JPH05148635A - Ito sputtering target - Google Patents

Abstract

PURPOSE:To provide an ITO sintered target capable of stably forming a high- quality ITO film under good film forming operations with the abnormal discharge and nodules being hardly generated in sputtering and with gas adsorption minimized. CONSTITUTION:A powder metallurgy material consisting essentially of indium oxide and tin oxide is sintered in an oxygen atmosphere. Consequently, the surface roughness Ra of the target is adjusted to <=0.5mum, or an ITO sintered target is realized while satisfying 6.20<=D<=7.23 and -0.0676+0.887>=rho>=-0.0761D+0.666 where D is the density (g/cm<3>) and f is the bulk resistance value (mOMEGAcm).

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a target used for forming an ITO film (Indium-Tin Oxide film) by sputtering.

[0002]

2. Description of the Related Art In ₂ O ₃ and SnO ₂ oxide films, which exhibit "n-type conductive semiconductor characteristics" called "ITO film", have very high conductivity as well as visible light transmittance (transparency). Therefore, recently, liquid crystal display devices, thin film electroluminescence display devices, radiation detection elements, transparent tablets for terminal devices, heat generation films for preventing dew condensation on window glasses, antistatic films, or solar heat collection. It is used in a wide variety of applications, including selective permeation membranes for vessels. As a means for forming this ITO film, a chemical film forming method such as a spray method or a CVD method utilizing thermal decomposition of a compound, or a physical film forming method such as a vacuum vapor deposition method or a sputtering method is known. But,
Among them, the "sputtering method" has been widely adopted because of its advantage that "a film can be formed in a large area and a low resistance film can be formed with good reproducibility".

By the way, when an ITO film is formed by a sputtering method, a sputtering target made of indium oxide and tin oxide (hereinafter abbreviated as "ITO target") is used. As a get, a powder mixture of indium oxide and tin oxide, or a powder mixture obtained by adding dopant to the powder mixture is press-molded at room temperature, and the molded body is sintered at 1250 to 1650 ° C. in the atmosphere. Further, those which have been further machined have been generally used.

However, the ITO manufactured by the above method (method of performing mechanical processing after cold press air sintering)
(A) Abnormal discharge called arcing occurs during sputtering, which often impairs the stability of film forming operation. (B) During sputtering, the target surface is noisy. Prone to needles (needle-shaped protrusions), (C)
It has been pointed out that there are many "gas adsorption amounts on the target surface" associated with the leak of the sputtering device, which lowers the film quality, etc. Therefore, further excellent sputtering workability and ITO film quality are required. Inexpensive IT that can be secured
O target was strongly desired.

In recent years, of the series of steps for producing a sintered target, a method in which hot pressing is applied to the "molding step of powder raw material" (hereinafter referred to as "hot pressing method").
However, the ITO target obtained by sintering and machining by this method does not show a notable improvement in the above problems. (a) The initial cost of the equipment will increase, and it will be difficult to increase the size of the equipment. (b) Since the mold and the like will be expensive, the running cost will increase.
(c) Poor mass productivity because the time required for one operation is long,
Since new manufacturing problems such as the above occur, and these eventually affect the target price, it is difficult to say that these are industrially satisfactory means.

In view of the above, the object of the present invention is that the above-mentioned problems pointed out in the conventional materials are solved, but abnormal discharge and nodules are hardly generated during sputtering. Further, the gas adsorption was extremely small, and therefore, it was to realize an ITO sintered target capable of stably obtaining a high quality ITO film under a good film forming operation.

[0007]

Means for Solving the Problems The inventors of the present invention have conducted experiments and research from various viewpoints in order to achieve the above object, and found that "the factors that affect the characteristics of the ITO sintered target are: Although they exist in a wide variety, the influence of "surface roughness" on the abnormal discharge of the target, the generation of nodules, and the amount of gas adsorbed is extremely large, and if the surface roughness can be kept within a low range, The above-mentioned problems pointed out in the sintered target are remarkably improved. "

However, in practice, I adjusted to a fine surface roughness to the extent that the above-mentioned good characteristics are ensured.
There was a new problem that there was no technology for mass-producing TO sintered targets. That is, in the "conventional ITO sintered target" obtained by mechanical processing by being sintered by cold press air sintering or hot pressing, its surface roughness Ra (center line average defined by JIS B0601) The roughness is only in the range of “0.5 μm <Ra <10 μm” at best. However, the occurrence of abnormal discharge and nodules,
Alternatively, it is in the region where the surface roughness Ra is 0.5 μm or less that a remarkable improvement effect is recognized in terms of the amount of gas adsorbed, and it is an industry for keeping the surface roughness of the ITO sintered target within such a fine range. Technology was not established.

