradiated to the substrate side.
[0026]
Although the embodiments of the present invention have been described above, it will be obvious to those skilled in the art that the present invention is not limited to these embodiments, and various modifications and changes can be made within the scope of the claims.
[0027]
【The invention's effect】
As described above, according to the method of forming a silicon oxide film by light irradiation to a compound containing a Si—O—Si bond according to the present invention, a desired pattern can be formed on an arbitrary substrate without being limited by heat. A high-quality silicon oxide film can be formed. Since this silicon oxide film can be used to form an optical waveguide, a photonic crystal, or the like, it becomes an indispensable technique for shifting from the current integrated circuit to the future optical integrated circuit. The present invention can be used greatly in these photonics fields.
[Brief description of the drawings]
FIG. 1 is a schematic configuration diagram showing an embodiment of a method for forming a silicon oxide film by irradiating light to a compound containing a Si—O—Si bond according to the present invention.
FIG. 2 is an atomic force micrograph of a silicon oxide film patterned in a 30 μm square by simultaneously irradiating an organic polysiloxane and a silicon substrate with vacuum ultraviolet F ₂ laser light in an embodiment of the present invention. FIG.
FIG. 3 is a Fourier transform infrared absorption spectrum diagram showing the relationship between wave number and transmittance when the substrate is made of silicon and germanium in the formed film according to the embodiment of the present invention.
FIG. 4 is an X-ray photoelectron spectroscopic spectrum diagram showing the relationship between the sputtering time and the atomic concentration in the formed film for the formed film according to the embodiment of the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Vacuum container 2 Vacuum pump 3 Light transmission window 10 Organic polysiloxane 20 Silicon substrate 21 Mask 30 Light source

Claims (4)

A compound containing Si—O—Si bond placed in a decompressed container is exposed at a laser ablation threshold value or less by a light source containing light having a wavelength of 200 nm or less, and utilizing the gas released from the compound, A method of forming a silicon oxide film, comprising: chemically depositing a silicon oxide film on a substrate placed in an optical path of a light source. The method for forming a silicon oxide film according to claim 1 , wherein the silicon oxide film is formed on the substrate at room temperature. The method of forming a silicon oxide film according to claim 1 or 2 , wherein the silicon oxide film is formed in a predetermined pattern on the substrate by irradiating the substrate with light from the light source through the mask. The method for forming a silicon oxide film according to claim 1, 2 or 3 , wherein the substrate is a flat substrate, and is installed in an inclined or parallel direction with respect to the optical axis of the light source.

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