JP2000080469A - Ito sputtering target material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a target material for a transparent conductive film of high performance composed of ITO of high density under the ordinary compacting and sintering conditions of ceramics by using ITO contg. a specified amt. of indium oxide having specified surface arer value as the raw material to form a sintered body. SOLUTION: A target obtd. by executing sintering using ITO as the raw material is subjected to sputtering to form a transparent conductive film. As to IN2O3 in this sintering raw material, the specific surface area value is controlled to >=20 m2/g, preferably to 20 to 60 m2/g, most preferably to 20 to 40 m2/g, the average crystal particle size is limited to an ultrafine range of about 0.01 to 0.05 μm, and, it is used by 85 to 95 wt% in the whole raw material. This raw material powder composed of In2O3 and SnO2 is subjected to compacting and sintering in such a manner that the cold compacting pressure is 1 to 3 ton/cm2, and the sintering temp. in the atmosphere is 1,450 to 1,600 deg.C to obtain an ITO sputtering target material composed of the sintered body having >=83.5%, preferably 83.5 to 95% relative density.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to a high-density ITO (indium oxide containing tin, abbreviated as Indium-Tin-Oxide) sputtering target material for forming a transparent conductive film.

[0002]

2. Description of the Related Art With the development of thin film technology, transparent conductive films have been used for solar cells, liquid crystal displays and the like in the field of display devices and the like. Among them, In ₂ O _3. Since the SnO ₂ (ITO) film has characteristics such as light transmittance and conductivity, it is widely used as an oxide-based transparent conductive film.

As a method for producing a transparent conductive film made of ITO, there are a coating method, a CVD method, a vacuum evaporation method, an electron beam evaporation method, a reactive sputtering method using an indium-tin metal target, and a sputtering method using an ITO target. Methods and the like have been proposed, and among them, the sputtering method using an ITO target is currently the mainstream.

The following methods have been proposed as a method of forming the ITO target, but there are still many problems to be solved. A) Hot pressing method: (See Japanese Patent Application Laid-Open No. 61-55811) In this method, the powder material of In ₂ O ₃ and SnO ₂ is heated to a high temperature and a high pressure (about 1 × 10 ³ ° C. at 1 ton / cm ² ). Squeezing to produce a plate-like molded body, so that the density can be easily increased, but the equipment and the mold become extremely expensive, and the productivity is also 1 to 10 sheets / 1-2.
It is a very expensive target because it is as bad as a day.

[0005] b) Cold isostatic pressing method:
This is a method in which an ITO powder is charged into a mold together with a binder, pressurized to form a preform, and the preform is degreased, repressed at about 5 ton / cm ² , and then fired. In addition, the manufacturing process is extremely complicated, requires many steps, and further requires high-pressure treatment, which is technically and economically problematic and impractical.

C) Cast molding method: (JP-A-1-2905)
No. 50) A method of molding a molded product of indium oxide-tin oxide by a slurry casting method and firing the molded product. In this method, if the flow characteristics of the slurry are optimized, the sinterability of the powder is reduced. However, there is a natural limit to achieving high density.

[0007] In order to realize the densification of the ITO targets listed above, a hot pressing method is used,
By re-pressing at a high pressure of ^{3 to 5} ton / cm ² or by casting a high-concentration slurry into a mold and casting, a compact having a relative density of 70% or more can be obtained. There are many problems to be solved.

Further, the relative density is about 60% in a normal cold pressure molding method or a normal pressure sintering method, which cannot be said to be a high density.
It cannot achieve its intended purpose.

[0009]

SUMMARY OF THE INVENTION In view of the above situation, the present invention has examined the high-density ITO target material by the cold pressing method and the normal pressure sintering method, and Alternatively, it has been found that the average crystallite diameter constituting the powder has a significant effect on the target sintered body density, and the specific surface area value of the raw powder (indium oxide which is a main raw material) during the production of the ITO target (or By limiting the crystallite diameter to the range of fine particles, a high-density ITO target material obtained under ordinary ceramic forming and firing conditions without special high-temperature and high-pressure treatment was found.

