JP4758697B2 - Manufacturing method of IZO sputtering target - Google Patents

Description

  The present invention relates to a method for producing an IZO sputtering target mainly composed of indium oxide and zinc oxide or a powder thereof.

Liquid crystal display devices and electroluminescent display devices are widely used in display devices such as mobile phones, personal computers, word processors, and televisions because of their excellent display performance and low power consumption.
As the transparent conductive film used in these display devices, an indium tin oxide (hereinafter abbreviated as ITO) film dominates. This is because the ITO film has high light transmittance, excellent conductivity, etching processing, and excellent adhesion to the substrate. Usually, this ITO film is formed by sputtering, ion plating, or vapor deposition.

However, ITO has excellent performance in terms of the above properties, but a transparent conductive film formed using an ITO target uses a strong acid such as aqua regia, hydrochloric acid, hydrobromic acid, etc. for etching. Since it is necessary, there is a problem that even the wiring material in the thin film type liquid crystal display device is etched.
In addition, since ITO has crystallinity, it is etched from the crystal grain interface portion of the transparent conductive film during the etching process. As a result, the crystal particles are left behind in the etched portion of the transparent conductive film, which causes a display defect due to conduction when used as a display element.

  In view of this, studies on materials using combinations other than ITO have been made. For example, a material mainly composed of zinc oxide and tin oxide, a material obtained by adding antimony to tin oxide, a material obtained by adding aluminum to zinc oxide, or IZO mainly composed of indium oxide and zinc oxide have been proposed ( For example, see Patent Document 1 and Patent Document 2). Among them, IZO, which contains indium oxide and zinc oxide as main components, has attracted attention because it has a feature that the etching rate is higher than that of ITO.

  In general, an ITO sputtering target is manufactured through many steps of mixing, pulverizing, drying, calcining, pulverizing, granulating, molding, and sintering powders of indium oxide and zinc oxide (for example, see Patent Document 3). . The production of the sputtering target over many processes leads to a decrease in productivity and increases the cost, but improvement such as a reduction in the process has not been sufficiently studied. Even in the production of an IZO sputtering target, the conventional production process as described above has been followed, and there has been no improvement in production, such as a reduction in the production process. Is desired.

JP-A-8-171824 JP 2000-256059 A International Publication No. WO2003 / 14409

  Under such circumstances, the present invention improves productivity and reduces manufacturing costs by reducing the process and reducing the sintering temperature while maintaining the characteristics as an IZO sputtering target in the production of an IZO sputtering target. It is an object of the present invention to provide a manufacturing method that can reduce the above.

  As a result of intensive studies to achieve the above object, the present inventors have used indium oxide powder and zinc oxide powder having specific properties, or raw material powders mainly composed of these powders. It has been found that the manufacturing process can be reduced and the sintering temperature can be lowered while maintaining the characteristics as an IZO sputtering target. The present invention has been completed based on such findings.

That is, the present invention
(1) A mixing and pulverizing step in which fine powder is obtained by mixing and pulverizing indium oxide powder and zinc oxide powder, or a raw material powder mainly composed of these powders, and a molding step in which the fine powder is molded to obtain a molded product A method for producing an IZO sputtering target, comprising a sintering step of obtaining a sintered body by sintering the molded product under pressure at 1100 to 1250 ° C. in an oxygen atmosphere. specific surface area of 8~10m ² / g, a manufacturing method of the IZO sputtering target a specific surface area of 10 m ² / g or more of the zinc oxide powder,
(2) A mixing and pulverizing step of mixing and pulverizing indium oxide powder and zinc oxide powder or raw powders mainly composed of these powders to obtain fine pulverization, and a molding step of forming the fine powder to obtain a molded product A method for producing an IZO sputtering target, comprising a sintering step of obtaining a sintered body by sintering the molded product under pressure at 1100 to 1250 ° C. in an oxygen atmosphere. IZO sputtering in which the median diameter of the particle size distribution is 1 to 2 μm, the median diameter of the particle size distribution of the zinc oxide powder is 65 nm to 0.2 μm, and the average median diameter after the mixing and grinding step is 0.5 to 1 μm Target manufacturing method,
(3) The method for producing an IZO sputtering target according to the above (1) or (2), which is not calcined before the molding step ,
(4) The method for producing an IZO sputtering target according to any one of (1) to (3) above, wherein the sintered body has a density of 6.5 g / cm ³ or more, and
(5) The IZO sputtering target according to any one of (1) to (4) above, wherein the amount of the indium oxide powder and the zinc oxide powder used is 75:25 to 95: 5 by weight. Manufacturing method,
(6) The method for producing an IZO sputtering target according to any one of (1) to (5) above, wherein the sintering step is performed under a pressure exceeding atmospheric pressure to 0.5 MPa.
Is to provide.

