Cu-Ga SPUTTERING TARGET AND PRODUCTION METHOD FOR Cu-Ga SPUTTERING TARGET

Abstract

A Cu—Ga sputtering target made of a composition containing: as metal components excluding fluorine, 5 atomic % or more and 60 atomic % or less of Ga and 0.01 atomic % or more and 5 atomic % or less of K; and the Cu balance containing inevitable impurities is provided. In the Cu—Ga sputtering target, the Cu—Ga sputtering target has a region containing Cu, Ga, K, and F, in an atomic mapping image by a wavelength separation X-ray detector.

Claims

1. A Cu—Ga sputtering target made of a composition containing: metal components excluding fluorine, which contain 5 atomic % or more and 60 atomic % or less of Ga and 0.01 atomic % or more and 5 atomic % or less of K; and a balance containing Cu and inevitable impurities, wherein the Cu—Ga sputtering target has a region containing Cu, Ga, K, and F, in an atomic mapping image by a wavelength separation X-ray detector.

2. The Cu—Ga sputtering target according to claim 1, wherein the region containing Cu, Ga, K, and F has a compound phase of: K; one of or both of Cu and Ga; and F.

3. The Cu—Ga sputtering target according to claim 1, wherein the region containing Cu, Ga, K, and F disperses in a grain boundary of a Cu—Ga matrix.

4. The Cu—Ga sputtering target according to claim 1, wherein the Cu—Ga matrix includes a KF single phase, and an abundance ratio X of the KF single phase relative to an entire amount of KF in the Cu—Ga sputtering target is 0%<X≦70%.

5. A Cu—Ga sputtering target production method for producing the Cu—Ga sputtering target according to claim 1, the method comprising the step of sintering a raw material powder by heating, wherein the raw material powder is a mixed powder, in which: a first Cu—Ga alloy powder forming a liquid phase component in the step of sintering; a KF raw material powder; and one of or both of a second Cu—Ga alloy powder not forming a liquid phase component in the step of sintering and a Cu powder, are mixed so as to obtain a composition containing: metal components excluding fluorine, which contain 5 atomic % or more and 60 atomic % or less of Ga and 0.01 atomic % or more and 5 atomic % or less of K; and a balance containing Cu and inevitable impurities, and a Cu—Ga—K—F region containing Cu, Ga, K, and F is formed by liquid phase sintering a part of the raw material powder in the step of sintering.

6. The Cu—Ga sputtering target production method according to claim 5, wherein an oxygen concentration of the first Cu—Ga alloy powder is 1000 ppm or less.

7. The Cu—Ga sputtering target production method according to claim 5, wherein an average grain size of the first Cu—Ga alloy powder in the raw material powder is in a range of 5 μm or more and 50 μm or less; and an average grain size of the KF raw material powder is in the range of 5 μm or more and 500 μm or less.

8. The Cu—Ga sputtering target production method according to claim 5, wherein the raw material powder is kept at a temperature, at which a liquid phase is formed from the first Cu—Ga alloy powder, for 15 minutes or more in the step of sintering.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0033] FIG. 1 is a flowchart showing the Cu—Ga sputtering target production method related to an embodiment of the present invention.

[0034] FIG. 2 is an example of elemental mapping of Cu, Ga, K, and F of the Cu—Ga sputtering target observed in Example of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

[0035] The Cu—Ga sputtering target and the Cu—Ga sputtering target production method, both of which are embodiments of the present invention, are explained below in reference to the attached drawings.

[0036] The Cu—Ga sputtering target related to the present embodiment is used during depositing the Cu—Ga thin film by sputtering in order to form the light-absorbing layer made of the Cu—In—Ga—Se quaternary alloy thin film in the CIGS thin film solar cell, for example.

[0037] In the Cu—Ga sputtering target related to the present embodiment, KF (potassium fluoride) is added to the Cu—Ga alloy; and the Cu—Ga sputtering target related to the present embodiment has a composition containing: as metal components excluding fluorine, 5 atomic % or more and 60 atomic % or less of Ga and 0.01 atomic % or more and 5 atomic % or less of K; and the Cu balance containing inevitable impurities.

[0038] The alkaline metal, K is included in the deposited Cu—Ga thin film by the Cu—Ga sputtering target, and the element having the effect of improving the conversion efficiency of the CIGS thin film solar cell. In the present embodiment, K is included at a relatively high amount of 0.01 atomic % or more and 5 atomic % or less.

