COPPER ALLOY SPUTTERING TARGET AND METHOD FOR MANUFACTURING SAME

Abstract

Provided is a copper alloy sputtering target, wherein, based on charged particle activation analysis, the copper alloy sputtering target has an oxygen content of 0.6 wtppm or less, or an oxygen content of 2 wtppm or less and a carbon content of 0.6 wtppm or less. Additionally provided is a method for manufacturing a copper alloy sputtering target, wherein a copper raw material is melted in a vacuum or an inert gas atmosphere, a reducing gas is thereafter introduced into the melting atmosphere, an alloy element is subsequently added to a molten metal for alloying, and an obtained ingot is processed into a target shape. The present invention aims to provide a copper alloy sputtering target that generates few particles during sputtering, and a method for manufacturing such a sputtering target.

Claims

1. A copper alloy sputtering target, wherein, based on charged particle activation analysis, the copper alloy sputtering target has an oxygen content of 0.6 wtppm or less, or an oxygen content of 2 wtppm or less and a carbon content of 0.6 wtppm or less.

2. The copper alloy sputtering target according to claim 1, wherein an alloy element is one or more types of elements having a greater affinity for oxygen or carbon than Cu.

3. A method for manufacturing a copper alloy sputtering target, wherein a copper raw material is melted in a vacuum or an inert gas atmosphere, a reducing gas is thereafter introduced into the melting atmosphere, an alloy element is subsequently added to a molten metal for alloying, and an obtained alloy ingot is processed into a target shape.

4. The method for manufacturing a copper alloy sputtering target according to claim 3, wherein the reducing gas is made of hydrogen or carbon monoxide.

5. The method for manufacturing a copper alloy sputtering target according to claim 4, wherein the melting process is performed via plasma arc melting, electron beam melting, or induction melting.

6. The method for manufacturing a copper alloy sputtering target according to claim 5, wherein each melting processing step is performed in a different crucible.

7. The method for manufacturing a copper alloy sputtering target according to claim 6, wherein copper is placed into a water-cooled copper crucible and melted via plasma arc melting in an argon atmosphere, a hydrogen gas is thereafter introduced into the melting atmosphere, a molten metal is placed into a subsequent-stage water-cooled copper crucible, an alloy element is thereafter added thereto for alloying via plasma arc melting, an obtained ingot is subject to forging, rolling, and heat treatment to prepare a sputtering target material, and the prepared target material is machined and processed into a target shape.

8. The method for manufacturing a copper alloy sputtering target according to claim 3, wherein the melting process is performed via plasma arc melting, electron beam melting, or induction melting.

9. The method for manufacturing a copper alloy sputtering target according to claim 3, wherein each melting processing step is performed in a different crucible.

10. The method for manufacturing a copper alloy sputtering target according to claim 3, wherein copper is placed into a water-cooled copper crucible and melted via plasma arc melting in an argon atmosphere, a hydrogen gas is thereafter introduced into the melting atmosphere, a molten metal is placed into a subsequent-stage water-cooled copper crucible, an alloy element is thereafter added thereto for alloying via plasma arc melting, an obtained ingot is subject to forging, rolling, and heat treatment to prepare a sputtering target material, and the prepared target material is machined and processed into a target shape.

Description

DESCRIPTION OF EMBODIMENTS

[0014] The copper alloy sputtering target of the present invention is characterized in that, based on charged particle activation analysis, the copper alloy sputtering target has an oxygen content of 0.6 wtppm or less, or an oxygen content of 2 wtppm or less and a carbon content of 0.6 wtppm or less. Conventionally, known are techniques of melting a copper raw material to eliminate impurities such as metals and gasses, and thereby prepare high-purity copper. However, when attempting to prepare a high-purity copper alloy, there were cases where the oxygen or carbon contained in the copper would transfer to the alloy element, and remain therein. The present invention is able to reduce oxygen and carbon in the copper alloy extremely effectively by devising the manufacturing method.

