JPH062134A - Method for producing transparent conductive film - Google Patents

Abstract

PURPOSE:To obtain a high-quality film in the sputtering method using an indium oxide-tin oxide (ITO) target by sputtering the target with a high-frequency discharge and suppressing the fluctuation in the film forming rate and decrease in the film resistivity due to the deterioration of the target surface. CONSTITUTION:Gaseous argon, for example, is introduced into a vacuum chamber 1, in which a substrate 6 is placed, to set the sputtering condition. A high- frquency voltage is then impressed between an ITO target 5 and the substrate 6 from a high-frequency power source 2 to sputter the target. The material on the target 5 surface is driven out by the argon ion and deposited on the substrate 6 as a film. Consequently, the target 5 and the material redeposited on the target are simultaneously sputtered irrepective of the variance in the resistance of the target 5 surface due to the redeposited material, hence the target 5 surface is not blackened, protrusions are not formed on the surface, the film forming rate is not fluctuated, and the film resistivity is not deteriorated.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing an indium-tin oxide transparent conductive film by a sputtering method,
Specifically, by using high frequency discharge during film formation,
The present invention relates to a method for continuously producing a transparent conductive film having excellent characteristics, which suppresses fluctuations in film formation rate and deterioration in film specific resistance due to alteration of the target surface.

[0002]

_2. Description of the Related Art Conventionally, indium-tin oxide (In ₂ O ₃ --Sn) obtained by a vacuum deposition method or a sputtering method is used.
O ₂ : Indium-Tin Oxide: ITO) film is widely used as an electrode material for electronic displays such as plasma displays, liquid crystal displays, and touch panels, by taking advantage of characteristics such as high conductivity and high transparency.

In recent years, the sputtering method has been generally used in the production line from the viewpoint of the controllability of the film formation rate and the uniformity of the film formed on a large area substrate. When it is used, the slow film forming speed has been a major obstacle. Therefore, by forming a magnet on the back surface of the target electrode and generating a non-uniform magnetic field due to the curved magnetic field lines on the target surface, the plasma is confined near the target surface and the ionization efficiency of the introduced gas such as argon gas is increased to form a film. A magnetron sputtering method has been devised that can improve the speed, and is now most widely used.

Generally, in the sputtering method, a high frequency voltage is applied between the cathode (target) and the anode (substrate) (RF sputtering method) and a direct current voltage is applied (DC).
Sputter method). Currently, on a commercial scale, the DC magnetron sputtering method is the mainstream for the production of transparent conductive films because of its high deposition rate and controllability and stability during deposition. 2.0 x 10 ^-4 Ω · cm
The low resistance film of is obtained. A magnetron sputtering method using both direct current and high frequency has also been proposed (Japanese Patent Laid-Open No. 3-249171).

However, when a film is formed by the direct current magnetron sputtering method using an ITO target, the target surface becomes black and projections occur (forest blackening phenomenon) as the target usage time becomes longer. It is known that fluctuations in the film formation rate and deterioration of the film specific resistance occur. Therefore, there arises a problem that a high-quality ITO film cannot be stably obtained for a long time.

Therefore, when the ITO film is formed, in order to improve the productivity, it is necessary to perform cleaning such as removing the black protrusions on the target surface after a certain period of time. However, in a mass-production type sputtering apparatus, this many cleanings greatly affects the productivity.

Therefore, there is a demand for a long-life target (long-life target) capable of continuously and stably obtaining a high-quality ITO film even if the cleaning frequency is small or no cleaning is performed at all.

As a measure for extending the life of the ITO target,
The density of the target can be increased. It is known that the forest blackening phenomenon occurs also in the high density target, and the film resistivity is deteriorated even if the forest blackening does not occur on the target surface.

[0009]

SUMMARY OF THE INVENTION The object of the present invention is to prevent fluctuation of the film formation rate by preventing the phenomenon of forest blackening on the target surface which occurs when a film is formed using an ITO target which has been conventionally used. Another object of the present invention is to provide a stable and continuous production method of a high-quality ITO transparent conductive film by suppressing the deterioration of the film specific resistance.

[0010]

The above object of the present invention can be achieved by performing sputtering by high-frequency discharge instead of DC discharge which has been conventionally used.

