JPH1088332A - Sputtering target, transparent conductive coating and its production - Google Patents

Abstract

PROBLEM TO BE SOLVED: To stably produce transparent conductive coating relatively high in a specific resistance by prescribing the compsn. of a sputtering target. SOLUTION: This sputtering target is the one essentially composed of ZnO and contg. Ga and Y. By using this target, transparent conductive coating having relatively high specific resistance of 10<-1> to 10<10> Ωcm can stably be obtd. This is owing to the following reason. Ga in the coating or target partially or totally enters into a solid solution, works as a dopant and works so as to produce electrons having electric conductivity. Y in the coating reduces the concn. of a carrier and works, as an impurity scattering source, so as to reduce the mobility thereof. By this operation, the coating relatively high in specific resistance can be realized even in sputtering with a low oxygen concn. Preferably, the content of Ga is regulated to 0.2 to 8.0mol% expressed in terms of Ga1 O3 , and the content of Y is regulated to 0.2 to 60.0mol% expressed in terms of Y2O3 .

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a sputtering target, a transparent conductive film and a method for producing the same.

[0002]

2. Description of the Related Art Conventionally, the resistivity is relatively high at 10 ^-1 to 10.
^When an oxide-based transparent conductive film having a resistivity of ¹⁰ Ωcm is formed by a sputtering method, the specific resistance of the target itself is 10 ⁻¹ to 10 ⁻¹ .
It is known that sputtering is performed using a target having a conductivity of 10 ¹⁰ Ωcm at a low oxygen concentration such that the oxygen in the atmospheric gas is 3% by volume or less.

However, in this method, since the conductivity of the target is poor, it is limited to the high-frequency sputtering method, and the DC structure is excellent in industrial productivity such as a simple apparatus structure, good operability, and a high deposition rate. There was a problem that the sputtering method was not used.

In order to use the DC sputtering method, 10
It is desirable to use a low-resistance high-conductivity target of ⁻² Ωcm or less in that a stable discharge can be obtained.

However, when a DC sputtering film is formed in a low oxygen atmosphere containing only argon gas using a ZnO-based target having a low resistance of 10 ^-3 to 10 ^-1 Ωcm, the specific resistance of the formed film is 10%. Only a low-resistance film of the order of ^-4 Ωcm has been obtained (Japanese Patent Laid-Open No. 2-149559).

When a target having a low resistance of 10 ⁻² Ωcm or less is used, a film having 10 ⁻¹ to 10 ¹⁰ Ωcm can be obtained by introducing an oxidizing gas such as an oxygen gas into an atmosphere gas. Sputtering at an oxygen concentration is required.

However, this oxygen has a problem that it also acts on the formed film and damages the film.

Therefore, a method of manufacturing a transparent conductive film having a specific resistance of 10 ^-1 to 10 ¹⁰ Ωcm under a low oxygen concentration atmosphere with little damage to the film by using a DC sputtering method excellent in productivity is desired. Was rare.

[0009]

The present invention can be used for a DC sputtering method and has a relatively high specific resistance.
An object of the present invention is to provide a sputtering target capable of stably producing a transparent conductive film having a thickness of 0 ^-1 to 10 ¹⁰ Ωcm.

Another object of the present invention is to provide a transparent conductive film which is excellent in productivity and can easily obtain a relatively high specific resistance of 10 ^-1 to 10 ¹⁰ Ωcm, and a method for producing the same.

[0011]

The present invention provides a sputtering target containing ZnO as a main component and containing Ga and Y.

The specific resistance of the sputtering target is 1
It is preferably at most 0 ^-2 Ωcm. If it is higher than 10 ^-2 Ωcm, discharge during DC sputtering tends to be unstable. In particular, it is preferably 10 ⁻³ Ωcm or less.

[0013] By using the sputtering target of the present invention, a relatively high specific resistance of 10 ^-1 to 10 ¹⁰ Ωc
The transparent conductive film having a value of m can be stably obtained.

Since the above-mentioned specific resistance can be obtained more stably, the content ratio of Ga is 0.1% in terms of Ga ₂ O ₃ .
The content of Y is preferably from ₂ to 8.0 mol% and from 0.2 to 60.0 mol% in terms of Y ₂ O ₃ .

The method for manufacturing the target is not particularly limited, but a method for sintering ordinary ceramics such as a normal pressure sintering method or a hot press method can be used. The hot pressing method is preferable because a dense and low-resistance sintered body (target) can be produced.

The present invention also provides a method for producing a transparent conductive film by sputtering a sputtering target in an atmosphere having an oxidizing gas content of 3% by volume or less, wherein the sputtering target is used as the sputtering target. And a method for producing a transparent conductive film.

The atmosphere gas has an oxidizing gas content of 3%.
It is used in a volume% or less, and can be used only with an inert gas such as an argon gas.

If the content of the oxidizing gas in the atmosphere exceeds 3% by volume, the oxidizing gas in the atmosphere resputters the formed film and damages the film.

