JP5882248B2 - Cu-Ga alloy sputtering target, casting product for the sputtering target, and production method thereof - Google Patents

Description

In the present invention, a pore (also referred to as a void or a void) used when forming a Cu—In—Ga—Se (hereinafter referred to as CIGS) quaternary alloy thin film which is a light absorption layer of a thin film solar cell layer. ) -Reduced Cu—Ga alloy sputtering target, a casting product for the sputtering target, and a method for producing them.

In recent years, mass production of high-efficiency CIGS solar cells as thin-film solar cells has progressed, and vapor deposition methods and selenization methods are known as methods for producing the light absorption layer. Solar cells manufactured by vapor deposition have advantages of high conversion efficiency, but have disadvantages of low film formation speed, high cost, and low productivity, and selenization is more suitable for industrial mass production.

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

Various manufacturing conditions, characteristics of constituent materials, and the like affect the conversion efficiency of the CIGS solar cell, but the characteristics of the CIGS film also have a large effect.
As a method for producing the Cu—Ga target, there are a dissolution method and a powder method. In general, a Cu—Ga target manufactured by a melting method is considered to have relatively little impurity contamination, but has a drawback. For example, pores are generated in the target. This is accompanied by abnormal discharge and generation of particles during sputtering. This causes the film quality to deteriorate.

In addition, shrinkage cavities are likely to occur at the final stage when the molten metal is cooled, the properties around the shrinkage cavities are poor, and the yield is poor because it cannot be used for processing into a predetermined shape.
Although there is a description that compositional segregation was not observed in the prior document (Patent Document 1) relating to the Cu—Ga target by the dissolution method, no analysis results or the like are shown. Moreover, no attention is paid to the occurrence of pores in the target, and there is no solution.

On the other hand, targets prepared by the powder method generally have problems such as low sintering density and high impurity concentration. In Patent Document 2 relating to a Cu-Ga target, a sintered body target is described. However, there is an explanation of the prior art regarding brittleness in which cracking and chipping are liable to occur when the target is cut. As mentioned above, two types of powders are manufactured, mixed and sintered. One of the two types of powders is a powder having a high Ga content, and the other is a powder having a low Ga content, which is a two-phase coexisting structure surrounded by a grain boundary phase.

Since this process produces two types of powders, the process is complicated, and the metal powder has a high oxygen concentration, and an improvement in the relative density of the sintered body cannot be expected.
The target with low density and high oxygen concentration naturally has abnormal discharge and particle generation, and if there are irregular shapes such as particles on the surface of the sputtered film, it will adversely affect the characteristics of the subsequent CIGS film. There is a possibility that the conversion efficiency of the solar cell is greatly reduced.

Patent Document 3 describes a Cu—Ga alloy sputtering target having an average crystal grain size of 10 μm or less and a porosity of 0.1% or less, and the uniformity of the composition of the film (film uniformity) In addition, it is possible to form a Cu—Ga sputtering film excellent in) and to reduce the occurrence of arcing during sputtering and to suppress cracking during sputtering, and to improve the denseness. The problem as a sintered body cannot be fundamentally solved.

The big problem of Cu-Ga sputtering target produced by the powder method is that the process is complicated, and the produced sintered body has a high oxygen concentration and a large amount of impurities, so the quality is not always good and the production cost is low. There is a big disadvantage that increases. From this point, a melting / casting method is desired, but as described above, there is a problem in manufacturing, and the quality of the target itself could not be improved.

JP 2000-73163 A JP 2008-138232 A JP 2010-265544 A

The Cu—Ga alloy target is very brittle when the Ga concentration is 25 at% or more, and it has been difficult to produce by melt casting. Moreover, although it can manufacture also by powder sintering, since oxygen concentration is high and the amount of impurities increases, there exists a possibility of degrading a solar cell characteristic. Therefore, in this application, even in a CuGa alloy having a Ga concentration in the range of 25 at% to 35 at%, cracking does not occur, and pores (holes or voids) are reduced, thereby enabling good sputtering with less abnormal discharge and the like. The challenge is to provide a target.

In order to solve the above problems, the present inventors conducted extensive research,
It is a cylindrical cast product that is prepared by adjusting the Ga component composition and melting and casting by the melting method. By optimizing the melting conditions and the HIP conditions, it has been found that a target with extremely small pores can be obtained. Completed the invention.

From the above findings, the present invention provides the following inventions.
1) A cylindrical cast product of a melted and cast Cu-Ga alloy composed of 25 at% or more and 35 at% or less, the balance being Cu and inevitable impurities, and when the cylindrical cast product is cut into round pieces, A Cu-Ga alloy cylindrical cast product, wherein the number of pores having a circle-equivalent diameter of 100 μm or more in a cross section is 3.5 pieces / cm ² or less.
It should be noted that the “equivalent circle diameter” of the pore means a circle equivalent diameter which is the diameter of a circle having the same area as the area of one irregularly shaped pore. The same applies hereinafter.

