JPS5952526A - Method for sputtering metal oxide film - Google Patents

Abstract

PURPOSE:To prevent the generation of a pinhole, by a method wherein argon gas is at first mixed in oxygen gas while plasma is generated at low voltage and only the oxygen gas is subsequently flowed to generate plasma by predetermined voltage. CONSTITUTION:After a sputtering chamber is evacuated from an exhaust port 4, argon gas and oxygen gas are flowed into from a gas inflow port 5. In this state, DC voltage is applied and the inflow of the argon gas is stopped. Thereafter, while the oxygen is succeedingly supplied, sputtering is performed to form a chromium oxide film on a glass substrate 2.

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Technical Field of the Invention The present invention relates to improvements in reactive sputtering methods for depositing metal oxide films.

('b) Prior Art and Problems As is well known, the sputtering method (hereinafter referred to as sputtering method) is often used to form thin films for electronic components, and is essential in the manufacture of semiconductor devices and resistors. It is a technology that cannot be used.

For example, photomasks used in semiconductor manufacturing are formed by patterning a thin film of a metal such as chromium (Or) or a metal oxide such as chromium oxide (Cr2O2) on a transparent substrate. Sputtering is used to deposit the thin film. The sputtering method in which the target is hit and causes a chemical reaction with plasma ions during film deposition, and the reaction product film is deposited is called reactive sputtering.
This applies when depositing the above-mentioned chromium oxide, or when depositing silicon oxide or silicon nitride.

In this type of reactive sputtering method, when oxygen (02) gas is turned into plasma and oxygen ions are collided with the target to deposit an oxide film, plasma is generated in the initial stage, but it is difficult to generate a plasma, and a high temperature is forced. A method is used to forcefully generate plasma by applying a voltage. For example, this corresponds to the case where a chromium oxide film is deposited using a direct current (DC) power type nupatsuta device, a schematic cross-sectional view of which is shown in FIG.

In the figure, l is the metal chrome plate of the target, 2 is the glass substrate of the deposited moon, and the exhaust port 4 is inside the Nubatta container 3.
The chamber is thoroughly evacuated, and oxygen gas is introduced through the gas inlet 5 so that the degree of vacuum becomes IO'' Torr.

First, the DC voltage is raised to eoov or higher to generate plasma, and as the generation begins, the voltage increases to about 500V.
Sputtering is performed by lowering the voltage to .

In this way, after depositing a chromium oxide film with a thickness of 200 to 300 people, when the surface was inspected, the diameter lμel1
Numerous pits (pinholes) occur in the front and rear,
It is a thin film with extremely rough texture.

This is because the target surface is exposed to air and a non-conducting film is formed on the surface, so it is necessary to destroy the non-conducting film first, and to do so, a high voltage is applied and the resulting abnormal discharge causes It is thought that pinholes occur.

However, the thin film with such pinholes is
This is by no means desirable, and as electronic technology advances in the future, it is expected that the number of people with scratchy membranes will increase by several hundred, so it is necessary to improve the quality of the membrane to be pinhole-free.

(C) Object of the Invention The present invention proposes a method of forming a metal oxide film free from such pinholes by reactive sputtering.

Structure of the Invention The object of the present invention is to first mix argon (Ar) gas into oxygen gas, generate plasma at a low voltage, and then introduce only oxygen gas in the reactive sputtering method for forming a metal oxide film. This can be achieved by a sputtering method in which plasma is generated at a desired voltage.

(e) Examples of the invention Hereinafter, the invention will be explained in detail using examples. Using the sputtering apparatus shown in FIG. 1, a vacuum is drawn through the exhaust port 4, and then argon gas and oxygen gas are introduced through the gas inlet 4 as shown in the chart shown in FIG. That is, argon gas is 2
ntll 7 minutes, oxygen gas flows for 12 m61 minutes, and when a DC 1fi pressure of 850 V is applied, plasma is generated in just 1 second. The DC voltage was gradually increased while the inflow gas was left as it was for several seconds, and at the same time a D'C voltage of 500 cm was applied, the inflow of argon gas was stopped. Thereafter, sputtering is carried out with the oxygen gas at 12 Ll/min and the DC voltage at 500 mm, and a chromium oxide film with a thickness of 200 mm can be formed on the glass substrate z in 30 to 35 seconds.

During this time, the degree of vacuum is constantly maintained at 1O-3 Torr.

When the chromium oxide film deposited in this manner was detected, a thin chromium oxide film was found in which no pinholes were observed. This means that no abnormal discharge occurred during initial plasma generation.

The above is just one example, but when depositing a metal oxide film by reactive sputtering, the inflowing gas is not only oxygen gas, but also other gases such as nitrogen gas mixed into the oxygen gas. Similarly, by initially mixing argon gas, plasma can be generated at a low voltage, resulting in a similarly soft plasma generation method.

(g) Effects of the Invention Accordingly, according to the present invention, a very thin metal oxide film, for example, a thin film of about 300 layers, can be formed with extremely high quality, which contributes to improving the performance of electronic components.

Although the above embodiment has been explained using a chromium oxide thin film, it is of course applicable to sputtering methods for other metal thin films.

[Brief explanation of the drawing]

FIG. 1 is a schematic cross-sectional view of a sputtering apparatus, and FIG. 2 is a time chart of the Nubatta ring method according to the present invention. In the figure, 1 is the target (metallic chromium), 2 is the glass substrate,
8 is a vacuum container, 4 is an exhaust port, and 5 is a gas inlet.

Claims (1)

[Claims] In the reactive sputtering method, in which oxygen gas is introduced, oxygen plasma is generated, and the plasma collides with the target to form an oxide film made of the metal of the target material. Argon gas is first mixed into the oxygen gas, and then the plasma is sputtered at a low voltage. 1. A method for sputtering a metal p-oxide film, comprising the steps of generating plasma, then introducing only oxygen gas, and generating an oxygen beam plasma at a desired voltage.