[0039] The Cu—Ga sputtering target has the Cu—Ga matrix, the Cu—Ga—K—F region containing Cu, Ga, K, and F and the KF single phase.

[0040] The Cu—Ga—K—F region containing Cu, Ga, K, and F is formed by having: KF; and Cu and Ga, react each other. In the present embodiment, the Cu—Ga—K—F region has a compound phase of: K; one of or both of Cu and Ga; and F, and disperses in the grain boundary of the Cu—Ga matrix.

[0041] A preferable area ratio of the Cu—Ga—K—F region is 5% to 80% in the atomic mapping image by the wavelength separation X-ray detector in any cross section of the Cu—Ga sputtering target related to the present embodiment. A more preferable area ratio of the Cu—Ga—K—F region is 10% to 50%. An even more preferable area ratio of the Cu—Ga—K—F region is 20% to 30%. The area ratio of the Cu—Ga—K—F region means the area ratio of the Cu—Ga—K—F region relative to the entire area of the observed area.

[0042] In addition, in the Cu—Ga sputtering target of the present embodiment, the Cu—Ga matrix includes the KF single phase, and the abundance ratio X of the KF single phase relative to the entire amount of KF in the Cu—Ga sputtering target is set to the range of 0%<X≦70%.

[0043] The abundance ratio of the KF single phase is limited to 70% or less in order to suppress the abnormal discharge when the sputtering target includes alkaline metal, K in a relatively larger amount.

[0044] Next, the Cu—Ga sputtering target production method related to the present embodiment is explained in reference to the flowchart shown in FIG. 1.

[0045] The Cu—Ga sputtering target production method related to the present embodiment includes: the Cu—Ga alloy preparing process S01, in which the after-mentioned first and second Cu—Ga alloy powders are prepared; the mixing and crushing process S02, in which the raw material powder is obtained by mixing and crushing the first Cu—Ga alloy powder and the second Cu—Ga alloy powder, the KF raw powder, and the Cu powder; the sintering process S03, in which sintering is performed by heating the raw material powder; and the machining process S04, in which the obtained sintered material is machined, as shown in FIG. 1.

[0046] The raw material powder is the mixed powder, in which: the KF raw material powder; the first Cu—Ga alloy powder forming the liquid phase component at the sintering temperature in the sintering process (at 50° C. or more and 300° C. or less in the present embodiment); and one of or both of the second Cu—Ga alloy powder not forming the liquid phase component in the above-described sintering process and the Cu powder, are mixed.

[0047] The purity of the KF raw material powder is set to 99.9 mass % or more; and the average grain size of the KF raw material powder is set to the range of 5 μm or more and 500 μm or less.

[0048] The first Cu—Ga alloy powder is the atomized powder having the composition of: 43 atomic % or more and 66 atomic % or less of Ga; and the Cu balance containing inevitable impurities; and the average grain size of the first Cu—Ga alloy powder is set to the range of 5 μm or more and 50 μm or less.

[0049] In addition, in the first Cu—Ga alloy powder, the oxygen concentration is set to 1000 ppm or less in mass ratio. Preferably, it is set to 200 ppm or less.

[0050] The second Cu—Ga alloy powder is the atomized powder having the composition of: more than 0 atomic % and less than 43 atomic % of Ga; and the Cu balance containing inevitable impurities; and the average grain size of the second Cu—Ga alloy powder is set to the range of 5 μm or more and 50 μm or less.

[0051] In addition, in the Cu powder, the purity is set to 99.9 mass % or more; and the average grain size is set to the range of 5 μm or more and 50 μm or less.

[Cu—Ga Alloy Powder Preparation Process S01]

[0052] The above-described first and second Cu—Ga alloy powders are prepared by procedures explained below.

[0053] First, the massive form Cu raw material and Ga material are weighted to obtain a predetermined composition, and inserted in a crucible made of carbon to set in a gas atomization device. After vacuum evacuating and melting the raw material at the temperature condition of 1000° C. or more and 1200° C. or less for 1 minutes or more and 30 minutes or less, the gas atomize powder is prepared by ejecting Ar gas in the condition of 10 kgf/cm.sup.2 or more and 50 kgf/cm.sup.2 or less of the injection gas pressure, while the melt is dropped form the nozzle having the diameter of 1 mm or more and 3 mm or less. After cooling, the obtained atomized powder is subjected to classification with the sieve of 90-500 μm; and the first Cu—Ga alloy powder and the second Cu—Ga alloy powder having predetermined grain sizes are obtained.