  According to the present invention, in the production of an IZO sputtering target, it is possible to improve the productivity and reduce the manufacturing cost by reducing the process and reducing the sintering temperature while maintaining the characteristics as the IZO sputtering target. A manufacturing method can be provided.

[Raw material powder]
The present invention makes it possible to reduce the manufacturing process and lower the sintering temperature by using indium oxide powder and zinc oxide powder having specific properties or using raw material powders mainly composed of these powders. To do.
The specific surface area of the indium oxide powder and zinc oxide powder used as a raw material in the present invention, in order to reduce expression of defect called white spots of the sputtering target surface (white spots irregularities), each 8~10m ² / g and 10 m ² / G or more.
In addition, the median diameters of the particle size distributions of the indium oxide powder and zinc oxide powder used as raw materials in the present invention are required to be 1 to 2 μm and 65 nm to 0.2 μm, respectively, in order to reduce the appearance of white spots. The average median diameter of the fine powder after the mixing and pulverizing step is preferably as fine as possible, but is pulverized to be 0.5 to 1 μm. Within this range, a high-density IZO sputtering target can be obtained, and the amount of impurities mixed from the pulverizer during pulverization can be reduced. In addition, it is preferable that the powder used as the raw material satisfies both the specific surface area and the median diameter.

The amount of the indium oxide powder and zinc oxide powder used is preferably 75:25 to 95: 5, and more preferably 80:20 to 94: 6, by weight.
As long as the raw material of the IZO sputtering target concerning manufacture of this invention has an indium oxide and a zinc oxide as a main component, you may add another component in order to improve the characteristic of this target. For example, a positive tetravalent element such as tin, zirconium, titanium, hafnium, germanium, cerium or the like can be added in an amount of about 100 to 2000 ppm in order to reduce the bulk electrical resistance value of the IZO sputtering target.

[Production method]
The IZO sputtering target is manufactured as follows. Fine powder obtained by wet milling a mixture of indium oxide powder and zinc oxide powder, or a mixture containing these powders as a main component, press-sintered particles using a spray drier, etc., and then sintered. It can be manufactured by cutting a sintered body of the object.
The mixing and pulverizing step refers to the indium oxide powder and the zinc oxide powder, or the raw material powder containing these powders as a main component, uniformly using a wet mixing and pulverizing machine such as a wet ball mill, a bead mill, or an ultrasonic wave. This is a step of mixing and grinding to obtain fine powder. The particle size of the pulverized fine powder is adjusted from the viewpoint of reducing the density of the IZO sputtering target as described above and the amount of impurities mixed from the pulverizer during pulverization.
Next, the obtained fine powder is dried. For drying the fine powder, a spray dryer, a general powder dryer, or the like can be used.
The dried fine powder is subjected to a molding step of filling a mold and press-molding it into a desired shape using a general cold press machine or the like. The press molding can be performed using a uniaxial press, a cold isostatic press (CIP), or the like.
The molded product obtained by press molding becomes a sintered body for an IZO sputtering target through a sintering process. Sintering is performed in an oxygen atmosphere. The oxygen atmosphere means that the oxygen concentration is 21% to less than 50%, preferably 21% to less than 40%. If it is in this range, it is possible to sinter efficiently and the firing furnace will not burn out. Sintering can also be performed in an air atmosphere. In addition, the sintering is performed at a pressure exceeding atmospheric pressure to 0.5 MPa under pressure for the purpose of increasing the sintering density and preventing the cost of a sintering apparatus including a sintering furnace from increasing.
Sintering temperature is 1100-1250 degreeC, Preferably it is 1150-1250 degreeC, if it exists in this range, a sintering density will become high and manufacturing cost can be reduced. The sintering time is 2 to 48 hours, preferably 10 to 36 hours, in order to increase the sintered density and reduce the manufacturing cost, and the preferred temperature increase rate during sintering is 2 to 24 ° C./min. .
In order to produce a sputtering target from the sintered body of the obtained molded product, the sintered body is cut into a shape suitable for mounting on a sputtering apparatus, and a mounting jig is attached thereto. . At this time, mirror finishing may be performed to improve the average surface roughness of the target. For this mirror finishing, a general polishing method such as chemical polishing, mechanical polishing, chemical mechanical polishing, or the like can be used.

