JP2012201948A - Cu-Ga ALLOY SPUTTERING TARGET - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a Cu-Ga alloy sputtering target which has high Ga concentration and in which cracks, abnormal discharge, and generation of particles are suppressed.SOLUTION: The Cu-Ga alloy sputtering target has Ga concentration of 30-45 mass%, an average crystal grain size of 20 μm or less, an area ratio of the group comprising a γphase, a γphase, a γphase, and a γ phase of 95 area% or more, porosity of 1% or less, and three-point bending strength of 200 MPa or more.

Description

  The present invention relates to a Cu—Ga alloy sputtering target used for forming a light absorption layer of a CIGS (Cu—In—Ga—Se quaternary alloy) solar cell.

  In recent years, photovoltaic power generation has attracted attention as one of clean energy. Although crystalline Si solar cells are mainly used, CIGS (Cu—In—Ga—Se quaternary alloy) solar cells with high conversion efficiency are attracting attention because of supply and cost problems. Yes.

  The CIGS solar cell has, as a basic structure, a Mo electrode layer to be a back electrode formed on a soda lime glass substrate and a CIGS film (Cu-In--) to be a light absorption layer formed on the Mo electrode layer. Ga-Se film or Cu-In-Ga-S-Se film), a buffer layer made of ZnS, CdS, etc. formed on the light absorption layer, and a transparent electrode formed on the buffer layer, Is provided.

  As a method for forming a CIGS light absorption layer made of a Cu—In—Ga—Se quaternary alloy film, a vapor deposition method is known, but a metal produced by sputtering to obtain a uniform film with a larger area. A method for selenizing a precursor film has been proposed (see, for example, Patent Document 1).

  The sputtering method is a method in which a metal precursor film is produced by sputtering using a Cu—Ga alloy sputtering target and an In target, and this is heat-treated in a Se or S atmosphere to form a CIGS film. Since the quality of the CIGS film formed by this sputtering method largely depends on the quality of the Cu—Ga alloy sputtering target, a high quality Cu—Ga alloy sputtering target is desired.

Japanese Patent No. 3249408 JP 2000-73163 A JP 2008-138232 A JP 2005-60745 A JP 2010-265544 A

  By the way, in recent years, optimization of CIGS layer composition by a solar cell manufacturer has progressed, and a Cu—Ga alloy sputtering target having a Ga concentration of 30% by mass or more has been demanded.

  As a method for producing a Cu—Ga alloy sputtering target, a production method by a melting method (for example, see Patent Document 2) or a powder metallurgy method (for example, see Patent Documents 3 to 5) is known.

  Patent Document 2 proposes a method for producing a Cu—Ga alloy sputtering target by a melting method, but the cast alloy having a Ga concentration of 30% by mass or more is brittle, and the target is cracked in subsequent processing. is there.

  Patent Document 3 proposes a method of manufacturing a Cu—Ga alloy sputtering target having a Ga concentration of 30% by mass or more and having no cracks or defects by a powder sintering method. The manufactured Cu—Ga alloy sputtering target has a two-phase coexistence structure in which high Ga-containing alloy grains are surrounded by a grain boundary phase made of a low Ga alloy.

  However, the Cu—Ga alloy sputtering target cannot form a uniform sputtered film if the metal phase is complicated. In this regard, in Patent Document 4, the metal structure (metal phase) of a rare earth-transition metal alloy sputtering target that forms a complex metal phase affects the uniformity of the sputtered film, as in the case of Cu-Ga alloys. It is described. Since it is calculated | required that a Cu-Ga alloy sputtering target can form a uniform film with a large area, what a metal phase is not complicated is preferable.

Even if the metal phase can be simplified, a Cu-Ga alloy sputtering target having a Ga concentration of 30% by mass or more has a Ga concentration of 35 atoms as described in Comparative Example 6 of Patent Document 5. % (37% by mass) of Cu ₉ Ga ₄ phase (γ phase) single phase Cu—Ga alloy sputtering target has been shown to break during sputtering.

  Furthermore, when an abnormal discharge (arc discharge) occurs during sputtering, splash splashes and adheres to the metal precursor film, or small pieces fall off from the Cu—Ga alloy sputtering target and adhere to the metal precursor film. There arises a problem that the solar cell characteristics and the yield are lowered. For this reason, a high-quality Cu—Ga alloy sputtering target is also required not to cause abnormal discharge or particle dropout.

  The present invention has been proposed in view of the above circumstances, and in a Cu-Ga alloy sputtering target having a high Ga concentration, the sputtered film has excellent uniformity, and there is no cracking during target processing and sputtering. Provided is a Cu—Ga alloy sputtering target in which abnormal discharge and generation of particles are suppressed.

The Cu—Ga alloy sputtering target according to the present invention that achieves the above-described object has a Ga concentration of 30 mass% to 45 mass%, an average crystal grain size of 20 μm or less, a γ ₁ phase, a γ ₂ phase, and a γ ₃ phase. And the area ratio of the group consisting of γ phase is 95 area% or more, the porosity is 1% or less, and the three-point bending strength is 200 MPa or more.

In the present invention, the average crystal grain size, the area ratio of the group consisting of γ ₁ phase, γ ₂ phase, γ ₃ phase and γ phase, porosity, and three-point bending strength are contained, containing Ga of 30 mass% to 45 mass%. By satisfying the predetermined conditions, even if the Ga concentration is high, cracks, abnormal discharge during sputtering, and generation of particles in the film are suppressed, and a sputtered film having a uniform composition can be formed.

It is a Cu-Ga type alloy phase diagram. It is a figure which shows the X-ray-diffraction pattern of (gamma) phase of a Cu-Ga alloy. 2 is an optical micrograph of a sintered body of Example 1.

  Below, the Cu-Ga alloy sputtering target to which this invention is applied is demonstrated in detail. Note that the present invention is not limited to the following detailed description unless otherwise specified.

<Cu-Ga alloy sputtering target>
First, a Cu—Ga alloy sputtering target will be described. In addition, a Cu-Ga alloy sputtering target includes the state of the target material before target finishing processes, such as surface grinding and bonding. The Cu—Ga alloy sputtering target can be produced by a powder sintering method using Cu—Ga alloy powder as a raw material, as will be described later.

This Cu—Ga alloy sputtering target has a Ga concentration of 30% by mass to 45% by mass, an average crystal grain size of 20 μm or less, a group consisting of γ ₁ phase, γ ₂ phase, γ ₃ phase and γ phase (hereinafter, is also 95% by area or more, the porosity is 1% or less, and the three-point bending strength is 200 MPa or more.

Ga density | concentration is 30 mass%-45 mass%. When the Ga concentration is 30% by mass or more, the CIGS layer composition for solar cells is optimized, but it is preferably 45% by mass or less. When the Ga concentration is greater than 45% by mass, the area ratio of different metal phases other than the γ ₁ phase, γ ₂ phase, γ ₃ phase and γ phase increases in the metal phase of the Cu—Ga alloy sputtering target, resulting in sputtering. The uniformity of the film will be insufficient. Therefore, the Ga concentration is 30% by mass to 45% by mass.

The metal phase is a simple metal phase in which the area ratio of the γ phase group is 95 area% or more of the entire Cu—Ga alloy sputtering target. Here, the γ phase, γ ₁ phase, γ ₂ phase, and γ ₃ phase are shown in the Cu—Ga based alloy phase diagram shown in FIG. 1. Although these phases are slightly different in Ga concentration, the crystal structures are classified into the same space group P43m and are very similar. Since the target material is evaporated and released from the sputtering target having such a crystal structure, the uniformity of the film quality such as the composition and the film thickness of the sputtered film is improved. When the area ratio of the γ phase group is less than 95 area%, the area ratio of the metal phase having a different crystal structure increases and the uniformity of the sputtered film becomes insufficient.

