JPS62122011A - Transparent conducting film and manufacture of the same - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed description of the invention] Arashi division The present invention relates to a transparent conductive film and a method for manufacturing the same.

The transparent conductive film manufactured by Jōmei Co., Ltd. has both high conductivity and high transparency in the visible range, and is an EL (electroluminescence) film.
It is used as transparent electrodes for display panels such as display elements and liquid crystal display elements, and as electrode films for solar cells and various light-receiving elements.

Conventionally, transparent conductive films have been made of metal thin films such as Au or Sn.
O2, In, 03. CaO, ZnS, Z
Thin films such as nO are known. But these.

At present, most of them have insufficient electrical conductivity, as well as many drawbacks in terms of mechanical properties (hardness, density) and chemical stability.

S n O2, r T O (Indium Tin 0
xide) is widely used.

However, In2O, SnO2, and IT○ also have the following drawbacks, and further improvements are needed.

(1) It has poor thermal stability, and when used in devices such as EL, the resistivity increases when subjected to heat treatment, and In and Sn diffuse into the light emitting layer, etc., causing adverse effects.

(2) 30°C during or after film formation to lower specific resistance.
Heat treatment at 0°C or higher is required.

(3) The materials are very expensive.

Zinc oxide (Zn○) is much cheaper than ZnOff or SnO, and is preferred as an industrial material for transparent conductive films. However, although ZnO has high transparency in the visible range.

Electrical conductivity was not sufficient.

The present invention provides a transparent conductive film that has high electrical conductivity and heat resistance, and can be formed from inexpensive materials.

The transparent conductive film of the present invention is characterized by being a C-axis oriented film containing zinc oxide as a main component and aluminum.

The method for manufacturing a transparent conductive film of the present invention uses a target containing zinc oxide as a main component and aluminum oxide as a main component, and uses a DC
It is characterized by being manufactured by a magnetron sputtering method.

The present invention will be explained in more detail below.

Zinc oxide (ZnO) films inherently have high electrical conductivity and high transmittance in the visible range, but it has been found that the specific resistance can be further reduced by adding aluminum. This film also has excellent thermal stability.

FIG. 1 is a graph showing the relationship between the amount of aluminum added and specific resistance. This was prepared by a DC magnetron sputtering method using a mixture of A1□O□ powder and ZnO powder and sintering as a target material under conditions of a substrate temperature of 300° C. and a film thickness of 2000 mm. It can be seen that the specific resistance changes depending on the amount of A1□03 added. The amount of Al2O in the transparent conductive film is (A I 20 g)
/ (ZnO+AI,O,) is preferably in the range of 0.5 to 5% by weight.

More preferably, it is in the range of 1.0 to 4.0% by weight.

Note that when a target containing 6 wt % or more of Al2O was used, the resistance of the target itself became large and discharge could not be performed using a DC power source.

FIG. 2 is a graph showing the relationship between the half-width: Δθso of the rocking curve of the (002) plane, which is a characteristic value indicating the C-axis orientation of the transparent conductive film, and the specific resistance: ρ. Δθ of the transparent conductive film. It can be seen that the smaller the resistivity becomes, that is, the more the C-axis orientation improves, the smaller the specific resistance becomes. Therefore, the transparent conductive film preferably has a Δθ5o of 8.0 (deg) or less, more preferably 4.0 (deg) or less.

The C-axis alignment film of ZnO containing Al can be produced by sputtering methods such as DC magnetron sputtering method and RF magnetron sputtering method, PVD method such as vapor deposition method, ion blating method, etc.
By VD method etc.

It can be formed on any suitable substrate, and among these, DC magnetron sputtering is preferred.

Next, the manufacturing method of the present invention using DC magnetron sputtering will be evaluated.

FIG. 3 is a schematic diagram showing the configuration of a DC magnetron sputtering apparatus. A sputtering electrode 13 is provided in the vacuum chamber 11, and a target 15 is placed on the sputtering electrode 13.

A substrate 17 is held facing the target 15 so as to be parallel to the surface of the target 15 . The exhaust system 21 creates a high vacuum in the vacuum chamber 11, e.g.
After evacuation to ~IO-' Torr, a sputtering gas such as Ar or Ar+02 is introduced by the gas introduction valve 23 until the degree of vacuum is, for example, 10-2 to 10'' Torr to set the sputtering pressure. Then, when a high voltage is applied between the electrodes by the sputter power supply 25, a magnet (not shown) provided on the back surface of the sputter electrode 13
A magnetron discharge occurs due to the magnetic field, and the target is sputtered to form a transparent conductive film on the surface of the substrate 17. In the figure, a DC power source is used as the power source 25, but in the case of RF magnetron sputtering, an RF main power source may be used. However, the DCC magnetron sputtering method has a high sputtering speed and causes less thermal damage to the substrate surface. In the figure, 19 indicates a thermocouple for measuring the substrate temperature. The composition of the target is (A1.03
)/(A1.O, +ZnO) from 0.5 to 5.0
The weight percent range is preferably from 1.0 to 3.
It is 0% by weight. The target is ZnO powder and Al2O,
After mixing with powder, crushing and compression molding, 900-1000
The material used is one that has been main sintered at a temperature of about .degree. C. and further heat-treated at a high temperature, for example, about 1300.degree.