[0015] The term “charged particle activation analysis” as used herein is one method of chemical analysis, in which a sample is irradiated with deuteron rays, neutron rays or γ rays to radioactivate the sample, and the radioisotope thereof is traced to perform a qualitative and quantitative analysis of the various elements contained in the sample. The present invention is able to significantly reduce the oxygen or carbon contained in the copper alloy sputtering target, and consequently effectively suppress the generation of particles during sputtering. Note that the quantitative lower limit based on the foregoing analyzing method is as follows; specifically, oxygen: 0.1 wtppm; carbon: 0.1 wtppm.

[0016] It goes without saying that the copper alloy of the present invention has a high purity, and the purity is preferably 99.999 wt % (5N) or higher. The purity is obtained by measuring the content of metal impurities excluding copper and alloy elements contained in the target via glow-discharge mass spectrometry (GDMS), and applying the subtracting method (deeming the result of subtracting metal impurities from 100 wt % as the purity wt %). The impurities are Ag, Al, Ca, Cr, Fe, K, Na, Ni, P, S, Th, and U.

[0017] As the alloy element configuring the copper alloy sputtering target of the present invention, preferably used is one or more types of elements having a higher affinity for oxygen or carbon in comparison to copper. For instance, considered may be Al, Mn, Co, Ni, Mg, Ti, Si, In, Sn, Ge, Bi, B, Cr, Nd, Zr, La, Er, Gd, Dy, Yb, Lu, Hf, and Ta. These alloy elements are well-known materials capable of improving the wiring properties of semiconductor devices, and a plurality of materials may also be combined and added to improve the properties. While the additive amount of these elements will differ depending on the required properties, for instance, the additive amount is preferably 0.1 to 15.0 at % for Al, and 0.1 to 30.0 at % for Mn.

[0018] The method of manufacturing the copper alloy sputtering target of the present invention is now explained. Foremost, copper and an alloy material (Al, Mn or the like) are prepared as the raw materials. These raw materials preferably have the highest purity possible, and it would be effective to use copper having a purity of 6N or higher, and an alloy element having a purity of 4N or higher. Subsequently, these raw materials are weighed to achieve the intended composition, and thereafter only the copper raw material is placed into a water-cooled copper crucible (including a hearth). While alumina, magnesia, graphite and other refractories are used as the crucible material, since they may get incorporated as impurities in the molten metal, it would be favorable to use copper having the same quality as the material to be subject to melting. Consequently, even if the crucible material becomes melted and gets mixed into the molten metal, it will not become an impurity.

[0019] Subsequently, the copper is melted in a vacuum or an inert gas (Ar, He or the like) atmosphere. Here, the volatilization of components can be suppressed by melting the copper in an inert gas atmosphere. Melting may be performed via plasma arc melting, electron beam melting, induction melting or the like. A reducing gas (hydrogen, carbon monoxide or the like) is thereafter introduced into the melting atmosphere. It is thereby possible to effectively eliminate the oxygen contained in the copper. As the amount of gas to be introduced, when adopting the plasma melting method, 0.1 to 20 vol % of reducing gas is preferably added to the inert gas. When adopting the electron beam melting method, the reducing gas is preferably introduced into the vacuum at a flow rate of 400 ml/min or more.

[0020] Here, the reducing gas is preferably added after melting the copper in a vacuum or an inert gas atmosphere and sufficiently desorbing the oxygen and carbon contained in the copper as carbon monoxide. After sufficiently eliminating carbon, excess oxygen can be desorbed as vapor (H.sub.2O) or carbon dioxide (CO.sub.2) by using the reducing gas, and carbon and oxygen contained as impurities in the copper can be reduced extremely effectively. Needless to say, the present invention is not restricting the addition of the reducing gas at a relatively early stage of melting copper (stage where carbon has not yet been sufficiently eliminated).

[0021] Subsequently, the obtained molten metal of copper is placed into a subsequent-stage water-cooled copper crucible (including a hearth), an alloy element is added, and a copper alloy is obtained via plasma arc melting, electron beam melting, induction melting or the like. What is particularly important is that the alloy element is added to the molten metal of copper after the elimination of oxygen and carbon, and then melted. If the alloy element is added to copper before the degassing process and then melted, the oxygen and carbon contained in the copper are incorporated into the alloy element and form oxides and carbides, and, even after the melting, these impurities will remain in the alloy ingot. Accordingly, the timing of adding the alloy element is extremely important.