In addition to the γ ₁ phase, γ ₂ phase, γ ₃ phase, and γ phase, the metal phase of the Cu—Ga alloy includes a Cu (α) phase, a β phase, a ζ phase, a θ phase, and the like. The Ga concentration of each metal phase can be known from the Cu—Ga-based alloy phase diagram of FIG. That is, the Cu (α) phase has a Ga concentration of 0 to 22.2 mass%, the β phase has a Ga concentration of 20.8 mass% to 29.4 mass%, and the ζ phase has a Ga concentration of 22.1 mass% to 24.2 mass%. %, Γ phase is 31.5 mass% to 36.8 mass%, γ ₁ phase is 31.8 mass% to 39.6 mass%, and γ ₂ phase is Ga concentration 36.0 mass% to 39.9 mass%. The γ ₃ phase has a Ga concentration of 39.7% by mass to 45.0% by mass, and the θ phase has a Ga concentration of 66.7% by mass to 68.7% by mass. A Cu-Ga alloy having a Ga concentration that does not belong to any metal phase is a mixed state of a plurality of metal phases having different Ga concentrations.

Since the Ga concentrations of the γ phase, γ ₁ phase, γ ₂ phase and γ ₃ phase overlap each other, it is difficult to specify the respective metal phases only by the Ga concentration, but the Ga concentration of 31.5 mass % To 44.9% by mass of the metal phase is only a γ phase group consisting of a γ ₁ phase, a γ ₂ phase, a γ ₃ phase and a γ phase, and there is no other metal phase in this Ga concentration range. Due to the characteristics of such a Cu-Ga alloy, the γ ₁ phase, γ ₂ phase, γ ₃ phase and γ phase and the metal phases different from these are secondary electrons by EPMA analysis (Electron Probe Micro Analyzer) of the target polished surface. A distinction can be made from images, backscattered electron images and quantitative analysis. Furthermore, the area ratio of the metal phase having a Ga concentration of 31.5% by mass to 44.9% by mass, that is, the γ phase group, can be obtained by using image analysis processing of EPMA analysis. Also, if the color tone of the metal phase specified by the EPMA analysis is known, the area ratio of the γ phase group can be obtained from the optical microscope observation of the target polished surface and its image processing without performing the EPMA analysis every time. it can.

The metal phase can be identified more clearly by using X-ray diffraction in addition to EPMA analysis and optical microscope observation. For example, when a target surface made of a metal phase of the γ phase group is subjected to X-ray diffraction analysis, the diffraction pattern shown in FIG. When a metal phase other than the γ phase group is present, another diffraction peak is mixed. Which angle of 2θ of X-ray diffraction appears at the angle depends on the metal phase. Therefore, the type of metal phase contained in the target can be determined from the appearance pattern of the X-ray diffraction peak. However, the γ ₁ phase, the γ ₂ phase, the γ ₃ phase, and the γ phase are identified as a γ phase group because it is difficult to distinguish the respective diffraction peaks. Since the area ratio of each metal phase is not known only by X-ray diffraction analysis, the area ratio is calculated from the above-mentioned EPMA analysis and optical microscope observation.

  The cross-sectional structure of the Cu—Ga alloy sputtering target is composed of particles having an average crystal grain size of 20 μm or less. When the average crystal grain size is larger than 20 μm, the mechanical strength of the target is insufficient, and the target small piece falls off during sputtering, or is easily cracked due to a thermal change during sputtering. In addition, when the average crystal grain size is larger than 20 μm, the surface roughness of the portion where the target is scraped by the collision of Ar ions during sputtering, the so-called erosion portion increases, and the tip of the rough surface increases. Fall off and become particles and adhere to the sputtered film. The average crystal grain size is measured by polishing a surface parallel to the surface to be sputtered of the Cu-Ga alloy sputtering target and using a metallographic image in which crystal grains can be observed using a polarizing optical microscope or SEM (Scanning Electron Microscope). To do. Then, based on the cutting method described in JIS H 0501 “Copper Product Grain Size Test Method”, the number of particles cut by the line drawn on the metal structure image, and the average crystal grain from the cut length Find the diameter.

  The porosity is 1% or less. When the porosity is larger than 1%, the pores become the starting point of the target crack and are easily broken. Further, when the porosity is larger than 1%, abnormal discharge (arc discharge) is likely to occur during sputtering, and splash is scattered, which adheres to the sputtered film. The holes can be observed with SEM, EPMA or optical microscope on the target polished surface. The porosity can be obtained by image analysis of these.

  The three-point bending strength is 200 MPa or more. When the three-point bending strength is smaller than 200 MPa, cracks and chips are generated in the surface grinding process and the bonding process of target production. On the other hand, when the pressure is less than 200 MPa, particles are likely to be generated by cracking due to thermal changes during sputtering or dropping off the leading end of the rough surface generated in the erosion portion. The three-point bending strength is determined by the method described in JIS R1601 (Fine ceramic room temperature bending strength test method).

  The Cu—Ga alloy sputtering target having the above configuration has a high Ga concentration of 30% to 45% by mass, but the average crystal grain size is 20 μm or less, and the area ratio of the γ phase group is 95 areas. %, Porosity is 1% or less, and the three-point bending strength is 200 MPa or more, so there is no cracks or defects, no abnormal discharge or erosion occurs during sputtering, and a uniform film without particles is formed. can do.

  Furthermore, the half width and orientation degree index in the X-ray diffraction of the Cu—Ga alloy sputtering target will be described. However, in the X-ray diffraction, the diffraction peaks due to Cu-Kα1 and Kα2 are separated into the diffraction peaks due only to the Cu-Kα1 line.

  The (222) plane, (321) plane, (330) plane, (332) plane, (422) plane, (510) plane, (521) plane, (600) of the γ phase group in the X-ray diffraction shown in FIG. The average half width obtained from the eight diffraction peaks of the surface is 0.13 deg. The above is preferable. The width at half maximum increases as the crystal grains become smaller. This is because, as a result of the reduction of the number of lattice planes of crystal grains, X-rays scattered at a slightly different angle θ from the diffraction peak are not easily canceled out by X-rays from another lattice plane. As the crystal grains become smaller, the grain boundaries increase, and the crystal dislocations that occur when the metal structure is deformed are prevented by the grain boundaries, thereby increasing the strength.

  The average half width of the X-ray diffraction peak is 0.13 deg. In the above, the crystal grain size constituting the metal structure of the Cu—Ga alloy sputtering target is reduced, and the crystal grain boundary is increased, whereby the mechanical strength is improved. The average half width is 0.13 deg. Is smaller than 200 MPa, the cracking and chipping of the sputtering target will occur.

  As shown in FIG. 2, the (222) plane, (321) plane, (330) plane, (332) plane, (422) plane, (510) plane, (521) plane, (600) plane of the γ phase group Respectively, 2θ is 36, 39, 44, 49, 51, 53, 58 and 64 deg. Appears in a nearby position. The average of the full width at half maximum can be calculated by dividing the total of the full width at half maximum of each surface by the number of peaks.

In addition, the (222) plane, (321) plane, (330) plane, (332) plane, (422) plane, (510) plane, (521) plane, (600) plane of the γ phase group in X-ray diffraction The degree of orientation index K _(hkl) is preferably 1.5 or less. The orientation degree index K _(hkl) is obtained by the following equation.

K _(hkl) = (I _(hkl) / ΣI _(hkl) ) / ( _{ID (hkl)} / ΣID _(hkl) )
here,
I _(hkl) is the diffraction peak intensity of the (hkl) plane of the measured γ phase group,
_{ID (hkl)} is the diffraction peak intensity of the (hkl) plane of the γ phase indicated by 71-0458 in the ICDD card data as standard data,
ΣI _(hkl) and ΣID _(hkl) are
ΣI _(hkl) = I ₍₂₂₂₎ + I ₍₃₂₁₎ + I ₍₃₃₀₎ + I ₍₃₃₂₎
+ I ₍₄₂₂₎ + I ₍₅₁₀₎ + I ₍₅₂₁₎ + I ₍₆₀₀₎
ΣI _{D (hkl)} = _{ID (222)} + _{ID (321)} + _{ID (330)}
+ _{ID (332)} + _{ID (422)} + _{ID (510)}
+ _{ID (521)} + _{ID (600)}
It is.