[0054] In producing the first Cu—Ga alloy powder, the oxygen concentration is reduced to 1000 ppm or less, preferably to 200 rpm or less, by setting the degree of vacuum to 1 Pa or less during vacuum evacuating.

[0055] In addition, depending on the composition ratio between Cu and Ga, it is possible that the melt reaches to the chamber before solidifying to be powder due to too high ejection temperature. In this case, it is preferable that atomization is performed at the ejection temperature 100° C. to 400° C. lower than the hot retention temperature.

[Mixing and Crushing Process S02]

[0056] Next, the above-described KF raw material powder, the first Cu—Ga alloy powder, the second Cu—Ga alloy powders, and the Cu powder are weighted to obtain a predetermined composition. Then, they are mixed and crushed by using the mixing pulverizer to obtain the raw material powder. When the ball mill is used as the mixing pulverizer, it is preferable that 5 kg of zirconia made balls of 45 mm, and 3 kg of the raw material powder (the KF raw material powder, the first Cu—Ga alloy powder, the second Cu—Ga alloy powders, and the Cu powder) in total are placed in a 10-L pot filled an inert gas such as Ar, for example; and the ball mill is operated at 85 rpm for 16 hours. In addition, when the Henschel mill is used as the mixing pulverizer, it is preferable that the Henschel mill is operated at the rotation speed of 2800 rpm for 5 minutes in inert gas atmosphere such as Ar, for example. Mixing-based mixing pulverizer such as the V type mixer, the rocking mixer, and the like is not preferable since it is possible that crushing of the KF raw material powder becomes insufficient.

[Sintering Process S03]

[0057] Next, sintering of the raw material powder (the mixed powder) obtained as described above is performed in vacuum, inert gas atmosphere, or reducing atmosphere. It is preferable to set the sintering temperature in the sintering process depending on the melting temperature Tm of the producing Cu—Ga alloy. Specifically, it is preferable that the sintering temperature is set to the range of (Tm-70°) C. or more and (Tm-20°) C. or less. In addition, it is preferable to retain the raw material powder in the temperature range of 250° C. or more and 300° C. or less corresponding to the temperature, in which the first Cu—Ga alloy powder is melted for the liquid phase to be formed (the liquid phase temperature of the first Cu—Ga alloy powder) in the temperature profile during sintering, for 15 minutes or more.

[0058] In this sintering process S03, a part of the first Cu—Ga alloy powder is melted for the liquid phase to be formed. By having the liquid phase and the KF raw material powder react each other, the Cu—Ga—K—F region containing Cu, Ga, K, and F is formed.

[0059] In the sintering process S03, pressureless sintering; hot pressing; or hot isostatic pressing can be used as a sintering method.

[0060] When pressureless sintering is used, it is advantageous to use carbon monoxide (CO), hydrogen, ammonia cracking gas, or the like in sintering as reducing gas. In addition, it is preferable that the content of the reducing gas in the atmosphere is 1 volume % or more.

[0061] In addition, when hot pressing or hot isostatic pressing is used, it is preferable that the pressure condition is set to the range of 10 MPa or more and 60 MPa or less, since the pressure condition influences on the density of the sintered material. Pressing can be done before the beginning of heating. Alternatively, pressing can be done after reaching to a constant temperature.

[Machining Process S04]

[0062] By performing cutting work or grinding work on the sintered material obtained in the sintering process S03, it is machined into a sputtering target in a predetermined shape. Since KF dissolve in water, it is preferable to use dry method not using coolant liquid in the machining process S04.

[0063] By following the above-described processes, the Cu—Ga sputtering target of the present embodiment is produced. This Cu—Ga sputtering target is used after bonded on a backing plate, which is made of Cu, SUS (stainless), or other metal (for example, Mo), using In as soldering material.