[0010]

That is, according to the present invention, indium oxide having a specific surface area value of 20 m ² / g or more is contained in 85% of all raw materials.
The present invention relates to an ITO sputtering target material made of a sintered body having a relative density of 83.5% or more using up to 95% by weight. Next, the target material of the present invention will be described in detail.

Based on the above findings, the present inventors have repeated many trials and experiments to increase the specific surface area of indium oxide as a raw material powder, in other words, to reduce the average crystallite diameter of the raw powder powder to ultra-fine. Cold forming pressure: 1 to 3 ton / cm ² , firing temperature: 1450 ° C in air
It has been found that a sintered body having a relative density of 83.5% to 95% can be obtained by molding and firing at a temperature of 1600 ° C. or less, which exceeds 1600 ° C.

The specific surface area of the raw material powder is 20 m ² /
g or more, preferably 20 to 60 m ² / g, most preferably 20 to 40 m ² / g. By using indium oxide which is a raw material powder in this condition range, a sintered body having a high relative density can be obtained. It is done.

As the indium oxide powder used in the present invention, a commercially available indium oxide powder having a specific surface area of 20 m ² / g or more, in other words, an average crystallite diameter in the range of 0.01 to 0.05 μm is used. A mixture of powder and tin oxide powder at a predetermined ratio or a powder produced by a coprecipitation method may be used, and a small amount of a third component may be added for improving conductivity and light transmittance.

As for the compounding ratio of indium oxide, 85 to 95 wt% of the whole raw material is necessary to obtain a sintered body having a relative density of 83.5% or more.

Next, the molding method may be cold pressure molding using a mold or cold isostatic pressing using a rubber mold. The specific surface area of the raw material powder is 20 m ² / g or more. Therefore, the viscosity of the slurry becomes high, and the casting method is not appropriate.

Examples of the molding pressure in molding, cold-molding pressure 1~3ton / cm ^2, in order to further the relative density of the sintered body 90% or more is the preferred 1.5 ton / cm ² or more. Even if the molding pressure is less than 1 ton / cm ² , the intended purpose can be achieved for a time, for example, the molding pressure is 250 kg / cm ² ,
The relative density of the sintered body manufactured under the conditions of a sintering temperature of 1500 ° C. and a sintering time of 60 minutes is about 73%.

The present invention is constituted as described above, and has a specific surface area of 20 m ² / g or more, preferably 20 to 60 m ² / g,
Most preferably, a raw material powder consisting of 85 to 95 wt% of indium oxide powder of 20 to 40 m ² / g, 5 to 15 wt% of tin oxide, and other unavoidable impurities is used, and a pressure of 1 to 3 tons is applied by a cold pressing method. / cm ² , and sintered at atmospheric pressure sintering at a temperature exceeding 1450 ° C.
% Or more high-density ITO sputtering material.

The fine powder having a specific surface area of 20 to 60 m ² / g was examined by a transmission electron microscope to find that the primary
The primary particles were referred to as “crystallites”. That is, a powder having an average crystallite diameter of 0.01 to 0.05 μm corresponds to a powder having a specific surface area of 20 to 60 m ² / g. Next, the present invention will be described with reference to examples.

[0019]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Example 1 190 g of indium oxide fine powder and 10 g of tin oxide fine powder having a specific surface area of 36 m ² / g were collected.
0 wt% of water was added as a binder and mixed in an agate automatic mortar for 5 hours to obtain ITO powder.

After the ITO powder is granulated with a sieve having an opening of 200 μm, it is filled into a mold having an inner diameter of 25.4 mmφ to form pellets of about 10 g, and subjected to cold pressure molding at 1.5 ton / cm ² , and
It was fired at 00 ° C. for 1 hour under normal pressure to produce a sintered body. The relative density of this sintered body was 90.2%.

