JPH0935535A - Zno-sno2 transparent conductive film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a ZnO-SnO2 transparent conductive film of low resistance. SOLUTION: In a ZnO-SnO2 transparent conductive film, Sn/Zn is set to from 0.6 to 0.75. As an additive, 0.1atm% or more 5atm% or less three group elements of Al, Ga, In, etc., may be contained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a ZnO--SnO ₂ system transparent conductive film.

[0002]

2. Description of the Related Art Demands for transparent conductive films are increasing as solar cells, transparent electrodes for display devices, surface heaters, and antistatic conductive films. As a transparent conductive film of a conductive metal oxide, a tin-doped indium oxide film (IT
O) and antimony-doped tin oxide films (ATO) are known and these are used industrially.

However, although ITO can form a thin film having good resistivity and transparency, it is not suitable for outdoor equipment such as solar cells because it is expensive and chemically unstable. . Further, although ATO is chemically stable, there is a problem that only a thin film having high resistance can be obtained.

Recently, it was reported that a ZnO-SnO ₂ system transparent conductive film was obtained, which has low resistance and good transparency (Jpn., J., Appl. Phys., Vol. 33 (199
4) ppL1693-1696). It is known that the ZnO—SnO ₂ system transparent conductive film is superior in heat resistance, acid resistance, and alkali resistance to ITO and ZnO.

[0005]

SUMMARY OF THE INVENTION However, ZnO
-SnO ₂ system transparent conductive film has a specific resistance of 4 × 10 ^-3 Ωcm.
Therefore, the range of application is limited. ZnO and Sn
A thin film having a low resistance has not been obtained by changing the proportion of O ₂ .

Therefore, an object of the present invention is to provide a ZnO—SnO ₂ system transparent conductive film having a low resistance.

[0007]

In order to achieve the above-mentioned object, the present invention is characterized in that in a ZnO—SnO ₂ system transparent conductive film, Sn / Zn is 0.6 to 0.75. The ZnO—SnO ₂ system transparent conductive film is used.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail.

In the ZnO—SnO ₂ system transparent conductive film, the reason why the specific resistance is not improved is that the electron concentration is 1 × 10 ^20.
This is probably because it is as low as / cc. Therefore, we tried to add a dopant to increase the electron concentration.

A thin film was prepared by RF sputtering using a target obtained by mixing a powder obtained by adding a Group 3 element to zinc oxide and calcining the powder and a powder of tin oxide and then compression-molding the mixture. As a result, when a Group 3 element such as Al, Ga, In is added,
It has been found that a specific resistance of 1 × 10 ⁻³ Ωcm or less can be obtained. It is considered that this is because the Group 3 element replaced Zn and the electron concentration increased.

The concentration of the Group 3 element is 0.1 atm% or more and 5a.
tm% or less is preferable, and particularly preferably 0.5 at
It is at least m% and at most 4 atm%. Moreover, as a result of measuring the X-ray diffraction of the transparent conductive film having a film thickness of 1 μm, these films were amorphous.

As a method of forming these zinc oxide type transparent conductive films, DC or RF sputtering or MOCV is used.
A method such as D is often used. The film thickness of the transparent conductive film is preferably about 0.02 μm to 10 μm, 0.05 μm to 0.1 μm for a display, and about 1 to 5 μm for a solar cell.

[0013]

EXAMPLES The present invention will be described in more detail below with reference to examples.

Example 1 Zinc oxide powder and aluminum oxide powder were mixed in a ball mill for 12 hours, and then the mixed powder was heat-treated at 1000 ° C. to obtain a powder having an average particle size of about 3 μm. This powder and tin oxide powder are ball milled for 20
After mixing for an hour, put this powder in a 4-inch mold and
It was molded at a pressure of t / cm ² . By adjusting the amounts of zinc oxide and tin oxide powder, the Sn / Zn ratio was adjusted to 0.58, 0.7, 0.
The composition was 8. For each composition, the amount of aluminum oxide powder added was changed to obtain aluminum concentrations of 0, 0.1,
A total of 18 kinds of targets of 1, 3, 4, 6 atm% were prepared.

RF sputtering was carried out using these targets to prepare samples. The sputtering conditions were a gas pressure of 0.5 Pa, an oxygen partial pressure of 0.005 Pa, and an RF power of 80 W. The film thickness is 1500A (0.15μ
The substrate used was Corning 7059 for m). The measurement results of the specific resistance are shown in Table 1 attached.

It can be seen from Table 1 that the samples having a Sn / Zn ratio of 0.7 and an Al concentration of 0.1 to 4 atm% exhibit a specific resistance of 1 × 10 ⁻³ Ωcm or less.

(Example 2) Zinc oxide powder and gallium oxide powder were mixed in a ball mill for 12 hours, and then mixed powder
Heat treatment was performed at 200 ° C. to obtain a powder having an average particle size of about 4 μm. This powder and tin oxide powder were mixed in a ball mill for 20 hours, and then the powder was placed in a 4-inch mold and 1 t / t.
Molded at a pressure of cm ² . The composition of the Sn / Zn ratio was 0.71 by adjusting the amounts of zinc oxide and tin oxide powder. With respect to this composition, the amount of gallium oxide powder added was changed to prepare targets having gallium concentrations of 0.1, 1 and 6 atm%. A sample was prepared by RF sputtering these targets. The sputtering conditions were the same as in Example 1. Table 2 shows the measurement results of the specific resistance of these samples.
Shown in From Table 2, Sn / Zn ratio 0.71 and Ga concentration 0.
It can be seen that the sample of 1 to 1 atm% exhibits a specific resistance of 1 × 10 ⁻³ Ωcm or less.

Example 3 Zinc oxide powder and indium oxide powder were mixed by a ball mill for 15 hours, and the mixed powder was heat-treated at 1100 ° C. to obtain a powder having an average particle size of about 3 μm. This powder and tin oxide powder were mixed in a ball mill for 20 hours and then placed in a 4-inch mold for 1 t.
Molded at a pressure of / cm ² . The composition of the Sn / Zn ratio was 0.68 by adjusting the amounts of zinc oxide and tin oxide powder. With respect to this composition, the amount of indium oxide powder added was changed to prepare targets having indium concentrations of 0.1, 1 and 6 atm%. A sample was prepared by RF sputtering these targets. The sputtering conditions are those in Example 1.
I went with the same. Table 3 shows the measurement results of the specific resistance of these samples. It can be seen from Table 3 that the sample having an Sn / Zn ratio of 0.68 and an In concentration of 0.1 to 1 atm% exhibits a specific resistance of 1 × 10 ⁻³ Ωcm or less.

[0019]

As described above, according to the present invention,
With excellent conductivity ZnO-SnO ₂ based transparent conductive film is obtained.

[Table 1]

[Table 2]

[Table 3]

Claims (3)

[Claims] 1. A ZnO-SnO ₂ system in the transparent conductive film, ZnO-SnO ₂ based transparent conductive film, wherein the Sn / Zn is from 0.75 to 0.6. 2. The ZnO—SnO ₂ -based transparent conductive film according to claim 1, wherein the additive contains a Group 3 element such as Al, Ga and In in an amount of 0.1 atm% or more and 5 atm% or less. ZnO—SnO ₂ system transparent conductive film. 3. A process according to claim 2 in ZnO-SnO ₂ based transparent conductive film according, ZnO-SnO ₂ based transparent conductive film, wherein the film is amorphous.