JP2002179469A - Production process of sintered compact for target - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a production process of a sintered compact for a target with which when dried, no crack or no warpage is not caused in the green body and the dried green body shows high strength, by applying a slip casting method in formation of a large-sized green body. SOLUTION: This sintered compact production process involves casting a slurry consisting of a powdery metal oxide such as oxide of indium, tin, zinc, aluminum, gallium, cerium, germanium or silicon, or multiple oxide of plural metals selected from these metals, a binder, a dispersant and water, into a casting mold, drying the resulting green body to obtain a dried green body and sintering the dried green body, wherein: immediately after the casting, the formed green body is dried under drying conditions sufficient to provide a 3-5 mg/cm3/hr [(weight) of H2O removed)/(green body unit volume)/(unit time)] drying rate and also, an about >=70% ratio of the amount of water removed to the amount of water contained in the green body immediately after the casing, more specifically, when the drying is performed in an atmosphere of 20-60 deg.C and a 75-85% relative humidity; subsequently, the dried green body is subjected to heat treatment at 80-200 deg.C for 20 min to 1 hr; and thereafter; the heat-treated body is sintered at a desired temperature.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sputtering method for a transparent conductive film used for a solar cell or a liquid crystal display device, a high-ferroelectric film used for a protective film of a capacitor or a capacitor of a semiconductor memory, or a discharge electrode of a PDP. The present invention relates to a ceramic sintered body target used when manufacturing by a method, and more specifically, to a method for manufacturing a high-density and large-sized ceramic sintered body.

[0002]

2. Description of the Related Art Conventionally, a ceramic sintered body for a sputtering target is obtained by pulverizing and mixing a raw material powder with a ball mill or a medium stirring mill, and drying and mixing the powder with a spray drier or the like.
Granulation, mold molding and casting molding, cold isostatic pressing (C
It is often manufactured by a so-called normal pressure sintering method, which is obtained by sintering in a sintering furnace after molding by IP) or the like. As another method, there is a pressure sintering method using a hot press or the like, but the equipment cost is high, and it is not general as a method for manufacturing a large sputtering target.

In recent years, as the size of liquid crystal display elements and solar cells has increased, and the diameter of semiconductor Si wafers has increased, the size of sputtering targets used has also increased, resulting in a 700 mm square tin oxide-added indium oxide (ITO) target and gallium-added oxide. A zinc target (GZO), an aluminum-added zinc oxide target (AZO), a strontium-added barium titanate target having a diameter of 350 mm, and the like have been developed.

[0004] To produce a 800mm angle about a large target for sinter is desirable to surface pressure during molding and 500 Kg / cm ^2, Then the die pressing method 2
A 500-ton mold press is required, and the CIP method also requires a large-sized apparatus, which is not practical. Therefore, a split target in which a plurality of smaller sintered bodies are bonded has been used. However, the use of such a split target causes the following problem.

[0005] 1. Debris generated during sputtering accumulates at the joint between the sintered bodies, and the dust re-adheres to the film surface, thereby increasing the number of pinholes in the resulting film.

[0006] 2. Black foreign substances called nodules are generated on the surface of the sintered body around the joint of the sintered body, resulting in a decrease in deposition rate, a decrease in light transmittance of the obtained film, an increase in electric resistance of the obtained film, and abnormal discharge. Pinholes increase.

[0007] Since nodules also occur in low-density portions of the target, a uniform target having a high density of the sintered body is required.

Recently, by using a pressure casting method as disclosed in Japanese Patent Publication No. 6-659 and Japanese Patent Application Laid-Open No. Hei 9-88564, it has become possible to produce a larger and higher-density target than the die pressing method or the CIP method. Was. As the mold used for the casting, a mold made of gypsum or a mold made of a phenolic resin-based porous plastic as described in Japanese Patent No. 1073068 can be used.