When the value is 1, the orientation degree index indicates that the crystal has no orientation at all. When the value is large, the orientation is strengthened on the target crystal plane. When the crystal orientation is strong, segregation occurs in the direction of evaporation and emission from the sputtering target, and it cannot reach the substrate effectively, resulting in a decrease in film formation rate. In addition, when the crystal orientation is strong, the erosion shape changes and the target consumption is likely to increase. In the Cu—Ga alloy sputtering target, such a problem occurs when the orientation degree index K _(hkl) is larger than 1.5.

  The oxygen content of the Cu—Ga alloy sputtering target is preferably 0.2% by mass or less. If the oxygen content is more than 0.2% by mass, abnormal discharge (arc discharge) is likely to occur and splash splashes, which adhere to the sputtered film.

  The Cu—Ga alloy sputtering target having the above-described configuration has an average crystal grain size, an area ratio of the γ phase group, a porosity, and a three-point bending strength even when the Ga concentration is as high as 30% to 45% by mass. Satisfying the predetermined condition, it is a simple alloy phase, there is no crack chipping during target processing and sputtering, and abnormal discharge during sputtering or generation of particles in the film can be prevented.

  Moreover, this Cu-Ga alloy sputtering target calculates | requires the Ga density | concentration analysis value by EPMA analysis of 5-10 different places, for example, and the maximum and minimum difference of this analysis value will be 3.0 mass% or less. The Cu—Ga alloy sputtering target is a high-quality one having a uniform composition because the difference in Ga concentration is as small as 3.0 mass% or less and the variation in Ga concentration is small. Therefore, when sputtering is performed using a Cu—Ga alloy sputtering target, the difference between the maximum and the minimum of the Ga concentration analysis value is 3.0% by mass or less. A film can be formed.

<Method for producing Cu-Ga alloy sputtering target>
The Cu—Ga alloy sputtering target having the above-described configuration can be manufactured by a manufacturing method having a sintering process from a stirring process described below.

  In this Cu—Ga alloy sputtering target manufacturing method, Cu powder is stirred at a temperature of 150 ° C. to 300 ° C. in a mixed gas atmosphere containing hydrogen gas, and Cu powder subjected to this stirring process is mixed with Ga powder. Preparation of alloy powder that directly forms Cu-Ga alloy powder by stirring mixed powder containing 30 mass% to 45 mass% in a vacuum or inert atmosphere at a temperature of 30 ° C. to 300 ° C. Cu-Ga alloy powder obtained by the process is used. And the manufacturing method of a Cu-Ga alloy sputtering target WHEREIN: Cu-Ga alloy powder which gave the heat treatment process heat-processed at the temperature of 250 to 836 degreeC in a vacuum or an inert gas atmosphere is in a vacuum or an inert gas atmosphere. The Cu—Ga alloy powder is sintered by a sintering process in which sintering is performed by a hot press method at a temperature of 250 ° C. to 836 ° C. and a press pressure of 5 MPa to 30 MPa to produce a Cu—Ga alloy sputtering target.

  In the method of manufacturing a Cu-Ga alloy sputtering target, a low oxygen content, a small average crystal grain size, and a large X-ray diffraction half are obtained by a suitable atmosphere, direct alloy powder formation at a low temperature, a suitable heat treatment and target sintering. A Cu—Ga alloy sputtering target having a value width (small crystallite), a simple metal phase, a uniform target composition, a dense structure, no crystal orientation, and strong bending strength can be manufactured. Such a Cu—Ga alloy sputtering target can form a sputtered film that is uniform and has very few defects without cracking during sputtering. In addition, the Cu—Ga alloy sputtering target has a high productivity because it has a high deposition rate and consumes less target.

<1. Method for producing Cu-Ga alloy powder>
First, the manufacturing method of Cu-Ga alloy powder is demonstrated.

(material)
Cu powder and Ga are used as raw materials for the Cu-Ga alloy powder.

  As the Cu powder, for example, electrolytic Cu powder or atomized Cu powder produced by an electrolytic method or an atomizing method can be used. The electrolytic Cu powder is produced by depositing spongy or dendritic Cu on the cathode by electrolysis in an electrolytic solution such as a copper sulfate solution. As for the atomized Cu powder, spherical or irregular shaped Cu powder is produced by a gas atomization method, a water atomization method, a centrifugal atomization method, a melt extraction method, or the like. In addition, you may use what was manufactured by Cu methods other than these methods.

  The purity of the Cu powder is appropriately selected so as not to affect the characteristics of the CIGS light absorption layer formed from the Cu—Ga alloy sputtering target. When the oxygen content in the Cu powder is more than 0.2% by mass, the stirring process described later takes a long time, so the oxygen content is preferably 0.2% by mass or less. . Further, when the content of Fe, Ni, and Cr in the Cu powder is more than 3 ppm, the quantum efficiency of the CIGS light absorption layer is lowered, so that Fe, Ni, and Cr are preferably 3 ppm or less. .

  The average particle diameter of the Cu powder is preferably 5 μm to 300 μm. When the average particle size of the Cu powder is 5 μm or more, special handling for preventing the scattering of the Cu powder is not required, and the alloy powder production apparatus is increased in size due to the increase in the bulk capacity of the Cu powder. Can be prevented. In addition, when the average particle size of the Cu powder is 300 μm or less, the surface area (BET) of the Cu powder that must be coated with Ga is insufficient, and surplus unreacted liquid phase Ga tends to remain. Can be prevented. Thereby, when the average particle diameter of Cu powder is 300 micrometers or less, it can suppress that dispersion | variation arises in the composition of Cu-Ga alloy powder by presence of unreacted liquid phase Ga. Therefore, by making the average particle size of Cu powder 5 μm or more and 300 μm or less, it is not necessary to take measures to prevent Cu powder scattering, and it is possible to prevent enlargement of the alloy powder production apparatus, and also the liquid phase of unreacted Ga And the variation in the composition of the Cu—Ga alloy powder can be suppressed.

  The average particle size of the Cu powder is obtained by measuring the particle size distribution of the Cu powder by a laser diffraction method, integrating the abundance ratio (volume basis) from the small diameter side, and integrating the abundance ratio over the entire particle diameter. The particle size (D50) is half of the value. The value of the specific surface area (hereinafter referred to as BET value) can be determined by the BET method.

(Stirring process)
When the surface of the Cu powder is oxidized, the reaction with Ga becomes insufficient. When the surface of the Cu powder is oxidized and the reaction with Ga becomes insufficient, there is an unreacted Cu powder whose surface is not alloyed with Ga, and variation in the Ga concentration of the Cu-Ga alloy powder. Will become bigger. Here, when the Cu powder is subjected to a rust inhibitor treatment, the progress of oxidation is suppressed, but the variation in Ga concentration is not eliminated. The reason why the reaction between the Cu powder and Ga is insufficient is considered to be because the oxide film and the rust preventive film on the surface of the Cu powder inhibit the contact with Ga. Before reacting Cu powder with Ga, it is necessary to activate the surface by removing the oxide film and rust preventive film on the surface to improve the reactivity.

  Therefore, in the stirring step, the Cu powder is stirred at a temperature of 150 ° C. to 300 ° C. in a mixed gas atmosphere containing hydrogen gas. In this stirring step, the oxide film and the rust inhibitor are removed from the surface of the Cu powder. The Cu powder removes the oxide film and rust preventive agent on the surface by the treatment in the stirring step, and the reactivity with Ga is improved. Thereby, when this stirring process is performed, Ga and unreacted Cu powder decrease, and it can suppress effectively the dispersion | variation in Ga density | concentration of Cu-Ga alloy powder or Cu-Ga alloy sputtering target. it can.

