WO2013031381A1 - Cu-Ga合金スパッタリングターゲット及びその製造方法 - Google Patents
Cu-Ga合金スパッタリングターゲット及びその製造方法 Download PDFInfo
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- WO2013031381A1 WO2013031381A1 PCT/JP2012/067280 JP2012067280W WO2013031381A1 WO 2013031381 A1 WO2013031381 A1 WO 2013031381A1 JP 2012067280 W JP2012067280 W JP 2012067280W WO 2013031381 A1 WO2013031381 A1 WO 2013031381A1
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- C—CHEMISTRY; METALLURGY
- C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
- C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
- C23C14/00—Coating by vacuum evaporation, by sputtering or by ion implantation of the coating forming material
- C23C14/22—Coating by vacuum evaporation, by sputtering or by ion implantation of the coating forming material characterised by the process of coating
- C23C14/34—Sputtering
- C23C14/3407—Cathode assembly for sputtering apparatus, e.g. Target
- C23C14/3414—Metallurgical or chemical aspects of target preparation, e.g. casting, powder metallurgy
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- C—CHEMISTRY; METALLURGY
- C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
- C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
- C23C14/00—Coating by vacuum evaporation, by sputtering or by ion implantation of the coating forming material
- C23C14/22—Coating by vacuum evaporation, by sputtering or by ion implantation of the coating forming material characterised by the process of coating
- C23C14/34—Sputtering
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B22—CASTING; POWDER METALLURGY
- B22D—CASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
- B22D11/00—Continuous casting of metals, i.e. casting in indefinite lengths
- B22D11/001—Continuous casting of metals, i.e. casting in indefinite lengths of specific alloys
- B22D11/004—Copper alloys
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B22—CASTING; POWDER METALLURGY
- B22D—CASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
- B22D11/00—Continuous casting of metals, i.e. casting in indefinite lengths
- B22D11/04—Continuous casting of metals, i.e. casting in indefinite lengths into open-ended moulds
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C9/00—Alloys based on copper
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22F—CHANGING THE PHYSICAL STRUCTURE OF NON-FERROUS METALS AND NON-FERROUS ALLOYS
- C22F1/00—Changing the physical structure of non-ferrous metals or alloys by heat treatment or by hot or cold working
- C22F1/08—Changing the physical structure of non-ferrous metals or alloys by heat treatment or by hot or cold working of copper or alloys based thereon
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22F—CHANGING THE PHYSICAL STRUCTURE OF NON-FERROUS METALS AND NON-FERROUS ALLOYS
- C22F1/00—Changing the physical structure of non-ferrous metals or alloys by heat treatment or by hot or cold working
Definitions
- the present invention relates to a Cu—Ga alloy sputtering target used for 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, and its production. Regarding the method.
- CIGS Cu—In—Ga—Se
- the outline process of 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.
- a method for producing a Cu—Ga target there are a dissolution method and a powder method.
- a Cu—Ga target manufactured by a melting method is said to have relatively little impurity contamination, but has many drawbacks. For example, since the cooling rate cannot be increased, the compositional segregation is large, and the composition of the film produced by the sputtering method gradually changes.
- 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.
- the brittleness increases and cracking easily occurs, and cracking and chipping are likely to occur during processing of the target or during sputtering, which also causes an increase in cost due to a decrease in yield.
- Patent Document 1 relating to the Cu—Ga target by the dissolution method
- no analysis results or the like are shown.
- there is a description that there was no brittleness and no cracks there is no description of processing conditions and sputtering conditions, and the contents are unclear.
- the upper limit of the Ga concentration range is only up to 30% by weight, and there is no description regarding characteristics including brittleness and cracks in a Ga high concentration region beyond this.
- targets produced by the powder method generally have problems such as low sintering density and high impurity concentration.
- Patent Document 2 relating to a Cu—Ga target describes a sintered body target.
- brittleness in which cracking and chipping are likely 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.
- a major problem of the Cu—Ga sputtering target produced by the soot powder method is that the process is complicated, the quality of the produced sintered body is not always good, and the production cost 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.
- Patent Document 3 As a conventional technique, there is, for example, Patent Document 3.
- a technique is described in which a copper alloy to which high-purity copper and a small amount of 0.04 to 0.15 wt% of titanium or 0.014 to 0.15 wt% of zinc are added is processed into a target by continuous casting. ing.
- Such an alloy is easy to cast and process, and is not applicable to the production of a difficult-to-process Cu—Ga alloy target in which the gallium addition amount exceeds 29 at%.
- Patent Document 4 discloses a technique in which high-purity copper is continuously cast into a rod shape so that there is no casting defect, and this is rolled into a sputtering target. Similarly, it is easy to cast and process, and is not applicable to the production of a difficult-to-process Cu—Ga alloy target in which the gallium addition amount exceeds 29 at%.
- Patent Document 5 a single crystal target sputtering target is manufactured by adding 0.1 to 3.0% by weight of a material selected from 24 elements such as Ag and Au to aluminum. Are listed. However, this is also easy to cast and process, and is not applicable to the manufacture of difficult-to-process Cu—Ga alloy targets in which the gallium addition amount exceeds 29 at%. Patent Documents 3 to 5 show examples of manufacturing using a continuous casting method, but all are limited to materials that are easy to cast and process, and are difficult to process Cu—Ga alloy targets. It can be said that there is no disclosure that can solve the problems existing in the manufacture of
- JP 2000-73163 A JP 2008-138232 A JP-A-5-31424 JP-A-2005-330591 Japanese Patent Laid-Open No. 7-300667
- a Cu—Ga alloy has a brittle ⁇ phase single phase structure when the Ga composition is 29 at% or more. Therefore, even if a target is produced by casting, subsequent processes such as rolling and forging cannot be performed, and the cast structure remains as it is. Therefore, it is a requirement that the sputtering target has a cast structure. In order to obtain a sputtering target having this cast structure and a higher quality target than a sintered compact target, it is important that the crystal grains are small and aligned. Such a target has good sputtering characteristics and can form a sputtered film with better quality.
- the present invention provides a target having a cast structure having a small crystal grain size and uniform by solidifying continuously under solidification conditions of a certain cooling rate or higher.
- the present inventors have conducted intensive research and found that a CuGa alloy sputtering target having an adjusted crystal grain size can be obtained by a continuous casting method, thereby completing the present invention.
- the present invention provides the following inventions. 1) A melted and cast plate-like Cu—Ga alloy sputtering target composed of 29 to 42.6 at% Ga, the balance being Cu and inevitable impurities, and an average crystal of the center plane parallel to the sputtering surface from the sputtering surface A Cu—Ga alloy sputtering target having a particle size of 3 mm or less and a cross-sectional structure of the target having a columnar structure grown in the direction of the sputtering surface.
