JP2000226254A - Production of high-density ito sintered compact and the resultant sintered compact, and ito sputter target using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain the subject industrially useful sintered compact excellent in characteristics as a sputter target by molding and then sintering ITO powder. SOLUTION: This ITO sintered compact is obtained by molding powder comprising indium, tin and oxygen and containing <=0.02 wt.% of halogen(s) followed by sintering the powder in an oxygen-contg. atmosphere >=90 wt.% in oxygen concentration and <=800 Pa in water vapor partial pressure at 1,500-1,650 deg.C for one hour or longer. The ITO sputter target is obtained by working the above ITO sintered compact.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for producing a high-density ITO sintered body.

[0002]

2. Description of the Related Art ITO (Indium-Tin-Oxi)
The de, indium oxide-tin oxide solid solution) thin film is used as a transparent electrode of a flat display material for a liquid crystal display or the like because of its high conductivity and excellent translucency. As a method of forming an ITO thin film, an ITO film is applied to a base material, or an ITO sintered body target obtained by molding and sintering an oxide raw material powder is sputtered to form an ITO film on the base material surface. And the like. The method of applying ITO powder to a substrate has high resistance,
It is not used as a practical transparent electrode, and almost all ITO films are industrially manufactured by sputtering.

[0003] In the sputtering method, a method using an In-Sn alloy as a target was initially used. However, there are difficulties in controllability and reproducibility of a film, and a method using an ITO sintered body as a target is presently used. Mainstream. However, in the conventional method of manufacturing an ITO thin film by sputtering using an ITO sintered body target, a blackening phenomenon of the ITO target surface called nodule occurs.
Since a work called cleaning, which removes the ITO target after stopping the sputtering and scrapes the nodule, is required, there is a problem that productivity is reduced. It has been found that the generation of this nodule is likely to occur with a low-density ITO target, and the use of a high-density ITO target suppresses the generation of nodules, thereby eliminating the cleaning step and improving the productivity.

[0004] Other problems of the low-density ITO target are that the resistance increases as the sputtering continues, the sputtering efficiency decreases, and dust called particles is generated in the sputtering apparatus, and the substrate for the ITO film is removed. The properties of the deposited ITO film deposited on the surface may be deteriorated,
The point of breaking the pattern of the TO film, the low resistance of the low-density ITO target, resulting in low spatter productivity, and increasing the power supply during sputtering causes abnormal discharge, making it impossible to stably sputter. It is pointed out.

For this purpose, various proposals have hitherto been made to increase the density of the ITO sintered body. For example, a hot press method or a hot isostatic press (hot isost)
Attic press (hereinafter abbreviated as HIP) method and a method of obtaining a high-density ITO sintered body by sintering under pressure. However, hot pressing and HI
In the P method, the temperature could not be raised, so that tin oxide could not be dissolved sufficiently, the resistance value of the ITO target was not reduced, and only a non-uniform ITO target could be obtained.
In addition, when the hot press method or the HIP method is used, expensive equipment is required, so that there is a problem that the price of the product increases.

In addition, ITO is used in a pressurized oxygen gas atmosphere.
A method for sintering a sintered body has been proposed (Japanese Patent Laid-Open No. 3-2).
However, in order to perform sintering in a pressurized oxygen gas atmosphere, expensive and special equipment that can withstand the pressure is required, so that there is a problem that the price of the product increases. Further, there is a problem such as safety in a high-pressure oxygen gas atmosphere. Furthermore, a method of sintering an ITO sintered body in an atmosphere of oxygen gas at normal pressure has been proposed (Japanese Patent Laid-Open No. 6-29934).
No. 4), but a high-density ITO sintered body has not been obtained. Further, a method has been proposed in which tin oxide powder having a large particle size is mixed with fine indium oxide powder (Japanese Patent Laid-Open No. Hei 6-1994).
183732) is not always sufficient to achieve high density.

[0007]

SUMMARY OF THE INVENTION The object of the present invention is to provide an IT
An object of the present invention is to provide a high-density ITO sintered body which is excellent in characteristics as a sputter target and industrially useful in a method for manufacturing an ITO sputter target in which O powder is molded and then sintered.