[0009]

By the way, recently, the size of LCDs, solar cells, and the like has been increasing, and a target having a length of 1 m or more has been required. However, it has been difficult to satisfy this requirement even by using the casting method. That is, even if the casting method is applied, a molded article exceeding 50 cm × 50 cm is liable to crack or warp during drying, and is deformed or broken during handling of the molded article such as being put into a sintering furnace. . In particular, when a target thinner than the area is manufactured, the strength of the compact is reduced, and this disadvantage is particularly remarkable.

An object of the present invention is to provide a method for obtaining a sintered body for a target which does not generate cracks and warpage during drying and has a high strength of the molded body when a large molded body is obtained by applying the casting method. .

[0011]

A method for producing a sintered body for a target according to the present invention, which achieves the above object, comprises an oxide of indium, tin, zinc, aluminum, gallium, cerium, germanium, silicon, or a composite oxide thereof. In a method of manufacturing a sintered body for a target by injecting a slurry comprising a metal oxide powder such as a binder, a dispersant, and water into a casting mold and drying to obtain a molded body, and sintering the molded body, At a drying rate of ^{3 to 5} mg H ₂ O / molded body 1 cm ³ / hour, more preferably 4 to 4.5 mg H ₂ O / molded body 1 cm ³ / hour, the water content of the molded body immediately after casting is about 70.
% Or more, then heat-treated at 80 to 200 #C for 20 minutes to 1 hour, and then sintered at a desired temperature.

Another embodiment of the present invention provides indium,
Inject a slurry consisting of metal oxide powder such as tin, zinc, aluminum, gallium, cerium, germanium, silicon oxide or composite oxides of these, binder, dispersant and water into a casting mold, dry and mold In a method for producing a sintered body and sintering the molded body to produce a sintered body for a target, the drying conditions immediately after casting are adjusted to a temperature of 20 to
In an atmosphere of 60 # C and humidity of 75 to 85%, the molded body immediately after casting is dried in the atmosphere for about 70% or more of the water content, and then heat-treated at 80 to 200 # C for 20 minutes to 1 hour. Sinter at temperature.

The present invention is more effective when acrylic resin is used as a binder at the time of casting.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A large molded article can be relatively easily prepared by using a casting method. However, a molded article immediately after casting contains a large amount of water and must be dried. For drying, it is necessary to perform constant-rate drying so as not to form a distribution of moisture inside the molded body.

As a condition for this, a drying speed of 3 to 5 mgH ₂ O / 1 cm ³ / hour of molded article, more preferably 4 to 4.5 mgH ₂ O / 1 cm ³ / hour of molded article, is appropriate. If the speed is higher than 5 mgH ₂ O / cm ³ / hour, cracks and deformation occur in the molded body. 3 mgH ₂
If it is slower than O / compacted body 1 cm ³ / hour, the drying time will be long, and the moisture will be repeatedly dried and absorbed under the influence of the outside due to the opening and closing of the drying chamber, making it difficult to dry at a constant rate. Specific drying conditions for obtaining such a drying speed can be realized, for example, by setting the temperature of the drying chamber at 25 to 55 ° C. and the humidity at 75 to 85%. Immediately after casting under these conditions, approximately 70% or more of the water contained in the molded body is removed. Even if the drying speed thereafter is increased, no cracking or deformation occurs in the molded body.

The compact obtained in this way is sintered in a sintering furnace, but before that, it is subjected to handling operations such as storage until sintering and movement to the sintering furnace. A molded body with a small thickness for its area is easily deformed by such handling,
Easy to break.

In order to improve the handleability of the molded article, in the present invention, the dried molded article is 40 to 200 #
C. If moisture remains in the compact, dry completely at 60-120 # C. The effect began to be seen after about 20 minutes after this treatment, and this effect was saturated in about 2 hours. This is 2
If the time is 0 minutes or less, the temperature of the entire molded body does not rise, and the modification of the binder and the evaporation of the residual moisture are not sufficient. If it is 2 hours or more, the modification of the binder and the evaporation of the residual moisture are considered to have been completed. .