[0064] According to the Cu—Ga sputtering target of the present embodiment configured as described above, the Cu—Ga film containing the alkaline metal, K can be deposited, since KF (potassium fluoride) is added to the Cu—Ga alloy; and the Cu—Ga sputtering target has the composition containing: as metal components excluding fluorine, 5 atomic % or more and 60 atomic % or less of Ga and 0.01 atomic % or more and 5 atomic % or less of K; and the Cu balance containing inevitable impurities. Thus, a high quality CIGS thin film solar cell having excellent conversion efficiency can be constructed.

[0065] In addition, in the Cu—Ga sputtering target of the present embodiment, at least a part of the alkaline metal, K is included in the form of the Cu—Ga—K—F region containing Cu, Ga, K, and F. Thus, the abnormal discharge during sputtering can be suppressed; and the Cu—Ga film can be deposited stably.

[0066] In the Cu—Ga sputtering target production method of the present embodiment, the liquid phase is produced by melting at least part of the first Cu—Ga alloy powder in the sintering process S03. Thus, the Cu—Ga alloy in the liquid phase and the KF raw material powder react each other; and the Cu—Ga—K—F region containing Cu, Ga, K, and F can be formed. Thus, as described above, the Cu—Ga sputtering target, which is capable of depositing stably the Cu—Ga film in which the alkaline metal, K is uniformly dispersed, can be obtained.

[0067] In addition, in the present embodiment, the oxygen concentration of the first Cu—Ga alloy powder is limited to 1000 ppm, preferably to 200 ppm. Thus, at least a part of the first Cu—Ga alloy powder can be melted reliably for the liquid phase to be produced; and the Cu—Ga—K—F region containing Cu, Ga, K, and F can be formed reliably.

[0068] Moreover, in the present embodiment, the raw material powder is retained at the temperature, in which the liquid phase is produced from the first Cu—Ga alloy powder in the temperature profile in the sintering process S03, for 15 minutes or more. Thus, time for the liquid phase produced from the first Cu—Ga alloy powder and the KF raw material powder contacting each other to react can be secured; and the Cu—Ga—K—F region containing Cu, Ga, K, and F can be formed reliably.

[0069] In addition, in the present embodiment, the average grain size of the first Cu—Ga alloy powder in the raw material powder is set to the range of 5 μm or more and 50 μm or less; and the average grain size of the KF raw material powder is set to the range of 5 μm or more and 500 μm or less. Thus, the Cu—Ga—K—F region containing Cu, Ga, K, and F can be formed by having the first Cu—Ga alloy powder and the KF raw material powder react each other reliably.

[0070] Embodiments of the present invention are explained above. However, the present invention is not limited by the explanation, and can be modified suitably to the extent not deviating from the scope of the present invention.

[0071] For example, in the present embodiment, the raw material powder is explained as the mixed powder, in which the first Cu—Ga alloy powder; the KF raw material powder; the second Cu—Ga alloy powder; and the Cu powder. The present invention is not limited by the description. In terms of the second Cu—Ga alloy powder and the Cu powder, the raw material powder may include at least one of the second Cu—Ga alloy powder and the Cu powder; and it can be configured suitably depending on the composition of the Cu—Ga sputtering needed.

EXAMPLES

[0072] Test results in evaluating the effects of the Cu—Ga sputtering target related to the present invention are explained below.

[0073] [Cu—Ga Sputtering Target]

[0074] First, the Cu—Ga alloy powder, the Cu powder and the KF raw material powder, all of which were ingredients of the raw material powder, were prepared. In Examples 1-14 of the present invention and Comparative Example 5, the first Cu—Ga alloy powder, which produced the liquid phase in the sintering process, was used. The method of producing the first Cu—Ga alloy powder is shown in Table 1.

[0075] The Cu—Ga sputtering targets having the compositions shown in Table 4 were produced by setting the blending composition of the raw material powder as shown in Table 2; and following the production conditions shown in Table 3.

[0076] Texture observation was performed on the obtained Cu—Ga sputtering targets; and occurrence of the abnormal discharge was evaluated as explained below. The evaluation results are shown in Table 4.

[Identification of the Cu—Ga—K—F Region and the KF Single Phase]

[0077] The atomic mapping image can be obtained by the wavelength separation X-ray detector. In the present examples, the atomic mapping image of the cross section of the Cu—Ga sputtering target was obtained by the method explained below by using the electron probe micro analyzer (EPMA) device.