[0008]

Means for Solving the Problems The present inventors have conducted intensive studies in order to solve the above-mentioned problems, and as a result, the lower the partial pressure of water vapor in the sintering atmosphere of ITO, the lower the partial pressure of steam in the sintering atmosphere of ITO. It has been found that the higher the oxygen concentration, the higher the density of the final sintered body is promoted, and completed the present invention.
That is, the present invention provides a method of forming a powder of indium, tin and oxygen by sintering in an oxygen gas-containing atmosphere.
In the method for producing a sintered body, the halogen content contained in the powder composed of indium, tin and oxygen is 0.02% by weight or less, the oxygen concentration in the oxygen gas-containing atmosphere during sintering is 90% or more, The partial pressure of water vapor contained in the oxygen-containing atmosphere is 800 Pa or less, and 1500 ° C. to 1650 ° C.
A method for producing an ITO sintered body which is sintered while being held for at least one hour in the following temperature range, and I produced by the method.
An object of the present invention is to provide an ITO sputter target obtained by processing a TO sintered body.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail. As the powder comprising indium, tin, and oxygen in the present invention, the powder described in JP-A-10-72253 can be used.
Powder comprising indium, tin and oxygen, which can be produced according to the method for producing TO powder, mixed powder of indium oxide powder and tin oxide powder, mixed powder of indium-tin-oxide powder and tin oxide powder, or indium-tin- o
A mixed powder of xide powder and indium oxide powder may be used. Hereinafter, these are collectively referred to as ITO and IT
Abbreviated as O powder. These are formed into molded articles by the following method.

The content of tin oxide in the powder is 1 to 50% by weight.
And more preferably, can be arbitrarily selected to be 2 to 20% by weight. The powder preferably does not contain halogen, and the halogen content of the powder is 0.02% by weight or less. The powder is powder B
The primary particle diameter determined from the ET specific surface area is preferably set to 0.1.
It is larger than 05 μm and 1 μm or less, more preferably 0.1 μm or less.
It is preferable to use one having a size larger than 1 μm and equal to or smaller than 0.5 μm. The powder is preferably pulverized because the secondary particles may be agglomerated in some cases. The central particle size determined from the particle size distribution after crushing is preferably 1 μm or less. As the crushing method, dry ball mill crushing, wet ball mill crushing, jet mill crushing, or a combination thereof can be used. By using this preferable powder, the sintered body density is 7.10 g / c.
m ³ or more, the true density (the true density of ITO is 7.16 g /
cm ³ ) to obtain a high-density ITO sintered body that has been densified to 99% or more. Next, the powder is formed into a desired shape and further sintered to manufacture an ITO sintered body.

As a method for obtaining a compact of the powder,
Various known methods are used, for example, dry pressing and cold isostatic pressing (CIP) as dry molding methods, slip casting and tape casting as wet molding methods, and other injection molding methods and the like. No. When using the dry molding method, the powder is slurried in advance,
Then, when the granules are formed into a shape by spray drying or the like, operability at the time of molding is improved, and effects such as obtaining a more uniform molded body are obtained. At the time of molding, a dispersant for enhancing the dispersibility of the powder, a binder for imparting shape retention,
A release agent for facilitating removal from the mold, a lubricant for reducing friction between powders, and the like are added as necessary. Nonionic, cationic surfactants and the like as dispersants, polyvinyl alcohol, polyethylene glycol, polymers such as polymethyl methacrylate as binders, microwax emulsions and the like as release agents,
Glycerin and the like are preferably used as the lubricant.

The powder compact thus obtained is sintered and densified. Sintering is an operation of fixing powders by diffusion and requires a high temperature, and can be performed using a normal sintering apparatus using an electric furnace or the like. The sintering temperature is maintained in a temperature range from 1500 ° C. to 1650 ° C. for 1 hour or more, preferably 3 hours or more. Before sintering, that is, at a temperature lower than the temperature at which sintering starts, that is, at a temperature in the range of 1000 ° C. to 1300 ° C., the temperature is preferably maintained for 1 hour or more, and more preferably 3 hours or more.