2) A method for producing a cylindrical cast product by melting and casting a Cu—Ga alloy comprising Ga of 25 at% or more and 35 at% or less, the balance being Cu and inevitable impurities, and the melting temperature of the alloy is (melting point + 100 ) A method for producing a Cu-Ga alloy cylindrical cast product, characterized by melting and casting at a temperature not lower than 1 ° C. and not higher than 1100 ° C. and a high vacuum level of 5.0 × 10 ⁻² torr or higher.
3) The method for producing a Cu-Ga alloy cylindrical cast according to 2) above, wherein the melting temperature of the alloy is (melting point + 100) ° C. or higher and 1040 ° C. or lower.

4) The number of pores having a circle-equivalent diameter of 100 μm or more in a cross section when the cylindrical casting is cut into round pieces by the above manufacturing method is 3.5 pieces / cm ² or less. A method for producing a Cu-Ga alloy cylindrical cast according to 2) or 3).

5) A Cu—Ga alloy sputtering target comprising Ga of 25 at% or more and 35 at% or less and the balance of Cu and inevitable impurities, wherein the number of pores having an equivalent circle diameter of 50 μm or more is 0.3 / A Cu—Ga alloy cylindrical sputtering target characterized by being cm ² or less.

6) A method for producing a Cu—Ga alloy sputtering target comprising Ga of 25 at% or more and 35 at% or less, the balance being Cu and inevitable impurities, and when melting the Cu—Ga alloy raw material, the melting temperature of the alloy ( Melting point + 100) ° C. or higher and 1100 ° C. or lower and a vacuum degree of 5.0 × 10 ⁻² torr or higher, melting and casting to form a Cu—Ga alloy cylindrical cast product, and then applying pressure Cu-, characterized by being subjected to HIP (hot isostatic pressing) at a temperature of 1500 kg / cm ² or more, a temperature of 750 ° C. or more and a melting point of −50 ° C. or less and a holding time of 2 hours or more, and further processed into a target shape. Manufacturing method of Ga alloy cylindrical sputtering target.

7) The melting temperature is set to + 100 ° C. or higher and 1040 ° C. or lower of the melting point of the alloy, and the degree of vacuum is set to a high degree of vacuum of 5.0 × 10 ⁻³ torr or higher. Cu-Ga as described in 6) above, wherein the product is subjected to HIP treatment at a pressure of 1500 kg / cm ² or more, a temperature of 750 ° C. or more (melting point −50) ° C. and a holding time of 3 hours or more. Manufacturing method of alloy cylindrical sputtering target.
8) The method for producing a Cu—Ga alloy cylindrical sputtering target according to 7) above, wherein the number of pores having an average diameter of 50 μm or more is set to 0.3 / cm ² or less by the step.

  According to the present invention, even in a CuGa alloy having a Ga concentration in the range of 25 at% to 35 at%, cracks do not occur, and pores (also referred to as vacancies or voids) are reduced. It has an excellent effect of providing a target capable of sputtering. Further, there is a great advantage that the gas component can be reduced as compared with the sintered compact target. Sputtering using a Cu-Ga alloy target having a cast structure with a small amount of gas components (oxygen, etc.) and a small amount of pores as described above results in less abnormal discharge and less generation of particles and a homogeneous Cu-Ga alloy. A film can be obtained, and the manufacturing cost of the Cu—Ga alloy target can be greatly reduced. Since a light absorption layer and a CIGS solar cell can be manufactured from such a sputtered film, a reduction in conversion efficiency of the CIGS solar cell is suppressed, and a low-cost CIGS solar cell can be produced. Has an excellent effect.

It is explanatory drawing which shows the mode of the pore which generate | occur | produced in the structure | tissue after casting. It is explanatory drawing which shows the gas analysis result inside a micropore. It is a binary phase diagram of Cu-H. It is explanatory drawing which shows an example of the casting method. It is explanatory drawing which shows the example which cuts a cylindrical casting (casting).

The Cu-Ga alloy cylindrical cast of the present invention is made of Cu-Ga alloy in which Ga is 25 at% or more and 35 at% or less, and the balance is made of Cu and inevitable impurities. It is a cylindrical casting. When the cylindrical cast product is cut into round pieces, the number of pores having a circle-equivalent diameter of 100 μm or more in the cross section is set to 3.5 pieces / cm ² or less.
By performing sputtering using a Cu—Ga alloy target having such a cast structure, it is possible to obtain a homogeneous Cu—Ga alloy film with less abnormal discharge and generation of particles. Furthermore, when the light absorption layer and the CIGS solar cell are manufactured using the sputtered film using the Cu—Ga alloy target of the present invention, the reduction in the conversion efficiency of the CIGS solar cell is suppressed, and the low-cost CIGS system is used. A solar cell can be produced.

The Ga content is required from the request for the formation of a Cu—Ga alloy sputtered film that is required when manufacturing a CIGS solar cell. Disclosed is a fused and cast cylindrical Cu-Ga alloy sputtering target having 25 at% or more and 35 at% or less, the balance being Cu and inevitable impurities.

In a conventional sintered product, the target is to set the relative density to 95% or more, further 98% or more. When the relative density is low, when the internal vacancies are exposed during sputtering, the generation of particles and surface irregularities on the film due to splash and abnormal discharge starting from the periphery of the vacancies progress early, and surface protrusions (nodules) This is because an abnormal discharge or the like starting from () is likely to occur. The cast product can achieve a relative density of approximately 100%, and as a result, has an effect of suppressing generation of particles during sputtering. This is one of the major advantages of castings.

