JPH05341279A - Quartz glass target - Google Patents

Abstract

PURPOSE:To provide the quartz glass target which can be formed thick in parts liable to be consumed by sputtering by using nearly net-shaped quartz glass to prevent the degradation in the yield of the material, has a high density, purity and viscosity, foams less, has a smooth surface, eliminates the need for polishing, has the characteristic of a low concn. of alkaline metal impurities so as to enhance the purity and is adequate for the insulating film of ELs and liquid crystals. CONSTITUTION:This quartz glass target is constituted by forming the slurry of synthetic silica powder having 0.5 to 20mum grain size distribution and forming the parts to be within the erosion area at the time of sputtering with a porous plate casting mold as thick parts 2. The concn. of the alkaline impurities of the target is <=0.5ppm, the total impurity content is <=5ppm, the occupying area of the foam is <=0.5mm<2>/100cm<3> and the surface roughness Rmax right after sintering is <=5mum.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a silica glass sputtering target (hereinafter referred to as a target) used when forming an insulating film used in an EL display, a liquid crystal display, a touch panel, etc. by a sputtering method.
Regarding

[0002]

2. Description of the Related Art Conventionally, a flat target made of quartz glass has been used as a material for forming a transparent insulating film on an EL substrate or a liquid crystal substrate.

The transparent quartz glass used for this purpose is conventionally known as natural quartz glass which melts quartz powder with an oxyhydrogen flame or synthetic quartz glass which hydrolyzes silicon tetrachloride with an oxyhydrogen flame. In order to obtain the size, the quartz glass block has been manufactured by cutting, grinding and polishing.

[0004]

However, a high frequency sputtering method is usually used for sputtering an oxide target of a non-conductive material, but since the sputtering is performed while controlling the plasma by a magnet, in this case, the conventional method is used. In the case of a flat-plate type silica glass target, the shape of the magnet is eroded, that is, a portion having a high horizontal magnetic flux is preferentially consumed, and the sputtering rate is gradually lowered, and the target use efficiency is 20 to 40%. There was a problem that it became low.

In order to avoid this, a method has been proposed in which the portion that is likely to be consumed in advance is made thick. However, the conventional method of making irregularities on the surface by machining such as cutting and grinding a block of quartz glass in which quartz powder or silicon tetrachloride is melted with oxyhydrogen lowers the material yield and complicates the work. Have a problem.

Further, if the surface of the target is not smooth, particles will be generated due to abnormal sputtering, so polishing is required in the machining, but there is a defect that the work is complicated and the yield is deteriorated.

The conventional transparent quartz glass has the following problems when it is used for a target. (1) When the density is low, particles are generated in the generated film due to the contained gas and impurities. (2) Since bubbles are present even though they are minute, they cause damage to the target during sputtering. (3) When natural quartz glass is used, there are many impurities,
The characteristics of the formed film deteriorate. (4) When synthetic quartz glass is used, it has a low viscosity and is liable to crack due to an increase in the target temperature during sputtering.

The present invention uses a near-net-shape synthetic quartz glass in which the yield of materials does not decrease, makes it possible to make the portion that is easily consumed by sputtering thick, has a high density, purity and viscosity, and has no bubbles. Less
An object of the present invention is to provide a quartz glass target which has a smooth surface and does not require polishing work, and has excellent utilization efficiency as a target material, and a method for producing the same.

[0009]

Therefore, the present inventors have
As a result of repeated intensive studies to solve the above problems, a high-purity synthetic silica powder having a uniform particle size was slurried using a solvent and a dispersant, and erosion during sputtering was performed using a porous plate casting mold. A finding that the above object can be achieved by obtaining a molded body with a thickened area, drying and sintering the obtained molded body to obtain quartz glass, and densifying the obtained transparent quartz glass Thus, the present invention was completed.

The feature of the present invention is that a slurry of high-purity synthetic silica powder is poured into a porous plate mold, and is dried and sintered, so that the erosion area at the time of sputtering is made thick and a smooth surface is obtained. To obtain a quartz glass target with.

The shape of the obtained product is not particularly limited as long as it has a thick erosion area during sputtering.

The particle size distribution of the synthetic silica powder used in the present invention is preferably 0.5 μm to 20 μm, particularly preferably 1 μm to 10 μm. If the particle size is less than 0.5 μm,
If it is difficult to mold due to the generation of fine bubbles, and if it exceeds 20 μm,
The density is low, which is not preferable.