In the present invention, the atmosphere during sintering includes an oxidizing atmosphere, that is, an atmosphere containing oxygen gas, air, air with an increased oxygen concentration, an oxygen atmosphere, and the like. Further, an atmosphere having an oxygen concentration of 95% or more is preferable. The oxygen gas-containing atmosphere at the time of sintering preferably does not contain water vapor, and the water vapor content is 800 Pa or less as a water vapor partial pressure, preferably 4 Pa or less.
It is preferably at most 00 Pa, more preferably at most 200 Pa. In order to reduce the water vapor content of the oxygen gas-containing atmosphere during sintering, the inside of the electric furnace is evacuated to remove residual water vapor and moisture adsorbed on the furnace wall, furnace material, heat insulating material, etc. Is preferred. Further, it is preferable to flow an oxygen gas having a small water vapor content such as an oxygen gas filled in an oxygen cylinder to reduce the amount of water vapor in the atmosphere in the electric furnace. There is also a method of reducing the amount of water vapor dissolved in a flowing gas by passing the gas through a desiccant or the like.

According to the method for producing an ITO sintered body of the present invention, a high-density ITO sintered body can be obtained. When this sintered body is used as a sputter target, nodules can be reduced, sputtering efficiency can be improved, and particles can be reduced. It can be expected to reduce the number of abnormal discharges, improve the quality of the formed ITO film, and the like.
Further, a dense and high-density ITO sintered body has excellent characteristics as an ITO sputter target and is industrially useful.

A transparent conductive film for a liquid crystal display (LCD) or the like is produced by a method of manufacturing a normal ITO target such as grinding and polishing the ITO sintered body of the present invention and bonding it to a copper backing plate with indium solder. Is obtained.

[0016]

EXAMPLES Next, the present invention will be described in more detail with reference to examples, but the present invention is not limited to these examples.

The measurement of the density of the sintered body in the present invention was performed as follows. Measurement of Density of ITO Sintered Body The bulk density of the ITO sintered body is measured in accordance with JIS Z8807-1.
It was determined by the Archimedes method (buoyancy method) according to the measurement method of 976 and JISR 2205-1992.

The true density for obtaining the relative density was 7.16 g / cm ^{3 according} to the following equation. 6. Indium oxide density
It was calculated from the following equation from 18 g / cm ³ , the density of tin oxide 6.95 g / cm ³ and the content of tin oxide 10 wt%.

Example 1 An oxide powder composed of indium, tin and oxygen and having a BET specific surface area of 3.26 m ² / g and a primary particle size of 0.26 μm determined from the BET specific surface area was crushed by a ball mill. The composition of indium, tin, and oxygen in the powder has a weight ratio [SnO ₂ / (In ₂ O ₃ + SnO ₂ )] calculated as an oxide of 1
It was adjusted to be 0%. When the powder was analyzed by X-ray fluorescence spectrometry, no chlorine peak was detected, and the chlorine content of the powder was 100 ppm (0.01% by weight) or less. After pulverizing the powder with a ball mill, the center particle diameter D50 determined by a laser diffraction method was 0.6 μm. A binder was added to the powder and spray dried to granulate. The powder was filled in a φ20 mm mold, uniaxially pressed at 100 kg / cm ^{2, and then} subjected to CIP pressing at a pressure of 3 ton / cm ² . Put the obtained molded body in an electric furnace for degreasing,
The temperature was raised to 600 ° C. to perform degreasing.

The degreased compact was placed in an electric furnace for sintering, and the air in the furnace was pulled by a vacuum pump. Oxygen gas with a purity of 99.5% or more in which the oxygen cylinder was dried was introduced into the electric furnace, and the atmosphere in the electric furnace was replaced with dry oxygen gas. After the replacement, the temperature of the electric furnace was increased while flowing dry oxygen gas at a flow rate of 500 ml / min. After the temperature was raised to 1200 ° C. at a rate of 200 ° C./hour and maintained at 1200 ° C. for 12 hours, the temperature was raised to 1600 ° C. at a rate of 200 ° C./hour.
Sintering was performed at 1600 ° C. for 10 hours to obtain an ITO sintered body. The dew point of the gas coming out of the gas outlet of the electric furnace was measured with a dew point meter in order to examine the partial pressure of water vapor of the oxygen gas in the atmosphere during sintering. The dew point was −70 ° C., and the partial pressure of water vapor in the oxygen gas in the sintering atmosphere was 0.26 Pa. The density of the obtained sintered body was 7.142 g / cm ³ and the relative density was 99.75%.
Met.