That is, the method for producing a transparent conductive film of the present invention is characterized in that in the method for producing a transparent conductive film by a sputtering method using an ITO target, high frequency discharge is used for the sputtering.

The present invention will be described in detail below. FIG. 1 is a configuration diagram of an apparatus for carrying out the manufacturing method of the present invention, and shows a typical high frequency magnetron sputtering apparatus. In the figure, 1 is a vacuum chamber, 2 is a high frequency power supply, 3 is a magnet, 4 is a backing plate, 5 is an ITO target, 6 is a substrate, 7 is a mass flow, 8 is a gas cylinder, 9 is a vacuum pump, 10 is a vacuum gauge, Reference numerals 11 denote matching boxes, respectively.

This apparatus has an IT inside a vacuum chamber 1 equipped with a vacuum exhaust system consisting of a vacuum pump 9, a gas cylinder 8 of argon gas or the like, and a gas introduction system consisting of a mass flow 7.
An O target 5 and a substrate 6 facing the O target 5 are arranged.

In sputtering, after the substrate 6 is set in the vacuum chamber 1, the vacuum chamber 1 is evacuated to a high vacuum by the vacuum pump 9 and an argon gas or a mixed gas of argon and oxygen is mass flowed from the gas introduction system 7. And is introduced into the vacuum chamber 1 via the to set the sputtering conditions. Further, the substrate 6 is heated by a substrate heater or the like as needed. After setting the sputtering conditions, a high frequency power supply 2 applies a high frequency voltage between the ITO target 5 and the substrate 6. At this time, argon ions knock out the target material on the target surface,
A film is deposited on the surface of the substrate.

On the back surface of the ITO target 5, there is provided a magnet 3 for increasing the plasma density on the target surface to increase the film formation rate. As a result, the ITO target 5 has a portion with a high plasma density which is dug. The part that is marked is called the erosion part.

The ITO target 5 is driven by the DC power supply 12.
In the conventional DC magnetron sputtering apparatus shown in FIG. 2 in which a DC voltage is applied between the substrate 6 and the substrate 6, as the target use time (sputtering accumulated time) becomes longer,
The vicinity of this erosion is blackened and a protrusion is generated. Along with this, fluctuations in the film formation rate and deterioration of the film resistivity have become major problems at the production site.

Therefore, in the present invention, the high frequency voltage is applied to the sputtering as described above to generate the high frequency discharge, thereby preventing the blackening of the surface of the ITO target and the generation of the projections.

In this way, even after long-term use, I
The phenomenon of forest blackening of the TO target is suppressed, and fluctuations in the film formation rate and deterioration of the film specific resistance are prevented.

[0019]

The action of the protrusion of the ITO target and the action when the high frequency discharge is used are as follows.

That is, when a film is formed by sputtering using an ITO target, the target material knocked out by argon ions reaches the substrate and becomes an ITO film, and the target material reattaches to the target surface without reaching the substrate. There is something to do. It is considered that this re-deposited substance is in a state of lacking oxygen due to the bombardment of argon ions, and it is considered that the resistance of the re-deposited substance is higher than that of the ITO target body.

When sputtering is performed by direct current discharge in such a state, positive charges brought by inflowing argon ions are accumulated in the redeposited portion, and the potential of the redeposited portion becomes equal to the plasma potential. Therefore, the argon ions do not collide with only that portion, and a dug-up protrusion is formed.

On the other hand, since the sputtering by the high frequency discharge has been conventionally used for forming a film of an insulator, the sputtering by the high frequency discharge does not affect the resistance of the target surface due to the adherence of the redeposited material and the target body. Since it is possible to simultaneously sputter the reattached material and the reattachment, it is possible to prevent the generation of protrusions.

From the above, when the ITO transparent conductive film is manufactured by sputtering, high frequency discharge is used to prevent blackening of the target surface and generation of protrusions, and fluctuation of the film formation rate due to blackening of the forest and It is possible to suppress deterioration of the film resistivity.

[0024]

EXAMPLES The present invention will be specifically described below based on Examples and the like.

