TWI458848B - Cu-Ga sintered body sputtering target and manufacturing method of the target - Google Patents

Description

Cu-Ga sintered body sputtering target and method for manufacturing the same

The present invention relates to a Cu-Ga sintered body sputtering target used for forming a Cu-In-Ga-Se (hereinafter referred to as CIGS) quaternary alloy thin film (that is, a light absorbing layer of a thin film solar cell layer) and the target Manufacturing method.

In recent years, mass production of CIGS-based solar cells having high efficiency as thin-film solar cells is progressing, and vapor deposition methods and selenization methods are known as methods for producing light-absorbing layers. Although the solar cell manufactured by the vapor deposition method has the advantages of high conversion efficiency, it has the disadvantages of low film formation speed, high cost, and low productivity, and the selenization method is more suitable for mass production in the industry.

The process of the selenization process is summarized as follows. First, a molybdenum electrode layer is formed on a soda lime glass substrate, and a Cu-Ga layer and an In layer are formed by sputtering thereon, and then a CIGS layer is formed by high temperature treatment in a hydrogenated selenium gas. A Cu-Ga target is used in the sputtering film formation of the Cu-Ga layer in the CIGS layer formation process by this selenization method.

The manufacturing method of the Cu-Ga target includes a melting method and a powder method. In general, the Cu-Ga target produced by the melting method has less impurity contamination, but has problems such as large composition segregation and a decrease in yield due to a shrinkage cavity. The target produced by the powder method has a sintered density. Low, easy to break and other issues.

Various factors will affect the conversion efficiency of CIGS solar cells, and the CIGS film characteristics will also have a great impact. The characteristics of the Cu-Ga film before the formation of the CIGS film will also affect the conversion efficiency of the solar cell. It has a big impact. The target obtained by sintering the powder has a characteristic that the composition is less segregated, easier to manufacture, and easy to adjust the composition as needed, compared with the melted product, and has a larger advantage than the melted product.

However, the target obtained by sintering has a problem that the Cu-Ga target is highly brittle and easily broken. If the target is processed to rupture, the target manufacturing yield is lowered, and if it is broken during sputtering, the yield of the CIGS solar cell is lowered. Both ultimately relate to the rise in the cost of manufacturing CIGS solar cells.

One of the documents relating to the Cu-Ga target up to now is Patent Document 1 which produces a Cu-Ga target by a melting method. The feature of Patent Document 1 is that a Cu-Ga target is implanted with In. In Patent Document 1, although there is no description about the abnormal discharge or the like and the relative density is 95% or more, the crack of the obtained target is not particularly described.

In general, the melted product is of higher density than the sintered product, and is usually less than 100% dense. However, the paragraph [0010] of Patent Document 1 describes "a high density of a relative density of 95% or more", and there is a description of achieving such a degree of density.

Therefore, the relative density of about 95% is definitely not called high density. In fact, in this patent document 1, in the melted product, pores and poor pores (voids) which lower the density are generated.

Further, although the description of the composition segregation has not been observed, the analysis results and the like are not disclosed at all. From the description of the relative density of the above-mentioned degree, only the improvement of the segregation of the level of the recognized level is described.

In general, the melting method generally has a large compositional segregation, and since it has not undergone a special step for eliminating segregation, it is considered that it will have a general degree of segregation.

The segregation characteristic of such a molten product has a problem that a change in film composition occurs during sputtering. The sputtering conditions are also unknown.

Therefore, in the molten product, a hole which causes a decrease in density, a defective void (void), or a target of segregation is more likely to be broken than the powder sintered body.

Further, in the other literature (Patent Document 2) of the Cu-Ga target, a sintered body target is described, and there is a description of a conventional technique in which cracking and defect brittleness are likely to occur when the target is cut, and in order to solve this problem, two types of manufacturing are manufactured. The powder is mixed and sintered. One of the two powders is a powder which increases the Ga content, and the other is a powder which reduces the Ga content, and is a two-phase coexisting organizer surrounded by a grain boundary phase.

Since this step is to produce two kinds of powders beforehand, the steps are complicated, and the physical properties and the structure of the hardness of the various powders are different. Therefore, it is difficult to form a uniform sintered body only by mixing and sintering, and the density cannot be expected to be improved. A target with a lower density will of course cause cracking.

