JP2001303239A - Method for manufacturing ito target - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce the number of pores by improving dispersibility of tin and to efficiently manufacture a target of ITO sintered compact reduced in the occurrence of nodules and suitably used for deposition of ITO thin film and, hereby, to suppress deterioration in film quality and reduction in the productivity of film. SOLUTION: The ITO target can be manufactured by mixing a disperse solution in which metastannic acid is dispersed with a disperse solution in which indium hydroxide is dispersed to form a mixed disperse solution, drying and calcining this mixed disperse solution, and subjecting a green compact of the resultant oxide powder mixture to sintering.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing an ITO target for sputtering used for forming an ITO film.

[0002]

2. Description of the Related Art An ITO (composite oxide mainly containing indium-tin) film is widely used as a transparent electrode (film) of a display device mainly for a liquid crystal display. The method of forming the ITO film is generally performed by a means generally called a physical vapor deposition method such as a vacuum vapor deposition method or a sputtering method. In particular, it is often formed using a magnetron sputtering method from the viewpoint of operability and film stability.

[0003] The formation of a film by the sputtering method involves physically colliding positive ions, such as Ar ions, with a target provided on a cathode, and releasing the material constituting the target with the collision energy, thereby forming a film on the side of the anode facing the anode. By laminating a film having substantially the same composition as the target material on the substrate. The coating method by the sputtering method is characterized in that a thin film of angstrom unit to a thick film of several tens μm can be formed at a stable film forming rate by adjusting the processing time, the supplied power, and the like.

A particular problem when forming an ITO film is that fine projections called nodules are generated in the erosion portion of the target surface due to sputtering, which causes abnormal discharge and a decrease in sputter rate. cause. Further, coarse particles float in the sputtering chamber, which adhere to the formed film and cause deterioration in quality. As described above, in actual production, it is necessary to periodically remove nodules generated in the target, which significantly reduces productivity.

[0005] From the above, it has been proposed to increase the density of the sintered body as much as possible and to reduce the number of pores in the sintered body as a method of reducing nodules. However, this requires sintering in a pressurized state, and there is a problem that the equipment needs to be further enlarged to further increase the density, and thus cannot be said to be an industrially efficient method. .

[0006] In order to solve the above-mentioned problem, as a result of examining pores inside the sintered body, it was found that tin oxide was segregated on the pore inner wall and its periphery. The cause of such segregation is that tin oxide, which is a raw material of ITO, is agglomerated. Therefore, the pores can be reduced by improving the dispersibility of tin, whereby it is possible to efficiently manufacture an ITO sintered body target with less generation of nodules.

Generally, an ITO sintered body target is manufactured by pulverizing and mixing indium oxide and tin oxide, and molding and sintering the obtained mixed powder. Dry or wet mixing with a ball mill, V-type mixer, or ribbon type mixer is used for the pulverization and mixing of indium oxide and tin oxide, but mixing takes a long time, and mixing for a long time is performed. However, even in such a case, there is a problem that it is not always possible to obtain a good tin dispersion state. In addition, in order to obtain the indium oxide and tin oxide, a precipitant is added to a solution in which the indium salt and the tin salt are dissolved,
A method was used in which respective precipitates of indium hydroxide and metastannic acid were obtained (neutralization method), washed and roasted to obtain respective powders of indium oxide or tin oxide. For reference, FIG. 3 shows a flow of a step (neutralization method) according to a conventional manufacturing method. However, in the case of this neutralization method, there is a problem that a production cost is increased because a neutralized waste liquid is generated.

Similarly, in order to obtain indium oxide and tin oxide, electrolysis is performed using indium metal and tin metal as anodes to obtain respective precipitates of indium hydroxide and metastannic acid (electrolytic method), which are washed. And roasting to obtain respective powders of indium oxide and tin oxide. This electrolysis method was different from the above-mentioned neutralization method, and an excellent result that no waste liquid was generated was obtained. However, both the neutralization method and the electrolytic method are based on a method in which indium oxide and tin oxide are mixed, molded and sintered, and a problem that a good tin dispersion state cannot be obtained. was there.