The pores need to be reduced as much as possible to reduce abnormal discharge and particles during sputtering. However, in the case of a cylindrical shape such as a rotary target, it has been found that when a molten metal is poured into a mold, large pores (holes) that can be visually confirmed in units of 100 to 500 μm are generated.
The state of the structure | tissue which grind | polished the partial cut surface of the casting ingot is shown in FIG. In the upper diagram of FIG. 1, five pores (micropores) surrounded by circles can be confirmed. The lower figure of FIG. 1 is a photograph of an enlarged structure of one of them. There are pores mainly at the grain boundaries of the crystal structure.

It was found that hydrogen gas was mainly contained in the pores. The gas analysis inside the pore is measured by analyzing the gas while making a hole in the slab with a micro drill, and the presence of hydrogen gas can be confirmed by comparison with a background in which no hole is made with a drill.
The actual gas analysis was carried out using a gas analyzer in the blowhole (Nippon Techno Research) and a mass spectrometer (“A quadrupole mass spectrometer”). The result is shown in FIG. FIG. 2 shows the analysis results of the background (upper figure) and gas release (lower figure).

Although hydrogen is dissolved in copper when dissolved, it is trapped in the solid phase during the solidification process. Therefore, in general, the micropores are finally removed by HIP processing or the like.
However, if there is a certain amount or more of voids per unit area, it may not be completely removed by HIP treatment alone and may remain inside the ingot.

Therefore, by devising the melting conditions, that is, the melting temperature of the Cu—Ga alloy having Ga of 25 at% or more and 35 at% or less and the balance being Cu is set to (melting point + 100) ° C. or more and 1100 ° C. or less of the alloy, The melting point is +100) ° C. or higher and 1040 ° C. or lower, and the degree of vacuum is 5.0 × 10 ⁻² torr or higher, and further high melting degree is 5.0 × 10 ⁻³ torr or higher. Could be reduced or eliminated.
That is, the number of pores having a circle-equivalent diameter of 100 μm or more in the cross section when the cylindrical cast product is cut into round pieces can be 3.5 pieces / cm ² or less.
The melting point of the alloy can be determined from a binary phase diagram of Cu-Ga (reference material: ASM's Binary Alloy data base). For example, when Ga is 25 at%, the melting point is 890 ° C. from the binary phase diagram of Cu—Ga.

In this case, if the dissolution temperature exceeds 1100 ° C., the hydrogen solubility in the liquid phase increases and cannot be removed sufficiently. More preferably, the melting temperature is 1040 ° C. or lower. Even if the degree of vacuum is 5 × 10 ⁻³ torr or more, the gas component is dissolved in the solution and cannot be removed, so the above conditions can be said to be preferable.
FIG. 3 shows a binary phase diagram of Cu—H. The hydrogen solubility limit of Cu is 0.2 at% at about 1075 ° C., and decreases as the temperature decreases. When the melting point exceeds 1084 ° C., the solubility increases by a factor of 3 to 0.6 at%. From this, it can be said that the above temperature range is preferable.

In the production of a Cu-Ga alloy cylindrical sputtering target, a raw material comprising Ga of 25 at% to 35 at% and the balance of Cu as described above has a melting temperature of (melting point + 100) ° C. to 1100 ° C. More preferably, it is 1040 ° C. or less) and the degree of vacuum is as high as 5.0 × 10 ⁻² torr or more. A HIP treatment is performed at a pressure of 1500 kg / cm ² or more, a temperature of 750 ° C. or more (melting point −50) ° C. or less, a holding time of 2 hours or more (more preferably 3 hours or more), and further processed into a target shape. can be the number of pores having an equivalent circle diameter of more than 50μm to obtain a 0.3 / cm ² or less of Cu-Ga alloy cylindrical sputtering target It became.

In this HIP treatment, when the pressure is less than 1500 kg / cm ² , the pores are not sufficiently crushed, and when the temperature is less than 750 ° C., the gas component remains without being diffused. Moreover, it is necessary to set the high temperature holding time to a certain time or longer. Specifically, 2 hours or more, further 3 hours or more are desirable. If the high temperature holding time is insufficient, the gas component contained in the pores is not sufficiently diffused, and pores (holes) often remain.
An example of melt casting of a Cu—Ga alloy is shown in FIG. For example, about 25 kg of Cu and Ga raw materials are dissolved in a graphite crucible so as to have a predetermined CuGa alloy composition. In order to remove water, it is better to beat the graphite tundish with a burner for about 1 hour.

A graphite mold (for example, an outer diameter of 165φ, an inner diameter of 125φ, and a height of 400 mm) having a core and a tundish are placed in the chamber. After evacuation until a predetermined degree of vacuum is achieved, the crucible is heated by induction heating to melt the raw material. And when it becomes predetermined | prescribed temperature, it pours into a casting_mold | template via a tundish and manufactures a cylindrical Cu-Ga alloy ingot.

When evaluating the cylindrical Cu-Ga alloy ingot, as shown in FIG. 5, a cylindrical cast product (cast) having a length of about 300 mm, for example, three locations at positions of 50 mm, 150 mm, and 250 mm from the top, Cut into rounds so that each thickness is 10 mm. At the time of ring cutting, cutting is performed so that the cross-sectional direction is nearly perpendicular to the length direction as shown in FIG. 5 (they are not cut obliquely).
The ingot thus obtained is polished with # 400 emery paper. Then, the number of pores present in the cross section is counted to check whether the requirements of the present invention are satisfied.

Further, a Cu-Ga alloy cylindrical cast product (ingot) is melted and cast to a pressure of 1500 kg / cm ² or more, a temperature range from 750 ° C. to a melting point of −50 ° C., holding time: 2 hours or more (if necessary Cu-Ga alloy cylindrical sputtering target in which the number of pores having a circle-equivalent diameter of 50 μm or more is 0.3 pieces / cm ² or less by processing into a target by HIP treatment for 3 hours or more) Can be obtained. Further, it can be 0 / cm ² .

The sputtering target manufactured in this way is, for example, a sputtering time of 5 hours when the sputtering power is direct current (DC) 1000 W, the atmosphere gas is argon, the gas flow rate is 50 scm, and the sputtering pressure is 0.5 Pa. The number of abnormal discharges in 1 hour between 6 hours and 10 hours or less can be 10 times or less, preferably 5 times or less.
As described above, by controlling the casting conditions and performing the HIP process under appropriate conditions, even if the Ga concentration is in the range of 25 to 35 at%, the target is not cracked and the number of abnormal discharges is reduced by reducing the micropores. CuGa alloy rotary target with reduced can be obtained.

  Next, examples of the present invention will be described. In addition, a present Example is an example to the last, and is not restrict | limited to this example. In other words, all aspects or modifications other than the invention and examples that can be grasped from the entire specification are included within the scope of the technical idea of the present invention.

Example 1
Using the casting apparatus shown in FIG. 4, the additive element Ga (purity: 4N) is adjusted so that the Ga concentration is a composition ratio of 25 at%, and the remaining 25 kg of raw material made of copper (Cu: purity 4N) is carbon. It put in the crucible made, the inside of a chamber was made into the vacuum atmosphere of 5 * 10 < ^-3 > torr, and the crucible was heated to 1100 degreeC by induction heating.
After the raw materials were completely dissolved, argon gas was introduced into the chamber, the molten metal temperature was lowered to 990 ° C., and tapping started when the molten metal temperature became stable. Hereinafter, this temperature will be referred to as the tapping temperature. The tapping was performed by pouring into a mold through a tundish. The shape of the crucible used for melting was 320 mmφ × 400 mmφ, the mold had an outer diameter of 165φ, an inner diameter of 125φ, and a height of 400 mm.

After casting, the ingot was taken out from the mold, and the finished cylindrical casting having a length of about 300 mm was cut into three pieces at a position of 50 mm, 150 mm, and 250 mm from the top so that each thickness was 10 mm. After polishing the cross section of the ingot obtained in this manner with emery paper of # 400, it was confirmed number of pores having an equivalent circle diameter of more than 100μ present in cross-section, 0.8 per unit cm ² in there were.

Further, this cylindrical product was subjected to HIP treatment at a pressure of 1500 kg / cm ² , a temperature of 750 ° C., and a holding time of 3 hours. There were no (0) pores having an equivalent circle diameter of 50 μm or more present in the casting, and 0.3 or less per cm ² was satisfied. The results are shown in Table 1.
Two cylindrical castings having an inner diameter of 135 mm, an outer diameter of 150 mm, and a length of 75 mm were processed into a cylindrical shape, bonded to a titanium backing tube, and sputtered with a splitting target having a total length of 150 mm. The sputtering power was direct current (DC) 1000 W, the atmosphere gas was argon, the gas flow rate was 50 sccm, and the sputtering pressure was 0.5 Pa. When the number of abnormal discharges in one hour between 5 hours and 6 hours after the sputtering time was counted, it was 0. Thereby, the objective of this application was able to be achieved. The results are shown in Table 1.

(Comparative Example 1)
A cylindrical casting cast in the same manner as in Example 1 was subjected to HIP treatment at a pressure of 1500 kg / cm ² , a temperature of 650 ° C., and a holding time of 3 hours. The number of pores having an equivalent circle diameter of 50 μm or more present in the casting was 0.5 per unit cm ² . Although it processed by HIP conditions (low temperature) different from Example 1, the number of pores increased. The results are also shown in Table 1. When sputtering was performed under the same conditions as in Example 1, the number of abnormal discharges was 12, which resulted in many abnormal discharges.

(Example 2)
A cylindrical casting cast in the same manner as in Example 1 except that the tapping temperature was 1040 ° C. was subjected to HIP treatment at a pressure of 1500 kg / cm ² , a temperature of 750 ° C., and a holding time of 3 hours. The number of pores having a circle-equivalent diameter of 50 μm or more present in the casting is 1.4 per unit cm ² , and the number of pores after HIP is none (0) per unit cm ^2. Pieces / cm3 or less were satisfied. The results are shown in Table 1. When sputtering was performed under the same conditions as in Example 1, the number of abnormal discharges was zero. Thereby, the objective of this application was able to be achieved. The results are shown in Table 1.

(Comparative Example 2)
The cylindrical casting cast in the same manner as in Example 2 was subjected to HIP treatment at a pressure of 1500 kg / cm ² , a temperature of 650 ° C., and a holding time of 3 hours. The number of pores having a circle-equivalent diameter of 50 μm or more present in the casting was 1.4 per unit cm ² , and the number of pores after HIP was 0.5 per unit cm ² .
Although it processed by HIP conditions (low temperature) different from Example 2, the number of pores increased. The results are also shown in Table 1. When sputtering was performed under the same conditions as in Example 1, the number of abnormal discharges was 20, which resulted in many abnormal discharges.

(Example 3)
A cylindrical casting cast in the same manner as in Example 1 except that the tapping temperature was 1100 ° C. was subjected to HIP treatment at a pressure of 1500 kg / cm ² , a temperature of 750 ° C., and a holding time of 3 hours. The number of pores having a circle-equivalent diameter of 50 μm or more present in the casting is 3.2 per unit cm ² , and the number of pores after HIP is 0.2 per unit cm ^2. The number / cm ² or less was satisfied. The results are shown in Table 1. When sputtering was performed under the same conditions as in Example 1, the number of abnormal discharges was two. Thereby, the objective of this application was able to be achieved. The results are shown in Table 1.

(Comparative Example 3)
A cylindrical casting cast in the same manner as in Example 3 except that the vacuum degree was 5 × 10 ⁻¹ torr (vacuum degree before tapping) was applied to a pressing force of 1500 kg / cm ² , a temperature of 750 ° C., and a holding time of 3 hours. Then, the HIP treatment was performed. The number of pores having an equivalent circle diameter of 50 μm or more present in the casting was 4.5 per unit cm ² , and the number of pores after HIP was 0.6 per unit cm ² .
Thus, although it processed by the vacuum degree (low vacuum) different from Example 3, the number of pores increased. The results are also shown in Table 1. When sputtering was performed under the same conditions as in Example 1, the number of abnormal discharges was 36, resulting in many abnormal discharges.

Example 4
The additive element Ga (purity: 4N) was adjusted to a composition ratio of Ga concentration of 30 at%, and the raw material was completely dissolved as in Example 1.
After the raw material was completely dissolved, argon gas was introduced into the chamber, the molten metal temperature was lowered to 950 ° C., and the hot water was started when the molten metal temperature was stabilized. The hot water discharge method and the dimensions of the mold are the same as in Example 1.
The cast cylindrical product was subjected to HIP treatment at a pressure of 1500 kg / cm ² , a temperature of 750 ° C., and a holding time of 2 hours. The number of pores having a circle-equivalent diameter of 50 μm or more present in the casting is 1.3 per unit cm ² , and the number of pores after HIP is 0.1 per unit cm ² , 0.3 The number / cm ² or less was satisfied. The results are shown in Table 1. When sputtering was performed under the same conditions as in Example 1, the number of abnormal discharges was two. Thereby, the objective of this application was able to be achieved. The results are shown in Table 1.

(Comparative Example 4)
A cylindrical casting cast in the same manner as in Example 4 was subjected to HIP treatment at a pressure of 1500 kg / cm ² , a temperature of 650 ° C., and a holding time of 3 hours. The number of pores having an equivalent circle diameter of 50 μm or more present in the casting was 1.3 per unit cm ² , and the number of pores after HIP was 0.6 per unit cm ² .
Although it processed by HIP conditions (low temperature) different from Example 4, the number of pores increased. The results are also shown in Table 1. When sputtering was performed under the same conditions as in Example 1, the number of abnormal discharges was 32, resulting in many abnormal discharges.

(Example 5)
A cylindrical casting cast in the same manner as in Example 4 was subjected to HIP treatment at a pressure of 1500 kg / cm ² , a temperature of 800 ° C., and a holding time of 3 hours. The number of pores having a circle-equivalent diameter of 50 μm or more present in the casting is 1.3 per unit cm ² , and the number of pores after HIP is none (0) per unit cm ² . 3 pieces / cm ² or less were satisfied. The results are shown in Table 1. When sputtering was performed under the same conditions as in Example 1, the number of abnormal discharges was one. Thereby, the objective of this application was able to be achieved. The results are shown in Table 1.

(Example 6)
A cylindrical casting cast in the same manner as in Example 4 except that the degree of vacuum was changed to a vacuum atmosphere of 5 × 10 ⁻² torr was subjected to HIP treatment at a pressure of 1500 kg / cm ² , a temperature of 750 ° C., and a holding time of 4 hours. did. The number of pores having a circle-equivalent diameter of 50 μm or more present in the casting is 3.2 per unit cm ² , and the number of pores after HIP is 0.2 per unit cm ^2. The number / cm ² or less was satisfied. The results are shown in Table 1. When sputtering was performed under the same conditions as in Example 1, the number of abnormal discharges was two. Thereby, the objective of this application was able to be achieved. The results are shown in Table 1.

(Example 7)
A cylindrical casting cast in the same manner as in Example 4 except that the tapping temperature was 1040 ° C. was subjected to HIP treatment at a pressure of 1500 kg / cm ² , a temperature of 750 ° C., and a holding time of 3 hours. The number of pores having a circle-equivalent diameter of 50 μm or more present in the casting is 2.2 per unit cm ² , and the number of pores after HIP is 0.3 per unit cm ^2. The number / cm ² or less was satisfied. The results are shown in Table 1. When sputtering was performed under the same conditions as in Example 1, the number of abnormal discharges was four. Thereby, the objective of this application was able to be achieved. The results are shown in Table 1.

(Comparative Example 5)
A cylindrical casting cast in the same manner as in Example 7 was subjected to HIP treatment at a pressure of 1500 kg / cm ² , a temperature of 650 ° C., and a holding time of 3 hours. The number of pores having a circle-equivalent diameter of 50 μm or more present in the casting was 2.2 per unit cm ² , and the number of pores after HIP was 0.8 per unit cm ² .
Although it processed by HIP conditions (low temperature) different from Example 7, the number of pores increased. The results are also shown in Table 1. When sputtering was performed under the same conditions as in Example 1, the number of abnormal discharges was 64, resulting in many abnormal discharges.

(Comparative Example 6)
A cylindrical casting cast in the same manner as in Example 7 was subjected to HIP treatment at a pressure of 1500 kg / cm ² , a temperature of 750 ° C., and a holding time of 1 hour. The number of pores having an equivalent circle diameter of 50 μm or more present in the casting was 2.2 per unit cm ² , and the number of pores after HIP was 0.5 per unit cm ² .
Although it processed by HIP conditions (short time) different from Example 7, the number of pores increased. The results are also shown in Table 1. When sputtering was performed under the same conditions as in Example 1, the number of abnormal discharges was 26, and there were many abnormal discharges.

(Example 8)
A cylindrical casting cast in the same manner as in Example 7 except that the degree of vacuum was 5 × 10 ⁻⁴ torr was subjected to HIP treatment at a pressure of 1500 kg / cm ² , a temperature of 750 ° C., and a holding time of 2 hours. The number of pores having a circle-equivalent diameter of 50 μm or more present in the casting is 1.8 per unit cm ² , and the number of pores after HIP is none (0) per unit cm ^2. Pieces / cm3 or less were satisfied. The results are shown in Table 1. When sputtering was performed under the same conditions as in Example 1, the number of abnormal discharges was one. Thereby, the objective of this application was able to be achieved. The results are shown in Table 1.

Example 9
A cylindrical casting cast in the same manner as in Example 7 except that the degree of vacuum was 5 × 10 ⁻² torr was subjected to HIP treatment at a pressure of 1500 kg / cm ² , a temperature of 750 ° C., and a holding time of 3 hours. The number of pores having an equivalent circle diameter of 50 μm or more present in the casting is 4.0 per unit cm ² , and the number of pores after HIP is 0.3 per unit cm ^2. The number / cm ² or less was satisfied. The results are shown in Table 1. When sputtering was performed under the same conditions as in Example 1, the number of abnormal discharges was three. Thereby, the objective of this application was able to be achieved. The results are shown in Table 1.

(Example 10)
A cylindrical casting cast in the same manner as in Example 4 except that the tapping temperature was 1050 ° C. was subjected to HIP treatment at a pressure of 1500 kg / cm ² , a temperature of 800 ° C., and a holding time of 3 hours. The number of pores having a circle-equivalent diameter of 50 μm or more present in the casting is 3.1 per unit cm ² , and the number of pores after HIP is 0.2 per unit cm ^2. The number / cm ² or less was satisfied. The results are shown in Table 1. When sputtering was performed under the same conditions as in Example 1, the number of abnormal discharges was two. Thereby, the objective of this application was able to be achieved. The results are shown in Table 1.

(Comparative Example 7)
A cylindrical casting cast in the same manner as in Example 4 except that the melting temperature was increased to 1180 ° C. and the hot water was discharged as it was was subjected to HIP treatment at a pressure of 1500 kg / cm ² , a temperature of 750 ° C., and a holding time of 3 hours. . The number of pores having a circle-equivalent diameter of 50 μm or more present in the casting was 4.3 per unit cm ² , and the number of pores after HIP was 0.5 per unit cm ² .
Although it was processed at a different melting and tapping temperature (high temperature) from Example 4, the number of pores increased. The results are also shown in Table 1. When sputtering was performed under the same conditions as in Example 1, the number of abnormal discharges was 28, resulting in many abnormal discharges.

(Comparative Example 8)
A cylindrical casting cast in the same manner as in Example 4 except that the tapping temperature was 1200 ° C. was subjected to HIP treatment at a pressure of 1500 kg / cm ² , a temperature of 750 ° C., and a holding time of 3 hours. The number of pores having an equivalent circle diameter of 50 μm or more present in the casting was 5.4 per unit cm ² , and the number of pores after HIP was 0.7 per unit cm ² .
Although it processed by the tapping temperature (high temperature) different from Example 4, the number of pores increased. The results are also shown in Table 1. When sputtering was performed under the same conditions as in Example 1, the number of abnormal discharges was 49, resulting in many abnormal discharges.

(Example 11)
The additive element Ga (purity: 4N) was adjusted to a composition ratio of Ga concentration of 35 at%, and the raw material was completely dissolved in the same manner as in Example 1.
After the raw materials were completely dissolved, argon gas was introduced into the chamber, the molten metal temperature was lowered to 910 ° C., and the hot water was started when the molten metal temperature was stabilized. The hot water discharge method and the dimensions of the mold are the same as in Example 1.
The cast cylindrical product was subjected to HIP treatment at a pressure of 1500 kg / cm ² , a temperature of 750 ° C., and a holding time of 2 hours. The number of pores having a circle-equivalent diameter of 50 μm or more present in the casting is 1.5 per unit cm ² , and the number of pores after HIP is 0.2 per unit cm ^2. The number / cm ² or less was satisfied. The results are shown in Table 1. When sputtering was performed under the same conditions as in Example 1, the number of abnormal discharges was two. Thereby, the objective of this application was able to be achieved. The results are shown in Table 1.

(Comparative Example 9)
A cylindrical casting cast in the same manner as in Example 11 was subjected to HIP treatment at a pressure of 1500 kg / cm ² , a temperature of 650 ° C., and a holding time of 3 hours. The number of pores having an equivalent circle diameter of 50 μm or more present in the casting was 1.5 per unit cm ² , and the number of pores after HIP was 0.6 per unit cm ² .
Although it processed by HIP conditions (low temperature) different from Example 11, the number of pores increased. The results are also shown in Table 1. When sputtering was performed under the same conditions as in Example 1, the number of abnormal discharges was 40, resulting in many abnormal discharges.

(Example 12)
A cylindrical casting cast in the same manner as in Example 11 was subjected to HIP treatment at a pressure of 1500 kg / cm ² , a temperature of 750 ° C., and a holding time of 5 hours. The number of pores having a circle-equivalent diameter of 50 μm or more present in the casting is 1.5 per unit cm ² , and the number of pores after HIP is none (0) per unit cm ^2. The number / cm ² or less was satisfied. The results are shown in Table 1. When sputtering was performed under the same conditions as in Example 1, the number of abnormal discharges was zero. Thereby, the objective of this application was able to be achieved. The results are shown in Table 1.

(Example 13)
A cylindrical casting cast in the same manner as in Example 11 except that the degree of vacuum was 5 × 10 ⁻² torr was subjected to HIP treatment at a pressure of 1500 kg / cm ² , a temperature of 750 ° C., and a holding time of 3 hours. The number of pores having a circle-equivalent diameter of 50 μm or more present in the casting is 3.3 per unit cm ² , and the number of pores after HIP is 0.3 per unit cm ^2. The number / cm ² or less was satisfied. The results are shown in Table 1. When sputtering was performed under the same conditions as in Example 1, the number of abnormal discharges was three. Thereby, the objective of this application was able to be achieved. The results are shown in Table 1.

(Comparative Example 10)
A cylindrical casting cast in the same manner as in Example 11 except that the degree of vacuum was 5 × 10 ⁻¹ torr was subjected to HIP treatment at a pressure of 1500 kg / cm ² , a temperature of 750 ° C., and a holding time of 3 hours. The number of pores having an equivalent circle diameter of 50 μm or more present in the casting was 4.2 per unit cm ² , and the number of pores after HIP was 0.4 per unit cm ² .
Although it processed by the vacuum degree (low vacuum) different from Example 11, the number of pores increased. The results are also shown in Table 1. When sputtering was performed under the same conditions as in Example 1, the number of abnormal discharges was 11, which resulted in many abnormal discharges.

(Example 14)
A cylindrical casting cast in the same manner as in Example 11 except that the tapping temperature was 1040 ° C. was subjected to HIP treatment at a pressure of 1500 kg / cm ² , a temperature of 750 ° C., and a holding time of 2 hours. The number of pores having a circle-equivalent diameter of 50 μm or more present in the casting is 2.9 per unit cm ² , and the number of pores after HIP is 0.1 per unit cm ² , 0.3 The number / cm ² or less was satisfied. The results are shown in Table 1. When sputtering was performed under the same conditions as in Example 1, the number of abnormal discharges was two. Thereby, the objective of this application was able to be achieved. The results are shown in Table 1.

(Comparative Example 11)
A cylindrical casting cast in the same manner as in Example 14 was subjected to HIP treatment at a pressure of 1500 kg / cm ² , a temperature of 600 ° C., and a holding time of 3 hours. The number of pores having an equivalent circle diameter of 50 μm or more present in the casting was 2.9 per unit cm ² , and the number of pores after HIP was 1.0 per unit cm ² .
Although it processed by HIP conditions (low temperature) different from Example 11, the number of pores increased. The results are also shown in Table 1. When sputtering was performed under the same conditions as in Example 1, the number of abnormal discharges was 72, resulting in many abnormal discharges.

(Example 15)
A cylindrical casting cast in the same manner as in Example 11 except that the degree of vacuum was 5 × 10 ⁻⁴ torr was subjected to HIP treatment at a pressure of 1500 kg / cm ² , a temperature of 750 ° C., and a holding time of 3 hours. The number of pores having a circle-equivalent diameter of 50 μm or more present in the casting is 2.4 per unit cm ² , and the number of pores after HIP is none (0) per unit cm ^2. The number / cm ² or less was satisfied. The results are shown in Table 1. When sputtering was performed under the same conditions as in Example 1, the number of abnormal discharges was one. Thereby, the objective of this application was able to be achieved. The results are shown in Table 1.