The reason for the increase in the strength of the molded article due to the heat treatment may be simply due to thermal denaturation of an organic substance as a binder and an increase in the strength due to an increase in film thickness. In the present invention, however, the strength is increased more than expected. This is considered to be due to the effect that the adhesion between the binder and the raw material particles and the adhesion between the raw material particles are increased by removing water from the surface where the binder and the raw material particles are in contact. This is supported by the fact that the strength decreases when the heat-treated molded body is placed in a humid environment again to absorb moisture.

The binder to be added to the molded product is not particularly limited, but acrylic emulsions such as Yuken Kogyo's Celander DB system, Kyoeisha Chemical Oricox KC system, Chuo Rika Chemical Industry's Rica Bond ES system, Mitsui Chemicals WA310 system, etc. These acrylic emulsions and Kuraray Povar
It is more effective to use a mixture of PVA105 or PVA117 (PVA), or a mixture of these acrylic emulsions and oligosaccharide alcohols, or sugars such as D-sorbitol or SE-20 of Niken Kagaku as the binder.

The amount of the binder to be added may be a generally employed ratio, for example, 0.5 to 4 parts by weight based on the dry raw material powder.
% By weight, particularly preferably 1-2% by weight.

The metal oxide powder which can obtain good results by applying the present invention is an oxide of indium, tin, zinc, aluminum, gallium, cerium, germanium, silicon, or a composite oxide thereof. The particle diameter of the metal oxide powder immediately before casting is preferably 0.1 μm or less. For this purpose, if necessary, the metal oxide powder is mixed with a binder or the like, and then pulverized by a wet ball mill or a medium stirring mill.

[0022]

The present invention will be described below in detail with reference to examples of the present invention. In addition, the following results can be obtained even by using GZO or AZO, and it is possible to obtain these large sintered bodies. (Example 1) Internal dimensions, 360 mm x 195 mm x 10 m
m with phenolic resin mold fixed to a large press
A production test of an O-sinter was performed.

Indium oxide powder (2260 g), tin oxide (251 g), polycarboxylic acid dispersant having a solid content of 40 wt% (85 g), acrylic emulsion binder having a solid content of 40 wt% (189 g), water (354 g) Is mixed in a high-speed medium stirring mill, mixed and pulverized to a concentration of 80.
A weight percent slurry was made. After degassing the obtained slurry under vacuum, it is poured into a casting mold, and the casting pressure is 5 kg.
/ Cm ² was cast.

After the completion of the casting, 0.2 kg is added to the casting mold.
/ Cm ² was applied to the upper mold to raise the upper mold, and the molded body was taken out of the mold.

The molded body thus obtained is placed in a thermo-hygrostat at 30 ° C./80% Rh, 30 ° C./75% Rh, 30 ° C. · 7
0% Rh, 40 ° C, 80% Rh, 60 ° C, 80% Rh, 7
Each three sheets were dried under the conditions of 0 ° C. and 80% Rh. Drying in the thermo-hygrostat was terminated when 70% of the moisture contained in the molded body had evaporated immediately after casting. Table 1 shows the results together with the drying rate (mgH ₂ O / molded article 1 cm ³ / hour). The number of cracks in the table is represented by (number of cracked compacts) / (number of dried articles).

FIGS. 1 and 2 show the change in weight during the drying process of the compact under each condition. Table 1 Drying conditions and number of cracks ─────────────────────────────────── Drying conditions 30 ℃ 30 ℃ 30 ℃ 40 ℃ 60 ℃ 70 ℃ 80% Rh 75% Rh 70% Rh 80% Rh 80% Rh 80% Rh ───────────────────────枚 数 Number of cracks generated 0/3 0/3 2/3 0/3 0/3 3/3 ────────────────── Drying rate 3.5 4.3 5.3 4.2 4.7 5.2 (mgH ₂ O / molded product 1cm ³ / hour) ────────────を The molded body without cracks is put in a thermostat at 100 # C,
Heat treatment was performed for one hour. Thereafter, the dimensions and weight were measured to calculate the density of the compact. The compact density was 49%.

