JPS61203136A - Formation of transparent electroconductive film - Google Patents

Abstract

PURPOSE:To obtain the titled film which can find utility in a wide variety of substrates excellent in transparency, electric conductivity, mechanical strength and physical strength, by plasma-polymerizing tetramethyltin and a specified oxygen-containing gas. CONSTITUTION:Tetramethyltin and a gas containing at least 20% oxygen at least ten times the weight of the tetramethyltin are fed through valves 10, 11 and 12 to a plasma reaction vessel 2, wherein they are converted into plasmas by applying 0.05-0.7W/cm<2> high-frequency voltage on the order of kHz to MHz by means of an electric source 1 and an electrode 3 of an output of 1W/cm<2> and polymerized for at least one min at 10<-3>-10<0>Torr to form a plasma polymer film 4 on a base 5, such as a glass plate with a smooth surface, at a temperature of room - 200 deg.C.

Description

Detailed Description of the Invention (Industrial Application Field) The present invention relates to a transparent conductive film, and more specifically, a transparent conductive film is formed on a substrate by turning a gas containing tetramethyltin and at least 10 times the amount of oxygen into plasma. The present invention relates to a method of forming a conductive film.

(Prior art) A transparent conductive thin film mainly composed of tin oxide forms a film on glass or ceramic, and is useful as a transparent electrode in the field of electronics due to its chemical stability, physical stability, mechanical strength, etc. It has certain characteristics.

Conventional techniques for forming this transparent conductive thin film include physical vapor deposition (PVD) and chemical vapor deposition (CVD). For the former, vacuum evaporation method and sputtering method (plasma sputtering) are used.

The main and important ones are ion sputtering) and plasma CVD, the latter being chemical production methods (spray method,
There are two methods: immersion method) and thermal decomposition method (photoCVD, MO-CVD, low pressure C!VD, normal pressure CvD, etc.). In the vacuum evaporation method and sputtering method, target substances (e.g. In20B,
8n02 or 8n) etc. to the substrate by heating or the force of high-speed electrons or high-speed ions, the evaporation rate is slow, impurities may be mixed in, the product tends to have a non-uniform structure, and mechanical There are disadvantages such as low physical strength, the need to raise the substrate temperature so polymer substrates cannot be used, and the tendency to form non-uniform structures.

In addition, with chemical production methods and thermal decomposition methods, substrate characteristics such as ease of adhesion to the substrate and the need for a heating oxidation process make it impossible to use substrates with low heat resistance such as polymer films. There are restrictions.

Methods for manufacturing tin oxide using plasma include plasma CVD, sputtering, etc.
No. 005 discloses a method for producing a tin oxide film containing fluorine and antimony using a gas containing an organic tin compound, a gas containing oxygen, an ammonium fluoride gas, and a gas containing an antimony compound. However, in these methods, it is necessary to maintain the substrate temperature at a high temperature of several hundred degrees, and substrates with low heat resistance such as polymer films cannot be used. It is also necessary to mix ammonium fluoride and antimony compounds.

(Problems to be Solved by the Invention) The present inventors have completed the present invention as a result of intensive research. An object of the present invention is to provide a method for forming a transparent conductive film on a wider variety of substrates, using an industrially easier device, and having more stable performance.

(Means for Solving the Problems) The present invention introduces tetramethyltin and a gas containing at least 10 times the amount of oxygen into a plasma reactor, applies a high frequency voltage to turn it into plasma, and plasma polymerizes it onto a substrate. It is characterized by forming a film.

In the method of the present invention, the amount of oxygen coexisting during the plasma polymerization of tetramethyltin is important, and the conductivity of the tin oxide film obtained differs depending on the amount of oxygen. The amount of oxygen required is at least 10 times, preferably at least 30 times, and more preferably 50 to 200 times the weight of tetramethyltin. If the oxygen content is less than 10 times the amount of tetramethyltin, the oxidation of tetramethyltin will be insufficient and the conductivity of the film will decrease. In addition, if the oxygen content exceeds 200 times the amount of tetramethyltin group, the formation rate of the transparent conductive film will decrease, or the amount of gas in the reactor will become extremely large, resulting in an extremely poor vacuum and stability. High-energy plasma cannot be obtained, resulting in a decrease in the polymerization rate or inability to proceed with the oxidation reaction, which is undesirable because a homogeneous conductive skin is not formed.

During the plasma polymerization of tetramethyltin, a mixed gas other than oxygen may be used and is appropriately selected depending on the purpose. However, if the mixed gas other than oxygen is too large, the partial pressure of oxygen will decrease and side reactions will occur. Therefore, the mixed gas other than oxygen is preferably a non-oxidizing gas such as N2, Ar, He, etc., especially when activated. Free Ar is preferred. The amount of these mixed gases is preferably less than 50%.