Example Using the apparatus shown in FIG. 1, I was placed on the substrate by high frequency discharge.
A TO film was formed. The target used at this time is In
_A mixture of ₂ O ₃ and SnO ₂ at a ratio of 10% by weight was manufactured by a cold press method with a density of 87% and a thickness of 6 mm.
It is a sintered body of. Here, a crown glass having a thickness of 1 mm was used for the substrate.

At this time, the erosion digging depth, the variation rate of the film formation rate, and the change of the film specific resistance were evaluated.

First, high frequency power 1 watt / c
Films were formed at m ² , pressure of 3 mtorr, and substrate temperature of 200 ° C. by changing the mixing ratio of argon gas and oxygen gas, and the conditions for obtaining the lowest film resistivity were searched. After that, sputtering was continued at ² watt / cm ² until the erosion portion became 1 mm, and when 1 mm was dug, 1 watt / cm ² was again obtained.
The film formation was continued until 5 mm was dug.

As a result, in the case of sputtering by high frequency discharge, almost no protrusions were formed on the target surface when the erosion was dug by 5 mm.

FIG. 3 shows changes in the film formation rate with respect to the erosion depth. From FIG. 3, the film formation rate when digging 5 mm by sputtering by high frequency discharge was reduced by about 10% compared to when the target was first used.

FIG. 4 shows changes in the film resistivity with respect to the erosion depth. From FIG. 4, in the case of sputtering by high-frequency discharge, the film specific resistance at the beginning of use of the target is 1.8 × 10 ⁻⁴ Ω · cm, and 2.4 in the state where 5 mm is dug.
× 10 ^-4 Ω · cm, which is about 1.3 times the initial value.

Comparative Example Using the device shown in FIG. 2, IT was formed on the substrate by DC discharge.
An O film was formed. The target and substrate used at this time are the same as those in the example.

At this time, the erosion digging depth, the variation rate of the film formation rate, and the change of the film specific resistance were evaluated.

First, high frequency power 0.3 watt / c
Film formation was performed by changing the mixing ratio of argon gas and oxygen gas at m ² , pressure of 3 mtorr, and substrate temperature of 200 ° C., and a condition for obtaining the lowest film specific resistance was searched for. After this, erosion is 1m
Sputtering was continued at 2.3 watt / cm ² until the m became 1 m and 0.3 watt / c was again obtained when 1 mm was dug.
The process of forming a film with m ² was continued until 5 mm was dug.

As a result, in the case of sputtering by DC discharge, many black protrusions were generated on the target surface when the erosion was used up to 5 mm.

FIG. 3 shows changes in the film formation rate with respect to the erosion depth. From FIG. 3, the film formation rate when digging 5 mm by sputtering by DC discharge was reduced by about 65% compared to when the target was first used.

FIG. 4 shows the change in the film resistivity with respect to the erosion depth. From FIG. 4, in the case of sputtering by DC discharge, the film specific resistance at the beginning of using the target is 2
^{× 10 -4 Ω · cm, 5} × 10 -4 Ω in a state where dug 5mm
・ It was about 2.5 times that of the beginning of use.

[0037]

As is apparent from the above, when the ITO film is formed by sputtering according to the manufacturing method of the present invention, fluctuations in the film formation rate and deterioration of the film specific resistance due to blackening of the target surface and generation of protrusions And a high quality ITO transparent conductive film can be stably and continuously manufactured without cleaning the target surface.

[Brief description of drawings]

FIG. 1 is a configuration diagram of a high frequency magnetron sputtering apparatus used in an example.

FIG. 2 is a configuration diagram of a DC magnetron sputtering device used in a comparative example.

FIG. 3 is a graph showing the relationship between the erosion depth and the film formation rate fluctuation rate.

FIG. 4 is a graph showing the relationship between erosion depth and film resistivity.

[Explanation of symbols]

1: vacuum chamber, 2: high frequency power supply, 3: magnet, 4: backing plate, 5: ITO target,
6: substrate, 7: mass flow, 8: gas cylinder, 9: vacuum pump, 10: vacuum gauge, 11: matching box, 1
2: DC power supply.

Claims (1)

[Claims] 1. A method for producing a transparent conductive film by a sputtering method using an indium-tin oxide target, wherein high frequency discharge is used for the sputtering.