As ELs and liquid crystals have become more sophisticated, the target which is a material is required to have a higher purity. In particular, the alkali metal which is a raw material for disconnection of wiring is disliked, and the purity of the synthetic silica powder depends on the alkali metal impurities. 0.1 ppm or less, the total amount of impurities is 5 ppm or less, and preferably the total amount of impurities is 1 ppm or less. If the total amount of impurities exceeds 5 ppm, the characteristics of the insulating film formed by sputtering deteriorate, which is not preferable.

The slurry is obtained by mixing the synthetic silica powder with a solvent such as distilled water and a dispersant (organic solvent such as alcohol, ketone and amide) in a rotary ball mill or the like. At this time, it is preferable to perform sufficient defoaming.

[0015] To obtain a high density of quartz glass, it is necessary to the absence of bubbles even a minute in the glass, the total bubble diameter therein, the presence 0.5 mm ^2/100 cm ³ or more, Patekuru It is a cause of generation and causes the target to crack when sputtering at high output.

[0016] The sum of bubble diameter to the 0.5 mm ^2/100 cm ³ or less, when forming the synthetic silica powder, it is essential not to leave gas or impurities that cause bubbles therein, the Therefore, by using a porous plate mold, sufficient deaeration and dehydration during molding are performed.

As the mold, various synthetic resins such as polyethylene, polypropylene, polystyrene, fluororesin, phenol resin, epoxy resin, silicone rubber, polyurethane or synthetic rubber, and water absorbing materials such as gypsum are generally used. However, it is essential that impurities are not mixed in from the mold and that the permeability is good, and a high-purity resin sintered body, a quartz sintered body, or a porous plate mold whose inner wall surface is coated with quartz cloth is used. Preferably.

The porous plate mold has such a shape that a molded body having a thick erosion area at the time of sputtering of the obtained target can be obtained. At this time, it is preferable that the shape of the molded body is such that 80% or more of the weight of the target exists in the erosion area during sputtering in order to further improve the use efficiency of the target.

In order to obtain high-purity quartz glass, the raw material synthetic silica powder must be of high purity, and it is necessary to avoid contamination during manufacturing. Therefore, the molded product is dried and sintered. The atmosphere also needs high cleanliness of class 1000, preferably class 100, in order to prevent contamination from the outside.

To increase the density, the slurry should have a density of 0.
It is carried out by pressure casting in which the pressure is 5 kg / cm ² or more, preferably 2.0 kg / cm ² or more and is injected into the mold.

After that, deaeration and dehydration are performed at a low temperature to obtain 8
Dry for 1-2 hours at 00-1000 ° C, then 15
Sintering at 00 ° C. gives a quartz glass target.

Further, during sputtering, the temperature of the target surface rises, and the target may be damaged due to the temperature difference between the back surface and the cooling surface. Therefore, it is necessary that the viscosity of the quartz glass at 1200 ° C. is 3.16 × 10 ¹² poise or more, preferably 4 × 10 ¹² poise or more.

In order to prevent the contamination of the film, it is necessary that the surface of the target is smooth, and normally, the polishing is performed by machining with SiC or Al ₂ O ₃ having an abrasive grain size of # 500. ..

On the other hand, according to the present invention, since the molding is performed with a mold which does not contaminate, the mixing of impurities can be made extremely small. Also, since it is dried and sintered in a clean atmosphere, it does not impair purity, it has high density, few bubbles, and
Quartz glass with a smooth surface can be manufactured.

【effect】

The quartz glass obtained according to the present invention has the same purity as synthetic quartz glass widely used for targets and has less bubbles as much as natural quartz glass.
Conventionally, sputter characteristics that cannot be reached at all can be expected, and since the density is similar to that of natural transparent quartz glass, it has high mechanical strength.

Further, since the high temperature viscosity is high, it has heat resistance similar to that of the natural transparent quartz glass. Therefore, the transparent quartz glass target according to the present invention is an optimum target for sophisticated EL and liquid crystal substrates.

[0027]

EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples, but the present invention is not limited thereto.

Example 1 As a raw material, a synthetic silica powder having a particle size distribution adjusted to 1 μm to 10 μm and having an analysis value shown in Table 1 was used. The synthetic silica powder was distilled water as a solvent, alcohol as a dispersant, etc. The organic solvent of was used to mix by a rotary ball mill to obtain a slurry having a concentration of 20% by weight, and sufficient defoaming was performed.