In Patent Document 2, although the crack at the time of cutting is evaluated as good, the problem of cracking at the time of sputtering is still unknown. Since the target structure is not a surface but an internal problem, the problem that the two-phase coexisting structure is broken at the time of sputtering is considered to be a problem different from the machinability of the surface. Even if the problem of cracking at the time of sputtering can be solved, since the structure of the target becomes a two-phase coexisting structure, a non-uniform sputtering film may be generated. It can be said that the cost increase caused by the production of the two powders and the above problems are implied.

In Patent Document 3, in addition to one of the materials of the recording layer of the optical recording medium, CuGa ₂ is exemplified, and the AuZn recording layer is deposited by sputtering. However, there is no description of sputtering of CuGa ₂ , but only the sputtering of CuGa ₂ is suggested.

In Patent Document 4, in addition to one of the materials of the recording layer of the optical recording medium, CuGa ₂ is exemplified, and the AuSn recording layer is deposited by sputtering. There is no description of sputtering of CuGa ₂ , but only the sputtering of CuGa ₂ is suggested.

Patent Document 5, in claim 29, describes a copper alloy target containing 100 ppm or more and less than 10% by weight of Ga, having an average crystal grain size of 1 to 20 μm, and having a crystal grain size uniformity of the entire target of less than 15%. Standard deviation. The purpose is to make the Ga concentration low and to make the target made by forging and calendering have a specific texture.

Patent Document 6 proposes a copper alloy in which an additive element containing Ga is added in a range of a solid solution limit of 0.1 to 20.0 at%. However, the examples shown in the examples are only Cu-Mn alloys, and the method for producing the targets is not specifically described, and it is considered to be obtained by a melting method. The purpose is for display devices.

Patent Document 7 is a copper alloy target obtained by subjecting a raw material component of a powder to a water pressure compression, and a method for producing a target using a mixture of indium powder and Cu-Ga alloy powder as a raw material is described in Example 3. . Compared with the invention of the present application, sintering is not performed, and the composition is also different, and there is no relevant element.

Patent Document 8 describes a sputtering target for a Cu alloy recording layer containing 1 to 20 at% Ga. However, in the examples, it is described that a material obtained by adding Zn or Mn to Cu in an arc melting furnace is used. Ingots do not have any specific records regarding the addition of a copper alloy target of Ga.

Patent Document 9 describes an example of use of a CuGa alloy target for use in 10, 20, or 30% by weight of Ga for the production of a CIGS-type thin film solar cell. However, there is no description of the method for producing the CuGa alloy target itself. . Further, the characteristics of the target are also not described in the same manner.

Patent Document 10 describes a method of producing a CuGa alloy target containing 25 to 67 at% of Ga by a forging quenching method. Although it is used for a thin film solar cell as in the present invention, it has a disadvantage unique to forging, and the problem to be solved by the invention of the present application still exists.

Patent Document 11 defines a CuGa alloy target containing 20 to 96% by weight of Ga, and in the examples, it is described that Ga25 wt% and Cu75 wt% are particularly effective. However, there is no description about the method of producing the Cu-Ga alloy target itself, and the properties of the target are also not described. In the above-mentioned patent documents, the disclosure of the subject matter of the present invention and the means for solving the same can be found.

Patent Document 1: Japanese Laid-Open Patent Publication No. 2000-73163

Patent Document 2: JP-A-2008-138232

Patent Document 3: Japanese Laid-Open Patent Publication No. 63-37834

Patent Document 4: Japanese Laid-Open Patent Publication No. 62-379533

Patent Document 5: Japanese Patent Publication No. 2005-533187

Patent Document 6: International Publication WO2006-025347

Patent Document 7: International Publication WO2007-137824

Patent Document 8: International Publication WO2007-004344

Patent Document 9: Japanese Laid-Open Patent Publication No. Hei 10-135498

Patent Document 10: Unexamined Patent No. 1719626

Patent Document 11: Japanese Patent Laid-Open No. Hei 11-260724

In view of the above circumstances, an object of the present invention is to provide a Cu-Ga sintered body target which can improve bending strength, suppress target production, and target during sputtering film formation, and a method for producing the same. Cracking and increasing yield, reducing CIGS layer formation procedures and the cost of CIGS solar cell manufacturing.