- the target raw material is melted in a crucible, and this molten metal is poured into a mold equipped with a water-cooled probe to continuously produce a cast body made of a Cu—Ga alloy, which is further machined to obtain Cu—
- a method for producing a Ga alloy target wherein the solidification rate from the melting point to 400 ° C. of the casting is controlled to 380 to 1000 ° C./min, and the structure of the casting is A method for producing a Cu—Ga alloy sputtering target comprising Ga of 29 to 42.6 at%, the balance being Cu and unavoidable impurities, characterized in that it has a columnar structure grown on the substrate.
- the present invention it is possible to obtain a homogeneous Cu—Ga alloy film with less generation of particles by sputtering using a Cu—Ga alloy target having small crystal grains and a uniform cast structure.
- 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.
- the Cu—Ga alloy sputtering target of the present invention is a melted / cast Cu—Ga alloy sputtering target in which Ga is 29 to 42.6 at%, and the balance is Cu and inevitable impurities.
- the target for sintered products is a relative density of 95% or more.
- 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 almost 100%, and as a result, it has an effect of suppressing generation of particles due to the difference in sputtering. This is one of the major advantages of castings.
- the Ga content is required from the request for the formation of a Cu—Ga alloy sputtered film, which is required when manufacturing a CIGS solar cell, but within the range of 29 to 42.6 at%, the ⁇ phase A single-phase cast structure can be obtained. Under conditions outside this range, a heterogeneous phase occurs, and a uniform structure of the cast structure cannot be obtained. From the above, the additive amount of Ga is in the above range.
- the average crystal grain size of the sputtering surface (the surface of the target viewed from the sputtering direction) is 3 mm or less.
- a sputtering surface having a structure with a fine crystal grain size is effective for forming a uniform film.
- This average crystal grain size can be achieved by controlling the drawing speed, but the average crystal grain size can be 2 mm or less, and the average crystal grain size can be 1 mm or less.
- the target of the present invention has a columnar structure in which the cross-sectional structure grows from the sputtering surface toward the center plane parallel to the sputtering surface. This is one of the major features of the present invention.
- the crystal grows in a columnar shape from the wall surface of the mold toward the inside. . Furthermore, many of them grow in a columnar shape in the vertical direction. As a result, the cross-sectional structure of the target becomes a columnar structure grown in the direction of the center plane parallel to the sputtering surface from the sputtering surface.
- the average diameter of the columnar crystals is 3 mm or less.
- the sputter surface has an average crystal grain size of 3 mm or less.
- the average diameter of the columnar crystals exceeds 3 mm, the width and length of the columnar crystals are close to 1: 1 and cannot be said to be columnar crystals.
- coarse particles are generated in the casting target, and some of them become columnar crystals and some become spheroidized particles, which are non-uniform and sparsely generated in the thickness direction. Therefore, it is not preferable. In this sense, it is necessary to average crystal grain size of the sputtering surface and 3mm or less.
- impurities in the Cu—Ga alloy sputtering target include P, S, Fe, Ni, and Ag.
- the content of each of these impurities is preferably less than 10 wtppm. These can be adjusted at the raw material stage. This is a preferable requirement for improving the characteristics of the CIGS solar cell.
- the content of gas components C, O, N, and H is 300 wtppm or less in total. This is achieved by degassing the molten Cu-Ga alloy and taking measures to prevent air contamination in the casting stage (for example, selection of a sealing material for the mold and refractory material and introduction of argon gas or nitrogen gas in the sealing portion). it can. Similar to the above, this is a preferable requirement for improving the characteristics of the CIGS solar cell.
- the Cu—Ga alloy sputtering target of the present invention can be limited to the requirement that the target structure is limited to a single phase structure of ⁇ phase.
- a columnar structure grown in a direction toward the center plane parallel to the sputtering surface can be formed from both wide surfaces of the target (one surface becomes a sputtering surface), and in this case as well, many of them are in the vertical direction. It can be made into a columnar structure that has grown.
- the Cu—Ga alloy sputtering target can be a target having a cast structure manufactured by continuous casting.
- the target raw material was melted in a crucible, and this molten metal was equipped with a water-cooled probe.
- the present invention provides a method for producing a Cu—Ga alloy target by pouring molten metal into a mold to continuously produce a cast body made of a Cu—Ga alloy and further machining it.
- the mold can be appropriately selected depending on a desired target shape such as a rectangle, a column, or a cylinder.
- the solidification rate from the melting point to 400 ° C. of the cast body is controlled to 380 to 1000 ° C./min, so that the structure of the cast body has a columnar structure grown in the mold inner wall direction.
- the average crystal grain size of the sputter surface is 3 mm or less and the cross-sectional structure of the target grows from the sputter surface toward the center plane parallel to the sputter surface.
- the cast body can be more easily manufactured by casting using a continuous casting apparatus, and further by intermittently pulling the cast body from the mold.
- the content of each impurity of P, S, Fe, Ni, and Ag can be set to 10 wtppm or less and further to 5 wtppm or less, respectively.
- the contents of the gas components C, O, N, and H can be set to 300 wtppm or less in total, and the target structure can be a ⁇ -phase single-phase structure.
- a cast body having a cross-sectional width of 50 mm to 320 mm and a thickness of 5 mm to 30 mm is extracted from the mold, and machined and surface-polished. This manufacturing condition is arbitrary but preferable.
- the compositional deviation greatly changes the characteristics of the light absorption layer and the CIGS solar cell, but the Cu—Ga alloy sputtering target of the present invention. Such a composition shift is not observed at all when the film is formed by using. This is one of the major advantages of the cast product compared to the sintered product.
- FIG. 1 is a sectional view of a typical continuous casting apparatus used in the present invention. Moreover, the principal part enlarged view (sectional drawing) is shown in FIG. 1 and 2 show a horizontal continuous casting method, a vertical continuous casting method can be used. As shown in FIG. 1 and FIG. 2, a Cu—Ga alloy melt whose components are adjusted is introduced into the crucible. As the crucible, a graphite crucible is usually used, but other ceramic crucible materials may be used.
- the crucible is surrounded by a refractory material, and in this refractory material, a mold (part), a heating device that heats the crucible, and nitrogen gas introduction to prevent air from entering from the seal between the mold and the refractory material There is a department.
- a heating device By introducing the nitrogen gas, the nitrogen gas is also supplied to the molten metal in the mold, and the molten metal is bubbled. By this bubbling of the molten metal, the gas component in the molten metal is removed, and the gas component can be effectively reduced.
- a resistance heating device heating element
- an induction heating device can also be used.
- a water-cooled probe is placed inside the mold so that the mold can be cooled.
- a dummy bar is introduced into the casting. It is preferable to use a pure copper dummy bar as the dummy bar.