[0022] Subsequently, the molten metal of copper alloy is placed into a water-cooled copper mold and melted via induction melting or the like, and the solidified ingot is extracted from the bottom of the mold. The surface layer of the prepared ingot is thereafter removed, and the ingot is subject to plastic working and heat treatment to produce a sputtering target material. Furthermore, the produced target material is machined and processed into a predetermined target shape so as to obtain a copper alloy sputtering target.

EXAMPLES

[0023] The present invention is now explained based on the Examples. The Examples indicated below are provided for facilitating the understanding of the present invention, and the present invention is not limited by these Examples. In other words, modifications and other examples based on the technical concept of the present invention are also covered by the present invention as a matter of course.

Example 1

[0024] Cu having a purity of 6N or higher was prepared, and the Cu was placed into a water-cooled copper hearth and melted via plasma arc melting of being irradiated with plasma in an argon atmosphere with 4 vol % of hydrogen introduced therein. Subsequently, the resulting molten metal was placed into another water-cooled copper hearth, and Al having a purity of 4N or higher was added to achieve an amount of 1 at %, and melted via plasma arc melting. Subsequently, the molten metal of copper alloy was poured into a water-cooled copper mold and melted via vacuum induction melting, and the solidified ingot was extracted from the bottom of the mold.

[0025] Subsequently, the obtained ingot was processed into a size having a diameter of 180 mm× thickness of 160 mm, thereafter subject to hot forging at 700° C., and additionally subject to cold rolling until the size became a diameter of 460 mm×thickness of 24.5 mm. This was thereafter subject to heat treatment at 400° C., and rapidly cooled to prepare a rolled plate. The rolled plate was machined to manufacture a sputtering target having a diameter of 440 mm and a thickness of 16.5 mm, and the manufactured sputtering target was bonded with a backing plate via diffusion bonding.

[0026] The impurity concentration in a part cut out of the ingot was examined. Note that metal components were measured using GDMS, and gas components (oxygen, carbon) were measured using charged particle activation analysis. Consequently, the total content of metal impurities was 1 wtppm or less, and, with regard to the gas components, the carbon content was 0.7 wtppm and the oxygen content was 0.3 wtppm. In particular, the concentration of oxygen as a gas component could be reduced considerably.

[0027] Sputtering was performed up to 100 kWh using the obtained target to deposit a film on a 12-inch silicon substrate at an input power of 38 kW for 5 seconds. As a result of measuring the number of particles having a size of 0.088 μm or larger in the deposited film, the result was favorable at 8 particles. Subsequently, as a result of measuring the number of particles on the substrate with regard to the respective Life positions of 200, 300, 500, and 800 kWh, the result was favorable at 10 particles or less throughout the entire Life of the target.

Example 2

[0028] Cu having a purity of 6N or higher was prepared, and the Cu was placed into a water-cooled copper hearth and melted via plasma arc melting of being irradiated with plasma in an argon atmosphere. Subsequently, 4 vol % of hydrogen was introduced into the melting atmosphere, and the Cu was further melted. Subsequently, the resulting molten metal was placed into a subsequent-stage water-cooled copper hearth, and Al having a purity of 4N or higher was added to achieve an amount of 1 at %, and melted via plasma arc melting. Subsequently, the molten metal of copper alloy was poured into a water-cooled copper mold and melted via vacuum induction melting, and the solidified ingot was extracted from the bottom of the mold.

[0029] Subsequently, the obtained alloy ingot was processed into a sputtering target according to the same method and conditions as Example 1, and the target was bonded with a backing plate via diffusion bonding. As a result of examining the impurity concentration in a part cut out of the ingot, the total content of metal impurities was 1 wtppm or less, and, with regard to the gas components, the carbon content was 0.2 wtppm and the oxygen content was 0.3 wtppm. The concentration of both carbon and oxygen as gas components could be reduced considerably. Furthermore, sputtering was performed using the obtained target in the same manner as Example 1, and the number of particles was measured. The result was favorable at 8 particles or less throughout the enter Life of the target.

