JPH06659B2 - Method for manufacturing sputtering target for transparent conductive film - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a method for producing a sputtering target used when forming a transparent conductive film such as an EL display, a liquid crystal display surface heating element, and a touch panel by a sputtering method. is there.

(Prior Art) In recent years, a transparent conductive film has been used in the field of display elements and the like with the development of thinning technology. At present, indium oxide-tin oxide (hereinafter referred to as ITO) is often used as a material for the transparent conductive film for reasons such as stability and high light transmittance. In addition, as a method for producing a transparent conductive film made of ITO, a vapor deposition method, a reactive sputtering method using an indium-tin metal target, and a sputtering method using an ITO target are known. The sputtering method using an ITO target has become the mainstream. In addition, as the size of the sputtering apparatus increases, the size of the target is required to increase.

Conventionally, an ITO target is obtained by obtaining an ITO molded body from ITO powder by a die press molding method and then firing the molded body. Is difficult to obtain,
When the target is increased in size, the obtained target is warped or cracked. Therefore, at present, several target pieces are obtained by a die press molding method, and these pieces are joined and used. However, in this way,
It is necessary to manufacture an expensive die each time the shape is different, and the obtained large target also has a problem that abnormal discharge occurs during sputtering due to the joint portion.

(Problems to be Solved by the Invention) An object of the present invention is to provide a method for manufacturing a large ITO sputtering target.

(Means for Solving the Problem) As a result of intensive studies for solving the above-mentioned problems, the present inventors have found that a large-sized ITO target can be easily obtained by using the slurry casting method. The present invention has been completed. That is, the present invention provides a molded body of indium oxide-tin oxide with a slurry concentration of 70% or more,
It is a method for producing a sputtering target for transparent conductive film, which is obtained by a slurry casting molding method under a molding pressure of 0.5 kg / cm ² or more, and the molded body is fired.

The slurry casting molding method in the present invention means that a slurry obtained by mixing a raw material powder with a solvent, a dispersant and a binder is poured into a water-absorbing porous molding die such as a gypsum mold under normal pressure or pressure. And then the solvent is removed to mold. At this time, by changing the size and shape of the porous mold, it is possible to obtain a large ITO molded body having a desired shape.

In the present invention, when a slurry is obtained, water is usually used as the solvent, examples of the dispersant include polycarboxylic acid type, and examples of the binder include acrylic emulsion type. Not limited to. As the raw material powder, an ITO powder obtained by a mixing method, a coprecipitation method or the like is used, and an ITO powder containing 70% by weight or more of indium oxide is usually used. Furthermore, in order to improve the conductivity and transparency of the transparent conductive film formed from the obtained target, ITO powder containing a third component added in addition to indium oxide and tin oxide may be used.

The slurry concentration at this time is preferably 70% or more, more preferably 75 to 80%. If the slurry concentration is less than 70%, cracking tends to occur during the production of the target.

For molding, the slurry is 0.5 kg / cm ² or more, and 2.
It is preferable to perform pressure casting in which the pressure is 0 kg / cm ² or more, and the mixture is poured into the mold so that the density of the target obtained becomes high and the warpage becomes small.

Then, the ITO molded body is fired to obtain an ITO target having a desired size and shape. At this time, the firing temperature is preferably 1300 to 1450 ° C. for 1 hour or more. Further, it is preferable to subject the ITO molded body to cold isostatic pressing or the like before firing to consolidate the ITO molded body so that an ITO target having a large relative density can be obtained.

(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 4950 g of commercially available indium oxide powder and 5 tin oxide powder
50 g, polycarboxylic acid type dispersant (solid content 40%) 10
0 g, acrylic emulsion binder (solid content 40
%) 100 g and pure water 1740 g are mixed in a 10 nylon pot with a resin ball containing an iron core having a diameter of 15 mm for 16 hours by a rotary ball mill to obtain a slurry concentration of 75%.
I got the mud.

Then, after thoroughly defoaming the obtained slurry, the inner size is 180
It was poured into a gypsum mold of × 1080 × 10 ^t and cast-molded at a casting pressure of 0.5 kg / cm ² to obtain an ITO molded body.

Thereafter, the obtained molded body is debindered, and 13
It was fired at 50 ° C. for 3 hours to obtain a sintered body, which was processed by electric discharge machining and surface grinding to obtain a 150 × 900 × 6 ^t ITO target. The relative density of the obtained target is 60%
Met.

Example 2 Sludge casting was carried out using a gypsum mold having an internal size of 180 × 620 × 8 ^t , and after sintering, the sintered body obtained was 15
An ITO target was obtained in the same manner as in Example 1 except that an ITO target of 4 × 508 × 6 ^t was obtained. The relative density of the obtained target was 63%.

Comparative Example 1 4950 g of commercially available indium oxide powder and tin oxide powder 5
50 g, polycarboxylic acid type dispersant (solid content 40%) 10
0 g, acrylic emulsion binder (solid content 40
%) 100 g and pure water 2885 g are mixed in a 10-nylon pot with a resin ball containing an iron core having a diameter of 15 mm by a rotary ball mill for 16 hours to obtain a slurry concentration of 65%.
An ITO powder slurry of was obtained.

After sufficiently defoaming the slurry, the inside dimension is 180 mm x 1080
mm × 10 mm gypsum mold, casting pressure 0.5 kg /
A molded body of ITO was prepared by performing pre-molding by pressure casting at cm ² , but the molding strength was weak, and cracks were formed when the mold was removed from the mold.

Comparative Example 2 4950 g of commercially available indium oxide powder and tin oxide powder 5
50 g, polycarboxylic acid dispersant (solid content 40%) 100
g, acrylic emulsion binder (solid content 40
%) 100 g and 1740 g of pure water were mixed in a 10-nylon pot for 16 hours using a resin ball with an iron core having a diameter of 15 mm by a rotary ball mill to obtain a slurry concentration of 75%.
An ITO powder slurry of was obtained.

After sufficiently degassing the slurry, the inner size is 170 mm x 1080
mm × 10 mm gypsum mold, casting pressure 0.1 kg /
Preforming was performed by pressure casting at cm ² , and an ITO molded body was prepared. However, unevenness of inking occurred and many wrinkle-like fine cracks were formed in the ITO molded body.

(Effect of the Invention) As described above, according to the present invention, a large-sized and arbitrarily shaped ITO target can be easily obtained. In addition, since it can be obtained without joining a large target, the obtained target is free from solder bleeding during sputtering or abnormal discharge associated therewith, and it is possible to form a transparent conductive film of good film quality. Become.

Claims (1)

[Claims] 1. A molded product containing indium oxide-tin oxide, having a slurry concentration of 70% or more and a molding pressure of 0.5 kg / cm ^2.
A method for producing a sputtering target for a transparent conductive film, which is obtained by a sludge casting molding method under the above conditions and is then fired.