In order to solve the above problems, the inventors of the present invention have found that in order to prevent composition segregation, there is a limit to the use of the melting method, and it is necessary to use a powder method to make the composition uniform in composition; and to reduce the brittleness, the target is improved. It is effective to set the density, to set the average particle diameter within a specific range, and the like, and the present invention has been completed.

That is, the present invention provides

1) A Cu-Ga alloy sintered body sputtering target, which is characterized in that it is composed of a sintered body of Cu-Ga alloy powder having a Ga concentration of 20 to 60 at% and a remaining portion of Cu and an unavoidable impurity, The sintered body has a relative density of 97% or more, an average crystal grain size of 5 to 30 μm, and a bending strength of 150 MPa or more.

2) The Cu-Ga alloy sintered body sputtering target according to the above 1), wherein when the bending strength of the target is F (MPa) and the Ga concentration is N (at%), F>-10×N+ is satisfied. 600 relationship,

3) The Cu-Ga alloy sintered body sputtering target according to the above 1) or 2), wherein the Cu-Ga alloy is composed of a single composition,

(4) The Cu-Ga alloy sintered body sputtering target according to any one of the above-mentioned items 1 to 3, wherein the peak intensity of the main peak other than the X-ray diffraction of the Cu-Ga alloy is 5% or less with respect to the main peak intensity,

The Cu-Ga alloy sintered body sputtering target according to any one of the above 1 to 4, wherein the Cu-Ga alloy composition is substantially a γ phase or a main phase is a γ phase.

Also, the present invention provides

6) A method for producing a Cu-Ga alloy sintered body sputtering target, wherein the Cu and Ga raw materials are melted and cooled, and then the pulverized mixed raw material powder is formed into the above 1) to 5) by hot pressing A method for sputtering a target of a Cu-Ga alloy sintered body, characterized in that the holding temperature during hot pressing is set to be 50 to 200 ° C lower than the melting point of the mixed raw material powder, and the holding time is set to 1 to 3 hours, and the cooling is performed. The speed is set to 5 ° C / min or more, and the pressing pressure of the mixed raw material powder is set to 30 to 40 MPa to perform hot pressing.

7) The method for producing a Cu-Ga alloy sintered body sputtering target according to the above 6), wherein the Cu and Ga raw materials are melted and cooled by a mechanical pulverization method, a gas atomization method or a water atomization method.

According to the present invention, in the Cu-Ga sintered body target, since the bending strength can be improved, the target crack during the target production and the sputtering film formation can be suppressed, and the yield is improved, the CIGS layer forming process and the CIGS sun can be reduced. The excellent effect of the cost of battery manufacturing.

Next, the reason for the definition of the constituent elements of the present invention, the reason, the meaning, the adjustment method, the measurement method, and the like are described.

The Cu-Ga alloy sintered body sputtering target of the present invention has a Ga concentration in the range of 20 to 60 at%, and the remainder is Cu and unavoidable impurities. This is because of the appropriate and preferred Ga concentration range for the actual production of CIGS-based solar cells. However, the technical idea of the present invention itself can also be applied to components outside this range.

In the Cu-Ga alloy sintered body sputtering target of the present invention, the relative density of the sintered body is 97% or more, preferably 98% or more, and more preferably 99% or more. The relative density is the ratio of the actual absolute density of the sintered body target divided by the value of the theoretical density of the target.

The low relative density of the target means that there are a large number of internal pores in the target, which may be the main cause of embrittlement of the sintered body of the Cu-Ga alloy. As shown in the examples and comparative examples described later, the Cu-Ga alloy sintered body target is rapidly embrittled if the Ga content is increased. Therefore, increasing the density of the target has a function of suppressing embrittlement of the Cu-Ga alloy sintered body target and improving the bending strength.

Further, the Cu-Ga alloy sintered body sputtering target system of the present invention has an average crystal grain size of 5 to 30 μm. The average particle size may be slightly etched as needed, and the grain boundaries may be determined and then determined by a planimetric method.

When the average particle diameter is small, the density is easily increased, and the occurrence of cracking can be suppressed by the above-described high density characteristic. On the other hand, if the average particle diameter is large, the crystal grains are randomly aligned, and thus it is easy to advance the cracking.