Therefore, for the purpose of improving the dispersion state of tin, an indium salt and a tin salt are previously mixed, a precipitant is added to the mixed solution, and a mixed precipitate of indium hydroxide and metastannic acid is formed. At the same time, a method of obtaining a mixed powder of indium oxide and tin oxide by washing and roasting the obtained powder (coprecipitation method) was also considered. This coprecipitation method has a good dispersion state of tin, but has a problem that the production cost increases because a neutralized waste liquid is generated as in the neutralization method. Also,
Similarly, for the purpose of improving the dispersion state of tin, electrolysis is performed using an indium-tin alloy as an anode to obtain a mixed precipitate of indium hydroxide and metastannic acid (co-electrolysis method), which is washed and roasted. A method of obtaining a mixed powder of indium oxide and tin oxide was also considered. In this co-electrolysis method, the dispersion state of tin was good and, unlike the above-mentioned co-precipitation method, an excellent result that no waste liquid was generated was obtained.

Unfortunately, ammonium nitrate used as an electrolytic solution is satisfactory in terms of cost and maintenance of purity. However, since metastannic acid, which is a non-conductor, is deposited on the electrode surface, continuous electrolysis is performed. There was a problem that it was not possible. Ammonium chloride was considered as an alternative electrolytic solution.However, although metastannic acid does not precipitate in an electrolytic solution containing chlorine, it is difficult to remove chloride ions from the obtained precipitate, and the problem of increased cost due to washing occurs. Yes, it did not lead to a fundamental solution.

[0011]

DISCLOSURE OF THE INVENTION The present invention solves the above-mentioned problems, in particular, improves the dispersibility of tin to reduce vacancies, and is suitable for forming an ITO thin film with high density and low nodule generation. An object of the present invention is to efficiently manufacture an ITO sintered body target, thereby suppressing a decrease in productivity and a decrease in quality due to generation of nodules.

[0012]

Means for Solving the Problems The present invention provides: a mixed solution in which a dispersion solution in which indium hydroxide is dispersed and a dispersion solution in which metastannic acid is dispersed are mixed;
A method for producing an ITO target, characterized in that the mixed dispersion solution is dried and then roasted, and the molded body of the oxide mixed powder thus obtained is sintered. 2 Production of indium hydroxide by an electrolytic method. 3. The method for producing an ITO target according to the above item 1) 3. The method for producing an ITO target according to the above item 1 or 2, wherein metastannic acid is produced by dissolving metallic tin in nitric acid. 5. The method for producing an ITO target according to any one of the above items 1 to 3, wherein a shape drying device is used. 5. The pH of the mixed dispersion solution is 5 or more and 9 or less. And a method of manufacturing an ITO target.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION The present inventors have studied a method of obtaining a more simple and more uniform tin dispersion state, instead of the conventional method of manufacturing by mixing an oxide powder, and as a result, have found that indium oxide has Focusing on a dispersion solution of indium hydroxide as a precursor and a dispersion solution of metastannic acid as a precursor of tin oxide, these dispersion solution stages, namely, dispersion of indium hydroxide dispersion solution (slurry) and dispersion of metastannic acid The solution (slurry) is mixed to form a mixed and dispersed solution (mixed slurry). Thereby, the dispersibility of tin is dramatically improved. Then, after drying and roasting, the oxide mixed powder obtained is molded and then sintered, whereby a sintered body without tin segregation can be obtained. Body targets can be manufactured. FIG. 1 shows a flow of a process of manufacturing an ITO sintered body by mixing the slurry of the present invention.

A dispersion solution of indium hydroxide as a raw material is prepared by dissolving metal indium in an acid (such as nitric acid).
A method of neutralizing by adding an alkali (ammonia or the like), washing the precipitated indium hydroxide and dispersing it in pure water (neutralization method), or washing the indium hydroxide generated by electrolysis using metal indium as an anode and purifying the indium hydroxide. It can be produced by a method of dispersing in water (electrolytic method). As described above, the production method is not particularly limited, but production by the electrolytic method is more advantageous in terms of cost, and is more effective because waste liquid treatment is not required. The dispersing solution of metastannic acid as a raw material is a method of dissolving metallic tin in nitric acid, washing the precipitated metastannic acid and dispersing it purely (dissolution precipitation method), or metastannic acid generated by electrolysis using metallic tin as an anode. Can be manufactured by a method of washing and dispersing in pure water (electrolytic method).