- the gap between the dummy bar and the mold has a structure capable of introducing nitrogen gas. The molten Cu—Ga alloy comes into contact with this dummy bar to be welded and solidified, and at the same time, the dummy bar is pulled out from the mold, and at the same time, the solidified Cu—Ga alloy is pulled out from the mold.
- a slab (Cu—Ga alloy cast) is drawn using a pinch roller disposed in front.
- This intermittent drawing is effective in reducing impurities. This is presumably because impurities contained in the Cu—Ga alloy are discharged to the molten metal side when the molten metal is solidified.
- This is the same principle as that of the zone melting method (zone melting method), which is one of the high purity methods.
- Example 1 First, using a continuous casting apparatus as shown in FIG. 1, 20 kg of a copper (Cu: purity 4N) raw material was placed in a carbon crucible, and the inside of the crucible was placed in a nitrogen gas atmosphere and heated to 1250 ° C. This high-temperature heating is for welding the dummy bar and the Cu—Ga alloy melt. Next, the additive element Ga (purity: 4N) was adjusted to a composition ratio of Ga concentration of 29 at% and introduced into the heating crucible. The heating of the crucible, using a resistance heating device (graphite elements). The melting crucible had a shape of 140 mm ⁇ ⁇ 400 mm ⁇ , the mold was made of graphite, and the cast lump was a 65 mmw ⁇ 12 mmt plate, which was continuously cast.
- Cu copper
- purity 4N purity 4N
- the molten metal temperature is lowered to 950 ° C., and drawing is started when the molten metal temperature and the mold temperature are stabilized.
- FIG. 1 since a dummy bar is inserted at the front end of the mold, the solidified slab is drawn by pulling out the dummy bar.
- the drawing pattern was repeated by driving for 0.5 seconds and stopping for 2.5 seconds, the frequency was changed, and the drawing speed was 30 mm / min.
- the relationship between the drawing speed of the slab and the cooling rate is shown in FIG.
- the drawing speed (mm / min) and the cooling speed (° C / min) are in a proportional relationship, and the cooling speed increases as the drawing speed (mm / min) is increased.
- a water-cooled probe is inserted into the mold. From the molten metal side, 30mm, 50mm, 70mm, 90mm, 110mm and 20mm each, 5 points by thermocouple, temperature to about half of the mold Measurement was performed. As a result of the measurement, a temperature gradient of about 130 ° C. was provided every 20 mm. The results are shown in Table 1. Table 1 also shows the amount of Ga added and the amounts of C, O, N, and H (wtppm) as gas components.
- FIG. 3 shows the relationship between the drawing speed of the slab and the cooling rate.
- FIG. 4 is a diagram showing a surface micrograph when the drawing speed is changed. When the drawing speed of Example 1 is relatively fast, 30 mm / min, the surface of the slab is machined (surface polished). FIG. 4 shows a micrograph of the surface obtained by etching the polished surface with nitric acid. The average crystal grain size of the target surface shown on the left side of the center of FIG. 4 was 3 mm or less, and most was 1 mm or less.
- FIG. 5 shows a photomicrograph of the surface obtained by further etching the cross section parallel to the drawing direction of the slab, that is, the polished surface of the target after machining (surface polishing) with nitric acid.
- the columnar crystals are curved along the drawing direction of the slab.
- the degree thereof is small, so that a structure with an average crystal grain size of 3 mm or less is always obtained on the surface of the target. It is not a thing.
- Sputtering using a Cu—Ga alloy target having a small crystal grain and a uniform casting structure as described above has an excellent effect that a uniform Cu—Ga alloy film can be obtained with less generation of particles.
- Example 2 is a case where the drawing speed is higher than that of Example 1, that is, 50 mm / min, and other manufacturing conditions are the same as those of Example 1.
- the surface of the slab is machined (surface polished) to be a target, and a micrograph of the surface obtained by etching the target polished surface with nitric acid is shown in FIG.
- the average crystal grain size of the target surface of Example 2 shown on the right side of the center of FIG. 4 was 2 mm or less, and most was 1 mm or less.
- FIG. 5 shows a photomicrograph of the surface obtained by further etching the cross section parallel to the drawing direction of the slab, that is, the polished surface of the target after machining (surface polishing) with nitric acid.
- the columnar crystals are slightly curved from the surface of the slab, which is the surface of the target, toward the center plane parallel to the sputter surface, but in a substantially vertical direction. Is observed.
- a structure having an average crystal grain size of 3 mm or less was always obtained.
- Sputtering using a Cu—Ga alloy target having a small crystal grain and a uniform casting structure as described above has an excellent effect that a uniform Cu—Ga alloy film can be obtained with less generation of particles.
- Example 3 is a case where the drawing speed is higher than that of Example 2, that is, 92 mm / min, and other manufacturing conditions are the same as those of Example 1 and Example 2.
- the surface of the slab is machined (surface polished) to be a target, and a micrograph of the surface obtained by etching the target polished surface with nitric acid is shown in FIG.
- the average crystal grain size of the target surface of Example 3 shown on the right side of the center of FIG. 4 was 1 mm or less.
- FIG. 5 shows a photomicrograph of the surface obtained by further etching the cross section parallel to the drawing direction of the slab, that is, the polished surface of the target after machining (surface polishing) with nitric acid.
- the columnar crystals are substantially vertical from the surface of the slab, which is the surface of the target, toward the center plane parallel to the sputtering surface.
- a structure having an average crystal grain size of 1 mm or less was always obtained.
- Sputtering using a Cu—Ga alloy target having a small crystal grain and a uniform casting structure as described above has an excellent effect that a uniform Cu—Ga alloy film can be obtained with less generation of particles.
- Example 4 is a case where the drawing speed is higher than that of Example 3, that is, 159 mm / min, and other manufacturing conditions are the same as those of Example 1, Example 2 and Example 3.
- the surface of the slab is machined (surface polished) to be a target, and a micrograph of the surface obtained by etching the target polished surface with nitric acid is shown in FIG.
- the average crystal grain size of the target surface of Example 4 shown on the right side of the center of FIG. 4 was 1 mm or less.
- FIG. 5 shows a photomicrograph of the surface obtained by further etching the cross section parallel to the drawing direction of the slab, that is, the polished surface of the target after machining (surface polishing) with nitric acid.
- the sixth photograph from the top in FIG. 5 it is observed that the columnar crystals are in a substantially vertical direction from the surface of the slab toward the center plane parallel to the sputtering surface.
- the surface of the target always mean crystal grain size was obtained following tissue 1 mm.
- Sputtering using a Cu—Ga alloy target having a small crystal grain and a uniform casting structure as described above has an excellent effect that a uniform Cu—Ga alloy film can be obtained with less generation of particles.