The plasma used in the present invention is a low-temperature gas plasma generated by applying a high frequency voltage. The frequency of the high frequency voltage is KI
-b to N14 high frequencies are preferred. Especially 18.56M
A high frequency of Hz is preferable in terms of ease of plasma generation and stability and uniformity of glow.

The high frequency output is at most t W/all per unit area of the electrode, preferably 0.05 to 0.7 W/cli,
Furthermore, the plasma polymerization time is a major factor in determining the film thickness of the film, and the conductivity increases as the film thickness increases. However, once the film thickness reaches a certain level, it becomes almost constant. A plasma polymerization time of at least 1 minute is sufficient, preferably at least 8 minutes, more preferably at least 5 minutes, and a transparent conductive film with excellent conductivity can be obtained. What is even more interesting is that rectifying properties have been observed in thick films, and scanning electron micrographs of these films show that the surface of these films has a
Particles of about μ size were present.

The substrate on which the film is formed is not particularly limited, and may be glass, metal, ceramic, or polymer having a smooth surface. The temperature of the substrate may range from room temperature to at most 200° C. When a polymer is used for the substrate, it is appropriately selected depending on its heat resistance.

(Effects of the present invention) The transparent conductive film of the present invention can be used for a wide range of purposes due to its excellent transparency, conductivity, chemical, mechanical strength, and physical strength.

For example, it can be used as an electrode material for image tubes of various display devices, solar cells, etc., a material for photoelectric conversion elements by laminating metals such as Au or AA, and selective transmission films for heat rays.

Example 1 The cross shown in Fig. 1 was used as a substrate on the lower electrode of a type reactor, and the surface resistance was 16Ω/a+! ITO with! ! Place a glass plate with a film on it and bring the temperature of the electrode to 50°C. Tetramethyltin was injected in gaseous form from the 7-mer inlet at the flow rate shown in Table 1.
A mixed gas of 30/20 oxygen/nitrogen rich was introduced from another inlet at a flow rate of 30 mg (8 TP)/cod. Then 18
．． A high frequency of 56 MHz is applied to parallel plate electrodes with a diameter of 15 cm in the reactor through a power source and a matching box. A high frequency power of 20 W was applied for 20 minutes to effect plasma polymerization. After polymerization, the glass plate was washed with mettatolu and air-dried, and then an aluminum electrode was attached and resistance was measured in dry air.

The film thickness was measured using a repeating interference film thickness meter.

Example 2 Using the same equipment as in Example 1, 2.5% of tetramethyltin
X 10-81/m, oxygen was introduced into the reactor at a flow rate of 40-/-, and high frequency was applied at an output of 30 W for the time shown in Table 2 to perform plasma polymerization.

Note that the film thicknesses in parentheses in Exp-11 and -12 indicate the film thicknesses determined by the gravimetric method. Further, the specific resistance in parentheses is the specific resistance value when using the film thickness value determined by the gravimetric method.

The rectification ratio is the ratio of the current value (I
+/I-).

Margin below

[Brief explanation of drawings]

FIG. 1 is a schematic diagram of a high frequency discharge plasma polymerization apparatus. Kanebo Gosen Co., Ltd.

Claims (13)

[Claims] (1) Tetramethyltin and a gas containing at least 10 times the amount of oxygen are introduced into a plasma reactor, and a high frequency voltage is applied to turn them into plasma to form a plasma polymerized film on the substrate. A method for forming a transparent conductive film. (2) The method according to claim 1, wherein the amount of oxygen is at least 30 times that of tetramethyltin. (3) The method according to claim 1, wherein the amount of oxygen is 50 to 200 times that of tetramethyltin. (4) The method of claim 1, wherein the oxygen-containing gas contains at least 20% oxygen. (5) The method according to claim 1, wherein the oxygen-containing gas consists of 50% or more oxygen and 50% or less argon. (6) Output per unit area of high-frequency electrode is at most 1 W/c
The method according to claim 1, wherein m^2. (7) The method according to claim 1, wherein the high frequency output is 0.05 to 0.7 W/cm^2. (8) The method according to claim 1, wherein the plasma polymerization time is at least 1 minute. (9) The method according to claim 1, wherein the plasma polymerization time is at least 3 minutes. (10) The method according to claim 1, wherein the plasma polymerization time is at least 5 minutes. (11) The method according to claim 1, wherein the substrate is glass, polymeric metal, or ceramic having a smooth surface. (12) The method according to claim 1, wherein the temperature of the substrate is from room temperature to at most 200°C. (13) The degree of vacuum inside the reactor is 10^-^3~10^0T
The method of claim 1, wherein orr.