JPS6219005B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing a transparent electrode containing at least one of tin (Sn) oxide and indium (In) oxide. The purpose is to

Recently, Sn or In oxides, such as SnO ₂ and
In ₂ O ₃ and mixtures thereof have come to be widely used as electrode materials for display panels such as liquid crystals, solar cells, and transparent electrode materials for various light receiving elements. Its required properties are high light transmittance and low resistivity. The resistivity of these transparent electrode materials is determined by the extent to which excess positive atoms provide electrons as donors. Therefore, as a method of lowering the resistance of these transparent electrode materials, heat treatment in a reducing gas has conventionally been adopted. However, this method of lowering the resistance by heat treatment in a reducing gas is difficult because if the heat treatment is excessive, positive atoms precipitate and the transmittance decreases, and if the heat treatment is insufficient, the resistance cannot be lowered completely. The settings were extremely difficult. Another fatal drawback of this heat treatment method in a reducing gas is that it is necessary to raise the temperature to several hundred degrees in order to lower the resistance. Such high temperatures cannot be used to lower the resistance of samples with transparent electrodes formed on organic material substrates because the organic materials cannot withstand high temperatures. Even in batteries and photodetectors,
Such high temperatures have the disadvantage that they tend to cause deterioration in device characteristics. Therefore, it has been desired to reduce the resistance of these transparent electrodes at low temperatures.

By the way, as a method of using transparent electrodes, a method of forming transparent electrodes in a pattern is increasingly being used. In particular, with recent advances in etching technology, dry etching has come to be used instead of wet etching as an etching method that requires pattern precision. An example of the dry etching method applied to a light receiving element will be explained using FIGS. 1a, b, c, and d. Here, in the figure, 1 is a glass substrate. 2
3 is an electrode, and 3 is a heterojunction film made of ZnSe-Zn _1-x Cd _x Te. 4 is a transparent electrode made of In ₂ O ₃ or SnO ₂ or a mixture thereof. 5 is a resist for forming a pattern. The sample shown in Figure a undergoes the exposure and development process.
Patterns 6 and 7 are formed as shown in Figure b.
Next, the transparent electrode 4 is etched.
As a dry etching method, physical sputtering using an inert gas such as Ar may be used.
Further, chemical reaction sputtering may be performed using a reactive gas such as CCl ₄ . By carrying out such dry etching, a state as shown in FIG. There is a method using oxygen plasma to remove the ashed resist.
A sample having the transparent electrode pattern shown in Figure 1 is obtained. However, when the oxygen plasma is removed, the resistance of the transparent electrode 3 increases significantly from the initial value.
It's more than just a mouthful. This increased series resistance reduces the photoelectric conversion efficiency of the light receiving element. To lower the resistance of this transparent electrode, for example, at 400°C 30°C in _H2 gas.
When the heat treatment is performed for 10 minutes, the series resistance of the transparent electrode decreases, but the dark current of the heterojunction film 3 made of ZnSe-Zn _1-x Cd _x Te increases, and the S/N of the light-receiving element decreases. As described above, applying high temperature treatment to lower the resistance of a transparent electrode imposes restrictions on the substrate used, and there are various problems as a method of lowering the resistance of a transparent electrode formed on an active element.

The present invention has been made to eliminate the above-mentioned drawbacks of the conventional methods, and by sputtering a transparent electrode made of tin or indium oxide or a mixture thereof by irradiating it with inert gas plasma or reducing gas plasma. , provides a method for producing a transparent electrode with low resistance at low temperatures.