- Comparative Example 1 is a case where the drawing speed is slower than that of Example 1, that is, 10 mm / min, and other manufacturing conditions are the same as in Example 1.
- the surface of the slab is machined (surface polished) to be a target, and a micrograph of the surface obtained by etching the target polished surface with nitric acid is shown in FIG.
- the average crystal grain size on the target surface of Comparative Example 1 shown on the upper left side of FIG. 4 exceeded 3 mm, and the grain sizes were uneven.
- FIG. 5 shows a photomicrograph of the surface obtained by further etching the cross section parallel to the drawing direction of the slab, that is, the polished surface of the target after machining (surface polishing) with nitric acid.
- the crystal is greatly curved (flowing) from the surface of the slab toward the center plane parallel to the sputter surface.
- the cooling rate is slow, especially in the interior of the slab, since solidification is slow compared to the surface (surface contacting the mold), so that the initial precipitation It is considered that the columnar crystals are inclined (curved) because precipitation is continuously delayed.
- the shape of the crystal appearing on the surface of the slab reflects an inclined shape (curved shape), and the cross section of the crystal does not become a grain shape, and is considered to be uneven and coarse.
- an average crystal grain size exceeded 3 mm, and a structure with irregular shapes was obtained.
- Comparative Example 2 is a case where the drawing speed is slightly faster than Comparative Example 1, that is, 20 mm / min. Other manufacturing conditions are the same as in Comparative Example 1.
- the surface of the slab is machined (surface polished) to be a target, and a micrograph of the surface obtained by etching the target polished surface with nitric acid is shown in FIG.
- the average crystal grain size of the target surface of Comparative Example 2 shown on the upper right side of FIG. 4 exceeded 3 mm, and the grain sizes were uneven.
- FIG. 5 shows a photomicrograph of the surface obtained by further etching the cross section parallel to the drawing direction of the slab, that is, the polished surface of the target after machining (surface polishing) with nitric acid.
- the crystal is greatly curved (flowing) from the surface of the slab toward the center plane parallel to the sputtering surface.
- an average crystal grain size exceeded 3 mm, and a structure with irregular shapes was obtained.
- the melted and cast Cu—Ga alloy sputtering target composed of 29 to 42.6 at% Ga, the remainder being Cu and inevitable impurities has an average crystal grain size of 3 mm on the sputtering surface.
- the cross-sectional structure of the target has a columnar structure grown in the direction of the center plane parallel to the sputter surface from the sputter surface to reduce the generation of particles and form a homogeneous Cu-Ga alloy film. It can be seen that it has an important role.
- Example 5 As the main impurities contained in the Cu raw material, when impurities are contained at a high concentration shown in Table 2, that is, P: 2.8 wtppm, S: 3.9 wtppm, Fe: 1. An example is shown in which impurities of 3 wtppm, Ni: 0.63 wtppm, and Ag: 8.6 wtppm are contained.
- the gas components are the same as in Example 4, that is, C: 30 wtppm, O: 30 wtppm, N: ⁇ 10 wtppm, and H ⁇ 10 wtppm.
- the continuous casting method of Example 5 the same method as in Example 4 was used.
- a Cu—Ga alloy target having a small crystal grain equivalent to that of Example 4 and a uniform cast structure could be obtained.
- the impurity which is a raw material did not affect the cast structure.
- Example 5 when the amount of impurities produced by continuous casting was measured, P: 0.33 wtppm, S: 2.6 wtppm, Fe: 0.5 wtppm, Ni: 0.21 wtppm, Ag: 1.3 wtppm A great reduction effect was obtained.
- the casting target of Cu—Ga alloy manufactured by continuous casting has a feature that an effect of reducing impurities can be obtained. As described above, this is considered to be because impurities contained in the Cu—Ga alloy are discharged to the molten metal side when the molten metal is solidified. This is considered to be because impurities are reduced by the same principle as that of the zone melting method (zone melting method), which is one of the high purity methods.
- a 4NCu raw material and a 4NGa raw material were prepared in order to produce a Cu—Ga alloy in which Ga is 35 at% and the balance is Cu.
- These raw materials include P: 2.8 wtppm, S: 3.9 wtppm, Fe: 1.3 wtppm, Ni: 0.63 wtppm, Ag: 8.6 wtppm as impurities, and C: 30 wtppm, O: as gas components. It contained 30 wtppm, N: ⁇ 10 wtppm, H ⁇ 10 wtppm.
- Example 2 Using the same continuous casting apparatus as in Example 1, the crucible was heated to 1250 ° C, the Cu and Ga raw materials were added, and the molten metal temperature was lowered to 915 ° C. The drawing of the piece started. The drawing speed was 30 mm / min. Other manufacturing conditions are the same as those in Example 1, Example 2, and Example 3. The surface of the slab is machined (surface polished) to be a target. A micrograph of the surface of the target polished surface etched with nitric acid is shown in FIG. The average crystal grain size on the target surface of Example 6 was 1 mm or less.
- FIG. 7 shows a photomicrograph of the surface obtained by further etching the cross section parallel to the drawing direction of the slab, that is, the polished surface of the target after machining (surface polishing) with nitric acid.
- the columnar crystals are in a substantially vertical direction from the surface of the slab toward the center plane parallel to the sputtering surface.
- a structure having an average crystal grain size of 1 mm or less was always obtained.
- Example 6 when the amount of impurities produced by continuous casting was measured, P: 0.24 wtppm, S: 2.3 wtppm, Fe: 0.45 wtppm, Ni: 0.17 wtppm, Ag: 1.5 wtppm was gotten. Further, gas impurities C: 20 wtppm, O: 30 wtppm, N ⁇ 10 wtppm, and H ⁇ 10 wtppm. The results are shown in Table 3. As described above, the casting target of Cu—Ga alloy manufactured by continuous casting has a feature that an effect of reducing impurities can be obtained. As described above, this is considered to be because impurities contained in the Cu—Ga alloy are discharged to the molten metal side when the molten metal is solidified.
- a 4NCu raw material and a 4NGa raw material were prepared in order to produce a Cu—Ga alloy in which Ga is 35 at% and the balance is Cu.
- These raw materials include P: 2.8 wtppm, S: 3.9 wtppm, Fe: 1.3 wtppm, Ni: 0.63 wtppm, Ag: 8.6 wtppm as impurities, and C: 30 wtppm, O: as gas components. It contained 30 wtppm, N: ⁇ 10 wtppm, H ⁇ 10 wtppm.
- Example 7 Using the same continuous casting apparatus as in Example 1, the crucible was heated to 1250 ° C, the Cu and Ga raw materials were added, and the molten metal temperature was lowered to 915 ° C. The drawing of the piece started. The drawing speed was 150 mm / min. Other manufacturing conditions are the same as those in Example 1, Example 2, and Example 3. The surface of the slab is machined (surface polished) to be a target, and a micrograph of the surface obtained by etching the target polished surface with nitric acid is shown in FIG. The average crystal grain size of the target surface of Example 7 was 1 mm or less.