After demolding the molded body at 600 ° C., it was sintered at 1550 ° C. for 25 hours to obtain an ITO sintered body. The sintered density of this sintered body is 99.3% to 99.7%
Met.

(Example 2) Cast molding was carried out in the same manner as in Example 1, and the obtained molded product was subjected to 40 ° C · 8 in a thermo-hygrostat.
Immediately after the casting, the molded body was dried under the condition of 0% Rh until 70% of the water contained in the molded body was evaporated. Nineteen molded articles were prepared in the same manner. One sheet was left at room temperature without heat treatment, and dried until the moisture content in the molded article became about 2%. Others are 40 # C, 80 # C, 100 # C in the thermostat.
Heat treatment was performed for 1 hour at each of 150 # C, 200 # C, and 250 # C. The density of these compacts was 50%.

From these compacts, 30 mm × 10 mm ×
Four 10 mm samples were each cut out and subjected to a three-point bending test. Table 2 shows the obtained results.

Table 2 熱処理 Heat treatment temperature (#C) None 40 80 100 150 200 250 ────────────────────────────────── Strength MPa 3.92 10.78 11.55 12.74 13.45 15.76 14.95 強度よ り From the results in Table 2, the heat treatment increases the strength of the compact, It is understood that the strength is saturated when the value exceeds.

Next, the molded body obtained in this example was subjected to a binder removal treatment at 600 ° C., and then sintered at 1550 ° C. for 25 hours to obtain an ITO sintered body. The sintered density of this ITO sintered body is 9
It was 9.5%.

Next, a performance test as a target was performed using the obtained ITO sintered body. A circular target having a diameter of 125 mm and a thickness of 7 mm, and a semicircular target obtained by dividing a round target into two were prepared from the ITO sintered body, and subjected to a long-term sputtering test using a sputtering apparatus CFS52-F manufactured by Shibaura Electric. Sputtering conditions were gas pressure of 0.
The sputtering was performed at 6 Pa, an oxygen partial pressure of 2%, and a sputtering current of 1.2 A.

With one circular target, the amount of nodules generated is small until the thickness of the erogen becomes about 6 mm, and the specific resistance of the obtained sputtered film is 5 × 10 ⁻⁴ Ω.
・ It was stable at about cm 2. On the other hand, in the case of a divided target in which two semicircular targets are combined and used as a circular target, if the erogen thickness of the target exceeds 3 mm, nodules are densely generated on the line of the joining portion, and the resulting sputtered film has Specific resistance is 5 × 10 ^-4 Ω
· From about cm to 8 × 10 ^-4 Ω · cm.

It is said that particles in the obtained sputtered film are related to abnormal discharge during sputtering. Therefore, the number of arcs generated during the above-mentioned sputtering test was measured using a micro arc monitor (manufactured by Landmark Technology). The results are shown in Tables 3 and 4. In the table, the large value is 50 m per arc energy.
J or more, medium is less than 50 mJ, 10 mJ or more, small is 10 mJ
It is less than. The number of occurrences is the average number of occurrences per minute.

As can be seen from the table, it can be seen that the number of occurrences of small arcs is larger in the divided target using two semicircular targets. This shows that a large target is effective in reducing abnormal discharge, which leads to a reduction in particles and pinholes.