Therefore, the inventors of the present invention continued their research to find a means for stably producing an ITO sintered target having a fine surface roughness on an industrial scale, and as a result, obtained the following new findings. I was able to do it. a) In the production of the ITO sintered target, "sintering of the compression-molded oxide powder mixture" is carried out in an atmosphere with a high oxygen partial pressure of 1 atm or more, and this is subjected to machining according to a conventional method. And even when the cold pressing method is applied to the compression molding of the oxide powder mixture, the surface roughness Ra is 0.5 μm.
The following "ITO sintered target" can be stably obtained, and the occurrence of abnormal discharge, nodules, gas adsorption, etc. during sputtering can be suppressed as much as possible.

B) When the "ITO target" is sintered in a high oxygen partial pressure atmosphere, the density of the obtained "ITO target" exceeds about 7 g / cm ^3. Since it can be increased to (theoretical density of about 97 to 99%) (the density obtained by the conventional cold press atmospheric sintering method is 4.2 to 5.8 g / cm ³ and the theoretical density is at most 60 to
It is about 80%, and even the one obtained by the conventional hot pressing method has a density of 6.0 to 6.7 g / cm ^3, which is 83 to 93% of the theoretical density.
In addition to realizing a wide density range of "ITO sintered target", the above-mentioned characteristics desired for the "ITO sintered target" can be further improved by making the above high density product. It can be improved.

C) However, as described above, the surface roughness of the ITO sintered target and the density are deeply related to the effect of suppressing abnormal discharge, nodules, gas adsorption, etc. during sputtering. Needless to say, the bulk resistance value is also closely related, and when the density and the bulk resistance value are adjusted to a specific region, the stability of the film forming operation is further improved and the formability of the high performance ITO film is further improved. Further improve.

The present invention has been completed on the basis of the above-mentioned findings and the like. "A surface roughness Ra is adjusted to 0.5 µm or less, or in addition to this, a density D (g / cm ³ )
And bulk resistance ρ (mΩcm) is a) 6.20 ≤ D ≤ 7.23, b) -0.0676D + 0.887 ≥ ρ ≥ -0.0761D + 0.66
6, "ITO target manufactured by powder metallurgy from raw materials mainly composed of indium oxide and tin oxide", which satisfies the following two formulas at the same time, is provided, and abnormal discharge and nodule at the time of sputtering are provided. -It is possible to realize excellent film forming operation stability and film characteristics by suppressing the generation of gas and gas adsorption as much as possible. "

In the present invention, "surface roughness", "density D" and "bulk resistance ρ" of the ITO sintered target are used.
The reason why the value is limited to the above range is as follows. (A) Surface Roughness When the surface roughness Ra (center line average roughness defined by JIS B0601) exceeds 0.5 μm, it is not possible to sufficiently suppress abnormal discharge and nodules during sputtering, and also sputtering Due to the leak of the device, the amount of gas adsorbed on the surface of the target increases, and it becomes difficult to stably form a high-performance ITO film. The "ITO sintering target" having a surface roughness Ra of 0.5 μm or less was obtained by sintering the compression-molded raw material oxide powder mixture in a high oxygen partial pressure atmosphere of 1 atm or more as described above. After carrying out (sintering method in oxygen atmosphere), it can be manufactured by performing mechanical processing in a usual manner.

(B) Density D and bulk resistance value The density D of the ITO sintered target also has a considerable influence on the abnormal discharge during sputtering, the generation of nodules, and the amount of gas adsorbed on the target surface. However, it is also closely related to the film forming rate, the film forming rate stability, and the bulk resistance value, so that it is desirable to adjust appropriately. And, when the density of the target is lower than 6.20 g / cm ³ , the above-mentioned characteristics begin to be adversely affected, while the density of the ITO sintered target is increased to a region higher than 7.23 g / cm ^3. The "sintering method in an oxygen atmosphere" is also very difficult and causes a cost disadvantage. Therefore, the density of the ITO sintered target is 6.20-7.23.
It was defined as g / cm ³ .