Examples of the oxygen-containing gas that can be used in the present invention include gases having oxygen atoms in gas molecules such as O ₂ , H ₂ O, CO, and CO ₂ .

As a sputtering method, a direct current method,
Although any discharge method such as a high frequency method can be used, a direct current sputtering method which is excellent in industrial productivity such as a simple apparatus structure, good operability, and a high film forming rate is preferable.

Examples of the substrate on which a film is formed include glass, ceramics, plastics, and metals. The temperature of the substrate during film formation is not particularly limited. After the film formation, the substrate can be post-heated (heat treated).

According to the present invention, ZnO is used as a main component.
A transparent conductive film containing a and Y is provided.

The transparent conductive film of the present invention can easily achieve a relatively high specific resistance of 10 ^-1 to 10 ¹⁰ Ωcm.
Such a transparent conductive film having a relatively high specific resistance is suitable.

In particular, when a high sheet resistance value of 10 kΩ / □ to 100 GΩ / □ is required, for example, it is most suitable for a transparent heating element for obtaining various desired heating values. Further, for example, when used in combination (laminated) with another transparent conductive film, conductivity near the electrode portion is very important in practical use, but has a resistance of 10 kΩ / □ to 100 GΩ / □. If this is the case, the conductivity near the electrodes is sufficient and the film can be stably energized (used). At this time, when used as a base film of another transparent conductive film, the crystallinity of the film laminated thereon is adjusted, contamination from moisture remaining in vacuum is suppressed, or the film is laminated on the film. Characteristics such as conductivity and durability of the film can be improved. Further, it can be used as a protective film as an overcoat film of another transparent conductive film. In addition, the lamination can reduce internal stress of the laminated film and reduce film breakage.

When the specific resistance of the film is lower than 10 ^-1 Ωcm,
In order to obtain a desired (10 kΩ / □ to 100 GΩ / □) sheet resistance value, it is necessary to reduce the film thickness, which is not preferable because problems such as disconnection of the film are likely to occur.

When the specific resistance of the film is higher than 10 ¹⁰ Ωcm, it is necessary to increase the film thickness in order to obtain a desired sheet resistance value (10 kΩ / □ to 100 GΩ / □), which increases the cost. It is not preferable.

Since the above-mentioned specific resistance can be obtained more stably, the content ratio of Ga is 0.1% in terms of Ga ₂ O ₃ .
A 2 to 8.0 mol%, it is preferable content of Y is 0.2 to 60.0 mol% in terms _of Y ₂ O _3.

In the present invention, a part of Y contained in the film or the target of the present invention can be replaced with another element, or another element can be added to Y. Other elements include La and Ce.
Lanthanoids and Sc.

[0029]

The Ga in the film and the target is partially or entirely dissolved in ZnO to function as a dopant, and functions to generate electrons exhibiting conductivity.

Y in the film works to reduce the carrier concentration and to reduce the mobility as an impurity scattering source. By this effect, a relatively high specific resistance of 10 ^-1 to 10 ¹⁰ Ωcm can be realized even by sputtering at a low oxygen concentration.

Y in the film is uniformly dispersed in the film,
It exists as a solid solution in ZnO. On the other hand, since Y in the target is segregated, the effect of increasing the resistance of Y is limited to a narrow range, so that the target as a whole has a low resistance of the order of 10 ⁻⁴ Ωcm. Y in the target exists as a solid solution in Y ₂ O ₃ or ZnO.

[0032]

【Example】

(Examples 1 to 11) ZnO powder, Ga ₂ O ₃ powder and Y ₂
O ₃ powders were prepared, and these powders were mixed at various ratios shown in Table 1 with a ball mill.

This mixed powder was filled in a carbon hot press mold and hot-pressed at 1100 ° C. for 1 hour in an argon atmosphere to produce a sintered body. The hot press pressure at this time was 100 kg / cm ² .

Next, 3 × 3 × 30
The sample was cut into a square prism having a thickness of mm, and the specific resistance was measured by a four-terminal method. Table 1 shows the results. All had low resistance of the order of 10 ⁻⁴ Ωcm.

Next, each sintered body was cut out to a size of 6 inches in diameter and 5 mm in thickness, and ZnO--Ga ₂ O ₃
Was prepared -Y ₂ O ₃ system targets (hereinafter, referred to as ZGY target.).

Using these ZGY targets, a magnetron direct current (DC) sputtering apparatus is used to
An nO—Ga ₂ O ₃ —Y ₂ O ₃ -based film (hereinafter referred to as a ZGY film) was formed by applying power: 800 W, introducing gas: argon gas, pressure: 4 × 10 ⁻³ Torr, and substrate temperature: This was performed under the condition of no heating. Soda lime glass was used for the substrate. The film thickness was set to be about 40 nm.