Table 3 Integrated target {Erosion depth Large arc Medium arc Small arc} ──────────────────────────── 0 to 3mm 0 0.05 pcs / min 2.9 pcs / min ────────── ───────────────────── 3mm to 6mm 0 0.17 pcs / min 3.7 pcs / min ───────────────── ────────────── Table 4 Split target ─────────────────────────────── Erosion depth Large arc Medium arc Small arc ─────────────────────────────── 0 to 3mm 0 0.04 pcs / min 3.3 pcs / Min ────────────────────────────── ─ 3mm to 6mm 0 0.31 pieces / min 12.1 pieces / min 内 (Example 3) Dimensions, 780mm × 360mm × 10m
phenolic resin and SUS porous layer
Production of ITO sintered body by fixing to large press using mold
The test was performed. Indium oxide powder (9040 g), acid
Tin Carbide (1004g), Polycarbo with 40% by mass solid content
Acrylic acid with predetermined amount of acid-based dispersant and solid content of 40% by mass
Emulsion binder (502g) and water
The mixture is put into a high-speed medium stirring mill, mixed and pulverized to a concentration of 80.
A slurry having a mass of t% was prepared. True the resulting slurry
After the emptying method, it is poured into the casting mold created in this example,
Casting pressure 20kg / cm ^TwoWas cast. Casting
After completion of casting, 0.2kg / cm in casting mold^TwoPneumatic
And the upper mold was raised to remove the molded body from the mold.

The molded body was placed in a thermo-hygrostat at 40 ° C. and 80%
It was dried under Rh conditions. Drying in the thermo-hygrostat was terminated when 70% of the moisture contained in the molded body had evaporated immediately after casting. There was no crack in the obtained molded body. This molded body is placed in a thermostat at 100 ° C.
Heat treatment was performed for one hour.

Thereafter, the dimensions and weight were measured to calculate the density of the compact. The size of the molded body is 765mm x 353mm x
9 mm. The compact density was 49%.

After demolding the molded body at 600 ° C., it was sintered at 1550 ° C. for 25 hours to obtain an ITO molded body. The surface of this sintered body is ground to 615 mm x 280 m
An mx 7 mm target was made. The sintered density of this target was 99.5%.

[0040]

As described in detail above, according to the present invention,
After casting, it became possible to dry without generating cracks, and the strength of the molded body was increased. As a result, the molded body was not deformed or damaged in handling for producing a large-sized sintered body. Also, the use of the integrated target leads to prevention of deterioration of specific resistance in sputter deposition and prevention of abnormal discharge.

This large sintered body is extremely useful for producing a transparent conductive film using an ITO or zinc oxide based sintered body. For these reasons, the present invention is extremely valuable industrially.

[Brief description of the drawings]

FIG. 1 is a diagram showing a change in weight during a drying process of a molded body in Example 1.

FIG. 2 is a diagram showing a change in weight during a drying process of a compact in Example 1.

Claims (3)

[Claims] 1. Indium, tin, zinc, aluminum, gas
Oxides of lithium, cerium, germanium, silicon,
Or a metal oxide powder such as a composite oxide thereof,
Pours a slurry consisting of
And dried to obtain a compact, which is sintered and
In the method for producing a sintered body for get, 3 to 5 mgH
_TwoO / mold 1cm^Three/ Hour drying speed, immediately after casting
After drying about 70% or more of the water content of the molded body,
Heat treatment at ~ 200 # C for more than 20 minutes
Sintered body for target characterized by sintering at desired temperature
Manufacturing method. 2. An oxide of indium, tin, zinc, aluminum, gallium, cerium, germanium, silicon,
Alternatively, a slurry comprising a metal oxide powder such as a composite oxide thereof, a binder, a dispersant, and water is poured into a casting mold, dried to obtain a molded body, and the molded body is sintered to form a sintered body for a target. In the method of manufacturing, the drying conditions immediately after the casting are performed in an atmosphere at a temperature of 20 to 60 ° C. and a humidity of 75 to 85%, and in the atmosphere, about 70% or more of the moisture of the molded body immediately after the casting is dried. And then 80-20
A method for producing a sintered body for a target, comprising heat-treating at 0 # C for 20 minutes to 1 hour, and thereafter sintering at a desired temperature. 3. The method for producing a sintered body for a target according to claim 1, wherein the binder is an acrylic resin.