Bulk resistance value ρ of ITO sintered target
Has a tendency to largely depend on its density D, and, for example, as shown in FIG. 1, tends to decrease sharply as the density increases. The lower the bulk resistance value, the less the occurrence of arcing during sputtering, which is preferable.
Achieving ρ <−0.0761D + 0.666 in the region of density 6.20 to 7.23 g / cm ³ is very difficult even by the “oxygen atmosphere sintering method”. On the other hand, when the bulk resistance value ρ of the ITO sintered target is in the region of ρ> -0.0676D + 0.887, abnormal discharge is often generated during sputtering, and the stability of the film forming operation is impaired. The phenomenon that the speed becomes unstable and the film forming speed decreases as the sputtering progresses becomes remarkable. Therefore, it is desirable to adjust the bulk resistance value ρ of the ITO sintered target within the range of −0.0676D + 0.887 ≧ ρ ≧ −0.0761D + 0.666. The relationship between the "density" and the "bulk resistance value" of the "ITO sintered target" according to the present invention is shown in a graph of FIG.

Further, the surface roughness, density and bulk resistance of the ITO sintered target according to the present invention are adjusted by pressing pressure when raw material powder is press-formed and atmosphere (oxygen partial pressure) during sintering. It is possible by adjusting the sintering temperature.

As described above, the ITO sintered target according to the present invention is obtained by press-molding and sintering a powder mixture containing indium oxide and tin oxide as main components as in the conventional method. When manufacturing an ITO target, the sintering is performed as "1.
Pure oxygen gas atmosphere pressurized above atmospheric pressure (absolute pressure) ",
It can be obtained by carrying out in a pressurized oxygen atmosphere such as "a mixed gas atmosphere having an O ₂ partial pressure of 1 atm or more". The reason for obtaining the product is not yet clear at present.

However, "when the sintering is carried out in an atmosphere of an inert gas such as N ₂ or Ar, the decomposition of ITO occurs, the surface roughness of the sintered body increases, and the density and performance decrease. And the fact that ITO has a property of easily dissociating oxygen when heated to a high temperature even in the atmosphere, so that the pressure of oxygen during sintering causes the ITO to be heated at a high temperature.
It is presumed that the dissociation of Al is effectively prevented, and that oxygen acts as a sintering aid to contribute to the fineness of the surface roughness, the improvement of the density, and the decrease of the bulk resistance. .. Further, the sintering temperature in the pressurized oxygen atmosphere is appropriately about 1600 to 1700 ° C. as in the case of conventional atmospheric sintering, and the sintering time is preferably 3 hours or more (sintering time Is the longer the better the result).

Next, the present invention will be described more specifically by comparing the present invention with comparative examples.

EXAMPLE First, tin oxide powder having the same particle size as indium oxide powder having an average particle size of 2 μm was uniformly mixed in a weight ratio of 90:10, and a binder for molding was added thereto, and -For Ludopress, the mold (165 ^W x 52
0 ^L ), graphite type (23
0 φ) was uniformly filled. Then, according to the following steps, "invention product 1", "invention product 2", "comparative product 3: co-
And an ITO sintered target of "Comparative product 4: Hot pressed product".

The product of the present invention 1: The raw material mixed powder filled in the mold is pressurized with a hydraulic press at a pressure of 800 kg / cm ² , and then heated to 80 ° C. to evaporate the water content in the binder to dry it. Then, sintering is performed in a pressure sintering furnace in a pure oxygen gas atmosphere of 1 atm (absolute pressure) at 1650 ° C. for 10 hours. Next, the surface of the obtained sintered body was ground with a surface grinder, and the side edges were further cut with a diamond cutter to obtain a target product. Surface roughness Ra of the obtained ITO sintered target product
Is 0.40 μm, density is 6.60 g / cm ³ , bulk resistance is 0.15 m
It was Ωcm.

Product 2 of the present invention: The raw material mixed powder filled in the mold is pressurized with a hydraulic press at a pressure of 950 kg / cm ² , and then heated to 80 ° C. to evaporate the water content in the binder and dry it. Then, sintering is performed in a pressure sintering furnace in a pure oxygen gas atmosphere of 4 atm (absolute pressure) at 1650 ° C. for 10 hours. Next, the surface of the obtained sintered body was ground with a surface grinder, and the side edges were further cut with a diamond cutter to obtain a target product. Surface roughness Ra of the obtained ITO sintered target product
Is 0.27 μm, density is 7.23 g / cm ³ , bulk resistance is 0.12 m
It was Ωcm.