  The stirring step is performed in a mixed gas atmosphere containing hydrogen gas. The hydrogen gas concentration in the mixed gas is preferably 0.1% to 5%. When the hydrogen gas concentration is lower than 0.1%, an oxide film and a rust preventive agent remain on the surface of the Cu powder, resulting in insufficient reactivity with Ga, effectively improving variation in Ga concentration. Can not do it. When the hydrogen gas concentration is higher than 5%, the effect of removing the oxide film and the rust inhibitor is sufficient, but the amount of expensive hydrogen gas used increases. Moreover, when hydrogen gas concentration is high, the high safety | security with respect to ignition and combustion is requested | required and an installation will become expensive.

  The balance of the mixed gas is preferably nitrogen gas or argon gas. When the balance is nitrogen gas or argon gas, the surface activation state of the Cu powder can be maintained. The atmosphere of the stirring step may be replaced with a mixed gas after putting Cu powder into the stirring device. When oxygen is mixed, removal of the oxide film and the rust inhibitor does not proceed effectively. Therefore, it is preferable to introduce the mixed gas after evacuating the gas until the pressure becomes 100 Pa or less.

  The temperature of the stirring step is 150 ° C to 300 ° C. When the temperature is lower than 150 ° C., the oxide film and the rust preventive agent remain on the surface of the Cu powder, and the reactivity with Ga becomes insufficient, and the variation in Ga concentration cannot be effectively improved. When the temperature is higher than 300 ° C., the effect of removing the oxide film and the rust inhibitor is sufficient, but the Cu powder whose surface is activated is aggregated and solidified. Therefore, in the stirring step, by setting the temperature to 150 ° C. to 300 ° C., the oxide film and the rust preventive agent can be removed from the surface of the Cu powder, the reactivity of the Cu powder to Ga is not inferior, and the variation in Ga concentration is suppressed. It is possible to prevent the Cu powder from aggregating.

  The temperature holding time is preferably 10 minutes to 2 hours. When the holding time is shorter than 10 minutes, an oxide film or a rust preventive agent remains on the surface of the Cu powder, the reactivity with Ga becomes insufficient, and variation in Ga concentration cannot be effectively improved. . When the holding time is longer than 2 hours, the reactivity between Cu powder and Ga can be sufficiently achieved, and the effect of suppressing variation in composition is maintained, but the amount of expensive hydrogen gas used increases. End up.

  The stirring step is performed while stirring the Cu powder. This is because, when stirring is not performed, the contact between the Cu powder and the mixed gas becomes insufficient, and the oxide film and the rust preventive agent remain on the surface of the Cu powder.

  As the stirring device, a rotating container type stirring device such as a cylinder, a double cone, or a twin shell, or a stirring device in which a stirring bar such as a stirring blade or a stirring blade moves in a fixed container can be used.

(Alloy powder production process)
Next, an alloy powder preparation step is performed in which a predetermined amount of Ga is added to the Cu powder whose surface has been treated by the stirring step described above to prepare a Cu-Ga alloy powder.

  Next, in the alloy powder production process, mixed powder prepared by mixing Ga at a ratio of 30% by mass to 45% by mass with Cu powder subjected to the agitation process is heated at 30 ° C. to 300 ° C. in a vacuum or an inert gas atmosphere. By stirring at a temperature, Cu—Ga alloy powder is directly formed. Conventionally, Cu and Ga were once melted and alloyed at a high temperature, and the produced Cu—Ga alloy ingot was pulverized to obtain a Cu—Ga alloy powder. However, in this alloy powder production step, a Cu-Ga alloy ingot is produced and pulverized by stirring a mixed powder obtained by mixing Cu powder and Ga at a temperature of 30 ° C to 300 ° C under the above conditions. Even if it does not do, Cu-Ga alloy powder can be directly produced from the state of a raw material.

  Specifically, the Cu powder and Ga pieces weighed at the above-described ratio are controlled to a temperature higher than the melting point of Ga and lower than the melting point of Cu, that is, in the range of 30 ° C. to 300 ° C. A Cu—Ga binary alloy is formed.

  The Cu-Ga alloy is considered to be formed through the following process. Ga, which has become liquid beyond the melting point, is uniformly dispersed between Cu powders while becoming small droplets by the shearing motion of mixing. The dispersed Ga droplets adhere to the periphery of the Cu powder, and when the Cu powder and Ga droplets come into contact with each other, the diffusion of Ga begins in the Cu powder, increasing the Ga concentration and forming an alloy while forming a Cu-Ga intermetallic compound. The reaction proceeds. At this time, the surface of the Cu—Ga alloyed material is a Cu—Ga intermetallic compound layer having a high Ga concentration, and the central portion is pure Cu.

  This mixing of Cu powder and Ga is effective for the progress of a uniform alloying reaction (homogenization reaction). Moreover, it is considered that the shearing motion of mixing also suppresses the formation of a lump due to the adhesion between the powders. When a lump is generated, voids are formed in the sintered body in a subsequent sintering process such as hot pressing, and the density becomes non-uniform.

  Similarly to Cu powder, Ga is appropriately selected so as not to affect the characteristics of the CIGS light absorption layer formed from the Cu—Ga alloy sputtering target. As with the Cu powder, the purity of Ga is preferably 3 ppm or less because the quantum efficiency of the CIGS light-absorbing layer is lowered when Fe, Ni, and Cr are more than 3 ppm. The oxygen content in Ga is preferably 0.2% by mass or less. When the oxygen content in Ga is more than 0.2% by mass, abnormal discharge is likely to occur during sputtering.

  Ga is a metal having a low melting point (melting point: 29.78 ° C.). Ga to be added to the Cu powder is preferably melted liquid Ga because stirring can be started immediately. Although there is no restriction | limiting in the shape of Ga, when it is a small piece, weighing is easy. The small piece can be obtained by melting and casting Ga in the vicinity of room temperature and crushing the casting.

  Cu powder and Ga are blended in a mass ratio of 70:30 to 55:45. In the alloy powder preparation process, Ga can be uniformly coated on the surface of the Cu powder in a short time because Ga is 30% by mass or more, and it can be coated in a short time because Ga is 45% by mass or less. Ga can be alloyed. The Cu—Ga alloy powder formed in this alloy powder production step has a Cu—Ga alloy layer on the surface of the Cu powder.

  The alloy powder preparation step is performed in a vacuum or an inert gas atmosphere. In the alloy powder production step, it is possible to suppress the inclusion of oxygen in the Cu—Ga alloy powder by alloying in a vacuum or an inert gas atmosphere.

  The oxygen partial pressure in a vacuum or an inert gas atmosphere is preferably 20 Pa or less. When it is higher than 20 Pa, the oxygen content of the formed Cu—Ga alloy powder increases, the oxygen content of the produced sputtering target also increases, and abnormal sputtering occurs when sputtered with a large input power. The inert gas atmosphere is preferably nitrogen gas or argon gas.

  The temperature at the time of alloying is 30 ° C to 300 ° C. When the temperature is lower than 30 ° C., the reactivity between the Cu powder and Ga becomes insufficient, unreacted Cu powder remains, and the Ga concentration of the Cu—Ga alloy powder varies. When the temperature is higher than 300 ° C., the surface of the Cu powder is alloyed, but when the temperature is increased, the Cu—Ga alloy powder begins to aggregate. Since this agglomeration can be solved by a shearing motion by stirring, a Cu-Ga alloy powder can be formed at a temperature higher than 300 ° C., but the thermal deterioration of the stirring device is severe and the frequency of replacement of device parts is increased. It becomes expensive. Therefore, by setting the temperature to 30 ° C. to 300 ° C., Cu powder and Ga can be sufficiently reacted without aggregation.