- FIG. 9 shows a micrograph of the surface parallel to the drawing direction of the slab, that is, the polished surface when the target after machining (surface polishing) is further etched with nitric acid. As shown in this photograph, it is observed that the columnar crystals are in a substantially vertical direction toward the surface of the slab. And on the surface of the target, a structure having an average crystal grain size of 1 mm or less was always obtained.
- Example 7 when the amount of impurities produced by continuous casting was measured, P: 0.38 wtppm, S: 2.5 wtppm, Fe: 0.53 wtppm, Ni: 0.19 wtppm, Ag: 1.4 wtppm was gotten. Further, gas impurities C: 20 wtppm, O: 30 wtppm, N ⁇ 10 wtppm, and H ⁇ 10 wtppm. The results are shown in Table 3. As described above, the casting target of Cu—Ga alloy manufactured by continuous casting has a feature that an effect of reducing impurities can be obtained. As described above, this is considered to be because impurities contained in the Cu—Ga alloy are discharged to the molten metal side when the molten metal is solidified.
- a 4NCu raw material and a 4NGa raw material were prepared in order to produce a Cu—Ga alloy having Ga 40 at% and the balance being Cu.
- These raw materials include P: 2.8 wtppm, S: 3.9 wtppm, Fe: 1.3 wtppm, Ni: 0.63 wtppm, Ag: 8.6 wtppm as impurities, and C: 30 wtppm, O: as gas components. It contained 30 wtppm, N: ⁇ 10 wtppm, H ⁇ 10 wtppm.
- Example 2 Using the same continuous casting apparatus as in Example 1, the crucible was heated to 1250 ° C, the Cu and Ga raw materials were added, and the molten metal temperature was lowered to 860 ° C. The drawing of the piece started. The drawing speed was 30 mm / min. Other manufacturing conditions are the same as those in Example 1, Example 2, and Example 3. The surface of the slab is machined (surface polished) to be a target. A micrograph of the surface of the target polished surface etched with nitric acid is shown in FIG. The average crystal grain size of the target surface of Example 8 was 1 mm or less.
- FIG. 11 shows a micrograph of a surface parallel to the drawing direction of the slab, that is, a surface obtained by further etching the polished surface with a target after machining (surface polishing) with nitric acid.
- a target after machining surface polishing
- nitric acid nitric acid
- Example 8 when the amount of impurities produced by continuous casting was measured, P: 0.33 wtppm, S: 2.4 wtppm, Fe: 0.38 wtppm, Ni: 0.21 wtppm, Ag: 1.8 wtppm was gotten. Further, the gas impurities were C: 20 wtppm, O: 40 wtppm, N ⁇ 10 wtppm, and H ⁇ 10 wtppm. The results are shown in Table 3. As described above, the casting target of Cu—Ga alloy manufactured by continuous casting has a feature that an effect of reducing impurities can be obtained. As described above, this is considered to be because impurities contained in the Cu—Ga alloy are discharged to the molten metal side when the molten metal is solidified.
- Example 9 In the ninth embodiment, a 4NCu raw material and a 4NGa raw material were prepared in order to manufacture a Cu—Ga alloy having Ga 40 at% and the balance being Cu.
- These raw materials include P: 2.8 wtppm, S: 3.9 wtppm, Fe: 1.3 wtppm, Ni: 0.63 wtppm, Ag: 8.6 wtppm as impurities, and C: 30 wtppm, O: as gas components. It contained 30 wtppm, N: ⁇ 10 wtppm, H ⁇ 10 wtppm.
- Example 1 Using the same continuous casting apparatus as in Example 1, the crucible was heated to 1250 ° C, the Cu and Ga raw materials were added, and the molten metal temperature was lowered to 860 ° C. The drawing of the piece started. The drawing speed was 150 mm / min. Other manufacturing conditions are the same as those in Example 1, Example 2, and Example 3. The surface of the slab is machined (surface polished) to be a target. A micrograph of the surface of the target polished surface etched with nitric acid is shown in FIG. The average crystal grain size of the target surface of Example 9 was 1 mm or less.
- FIG. 13 shows a photomicrograph of the surface parallel to the drawing direction of the slab, that is, the polished surface when the target after machining (surface polishing) is further etched with nitric acid. As shown in this photograph, it is observed that the columnar crystals are in a substantially vertical direction from the surface of the slab toward the center plane parallel to the sputtering surface. And on the surface of the target, a structure having an average crystal grain size of 1 mm or less was always obtained.
- Example 9 the amount of impurities produced by continuous casting was measured.
- P 0.41 wtppm
- S 2.8 wtppm
- Fe 0.48 wtppm
- Ni 0.24 wtppm
- Ag 2.1 wtppm
- the gas impurities were C: 30 wtppm
- O 30 wtppm
- N ⁇ 10 wtppm and H ⁇ 10 wtppm.
- Table 3 As described above, the casting target of Cu—Ga alloy manufactured by continuous casting has a feature that an effect of reducing impurities can be obtained. As described above, this is considered to be because impurities contained in the Cu—Ga alloy are discharged to the molten metal side when the molten metal is solidified.
- the present invention it is possible to obtain a homogeneous Cu—Ga alloy film with less generation of particles by sputtering using a Cu—Ga alloy target having a small crystal grain and a uniform cast structure.
- 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, it is useful for a solar cell for suppressing a reduction in conversion efficiency of a CIGS solar cell.
