JP2931963B2 - Thin film formation method using alkoxide as raw material - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for forming a thin film using an alkoxide as a raw material. INDUSTRIAL APPLICABILITY The thin film forming method of the present invention can be suitably used for forming an antireflection film on the surface of a cathode ray tube of a television, doping of a functional organic substance, manufacturing a photocatalyst, forming a fine pattern film, and thinning a photosensitive material. .

[0002]

2. Description of the Related Art As is well known, alkoxide is used as a raw material for forming a metal oxide thin film such as an amorphous silicon (a-SiO ₂ ) film or a siloxane polymer film or an organic metal compound polymer thin film.

[0003] The alkoxide used for this raw material is a highly volatile liquid, and it has heretofore been impossible to coat it on a substrate. Therefore, conventionally, a sol-gel method or an ozone oxidation method has been used as a thin film manufacturing technique using an alkoxide.

The sol-gel method is a method in which an aqueous solution obtained by hydrolyzing an alkoxide is applied to a substrate, dried and sintered to obtain an oxide film. However, this method has the disadvantages of cracking the film during the drying and sintering processes and a high temperature process. In the case of this sol-gel method, since the raw material is an aqueous solution, the raw material solution often does not adhere to the substrate. In contrast, the adhesion has been increased by chemical treatment of the substrate surface.

[0005]

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a method for forming a thin film using an alkoxide as a raw material, which has a high quality by a different reaction mechanism. It is an object of the present invention to provide a method capable of reliably obtaining a thin film of

[0006]

SUMMARY OF THE INVENTION The present invention comprises a step of applying a raw material alkoxide non-aqueous solution on a substrate and, at the same time, making the raw material viscous, and a step of thinning the viscous raw material coating film obtained in the above step by a photo-induced reaction. And a step of forming

[0007] In the step of making the raw material coating film viscous, the substrate surface is activated by irradiating the substrate surface with excitation light to react with the raw material solution. At this stage, the coating is still a partially bonded viscous material, unlike an oxide film.

In the thinning step, when the high-viscosity polymer is irradiated with ultraviolet light, a photo-induced condensation polymerization reaction occurs,
The organic group in the alkoxide is eliminated, and a polymer film or an oxide thin film firmly bonded to the substrate is obtained.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A first embodiment of a thin film forming method using an alkoxide as a raw material according to the present invention is a method of forming a thin film having a viscosity of
Irradiates the substrate with excitation light to activate the substrate surface.
After that, the raw material alkoxide is adhered to the substrate surface.
This allows the raw material alkoxide to be adsorbed on the substrate surface
And a step of making the mixture viscous,
The raw material coating film is irradiated with excitation light, and the coating film is subjected to a light reaction.
It is characterized in that it is a step of thinning .

According to a second embodiment of the present invention, in the first embodiment, the excitation light used in the coating viscosity-imparting step has a wavelength shorter than 300 nm and a photon energy of 4.1 eV. It is characterized by the above.

According to a third embodiment of the present invention, the coating film is selectively formed by selecting the wavelength of the excitation light used in the coating film thinning step in the first embodiment. It is characterized by being a body or an oxide.

According to a fourth embodiment of the present invention, in the third embodiment, the excitation light used in the film thinning step has a wavelength shorter than 200 nm and a photon energy of 6.2 eV. It is characterized by the above.

[0013]

EXAMPLES Examples of the present invention will be described below, but the following examples are merely examples for suitably describing the present invention, and do not limit the present invention in any way.

Example 1 As shown in FIG. 1A, a xenon excimer lamp light 2 (having a spectrum of 15
(5 nm to 200 nm) for 15 minutes in a nitrogen atmosphere. Thereafter, as shown in FIG. 1B, tetramethyloxysilane (TMOS) is used as a raw material alkoxide.
Three drops of a stock solution 3 containing 91.83% of a TMOS monomer, 3.32% of a TMOS oligomer, and 4.84% of water / methanol were applied by spin coating. As shown in FIG. 1C, the raw material solution applied to the portion of the substrate 1 irradiated with the excitation light became a viscous coating film 3a and was adsorbed on the substrate surface. On the other hand, the raw material alkoxide solution attached to the portion of the substrate surface where the excitation light was not irradiated volatilized without leaving any trace in a few minutes.

