JPH0455328A - Production of glass thin film - Google Patents

Abstract

PURPOSE:To enable production of a thick film having no defect by combining the production of functional glass by sol-gel method and the production of thin films by sputtering. CONSTITUTION:A mixture soln. is prepared by adding water and alcohol to metal alkoxide expressed by the general formula M(OR)4 (wherein M is metal and R is alkyl group) and further adding a functional inorg. material. This mixture soln. is hydrolyzed and polymerized by dehydration condensation to synthesize a bulk glass. Then, by using this bulk glass as a target for sputtering, a glass thin film having the same compsn. as that of the bulk glass is formed on a substrate. By this method, the bulk glass can be obtained without subjecting to high temp. process so that no influence is given to the various kinds of dopants to be added. By forming thin films by sputtering, the compsn. of thin films does not change and thereby, film thickness can precisely be controlled. Defects such as cracks or peeling are hardly caused even when the film is made thick.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a method for producing a glass thin film used for optical waveguides and the like.

[Conventional technology]

Glass materials have excellent light transmittance and weather resistance, and are useful as optical materials. In particular, glasses with high optical functionality are synthesized by adding various dopant materials. Typical examples include laser glass that has laser oscillation characteristics by doping with rare earth elements such as neodymium and erbium, and nonlinear optical glass doped with semiconductor particles such as cadmium sulfide and copper chloride.

As methods for synthesizing such glass, the melt method and the sol-gel method are used on board.

When the melt method is used, as in the case of synthesizing silica glass, for example, a high temperature of 2000° C. or higher may be required, which tends to affect the added dopant material in various ways. On the other hand, when using the sol-gel method, the above-mentioned silica glass
It can be synthesized at a relatively low temperature of about 200°C. Therefore, even if a substance cannot be added due to decomposition or phase separation in a high temperature range, it is possible to synthesize a glass containing this substance using the sol-gel method.

By the way, when producing integrated optical components such as a guiding waveguide using glass with high optical functionality as described above, thinning the glass is an indispensable technique. Therefore, it is considered to be an effective method not only for synthesis but also for thin film formation.
Sol-gel methods have been used.

The general method for forming thin films using this sol-gel method is as follows:
For example, "Ceramic Industry Association Magazine" 90, (6) 9.328-3B
2 (1982), first, ethyl silicate, titanium isopropoxide and ethanol,
Water and hydrochloric acid as a catalyst are added and stirred to prepare a hydrolysis solution, ie, a coating solution. Next, the substrate to be coated is immersed in this solution and pulled up at a constant speed to form a film on the surface of the U plate, followed by drying and heating steps to produce a glass film.

Since film formation using this sol-gel method goes through a solution, it is relatively easy to uniformly coat the entire surface of large substrates, and the film has new functions such as mechanical and chemical protection and optical properties. It is useful as a coating method.

[Problem to be solved by the invention]

In the aforementioned sol-gel method, a transparent and uniform coating film with a film thickness of 0.1 μm to 0.3 μm is obtained, but if an attempt is made to increase the film thickness beyond this, cracks may occur on the coating film. , defects such as white clouding and peeling from the substrate may occur. Therefore, in order to prevent these defects from occurring, attempts were made to thicken the film by adding glycerin or ethyl ether as thickeners.
The maximum film thickness that can be formed is 0.5 μm at most.

Therefore, the film thickness required for optical components such as optical waveguides is 5 to 1.
There was a problem in that it was unsuitable for producing a glass thin film of about 0 μm.

The present invention is intended to solve such problems.

[Means to solve the problem]

The present invention adds water and alcohol to a metal alkoxide, and also adds a functional inorganic material to form a mixed liquid,
A first step of synthesizing bulk glass through hydrolysis and dehydration condensation, and a second step of producing a glass thin film having the same composition as the bulk glass by sputtering the synthesized bulk glass onto a target. It is characterized by

[Effect]

According to the present invention, since bulk glass is obtained without going through a high-temperature process, it has almost no effect on the various dopants added. There is little change in the composition during oxidation, the film thickness can be tightly controlled, and defects such as cracks and peeling are less likely to occur even when the film is thickened.

〔Example〕

Next, an example of the method for producing a glass thin film according to the present invention will be described.

First, in order to synthesize bulk glass, water, alcohol, and a catalyst are added to metal alkoxide, mixed, and hydrolyzed. As the metal alkoxide, those whose metal moieties are titanium, aluminum, germanium, or boron, and whose alkyl groups are methyl, ethyl, propyl, or butyl groups can be used.

1 to 3 metal alkoxides having the above functional groups.
It is also possible to use both types at the same time.

Next, a functional inorganic material is added to this mixed solution.

As the additive material, rare earth elements having a laser oscillation function such as neodymium and erbium, or semiconductor fine particles exhibiting a nonlinear optical effect such as cadmium sulfide and copper chloride are suitable.

This mixed solution is allowed to stand at around room temperature to gel, and then is gradually heated to undergo dehydration condensation. After reaching a certain temperature, the temperature increase is stopped and the already gelled mixture is turned into transparent glass while maintaining that temperature.

By using the bulk glass obtained through the above process as a target material and using a high frequency sputtering method, a thin film can be formed on any substrate. In this sputtering method, ions activated by a discharge phenomenon collide with the aforementioned target material and atoms of the target material are knocked out, and the film deposition rate is proportional to the discharge power.
The atoms attach to the substrate one by one and are deposited. Therefore, the thickness of the formed thin film can be controlled by sputtering time, sputtering conditions, and the like.

Here, a concrete example of the implementation will be explained.

First, 200ml of silicon alkoxide is used as the metal alkoxide, 200ml of water, 400ml of ethanol, and 7200ml of 0.1N7 are added and stirred for 30 minutes. Next, 2 g of erbium chloride, which is a rare earth compound, is added as a functional inorganic material to the mixed solution, and the mixture is further stirred for 30 minutes.

Thereafter, this mixed solution is transferred to a Teflon container, sealed with aluminum tape, and then gelled at 35°C. After gelatinization, the temperature was raised to 80"C over three days, and several IIIlφ holes were made in the aluminum tape to dry it. After drying for about two weeks, the temperature was raised to 1200°C at a heating rate of 1°C/min. The glass is heated and held for 1 hour to form transparent glass.The resulting glass has a disk shape with an outer diameter of 10 cm and a thickness of 0.5 cm.

Using this glass plate as a target material and using silica glass as a substrate, a thin film was formed by high frequency sputtering. As a result, a film with a thickness of approximately 5 μm was produced without defects such as cracks and peeling.

〔Effect of the invention〕

As explained above, the present invention provides a method for producing a glass thin film with excellent optical functions by combining the production of functional glass using the sol-gel method and the thin film forming technology using the sputtering method, and provides a method for producing a glass thin film with excellent optical functions. It is effective when used as a material.

Claims (1)

[Claims] 1. Water and alcohol are added to a metal alkoxide represented by the general formula M(OR)_4 (wherein M represents a metal and R represents an alkyl group), and a functional inorganic material is also added. a first step of synthesizing bulk glass by hydrolyzing and dehydrating and condensing the mixed liquid; and a second step of forming a glass thin film. 2. The method for producing a glass thin film according to claim 1, wherein the functional inorganic material in the first step is a rare earth element having a laser oscillation function or a semiconductor fine particle exhibiting a nonlinear optical effect. 3. The metal of the metal alkoxide in the first step is at least one of silicon, titanium, aluminum, germanium, and boron, and the alkyl group is at least one of a methyl group, an ethyl group, a propyl group, and a butyl group. Claim 1 characterized in that a product is used.
The method for producing the described glass thin film.