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Abstract
Description
Cu-Gaターゲットの製造方法としては、溶解法と粉末法がある。一般的には、溶解法で製造されたCu-Gaターゲットは、不純物汚染が比較的少ないとされているが、欠点も多い。例えば、冷却速度を大きくできないので組成偏析が大きく、スパッタ法によって作製される膜の組成が、次第に変化してきてしまう。
更に、高Ga濃度になるほど脆性が増加して割れ易くなり、ターゲットへの加工中やスパッタ時に割れや欠けが発生し易く、これも歩留まり低下によるコストアップの原因となる。
更に、実施例ではGa濃度範囲の上限が30重量%までの結果しかなく、これ以上のGa高濃度領域での脆性や割れを含めて、特性に関する記述は全くない。
密度が低いターゲットは、当然ながら異常放電やパーティクル発生があり、スパッタ膜表面にパーティクル等の異形物があると、その後のCIGS膜特性にも悪影響を与え、最終的にはCIGS太陽電池の変換効率の大きな低下を招く虞が多分にある。
上記特許文献3~5については、連続鋳造法を用いて製造する例を示しているが、いずれも鋳造及び加工が容易である材料に限定されたもので、難加工性のCu-Ga合金ターゲットの製造に存在する問題を解決できる開示はないと言える。
1)Gaが29~42.6at%、残部がCu及び不可避的不純物からなる溶解・鋳造した板状のCu-Ga合金スパッタリングターゲットであって、スパッタ表面からスパッタ面に平行な中心面の平均結晶粒径が3mm以下であり、ターゲットの断面組織がスパッタ表面の方向に成長した柱状組織を有することを特徴とするCu-Ga合金スパッタリングターゲット。
3)ガス成分であるC、O、N、Hの含有量が、合計で300wtppm以下であることを特徴とする上記1又は2記載のCu-Ga合金スパッタリングターゲット。
4)ターゲットの組織が、γ相の単相組織であることを特徴とする上記1~3のいずれか一項に記載のCu-Ga合金スパッタリングターゲット。
6)連続鋳造により製造したターゲットであることを特徴とする上記1~5のいずれか一項に記載のCu-Ga合金スパッタリングターゲット。
9)鋳型からの引抜き速度を50mm/min~150mm/minとすることを特徴とする上記7記載のCu-Ga合金スパッタリングターゲットの製造方法。
11)鋳造体を鋳型から間欠的に引抜くことを特徴とする上記7~10のいずれか一項記載のCu-Ga合金スパッタリングターゲットの製造方法。
13)ガス成分であるC、O、N、Hの含有量を、合計で300wtppm以下とすることを特徴とする上記7~12のいずれか一項記載のCu-Ga合金スパッタリングターゲットの製造方法。
一般に、焼結品は相対密度を95%以上にすることが目標である。相対密度が低いと、スパッタ中の内部空孔の表出時に空孔周辺を起点とするスプラッシュや異常放電による膜へのパーティクル発生や表面凹凸化の進展が早期に進行して、表面突起(ノジュール)を起点とする異常放電等が起き易くなるからである。
鋳造品は、ほぼ相対密度100%を達成することができ、この結果、スパッタリングの差異のパーティクルの発生を抑制できる効果を有する。これは鋳造品の大きな利点の一つと言える。
この平均結晶粒径は、引抜き速度を制御することにより達成できるが、平均結晶粒径を2mm以下に、さらには平均結晶粒径を1mm以下とすることができる。
また、本願発明のターゲットは、断面組織がスパッタ表面からスパッタ面に平行な中心面の方向に成長した柱状組織を有する。これは、本願発明の大きな特徴の一つである。
この結果、鋳造ターゲットの中で粗大粒子が発生し、その形状は、あるものは柱状晶に、あるものは球状化した粒子となって、不均一化し、また厚み方向に複数個まばらに発生するので好ましくない。この意味からも、スパッタ表面の平均結晶粒径を3mm以下とすることが必要となる。
また、ターゲットの双方の広幅面(一方の面はスパッタ面となる)から、スパッタ表面に平行な中心面に向う方向に成長した柱状組織とすることができ、この場合も、その多くを垂直方向に成長した柱状組織とすることができる。さらに、Cu-Ga合金スパッタリングターゲットは、連続鋳造により製造した鋳造組織を持つターゲットとすることができる。
またガス成分であるC、O、N、Hの含有量を、合計で300wtppm以下とすること、さらに、ターゲットの組織を、γ相の単相組織とすることができる。
間歇的に引出す場合には、このピンチローラーの駆動を制御することにより行うことができる。この間歇的な引出しは、不純物の低減化に有効である。それは、溶湯の凝固の際にCu-Ga合金に含まれる不純物が溶湯側へ吐き出されるためであると考えられる。これは、高純度化の手法の1つであるゾーンメルティング法(帯域溶融法)と同じ原理である。
まず、図1に示すような連続鋳造装置を使用し、銅(Cu:純度4N)原料20kgをカーボン製坩堝に入れ、坩堝内を窒素ガス雰囲気にし、1250°Cまで加熱した。この高温の加熱は、ダミーバーとCu-Ga合金溶湯を溶着させるためである。
次に、添加元素であるGa(純度:4N)をGa濃度が29at%の組成比となるように調整して、加熱坩堝に導入した。坩堝の加熱には、抵抗加熱装置(グラファイトエレメント)を使用した。溶解坩堝の形状は、140mmφ×400mmφであり、鋳型の材質はグラファイト製で、鋳造塊の形状は65mmw×12mmtの板とし、連続鋳造した。
引抜きパターンは、0.5秒駆動、2.5秒停止の繰り返しで行い、周波数を変化させ、引抜き速度を30mm/minとした。鋳片の引抜き速度と冷却速度の関係を図3に示す。図3に示すように、引抜き速度(mm/min)と冷却速度(°C/min)は比例関係にあり、引抜き速度(mm/min)を上げると冷却速度も上昇する。
図5の上から3番目の写真に示すように、鋳片の引抜き方向に沿って柱状晶が湾曲しているのが観察される。しかしながら、この柱状晶は中心面付近で湾曲しても、その程度が小さいため、ターゲットの表面では、常に平均結晶粒径は3mm以下の組織が得られる組織になるので、スパッタリング時に特に問題となるものではない。
このように結晶粒が小さく、揃った鋳造組織を持つCu-Ga合金ターゲットを用いてスパッタリングすることにより、パーティクルの発生が少なく、均質なCu-Ga系合金膜を得ることができるという優れた効果を有する。
実施例2は、実施例1よりもさらに速い引抜き速度、すなわち50mm/minとした場合であり、他の製造条件は、実施例1と同様にした場合である。鋳片の表面は、機械加工(表面研磨)してターゲットにするが、このターゲット研磨面を硝酸でエッチングした表面の顕微鏡写真を図4に示す。図4の中央右側に示す本実施例2のターゲット表面の平均結晶粒径は2mm以下であり、殆どは1mm以下であった。
このように結晶粒が小さく、揃った鋳造組織を持つCu-Ga合金ターゲットを用いてスパッタリングすることにより、パーティクルの発生が少なく、均質なCu-Ga系合金膜を得ることができるという優れた効果を有する。
