JP2000129432A - Conductive metal oxide sintered body and use thereof - Google Patents

Abstract

[PROBLEMS] To provide a flat thin film having no domain structure and excellent etching characteristics even when an ITO thin film is formed by a sputtering method at a substrate temperature higher than a crystallization temperature. The gallium is substantially composed of indium, tin, gallium, and oxygen, and the gallium is Ga / (In + Sn + G).
An ITO containing 0.1 to 5.0 atomic% of gallium in a ratio of Ga / (In + Sn + Ga) using a sputtering target formed of an ITO sintered body containing 0.1 to 5.0 atomic% of a). Form a thin film.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a conductive metal oxide sintered body, a target, a thin film, and uses thereof.

[0002]

2. Description of the Related Art ITO (Indium Tin Oxi)
de) The thin film has characteristics such as high conductivity and high transmittance,
Further, since fine processing can be easily performed, they are used in a wide range of fields such as display electrodes for flat panel displays, window materials for solar cells, and antistatic films. In particular, in the field of flat panel displays such as liquid crystal display devices, in recent years, the size and definition have been advanced, and the demand for ITO thin films as display electrodes has been rapidly increasing. The method of manufacturing such an ITO thin film can be roughly classified into a chemical film forming method such as a spray pyrolysis method and a CVD method, and a physical film forming method such as an electron beam evaporation method and a sputtering method. Among them, the sputtering method is used in various fields because it is a film forming method that can easily increase the area and obtain a high-performance film.

[0003] When an ITO thin film is produced by a sputtering method, an alloy target composed of indium metal and tin (hereinafter abbreviated as an IT target) or a composite oxide target composed of indium oxide and tin oxide (hereinafter abbreviated as IT) is used as a sputtering target.
O). Among them, IT
The method using an O target is less likely to change over time in the resistance value and transmittance of the obtained film than the method using an IT target, and it is easy to control film forming conditions. Has become.

In general, it is known that the resistivity of an ITO thin film is strongly affected by the substrate temperature at the time of film formation, and the resistivity decreases as the substrate temperature increases. Since the crystallization temperature of ITO is 150 ° C., it is necessary to crystallize the ITO thin film in order to form a thin film having a lower resistivity. However, it is well known that when a crystalline ITO thin film is formed by a sputtering method, a characteristic domain structure is formed in the ITO thin film. Figure 1 shows the domain structure
The crystal grains of 10 to 30 nm having well-aligned crystal orientations as shown in FIG. 1 are gathered to form a crystal grain region of 200 to 300 nm. Such a structure is not formed when an ITO thin film is formed by a vacuum deposition method. This domain structure is a collection of small grains having different crystal orientations, and is mainly composed of (111) and (110).
Or it is oriented to (100). Further, it has a feature that the resistance to plasma damage varies depending on the orientation plane. For this reason, the sputtering speed when the formed film is re-sputtered by plasma during the film formation differs. As a result, as shown in FIG.
A thin film whose surface is thick on the (100) plane and thin on the (110) plane is formed.

On the other hand, in the field of thin-film displays, in which ITO thin films are often used, especially in the field of liquid crystal displays, screens are becoming larger and finer at a rapid pace. Therefore, as a demand for a transparent conductive film, a film having a large area, low resistance, and easy microfabrication is required.

However, when a film is formed at a high substrate temperature by using a sputtering method capable of forming a uniform film over a large area, a film having a severe surface irregularity as described above is formed, and etching residues are easily generated. That is, there has been a problem that a thin film unsuitable for fine processing is formed.

[0007]

SUMMARY OF THE INVENTION An object of the present invention is to provide an IT device used for a transparent electrode or the like of a flat panel display.
Even when an O thin film is formed by a sputtering method at a substrate temperature equal to or higher than a crystallization temperature, it is an object to provide a thin film having no domain structure and having excellent etching characteristics.

[0008]

Means for Solving the Problems The inventors of the present invention have conducted intensive studies on conductive metal oxides obtained by doping ITO with a different element, and as a result, it has been confirmed that the conductive metal oxide containing gallium as a dopant.
The inventors have found that the above problems can be solved in a TO thin film, and have completed the present invention.