As described above, although the production method is not particularly limited, ammonium nitrate used as an electrolytic solution in a method for obtaining metastannic acid by an electrolytic method is satisfactory in terms of cost and maintenance of purity. Since metastannic acid, which is a nonconductor, precipitates on the surface, there is a problem that stable and stable electrolysis cannot be performed. Ammonium chloride can also be considered as an electrolytic solution, but metastannic acid does not precipitate in an electrolytic solution containing chlorine, but it is difficult to remove chloride ions from the obtained precipitate, and there is a problem that washing costs increase. Therefore, production by the solution precipitation method is more advantageous than the electrolytic method in terms of cost. As is clear from the above, there is no limitation on the production of indium hydroxide and metastannic acid as compared with the coprecipitation method or the coelectrolysis method performed for the purpose of improving dispersibility. In other words, on the one hand, in the production of indium hydroxide, the most efficient electrolysis method that does not cause problems such as wastewater treatment is adopted, and on the other hand, for the production of metastannic acid, the most efficient dissolution precipitation method (nitric acid dissolution) is used. Can be. This has an excellent effect that a mixed slurry having a dispersibility equivalent to that of the coprecipitation method or the like can be obtained. This is a major feature of the present invention.

The particle diameter of indium hydroxide and metastannic acid is preferably 10 μm or less. This is because uniformity and dispersibility are effectively improved. It is desirable that the pH of the slurry obtained by mixing the indium hydroxide dispersion solution and the metastannic acid dispersion solution is 5 or more and 9 or less. pH 5
If the pH is less than 1, the aggregation of metastannic acid occurs, and if the pH exceeds 9, aggregation of indium hydroxide occurs, and in any case, uniform mixing becomes difficult. In order to efficiently obtain a good dispersion state in a short time, it is desirable to mix the slurry using a homogenizer. Furthermore, if a spray-type drying apparatus is used for drying the mixed slurry, the mixed slurry can be dried in an extremely short time, and thus a dry powder can be obtained while maintaining good tin dispersibility.

A dispersion solution in which indium hydroxide is dispersed,
The solid content of the dispersion in which metastannic acid is dispersed and the solid content of the slurry in which these are mixed are desirably 10 to 80 wt%. If the content is less than 10 wt%, the amount of heat required for drying after mixing is large due to a large amount of water, which is disadvantageous in cost. On the other hand, if the content exceeds 80% by weight, the viscosity of the slurry becomes high, so that stirring and handling become difficult.

The roasting, that is, the heat treatment in an atmosphere containing oxygen is performed at a heating temperature of 700 to 1200 ° C. for a heat treatment time of 2 hours.
It is desirable to carry out in 4 hours or less. If the temperature is lower than 700 ° C., salts such as ammonium nitrate mixed from the electrolyte or the like may not sufficiently evaporate and remain. In addition, a temperature exceeding 1200 ° C. or a heat treatment time 2
This is because the roasting for more than 4 hours causes remarkable growth of crystal grains and lowers sinterability. When coarse particles are generated, it is conceivable to perform sufficient pulverization after roasting to reduce the effect, but this not only reduces the productivity but also reduces the contamination of impurities from the pulverization medium. It is not preferable because it increases. Therefore, it is better to set the above range. In particular, a heat treatment time of 5 hours or less is more preferable.

[0019]

Examples and Comparative Examples Next, examples of the present invention will be described. This embodiment is merely an example, and the present invention is not limited to this example. That is, all aspects or modifications other than the examples are included within the scope of the technical idea of the present invention.