Next, as shown in FIG. 1D, this sample was excited by a xenon excimer lamp light 4. As shown in FIG. 1E, when the infrared absorption measurement of the thin film 30 formed on the substrate 1 was performed, (i) disappearance of the methyl group,
(Ii) The appearance of a peak attributed to a-SiO ₂ was confirmed.

Hereinafter, the infrared absorption measurement will be described with reference to FIG.
This will be described in more detail with reference to the infrared spectrum shown in FIG.

The spectrum a in FIG. 2 is an infrared absorption spectrum of the substrate activated by the excitation light, which is spin-coated with TMOS and passed for 5 minutes. The spectrum already differs from that of the source TMOS. It can be seen that polymerization occurred within 5 minutes of the adhesion, and the TMOS was changed to a surface-adhered viscous substance.

The spectrum b in FIG. 2 is an infrared absorption spectrum obtained by irradiating the viscous coating (surface-attached polymer) with 1 × 10 ¹⁹ / cm ² of xenon excimer lamp light as the number of photons. Although the spectrum changes,
also different from the a-SiO _2. The peak attributable to the methyl group still remains clearly.

The spectrum c in FIG. 2 shows that the viscous coating film has a photon count of 4 × 10 ¹⁹ / xenon excimer lamp light.
It is an infrared absorption spectrum but was cm ² irradiation.
Although the intensity of the methyl group is significantly reduced, a-
Not SiO ₂ .

The spectrum d shown in FIG. 2 shows that the xenon excimer lamp light was applied to the viscous coating film in a number of photons of 1.2 × 10
^{20 is} an infrared absorption spectrum of the sample irradiated with ²⁰ / cm ² . The peaks attributed to methyl groups and C—H bonds have completely disappeared. This means that there is little residual organic matter. Further, a peak (800 cm ⁻¹ ) attributed to Si—O—Si appears, and the shape of the spectrum is the same as that of a-SiO ₂ . Spectrum e in FIG.
Is a silicon thermal oxide film (most popular as a semiconductor insulating film) placed for comparison.

FIG. 3 is an infrared absorption spectrum showing the irradiation wavelength (photon energy) dependence of the viscous coating.
The quasi-monochromatic synchrotron radiation from the undulator was used as the irradiation light source. Spectrum a is immediately after TMOS coating, spectrum b is irradiated with 5 eV light, and spectrum c is 7.
2eV light irradiation, spectrum d is 12.9 eV light irradiation, and spectrum e is an infrared absorption spectrum by 14.1 eV light irradiation. From these spectra, it can be seen that the higher the photon energy, the better the efficiency of thinning (forming an oxide film). Here, the peak at 1150 cm ⁻¹ is C—O—
C (in MeOMe) due to stretching vibration.

Example 2 In Example 1, tetramethyloxysilane was used as a raw material, and a silicon wafer was used as a substrate. In Example 2, the following raw materials and a substrate were used in the same manner. According to the procedure, a thin film was formed on the substrate. As the excitation light, synchrotron radiation from an undulator and excimer lamp light were used.

(Type of Raw Material Solution) The reaction between the substrate surface and the raw material solution is performed by silicon-based alkoxide (tetramethyloxysilane (TMOS), tetraethyloxysilane (TEOS)), germanium-based alkoxide, and titanium-based alkoxide. Performed on a substrate. A xenon excimer lamp was used as a light source. As a result, it was found that all the raw material liquids adhered firmly to the substrate subjected to the xenon excimer lamp light irradiation treatment, and formed a surface-adhered viscous substance (viscous coating film). Therefore, it was found that any alkoxide raw material reacts with the surface.

(Types of Substrates) Silicon substrates, a-SiO ₂ substrates, glass substrates, plastic substrates, acrylic substrates, vinyl chloride substrates, ceramics
Porcelain substrate, aluminum metal substrate, copper metal substrate, PMM
The test was performed with the A substrate and fine particles of these materials. As a result, it was found that alkoxide was attached to both. On the other hand, the alkoxide volatilized in a few minutes in the portion not irradiated with light, and no residue was left on the surface.