[0078] Cross section polisher processing (CP processing) was performed on the processed surface of the produced Cu—Ga sputtering target; and the electron mapping image of Cu, Ga, K, and F was obtained with the electron probe micro analyzer (EPMA) device (Model JXA-8500F manufactured by JOEL Ltd.). The region in which only K and F existed was defined as the KF single phase. The region in which Cu, Ga, K, and F were detected was defined as the Cu—Ga—K—F region. In terms of judging detection of Cu, Ga, K, and F, the element was regarded as being detected when: the Cu content was 5 mass % or more in the case of Cu; the Ga content was 5 mass % or more in the case of Ga; the K content was 5 mass % or more in the case of K; and the F content was 5 mass % or more in the case of F, in the quantitative map image created by using ZAF correction method. In creating the quantitative map, C, O, F, K, Cu, and Ga were chosen as constituent elements. An example of the element mapping image is shown in FIG. 2. The location, in which the Cu—Ga—K—F region existed, is shown in Table 4. When the Cu—Ga—K—F existed: in the grain boundary of Cu—Ga phases as shown in FIG. 2; or in both of the grain and the grain boundary of Cu—Ga phases, the location of the Cu—Ga—K—F region was defined as “in grain boundary.” When the Cu—Ga—K—F region only existed in the grain of the Cu—Ga phase, the location of the Cu—Ga—K—F was defined as “in grain.”

[0079] The measurement condition by EPMA device was as described below.

[0080] Measurement magnification: 500-times

[0081] Pixel size: 1 μm

[0082] Sampling time: 10 m sec

[0083] Electric current: 50 nA

[0084] Acceleration voltage: 15 kV

[0085] Characteristic X-ray used in mapping: C: Kα-ray, 0: Kα-ray, F: Kα-ray, K: Kα-ray, Cu: Kα-ray, Ga: Lα-ray

[0086] Software for creating map: JXA-8500F vol. 42

[Identification of the Compound Phase of: K; One of or Both of Cu and Ga; and F]

[0087] The presence or absence of the compound phase of: K; one of or both of Cu and Ga; and F, as the Cu—Ga—K—F region was evaluated by the procedure described below.

[0088] Cross section polisher processing (CP processing) was performed on the processed surface of the produced Cu—Ga sputtering target; the spectrum of the 2p orbital, which corresponded to the spectrum from 280 to 305 eV, was measured after performing surface etching by Ar for 1 minute with the X-ray photoelectron spectrometer (XPS) (manufactured by Physical Electronics). When there was a detected peak from 296 to 297 eV in the above-described K spectrum, it was defined as “Present.” When there was no peak from 296 to 297 eV in the above-described K spectrum, it was defined as “Absent.” Results are shown in Table 4.

[0089] The measurement condition by XPS device was as described below.

[0090] Radiation source: Al Kα-ray, 350 W

[0091] Measurement area: φ800 μm

[0092] Path energy: 187.85 eV

[0093] Measurement interval: 0.8 eV/step

[0094] Photoelectron extraction angle with respect to the sample surface: 45 deg

[Abundance Ratio of the KF Single Phase]

[0095] The abundance ratio of the KF single phase was calculated from the equation shown below after performing image processing on the mapping image of K among the above-described element mapping and obtaining each area of the Cu—Ga—K—F region and the KF single phase. As an image processing software, WinRoof (manufactured by Mitani Co.) can be used, for example.

(area of the KF single phase)/((area of the KF single phase)+(area of Cu—Ga—K—F region))×100

[Measurement of Uniformity of K in the Sputtered Film]

[0096] Deposition by sputtering was performed using the produced Cu—Ga sputtering target in the condition described below. A sputtered film was deposited in 1 μm thickness on the alkaline-free glass substrate having the dimension of 100 mm×100 mm: by using the DC magnetron sputtering device and Ar gas as the sputtering gas, in the condition of: 50 sccm of the flow rate; 0.67 Pa of the pressure; and 2 W/cm.sup.2 of the input electrical power.

[0097] The obtained films were analyzed by the fluorescence X-ray analyzer (XRF). Measurements of Cu, Ga, and K were performed on five locations on the coordinates of (−20 mm, +20 mm); (+20 mm, +20 mm); (−20 mm, −20 mm); (+20 mm, −20 mm); and (0 mm, 0 mm), the center of the substrate being the location of (X=0, Y=0). For the measurements, Primus II manufactured by Rigaku Co. was used. The value, in which the minimum value among the five points was subtracted from the maximum value among the five points, was calculated on the obtained values of K content.

[Abnormal Discharge During Sputtering]

[0098] By using the produced Cu—Ga sputtering target, deposition by sputtering was performed in the condition described below. Sputtering was performed for 30 minutes under two different electrical power settings, one of which was the input electrical power was 2 W/cm.sup.2 (low electrical power setting), and another of which was the input electrical power was 5 W/cm.sup.2 (high electrical power setting): by using the DC magnetron sputtering device and Ar gas as the sputtering gas, in the condition of: 50 sccm of the flow rate; and 0.67 Pa of the pressure. The number of occurrence of the abnormal discharge was counted by the arcing count function provided on the DC power supply.

[0099] In the present examples, as the electrical power supply, RPG-50 (manufactured by mks Co.) was used, for example.

TABLE-US-00001 TABLE 1 Raw material powder First Cu—Ga alloy powder Second Cu—Ga alloy producing the liquid powder not producing component the liquid component Cu powder KF powder Oxygen Average Average Average Average Ga concen- grain Blending Ga grain Blending grain Blending grain Blending content tration size ratio content size ratio size ratio size ratio (at %) (wt %) (μm) (%) (at %) (μm) (%) (μm) (%) (μm) (%) Example of  1 50 0.008  7.8 50.0 20  7.6 15.0 53.6 34.6 6 0.4 the present  2 60 0.013 10.3 41.7 — — — 25.1 56.8 112 1.5 invention  3 60 0.007 35.7 33.3 — — — 53.6 66.5 6 0.1  4 45 0.011 45.7 22.2 — — — 53.6 76.6 53 1.2  5 50 0.028 10.2 70.0 — — — 25.1 28.5 112 1.5  6 60 0.057 15.8 66.7 — — — 25.1 28.9 230 4.5  7 50 0.076 20.5 60.0 — — — 25.1 39.0 12 1.0  8 60 0.008  5.2 55.0 — — — 53.6 44.6 112 0.4  9 50 0.010 30.7 50.0 — — — 20.6 45.5 230 4.5 10 60 0.018 38.7 55.0 10 20.4 30.0 25.0 13.5 20 1.5 11 60 0.015 20.5 48.3 — — — 20.6 45.7 430 5.9 12 60 0.120 10.5 46.7 — — — 20.6 48.9 112 4.5 13 60 0.009 57.8 50.0 — — — 53.6 49.3 53 0.7 Comparative  1 — — — — 25 25.3 80.0 25.0 18.5 230 1.5 Example  2 — — — — 30 23.5 93.3 20.6 2.2 112 4.5  3 — — — — 35 19.3 85.7 53.6 13.5 53 0.7  4 — — — — 40 13.2 87.5 20.6 2.1 757 10.4  5 50 0.014 26.7 70.0 — — — 20.6 19.6 757 10.4

TABLE-US-00002 TABLE 2 Production condition of the first Cu—Ga alloy powder producing the liquid phase component Atomizing condition Cu Ga Ultimate Melting Retention content content vacuum temperature time (at %) (at %) (Pa) (° C. ) (min) Example of  1 50 50 0.03 1200  5 the present  2 40 60 0.06 1100 10 invention  3 40 60 0.01 1050 10  4 55 45 0.05 1100  5  5 50 50 0.12 1200  5  6 40 60 0.35 1050 10  7 50 50 0.89 1100  5  8 40 60 0.01 1050  5  9 50 50 0.03 1200  5 10 40 60 0.08 1100  5 11 40 60 0.05 1050 10 12 40 60 100    1100  5 13 40 60 0.03 1200  5 Comparative  1 The first Cu—Ga alloy powder producing the liquid Example phase component was not used  2 The first Cu—Ga alloy powder producing the liquid phase component was not used  3 The first Cu—Ga alloy powder producing the liquid phase component was not used  4 The first Cu—Ga alloy powder producing the liquid phase component was not used  5 50 50 0.05 1050 10

