JPH0340920A - Production of thin zirconia film - Google Patents

Abstract

PURPOSE:To improve adhesive strength by carrying out decomposition by a chemical vapor deposition process at a specific temp. or below by using Zr alkoxide as raw material. CONSTITUTION:As a carrier gas, an inert gas, etc., such as Ar, are regulated to about 100cc/min by means of a mass flow controller 6b and supplied to a vaporizer 10. On the other hand, Ar gas flow is regulated to about 5l/min by means of a mass flow controller 6a in a pipe 7a. By the above procedures, a gaseous mixture of the vapor of Zr alkoxide, such as Zr tertiary butoxide, and Ar is further diluted with Ar regulated to about 5l/min and is then introduced via a pipe 7c and a nozzle 5 into a reaction vessel 1. Subsequently, mirror-finished substrates 4 made of SUS304, etc., in the reaction vessel 1 are heated to <=500 deg.C and pressure in the vessel 1 is maintained at about 75Torr to carry out film formation for about 1hr, by which transparent cubic ZrO2 films of 10-20mg are deposited on the substrates 4, respectively.

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to a method for manufacturing a zirconia thin film.

[Prior art and issues] As is well known, zirconia has a high melting point and is used as a high-temperature material, but pure zirconia undergoes a transition from a low-temperature monoclinic crystal to a tetragonal crystal at approximately 1000°C, and this dislocation occurs. Destruction occurs from the volume change during . Therefore, it is used as stabilized zirconia or partially stabilized zirconia in which the high-temperature cubic crystal is stabilized over a wide temperature range by adding yttrium (Y), calcium (Ca), or the like.

By the way, even when making zirconia into a thin film, a stabilizer is added if the product is used at high temperatures. When creating a zirconia thin film using the vapor phase chemical reaction method (CVD), which is one of the thin film forming technologies, a reaction using zirconium and a stabilizer halide as raw materials is generally used. Approximately 1000 as reaction temperature
Requires high temperature of ℃. Further, there is a problem that corrosive gas is generated as a reaction by-product and corrodes the device and the substrate.

For this reason, CVD using an organic zirconium compound and an organic compound as a stabilizer, which can be decomposed at low temperatures and do not generate corrosive gas, has been attempted. As such organic compounds, a group of compounds called β-diketone complexes, typified by acetylacetone complexes, are used. In addition, zirconium alkoxides are used as other organic compounds (Jour
nal of Crystal Crows Volume 74 4
09 p. 1986).

However, although studies have been conducted using such zirconia organic compounds, all of these studies have aimed at stabilized zirconia films to which stabilizers have been added.

However, few organic compounds such as Y and Ca that are raw materials for stabilizers have high vapor pressures, and special measures are required to vaporize them when used in vapor phase chemical vapor deposition.

Furthermore, in vapor phase chemical deposition of oxide thin films including zirconia, single crystals such as silicon, quartz, etc. are used as substrates. When a metal substrate is used, since there is a large difference in coefficient of thermal expansion between the metal and the oxide, there is a risk that the film will peel off due to internal stress in the film.

The present invention has been made in view of the above circumstances, and it is an object of the present invention to provide a zirconia thin film that is stable over a wide temperature range and can be formed with good adhesion on a metal substrate, and a method for manufacturing the same.

[Means for Solving the Problems] The first invention of the present application is a method for producing a zirconia thin film, characterized in that a cubic zirconia thin film to which no stabilizer is added is heat-treated at a high temperature.

In the first invention of the present application, the heat treatment temperature needs to be 500° C. or higher. This is because at temperatures below 500° C., no transition to cubic crystals occurs, or even if the transition occurs, the rate is extremely slow and impractical.

The second invention of the present application is a method for producing a zirconia thin film, which is characterized by using a zirconium alkoxide as a raw material and decomposing it at 500° C. or lower in a chemical vapor deposition method.

Examples of the zirconium alkoxide according to the second invention of the present application include zirconium ethoxide, zirconium isoprooxide, and zirconium tert-butoxide, but when used in chemical vapor deposition, zirconium tert-butoxide has a high vapor pressure. preferable. When zirconium tertiary butoxide is used, a decomposition reaction occurs from about 250°C, but at temperatures above 500°C, monoclinic or tetragonal zirconia, which is a stable phase, grows, which is not preferable.

Regarding the decomposition reaction of the alkoxide of zirconium tert-butoxide, a thermal decomposition reaction of this compound alone,
Alternatively, it includes an oxidative decomposition reaction in which an oxidizing agent such as oxygen is added to the raw material, or a hydrolysis reaction in which water vapor is added.

When the above-mentioned zirconium alkoxide is used as a raw material by chemical vapor deposition, the gases to be mixed include inert gases such as nitrogen, argon, and helium, reducing gases such as hydrogen,
Single or mixed gases such as oxygen, carbon dioxide, or oxidizing gases such as water vapor are used.

When the above reaction is carried out by chemical vapor deposition, normal pressure or reduced pressure conditions are used.

Examples of the substrate for producing the zirconia thin film by chemical vapor deposition include sintered ceramics, single crystals such as silicon, amorphous materials such as glass, and metals such as stainless steel.