From the above mechanism, cracking can be suppressed by reducing the average particle diameter. As the average particle diameter increases, the bending strength becomes small, because the average particle diameter is more than about 30 μm, and cracks and cracks are likely to occur due to the relationship with the stress applied during the processing to the target and the sputtering. Further, although the average particle diameter is preferably small, if the average particle diameter is less than 5 μm, it is not advantageous for practical use because of an increase in the number of steps required for production.

The average particle diameter can be adjusted by maintaining the temperature at the time of hot pressing, and the higher the temperature, the larger the particle size.

In general, cracking and cracking during processing and sputtering tend to occur when the bending strength of the target is small, but it does not correspond to the value of the bending strength of 1 to 1, but to a certain extent. The range of the range, even if the same bending strength, if the density and particle size are different, the ease of rupture will be slightly different. In the present invention, the bending strength to the extent that cracking and cracking during processing and sputtering do not occur is defined as 150 MPa or more.

In the Cu-Ga-based alloy, if the Ga concentration is increased, the bending strength tends to decrease. In the present invention, when the bending strength of the target is set to F (MPa) and the Ga concentration is N (at%), the target having high bending strength is defined as the degree of satisfying the relationship of F>-10×N+600. .

The bending strength of the Cu-Ga target is not described in the conventional literature, and the bending strength of the present invention is high at each concentration, so that it has an effect on the crack suppression of the Cu-Ga target. The bending strength can be obtained by a 3-point bending method.

One of the preferable conditions for the Cu-Ga alloy sintered body sputtering target of the present invention is to provide a Cu-Ga alloy sintered body sputtering target composed of a single composition of a Cu-Ga alloy.

The term "single composition" in the present invention is used in the sense of "a composition consisting of a composition in which other components cannot be detected by a usual physical means". Further, at the microscopic level, even if a trace amount of other components is not considered to adversely affect various characteristics, substantially the same effect as a single composition is exhibited.

One of the preferable conditions of the Cu-Ga alloy sintered body sputtering target of the present invention is to provide a Cu-Ga alloy sintered body sputtering target, wherein the peak intensity of the Cu-Ga alloy other than the main peak of the X-ray diffraction is relative to The main peak intensity is 5% or less.

The basis of the singularity can be defined by the X-ray peak intensity ratio. The peak intensity of the other components is substantially the same as the single composition as long as it is 5% or less as compared with the peak of the main composition.

The composition of the mixed raw material powder produced by gas atomization or water atomization is substantially uniform, and the target composition obtained by hot pressing the mixed raw material can be nearly uniform. Further, if the cooling rate is small during hot press cooling, a hetero phase may be precipitated during cooling. If such a heterogeneous amount is large, it can be detected by an X-ray diffraction peak.

The Cu-Ga alloy has a Gamma (γ) phase when the Ga composition is about 30 to 43 at%. This phase is brittle and has the characteristics of being easily broken. Most of the Cu-Ga compositions used in CIGS-based solar cells are particularly in this Ga concentration range. In order to avoid the brittleness of such a Cu-Ga alloy, it is particularly effective to increase the density and increase the bending strength.

Next, the reason and meaning of the scoping, the influence on the characteristics of the target, and the like will be described with respect to the method for producing the target of the present invention.

The Cu and Ga raw materials are weighed in a predetermined composition ratio, placed in a carbon crucible, and heated in a heating furnace pressurized to about 0.5 MPa atmosphere to a melting point of about 50 to 200 ° C to melt the mixed raw material. After maintaining the molten raw material sufficiently for about 1 hour or more, the heating is stopped, and after cooling, the primary synthetic raw material is taken out.

This primary synthetic raw material is pulverized to obtain a fine powder raw material. The pulverization method includes mechanical pulverization, gas atomization method, water atomization method, etc., and any method is acceptable, but the method of water atomization is low in cost and can be processed in a large amount.

In the case of water atomization, the method is as follows: the primary synthetic raw material is once again melted in a crucible, and a liquid material is dropped, and about 10 Mpa of high pressure water is sprayed on the dripping liquid to obtain a fine powder. The obtained fine powder is used after being subjected to pressure filtration, drying, or the like as a raw material for mixing fine powder.

The mixed fine powder raw material is passed through a sieve of a specific opening, the particle size distribution is adjusted, and hot pressing is performed. The hot pressing conditions differ depending on the Ga concentration. For example, when the Ga concentration is 30 at%, the temperature is 600 to 700 ° C and the pressure is 30 to 40 MPa.