Thus, by using indium oxide powder and zinc oxide powder having specific properties, or using raw material powders mainly composed of these powders, calcining generally performed before the molding process by press molding is performed. A sintered body for an IZO sputtering target having a high density of 6.5 g / cm ³ or more can be obtained without going through the steps and lowering the sintering temperature. The IZO sputtering target produced by cutting the obtained sintered body has a high density and has excellent characteristics in which defects called white spots (white spot unevenness) do not exist on the target surface. The manufacturing method of the present invention can improve productivity and reduce manufacturing costs by reducing the number of steps and lowering the sintering temperature while maintaining the characteristics of the IZO sputtering target.

  The IZO sputtering target obtained by the production method of the present invention has the above-described characteristics, thereby suppressing the occurrence of black precipitates (projections) called nodules on the target surface when the film is formed by the sputtering method. To do. Therefore, it does not cause a decrease in the film forming speed, and no nodule scattered by abnormal discharge does not cause foreign matter to be mixed into the transparent conductive film, thus enabling stable sputtering and excellent transparent film characteristics. Can be obtained.

EXAMPLES Next, although an Example demonstrates this invention further in detail, this invention is not limited at all by this example.
Example 1
90 parts by weight of indium oxide powder having a specific surface area of 9 m ² / g and 10 parts by weight of zinc oxide powder having a specific surface area of 12 m ² / g were mixed and ground using a wet bead mill for 24 hours. As the medium, 1 mmφ zirconia beads were used. After mixing and grinding, the fine powder obtained by drying with a spray dryer was filled in a mold and press-molded at 1 t / cm ² using a cold press and a cold isostatic press. The obtained molded product was placed in a firing furnace and sintered at 1230 ° C. for 24 hours in an oxygen atmosphere having an oxygen concentration of 25% under a pressure of 0.15 MPa. The obtained sintered body for an IZO sputtering target was a sintered body having a high density of 6.72 g / cm ³ even though there was no calcining step.

Example 2
90 parts by weight of indium oxide powder having a median diameter of 1.5 μm and 10 parts by weight of zinc oxide powder having a median diameter of 0.1 μm are mixed and ground for 24 hours using a wet bead mill, and the median diameter after grinding is reduced to 0. .8 μm. As the medium, 1 mmφ zirconia beads were used. After mixing and grinding, the fine powder obtained by drying with a spray dryer was filled in a mold and press-molded at 1 t / cm ² using a cold press and a cold isostatic press. The obtained molded product was placed in a firing furnace and sintered at 1180 ° C. for 24 hours in an oxygen atmosphere with an oxygen concentration of 30% under a pressure of 0.12 MPa. The obtained sintered body for IZO sputtering target was a sintered body having a high density of 6.65 g / cm ³ , even though there was no calcining step.