Example 2 A degreased compact obtained in the same manner as in Example 1 was placed in an electric furnace for sintering, and the air in the furnace was pulled by a vacuum pump. Dry oxygen gas in an oxygen cylinder is humidified by bubbling with water at room temperature and mixed with dry oxygen gas in an oxygen cylinder to adjust the dew point to minus 40 ° C. A gas was made. Humidified oxygen gas was introduced into the electric furnace, and the atmosphere in the electric furnace was replaced with humidified oxygen gas. After the replacement, the temperature of the electric furnace was increased while flowing the humidified oxygen gas at a flow rate of 500 ml / min. The temperature of the electric furnace was raised in the same manner as in Example 1. 1 at 1600 ° C
Sintering was performed for 0 hour to obtain an ITO sintered body. The dew point of the gas coming out of the gas outlet of the electric furnace was measured with a dew point meter in order to examine the partial pressure of water vapor of the oxygen gas in the atmosphere during sintering. The dew point is minus 40 ° C and the partial pressure of water vapor in oxygen gas in the sintering atmosphere is 1
It was 3 Pa. The density of the obtained sintered body is 7.142 g.
/ Cm ³ and the relative density was 99.75%.

Example 3 An ITO sintered body was prepared in the same manner as in Example 2 except that the flow rate of the humidified oxygen gas bubbled with water and the flow rate of the dry oxygen gas were adjusted so that the dew point was -20 ° C. Obtained.
The dew point of the gas coming out of the gas outlet of the electric furnace is −20 ° C., and the partial pressure of water vapor in the oxygen gas in the sintering atmosphere is 104 ° C.
It was Pa. The density of the obtained sintered body was 7.135 g /
The relative density was 99.65% in cm ³ .

Example 4 An ITO sintered body was prepared in the same manner as in Example 2 except that the flow rate of the humidified oxygen gas bubbled with water and the flow rate of the dry oxygen gas were adjusted so that the dew point was -15 ° C. Obtained.
The dew point of the gas coming out of the gas outlet of the electric furnace was minus 15 ° C, and the partial pressure of water vapor in the oxygen gas in the sintering atmosphere was 167.
It was Pa. The density of the obtained sintered body was 7.130 g /
The relative density was 99.58% in cm ³ .

Example 5 An ITO sintered body was prepared in the same manner as in Example 2 except that the flow rate of the humidified oxygen gas bubbled with water and the flow rate of the dry oxygen gas were adjusted so that the dew point became -10 ° C. Obtained.
The dew point of the gas coming out of the gas outlet of the electric furnace is −10 ° C., and the partial pressure of water vapor in the oxygen gas in the sintering atmosphere is 262.
It was Pa. The density of the obtained sintered body was 7.121 g /
The relative density was 99.46% in cm ³ .

Example 6 An ITO sintered body was obtained in the same manner as in Example 2, except that the flow rate of the humidified oxygen gas bubbled with water and the flow rate of the dry oxygen gas were adjusted so that the dew point was 0 ° C. Was. The dew point of the gas coming out of the gas outlet of the electric furnace was 0 ° C., and the partial pressure of water vapor in the oxygen gas in the sintering atmosphere was 608 Pa. The density of the obtained sintered body was 7.054 g / cm ³ and the relative density was 9
8.52%.

Comparative Example 1 Except that the flow rate of the humidified oxygen gas bubbled with water and the flow rate of the dry oxygen gas were adjusted so that the dew point was 10 ° C.
An ITO sintered body was obtained in the same manner as in Example 2. The dew point of the gas discharged from the gas outlet of the electric furnace was 10 ° C., and the partial pressure of water vapor in the oxygen gas in the sintering atmosphere was 1,227 Pa. The density of the obtained sintered body was 6.852 g / cm ³ and the relative density was 95.70%.

Comparative Example 2 Except that the flow rate of the humidified oxygen gas bubbled with water and the flow rate of the dry oxygen gas were adjusted so that the dew point was 15 ° C.
An ITO sintered body was obtained in the same manner as in Example 2. The dew point of the gas coming out of the gas outlet of the electric furnace was 15 ° C., and the partial pressure of water vapor in the oxygen gas in the sintering atmosphere was 1704 Pa. The density of the obtained sintered body was 6.718 g / cm ³ and the relative density was 93.82%.