That is, in terms of the preferable conditions of the hot pressing, the effective ones are as follows: the temperature at which the hot pressing is maintained is lower than the melting point of the mixed raw material powder by 50 to 200 ° C, the holding time is set to 1 to 3 hours, and the cooling rate is set to 5 ° C. Above /min, the pressure of the mixed raw material powder is set to 30 to 40 MPa. When this hot pressing condition is appropriately selected, the density of the Cu-Ga alloy target can be increased, and the bending strength can be improved.

In terms of the relationship between the temperature profile such as the temperature increase rate and the holding time and the pressure application profile, the pressure is applied first before the pressure is applied to the highest temperature and then the pressure is applied. The powder will be finer and finer, which is effective for increasing the sintered density.

Further, if the cooling rate of the hot pressing is slow, a phase difference occurs between them, so that a rapid temperature at which the cooling rate is 5 ° C/min or more is effective.

The density of the Cu-Ga sintered body produced by the above method can be obtained by the Archimedes method and the average particle diameter can be obtained by a plane method and a composition by X-ray diffraction after surface etching.

The Cu-Ga sintered body can be processed into, for example, a diameter of 6 吋 and a thickness of 6 mm, and then indium is attached to a backing plate as a brazing filler metal as a sputtering target, and then a film is formed. Investigate the state of particle formation, ball formation, and abnormal discharge of the membrane.

Example

Next, examples and comparative examples of the present invention will be described. In addition, since the following examples are representative of representative examples, the present invention is not necessarily limited to the embodiments, and should be construed in the scope of the technical idea described in the specification.

(Example 1)

The Cu raw material and the Ga raw material were weighed so that the Ga concentration of the composition was 30 at%, placed in a carbon crucible, melted at 1000 ° C in a heating furnace to which 0.5 Mpa of argon was applied, and then cooled at a rate of 5 to 10 ° C/min. After cooling, the synthetic raw materials were taken out.

Next, this synthetic raw material was placed in a carbon crucible of a water atomizing apparatus, and after melting at 1000 ° C, the molten liquid was dropped while a high pressure water of 10 MPa was sprayed on the dropping liquid to obtain a Cu-Ga mixed fine powder. The mixed fine powder was filtered under pressure and dried at 120 ° C to obtain a mixed fine powder raw material.

After the mixed fine powder was heated from room temperature to 650 ° C at a temperature elevation rate of 5 ° C / min, it was kept at 650 ° C for 2 hours while applying a pressure of 35 MPa. Thereafter, the mixture was cooled at a temperature drop rate of 5 ° C/min, and then the sintered body was taken out.

The obtained Cu-Ga sintered body had a relative density of 99.9%, an average particle diameter of 11 μm, and an X-ray diffraction peak intensity ratio of the main phase and the heterophase of 0.2%. This sintered body was processed into a disk shape having a diameter of 6 吋 and a thickness of 6 mm to form a sputtering target and sputtering.

In terms of sputtering conditions, the ambient gas is argon and the gas flow rate is 50 sccm, and the sputtering pressure is 0.5 Pa, in particular, the sputtering power (an important condition related to target cracking) is as large as direct current (DC) 1000 W. After 20 hours of the sputtering time, after the total sputtering amount was 20 kWhr, the surface of the target was observed, and no crack was confirmed.

The above results are shown in Table 1.

(Examples 2 to 6)

The target in which the Ga composition and the average particle diameter were changed was prepared in the same manner as in Example 1, and the results of the sputtering evaluation were collectively shown in Table 1. From this result, it was found that a target having a Ga composition, an average particle diameter, and a bending strength within a certain range was obtained as a result of no cracking during processing and sputtering.

(Comparative Example 1 to Comparative Example 2)

The target was produced under substantially the same conditions as in Example 1, except that the temperature at the time of hot pressing was lowered to 600 ° C and 550 ° C, respectively, whereby a target having a low density was produced.

The results of the presence or absence of the characteristics of the target, the occurrence of cracks, and the like are shown in Table 1. Rupture during processing The "less" described in this column means that although the target is not broken and separated, it is somewhat cracked. From this result, if the density of the target is lower than a specific value, cracks are confirmed during processing. However, cracking of the target surface after sputtering was not confirmed.