(Wavelength Selectivity) The experiment was performed with both excitation light of excimer lamp light and synchrotron radiation. As a result, it was found that the surface was activated by light having a wavelength of 300 nm or less. Also, 300n
Even if the wavelength is longer than m, a laser can use a multiphoton reaction such as a two-photon or three-photon reaction.

(Regarding Light-Induced Surface Activation) After irradiating a silicon substrate with excimer lamp light, an ESR
(Electron spin resonance) measurement was performed. As a result, it was found that a high concentration of radical species (Pb center by a common name) was generated on the surface by light induction. This substrate has TMO
After performing ESR measurement after spin coating of the S stock solution, the Pb center on the substrate completely disappeared, and methyl radical was detected. This fact means that the radical species on the photo-generated silicon surface is causing a “radical polymerization reaction” that acts as an “initiator” in polymer chemistry.

(Lifetime of Radicals Generated on Substrate Surface) The lifetime of radicals (Pb center) generated on the substrate surface was evaluated by ESR. As a result, it was found that almost one day after the irradiation, the light disappeared. Therefore, it is desirable to coat the raw material solution as soon as possible after the substrate is irradiated with the excitation light.

The resulting thin film did not fall off when scratched with metal.

[0029]

The raw material alkoxide adheres only to the portion of the substrate irradiated with the excitation light, so that a fine pattern can be formed.

[Brief description of the drawings]

FIG. 1 is a process diagram showing a basic configuration of the present invention;
FIG. 1B is a diagram showing a state where a substrate is irradiated with a xenon excimer lamp light, FIG. 2B is a diagram showing a state where a raw material alkoxide solution is spin-coated on the substrate, and FIG. FIG. 4D is a view showing a state in which the substrate on which the coating film is formed is irradiated with xenon excimer lamp light, and FIG. 4E is a view showing a substrate on which a thin film is formed by irradiation with excitation light.

FIG. 2 is a diagram showing an infrared absorption spectrum of a thin film after spin-coating TMOS on a substrate activated by excitation light, where spectrum a is the spectrum of the coating film after 5 minutes, and spectra b and c. , D are the spectra of the thin film after irradiating the coating with a xenon excimer lamp,
The irradiation dose increases in the order of c and d. The spectrum e is the spectrum of the silicon thermal oxide film and is shown for comparison.

FIG. 3 is a diagram showing an infrared absorption spectrum representing the irradiation wavelength dependence of thinning, where spectrum a is an infrared absorption spectrum immediately after TMOS coating, spectrum b is an infrared absorption spectrum after 5 eV light irradiation, and spectrum c is 7. 2
The infrared absorption spectrum after irradiation with eV light, the spectrum d is the infrared absorption spectrum after irradiation with 12.9 eV light, and the spectrum e is the infrared absorption spectrum after irradiation with 14.1 eV light.

[Explanation of symbols]

Reference Signs List 1 silicon wafer (substrate) 2 excimer lamp light (excitation light) 3 undiluted solution of tetramethyloxysilane (raw alkoxide) 3a viscous coating film 4 excimer lamp light (excitation light) 30 thin film

Claims (4)

(57) [Claims] A substrate is irradiated with excitation light to activate the substrate surface.
And then apply the raw material alkoxide to the substrate surface.
The alkoxide on the substrate surface.
And viscous, and
Excitation light is applied to the viscous raw material coating, and the coating is irradiated with light.
A method of forming a thin film using an alkoxide as a raw material, the method comprising a step of forming a thin film by a method. 2. The method according to claim 1, wherein the excitation light used in the coating film viscosifying step is:
The method according to claim 1 , wherein the wavelength is photon energy of 300 nm or more. 3. By selecting the wavelength of the excitation light used for the coating film thinning step, thin film according to claim 1, characterized in that the selective polymer material or an oxide of the coating film Forming method. 4. The excitation light used in the film thinning step,
The photon energy has a wavelength of 200 nm or more, and the energy when the coating film is a complete oxide thin film is 14 e.
4. The method according to claim 3 , wherein the voltage is V or more.