Comparative Example 3 The degreased compact obtained in the same manner as in Example 1 was placed in an electric furnace for sintering, and the air in the furnace was pulled by a vacuum pump. Dry oxygen gas in the oxygen cylinder was humidified by bubbling with water at room temperature. Humidified oxygen gas was introduced into the electric furnace, and the atmosphere in the electric furnace was replaced with humidified oxygen gas. After the replacement, the temperature of the electric furnace was increased while flowing humidified oxygen gas at a flow rate of 500 ml / min. The temperature of the electric furnace was raised in the same manner as in Example 1. Sintered at 1600 ° C for 10 hours
A TO sintered body was obtained. Since the room temperature is 25 ° C. and the oxygen gas is bubbled with water, it is considered that the oxygen gas contains a saturated steam amount of 25 ° C., and the dew point of the oxygen gas in the sintering atmosphere is 25 ° C. The partial pressure is considered to be 3167 Pa. The density of the obtained sintered body is 6.130 g / c.
The relative density was 85.61% at m ³ .

Example 7 A degreased compact obtained in the same manner as in Example 1 was sintered.
And the air in the furnace was drawn by a vacuum pump. acid
Dry oxygen gas and dry nitrogen gas cylinder
Oxygen concentration becomes 95% by mixing with nitrogen gas
To produce a mixed gas of oxygen gas and nitrogen gas
Was. A mixed gas of oxygen gas and nitrogen gas is introduced into the electric furnace.
The atmosphere in the electric furnace was replaced with a mixed gas. After replacement,
While flowing the combined gas at a flow rate of 500 ml / min,
The temperature was raised. Up to 1200 ° C at 200 ° C / hour
After the temperature was raised and held at 1200 ° C. for 12 hours, the temperature was raised at a rate of 20
The temperature was raised to 1600 ° C. at 0 ° C./hour. 10 at 1600 ° C
After sintering for an hour, an ITO sintered body was obtained. Of the gas mixture during sintering
To check the partial pressure of water vapor and oxygen concentration?
Dew point and oxygen concentration
And each was measured. Dew point is minus 70 ° C, sintered
The partial pressure of water vapor in the oxygen gas in the atmosphere is 0.26 Pa,
The concentration was 95%. The density of the obtained sintered body is 7.1
24g / cm ^ThreeAnd the relative density was 99.50%.

Example 8 An ITO sintered body was obtained in the same manner as in Example 7, except that the oxygen concentration of the mixed gas was adjusted to 90%. Dew point of gas coming out of gas outlet of electric furnace is minus 70 ° C
And the partial pressure of water vapor in the oxygen gas in the sintering atmosphere is 0.26P
a, The oxygen concentration was 90%. The density of the obtained sintered body was 7.096 g / cm ³ and the relative density was 99.11%.

Comparative Example 4 An ITO sintered body was obtained in the same manner as in Example 7, except that oxygen gas and nitrogen gas were mixed so that the oxygen concentration became 50%. The dew point of the gas discharged from the gas outlet of the electric furnace was -70 ° C, the partial pressure of water vapor in the oxygen gas in the sintering atmosphere was 0.26 Pa, and the oxygen concentration was 50%. The density of the obtained sintered body was 6.924 g / cm ³ and the relative density was 96.7.
It was 0%.

Comparative Example 5 A powder having a chlorine content of 30 analyzed by X-ray fluorescence analysis was 30
Except for 0 ppm (0.03% by weight), an ITO sintered body was obtained in the same manner as in Example 1. The density of the obtained sintered body was 7.110 g / cm ³ and the relative density was 99.30%.
Met.

Comparative Example 6 The chlorine content of the powder analyzed by fluorescent X-ray analysis was 10%.
An ITO sintered body was obtained in the same manner as in Comparative Example 1 except that the amount was 00 ppm (0.1% by weight). The density of the obtained sintered body was 6.995 g / cm ³ and the relative density was 97.70%.
Met.

