JPS5826603B2 - Plasma etching method for transparent conductive film - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an etching method using gas plasma, and particularly to etching a transparent conductive film such as indium oxide or tin oxide deposited on a glass substrate.

Transparent conductive films are mainly used for electrodes of liquid crystal display boards of electronic desktop calculators and electronic watches.

As these transparent conductive films, tin oxide films or indium oxide films containing around 10% tin are widely used, and the thickness varies from 0.5 to 2.
A uniform thin film with a thickness of 800 to 2000 Å is formed on a transparent glass plate by sputtering or vacuum evaporation.

However, the resistance value of a homogeneous tin oxide film with the same film thickness is higher than that of an indium oxide film, so indium oxide films have been mainly used until now, but there are problems with stability when creating thin films. Currently, tin oxide films, which can be produced stably industrially, are mainly used.

Conventionally, chemical etching of these transparent conductive films has been carried out using a room-temperature hydrochloric acid solution for indium oxide, and a heated hydrochloric acid solution with zinc as an additive for tin oxide. There's a problem.

First, in etching using a masking process in which a photoresist or the like is applied to a transparent conductive film, penetration into the lower part of the mask tends to occur, and erosion, so-called side etching, occurs.

In addition, in order to strengthen the adhesion of this mask to the substrate, a heat treatment called post-bake is usually performed before etching, but depending on the conditions at this time, the shape and dimensions of the pattern of this mask may be distorted, making it difficult to form a faithful pattern by etching. is harmed.

Second, because these etching solutions are strong acids, it is expensive to dispose of large amounts of waste fluid.

Thirdly, the etching solutions used are different for indium oxide and tin oxide, and in particular, the etching conditions for tin oxide require severe additive and temperature conditions, making solution management complicated.

As a method to solve these problems, CCl2F2 (
There is a method of etching a transparent conductive film using gas plasma using a fluorocarbon gas such as Freon-12), but this etching method using gas plasma has an etching effect not only on the transparent conductive film but also on the underlying glass. have

As an example, a glass substrate on which an indium oxide film was formed by vacuum evaporation was etched using Freon-12 (CC12F2) as an etching gas, and a high frequency power of 300 W was applied to a sample table with a diameter of 280 mm, and the gas pressure was 0.02 Torr.
When etched under these conditions, the etching rate of indium oxide was 200 to 300 A/mi, whereas the etching rate of the underlying glass was 300 A/mi.

Such a phenomenon causes the following inconveniences.

If the etching rate distribution within the substrate that occurs in the case of gas plasma etching is uniform, the glass surface underlying the transparent conductive film will be exposed to the gas plasma until the etched areas are finished until other unetched areas are finished. become.

As an example, when etching an indium oxide film formed by vapor deposition on a 50 x 50 ig square glass substrate with a well-polished surface, the etching time for the central part was about twice as long as for the peripheral part.

This causes the indium oxide pattern at the periphery of the substrate to stand out from the glass substrate, further causing interference fringes.

For this reason, there has been a desire for selective etching using gas plasma, which can suppress the etching rate of glass, increase the etching rate of transparent conductive films, and reduce the amount of etching on the underlying glass surface.

The purpose of the present invention is to solve problems in conventional chemical etching using chemical solutions and gas plasma etching using fluorocarbon gas, and to selectively etch a transparent conductive film on a glass substrate to form a faithful etching pattern. The purpose is to provide a method.

The present invention generates plasma gas by introducing chlorine, a hydrocarbon gas containing chlorine, or a mixed gas of these gases and air into an airtight container under reduced pressure, and exposes a transparent conductive film to the plasma to activate the A low-melting point chloride such as indium chloride or tin chloride is created through a chemical reaction with molecules such as indium oxide or tin chloride, which is evaporated and removed by a vacuum pump, thereby selectively etching transparent conductive films such as indium oxide or tin oxide. In the plasma etching method.

This invention will be explained in detail below with reference to the drawings.

FIG. 1 is a diagram showing the configuration of a plasma etching apparatus used in the present invention.

In the figure, the vacuum container 10 is a Pelger 11. It consists of a pace plate 12, and the pace plate 12 is equipped with a pump (
), a gas outlet 14 connected to a variable leak pulp 15, a high frequency electrode assembly 20, and a counter electrode 24 are attached.

The high frequency electrode assembly 20 is composed of a high frequency electrode 21, a Teflon spacer 22, and a shield 23. A high frequency power source 30 is connected to the high frequency electrode 21 so that a high frequency voltage can be applied thereto.

A substrate 26 to be etched is placed on top of the high frequency electrode 21 .

The inside of the container is evacuated by a pump, and etching gas is introduced from the gas outlet 14 to keep the pressure inside the container constant within the range of 10-2 torr to 10-ltorr. By supplying high-frequency power, discharge is caused, and the discharge is particularly strong between the high-frequency electrode 21 and the counter electrode 24.

The substrate 26 placed on the high frequency electrode 21 is etched primarily by chemically active molecules generated within the plasma.

According to Example 1 of the present invention, when etching is performed by using carbon tetrachloride gas as the etching gas and supplying 150 W of high frequency power with a frequency of 13.56 MHz to a high frequency electrode with a diameter of 280 mm, the etching rate of indium oxide is , i 501/mi, the underlying glass etching rate was IOA/rni, and the relative ratio of the indium oxide and glass etching rates was 15.

Furthermore, according to Example 2, tin oxide was etched under the same conditions as Example 1, but at the same etching rate as indium oxide.
An etching rate of mi was obtained.

Furthermore, according to Example 3, a gas mixture of carbon tetrachloride and some air was used as the etching gas at a gas pressure of 0.1 to
When etching is performed by supplying a high frequency pressure of 150 W to a high frequency electrode with a diameter of 28°, the etching rate of indium oxide is 50 A/mi, and the etching rate of the underlying glass is 1 to 2X/mi. The relative ratio of etching rates was 25 or more.

Increasing the gas pressure and mixing air during etching increases the selectivity between indium oxide and glass, which means that the etching effect on indium oxide increases.
This shows that the chemical reaction due to the active molecules of the gas plasma caused by the above-mentioned chlorine-containing gas is largely responsible.

As a result, the present invention can be applied to the etching apparatus according to another embodiment of the present invention shown in FIG.

That is, in the airtight container 50, a coil 52 is wound around the outside of a cylindrical container 51 made of quartz.

The cylindrical container 51 is equipped with an exhaust port 53 connected to a pump (not shown) and a variable leak pulp 5 for introducing etching gas.

The substrate to be processed 61 is placed on the substrate support stand 60 and the cylindrical container 51
placed inside.

A high frequency power source 70 that flows a high frequency current is connected to both ends of a coil 520 wound around the outside of the cylindrical container.

The benefits of these applications will be obvious to those skilled in the art.

[Brief explanation of drawings]

FIG. 1 is a block diagram of an embodiment according to the present invention.
0 represents a vacuum vessel, 20 represents a high frequency electrode assembly, and 30 represents a high frequency power source. FIG. 2 is a configuration diagram of a second embodiment according to the present invention, in which 50 indicates a vacuum container, 60 indicates a substrate support stand, and 70 indicates a high frequency power source.

Claims (1)

[Claims] 1. A plasma etching method for a transparent conductive film, in which a gas containing chlorine or chlorinated hydrocarbons is turned into plasma, and the transparent conductive film is etched by this plasma gas.