JP2005163095A - METHOD OF PRODUCING SINTERED COMPACT, GaSb BASED ALLOY SPUTTERING TARGET, AND METHOD OF PRODUCING THE SAME - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of producing a sintered compact by which the occurrence of defects such as chipping in the edge parts of a sintered compact can be prevented, and to provide a sputtering target which attains the sintered density of ≥85% in a Ga-Sb based sintered compact and is suitable for the formation of a phase transition optical disk recording film adaptible to a high speed operation. <P>SOLUTION: The sintered compact is obtained by a stage where raw material powder is filled into a rubber mold with a prescribed shape, and is thereafter subjected to hot hydrostatic press under the pressure of ≥0.5 ton to obtain a green compact, and a stage where the green compact is sintered by a hot press. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a method for producing a sintered body. The present invention also relates to a GaSb-based alloy sputtering target used for forming a recording film of a phase change optical disk and a method for manufacturing the same.

  Currently, functional thin films produced by sputtering are widely used in various fields such as display elements, semiconductor elements, and recording media. A sputtering method uses a sputtering target (hereinafter simply referred to as a “target”) to release a predetermined substance from the target by plasma generated in a rare gas and deposit it on a substrate to form a thin film. To form.

  Since a wide variety of materials are used as the thin film, a target of a wide variety of materials is required, and various methods are employed in the target manufacturing method accordingly. In the case of a brittle material or a material whose raw material is a powder, the powder metallurgy method is most widely used for target production. The powder metallurgy includes an isostatic pressing + atmospheric pressure sintering method, a hot isostatic pressing method (HIP method), a hot pressing method, and the like, and the hot pressing method is an effective method for target production.

  The hot press method is a method in which raw material powder is filled into a cylindrical or cylindrical mold having a rectangular cross section, and the raw material powder is sintered by heating the mold and simultaneously applying pressure from above and below. Since heat and pressure are simultaneously applied, a sintered body having a high relative density can be obtained at a relatively low temperature.

  In addition, compared to the hot isostatic press method (HIP method), which is a sintering method in which heat and pressure are applied simultaneously, the hot press method can obtain a sintered body close to the product shape. The yield is relatively high. Therefore, it is suitable for manufacturing a small variety of products using a relatively expensive raw material such as a target.

  However, in the hot press method, chipping is likely to occur at the end of the obtained sintered body, and therefore it is difficult to sufficiently improve the product yield. In addition, there is a problem that the relative density cannot be sufficiently increased depending on the material.

  On the other hand, various phase change optical disks such as CD-RW, DVD-RW, DVD-RAM, and DVD + RW are used as media for recording computer information, video information, or music information. These optical disks are manufactured by sequentially forming a protective film, a recording film, a protective film, a reflective film, and the like on a plastic substrate by a sputtering method. Of these, the recording film takes two states, a crystal structure and an amorphous structure, by controlling the laser heating, and records digital information using the fact that the reflectance in each state is different. AgInSbTe-based alloys and GeSbTe-based alloys have been used as materials.

  Due to an increase in the amount of information processing, there is a strong demand for higher capacity and higher speed for optical discs. In order to increase the speed, it is important to select a recording film material in addition to improving the disc structure. Conventionally, it has been possible to increase the speed by optimizing the composition of the AgInSbTe-based alloy or GeSbTe-based alloy, but it is also approaching the limit. Therefore, a new alloy system suitable for higher speed is desired.

  The 12 atomic% Ga-88 atomic% Sb eutectic alloy has a high rate of change from an amorphous structure to a crystalline structure, that is, a so-called crystallization speed, and is expected as a high-speed recording film material that can replace AgInSbTe alloys and GeSbTe alloys. (For example, see H. Tashiro, et al., “Characterization of GaSb Phase-Change Material for High-Speed Rewritable Media”, pp11-15, Proceedings of The 14th Symposium on Phase Change Optical Information Storage (2002)) .

The sputtering target for recording film is generally manufactured by sintering material alloy powder obtained through melting and casting by means such as the above hot press. However, a GaSb-based alloy based on a 12 atomic% Ga-88 atomic% Sb eutectic alloy is expressed as a sintered density (relative density of the sintered body with respect to the true density of the alloy) even if manufactured by a conventional method. ) Has increased only to about 80%, causing problems such as abnormal discharge during sputtering, and the production efficiency of phase change optical disks not increasing.
H. Tashiro, et al., "Characterization of GaSb Phase-Change Material for High-Speed Rewritable Media", pp11-15, Proceedings of The 14th Symposium on Phase Change Optical Information Storage (2002)

  It is an object of the present invention to prevent defects such as chipping at the end of the obtained sintered body from occurring in the method for producing a sintered body. Further, the present invention provides a sputtering target suitable for forming a phase change optical disk recording film that achieves a sintering density of 85% or more in a GaSb-based alloy sintered body and supports high speed.