  The temperature holding time is preferably 30 minutes to 4 hours. When the holding time is shorter than 30 minutes, the reactivity between the Cu powder and Ga becomes insufficient, unreacted Cu powder remains, and the Ga concentration of the Cu—Ga alloy powder varies. When the holding time is longer than 4 hours, the oxygen content of the Cu—Ga alloy powder increases even in a vacuum or an inert gas atmosphere. Therefore, by setting the temperature holding time to 30 minutes to 4 hours, the Cu powder and Ga can be sufficiently reacted to suppress an increase in the oxygen content of the Cu-Ga alloy powder.

  The agitation is effective for directly forming the Cu—Ga alloy powder while suppressing aggregation and increasing the contact frequency between the Cu powder and Ga.

  As the stirring device, a rotating vessel type stirring device such as a cylinder, a double cone, or a twin shell similar to the stirring step, or a stirring device in which a stirring bar such as a stirring blade or a stirring blade moves in a fixed vessel can be used. . When the Cu powder subjected to the stirring step described above is exposed to the air, the surface is immediately oxidized and the reactivity with Ga is lowered. For this reason, the alloy powder production process is preferable because it can be performed while being isolated from the atmosphere by performing alloying after the stirring process in the same stirring apparatus that performs the stirring process.

  The material of the stirrer vessel and stirrer used in the stirring step and the alloy powder preparation step is titanium nitride (TiN) from the viewpoint of heat resistance, wear resistance, suppression of metal impurities such as Fe, Ni, Cr, etc. ), Chromium nitride (CrN), and diamond-like carbon (DLC) (Diamond like Carbon) coated stainless steel material is preferable.

  As mentioned above, in the manufacturing method of Cu-Ga alloy powder, by performing stirring process with respect to Cu powder, the reactivity with Ga of the surface of Cu powder becomes high, and Ga density | concentration is high on the surface of Cu powder. A uniform Cu—Ga intermetallic compound layer can be formed. In the obtained Cu—Ga alloy powder, variation in Ga concentration in the Cu—Ga intermetallic compound layer is suppressed, and variation is within 3.0 mass%.

<2. Manufacturing method of Cu-Ga alloy sputtering target>
Next, the manufacturing method which manufactures a Cu-Ga alloy sputtering target using the Cu-Ga alloy powder obtained by the stirring process and alloy powder preparation process mentioned above is demonstrated.

(Heat treatment process)
In the heat treatment step, the Cu—Ga alloy powder obtained by the above-described alloy powder production step is heat-treated at a temperature of 250 ° C. to 836 ° C. in a vacuum or an inert gas atmosphere.

  This will be described with reference to the phase diagram of the Cu—Ga alloy shown in FIG. In the phase diagram, the region above the temperature indicated by the liquidus is the liquid phase region where only the liquid phase exists, and the region below the temperature indicated by the solidus is the solid phase region where only the solid phase exists. The temperature region between the lines is the coexistence region of the liquid phase and the solid phase.

  The Cu—Ga alloy powder before heat treatment in which a large amount of Ga is present on the powder surface is located in the solid phase region. When this Cu-Ga alloy powder is heat-treated, the alloying is completed with the powder itself positioned in the solid phase region, and the final is temporarily positioned in the coexistence region of the liquid phase and the solid phase. In particular, it is considered that the alloying may be completed in the solid phase region.

  That is, in the former case, it is considered that Ga, which is present in a large amount on the powder surface, diffuses into the powder and alloying with Cu proceeds.

  In the latter case, diffusion of Ga into the powder is slow, and the surface portion of the powder becomes a liquid phase, which is considered to be located in the coexistence region of the liquid phase and the solid phase. It is considered that the liquid phase that appears at this time is alloyed by repeating contact with the surrounding Cu—Ga alloy powder and is finally located in the solid phase region. Therefore, in the latter case, when the pressure is applied by the hot press apparatus, the generated liquid phase flows and is pushed out from the gap of the press die.

  Therefore, in the heat treatment step, the Cu—Ga alloy powder is heat treated before sintering by hot pressing. With this heat treatment, the Cu-Ga alloy powder starts melting of the low melting point Cu-Ga alloy layer existing on the Cu particle surface, and at the same time, Ga in the Cu-Ga alloy layer on the Cu particle surface and Cu inside the particle are mixed. By interdiffusion, the Ga concentration on the surface of Cu particles can be lowered, and the appearance temperature of the liquid phase can be increased. Thereby, in the sintering process performed later, sintering progresses without producing a Ga liquid phase during sintering by hot pressing, and a sputtering target can be produced.

  The temperature of heat processing is 250 to 836 degreeC. When the temperature is lower than 250 ° C., interdiffusion between Ga in the alloy layer on the Cu particle surface and Cu inside the particle does not proceed sufficiently, and a high Ga concentration alloy layer remains, and during sintering by hot pressing. The Ga liquid phase appears and the Cu—Ga alloy powder leaks. When the temperature is higher than 836 ° C., a large amount of liquid phase is generated and separated from the Cu—Ga alloy powder.

  It is preferable to adjust the temperature of heat processing with the mixing | blending ratio of Ga in an alloy powder preparation process. When a small amount of liquid phase is generated during the heat treatment and aggregates are formed, the aggregation is weak and does not affect the sintering in the subsequent sintering process. When a phase appears, the liquid phase collects and separates from the Cu—Ga alloy powder, resulting in a large variation in composition. Such separation of the liquid phase can be effectively suppressed by controlling the heat treatment temperature in accordance with the Ga mixing ratio in the alloy powder production process.

  Specifically, the mixing ratio of Ga in the alloy powder production process is X mass%, and the heat treatment temperature will be described. The relationship between the compounding ratio of Ga (X mass%) and the heat treatment temperature (T ° C.) is represented by the state diagram shown in FIG. A liquid phase appears at a temperature exceeding the solidus of the phase diagram. Therefore, the temperature of the heat treatment is preferably 250 ° C. or more and not more than the solidus. In the heat treatment step, by setting the heat treatment temperature to 250 ° C. or higher and below the solidus line, mutual diffusion of Ga in the alloy layer on the surface of the Cu particles and Cu inside the particles is achieved without generating a liquid phase. Can do.

The solid line can be expressed as an approximate expression consisting of the Ga mixing ratio (X) and the heat treatment temperature (T) as follows. When X is in the range of 25.0% by mass to 29.34% by mass, T = −0.102 · X ² −4.16 · X + 1045.4. When X is in the range of 29.34% by mass to 31.5% by mass, T = 836. When X is in the range of 31.5% by mass to 39.0% by mass, T = −4.8169 · X ² + 292.85 · X−3609.4. When X is in the range of 39.0% to 45% by mass, T = −3.6111 · X ² + 264.17 · X− 4325.

  An example of the heat treatment temperature from the temperature calculated by the above approximate expression is as follows.

  When the compounding ratio of Ga in the alloy powder production process is 35% by mass, the heat treatment temperature in the heat treatment process is 250 ° C. to 740 ° C. When the compounding ratio of Ga in the alloy powder production process is 40% by mass, the heat treatment temperature in the heat treatment process is 250 ° C. to 464 ° C.

  In addition, when the mixture ratio of Ga in an alloy powder preparation process is 30 mass%, the heat processing temperature of a heat processing process will be 250 to 836 degreeC from the state diagram shown in FIG. When the compounding ratio of Ga in the alloy powder production process is 45% by mass, the heat treatment temperature in the heat treatment process is 250 ° C. to 254 ° C. from the state diagram shown in FIG.