During the film formation, the discharge was stable and there was no problem. After film formation, the film thickness was measured to be about 40 nm. Sheet resistance was measured by the two-end needle method. The specific resistance was calculated from the measured sheet resistance and film thickness. Table 1 shows the results.
Shown in

As shown in Table 1, the resistance of the ZGY film increased as the amount of Y added increased, and increased from 10 ^-1 to 10 ¹⁰ Ωcm. On the other hand, the composition of the ZGY film was analyzed by ICP. Table 1 shows the results. The content of Y (in terms of Y ₂ O ₃ ) in the ZGY film was about twice the content of the target.

The difference between the Y content in the target and the Y content in the film is that the vapor pressure of Y ₂ O ₃ is ZnO or Ga ₂ O.
Probably because it is lower than ₃ .

Example 12 As in Example 5, ZnO powder, G
a ₂ O ₃ powder and Y ₂ O ₃ powder were prepared, and these powders were mixed by a ball mill at the ratios shown in Table 1. After molding this mixed powder by a rubber press method,
Under normal pressure firing at 0 ° C. for 3 hours, a sintered body was produced.

Next, after cutting out in the same manner as in Example 5, the specific resistance was measured by a four-terminal method. As a result, the specific resistance is 5 × 10 ^−3.
Ωcm.

Next, in the same manner as in Example 5, a ZGY target was prepared by cutting out a piece having a diameter of 6 inches and a thickness of 5 mm.
A film was formed under the same conditions as in Example 5. During the film formation, the discharge was stable and there was no problem. After film formation, the film thickness was measured,
It was about 40 nm, and the specific resistance was 10 ⁵ Ωcm. The contents of Ga ₂ O ₃ and Y ₂ O _{3 in} the film were 2.7 mol% and 18.3 mol%, respectively.

The films (including the substrates) of Examples 1 to 12 all had a visible light transmittance of 85% or more.

(Examples 13 to 16)
In the same manner as in Example 1, the powder mixed at the ratio shown in Table 1 was hot-pressed to produce a sintered body.

Table 1 shows the resistivity measured in the same manner as in Example 1. In Example 15 containing no Ga, the specific resistance of the target was as high as 10 ⁵ Ωcm.

Next, a target was prepared from these sintered bodies in the same manner as in Example 1. Using these targets, a film was formed under the same conditions as in Example 1 using a magnetron DC sputtering apparatus.

In Example 15, which did not contain Ga, the target was high in resistance and did not discharge, so that a film could not be formed by DC sputtering.

In Examples 13, 14 and 16, the discharge was stable during the film formation, and there was no problem. After film formation, the film thickness was measured to be about 40 nm. Table 1 shows the result of calculating the specific resistance in the same manner as in Example 1. In Examples 13, 14 and 16, a desired transparent conductive film having a density of 10 ^-1 to 10 ¹⁰ Ωcm was not obtained.

The films (including the substrate) of Examples 13, 14 and 16 all had a visible light transmittance of 85% or more.

[0050]

[Table 1]

[0051]

The target of the present invention can be used for a direct current sputtering method, and the use of the target of the present invention stabilizes a transparent conductive film having a relatively high specific resistance of 10 ^-1 to 10 ¹⁰ Ωcm. Can be manufactured.

The transparent conductive film of the present invention has a relatively high 10 ^-1.
A specific resistance of 10 to 10 ¹⁰ Ωcm can be easily achieved, and the productivity is excellent.

The transparent conductive film of the present invention can be used alone or in combination with another transparent conductive film to provide the following effects.

For example, when the transparent conductive film of the present invention is used as an underlayer, it functions as a barrier layer and prevents evaporation or diffusion from the substrate. In addition, a film having desired crystallinity can be manufactured by suppressing contamination of the transparent conductive film which is subsequently formed as an upper layer from moisture remaining in vacuum or controlling crystal growth.

When used as an overcoat, it functions as a protective layer from the outside air such as moisture and oxygen.

When used in combination (laminated) with another transparent conductive film, conductivity near the electrode portion is very important for practical use, but it is required to have a resistance of 10 kΩ / □ to 100 GΩ / □. In this case, the conductivity near the electrodes is sufficient, the film can be stably energized (used), and abnormal heat generation near the electrodes can be prevented. In addition, the lamination can reduce internal stress of the laminated film and reduce film breakage.

Claims (5)

[Claims] 1. A sputtering target containing ZnO as a main component and containing Ga and Y. 2. The composition contains 0.2 to 8.0 mol% of Ga in terms of Ga ₂ O ₃ and 0.2 to 60.0 mol% of Y in terms of Y ₂ O _3.
2. The sputtering target of claim 1, comprising: 3. A method for producing a transparent conductive film by subjecting a sputtering target to DC sputtering in an atmosphere having an oxidizing gas content of 3% by volume or less, wherein the sputtering target according to claim 1 or 2 is used as the sputtering target. A method for producing a transparent conductive film, comprising: 4. A transparent conductive film containing ZnO as a main component and containing Ga and Y. 5. A composition containing 0.2 to 8.0 mol% of Ga as Ga ₂ O ₃ and 0.2 to 60.0 mol% of Y as Y ₂ O _3.
The transparent conductive film according to claim 4, comprising: