WO2012005098A1

WO2012005098A1 - Cu-ga alloy, and cu-ga alloy sputtering target

Info

Publication number: WO2012005098A1
Application number: PCT/JP2011/063802
Authority: WO
Inventors: 智泰矢野
Original assignee: 三井金属鉱業株式会社
Priority date: 2010-07-06
Filing date: 2011-06-16
Publication date: 2012-01-12
Also published as: CN102959107A; JP2012017481A; TW201204844A

Abstract

Disclosed is a Cu-Ga alloy which comprises 25-30 mass% of Ga and a reminder made up by Cu, and which is characterized in that a γ-phase (that is a phase having a Ga concentration appearing on a structure image obtained on an electron microscope of 30-35 mass%) has an average equivalent circle diameter of 50 μm or less and a largest equivalent circle diameter of 200 μm or less. The Cu-Ga alloy rarely undergoes breakage, cracking or the like even when produced by a casting method due to the specific phase structure contained in the structure thereof, and therefore the alloy can be subjected to rolling processing in spite of a fact that the alloy contains Ga at a concentration as high as 25-30 mass%. Therefore, it becomes possible to produce a sputtering target having a high Ga content by rolling, and the productivity of the sputtering target can be improved. When the Cu-Ga alloy is produced by a casting method, the sputtering rate becomes higher compared with that for a Cu-Ga alloy sputtering target that is produced by a powder sintering method such as hot pressing.

Description

Cu-Ga alloy and Cu-Ga alloy sputtering target

The present invention relates to a Cu—Ga alloy and a Cu—Ga alloy sputtering target, and more specifically, a Cu—Ga alloy that can be rolled even when the Ga content is large, and a Cu—Ga alloy sputtering obtained from the alloy. Regarding the target.

In recent years, thin film solar cells using compound semiconductors have been put into practical use. In this thin film solar cell, generally, a Mo electrode layer to be a positive electrode is formed on a soda lime glass substrate, and a light absorption layer made of a Cu—In—Ga—Se alloy film is formed on the Mo electrode layer. A buffer layer made of ZnS, CdS or the like is formed on the light absorption layer, and a transparent electrode layer serving as a negative electrode is formed on the buffer layer.

A method of forming a Cu—In—Ga—Se alloy film by a sputtering method is proposed as a method for forming a light absorption layer made of a Cu—In—Ga—Se alloy film, instead of the vapor deposition method which is slow in film formation speed and cost Has been.

As a method of forming this Cu—In—Ga—Se alloy film by sputtering, a Cu—Ga alloy film is formed by sputtering using a Cu—Ga target and formed on the Cu—Ga alloy film. There has been proposed a method of forming a Cu—In—Ga—Se alloy film by forming a laminated film by sputtering using an In target and then heat-treating the laminated film in a Se atmosphere. This method can also be performed by forming the laminated film in the reverse order, that is, by forming a Cu—Ga film on the In film. As a Cu—Ga alloy target, a Cu—Ga alloy target containing Ga: 1 to 40% by weight and the balance being Cu is known.

As a method for producing this Cu—Ga alloy sputtering target, a powder sintering method such as hot pressing and a casting method such as a vacuum melting method are used. As a Cu—Ga alloy sputtering target manufactured by a powder sintering method, for example, JP-A-2008-138232 discloses a Cu—Ga alloy powder having a Ga content of 30% by mass or more and pure copper powder or Ga content. A Cu—Ga alloy sputtering target obtained by hot pressing a mixed powder with a Cu—Ga alloy powder whose amount is 15 mass% or less is disclosed. However, the Cu—Ga alloy sputtering target manufactured by the hot press method has a drawback that it has a fine structure, but has a high oxygen concentration and a low sputtering rate.

On the other hand, a Cu—Ga alloy sputtering target manufactured by a casting method has an advantage that the oxygen concentration is low and the sputtering rate is fast. However, on the other hand, an ingot made of a Cu—Ga alloy produced by a casting method does not have a fine structure, and is easily segregated and easily cracked. Therefore, a sputtering target is formed by plastic working such as rolling. Has the disadvantage of being difficult. If the sputtering target cannot be formed by rolling, the productivity of the sputtering target cannot be improved. When the Ga concentration of the Cu—Ga alloy is 25% by mass or more, the hardness is high and the possibility of cracking is extremely high, so that it is particularly difficult to perform plastic working such as rolling.

As a technique for solving such defects such as segregation and brittle cracks caused by the casting method, Japanese Patent Application Laid-Open No. 2000-073163 discloses a method of controlling Ga from 15 to 15 while controlling the cooling rate using a mold having heating means and cooling means. An ingot produced by casting a Cu-Ga alloy material containing 70% by mass to produce an ingot, forming island-like holes in the ingot, and injecting molten In into the holes is disclosed. ing.

JP 2008-138232 A JP 2000-073163 A

The ingot disclosed in Japanese Patent Laid-Open No. 2000-073163 suppresses segregation and brittleness by slowing the cooling rate, and it is possible to form a sputtering target by cutting. If the speed is slowed down, one crystal at a time becomes large, so that rolling cannot be performed.

The present invention provides a Cu—Ga alloy that can be rolled even if the Ga content is high, and a Cu—Ga alloy sputtering target that can be produced by rolling even if the Ga content is high. For the purpose.

The inventor of the present invention is concerned with the brittleness of an ingot made of a Cu—Ga alloy obtained by a casting method, which is composed of a phase having a Ga concentration of 30 to 35% by mass, for example, a phase called a γ phase. The inventors have found that the ease of cracking can be controlled by adjusting the size and abundance ratio of the γ phase, and have completed the present invention.

That is, the present invention is a Cu—Ga alloy containing 25 to 30% by mass of Ga, the balance being Cu, and having a Ga concentration of 30 to 35% by mass appearing in a structure image obtained by an electron microscope. The Cu—Ga alloy is characterized in that the average equivalent circle diameter of the γ phase is 50 μm or less and the maximum equivalent circle diameter is 200 μm or less.

As a preferred embodiment of the Cu-Ga alloy,
The total ratio of the area of the γ phase to the area of the tissue image is 5 to 70%,
An alloy for producing a sputtering target.

Another invention is a Cu—Ga alloy sputtering target obtained by rolling the Cu—Ga alloy.

Since the structure of the Cu—Ga alloy of the present invention has a specific phase structure, cracks and chips are hardly generated even when it is produced by a casting method. Therefore, Ga is highly concentrated at 25 to 30% by mass. It can be rolled while containing. For this reason, it is possible to manufacture a sputtering target with a large Ga content by rolling, and the productivity of the sputtering target can be improved. In addition, when the Cu—Ga alloy of the present invention is produced by a casting method, the sputtering rate is faster than a Cu—Ga alloy sputtering target produced by a powder sintering method such as hot pressing.

FIG. 1 is an example of a structure image obtained by observing a cross-section of a Cu—Ga alloy of the present invention produced using a carbon mold at a magnification of 200 times with a scanning electron microscope. FIG. 2 is an example of a structure image obtained by observing a cross section of the Cu—Ga alloy of the present invention manufactured using a water-cooled copper mold with a scanning electron microscope at a magnification of 200 times.

The Cu—Ga alloy of the present invention contains 25 to 30% by mass of Ga, the balance is Cu, the average equivalent circle diameter of the γ phase appearing in the structure image obtained with an electron microscope is 50 μm or less, and the maximum circle The equivalent diameter is 200 μm or less. Here, the γ phase is a phase having a Ga concentration of 30 to 35% by mass. Whether or not the phase appearing in the tissue image is a γ phase can be confirmed by observing a difference in contrast due to a Ga concentration difference in an image (component image) corresponding to the average atomic weight obtained with an electron microscope. it can. The equivalent circle diameter is a diameter of a circle having a Ga concentration of 30 to 35 mass% in the component image obtained above, that is, a circle having the same area as the area of the γ phase. The average equivalent circle diameter is an average value of equivalent circle diameters of all γ phases appearing in the tissue image. The maximum equivalent circle diameter is the largest equivalent circle diameter among all equivalent circle diameters of the γ phase appearing in the tissue image.

As a specific method for obtaining the equivalent circle diameter of the γ phase, in a component image of 0.3 mm ² obtained at a magnification of 200 times, a boundary between the γ phase and another phase is determined, and then image processing is performed. The area of the γ phase is calculated, and a circle having the area is assumed, and the diameter is set as the equivalent circle diameter of the γ phase. The average equivalent circle diameter of the γ phase is obtained by calculating the equivalent circle diameter for all the γ phases appearing in the component image as described above and averaging these. Further, as described above, the equivalent circle diameter is obtained for all the γ phases appearing in the component image, and the maximum value among them is set as the maximum equivalent circle diameter of the γ phase.

In general, when the Ga content is less than about 25% by mass, a Cu—Ga alloy is composed of a phase in which Ga is dissolved in Cu and a phase (β phase) in which the Ga concentration is 20 to 25% by mass. However, when the Ga content is about 25% by mass or more, it is observed from an electron microscope that it is composed of two phases of a phase (γ phase) having a Ga concentration of 30 to 35% by mass and a β phase. It is confirmed.

In the Cu—Ga alloy of the present invention, the average equivalent circle diameter of the γ phase appearing in the structure image obtained with an electron microscope is 50 μm or less, and the maximum equivalent circle diameter of the γ phase is 200 μm or less. That is, the Cu—Ga alloy of the present invention has a uniform structure including a γ phase having an average equivalent circle diameter of 50 μm or less and an equivalent circle diameter of 200 μm or less.

If the average equivalent circle diameter of the γ phase is greater than 50 μm or the maximum equivalent circle diameter is greater than 200 μm, cracks are likely to occur during processing such as rolling. This is because the β phase is a soft and low brittle phase, whereas the γ phase is harder and more brittle than the β phase, so the average equivalent circle diameter is larger than 50 μm or equivalent to a circle. It is considered that when a γ phase having a diameter larger than 200 μm exists, cracks are likely to occur at the portion of the γ phase having a large equivalent circle diameter when a physical force is applied to the alloy. On the other hand, if the average equivalent circle diameter of the γ phase is 50 μm or less and the maximum equivalent circle diameter is 200 μm or less, there is no large γ phase that is prone to such cracking or there is little, so rolling It is considered that cracks are unlikely to occur during processing such as.

For these reasons, the smaller the average equivalent circle diameter and the maximum equivalent circle diameter of the γ phase, the better. The average equivalent circular diameter of the γ phase is preferably 45 μm or less, and more preferably 30 μm or less. The maximum equivalent circle diameter of the γ phase is preferably 150 μm or less, and more preferably 120 μm or less.

For the above reasons, the lower limit of the average equivalent circle diameter and the maximum equivalent circle diameter of the γ phase is not particularly limited. According to the ordinary method for producing the Cu—Ga alloy of the present invention described later, the lower limit value of the average equivalent circle diameter of the γ phase is approximately 10 μm, and the lower limit value of the maximum equivalent circle diameter is approximately 30 μm.

In the Cu—Ga alloy of the present invention, the ratio of the total area of the γ phase to the area of the structure image (hereinafter also referred to as area ratio) is preferably 5 to 70%. In general, the larger the amount of Ga contained in this alloy, the larger the total area of the γ phase appearing in the structure image, but even if the amount of Ga contained in the alloy is the same, whether Ga is contained in the γ phase Therefore, the total area of the γ phase appearing in the structure image may be different. If the area ratio is greater than 70%, the proportion of the highly brittle γ phase increases, so that even if the average equivalent circle diameter of the γ phase is 50 μm or less and the maximum equivalent circle diameter is 200 μm or less, rolling is performed. There is a high possibility of cracking during processing such as. In addition, when the Ga content of the Cu—Ga alloy is 25 to 30% by mass, the area ratio is usually not less than 5% by mass.

The ratio R of the total area of the γ phase with respect to the area of the tissue image is calculated in the same manner as described above for the area of all γ phases appearing in the component image obtained at a magnification of 200 times. Where S is the area, R (%) = (Sγ / S) × 100.

The Cu—Ga alloy of the present invention contains 25 to 30% by mass of Ga and the balance is Cu. When the Cu—Ga alloy has such a composition, a sputtering target capable of forming a Cu—Ga film effective as a light absorption layer of a solar cell can be manufactured. Further, if the Cu—Ga alloy has such a composition, cracks are likely to occur as described above, and therefore there is a high need to control these cracks. Note that the Cu—Ga alloy of the present invention may contain unavoidable impurities in addition to Ga and Cu.

The shape of the Cu—Ga alloy of the present invention is not particularly limited, and the shape can be appropriately determined according to the use of the alloy.

As described above, since the Cu—Ga alloy of the present invention is not easily broken even when a physical force is applied, various products can be manufactured by appropriately performing plastic working. For example, a sputtering target can be produced by rolling the Cu—Ga alloy of the present invention.

As a rolling method performed when the sputtering target is produced from the Cu—Ga alloy of the present invention, a known rolling method performed on a normal alloy, for example, an alloy plate is adjusted to a predetermined rolling temperature, and a rolling mill is used. An example is a method in which the alloy is rolled at a predetermined rolling reduction, and this is repeated as appropriate to gradually reduce the thickness of the alloy.

The rolling temperature is usually 500 to 850 ° C., preferably 700 to 850 ° C., more preferably 750 to 800 ° C. When the rolling temperature is lower than 500 ° C., the β phase does not become sufficiently soft, so that the alloy cannot withstand deformation due to rolling, and surface cracks and cracks are generated by rolling, making it difficult to obtain a sputtering target that can withstand use. . On the other hand, when the rolling temperature is higher than 850 ° C., there is a possibility that the material is melted by heat generated by deformation due to rolling or partly melted during heating.

As the rolling mill, a normal rolling mill used for rolling an alloy, for example, a rolling mill having a pair of rolling rollers can be used.

The rolling reduction is preferably 2 to 23%. When the rolling reduction is less than 2%, the number of rolling steps to be performed until the alloy plate reaches a desired thickness increases, and thus the productivity decreases. If the rolling reduction is greater than 23%, the alloy plate is likely to crack, and the load on the rolling mill becomes large. It is preferable in terms of productivity that the reduction ratio is set to a high value within a range in which the alloy plate is not cracked. The maximum rolling reduction that can be used, that is, the maximum value of the rolling reduction at which cracking does not occur even when rolling, depends on the rolling temperature and Ga concentration. The higher the rolling temperature and the lower the Ga concentration, the higher the maximum rolling reduction. The reduction ratio r is given by the following equation, where h _{1 is} the thickness of the alloy sheet after rolling once and h ₂ is the thickness of the alloy sheet before rolling.

The sputtering target thus obtained is joined to a backing plate and used for sputtering.

The method for producing the Cu—Ga alloy of the present invention is not particularly limited, and for example, a casting method such as a vacuum melting casting method, an atmospheric melting casting method and a semi-continuous casting method can be used. The Cu—Ga alloy of the present invention can be efficiently produced by a melting casting method including the following melting process and casting process.

[Dissolution process]
Each metal material is mixed and melted to obtain a molten metal.

As the metal material, Cu pure metal, Ga pure metal and Cu-Ga alloy can be used, a combination of Cu pure metal and Ga pure metal, Cu-Ga alloy only, Cu pure metal and Cu Any of a combination of a —Ga alloy, a combination of a pure metal of Ga and a Cu—Ga alloy, and a combination of a pure metal of Cu, a pure metal of Ga, and a Cu—Ga alloy may be used.

The mixing ratio of each metal material is such that the Ga content of the Cu—Ga alloy produced through the main melting step and the casting step is 25 to 30% by mass.

．Mix the blended metal material in a melting furnace. As the melting furnace, a melting furnace used in a normal melting casting method can be used, and for example, a high-frequency melting furnace, an electric furnace, or the like can be used. Among these, a high frequency melting furnace is preferable. In the high-frequency melting furnace, sufficient stirring is performed during melting, so that the molten metal has a uniform composition distribution, segregation and coarse particles are unlikely to occur in the ingot produced through the casting process, It is easy to reduce the equivalent circle diameter of the γ phase. On the other hand, in an electric furnace, stirring during melting tends to be insufficient, and composition distribution is likely to occur in the molten metal, so segregation and coarse particles are likely to occur in the ingot produced through the casting process, It is difficult to reduce the equivalent circle diameter of the γ phase. In particular, when mixing and using metal materials with greatly different compositions, such as a combination of pure Cu and pure Ga metals, the electric furnace may be insufficiently stirred during melting. High nature. However, even if an electric furnace is used, a molten metal material having a uniform composition distribution can be obtained by sufficiently stirring the molten metal material using a stirring rod or the like, and the above problems can be solved. Is possible. However, contamination may occur in the molten metal due to a stirring rod or the like.

The melting temperature is preferably 1200 to 1400 ° C., more preferably 1200 to 1300 ° C. When the melting temperature is lower than 1200 ° C., the molten metal is solidified at the stage of pouring the molten metal into the mold, and it becomes difficult to obtain a target ingot. In order to avoid such a problem, it is preferable that the melting temperature is higher by about 300 to 500 ° C. than the melting point of the alloy to be produced. On the other hand, if the melting temperature is higher than 1400 ° C., the cooling time becomes longer in the casting process, so that the growth of the structure proceeds during that time, segregation and coarse particles are likely to occur, and it is difficult to reduce the equivalent circle diameter of the γ phase. It becomes an ingot that tends to be cracked.

[Casting process]
The molten metal obtained in the melting step is poured into a mold and then cooled to obtain an ingot.

It is preferable to increase the speed at which the molten metal is poured into the mold, that is, the casting speed, because the equivalent circle diameter of the γ phase can be reduced. Since the equivalent circle diameter of the γ phase has a correlation with the cooling rate of the molten metal as described later, if the casting rate is low, it becomes difficult to quickly cool the entire molten metal, and the γ phase grows during cooling. It is considered that the equivalent circle diameter of the γ phase will increase. On the other hand, when the casting speed is high, the entire molten metal can be rapidly cooled, so that growth of the γ phase during cooling can be suppressed, and as a result, the equivalent circle diameter of the γ phase is considered to be small. However, if the molten metal poured into the mold can be quickly cooled, the equivalent circle diameter of the γ phase can be reduced even if the casting speed is low. For this reason, when the water-cooled copper mold is used, it is easy to reduce the equivalent circle diameter of the γ phase even if the casting speed is reduced compared to the case where the carbon mold is used.

For example, when a molten metal of 1200 to 1400 ° C. is cast into a carbon mold of 550 mm × 145 mm × 30 mm, the casting speed is preferably 200 to 1000 g / sec, more preferably 400 to 800 g / sec. When casting a molten metal at 1200 to 1400 ° C. in a water-cooled copper mold of 460 mm × 160 mm × 30 mm, the casting speed is preferably 200 to 800 g / sec, more preferably 250 to 600 g / sec.

The cooling rate of the molten metal is an important point in producing the Ga—Cu alloy of the present invention. When the cooling rate is low, the γ phase grows during cooling, and the equivalent circle diameter of the γ phase increases. On the other hand, when the cooling rate is large, the growth rate of the γ phase is small, the structure of the alloy is refined, and the equivalent circle diameter of the γ phase is small. A suitable cooling rate is 5 to 500 ° C./min. If the cooling rate is less than 5 ° C./min, the alloy structure becomes coarse, and it becomes difficult to make the average equivalent circle diameter of the γ phase 50 μm or less, or to make the maximum equivalent circle diameter 200 μm or less. On the other hand, if the cooling rate is higher than 500 ° C./min, the molten metal will harden in a short time when entering the mold, and it will not become a continuous ingot, but the ingot will be wrinkled or the ingot will be layered. Tend. A more preferable cooling rate is 10 to 150 ° C./min, and a further preferable cooling rate is 20 to 100 ° C./min.

As the mold, a mold used in a normal melt casting method can be used, and for example, a water-cooled copper mold and a carbon mold can be used. Among these, the water-cooled copper mold is preferable in that it can take a large cooling rate, and as described above, it is easy to refine the structure of the alloy and reduce the equivalent circle diameter of the γ phase. When a water-cooled copper mold is used, the cooling rate can usually be 40 to 200 ° C./min, and when a carbon mold is used, the cooling rate can be usually 5 to 20 ° C./min. .

The shape and dimensions of the mold are not particularly limited, but as described above, it is preferable that the cooling rate is high. Therefore, the shape and dimensions that can increase the cooling rate are preferable.

An example of a structure image obtained by observing a cross-section of the Cu—Ga alloy of the present invention manufactured using a carbon mold with a scanning electron microscope at a magnification of 200 times is manufactured using a water-cooled copper mold. FIG. 2 shows an example of a structure image obtained by observing a cross section of the Cu—Ga alloy of the present invention with a scanning electron microscope at a magnification of 200 times. For any Cu—Ga alloy, pure Cu and pure Ga were weighed so that the Ga concentration was 28% by mass, melted at 1200 ° C. in a high-frequency melting furnace to produce a molten metal, and then the former Cu—Ga. For the alloy, this molten metal was poured into a carbon mold and cooled at a cooling rate of 10 to 20 ° C./min. For the latter Cu—Ga alloy, this molten metal was poured into a water-cooled copper mold. And cooled at a cooling rate of 20 to 60 ° C./min. In any tissue image, the portion displayed in light color is the γ phase, and the portion displayed in dark color is the β phase. Both Cu—Ga alloys differ only in the mold used in the production process and the cooling rate, but from the comparison between FIG. 1 and FIG. 2, the Cu—Ga alloy of the present invention produced using a water-cooled copper mold. It can be seen that the Ga alloy has a smaller equivalent circle diameter of the γ phase than the Cu—Ga alloy of the present invention manufactured using a carbon mold.

By the manufacturing method including the melting step and the casting step as described above, an ingot that is the Cu—Ga alloy of the present invention is obtained.

(Comparative Production Example 1)
Pure Cu and pure Ga were weighed so that the Ga concentration was 28% by mass, and using a high-frequency vacuum melting furnace (FVM-30, manufactured by Fuji Radio Industry Co., Ltd.) in an Ar atmosphere at 15 ° C./min. The temperature was raised and after confirming that the raw material had melted, the molten metal temperature was maintained at 1000 ° C. The obtained molten metal was poured into a carbon mold of 550 mm × 145 mm × 30 mm at a casting speed of 500 g / sec. At this time, the melt began to solidify before the injection was completed. The molten metal poured into the carbon mold was cooled to 200 ° C. at a cooling rate of about 13 ° C./min to obtain an ingot. Since this ingot was solidified intermittently, it was layered and did not become a good ingot. The results are summarized in Table 1.

(Comparative Production Example 2)
A molten metal was produced under the same conditions as in Comparative Production Example 1. This molten metal was poured into a 460 mm × 160 mm × 30 mm water-cooled copper mold at a casting speed of 500 g / sec. At this time, the melt began to solidify before the injection was completed. The molten metal poured into the water-cooled copper mold was cooled to 50 ° C. at a cooling rate of about 100 ° C./min to obtain an ingot. In this ingot, many defects were generated at the portion where solidification occurred, and the ingot was not good. The results are summarized in Table 1.

(Comparative Production Example 3)
Pure Cu and pure Ga were weighed so that the Ga concentration was 28% by mass, and using a high-frequency vacuum melting furnace (FVM-30, manufactured by Fuji Radio Industry Co., Ltd.) in an Ar atmosphere at 15 ° C./min. The temperature was raised and after confirming that the raw material had melted, the molten metal temperature was maintained at 1100 ° C. The obtained molten metal was poured into a carbon mold of 550 mm × 145 mm × 30 mm at a casting speed of 500 g / sec. At this time, the melt began to solidify before the injection was completed. The molten metal poured into the carbon mold was cooled to a cooling rate of about 13 ° C./min to 200 ° C. to obtain an ingot. Since this ingot was solidified intermittently, it was not as good as the ingot obtained in Comparative Production Example 1, but it was layered and did not become a good ingot. The results are summarized in Table 1.

(Comparative Production Example 4)
A molten metal was produced under the same conditions as in Comparative Production Example 3. This molten metal was poured into a 460 mm × 160 mm × 30 mm water-cooled copper mold at a casting speed of 500 g / sec. At this time, the melt began to solidify before the injection was completed. The molten metal poured into the water-cooled copper mold was cooled to 50 ° C. at a cooling rate of about 100 ° C./min to obtain an ingot. Although this ingot was not as large as the ingot obtained in Comparative Production Example 2, a number of defects were generated at the locations where solidification occurred, and the ingot was not good. The results are summarized in Table 1.

(Production Example 1)
Pure Cu and pure Ga were weighed so that the Ga concentration was 28% by mass, and using a high-frequency vacuum melting furnace (FVM-30, manufactured by Fuji Radio Industry Co., Ltd.) in an Ar atmosphere at 15 ° C./min. The temperature was raised and after confirming that the raw material had melted, the molten metal temperature was maintained at 1200 ° C. The obtained molten metal was poured into a carbon mold of 550 mm × 145 mm × 30 mm at a casting speed of 500 g / sec. At this time, the molten metal did not begin to solidify before the injection was completed. The molten metal poured into the carbon mold was cooled to 200 ° C. at a cooling rate of about 13 ° C./min to obtain an ingot. This ingot was cut into a size of about 10 mm square, mirror-polished, and the cross section was observed with a scanning electron microscope (manufactured by JEOL Co., Ltd., JSM-6380A) at a magnification of 200 times. By the above-described method, the average equivalent circle diameter and the maximum equivalent circle diameter of the γ phase were obtained from the obtained tissue image. The results are summarized in Table 1. According to the above production conditions, a good ingot which is the Cu—Ga alloy of the present invention was obtained.

(Production Example 2)
A molten metal was produced under the same conditions as in Production Example 1. This molten metal was poured into a 460 mm × 160 mm × 30 mm water-cooled copper mold at a casting speed of 500 g / sec. At this time, the molten metal did not begin to solidify before the injection was completed. The molten metal poured into the water-cooled copper mold was cooled to 50 ° C. at a cooling rate of about 100 ° C./min to obtain an ingot. The ingot was observed with a scanning electron microscope under the same conditions as in Production Example 1 to determine the average equivalent circle diameter and the maximum equivalent circle diameter of the γ phase. The results are summarized in Table 1. According to the above production conditions, a good ingot which is the Cu—Ga alloy of the present invention was obtained.

(Comparative Production Example 5)
Pure Cu and pure Ga were weighed so that the Ga concentration was 28% by mass, and using a high-frequency vacuum melting furnace (FVM-30, manufactured by Fuji Radio Industry Co., Ltd.) in an Ar atmosphere at 15 ° C./min. The temperature was raised and after confirming that the raw material had melted, the molten metal temperature was maintained at 1300 ° C. The obtained molten metal was poured into a carbon mold of 550 mm × 145 mm × 30 mm at a casting speed of 500 g / sec. At this time, the molten metal did not begin to solidify before the injection was completed. The molten metal poured into the carbon mold was cooled to 200 ° C. at a cooling rate of about 13 ° C./min to obtain an ingot. The ingot was observed with a scanning electron microscope under the same conditions as in Production Example 1 to determine the average equivalent circle diameter and the maximum equivalent circle diameter of the γ phase. The results are summarized in Table 1. Under the above production conditions, a good ingot was obtained, but the average equivalent circle diameter of the γ phase was larger than 50 μm, and the Cu—Ga alloy of the present invention could not be obtained.

(Production Example 3)
A molten metal was produced under the same conditions as in Comparative Production Example 5. This molten metal was poured into a 460 mm × 160 mm × 30 mm water-cooled copper mold at a casting speed of 500 g / sec. At this time, the molten metal did not begin to solidify before the injection was completed. The molten metal poured into the water-cooled copper mold was cooled to 50 ° C. at a cooling rate of about 100 ° C./min to obtain an ingot. The ingot was observed with a scanning electron microscope under the same conditions as in Production Example 1 to determine the average equivalent circle diameter and the maximum equivalent circle diameter of the γ phase. The results are summarized in Table 1. According to the above production conditions, a good ingot which is the Cu—Ga alloy of the present invention was obtained.

(Comparative Production Example 6)
Pure Cu and pure Ga were weighed so that the Ga concentration was 28% by mass, and using a high-frequency vacuum melting furnace (FVM-30, manufactured by Fuji Radio Industry Co., Ltd.) in an Ar atmosphere at 15 ° C./min. The temperature was raised and after confirming that the raw material had melted, the molten metal temperature was maintained at 1400 ° C. The obtained molten metal was poured into a carbon mold of 550 mm × 145 mm × 30 mm at a casting speed of 500 g / sec. At this time, the molten metal did not begin to solidify before the injection was completed. The molten metal poured into the carbon mold was cooled to 200 ° C. at a cooling rate of about 13 ° C./min to obtain an ingot. The ingot was observed with a scanning electron microscope under the same conditions as in Production Example 1 to determine the average equivalent circle diameter and the maximum equivalent circle diameter of the γ phase. The results are summarized in Table 1. Under the above production conditions, a good ingot was obtained, but the average equivalent circle diameter of the γ phase was larger than 50 μm, and the Cu—Ga alloy of the present invention could not be obtained.

(Comparative Production Example 7)
A molten metal was produced under the same conditions as in Comparative Production Example 6. This molten metal was poured into a 460 mm × 160 mm × 30 mm water-cooled copper mold at a casting speed of 500 g / sec. At this time, the molten metal did not begin to solidify before the injection was completed. The molten metal poured into the water-cooled copper mold was cooled to 50 ° C. at a cooling rate of about 100 ° C./min to obtain an ingot. The ingot was observed with a scanning electron microscope under the same conditions as in Production Example 1 to determine the average equivalent circle diameter and the maximum equivalent circle diameter of the γ phase. The results are summarized in Table 1. Under the above production conditions, a good ingot was obtained, but the average equivalent circle diameter of the γ phase was larger than 50 μm, and the Cu—Ga alloy of the present invention could not be obtained.

From the results shown in Table 1, if the melting temperature is not higher by about 300 to 500 ° C. than the melting point of the Cu—Ga alloy to be produced, the molten metal begins to solidify before the injection into the mold is completed, and a good ingot is obtained. I found out I couldn't get it.

It was also found that a Cu—Ga alloy having a smaller average equivalent circle diameter of the γ phase can be obtained by using a water-cooled copper mold than by using a carbon mold. This is probably because the cooling rate can be increased by using the water-cooled copper mold as described above.

It was also found that the average equivalent circular diameter of the γ phase increases as the melting temperature increases. This is considered to be because the cooling time becomes longer when the melting temperature is high, and the tissue grows greatly.

(Production Example 4)
An ingot was produced under the same conditions as in Production Example 1, except that a Cu—Ga alloy having a Ga concentration of 28 mass% was used instead of pure Cu and pure Ga. This ingot was observed with a scanning electron microscope under the same conditions as in Production Example 1 to determine the average equivalent circle diameter and the maximum equivalent circle diameter of the γ phase. The average equivalent circle diameter of the γ phase was 50 μm or less and the maximum circle The equivalent diameter was 200 μm or less.

(Production Example 5)
Instead of pure Cu and pure Ga, a Cu—Ga alloy having a pure Cu and Ga concentration of 32% by mass was used, and both were weighed so that the Ga concentration was 28% by mass. An ingot was produced under the conditions. This ingot was observed with a scanning electron microscope under the same conditions as in Production Example 1 to determine the average equivalent circle diameter and the maximum equivalent circle diameter of the γ phase. The average equivalent circle diameter of the γ phase was 50 μm or less and the maximum circle The equivalent diameter was 200 μm or less.

(Production Example 6)
Instead of pure Cu and pure Ga, a Cu—Ga alloy having a pure Ga and Ga concentration of 20% by mass was used, and both were weighed so that the Ga concentration was 28% by mass. An ingot was produced under the conditions. This ingot was observed with a scanning electron microscope under the same conditions as in Production Example 1 to determine the average equivalent circle diameter and the maximum equivalent circle diameter of the γ phase. The average equivalent circle diameter of the γ phase was 50 μm or less and the maximum circle The equivalent diameter was 200 μm or less.

These results are shown in Table 2 together with the results of Production Example 1.

From the results shown in Table 2, the metal materials include a combination of pure Cu and Ga pure metals, a Cu—Ga alloy only, a combination of pure Cu and Cu—Ga alloys, pure Ga metal and Cu— It was found that a Cu—Ga alloy having an average equivalent circle diameter of the γ phase of 50 μm or less and a maximum equivalent circle diameter of 200 μm or less can be obtained by any combination with the Ga alloy. From this result, even in a combination of pure Cu metal, pure Ga metal, and Cu—Ga alloy, the average equivalent circle diameter of the γ phase is 50 μm or less, and the maximum equivalent circle diameter is 200 μm or less. It is presumed that a Ga alloy can be obtained.

(Examples 1 to 3, Comparative Examples 1 to 3)
Pure Cu and pure Ga are weighed so that the Ga concentration becomes the value shown in Table 3, and using a high-frequency vacuum melting furnace (FVM-30, manufactured by Fuji Denpa Kogyo Co., Ltd.) in an Ar atmosphere at 15 ° C. / The temperature was raised at min, and after confirming that the raw material had melted, the molten metal temperature was maintained at 1200 ° C. The obtained molten metal was poured into a carbon mold of 550 mm × 145 mm × 30 mm at a casting speed shown in Table 3. At this time, the molten metal did not begin to solidify before the injection was completed. The molten metal poured into the carbon mold was cooled to 200 ° C. at a cooling rate of about 13 ° C./min to obtain an ingot of 450 mm × 13.5 mm × 28 mm. This ingot was cut into a size of about 10 mm square, mirror-polished, and the cross section was observed with a scanning electron microscope (manufactured by JEOL Co., Ltd., JSM-6380A) at a magnification of 200 times. From the obtained tissue image, the average equivalent circle diameter of the γ phase, the maximum equivalent circle diameter, and the ratio of the total area of the γ phase to the area of the tissue image (area ratio) were determined by the method described above. In Comparative Example 1, since only the β phase appeared in the tissue image and the γ phase could not be confirmed, the average equivalent circle diameter and the maximum equivalent circle diameter of the γ phase were not obtained. In Comparative Example 3, since the tissue image was composed of only the γ phase, the average equivalent circle diameter and the maximum equivalent circle diameter of the γ phase were not obtained. The results are shown in Table 3.

Moreover, it rolls on the following conditions with respect to ingots other than the ingot obtained by the comparative example 1, and the presence or absence of the crack and crack which arose in the obtained rolled sheet, ie, a sputtering target, visually, on the following references | standards evaluated. The results are shown in Table 3. In Table 3, “−” in the rolling temperature column means that rolling was not performed.

A: No cracks or cracks were observed on the rolled sheet B: Cracks were observed on the rolled sheet C: No cracks were observed on the rolled sheet, but cracks were observed D: The ingot melted during rolling [Rolling conditions]
The ingot was heated in an electric furnace at the rolling temperature shown in Table 3 for 30 minutes. For this ingot, using a rolling mill (9LCD / 500W hot two-stage rolling mill manufactured by Nippon Cross Rolling Co., Ltd.), at a rolling reduction shown in Table 3 and a roll speed of 1.0 m / sec, The rolling operation was repeated until the thickness was changed from 30 mm to 11 mm, which is the thickness of the ingot before rolling.