  The holding time of the heat treatment temperature is preferably 30 minutes to 4 hours. When the holding time is shorter than 30 minutes, interdiffusion between Cu and Ga becomes insufficient, and a liquid phase appears in a hot press in the next sintering step, and Cu—Ga alloy powder is pushed out from the press die. . If the holding time is longer than 4 hours, the oxygen content of the Cu-Ga alloy powder increases even in a vacuum or inert gas atmosphere with an oxygen partial pressure of 20 Pa or less, and the oxygen content of the produced sputtering target When the amount is increased and sputtering is performed with a large input power, abnormal discharge occurs.

  The heat treatment is performed in a vacuum or an inert gas atmosphere. The oxygen partial pressure in a vacuum or inert atmosphere is preferably 20 Pa or less. When the pressure is higher than 20 Pa, the oxygen content of the heat-treated Cu—Ga alloy powder increases, the oxygen content of the produced sputtering target also increases, and abnormal sputtering occurs when sputtering is performed with a large input power. The inert atmosphere is preferably nitrogen gas or argon gas.

  This heat treatment step is preferably performed in the same hot press apparatus as the sintering step described later. When heat treatment is performed in the same hot press apparatus as the sintering process, it is not necessary to provide a separate heat treatment apparatus, and the cooling time after the heat treatment and the step of taking out the Cu—Ga alloy powder can be eliminated. As a result, when the heat treatment step and the sintering step are performed with the same hot press apparatus, the cooling time is not required as compared with the case where the heat treatment is performed with another heat treatment apparatus. Since the time can be shortened and there is no need to take out the Cu—Ga alloy powder, it is possible to prevent the yield from being lowered.

  When the heat treatment step is performed in the same hot press apparatus as the sintering step, it is preferable that the press pressure is no load on the Cu—Ga alloy powder or a pressure of 0.1 MPa or less. The pressure of 0.1 MPa or less corresponds to the pressure due to the weight of the upper punch of the hot press apparatus, and the pressure of no load or 0.1 MPa or less substantially does not apply pressure to the Cu-Ga alloy powder. State. By setting it as such a state, even if a liquid phase appears, it can prevent that Cu-Ga alloy powder leaks out from the press die of a hot press apparatus.

(Sintering process)
Next, the Cu—Ga alloy powder heat-treated in the heat treatment step is sintered by a hot press method at a temperature of 250 ° C. to 836 ° C. and a press pressure of 5 MPa to 30 MPa in a vacuum or an inert gas atmosphere.

  By setting the atmosphere of hot pressing in a vacuum or an inert gas atmosphere, an increase in the oxygen content of the sintered body can be suppressed. The oxygen partial pressure in a vacuum or an inert gas atmosphere is preferably 20 Pa or less. When the pressure is higher than 20 Pa, the oxygen content of the formed Cu—Ga alloy sintered body increases, the oxygen content of the produced sputtering target also increases, and abnormal sputtering occurs when sputtering is performed with a large input power. The inert gas atmosphere is preferably nitrogen gas or argon gas.

  The temperature of the hot press is 250 ° C to 836 ° C. When the temperature is lower than 250 ° C., the Cu—Ga alloy powder is not sufficiently sintered, resulting in a sintered body with many voids. When sputtering is performed using a sintered body having a large number of pores as a sputtering target, abnormal discharge or splash occurs. When temperature is higher than 830 degreeC, a liquid phase will appear and it will become impossible to produce a sintered compact. Therefore, by setting the temperature of the hot press to 250 ° C. to 836 ° C., liquid leakage does not occur and a sintered body with few voids can be produced.

  The press pressure of the hot press is 5 MPa to 30 MPa. When the pressing pressure is lower than 5 MPa, the sintering of the Cu—Ga alloy powder is insufficient and a sintered body with many voids is obtained. When the pressing pressure is increased, the sintered body is increased in density by decreasing the number of pores, but the density hardly increases even if the pressure is higher than 30 MPa. When trying to press at a press pressure higher than 30 MPa, the press die needs to be changed to a special material or large electric power is required.

  In the sintering process, the Cu-Ga alloy powder is not taken out from the hot press apparatus used in the heat treatment process, and pressure sintering is performed in the same hot press apparatus following the heat treatment process, and the temperature of the hot press is set as the heat treatment in the heat treatment process. The temperature is preferably the same. When heat treatment and sintering are performed with the same hot press apparatus, it is not necessary to prepare a separate heat treatment apparatus for the heat treatment step, and cooling time after the heat treatment is unnecessary. In the sintering step, by setting the hot press temperature to the same temperature as the heat treatment, a press pressure is applied subsequent to the heat treatment, so that the sintering can be easily performed. In the sintering process, the heat treatment and the sintering are performed in the same hot press apparatus, whereby the composition of the Cu—Ga alloy sputtering target can be prevented from changing and the yield can be prevented from being lowered.

(Finishing process)
In the finishing step, the surface of the sintered body of the Cu—Ga alloy obtained in the sintering step is finished to a flat surface by grinding and bonded to a Cu backing plate to obtain a Cu—Ga alloy sputtering target.

  In the manufacturing method of the Cu—Ga alloy sputtering target as described above, the Ga concentration is as high as 30 mass% to 45 mass%, the average crystal grain size is 20 μm or less, the area ratio of the γ phase group is 95 area% or more, A Cu—Ga alloy sputtering target having a rate of 1% or less and a three-point bending strength of 200 MPa or more can be produced without cracks during production, and the obtained Cu—Ga alloy sputtering target is cracked or chipped during sputtering. In addition, abnormal discharge and generation of particles can be prevented.

  Moreover, in the manufacturing method of a Cu-Ga alloy sputtering target, when producing Cu-Ga alloy powder used as the raw material of a sputtering target, Cu powder is temperature of 150 to 300 degreeC in the mixed gas atmosphere containing hydrogen gas. , The reactivity of the surface of the Cu powder with Ga increases, and the reaction between the Cu powder and Ga is sufficiently performed. As a result, the obtained Cu—Ga alloy powder has a uniform Cu—Ga intermetallic compound layer in which the Ga concentration is high and the variation in Ga concentration is suppressed within 3.0 mass% on the surface of the Cu powder. The

  In the method for producing a Cu—Ga alloy sputtering target, the Cu particle surface is obtained by heat-treating the Cu—Ga alloy powder in which the variation in Ga concentration is suppressed at a temperature of 250 ° C. to 836 ° C. in a vacuum or an inert gas atmosphere. It can be suppressed that Ga in the Cu-Ga intermetallic compound layer and Cu inside the particles are interdiffused to lower the Ga concentration on the surface of the Cu particles and to generate a Ga liquid phase during sintering.

  Thus, in the manufacturing method of a Cu-Ga alloy sputtering target, by using the Cu-Ga alloy powder in which the variation in Ga concentration is suppressed as a raw material, the Cu-Ga alloy powder is subjected to heat treatment before sintering. In the sintering step, sintering proceeds without causing a Ga liquid phase during sintering by hot pressing, and a sputtering target in which variation in Ga concentration is suppressed can be manufactured. The Cu—Ga alloy sputtering target obtained by this method for producing a Cu—Ga alloy sputtering target is of a high quality having a uniform composition with a variation in Ga concentration within 3.0 mass%.

  Specific examples to which the present invention is applied will be described below, but the present invention is not limited to these examples.

<Example 1>
[Stirring process]
First, in the stirring step as the first step, electrolytic Cu powder (average particle size 100 μm, BET 0.088 m ² / g, Fe, Cr, Ni each less than 1 ppm, oxygen: 0.16% by mass, 650 g of carbon (0.011% by mass) was charged into a biaxial planetary type 5 L mixing and stirring device (5XDmv-rr type manufactured by Kodaira Seisakusho) equipped with a TiN coating container and a stirring bar. The inside of the container was evacuated to a vacuum of 100 Pa or less (oxygen partial pressure of 20 Pa or less), and then replaced with a mixed gas of hydrogen and nitrogen (hydrogen gas concentration 1%). Cooled to ° C.