Example In accordance with the manufacturing process shown in FIG. 1, an indium hydroxide dispersion having a solid content of 50% produced by the electrolytic method and a solid content of 40% produced by a solution precipitation method were prepared.
% Of the metastannic acid dispersion is converted to oxides and converted into In ₂ O ₃
It was mixed so that -10% SnO _2, and dried by spraying in hot air 250 ° C. This dried powder is air
The mixture was roasted at 2 ° C. for 2 hours to obtain a mixed powder of indium oxide and tin oxide. The mixed oxide powder was pulverized by a wet medium stirring mill until the average particle diameter became 1 μm in order to dissolve the aggregation by roasting, and then granulated. Further, using this granulated powder, press molding was performed at a pressure of 1 t (ton) / cm ² to obtain
A molded body of 00 × 120 × 8 (mm) was sintered at 1550 ° C. for 3 hours in an oxygen atmosphere to obtain an ITO sintered body.

(Comparative Example) A dry powder obtained by spraying an indium hydroxide dispersion liquid produced in the same manner as in the example into hot air at 250 ° C. was roasted at 900 ° C. for 2 hours, and oxidized. Indium was obtained. Similarly, a dried powder obtained by spraying a metastannic acid dispersion produced in the same manner as in the example into hot air at 250 ° C. was roasted at 900 ° C. for 2 hours to obtain a tin oxide powder. . This was mixed so as to become In ₂ O ₃ -10% SnO ₂ , pulverized by a wet medium stirring mill until the average particle diameter became 1 μm in order to dissolve the aggregation by roasting, and then granulated. Using this granulated powder, molding and sintering were performed under the same conditions as in the example to obtain an ITO sintered body. FIG. 2 shows the flow of the manufacturing process of the comparative example.

Next, using the sintered bodies obtained in the above Examples and Comparative Examples as a sputtering target, DC magnetron sputtering was performed to measure the generation amount (coverage) of nodules. The sputtering conditions are as follows. Sputtering gas: Ar + O ₂ Sputtering gas pressure: 0.5 Pa Sputtering gas flow rate: 300 SCCM Oxygen concentration: 1% Leakage magnetic flux density: 400 Gauss Input power: 0.5 W / cm ² Sputtering time: Integrated power amount 100 Whr / cm ²
Table 1 shows the measurement results of the generation amount (coverage) of the discharge nodules until the value of. As is clear from this comparison, the coverage of nodules in the comparative example was 70%, whereas the coverage of nodules in the sintered body of this example was 10%.
The remarkable effect of the present invention was confirmed.

[0023]

[Table 1]

[0024]

According to the present invention, the porosity is reduced by improving the dispersibility of tin, and an ITO sintered body target with less nodule generation suitable for forming an ITO thin film is efficiently manufactured, whereby the quality of the film is reduced and It has an excellent effect of suppressing a decrease in productivity.

[Brief description of the drawings]

FIG. 1 is a diagram showing a flow of a manufacturing process by slurry mixing of the present invention.

FIG. 2 is a diagram showing a flow of a manufacturing process of a comparative example.

FIG. 3 is a diagram showing a flow of a conventional manufacturing process.

Continuing on the front page (72) Inventor Koichi Nakajima 187-4 Usuba, Hachikawa-cho, Kitaibaraki-shi, Ibaraki F-term in Nikko Materials Isohara Plant (reference) 4G030 AA34 AA39 BA02 GA17 4K029 BA45 BA50 BC09 DC05 DC09

Claims (5)

[Claims] 1. A mixed solution in which a dispersion solution in which indium hydroxide is dispersed and a dispersion solution in which metastannic acid is dispersed are mixed to form a mixed dispersion solution. The mixed dispersion solution is dried and then roasted. A method for producing an ITO target, comprising sintering a compact of a mixture of powders. 2. The method for producing an ITO target according to claim 1, wherein the indium hydroxide is produced by an electrolytic method. 3. The IT according to claim 1, wherein the metastannic acid is produced by dissolving tin metal in nitric acid.
Manufacturing method of O target. 4. The method for producing an ITO target according to claim 1, wherein a spray-type drying apparatus is used for drying the mixed dispersion solution. 5. The method according to claim 1, wherein the pH of the mixed dispersion is from 5 to 9.
Manufacturing method of TO target.