実施例3は、実施例2よりもさらに速い引抜き速度、すなわち92mm/minとした場合であり、他の製造条件は、実施例1及び実施例2と同様にした場合である。鋳片の表面は、機械加工(表面研磨)してターゲットにするが、このターゲット研磨面を硝酸でエッチングした表面の顕微鏡写真を図4に示す。図4の中央右側に示す本実施例3のターゲット表面の平均結晶粒径は1mm以下であった。
図5の上から5番目の写真に示すように、ターゲットの表面となる鋳片の表面からスパッタ面に平行な中心面に向かって柱状晶が、ほぼ垂直方向になっているのが観察される。そして、ターゲットの表面では、常に平均結晶粒径は1mm以下の組織が得られた。
このように結晶粒が小さく、揃った鋳造組織を持つCu-Ga合金ターゲットを用いてスパッタリングすることにより、パーティクルの発生が少なく、均質なCu-Ga系合金膜を得ることができるという優れた効果を有する。
実施例4は、実施例3よりもさらに速い引抜き速度、すなわち159mm/minとした場合であり、他の製造条件は、実施例1、実施例2及び実施例3と同様にした場合である。鋳片の表面は、機械加工(表面研磨)してターゲットにするが、このターゲット研磨面を硝酸でエッチングした表面の顕微鏡写真を図4に示す。図4の中央右側に示す本実施例4のターゲット表面の平均結晶粒径は1mm以下であった。
図5の上から6番目の写真に示すように、鋳片の表面からスパッタ面に平行な中心面に向かって柱状晶がほぼ垂直方向になっているのが観察される。そして、ターゲットの表面では、常に平均結晶粒径は1mm以下の組織が得られた。
このように結晶粒が小さく、揃った鋳造組織を持つCu-Ga合金ターゲットを用いてスパッタリングすることにより、パーティクルの発生が少なく、均質なCu-Ga系合金膜を得ることができるという優れた効果を有する。
比較例1は、実施例1よりも遅い引抜き速度、すなわち10mm/minとした場合であり、他の製造条件は、実施例1と同様にした場合である。鋳片の表面は、機械加工(表面研磨)してターゲットにするが、このターゲット研磨面を硝酸でエッチングした表面の顕微鏡写真を図4に示す。図4の上左側に示す本比較例1のターゲット表面の平均結晶粒径は3mmを超え、その粒径は不揃いであった。
図3に示すように、連続鋳造では、引抜き速度が遅い場合には、冷却速度が遅くなる、特に鋳片の内部では表面(鋳型に接触する面)に比べ凝固が遅くなるので、初期の析出した柱状晶に対して、継続して析出が遅延するために傾斜状(湾曲状)になるものと考えられる。このため、鋳片の表面に現れる結晶の形状は、傾斜状(湾曲状)の形状が反映され、結晶の横断面が粒形とはならず、不揃かつ粗大化するものと考えられる。
この結果、上記鋳片から得られたターゲットの表面では、中心面に近づくと、平均結晶粒径は3mmを超え、形状が不揃いなった組織が得られた。このように結晶粒が不揃いな鋳造組織を持つCu-Ga合金ターゲットを用いてスパッタリングすると、パーティクルの発生が多くなり、不均質なCu-Ga系合金膜となる問題が発生した。
比較例2は、比較例1よりもやや速くした引抜き速度、すなわち20mm/minとした場合であり、他の製造条件は、比較例1と同様にした場合である。鋳片の表面は、機械加工(表面研磨)してターゲットにするが、このターゲット研磨面を硝酸でエッチングした表面の顕微鏡写真を図4に示す。図4の上右側に示す本比較例2のターゲット表面の平均結晶粒径は3mmを超え、その粒径は不揃いであった。その流れは比較例1よりも若干改善はされているが、本願発明の目的を達成することはできなかった。
この結果、ターゲットの表面では、中心面に近づくと、平均結晶粒径は3mmを超え、形状が不揃いなった組織が得られた。このように結晶粒が不揃いな鋳造組織を持つCu-Ga合金ターゲットを用いてスパッタリングすると、パーティクルの発生が多くなり、不均質なCu-Ga系合金膜となる問題が発生した。
次に、本実施5では、Cu原料に含有する主な不純物として、表2に示す高濃度に不純物が含有された場合、すなわち、P:2.8wtppm、S:3.9wtppm、Fe:1.3wtppm、Ni:0.63wtppm、Ag:8.6wtppmの不純物が含有された例を示す。なお、ガス成分は、実施例4と同一、すなわちC:30wtppm、O:30wtppm、N:<10wtppm、H<10wtppmの場合である。
本実施例5の連続鋳造法では、実施例4と同一の方法で実施した。この結果、実施例4と同等の結晶粒が小さく、揃った鋳造組織を持つCu-Ga合金ターゲットを得ることができた。このように、原料である不純物は、鋳造組織に影響を与えることはなかった。
次に、本実施3では、Cu原料に含有する主な不純物として、表2に示す高濃度に不純物が含有された場合、すなわち、P:2.8wtppm、S:3.9wtppm、Fe:1.3wtppm、Ni:0.63wtppm、Ag:8.6wtppmの不純物が含有された例を示す。
本比較例3の鋳造法では、置き注ぎ法、すなわち通常の鋳造法により、実施例4と同一寸法のグラファイト製鋳型に鋳造したものである。
この実施例5と比較例3の対比から、連続鋳造によって製造したCu-Ga合金の鋳造ターゲットは、鋳造組織の改良だけでなく、不純物の低減効果が得られるという効果が顕著であることが確認できた。
本実施6では、Ga35at%、残部がCuであるCu-Ga合金を製造するために、4NCu原料及び4NGa原料を準備した。これらの原料には、不純物として、P:2.8wtppm、S:3.9wtppm、Fe:1.3wtppm、Ni:0.63wtppm、Ag:8.6wtppm、並びにガス成分として、C:30wtppm、O:30wtppm、N:<10wtppm、H<10wtppmを含有していた。
他の製造条件は、実施例1、実施例2及び実施例3と同様にした場合である。鋳片の表面は、機械加工(表面研磨)してターゲットにするが、このターゲット研磨面を、硝酸でエッチングした表面の顕微鏡写真を図6に示す。本実施例6のターゲット表面の平均結晶粒径は1mm以下であった。
この写真に示すように、鋳片の表面からスパッタ面に平行な中心面に向かって柱状晶が、ほぼ垂直方向になっているのが観察される。そして、ターゲットの表面では、常に平均結晶粒径は1mm以下の組織が得られた。
以上に示すように、連続鋳造によって製造したCu-Ga合金の鋳造ターゲットは、不純物の低減効果が得られるという特徴を持つ。これは、上記に述べたように、溶湯の凝固の際にCu-Ga合金に含まれる不純物が溶湯側へ吐き出されるためであると考えられる。
本実施7では、Ga35at%、残部がCuであるCu-Ga合金を製造するために、4NCu原料及び4NGa原料を準備した。これらの原料には、不純物として、P:2.8wtppm、S:3.9wtppm、Fe:1.3wtppm、Ni:0.63wtppm、Ag:8.6wtppm、並びにガス成分として、C:30wtppm、O:30wtppm、N:<10wtppm、H<10wtppmを含有していた。
他の製造条件は、実施例1、実施例2及び実施例3と同様にした場合である。鋳片の表面は、機械加工(表面研磨)してターゲットにするが、このターゲット研磨面を、硝酸でエッチングした表面の顕微鏡写真を図8に示す。本実施例7のターゲット表面の平均結晶粒径は1mm以下であった。