Comparative Example 7 The chlorine content of the powder analyzed by X-ray fluorescence analysis was 30%.
0 ppm (0.03% by weight).
An ITO sintered body was obtained in the same manner as in Example 1 except that the holding at 0 ° C. for 12 hours was not performed. The density of the obtained sintered body was 6.981 g / cm ³ and the relative density was 97.50%.

Comparative Example 8 The chlorine content of the powder analyzed by X-ray fluorescence analysis was 10%.
An ITO sintered body was obtained in the same manner as in Comparative Example 7, except that the amount was 00 ppm (0.1% by weight). The density of the obtained sintered body was 6.745 g / cm ³ and the relative density was 94.20%.
Met.

The above results are shown in Tables 1, 2 and 3 below.
Put together.

[0037]

Table 1 Dew point (° C.) Steam partial pressure (Pa) Sintered body density (g / cm ³ ) Relative density (%) Example 1-70 0.26 7.142 99.75 Example 2 -40 13 7 .142 99.75 Example 3 -20 104 7.135 99.65 Example 4 -15 167 7.130 99.58 Example 5 -10 262 7.121 99.46 Example 6 0 608 7.054 98 .52 Comparative Example 1 +10 1227 6.852 95.70 Comparative Example 2 +15 1704 6.718 93.82 Comparative Example 3 +25 3167 6.130 85.61

[0038]

Table 2 Dew point (° C) Oxygen concentration Sintered body density (g / cm ³ ) Relative density (%) Example 1-70 99.5% or more 7.142 99.75 Example 7-70 95% 124 99.50 Example 8 -70 90% 7.096 99.11 Comparative Example 4 -70 50% 6.924 96.70

[0039]

Table 3 Chlorine content Maintained at 1200 ° C Sintered body density (g / cm ³ ) Relative density (%) Example 1 0.01% or less 12 hours 7.142 99.75 Comparative example 5 0.03% 12 hours 7.110 99.30 Comparative Example 6 0.10% 12 hours 6.995 97.70 Comparative Example 7 0.03% None 6.981 97.50 Comparative Example 8 0.10% None 6.745 94.20

[0040]

According to the present invention, ITO powder, mixed powder of indium oxide powder and tin oxide powder, mixed powder of ITO powder and tin oxide powder, or mixed powder of ITO powder and indium oxide powder, etc. By sintering the compact obtained by molding the powder of the form, a dense ITO sintered body having a high sintering density can be easily obtained. The high-density ITO sintered body thus obtained has excellent characteristics as an ITO sputter target and is industrially useful.

Claims (9)

[Claims] 1. A method for producing an ITO sintered body, comprising forming a powder comprising indium, tin and oxygen and sintering the powder in an atmosphere containing oxygen gas, wherein the halogen content contained in the powder comprising indium, tin and oxygen is reduced. 0.02% by weight or less, the oxygen concentration in the oxygen gas-containing atmosphere during sintering is 90% or more, and the partial pressure of water vapor contained in the oxygen gas-containing atmosphere during sintering is 80% or less.
A method for producing an ITO sintered body, wherein the sintered body is held at a temperature of 1500 ° C. or more and 1650 ° C. or less for 1 hour or more. 2. The method according to claim 1, wherein the partial pressure of steam is 400 Pa or less. 3. The method according to claim 1, wherein the partial pressure of steam is 200 Pa or less. 4. The method according to claim 1, wherein the oxygen concentration in the oxygen gas-containing atmosphere during sintering is 95% or more. 5. BE of a powder comprising indium, tin and oxygen
The production method according to claim 1, wherein the T diameter is more than 0.05 µm and 1 µm or less, and the 50% diameter of the cumulative particle size distribution is 1 µm or less. 6. Oxidation comprising indium, tin and oxygen by firing a hydroxide powder comprising indium, tin, oxygen and hydrogen in a hydrogen halide gas or an atmosphere gas containing at least 1% by volume of halogen gas. The production method according to claim 1, wherein a product powder is produced, and the powder is molded and sintered. 7. The method according to claim 1, wherein the sintering is performed at a temperature in a range of 1000 ° C. to 1300 ° C. for 1 hour or more. 8. I prepared by the method according to claim 1.
TO sintered body. 9. An I prepared by the method according to claim 1.
An ITO sputter target obtained by processing a TO sintered body.