[Function] In the zirconia thin film according to the first invention of the present application, since no stabilizer is added to the cubic zirconia thin film serving as the base, dislocation to monoclinic, tetragonal, and cubic crystals occurs due to an increase in temperature; The membrane does not break due to volume changes during the process.

This is probably because the structure of the film created by chemical vapor deposition is different from that of a sintered body, and stress during phase transition does not act inside the film. This means that even when a metal with a thermal expansion coefficient significantly different from that of zirconia is used as a substrate, the film does not peel off, and it has great practical value as a surface modification of metal materials.

Although the zirconia thin film produced according to the second invention of the present application was produced at a low temperature, it becomes a cubic zirconia that exists stably at a temperature of 2000° C. or higher (this can be confirmed by X-ray diffraction). This seems to be related to the decomposition mechanism of alkoxide compounds.

The Journal of Crystal shown earlier
Crows Vol. 74, p. 409, published in 1986, also conducted a reaction of zirconium tert-butoxide alone, but the precipitates there were tetragonal or monoclinic.

[Example] An embodiment of the present invention will be described below.

First, a film forming apparatus used in the method of the present invention will be explained with reference to FIG.

1 in the figure is a reaction container. A susceptor 3 containing a heater 2 is disposed within the reaction vessel 1 . This susceptor 3 is designed to rotate as indicated by an arrow X in the figure. A plurality of substrates 4 are placed on the susceptor 3 directly below the nozzles described below. The substrate 4 is heated to a predetermined temperature.

A nozzle 4 is attached to the upper part of the reaction vessel 1, and the nozzle 4 is connected to a first pipe 7a to which a mass flow controller 6a is attached and a mass flow controller 6b.

A second pipe 7b to which a valve 8a is attached is communicated via a third pipe 7C. The mass flow controller 6b
A vaporizer 10 containing zirconium tert-butoxide is provided in the bypass pipe 9 of the second pipe 7b on the downstream side of the pipe 7b via valves 8b and 8c.

This vaporizer IO is maintained at, for example, 90° C. by a constant temperature bath 11.

A vacuum pump 14 is connected to the exhaust hole 12 of the reaction vessel 1 via an exhaust line 13 . This vacuum pump (
4, the reaction gas is exhausted. Here, exhaust line 1
By mixing nitrogen with the exhaust gas during step 3, the exhaust speed is adjusted and the pressure inside the reaction vessel 1 is maintained at a constant pressure.

Next, the method of the present invention using the above film forming apparatus will be explained. That is, first, the valve 8a of the second pipe 7b is "closed," and the valves 8b and 8c of the bypass line 9 are each "opened."

Next, Ar gas as a carrier gas is transferred to the mass controller 6.
Adjust the flow rate to 100 cc per minute using b and supply it to the vaporizer IO. On the other hand, the mass flow controller 6a of the first pipe 7a
Then, A' gas is adjusted to 5 g per minute. As a result, the mixed gas of zirconium tert-butoxide vapor and argon is further diluted with Ar gas adjusted to 5 p per minute, and the third pipe 7e, nozzle 5 The substrate 4 in the reaction container 1 is heated at, for example, 350°C.
Heat to. Here, as the substrate 4, for example, 20 meters
Corning 70 with size x 20mnX 2 +nm
59 glass, SUS 304, Mo, and mirror-polished SUS 304 were used. Further, the pressure inside the reaction vessel 1 was maintained at 75 Torr.

When the film was formed for 1 hour under these conditions, 10 to 201 g of a white film was deposited on each substrate, but a transparent film was obtained especially on the mirror-polished SUS 304. As a result of X-ray diffraction, it was confirmed that all the films on each substrate were cubic zirconia.

Further, for the sample using MO as a substrate, a similar film was further formed on the back surface to cover the entire surface, and then heat treatment was performed in air at 1300° C. for 3 hours in an annular furnace. No peeling was observed in the sample after heat treatment. As a result of X-ray diffraction, it was confirmed that it was monoclinic zirconia. This sample was further heated to 1400°C for 1 hour in a circular furnace and heated to 900°C.
I repeated the 1 hour heat cycle 5 times and returned to room temperature.
No peeling of the film was observed.

[Effects of the Invention] As detailed above, the present invention provides a zirconia thin film that is stable over a wide temperature range, can be formed with good adhesion on metal substrates, and can be used as a heat-resistant protective film for metals or as an optical film. We can provide a manufacturing method.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram of a film forming apparatus used in the present invention. DESCRIPTION OF SYMBOLS 1... Reaction container, 2... Heater, 3... Susceptor, 4... M plate, 5... Nozzle, 8a, 6b... Mass flow controller, 7a, 7b, 7cm=piping, 8a, l1lb, 8cm...bulb, lO...
Vaporizer, IL... constant temperature bath, 12... exhaust hole, 14.
··Vacuum pump.

Claims (2)

[Claims] (1) A method for producing a zirconia thin film, which comprises heat-treating a cubic zirconia thin film without adding a stabilizer at a high temperature. (2) A method for producing a zirconia thin film, which comprises using zirconium alkoxide as a raw material and decomposing it at 500° C. or lower in a chemical vapor deposition method.