  The method for producing a sintered body according to the present invention includes a step of obtaining a green compact by filling a raw material powder into a rubber mold having a predetermined shape and then subjecting the raw material powder to a hydrostatic press at a pressure of 0.5 tons or more. And a step of sintering the green compact by hot pressing. Thereby, defects, such as a chip | tip in the edge part of a sintered compact, can be prevented.

  The method for producing a sintered body according to the present invention is also effective in improving the sintered density of the sintered body, and is particularly useful when the production method is applied to the production of a sputtering target of GaSb-based alloy powder. . That is, as a result, the relative density of the GaSb-based alloy target can be 85% or more.

  In addition, when the GaSb-based alloy contains 1 atomic% or more and less than 50 atomic% of Ga, and the balance is composed of Sb and inevitable impurities, the application of the manufacturing method of the present invention is optimal.

  In addition, when the GaSb-based alloy is an alloy based on a GaSb alloy containing Ga of 1 atomic% or more and less than 50 atomic% to which an additive element is added, and the solidus temperature is 589 ° C. or lower. The application of the production method of the present invention is optimal.

  According to the present invention, it is possible to prevent the occurrence of chipping at the end of a sintered body that frequently occurs in the hot press method, and it is possible to efficiently produce a sintered body particularly suitable for a sputtering target.

  In addition, by using the present invention for the production of a GaSb alloy target for a recording film, a GaSb alloy target having a high sintered density can be provided, thereby further increasing the speed of the phase change optical disk.

   As a result of various studies on the problem that the end portion of the sintered body obtained by the hot press method is often chipped, the inventors have found that the cause of the chipping at the end portion of the sintered body is the mold of the hot press. The knowledge that it was in the filling of the raw material powder to the was obtained. And it discovered that this problem could be solved by introducing isostatic pressing using a rubber mold as a pretreatment of the sintering process by hot pressing.

  In a normal hot press method, raw material powder is directly put into a mold. In this case, the packing density of the raw material powder in the mold is inevitably difficult to be uniform, and in particular, the density at the end of the mold tends to be insufficient. For this reason, it is considered that chipping is likely to occur at the end of the sintered body during cooling after sintering or when the sintered body is taken out of the mold.

  As a pretreatment for the sintering process by hot pressing, isostatic pressing using a rubber mold as shown in FIG. 1 is introduced. This is considered to be because the generation of chipping at the end of the sintered body can be prevented because isotropic force is applied by isostatic pressing, thereby eliminating the nonuniformity of the packing density of the raw material powder. .

  As shown in FIG. 1, the rubber mold includes a lower rubber plate (1) and an upper rubber plate (2). The lower rubber plate (1) is provided with a cylindrical rubber (3), and the cylindrical rubber (3 ) Is filled with the raw material powder (4). The upper rubber plate (2) is provided with a kerf corresponding to the shape of the cylindrical rubber (3). At the time of production, after the raw material powder is filled in the cylindrical rubber, the upper rubber plate (2) is covered with the cylindrical rubber (3) fitted into the kerf as shown by the arrow in FIG. The upper rubber plate (2) and the lower rubber plate (1) are aligned. Thereby, raw material powder is shape | molded by plate shape.

  The shape of the rubber mold is arbitrary depending on the shape of the desired sintered body, and a cylindrical shape can be adopted in addition to the rectangular parallelepiped shape shown in FIG.

  The pressure of the hydrostatic press is preferably 0.5 tons or more. This is because the raw material powder is not sufficiently filled when the pressure is less than 0.5 tons. Although there is no upper limit to the pressure of the hydrostatic press, the effect of the present invention can be obtained as long as it is within the generally possible hydrostatic press pressure range and the pressure is 0.5 ton or more.

  In the case of normal isostatic pressing, the raw material powder is first preformed with a mold and then inserted into a rubber mold. In the present invention, there is no need for preforming with a mold.