(Comparative Example 3 to Comparative Example 5)

The target was produced under substantially the same conditions as in Example 1, but the cooling rate was reduced to 1 ° C/min, 2 ° C/min, and 0.5 ° C/min, respectively, whereby the average particle diameter was large and the X-ray intensity ratio was large. The target of the opposite phase.

Table 1 shows the results of the results of the characteristics of the target, the occurrence of cracks, and the like. As a result, it was found that cracks were not observed during sputtering, but there was some cracking during processing.

(Comparative Example 6 to Comparative Example 8)

A Cu-Ga target was produced by a melting method. Cu and Ga raw materials were weighed so that the Ga composition became a specific concentration and placed in a carbon crucible in a heating furnace to which 0.5 Mpa of argon was applied, and Comparative Example 6 was at 1000 ° C, and Comparative Examples 7 and 8 were higher than the respective materials. After melting at a temperature of about 200 ° C, the mixture was cooled and cooled at a cooling rate of about 5 ° C/min, and the results of evaluating the properties of the extracted target, the presence or absence of cracking, and the like were summarized in Table 1.

From this result, it was found that the average particle diameter of the target produced by the melting method was extremely large and the bending strength was extremely small, and cracking at the time of processing and sputtering was confirmed.

Fig. 1 is a graph showing the relationship between the Ga concentration and the bending strength of a Cu-Ga target in the examples and comparative examples of the present invention. As can be seen from the graph, the target of the embodiment of the present invention has a large bending strength, so that it is not broken during processing or sputtering, and a Cu-Ga-based target and film can be produced with good yield.

(industrial availability)

According to the present invention, it is possible to provide a Cu-Ga target having a high Ga concentration without composition segregation, low brittleness, and a Ga concentration of 25 to 45 at%, and a method for producing the same, since the target manufacturing and the yield of the CIGS-based solar cell manufacturing can be improved. Since the manufacturing cost can be reduced, it is used as a material for manufacturing a CIGS-based solar cell using a selenization method.

Fig. 1 is a graph showing the relationship between the Ga concentration of the examples and the comparative examples and the bending strength of the Cu-Ga-based target.

Claims (9)

A Cu-Ga alloy sintered body sputtering target is characterized in that it is composed of a sintered body of a Cu-Ga alloy powder having a Ga concentration of 20 to 60 at% and a remaining portion of Cu and an unavoidable impurity, the sintered body The relative density is 97% or more, the average crystal grain size is 5 to 30 μm, and the bending strength is 150 Mpa or more. For example, in the Cu-Ga alloy sintered body sputtering target according to the first aspect of the patent application, when the bending strength of the target is F (MPa) and the Ga concentration is N (at%), F>-10×N is satisfied. +600 relationship. A Cu-Ga alloy sintered body sputtering target according to claim 1, wherein the Cu-Ga alloy is composed of a single composition. A Cu-Ga alloy sintered body sputtering target according to the second aspect of the patent application, wherein the Cu-Ga alloy is composed of a single composition. The Cu-Ga alloy sintered body sputtering target according to any one of the first to fourth aspects of the invention, wherein the peak intensity other than the main peak of the X-ray diffraction of the Cu-Ga alloy is 5% or less with respect to the main peak intensity. The Cu-Ga alloy sintered body sputtering target according to any one of claims 1 to 4, wherein the Cu-Ga alloy composition is substantially a γ phase or a main phase is a γ phase. A Cu-Ga alloy sintered body sputtering target according to claim 5, wherein the Cu-Ga alloy composition is substantially a γ phase or a main phase is a γ phase. A method for producing a Cu-Ga alloy sintered body sputtering target, which is characterized in that the Cu and Ga raw materials are melted and cooled, and then the pulverized mixed raw material powder is hot pressed by a hot pressing method to manufacture the patent application range 1 to 7. Any of the items The method for sputtering a target of a Cu-Ga alloy sintered body is characterized in that the holding temperature during hot pressing is set to be 50 to 200 ° C lower than the melting point of the mixed raw material powder, and the holding time is set to 1 to 3 hours, and the cooling rate is set. The pressure is 5 to 30 MPa or more, and the pressure of the mixed raw material powder is set to 30 to 40 MPa to perform hot pressing. A method for producing a Cu-Ga alloy sintered body sputtering target according to the eighth aspect of the invention is characterized in that the Cu and Ga raw materials are melted and cooled by a mechanical pulverization method, a gas atomization method or a water atomization method.