この写真に示すように、鋳片の表面に向かって柱状晶が、ターゲット表面に向かって、ほぼ垂直方向になっているのが観察される。そして、ターゲットの表面では、常に平均結晶粒径は1mm以下の組織が得られた。
以上に示すように、連続鋳造によって製造したCu-Ga合金の鋳造ターゲットは、不純物の低減効果が得られるという特徴を持つ。これは、上記に述べたように、溶湯の凝固の際にCu-Ga合金に含まれる不純物が溶湯側へ吐き出されるためであると考えられる。
本実施8では、Ga40at%、残部がCuであるCu-Ga合金を製造するために、4NCu原料及び4NGa原料を準備した。これらの原料には、不純物として、P:2.8wtppm、S:3.9wtppm、Fe:1.3wtppm、Ni:0.63wtppm、Ag:8.6wtppm、並びにガス成分として、C:30wtppm、O:30wtppm、N:<10wtppm、H<10wtppmを含有していた。
他の製造条件は、実施例1、実施例2及び実施例3と同様にした場合である。鋳片の表面は、機械加工(表面研磨)してターゲットにするが、このターゲット研磨面を、硝酸でエッチングした表面の顕微鏡写真を図10に示す。本実施例8のターゲット表面の平均結晶粒径は1mm以下であった。
以上に示すように、連続鋳造によって製造したCu-Ga合金の鋳造ターゲットは、不純物の低減効果が得られるという特徴を持つ。これは、上記に述べたように、溶湯の凝固の際にCu-Ga合金に含まれる不純物が溶湯側へ吐き出されるためであると考えられる。
本実施9では、Ga40at%、残部がCuであるCu-Ga合金を製造するために、4NCu原料及び4NGa原料を準備した。これらの原料には、不純物として、P:2.8wtppm、S:3.9wtppm、Fe:1.3wtppm、Ni:0.63wtppm、Ag:8.6wtppm、並びにガス成分として、C:30wtppm、O:30wtppm、N:<10wtppm、H<10wtppmを含有していた。
他の製造条件は、実施例1、実施例2及び実施例3と同様にした場合である。鋳片の表面は、機械加工(表面研磨)してターゲットにするが、このターゲット研磨面を、硝酸でエッチングした表面の顕微鏡写真を図12に示す。本実施例9のターゲット表面の平均結晶粒径は1mm以下であった。
以上に示すように、連続鋳造によって製造したCu-Ga合金の鋳造ターゲットは、不純物の低減効果が得られるという特徴を持つ。これは、上記に述べたように、溶湯の凝固の際にCu-Ga合金に含まれる不純物が溶湯側へ吐き出されるためであると考えられる。
Claims (14)
- Gaが29~42.6at%、残部がCu及び不可避的不純物からなる溶解・鋳造したCu-Ga合金スパッタリングターゲットであって、スパッタ表面の平均結晶粒径が3mm以下であり、ターゲットの断面組織が、スパッタ表面からスパッタ面に平行な中心面の方向に成長した柱状組織を有することを特徴とするCu-Ga合金スパッタリングターゲット。
- P、S、Fe、Ni、Agの各不純物の含有量が、それぞれ10wtppm未満であること特徴とする請求項1記載のCu-Ga合金スパッタリングターゲット。
- ガス成分であるC、O、N、Hの含有量が、合計で300wtppm以下であることを特徴とする請求項1又は2記載のCu-Ga合金スパッタリングターゲット。
- ターゲットの組織が、γ相の単相組織であることを特徴とする請求項1~3のいずれか一項に記載のCu-Ga合金スパッタリングターゲット。
- ターゲット双方の広幅面(一方の面はスパッタ面となる)から、スパッタ表面に平行な中心面に向かって垂直方向に成長した柱状組織を有することを特徴とする請求項1~4のいずれか一項に記載のCu-Ga合金スパッタリングターゲット。
- 連続鋳造により製造したターゲットであることを特徴とする請求項1~5のいずれか一項に記載のCu-Ga合金スパッタリングターゲット。
- ターゲット原料を坩堝内で溶解し、この溶湯を、水冷プローブを備えた鋳型に注湯して連続的にCu-Ga合金からなる鋳造体を製造し、これをさらに機械加工してCu-Ga合金ターゲットを製造する方法であって、前記鋳造体が融点から400°Cに至るまでの凝固速度を380~1000°C/minに制御し、当該鋳造体の組織が鋳型内壁から鋳造体の内部の方向に成長した柱状の組織とすることを特徴とするGaが29~42.6at%、残部がCu及び不可避的不純物からなるCu-Ga合金スパッタリングターゲットの製造方法。
- スパッタ表面の平均結晶粒径が3mm以下であり、ターゲットの断面組織がスパッタ表面からスパッタ面に平行な中心面に向かって成長した柱状組織を有することを特徴とする請求項7記載のCu-Ga合金スパッタリングターゲットの製造方法。
- 鋳型からの引抜き速度を30mm/min~150mm/minとすることを特徴とする請求項7記載のCu-Ga合金スパッタリングターゲットの製造方法。
- 連続鋳造装置を用いて鋳造することを特徴とする請求項7又は8記載のCu-Ga合金スパッタリングターゲットの製造方法。
- 鋳造体を鋳型から間欠的に引抜くことを特徴とする請求項7~10のいずれか一項記載のCu-Ga合金スパッタリングターゲットの製造方法。
- P、S、Fe、Ni、Agの各不純物の含有量を、それぞれ10wtppm以下とすること特徴とする請求項7~11のいずれか一項記載のCu-Ga合金スパッタリングターゲットの製造方法。
- ガス成分であるC、O、N、Hの含有量を、合計で300wtppm以下とすることを特徴とする請求項7~12のいずれか一項記載のCu-Ga合金スパッタリングターゲットの製造方法。
- ターゲットの組織を、γ相の単相組織とすることを特徴とする請求項7~13のいずれか一項記載のCu-Ga合金スパッタリングターゲットの製造方法。
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KR1020137020332A KR20130094352A (ko) | 2011-08-29 | 2012-07-06 | Cu-Ga 합금 스퍼터링 타깃 및 그 제조 방법 |
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US14/004,289 US20140001039A1 (en) | 2011-08-29 | 2012-07-06 | Cu-Ga Alloy Sputtering Target and Method for Producing Same |
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JPWO2013031381A1 (ja) | 2015-03-23 |
EP2684978A4 (en) | 2015-01-14 |
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CN103502505B (zh) | 2015-09-30 |
EP2684978A1 (en) | 2014-01-15 |
US20140001039A1 (en) | 2014-01-02 |
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