  When the present invention is used, in addition to the effect of preventing chipping at the end of the sintered body, the effect of improving the productivity at the time of manufacturing the sintered body by the hot press method is also obtained. That is, since the packing density is increased compared to the case of directly feeding raw material powder, the number of sintered bodies that can be sintered at one time is increased, and the raw material is fed using a compact that is easy to handle. Since the raw material can be charged in a short time during the sintering process, productivity can be improved as compared with the conventional hot press method.

  In the method of the present invention, the raw material powder to be used is not particularly limited. However, when manufacturing a brittle material (for example, a TbFe-based intermetallic compound or a semi-metallic material such as Sb or Ge) that easily causes chipping at the end. Great effect.

  The green compact molded with a rubber mold is inserted into a mold installed in a hot press apparatus after external processing is applied as necessary. Hot press conditions may be those generally used. In addition, a sintered body obtained by hot pressing can be used for production of a target by applying a generally used method as it is.

  On the other hand, the inventors of the present invention have made various studies on the formation of a recording film using a GaSb-based alloy, such as inconveniences such as abnormal discharge during sputtering, and the production efficiency of a phase change optical disk not increasing. As a result, it has been found that the above problem can be prevented in the formation of a GaSb-based alloy recording film by setting the sintering density of the target to 85% or more. In addition, by introducing isostatic pressing using a rubber mold as a pretreatment for the sintering process by hot pressing, it is possible to produce a GaSb-based alloy target having a sintered density of 85% or more without occurrence of chipping. I found it possible.

  In the present invention, the sintered density (in this case, the relative density of the sintered body with respect to the true density of the GaSb alloy) is set to 85% or more. If the sintered density is less than 85%, frequent abnormal discharges occur due to low density. This is because problems such as low productivity occur.

  The present invention is effective in various GaSb-based alloys based on a 12 atom% Ga-88 atom% Sb eutectic alloy. Specifically, among the binary alloys containing Ga of 1 atomic% or more and less than 50 atomic% with the balance being Sb and inevitable impurities, and the multi-element alloys in which various additive elements are added to the GaSb alloy, the solidus line This is particularly effective when the alloy has a temperature lower than 589 ° C. This is because if the solidus temperature is lowered, it is necessary to further lower the hot press temperature. Note that 589 ° C. is the eutectic temperature of the GaSb binary alloy.

  By introducing isostatic pressing using a rubber mold as a pretreatment for the sintering process by hot pressing, a high-density sintered body can be obtained because the packing density of the raw material powder is increased by isostatic pressing. This is probably because of this.

  Also in this case, the pressure of the hydrostatic press is set to 0.5 ton or more because the increase in density becomes insufficient when the pressure is less than 0.5 ton. When the purpose is to improve the sintered density, the raw material powder used in the present invention is not particularly limited, but it is preferable to use a pulverized powder having an average particle size of 100 μm or less. The press body molded with a rubber mold is inserted into a mold in a hot press apparatus after external processing is applied as necessary.

The hot press conditions may be those generally used, but the hot press temperature is higher than the “solidus temperature −50 ° C.” of the alloy and lower than the “solidus temperature”, and the hot press pressure is 250 kg / cm ² or higher. Is preferred. The sintered body obtained by hot pressing is used as a target after external processing and bonding to a backing plate. For outline processing and bonding, generally used methods can be applied as they are.

(Example 1)
Fe-23.5 atomic% -7.0 atomic% Co-3.0 atomic% Cr alloy powder obtained by the reduction diffusion method was prepared as a raw material powder. After the raw material powder was packed into a cylindrical rubber mold, it was inserted into a hydrostatic press while being sealed with a plastic bag, and a green compact was produced by applying hydrostatic pressure to 0.5 tons or 2 tons. The obtained green compact was adjusted in size by shaving the outer periphery, and then inserted into a graphite mold installed in a hot press apparatus.

In a vacuum atmosphere, a temperature of 1000 ° C. and a pressure of 300 kg / cm ² were loaded for 2 hours, and hot pressing was performed. The obtained sintered body was 129 mm in diameter and 13 mm in thickness, and the density of the sintered body was 8.1 g / cm ³ and 8.3 g / cm ³ , respectively.

  Under the same conditions, a total of 10 hot presses of 5 sheets were carried out, but in all cases, sintered bodies free from cracks and chips were obtained.

(Comparative Example 1)
The same raw material powder as in Example 1 was directly filled into a graphite mold and hot pressed under the same conditions. A sintered body having the same shape was obtained, but the sintered density was 7.9 g / cm ³ . A total of 10 hot presses were carried out under the same conditions, but chipping occurred at the edge of two of them, and they could not be used as targets.