[Alloy powder production process]
Next, in the alloy production process as a second process, the inside of the container was evacuated to a vacuum degree of 50 Pa or less (oxygen partial pressure of 10 Pa or less) and then replaced with Ar gas. Liquid Ga in which Ga (Fe, Cr, Ni each less than 1 ppm, oxygen less than 0.01% by mass, carbon less than 0.001% by mass) was heated to 50 ° C. was put in a container containing Cu powder in an amount of 350 g (Ga (Mixing ratio 35% by mass). It was kept at 150 ° C. for 1 hour with stirring. When the Cu—Ga alloy powder taken out after cooling to room temperature was observed with a microscope, the surface of the Cu powder was alloyed to become grayish white, and no unreacted Cu powder not covered with the Cu—Ga alloy was observed. . Three samples of 1 g of alloy powder were collected and the Ga concentration was examined by ICP analysis (Inductively Coupled Plasma Mass Spectrometry). The minimum was 34.4% and the maximum was 35.8% by mass. Was as small as 1.4% by mass.

[Heat treatment process]
Next, in the heat treatment step as the third step, 100 g of Cu—Ga alloy powder was set in a graphite mold having an inner diameter of 50 mm for hot pressing, and attached to a hot pressing apparatus (manufactured by Daia Vacuum Co., Ltd.). While the inside of the apparatus was evacuated to 50 Pa or less (oxygen partial pressure of 10 Pa or less), the press pressure was heated in an unloaded state, and heat treatment was performed at a temperature of 750 ° C. for 1 hour.

[Sintering process]
Subsequently, in the sintering step as the fourth step, a press pressure of 30 MPa was applied while maintaining the temperature at 750 ° C., and hot pressing was performed for 1 hour, and a sintered body (target material) having a diameter of 50 mm and a thickness of 6 mm was taken out. . In Example 1, cracks did not occur when the sintered body was manufactured.

[Evaluation]
A plurality of sintered bodies were produced by the same method, and these sintered bodies were used for optical microscope observation, EPMA analysis, X-ray diffraction measurement, three-point bending strength measurement, oxygen content analysis, and sputter film formation.

(Half width)
A surface having a diameter (φ) of 50 mm corresponding to the sputtered surface of the sintered body was measured using an X-ray diffractometer (Specter Corp., X′PertPRO / MPD). As a result, 2θ is 36, 39, 44, 49, 51, 53, 58 and 64 deg. There are diffraction peaks at nearby positions, and the (222) plane, (321) plane, (330) plane, (332) plane, (422) plane, (510) plane, (521) plane, ( 600) plane. The half-value widths of the diffraction peaks on the eight faces of the γ phase group are as shown in Table 1. The average half-width of the diffraction peaks of these eight surfaces is 0.26 deg. It was big. Here, the half width was obtained by performing peak separation of Cu-Kα1 and Kα2 and extracting a diffraction peak only from the Cu-Kα1 line.

(Orientation index)
Orientation degree of (222) plane, (321) plane, (330) plane, (332) plane, (422) plane, (510) plane, (521) plane, (600) plane of γ phase group in X-ray diffraction The indices are as shown in Table 2. In all the planes, the orientation degree index was 1.5 or less, which was close to 1, so it was found that the crystal orientation was small. Further, a diffraction peak of a metal phase different from the γ phase group was not observed.

(Porosity)
A surface having a diameter (φ) of 50 mm corresponding to the sputter surface of the sintered body was polished. When the polished surface is observed with an optical microscope, it can be seen that the color tone is uniform and is composed of a simple metal phase as shown in FIG. Moreover, it turns out that there is almost no void | hole and it is dense. As for the porosity, the area ratio was obtained by extracting the void portion from the images of five different fields of view obtained by photographing the polished surface at 200 times using image analysis software ImageJ. As a result, the porosity was as extremely low as 0.007%.

(Average crystal grain size)
When switched to polarization observation so that crystal grains could be observed, a small grain structure was obtained. A line segment was drawn on a polarization microscope image of five different fields taken at 200 times, the number of crystal grains crossing the line segment was determined, and the average crystal grain size was determined by dividing the line segment length by this number of particles. . As a result, the average crystal grain size was 13 μm.

(Area ratio)
From the secondary electron image, backscattered electron image, and quantitative analysis using an EPMA analyzer (JXA-8100 manufactured by JEOL Ltd.), the γ phase group of the polished surface corresponding to the sputtered surface of this sintered body is identified, and the image From this, the area ratio was determined. The area ratio was 99.9 area%, which was found to be composed of a simple metal phase.

(Uniformity of sputtering target)
EPMA analysis was performed to analyze the Ga concentration at six locations on the polished surface corresponding to the sputtering surface. As a result, the minimum was 34.5% by mass, the maximum was 35.4% by mass, the difference between the maximum and minimum was 0.9% by mass, and the target was uniform in composition.

(Oxygen content)
As a result of analyzing the oxygen content of the sintered body by an inert gas melting-infrared absorption method, the oxygen content was as small as 0.04% by mass.

(3-point bending strength)
Five test pieces of 30 mm x 4 mm x 3 mm are cut out from the sintered body, and a three-point bending test is performed in accordance with the method described in JIS R1601 (Test method for fine ceramic room temperature bending strength). It was 271 Mpa when the average value of intensity | strength was computed.

  The above results are shown in Tables 3 and 4.

[Preparation of sputtered film]
Next, the sintered body was ground and joined to a Cu backing plate to prepare a Cu—Ga alloy sputtering target. This was attached to a sputtering device (SH450 manufactured by ULVAC), evacuated to 1.0 × 10 ⁻⁴ Pa or less, Ar gas (purity: 99.99%) was introduced, Ar gas pressure 0.5 Pa, DC 100 W Sputtering was performed under the following conditions to form a sputtered film. As a result of counting the average abnormal discharge for 1 minute using a micro arc monitor (manufactured by Landmark Technology Co., Ltd.), the average value was 0 times / minute, and it was found to be a good target without abnormal discharge. Further, the Cu—Ga alloy sputtering target was not cracked during sputtering.

(particle)
Using this Cu-Ga alloy sputtering target, the sputtered film formed on the Si wafer substrate having a diameter of 3 inches was observed with an optical microscope, and the number of film defects to which splash or particles adhered was obtained. / Cm ² and there was no film defect.

(Deposition rate)
The deposition rate obtained from the thickness of the sputtered film deposited on the soda lime glass substrate and the deposition time was 10.2 nm / min.

(Membrane uniformity)
The composition of the sputtered film was subjected to EPMA analysis at five locations on the polished surface corresponding to the sputtered surface. As a result, the minimum was 34.7% by mass and the maximum was 35.2% by mass. It was found to be an extremely small and uniform film of mass%.

(Deposition time and consumption rate)
As a result of measuring the surface roughness of the erosion deepest part of the target using an optical profiler (NewView 6200 manufactured by Zygo) at the time when the sputter integration time was 10 hours, the average roughness Ra was 0.89 μm. The target consumption rate determined from the ratio of the weight of the target decreased by the sputtering integrated time of 10 hours and the target weight before sputtering was 17%.

  The above results are shown in Table 4, Table 5, and Table 6.

<Example 2>
In Example 2, a Cu—Ga alloy sintered body was produced in the same manner as in Example 1 except that 700 g of electrolytic Cu powder, 300 g of Ga, the heat treatment step in the third step, and the sintering step in the fourth step were set to 830 ° C. did. When the produced Cu—Ga alloy sintered body was subjected to X-ray diffraction analysis, in addition to the diffraction peak of the γ phase group, a small diffraction peak of another metal phase considered to be a β phase was also mixed. The half width of the γ phase group is as shown in Table 1, and the orientation index is as shown in Table 2. Moreover, about the Cu-Ga alloy sintered compact, the result of having performed optical microscope observation, EPMA analysis, X-ray diffraction measurement, three-point bending strength measurement, and oxygen content analysis similarly to Example 1 is shown in Table 3, Table 4. Show.