From the results in Table 3, the ingot having an average equivalent circle diameter of γ phase of 50 μm or less and a maximum equivalent circle diameter of 200 μm or less can be rolled, and the average equivalent circle diameter and maximum equivalent circle diameter of the γ phase can be obtained. It was found that the smaller the is, the wider the temperature range that can be rolled. In addition, as shown in Example 3 and Comparative Example 2, even if the Ga concentration is the same, the ingot produced under the condition where the casting speed is low is higher than the ingot produced under the condition where the casting speed is high. However, the average equivalent circle diameter and the maximum equivalent circle diameter of the γ phase were large, and it was not possible to obtain a rolled sheet free from cracks and cracks.

(Examples 4 to 7, Comparative Examples 4 to 5)
Pure Cu and pure Ga were weighed so that the Ga concentration would be the value shown in Table 4, and using a high-frequency vacuum melting furnace (FVM-30, manufactured by Fuji Radio Industry Co., Ltd.) in an Ar atmosphere at 15 ° C. / The temperature was raised at min and it was confirmed that the raw material had melted, and then the molten metal temperature was maintained at 1200 ° C. This molten metal was poured into a 460 mm × 160 mm × 30 mm water-cooled copper mold at the casting speed shown in Table 4. At this time, the molten metal did not begin to solidify before the injection was completed. The molten metal poured into the water-cooled copper mold was cooled to 50 ° C. at a cooling rate of about 100 ° C./min to obtain an ingot of 410 mm × 155 mm × 29 mm. This ingot was observed with a scanning electron microscope in the same manner as in Example 1. From the obtained tissue image, the average equivalent circle diameter of the γ phase, the maximum equivalent circle diameter, and the ratio of the total area of the γ phase to the area of the tissue image (area ratio) were determined by the method described above. In Comparative Example 4, since only the β phase appeared in the tissue image and the γ phase could not be confirmed, the average equivalent circle diameter and the maximum equivalent circle diameter of the γ phase were not obtained. In Comparative Example 5, since the tissue image was composed of only the γ phase, the average equivalent circle diameter and the maximum equivalent circle diameter of the γ phase were not obtained. The results are shown in Table 5.

Further, the ingots other than the ingot obtained in Comparative Example 4 were rolled under the same conditions as in Example 1, and the obtained rolled plate, that is, the presence or absence of cracks and cracks generated in the sputtering target was visually observed. Evaluation was performed according to the same criteria as in Example 1. The results are shown in Table 4. Note that “−” in the rolling temperature column of Table 4 means that rolling was not performed.

From the results shown in Table 4, even in the case of using a water-cooled copper mold, an ingot having an average equivalent circle diameter of γ phase of 50 μm or less and a maximum equivalent circle diameter of 200 μm or less can be rolled. In other words, it was found that the rolling temperature range was wider as the average equivalent circle diameter and the maximum equivalent circle diameter of the γ phase were smaller.

Unlike the case where the carbon mold is used, when the water-cooled copper mold is used, as shown in Example 6 and Example 7, when the Ga concentration is the same, the casting speed is low. There was no significant difference in the average equivalent circle diameter of the γ phase between the produced ingot and the ingot produced under a condition where the casting speed was high. Ingots produced using a water-cooled copper mold have a smaller average equivalent circle diameter and maximum equivalent circle diameter of the γ phase when the Ga concentration is the same as that of an ingot produced using a carbon mold. all right. These are considered because the water-cooled copper mold has a higher cooling rate than the carbon mold.

Also, the ingots other than the ingots obtained in Comparative Example 4 and Example 7 were rolled under the same conditions as in Example 1 except that a reduction rate different from that in Example 1 was adopted. Several types of reduction ratios to be adopted were selected, and rolling was performed for each reduction ratio. Table 5 shows the highest rolling reduction (maximum rolling reduction) at which no cracks occurred in the rolled sheet among the rolling reductions employed. “B”, “D”, and “−” in Table 5 have the same meanings as “B”, “D”, and “—” shown in Table 3, respectively.

From the results in Table 5, it was found that the Cu—Ga alloy of the present invention can be rolled at a large reduction rate of 9 to 23%. For this reason, when a Cu—Ga alloy sputtering target is produced from the Cu—Ga alloy of the present invention by rolling, high productivity can be secured.

Claims

An average circle of γ phase containing 25 to 30% by mass of Ga with a balance of Cu—Ga alloy having a Ga concentration of 30 to 35% by mass appearing in a structure image obtained by an electron microscope A Cu—Ga alloy having an equivalent diameter of 50 μm or less and a maximum equivalent circle diameter of 200 μm or less.
2. The Cu—Ga alloy according to claim 1, wherein the ratio of the total area of the γ phase to the area of the tissue image is 5 to 70%.
The Cu-Ga alloy according to claim 1 or 2, which is an alloy for producing a sputtering target.
A Cu-Ga alloy sputtering target obtained by rolling the Cu-Ga alloy according to claim 3.