[Table 1]

The obtained slurry is 90 mm in diameter so that the erosion area during sputtering becomes thick.
1 and 2 by molding with a porous plate mold having a wall thickness of 8.4 mm and a wall thickness of 3.6 mm, and then removing the solvent and dispersant.
A molded body shown in was obtained. 3.0k slurry for molding
The density of the obtained target was increased by performing pressure casting in which the pressure was applied to the mold with g / cm ² pressure.

The obtained molded body was placed in a Draft at room temperature,
Then, deaeration and dehydration are carried out at a temperature of 300 ° C.
It was dried at 1000 ° C. for 1 to 2 hours and further sintered at 1500 ° C. to obtain a quartz glass target having a diameter of 75 mm, a thick portion 7 mm, and a thick portion 3 mm.

When the roughness of the surface of the obtained quartz glass target was measured, Ra was 0.4 μm and Rmax was 4.2 μm, and it was the same as the surface finished by baking after polishing with SiC having an abrasive grain size of # 500. there were.

The apparent specific gravity of this quartz glass target was 2.202, compared with 2.203 for conventional natural quartz glass and 2.201 for synthetic quartz glass.
Moreover, no bubbles were observed by visual observation.

The spectral transmittance of this glass was measured with a spectrophotometer.
It was confirmed that light of ˜5000 nm was well transmitted.
Results are shown in FIG.

The analytical values of the alkali metal of the glass obtained at this time were 0.3 ppm of sodium, 0.1 ppm of potassium and lithium were not detected. The other analytical values are shown in Table 2.

Further, the bubble diameter distribution measurement and the high temperature viscosity measurement were performed. The results are shown in Table 3.

Comparative Example A conventional block of quartz glass obtained by melting crystal powder with an oxyhydrogen flame was cut and machined for grinding, and the surface had an abrasive powder diameter of # 5.
After polishing with SiC No. 00, it was baked and finished to form a quartz glass target having a planar shape. Table 2 shows the analysis values of the obtained target, Table 3 shows the bubble diameter distribution measurement, and Table 3 shows the high temperature viscosity measurement results.
Shown in.

[Table 2]

[Table 3]

A sputtering test was conducted on the obtained target, and as a result, the target utilization efficiency was found to be the same as in Example 1.
Most of the targets described were subjected to sputtering, which was about 60%, and the usage efficiency was half that of 30%.

From the above results, according to the present invention, it is possible to obtain a quartz glass which has the same density and viscosity as the natural quartz glass and the purity which is the same as that of the synthetic quartz glass and has a small amount of bubbles. It is clear that a quartz glass target with high target usage efficiency can be obtained without doing so.

[Brief description of the figure]

FIG. 1 is a front view of a molded body.

FIG. 2 is a sectional view taken along line AA of the molded body.

FIG. 3 Transmittance of Example

[Explanation of symbols]

 1 Molded Body 2 Thick Part 3 Thick Part A Example

Claims (10)

[Claims] 1. A quartz glass target obtained by making a synthetic silica powder having a particle size distribution of 0.5 to 20 μm into a slurry, and using a porous plate mold to thicken a portion to be an erosion area at the time of sputtering. 2. The quartz glass target according to claim 1, which has a density of 2.20 g / cm ³ or more. 3. The quartz glass target according to claim 1, wherein the alkali metal impurities are 0.5 ppm or less. 4. The quartz glass target according to claim 1, wherein the total amount of impurities is 5 ppm or less. 5. The area occupied by bubbles is 0.5 mm ² / 100c.
The quartz glass target according to claim 1, wherein the quartz glass target is m ³ or less. 6. The quartz glass target according to claim 1, which has a viscosity at 1200 ° C. of 4 × 10 ¹² poise or more. 7. The surface roughness Ra immediately after sintering is 0.5 μm.
The quartz glass target according to claim 1, wherein: 8. The quartz glass target according to claim 1, wherein the surface roughness Rmax immediately after sintering is 5 μm or less. 9. A synthetic silica powder having a particle size distribution of 0.5 to 20 μm is slurried, and a mold using a porous plate is used,
A method for producing a quartz glass target, comprising: forming a molded body having a thick portion in an erosion area during sputtering, and drying and sintering the obtained molded body. 10. Molding in which a highly pure synthetic silica powder having a particle size distribution of 0.5 to 20 μm is slurried and 80% or more of the weight is present in the erosion area during sputtering by using a mold using a porous plate. A method for producing a quartz glass target, comprising obtaining a body, drying and sintering the obtained formed body to obtain quartz glass, and densifying the obtained transparent quartz glass.