  Next, the results of producing and sputtering a Cu—Ga alloy sputtering target using a Cu—Ga alloy sintered body in the same manner as in Example 1 are shown in Table 4, Table 5, and Table 6.

<Example 3>
In Example 3, a Cu—Ga alloy sintered body was produced in the same manner as in Example 1 except that 600 g of electrolytic Cu powder, 400 g of Ga, the heat treatment step in the third step, and the sintering step in the fourth step were set to 400 ° C. did. Tables 3 and 4 show the results of performing optical microscope observation, EPMA analysis, X-ray diffraction measurement, three-point bending strength measurement, and oxygen content analysis on the Cu—Ga alloy sintered body in the same manner as in Example 1. Next, Table 4, Table 5, and Table 6 show the results of producing and sputtering a Cu—Ga alloy sputtering target using a Cu—Ga alloy sintered body in the same manner as in Example 1.

<Reference Example 1>
In Reference Example 1, 650 g of electrolytic copper and 350 g of Ga pieces were placed in a graphite crucible and set in a vacuum melting furnace (manufactured by Daia Vacuum). After the inside of the furnace was evacuated to 9.0 × 10 ⁻³ Pa or less, Ar gas was introduced so as to be 27 kPa. In this state, the graphite crucible was heated using a high-frequency power source, electrolytic copper and Ga were dissolved, and poured into a graphite mold for casting. The cast ingot was pulverized with a jaw crusher in an Ar gas atmosphere to prepare a Cu—Ga alloy powder.

  Next, 100 g of Cu—Ga alloy powder was set in a graphite mold with an inner diameter of 50 mm for hot pressing, and attached to a hot pressing apparatus (manufactured by Daia Vacuum Co., Ltd.). While the inside of the apparatus is evacuated to 50 Pa or less (oxygen partial pressure of 10 Pa or less), it is hot-pressed under the conditions of a press pressure of 30 MPa, a temperature of 750 ° C., and an hour holding, and a sintered body (target material) having a diameter of 50 mm and a thickness of 6 mm Was taken out.

  The half width of the produced Cu—Ga alloy sintered body is as shown in Table 1, and the orientation degree index is as shown in Table 2.

  Tables 3 and 4 show the results of performing optical microscope observation, EPMA analysis, X-ray diffraction measurement, three-point bending strength measurement, and oxygen content analysis on the sintered body in the same manner as in Example 1. Tables 4, 5, and 6 show the results of sputtering and producing a sputtering target in the same manner as in Example 1.

<Reference Example 2>
In Comparative Example 2, a sintered body and a sputtering target were produced in the same manner as in Reference Example 1 except that 570 g of electrolytic copper, 430 g of Ga pieces, and a hot press temperature of 250 ° C. were used.

  Tables 3 and 4 show the results of performing optical microscope observation, EPMA analysis, X-ray diffraction measurement, three-point bending strength measurement, and oxygen content analysis on the sintered body in the same manner as in Example 1. Tables 4, 5, and 6 show the results of sputtering and producing a sputtering target in the same manner as in Example 1.

  As described above, from the results shown in Table 3, the sputtering targets of Examples 1 to 3 have a porosity of 1% or less, an average crystal grain size of 20 μm or less, and an area ratio of the γ phase group of 95.0 area% or more. This indicates that it is dense, has a fine average crystal grain size and a simple metal phase, and has a strong three-point bending strength of 200 MPa or more.

  From Tables 1 and 2, the sputtering targets of Examples 1 to 3 have an average half width of 0.13 deg. As described above, it has a full width at half maximum by X-ray diffraction, an orientation degree index of 1.5 or less, and it can be seen that there is almost no crystal orientation. Table 4 shows that the composition of the sputtering target is uniform because the oxygen content is as low as 0.2% or less and the difference in Ga concentration is as small as 3.0% by mass or less. From Tables 4 and 5, it can be seen that if sputtering is performed using the sputtering targets of Examples 1 to 3, a uniform sputtered film can be formed without cracking the sputtering target. Also, from Table 5, the sputtering targets of Examples 1 to 3 do not generate abnormal discharge because the porosity is 1% or less, the average crystal grain size is 20 μm or less, and the three-point bending strength is Since it is 200 MPa or more, it turns out that erosion roughness becomes small and smooth, and a sputtered film with few film defects can be formed. Further, from Table 6, since the sputtering targets of Examples 1 to 3 have an orientation degree index of 8 faces of the γ phase group of 1.5 or less, the film formation speed is high, the target consumption is small, and the productivity is high. Is high.

  On the other hand, in Reference Example 1, since the average crystal grain size is larger than 20 μm and the three-point bending strength is smaller than 200 MPa, cracks occur during sputtering, the erosion roughness is large, and the surface of the sputtering target is not smooth. There was no particle on the film.

  In Reference Example 2, since the average crystal grain size was larger than 20 μm and the three-point bending strength was smaller than 200 MPa, cracks occurred during sputtering. Further, in Reference Example 2, since the area ratio of the γ phase group was less than 95 area%, film uniformity could not be obtained. Furthermore, in Reference Example 2, since the porosity was larger than 1%, cracks occurred and abnormal discharge also occurred.

  From the examples and reference examples described above, the porosity of the Cu—Ga alloy sputtering target is 1% or less, the average crystal grain size is 20 μm or less, the area ratio of the γ phase group is 95% by area or more, and the porosity is 1 % And a three-point bending strength of 200 MPa or more, even if the Ga concentration is as high as 30% to 45% by mass, no abnormal discharge during cracking or sputtering occurs, and no particles are generated in the film. Therefore, a sputtered film having a uniform composition can be formed.

Claims (4)

A Cu-Ga alloy sputtering target having a Ga concentration of 30 mass% to 45 mass%,
The average crystal grain size is 20 μm or less, the area ratio of the group consisting of γ ₁ phase, γ ₂ phase, γ ₃ phase and γ phase is 95 area% or more, the porosity is 1% or less, and the three-point bending strength is 200 MPa or more. Cu-Ga alloy sputtering target characterized by the above-mentioned. (222) plane, (321) plane, (330) plane, (332) plane, (422) plane, (510) of the group consisting of γ ₁ phase, γ ₂ phase, γ ₃ phase and γ phase in X-ray diffraction The Cu-Ga alloy sputtering target according to claim 1, wherein an orientation degree index K _(hkl) obtained from the following formulas of the plane, the (521) plane, and the (600) plane is 1.5 or less.
K _(hkl) = (I _(hkl) / ΣI _(hkl) ) / ( _{ID (hkl)} / ΣID _(hkl) )
Where I _(hkl) is the measured diffraction peak intensity of the (hkl) plane of the group,
_{ID (hkl)} is the diffraction peak intensity of the (hkl) plane of the γ phase indicated by 71-0458 in the ICDD card data as standard data,
ΣI _(hkl) and ΣID _(hkl) are
ΣI _(hkl) = I ₍₂₂₂₎ + I ₍₃₂₁₎ + I ₍₃₃₀₎ + I ₍₃₃₂₎
+ I ₍₄₂₂₎ + I ₍₅₁₀₎ + I ₍₅₂₁₎ + I ₍₆₀₀₎
ΣI _{D (hkl)} = _{ID (222)} + _{ID (321)} + _{ID (330)}
+ _{ID (332)} + _{ID (422)} + _{ID (510)}
+ _{ID (521)} + _{ID (600)}
It is.   The Cu-Ga alloy sputtering target according to claim 1 or 2, wherein the oxygen content is 0.2 mass% or less.   The Cu-Ga alloy sputtering target according to any one of claims 1 to 3, wherein variation in Ga concentration is 3.0 mass% or less.

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