Comparative product 3 (cold press air-sintered product):
The raw material mixed powder filled in the die is 950kg / c by hydraulic press.
After pressurizing with m ² pressure, this is heated to 80 ° C. to evaporate the water content in the binder to dry it, and then to 1 in the atmosphere.
Sinter at 650 ° C. for 10 hours. Next, the surface of the obtained sintered body was ground with a surface grinder, and the side edges were cut with a diamond cutter.
Then, it was cut into a target product. The surface roughness Ra of the obtained ITO sintered target product was 0.96 μm, and the density was 5.54 g /
The cm ³ and bulk resistance were 0.84 mΩcm.

Comparative product 4 (hot-pressed product): A graphite mold was filled with a raw material mixed powder which was heated to 80 ° C., dried and cooled, and in an Ar atmosphere, pressing force: 300 kg / cm ² , heating temperature: 900 ° C. , Pressurizing and heating time: Sintering was performed by hot pressing under the condition of 1 hour. Next, the surface of the obtained sintered body was ground with a surface grinder, and the side edges were diamond-cut.
Then, it was cut into a target product. The resulting ITO sintered target product has a surface roughness Ra of 0.54 μm and a density of 6.42 g /
The cm ³ and bulk resistance were 0.60 mΩcm.

Next, using these targets, an ITO film formation test was carried out under the following conditions by a batch type sputtering machine, and the film formation situation at that time was investigated. Sputter power: 1.2 W / cm ² , gas pressure: 5 × 10 ^-3 Torr, O ₂ composition: 1%. The test results are summarized in Table 1.

[0023]

The results shown in Table 1 also show that, when the "invention product" is used, a better result is obtained than when the "comparative product (cold press air-sintered product, hot press product)" is used. It is clear that a high quality ITO film can be formed under the film workability.

[0025]

[Summary of Effects] As described above, according to the present invention, it is possible to provide an inexpensive ITO sintered target having excellent sputtering performance. The excellent ITO effect can be stably formed with good workability, which is extremely useful in industry.

[Brief description of drawings]

FIG. 1 is a graph showing a change tendency of bulk resistance with respect to the density of an ITO sintered target.

FIG. 2 is a graph showing the relationship between the density and bulk resistance of the ITO sintered target according to the present invention.

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[Procedure amendment]

[Submission date] October 27, 1992

[Procedure Amendment 1]

[Document name to be amended] Statement

[Correction target item name] 0018

[Correction method] Change

[Correction content]

Product 1 of the present invention : The raw material mixed powder filled in the mold is pressurized with a hydraulic press at a pressure of 800 kg / cm ² , and then heated to 80 ° C. to evaporate the water content in the binder and dry it. Then, sintering is performed in a pressure sintering furnace in a pure oxygen gas atmosphere of 1 atm (absolute pressure) at 1650 ° C. for 10 hours. Next, the surface of the obtained sintered body was ground with a surface grinder, and the side edges were further cut with a diamond cutter to obtain a target product. Surface roughness Ra of the obtained ITO sintered target product
Is 0.40 μm, density is 6.60 g / cm ³ , bulk resistance is 0.17 m
It was Ωcm.

[Procedure Amendment 2]

[Document name to be amended] Statement

[Name of item to be corrected] 0019

[Correction method] Change

[Correction content]

Product 2 of the present invention : The raw material mixed powder filled in the mold is pressurized with a hydraulic press at a pressure of 950 kg / cm ² , and then heated to 80 ° C. to evaporate the water content in the binder and dry it. Then, it is sintered in a pressure sintering furnace in a pure oxygen gas atmosphere of 3.5 atm (absolute pressure) at 1650 ° C. for 9 hours. Next, the surface of the obtained sintered body was ground with a surface grinder, and the side edges were further cut with a diamond cutter to obtain a target product. Surface roughness Ra of the obtained ITO sintered target product
Is 0.27 μm, density is 7.23 g / cm ³ , bulk resistance is 0.12 m
It was Ωcm.

[Procedure 3]

[Document name to be amended] Statement

[Name of item to be corrected] 0023

[Correction method] Change

[Correction content]

[0023]

Claims (2)

[Claims] 1. An ITO sputtering target manufactured by powder metallurgy from raw materials containing indium oxide and tin oxide as main components, wherein the surface roughness Ra is 0.5 μm or less. Target. 2. An ITO sputtering target produced by powder metallurgy from raw materials mainly containing indium oxide and tin oxide, having a surface roughness Ra of 0.5 μm or less and a density D (g / cm). ³ ) and the bulk resistance value ρ (mΩcm) simultaneously satisfy the following two equations, an ITO sputtering target. a) 6.20 ≤ D ≤ 7.23, b) -0.0676D + 0.887 ≥ ρ ≥ -0.0761D + 0.66
6.