Comparative Example 1
90 parts by weight of indium oxide powder having a specific surface area of 9 m ² / g and 10 parts by weight of zinc oxide powder having a specific surface area of 3 m ² / g were mixed and ground using a wet bead mill for 24 hours. As the medium, 1 mmφ zirconia beads were used. After mixing and grinding, the fine powder obtained by drying with a spray dryer was filled in a mold and press-molded at 1 t / cm ² using a cold press and a cold isostatic press. The obtained molded product was charged into a firing furnace and sintered in an air atmosphere at 1400 ° C. and atmospheric pressure for 24 hours. The density of the obtained sintered body for the IZO sputtering target was as low as 6.10 g / cm ³ .

Comparative Example 2
90 parts by weight of indium oxide powder having a median diameter of 1.5 μm and 10 parts by weight of zinc oxide powder having a median diameter of 1.0 μm are mixed and ground for 24 hours using a wet bead mill, and the median diameter after grinding is 1 .2 μm. As the medium, 1 mmφ zirconia beads were used. After mixing and grinding, the fine powder obtained by drying with a spray dryer was filled in a mold and press-molded at 1 t / cm ² using a cold press and a cold isostatic press. The obtained molded product was placed in a firing furnace and sintered in an air atmosphere at 1200 ° C. and atmospheric pressure for 24 hours. The density of the obtained sintered body for the IZO sputtering target was as low as 6.00 g / cm ³ .

Comparative Example 3
In Comparative Example 1 and Comparative Example 2, after mixing and pulverizing and before press molding, calcination was performed at 1200 ° C. for 2 hours in an air atmosphere, and the obtained calcination powder was pulverized using a wet bead mill. In the same manner as in Example 1 and Comparative Example 2, a sintered body for an IZO sputtering target was obtained. The density of the obtained sintered body was as high as 6.73 g / cm ³ and 6.73 g / cm ³ , respectively. The increase in density is due to calcination, and a sintered body having a higher density than those of Example 1 and Example 2 was obtained. Sex declined.

According to the present invention, in the production of an IZO sputtering target, while maintaining the characteristics as an IZO sputtering target, the number of steps is reduced, and the productivity is improved by lowering the sintering temperature, thereby reducing the production cost. be able to.

Claims (6)

A mixing and pulverizing step for obtaining fine powder by mixing and pulverizing indium oxide powder and zinc oxide powder, or raw material powders mainly composed of these powders, a molding step for obtaining a molded product by molding the fine powder, and the molding A method for producing an IZO sputtering target comprising sintering a product under pressure at 1100 to 1250 ° C. in an oxygen atmosphere to obtain a sintered body, wherein the specific surface area of the indium oxide powder is 8~10m a ² / g, the production method of the IZO sputtering target a specific surface area of 10 m ² / g or more of the zinc oxide powder.   A mixing and pulverizing step of mixing and pulverizing indium oxide powder and zinc oxide powder or raw powders mainly composed of these powders to obtain fine pulverization, a molding step of molding the fine powder to obtain a molded product, and the molding A method of manufacturing an IZO sputtering target comprising sintering a product under pressure at 1100 to 1250 ° C. in an oxygen atmosphere to obtain a sintered body, wherein the particle size distribution of the indium oxide powder is Production of an IZO sputtering target having a median diameter of 1 to 2 μm, a median diameter of a particle size distribution of the zinc oxide powder of 65 nm to 0.2 μm, and an average median diameter after the mixing and grinding step of 0.5 to 1 μm Method.   The method of manufacturing an IZO sputtering target according to claim 1, wherein the calcination is not performed before the molding step. The density of the said sintered compact is 6.5 g / cm < ³ > or more, The manufacturing method of the IZO sputtering target in any one of Claims 1-3 characterized by the above-mentioned. The method for producing an IZO sputtering target according to any one of claims 1 to 4, wherein the amount of the indium oxide powder and the zinc oxide powder used is 75:25 to 95: 5 by weight. The method for producing an IZO sputtering target according to any one of claims 1 to 5, wherein the sintering step is performed under a pressure exceeding atmospheric pressure to 0.5 MPa.