That is, the present invention provides a method for producing substantially indium,
It consists of tin, gallium and oxygen, where gallium is Ga /
A metal oxide sintered body characterized in that it is added at a ratio of (In + Sn + Ga) of 0.1 to 5.0 atomic%, a target using the sintered body, substantially indium, tin, A transparent conductive film comprising gallium and oxygen, wherein gallium is added at a ratio of 0.1 to 5.0 atomic% in a ratio of Ga / (In + Sn + Ga), including the transparent conductive film The present invention relates to a display device comprising:

Hereinafter, the present invention will be described in detail.

A sintered body according to the present invention, a sputtering target made of the sintered body, a thin film, and a display device containing the thin film are manufactured by the following method.

First, a mixed powder used for manufacturing a sintered body is manufactured. In order to produce this mixed powder, indium oxide powder, tin oxide powder, and gallium oxide powder may be mixed, or tin oxide solid solution indium oxide powder and gallium oxide powder may be mixed. Here, the mixing amount of tin oxide is 1.9 to 14 in the ratio of Sn / (Sn + In).
It is preferable to set the atomic percentage. More preferably, 4.6
１１11 atomic%. This is when an ITO thin film is produced by sputtering using the target of the present invention,
This is because the composition has the lowest resistivity of the film.

The amount of gallium oxide mixed is Ga /
The ratio of (In + Sn + Ga) is preferably 0.1 to 5.0 atomic%. More preferably, the content is 0.1 to 3.0 atomic%.
If the amount of gallium oxide is less than the above range,
If the effect of the present invention is weakened, the obtained thin film shows a domain structure, and if it exceeds the above range, the resistivity becomes too high, which is not appropriate. The mixing of the powder is performed by dry mixing or wet mixing using a ball mill or the like.

Next, a gallium oxide-containing ITO sintered body is manufactured using the obtained mixed powder. The method for producing the sintered body is not particularly limited, but it can be produced, for example, by the following method.

A binder or the like is added to the mixed powder obtained as described above, if necessary, and molded by a molding method such as a press method or a casting method to produce a molded body. In the case of producing a molded body by a pressing method, a predetermined mold is filled with the above-mentioned mixed powder to which a binder or the like is added as required, and then a powder press is used to prepare a 100 to 300 kg / cm ² powder.
Press at pressure of If the powder moldability is poor,
If necessary, a binder such as paraffin or polyvinyl alcohol may be added.

In the case of producing a molded article by the casting method, a slurry for producing a cast molded article is produced by adding a binder, a dispersant, and ion-exchanged water to the above-mentioned mixed powder and mixing them by a ball mill or the like. Subsequently, casting is performed using the obtained slurry. It is preferable to defoam the slurry before pouring the slurry into the mold. For defoaming, for example, a polyalkylene glycol-based defoaming agent may be added to the slurry to perform defoaming treatment in a vacuum. Subsequently, a drying process of the cast molded body is performed.

Next, if necessary, C is added to the obtained molded body.
Consolidation processing such as IP (cold isostatic pressing) is performed. At this time, the CIP pressure is 2 ton / c to obtain a sufficient consolidation effect.
m ² or more, preferably ^{2 to 5} ton / cm ² . When the initial molding is performed by a casting method, a binder removal treatment may be performed for the purpose of removing water and organic substances such as a binder remaining in the molded body after the CIP. Even when the initial molding is performed by the press method, it is desirable to perform the same binder removal treatment when a binder is used at the time of molding.

The compact thus obtained is put into a sintering furnace and sintered. As the sintering method, any method can be applied, but sintering in the air is desirable in view of the cost of production equipment and the like. However, it goes without saying that other conventionally known sintering methods such as an HP (hot press) method, a HIP (hot isostatic pressing) method and an oxygen pressure sintering method can be used. The sintering conditions can be appropriately selected, but the sintering temperature is desirably 1450 to 1650 ° C. in order to obtain a sufficient density increasing effect and to suppress the evaporation of tin oxide. The atmosphere during sintering is preferably air or a pure oxygen atmosphere. Also, the sintering time is 5 hours or more, preferably 5 to 30 in order to obtain a sufficient density increasing effect.
Desirably time. Thus, the gallium oxide-containing ITO sintered body, which is the first invention of the present application, can be manufactured.