(Example 2)
99.99% pure ITO powder (In ₂ O ₃ -10 mass% SnO ₂ powder) was prepared as a raw material powder. After the raw material powder was packed in a plate-shaped rubber mold, it was inserted into a hydrostatic press while being sealed with a plastic bag, and a hydrostatic pressure was applied up to 2 tons to produce a green compact. Five green compacts produced in the same procedure were inserted into a graphite mold installed in a hot press apparatus.

In a vacuum atmosphere, a temperature of 1000 ° C. and a pressure of 250 kg / cm ² were loaded for 2 hours, and hot pressing was performed. A total of 15 hot presses were carried out under the same conditions, but in all 15 sheets, a 128 mm × 255 mm × 9 mm sintered body free from cracks and chips was obtained. The density was 7.1 g / cm ³ .

(Comparative Example 2)
The same raw material powder as in Example 2 was directly filled into a graphite mold. Hot pressing was performed under the same conditions as in Example 2. A sintered body having the same shape was obtained, but only three sintered bodies were obtained by one hot press. In this way, a total of 15 hot presses were performed, but chipping occurred at the end of two of them, and could not be used as a target. The density of the sintered body was 6.9 g / cm ³ .

(Examples 3-8, Comparative Examples 3-6)
As Examples 3 to 8, a raw material powder was obtained by producing an ingot by melting in an argon atmosphere using various metal raw materials having a purity of 99.99% and pulverizing the obtained ingot with a stamp mill. Table 1 shows the composition, average particle diameter, and solidus temperature of the obtained raw material powder.

  The raw material powder was packed in a cylindrical rubber mold, inserted into a hydrostatic pressure press in a sealed state with a plastic bag, and subjected to hydrostatic pressure up to the pressure shown in Table 1 to produce a compact. The obtained formed body was inserted into a graphite mold installed in a hot press apparatus after the outer peripheral portion was shaved to adjust the size. Hot pressing was performed in an argon atmosphere at the temperature and pressure shown in Table 1 for 2 hours.

The obtained sintered body was 150 mm in diameter and 8 mm in thickness. The density of the sintered body was calculated from the outer shape and weight. Since the true density of the alloy is unknown, 6.56 g / cm ³ was used as the true density, and the sintered density was calculated as the ratio of the sintered body density to the true density (relative density). Table 1 shows the sintered density obtained by calculation.

  As Comparative Examples 3 to 6, Table 1 shows the results when the same raw material powder was directly inserted into a graphite mold and hot pressed.

  Among the obtained sintered bodies, Examples 4 and 8 and Comparative Examples 4 and 6 were subjected to external processing and bonding to obtain a sputtering target. Table 2 shows the properties of the sputtering target subjected to the test. Using the obtained sputtering target, a sputtering test was performed using a sputtering apparatus (manufactured by Nippon Vacuum Technology Co., Ltd.). The results of the sputtering test are also shown in Table 2.

As is apparent from Table 1, it can be seen that a sintered body having a density of 85% or more can be obtained by the present invention. Further, as is apparent from Table 2, it can be seen that sputtering can be performed without any problems by setting the density to 85% or more.

It shows a rubber mold used for an isostatic press.

Explanation of symbols

1 Lower rubber plate 2 Upper rubber plate 3 Cylindrical rubber 4 Raw material powder

Claims (5)

  After the raw material powder is filled into a rubber mold having a predetermined shape, a step of obtaining a green compact by subjecting the raw material powder to isostatic pressing at a pressure of 0.5 ton or more, and the green compact is baked by hot pressing. The manufacturing method of the sintered compact characterized by including the process to tie.   A step of obtaining a green compact by filling a GaSb-based alloy powder into a rubber mold having a predetermined shape and then subjecting the GaSb-based alloy powder to isostatic pressing at a pressure of 0.5 tons or more, and hot pressing the green compact The manufacturing method of the GaSb type alloy sputtering target characterized by including the process sintered by.   A GaSb-based alloy target having a relative density of 85% or more.   The GaSb-based alloy target according to claim 3, wherein the GaSb-based alloy contains Ga of 1 atomic% or more and less than 50 atomic%, and the balance is composed of Sb and inevitable impurities. The GaSb-based alloy according to claim 3, wherein the GaSb-based alloy is an alloy based on a GaSb alloy containing 1 atomic% or more and less than 50 atomic% of Ga, and the solidus temperature is 589 ° C or lower. target.

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