TABLE-US-00003 TABLE 3 Target production condition Sintering condition Reaction Retention Sintering Retention Pressure temperature time temperature time Method Atmosphere (MPa) (° C. ) (mm) (° C. ) (h) Example of  1 HIP Vacuum 60 290  5 770 1 the present  2 Hot pressing Vacuum 20 320 10 780 3 invention  3 HIP Vacuum 50 330 15 830 3  4 HIP Vacuum 60 270 10 920 2  5 Hot pressing Vacuum 18 — — 720 1  6 Hot pressing Vacuum 20 — — 500 5  7 Hot pressing Vacuum 20 — — 720 3  8 Pressureless H.sub.2 — 280 30 710 5 sintering  9 Pressureless CO — 280  5 780 10  sintering 10 HIP Vacuum 60 330 15 680 2 11 Hot pressing Vacuum 20 260  5 770 3 12 HIP Vacuum 50 260  3 770 2 13 Pressureless H.sub.2 — 300 30 720 5 sintering Comparative  1 Hot pressing Vacuum 20 — — 780 2 Example  2 HIP Vacuum 50 290  3 770 2  3 Pressureless H.sub.2 — 300 30 720 5 sintering  4 Hot pressing Vacuum 25 — — 710 3  5 Hot pressing Vacuum 25 270  3 710 3

TABLE-US-00004 TABLE 4 Composition of metal component Cu—Ga KF single Number of occurrence of (at %) matrix Cu—Ga—K—F region phase the abnormal discharge Cu and Average Presence or Abun- Uniformity Low High inevi- grain Presence absence of dance of K electrical electrical table im- size or Existing the compound ratio max-min power power Ga K purities μM absence location phase % wt % count/30 min count/30 min Example of  1 28 0.3 balance 5.7 present in grain present 19 0.03 0 0 the present boundary invention  2 25 1.0 balance 8.5 present in grain present 53 0.02 0 3 boundary  3 20 0.1 balance 32.2 present in grain present 9 0.01 0 0  4 10 0.8 balance 42.6 present in grain present 48 0.02 0 2 boundary  5 35 1.0 balance 8.4 present in grain present 64 0.03 2 10 boundary  6 40 3.0 balance 9.5 present in grain present 71 0.04 14 22 boundary  7 30 0.7 balance 14.2 present in grain present 89 0.03 6 8 boundary  8 33 0.3 balance 3.6 present in grain present 5 0.03 3 9 boundary  9 25 3.0 balance 25.3 present in grain present 21 0.04 4 14 boundary 10 36 1.0 balance 34.1 present in grain present 72 0.02 2 7 boundary 11 29 4.0 balance 14.6 present in grain present 65 0.05 16 24 boundary 12 28 3.0 balance 5.7 present in grain absent 90 0.04 8 25 boundary 13 30 0.5 balance 52.6 present in grain present 87 0.04 2 19 boundary Comparative  1 20 1.0 balance 8.3 absent — absent 100 0.10 53 142 Example  2 28 3.0 balance 5.7 absent — absent 100 0.04 78 235  3 30 0.5 balance 52.6 absent — absent 100 0.04 33 109  4 35 7.0 balance 22.3 absent — absent 100 0.12 85 shut down  5 35 7.0 balance 22.3 absent — absent 100 0.05 53 shut down

[0100] In Comparative Examples 1-5, in which the Cu—Ga—K—F region did not exist, the number of occurrence of the abnormal discharge was high; and sputtering was not performed stably. Particularly, in Comparative Examples 4 and 5, in which the grain size of the KF raw material powder was too large; and the content of the K component was too high, the sputtering device was shut down during high-power sputtering. In addition, in Comparative Examples 1, 4, and 5, uniformity of the K component in the deposited Cu—Ga film was deteriorated.

[0101] Contrary to that, in Examples 1-13 of the present invention, in which the Cu—Ga—K—F region do exist, the number of occurrence of the abnormal discharge was low; and sputtering was performed stably. In addition, it was confirmed that uniformity of the K component in the deposited Cu—Ga film was improved.

INDUSTRIAL APPLICABILITY

[0102] It is possible to produce the CIGS solar cell having high energy conversion efficiency with high production efficiency.

REFERENCE SIGNS LIST

[0103] S01: Cu—Ga alloy powder preparing process [0104] S02: Mixing and crushing process [0105] S03: Sintering process [0106] S04: Machining process