An embodiment of the present invention will be described below with reference to the drawings. FIG. 2 shows an apparatus used in one embodiment of the present invention. In the figure, 10 is a vacuum bell gear, and 11 is an exhaust system. 12 is a source of inert gas and reducing gas; needle valve 1;
The structure is such that the amount of gas supplied can be controlled by 3 or the like. 14 is a power source for generating plasma;
In the case of high frequency power supply, it has a 13.56MHz oscillator. Reference numeral 14' denotes a DC power supply that supplies an asymmetrical power wave and is inserted so that the electrode 16 side is mainly sputtered. Note that such a plasma generation power source is not limited to a high frequency power source, and may be a DC power source.
Reference numerals 15 and 16 are electrodes, and 17 is a glass substrate on which a transparent electrode 18 is formed. First, the inside of the Belgear 10 is heated to 10 ^-5 to ^{10 -6} Torr by the exhaust system 11.
exhaust to. Thereafter, by adjusting the needle valve 13 so that Ar is supplied at 10 ^-2 to 10 ^-3 Torr from the gas supply source 12, and by supplying power from the power supply 14, Ar plasma is applied to the electrodes 15, 16.
Generate in between. Transparent electrode 18 by Ar plasma
is sputtered and the resistance drops rapidly. Here, for example, the change in sheet resistance when a 1000kt thick (In ₂ O _{3 ) 0.8 (} SnO _{2 ) 0.2 film} (hereinafter referred to as an ITO film) is sputtered with Ar and H ₂ gas plasma is investigated. Shown in Figure 3. The incident power was 50 W, and after 60 seconds, when the sheet resistance had sufficiently decreased, the sputter film thickness decreased by at most 100 Å, making the ITO film 900 Å thick. Further, even with such operations, the transmittance of the transparent electrode does not decrease and remains 90% or more in the visible range. However, if the thickness of the ITO film is less than 500 Å, the stability of the sheet resistance deteriorates, so it is not preferable to perform sputtering for too long. Furthermore, the sputtering time during which the sheet resistance decreases tends to become shorter as the incident power increases. The reason why the resistance decreases due to sputtering with inert gas or reducing gas plasma is that ionized Ar ⁺ or H ⁺ enters the ITO film and selectively kills oxygen molecules in the ITO film. This is thought to be due to sputtering or by imparting a positive charge to the oxygen atoms in the ITO film, promoting the release of oxygen molecules in the ITO film.

As mentioned in the explanation of the conventional example, the manufacturing method according to the present invention is also effective as a method for reducing the resistance of an ITO film that increases due to the impact of oxygen plasma when resist is removed using oxygen plasma. After removing the resist with oxygen plasma,
The sheet resistance, which has reached 100 MΩ/hole or more, can be lowered to 200Ω/hole by introducing Ar gas and irradiating plasma in the same manner as shown in the example.

Further, according to the manufacturing method according to the present invention, by water cooling the electrode 16 shown in FIG.
For example, after sputtering for 60 seconds with Ar gas plasma, the rise in substrate temperature could be suppressed to within 35°C. Therefore, this is an extremely effective method for reducing the resistance of a transparent electrode formed on a substrate made of an organic material that cannot withstand high temperatures.

As described above, according to the present invention, a transparent electrode with low resistance can be easily obtained, and the process for obtaining a transparent electrode with low resistance can be performed at low temperature. The ability to perform the process to obtain a low-resistance transparent electrode at low temperatures is useful in many fields. For example, it is possible to reduce the resistance of transparent electrodes formed on organic materials, etc., and transparent electrodes formed on light-receiving elements and other elements that cannot withstand high temperatures. The increased resistance can be lowered by the oxygen plasma removal method of the resist, which is essential for the process.

[Brief explanation of the drawing]

Figures 1a, b, c, and d are cross-sectional views showing the transparent electrode pattern forming process, Figure 2 is a diagram showing an apparatus used in an embodiment of the present invention, and Figure 3 is an embodiment of the present invention. FIG. 3 is a diagram showing how the sheet resistance of a transparent electrode decreases due to sputtering treatment in an example. 3...Heterogeneous bonding film, 4,18...Transparent electrode, 5
...Resist, 10...Vacuum bell gear, 12...
...Gas supply source, 14...Power source for generating plasma.

Claims (1)

[Claims] 1. A step of forming a transparent electrode containing at least one of tin oxide and indium oxide on a substrate, and sputtering the transparent electrode with inert gas plasma or reducing gas plasma. A method for manufacturing a transparent electrode, comprising the step of lowering the resistance of the transparent electrode. 2. The method for manufacturing a transparent electrode according to claim 1, wherein the transparent electrode is subjected to treatment in an oxygen plasma atmosphere.