FIG. 4 is a graph showing the relationship between substrate temperature and specific resistance ρ. As the substrate temperature increases, the specific resistance decreases, and the temperature reaches 300℃.
The minimum value is 2~3X10-'(Ω・cm), but 3
When the temperature exceeds 00°C, ρ becomes somewhat larger. This is D under the conditions of argon gas pressure: 0.5X10-2 Torr and film thickness of 2000 people.
This was done by C magnetron sputtering method. in this way,
The transparent conductive film of the present invention can achieve a low specific resistance even at relatively low temperatures.

FIG. 5 is a graph showing the relationship between Ar gas pressure (PAr) and specific resistance ρ when a transparent conductive film is formed by magnetron sputtering under conditions of a substrate temperature of 300° C. and a film thickness of 2000 ml. It can be seen that the lower the argon gas pressure, the more a conductive film with a lower specific resistance can be obtained.

Figure 6 shows the substrate temperature at 300℃, Figure 7 shows the substrate water cooling (~1
ρ (specific resistance), n (carrier density), μ at
2 is a graph showing the dependence of H (hole mobility) on the thickness of an A1-doped ZnO film.

When the substrate temperature is 300° C., ρ is smaller and n and μH are larger. Furthermore, film thickness dependence is also improved.

Figure 8 shows the temperature of the substrate at 300°C, and Figure 9 shows the temperature of the substrate with water cooling.
It is a figure showing a line diffraction pattern. Both (002),
Only the peak of the (004) plane was observed, indicating that the film structure was oriented along the C axis. Furthermore, the diffraction intensity is about 20 times greater when the substrate temperature is 300° C., and it is considered that the degree of orientation is stronger.

In addition, A1-doped Z obtained by the DC magnetron method
The nO film exhibits a transmittance of 80% or more in the visible range.

According to the present invention, a transparent conductive film having heat resistance, thermal stability, and low resistivity can be obtained. Also.

A transparent conductive film with a low resistance on the order of 10''3 to 10-4 Ω·CII+ can be obtained even at 100°C or lower, and since no heat treatment is required after film formation, it can be formed even on a plastic film with a low heat resistance temperature. Zno and A used in the present invention
Since l□03 is very inexpensive compared to In2O and SnO2, it is extremely advantageous industrially.

Example 1 ZnO powder and Al□○ powder were combined into (Al□O,)/
(Al 203 + ZnO) was mixed to a concentration of 2 wt%, and after calcining, crushing, and compression molding, the
After main sintering at 0°C, the target was further heat-treated at 1300°C to lower the resistance.

Using this target, DC magnetron sputtering was performed at a substrate temperature of 300°C using the apparatus shown in Figure 3, and 7059
A transparent conductive film was formed on glass (manufactured by Corning).

The properties of the obtained transparent conductive film are shown in Table 1 below together with the following Examples.

Example 2 The same procedure as Example 1 was carried out except that the substrate temperature was maintained at 100° C. or less by water cooling.

Example 3 At a substrate temperature of 300°C, (A l-03) / (Z n
Al□O so that O+Al□O,) is 2wt%
, and Zn○ were simultaneously ion-blated from separate deposition sources to form a transparent conductive film.

Example 4 A transparent conductive film was produced in the same manner as in Example 1, except that a polyethylene terephthalate film was used as the substrate and the substrate temperature was maintained at 100° C. or lower by water cooling.

Table 1 *) Average transmittance at wavelength 400-700nm

[Brief explanation of drawings]

FIG. 1 is a graph showing the relationship between the amount of A1□03 added to the target and the specific resistance ρ of the film. FIG. 2 is a graph showing the relationship between Δθ5° and specific resistance. FIG. 3 is a schematic diagram showing the configuration of a DC magnetron sputtering apparatus. FIG. 4 is a graph showing the relationship between substrate temperature and specific resistance ρ. FIG. 5 is a graph showing the relationship between argon gas pressure and specific resistance ρ. Figure 6 shows the substrate temperature at 300℃, Figure 7 shows the substrate water cooling (~1
ρ (specific resistance), n (carrier density), μ at
2 is a graph showing the dependence of H (hole mobility) on the thickness of an A1-doped Zn○ film. FIG. 8 is a graph showing the X-ray diffraction pattern when the substrate temperature is 300° C., and FIG. 9 is a graph showing the X-ray diffraction pattern when the substrate is water-cooled. 11...Vacuum tank 13...Sputter electrode 15...Target 17...Substrate

Claims (2)

[Claims] 1. A transparent conductive film characterized by being a C-axis oriented film containing zinc oxide as a main component and aluminum. 2. 1. A method for producing a transparent conductive film, characterized in that it is produced by a DC magnetron sputtering method using a target containing zinc oxide as a main component and aluminum oxide mixed therein.