The same operation is performed using the same raw material powder as described above, and the molded body is molded at a press molding pressure of 3.0 ton / cm ² and fired at 1500 ° C. for 1 hour under normal pressure to obtain a sintered body. Manufactured. As a result, the relative density of the sintered body was 94.5%.

REFERENCE EXAMPLE Further, the same operation was performed using the same raw material powder as in the above-mentioned example, and after molding at a pressure molding pressure of 0.25 ton / cm ² ,
It was fired at 1500 ° C. for 1 hour under normal pressure to produce a sintered body. As a result, the relative density of the sintered body was 73.0%.

EXAMPLE 2 3800 g of indium oxide having a specific surface area of 36 m ² / g and 200 g of tin oxide fine powder were sampled.
After adding water by weight as a binder and mixing and granulating in the same manner as in Example 1, filling in a 150 × 450 mm mold, cold pressing at a pressure of 1 ton / cm ² , and 1500
The sintered body was manufactured by baking at normal pressure for 3 hours at ℃. The relative density of this sintered body was 84.0%.

Example 3 190 g of indium fine powder and 10 g of tin oxide fine powder having a specific surface area of 55 m ² / g were collected, and 10 wt.
% Of water was added as a binder and mixed in an agate automatic mortar for 5 hours to obtain ITO powder. The ITO powder was sifted through a sieve having an opening of 200 μm, granulated, filled in a mold having an inner diameter of 25.4 mmφ with about 10 g, cold-formed at a molding pressure of 1.5 ton / cm ² , and then subjected to normal pressure at 1500 ° C. for 1 hour. It was sintered to produce a sintered body. The relative density of this sintered body was 83.5%.

Comparative Example 1 Fine powders of indium oxide having specific surface areas of 6 m ² / g and 8 m ² / g were prepared, and fine powder of tin oxide was added to each fine powder of indium oxide.
wt.%, and water was added as a binder so as to be 10 wt.% each. Then, as in Example 1, each raw material powder was mixed in an agate automatic mortar for 5 hours.
O powder was obtained.

The ITO powder is sieved through a sieve having a mesh size of 200 μm, granulated, and placed in a mold having an inner diameter of 25.4 mmφ for about 10 minutes.
g and cold-press molding at a molding pressure of 1 ton / cm ² ,
The resultant was fired at 1500 ° C. for 1 hour under normal pressure to produce a sintered body.

The relative density of each sintered body is 6 m ² / g specific surface area.
The relative density of the sintered body using indium oxide as the main raw material powder is
56.3%, and the relative density when the specific surface area is 8 m ² / g is 60.
1%.

[0028]

As described above, according to the method of the present invention, a simple process similar to a normal ceramics manufacturing process can be carried out without using a special high-temperature and high-pressure treatment or a special expensive device as in the prior art. Since the molding pressure is low and the productivity is as high as about 20 to 30 sheets per hour, mass production at low cost becomes possible.

Further, according to the present invention, a high-density transparent conductive film sputtering target material that could not be achieved by the conventional method can be realized by the normal pressure sintering method.

Further, according to the present invention, since the reached relative density is high, a high quality transparent conductive film target can be manufactured.

Continued on the front page (72) Inventor Hiroaki Urano 277-1, Tobukicho, Hachioji-shi, Tokyo Inside Dowa Mining Co., Ltd. Central Research Laboratory (72) Inventor Riko Tanaka 277-1, Tobukicho, Hachioji-shi, Tokyo Dowa Mining Co., Ltd. Inside the research institute (72) Inventor Masaharu Abe 277-1, Tobukicho, Hachioji-shi, Tokyo Dowa Mining Co., Ltd.

Claims (1)

[Claims] 1. A relative density obtained by using indium oxide having a specific surface area value of 20 m ² / g or more in a proportion of 85 to 95% by weight of all raw materials.
ITO sputtering target material consisting of a sintered body of 83.5% or more.