(Comparative Example 12)
A cylindrical casting cast in the same manner as in Example 14 except that the degree of vacuum was 5 × 10 ⁻¹ torr was subjected to HIP treatment at a pressure of 1500 kg / cm ² , a temperature of 750 ° C., and a holding time of 3 hours. The number of pores having a circle-equivalent diameter of 50 μm or more present in the casting was 4.3 per unit cm ² , and the number of pores after HIP was 0.5 per unit cm ² .
Although it processed by the vacuum degree (low vacuum) different from Example 14, the number of pores increased. The results are also shown in Table 1. When sputtering was performed under the same conditions as in Example 1, the number of abnormal discharges was 34, and there were many abnormal discharges.

(Example 16)
A cylindrical casting cast in the same manner as in Example 11 except that the tapping temperature was 1050 ° C. was subjected to HIP treatment at a pressure of 1500 kg / cm ² , a temperature of 750 ° C., and a holding time of 6 hours. The number of pores having a circle-equivalent diameter of 50 μm or more present in the casting is 3.1 per unit cm ² , and the number of pores after HIP is 0.2 per unit cm ^2. The number / cm ² or less was satisfied. The results are shown in Table 1. When sputtering was performed under the same conditions as in Example 1, the number of abnormal discharges was two. Thereby, the objective of this application was able to be achieved. The results are shown in Table 1.

(Example 17)
A cylindrical casting cast in the same manner as in Example 11 except that the tapping temperature was 1100 ° C. was subjected to HIP treatment at a pressure of 1500 kg / cm ² , a temperature of 750 ° C., and a holding time of 3 hours. The number of pores having an equivalent circle diameter of 50 μm or more present in the casting is 3.5 per unit cm ² , and the number of pores after HIP is 0.3 per unit cm ^2. The number / cm ² or less was satisfied. The results are shown in Table 1. When sputtering was performed under the same conditions as in Example 1, the number of abnormal discharges was four. Thereby, the objective of this application was able to be achieved. The results are shown in Table 1.

(Comparative Example 13)
A cylindrical casting cast in the same manner as in Example 14 except that the tapping temperature was 1200 ° C. was subjected to HIP treatment at a pressure of 1500 kg / cm ² , a temperature of 750 ° C., and a holding time of 3 hours. The number of pores having an equivalent circle diameter of 50 μm or more present in the casting was 5.5 per unit cm ² , and the number of pores after HIP was 1.2 per unit cm ² .
Although it processed by the tapping temperature (high temperature) different from Example 14, the number of pores increased. The results are also shown in Table 1. When sputtering was performed under the same conditions as in Example 1, the number of abnormal discharges was 84, resulting in many abnormal discharges.

According to the present invention, even a CuGa alloy having a Ga concentration in the range of 25 at% to 35 at% has an excellent effect of providing a target with no cracks and reduced pores (holes or voids). Further, there is a great advantage that the gas component can be reduced as compared with the sintered compact target. Sputtering using a Cu—Ga alloy target having a cast structure with a small amount of gas and a small amount of pores in this way yields a homogeneous Cu—Ga alloy film with less abnormal discharge and particles. And has the effect of greatly reducing the manufacturing cost of the Cu—Ga alloy target.
Since a light absorption layer and a CIGS solar cell can be manufactured from such a sputtered film, it is useful for a solar cell for suppressing a reduction in conversion efficiency of a CIGS solar cell.

Claims (3)

A Cu-Ga alloy cylindrical sputtering target comprising Ga of 25 at% to 35 at% and the balance of Cu and inevitable impurities, wherein the cylindrical sputtering target has a length of 150 mm to 300 mm, and the cylindrical sputtering A Cu-Ga alloy cylindrical sputtering target characterized in that the number of pores having a circle-equivalent diameter of 50 μm or more in a cross section when the target is cut into a ring is 0.3 pieces / cm ² or less. A method for producing a Cu—Ga alloy cylindrical sputtering target comprising Ga at 25 at% to 35 at%, the balance being Cu and inevitable impurities, and when melting a Cu—Ga alloy raw material, the melting temperature of the alloy ( Melting point + 100) ° C. or higher and 1100 ° C. or lower and a vacuum degree of 5.0 × 10 ⁻² torr or higher, melting and casting to form a Cu—Ga alloy cylindrical cast product, and then applying pressure A method for producing a Cu-Ga alloy cylindrical sputtering target, characterized by HIP treatment at 1500 kg / cm ² or more, temperature of 750 ° C. or more (melting point−50) ° C. or less, holding time of 2 hours or more, and further processing into a target shape . Cu-Ga alloy cylindrical cast product by melting and casting with the melting temperature of the same alloy (melting point + 100) ° C. or higher and 1040 ° C. or lower and the vacuum degree of 5.0 × 10 ⁻³ torr or higher. The Cu—Ga alloy according to claim 2, wherein the Cu—Ga alloy is subjected to HIP treatment at a pressure of 1500 kg / cm ² or more, a temperature of 750 ° C. or more (melting point−50) ° C., and a holding time of 3 hours or more. Manufacturing method of cylindrical sputtering target.