Next, the obtained sintered body is ground into a desired shape and, if necessary, is bonded to a backing plate made of oxygen-free copper using indium solder or the like, thereby obtaining the second invention of the present application. Gallium oxide-containing ITO sputtering target is produced.

The obtained target is placed in a sputtering apparatus, and sputtering is performed by applying a dc or rf electric field using an inert gas such as argon and, if necessary, an oxygen gas as a sputtering gas. The gallium oxide-containing ITO thin film of the third invention of the present application is obtained on a substrate or a film substrate.

The thin film formed on the substrate is etched into a desired pattern as needed, and then used for a display device such as a touch panel according to the fourth invention of the present application.

[0022]

EXAMPLES Hereinafter, the present invention will be described in more detail with reference to Examples, but the present invention is not limited thereto.

Example 1 450 g of indium oxide powder, 50 g of tin oxide powder and 0.5 g of gallium oxide powder were placed in a polyethylene pot and mixed by a dry ball mill for 72 hours to prepare a mixed powder.

This mixed powder is put in a mold and is charged at 300 kg /
It was pressed at a pressure of cm ² to obtain a molded body. This compact was subjected to a densification treatment by CIP at a pressure of 3 ton / cm ² . Next, this compact was placed in a pure oxygen atmosphere sintering furnace and sintered under the following conditions.

(Sintering Conditions) Sintering temperature: 1500 ° C., heating rate: 25 ° C./Hr, sintering time: 6 hours, oxygen pressure: 50 mmH ₂ O (gauge pressure),
Oxygen linear velocity: 2.7 cm / min When the density of the obtained sintered body was measured by the Archimedes method, it was 7.08 g / cm ³ . The composition of this sintered body was analyzed using EPMA. Table 1 shows the results.

[0026]

[Table 1]

This sintered body was processed into a disk having a diameter of 4 inches and a thickness of 6 mm by a wet processing method, and bonded to a backing plate made of oxygen-free copper using indium solder to obtain a target.

This target was sputtered under the following sputtering conditions to evaluate the thin film.

(Sputtering conditions) DC power: 200 W, gas pressure: 5.0 mTorr, Ar
Gas flow rate: 50 SCCM, O ₂ gas flow rate: 0.1 SCC
M, substrate temperature = 200 ° C., film thickness = 3000 A.

The resistivity of the obtained film is 205 μΩ · cm
The transmittance at 550 nm was 86.7%.
The transmittance was measured as a transmittance including a glass substrate using air as a reference. Cor on the glass substrate
# 7059 manufactured by Ning Co. was used.

Next, the surface of the obtained thin film was subjected to SEM (Sc
Anning ElectronMicroscope
Observed using e). The results are shown in the photograph of FIG. No domain structure was observed.

Next, the composition of the film was examined using EPMA. Table 2 shows the results.

[0033]

[Table 2]

Example 2 450 g of indium oxide powder, 50 g of tin oxide powder and 17 g of gallium oxide powder were placed in a polyethylene pot and mixed by a dry ball mill for 72 hours to prepare a mixed powder.

This mixed powder is put in a mold and is weighed at 300 kg /
It was pressed at a pressure of cm ² to obtain a molded body. This compact was subjected to a densification treatment by CIP at a pressure of 3 ton / cm ² . Next, this compact was placed in a pure oxygen atmosphere sintering furnace and sintered under the same conditions as in Example 1.

The density of the obtained sintered body was measured by the Archimedes method and found to be 7.07 g / cm ³ . The composition of this sintered body was analyzed using EPMA. Table 1 shows the results.

This sintered body was processed into a disk shape having a diameter of 4 inches and a thickness of 6 mm by a wet processing method, and was bonded to a backing plate made of oxygen-free copper using indium solder to obtain a target.

The thin film was evaluated by sputtering this target under the following sputtering conditions.

(Sputtering conditions) DC power: 200 W, gas pressure: 5.0 mTorr, Ar
Gas flow rate: 50 SCCM, O ₂ gas flow rate: 0.1 SCC
M, substrate temperature = 200 ° C., film thickness = 3000 A.

The resistivity of the obtained film is 540 μΩ · cm
The transmittance at 550 nm was 86.4%.
The measurement conditions of the transmittance were the same as those in Example 1.

Next, the surface of the obtained thin film was observed using an SEM. The results are shown in the photograph of FIG. No domain structure was observed.

Next, the composition of the film was examined using EPMA. Table 2 shows the results.

Comparative Example 1 450 g of indium oxide powder and 50 g of tin oxide powder
Was placed in a polyethylene pot and mixed for 72 hours by a dry ball mill to prepare a mixed powder.

This mixed powder was placed in a mold and charged at 300 kg /
It was pressed at a pressure of cm ² to obtain a molded body. This compact was subjected to a densification treatment by CIP at a pressure of 3 ton / cm ² . Next, this compact was placed in a pure oxygen atmosphere sintering furnace and sintered under the same conditions as in Example 1.

When the density of the obtained sintered body was measured by the Archimedes method, it was 7.12 g / cm ³ . The composition of this sintered body was analyzed using EPMA. Table 1 shows the results.

The sintered body was processed into a disk having a diameter of 4 inches and a thickness of 6 mm by a wet processing method, and bonded to a backing plate made of oxygen-free copper using indium solder to obtain a target.

The thin film was evaluated by sputtering this target under the following sputtering conditions.

(Sputtering conditions) DC power: 200 W, gas pressure: 5.0 mTorr, Ar
Gas flow rate: 50 SCCM, O ₂ gas flow rate: 0.1 SCC
M, substrate temperature = 200 ° C., film thickness = 3000 A.

The resistivity of the obtained film is 200 μΩ · cm
The transmittance at 550 nm was 86.7%.
The measurement conditions of the transmittance were the same as those in Example 1. Next, the surface of the obtained thin film was observed using SEM. The results are shown in the photograph of FIG. A clear domain structure was observed.

Next, the composition of the film was examined using EPMA. Table 2 shows the results.

[0051]

The gallium oxide-containing ITO thin film of the present invention does not have a domain structure peculiar to the sputtered ITO thin film while maintaining the same specific resistance as that of ITO. It is suitable.

[Brief description of the drawings]

FIG. 1 is an SEM photograph showing the surface of a conventional ITO thin film having a domain structure.

FIG. 2 is a cross-sectional view schematically showing a cross-sectional shape near the surface of a conventional ITO thin film having a domain structure.

FIG. 3 is a diagram showing S showing the surface of the ITO thin film obtained in Example 1.
It is an EM photograph.

FIG. 4 is a diagram showing S showing the surface of the ITO thin film obtained in Example 2.
It is an EM photograph.

FIG. 5 is a diagram showing S showing the surface of the ITO thin film obtained in Comparative Example 1.
It is an EM photograph.

Claims (4)

[Claims] 1. The method according to claim 1, wherein the gallium consists essentially of indium, tin, gallium and oxygen, wherein gallium is Ga / (In + Sn + G).
A metal oxide sintered body characterized by being added at a ratio of 0.1 to 5.0 atomic% in the ratio of a). 2. The method according to claim 1, wherein the gallium consists essentially of indium, tin, gallium and oxygen, wherein gallium is Ga / (In + Sn + G).
A sputtering target using a metal oxide sintered body, which is added at a ratio of 0.1 to 5.0 atomic% in the ratio of a). 3. The method according to claim 1, wherein the gallium consists essentially of indium, tin, gallium and oxygen, wherein gallium is Ga / (In + Sn + G).
A transparent conductive film, which is added at a ratio of 0.1 to 5.0 atomic% in the ratio of a). 4. A display device comprising the transparent conductive film according to claim 3.