Example 3

[0030] Cu having a purity of 6N or higher was prepared, and the Cu was placed into a water-cooled copper hearth and melted via electron beam melting in an atmosphere where hydrogen was introduced into a vacuum at a flow rate of 400 ml/min or more. Subsequently, the resulting molten metal was placed into a subsequent-stage water-cooled copper hearth, and high-purity Al having a purity of 4N or higher was added to achieve an amount of 1 at %, and melted via electron beam melting. Subsequently, the molten metal of copper alloy was poured into a water-cooled copper mold and melted via vacuum induction melting, and the solidified ingot was extracted from the bottom of the mold.

[0031] Subsequently, the obtained alloy ingot was processed into a sputtering target according to the same method and conditions as Example 1, and the target was bonded with a backing plate via diffusion bonding. As a result of examining the impurity concentration in a part cut out of the ingot, the total content of metal impurities was 1 wtppm or less, and, with regard to the gas components, the carbon content was 0.6 wtppm and the oxygen content was 0.8 wtppm. In particular, the concentration of carbon as a gas component could be reduced considerably. Furthermore, sputtering was performed using the obtained target in the same manner as Example 1, and the number of particles was measured. The result was 12 particles or less throughout the enter Life of the target. The results are shown in Table 1.

Example 4

[0032] Cu having a purity of 6N or higher was prepared, and the Cu was placed into a water-cooled copper hearth and melted via electron beam melting in a vacuum. Subsequently, hydrogen was introduced into the melting atmosphere at a flow rate of 400 ml/min or more, and the Cu was further melted. Subsequently, the resulting molten metal was placed into a subsequent-stage water-cooled copper hearth, and high-purity Al having a purity of 4N or higher was added to achieve an amount of 1 at %, and melted via electron beam melting. Subsequently, the molten metal of copper alloy was poured into a water-cooled copper mold and melted via vacuum induction melting, and the solidified ingot was extracted from the bottom of the mold.

[0033] Subsequently, the obtained alloy ingot was processed into a sputtering target according to the same method and conditions as Example 1, and the target was bonded with a backing plate via diffusion bonding. As a result of examining the impurity concentration in a part cut out of the ingot, the total content of metal impurities was 1 wtppm or less, and, with regard to the gas components, the carbon content was 0.2 wtppm and the oxygen content was 0.9 wtppm. In particular, the concentration of carbon as a gas component could be reduced considerably. Furthermore, sputtering was performed using the obtained target in the same manner as Example 1, and the number of particles was measured. The result was 10 particles or less throughout the enter Life of the target. The results are shown in Table 1.

TABLE-US-00001 TABLE 1 Alloy Method O value by C value by com- of adding radioactivation radioactivation Number of Alloy position Melting alloy analysis analysis sputtering Element at % method Used gas element wtppm wtppm particles Example 1 Al 1 Plasma melting Ar + H.sub.2 Added after 0.3 0.7 10 particles mixing or less Example 2 Al 1 Plasma melting Ar     Ar + H.sub.2 Added after 0.3 0.2  8 particles mixing or less Example 3 Al 1 Electron beam H.sub.2 Added after 0.8 0.6 12 particles melting mixing or less Example 4 Al 1 Electron beam Vacuum     H.sub.2 Added alter 0.9 0.2 10 particles melting mixing or less Example 5 Al 2 Plasma melting Ar + H.sub.2 Added alter 0.4 0.7 12 particles mixing or less Example 6 Al 2 Plasma melting Ar     Ar + H.sub.2 Added after 0.4 0.3  7 particles mixing or less Example 7 Al 2 Electron beam H.sub.2 Added after 0.9 0.5 13 particles melting mixing or less Example 8 Al 2 Electron beam Vacuum     H.sub.2 Added after 1 0.2  8 particles melting mixing or less Example 9 Al 4 Plasma melting Ar + H.sub.2 Added after 0.4 1  9 particles mixing or less Example 10 Al 4 Plasma melting Ar     Ar + H.sub.2 Added after 0.4 0.4  7 particles mixing or less Example 11 Al 4 Electron beam H.sub.2 Added after 0.9 0.6 12 particles melting mixing or less Example 12 Al 4 Electron beam Vacuum     H.sub.2 Added after 1 0.2 11 particles melting mixing or less Example 13 Mn 1 Plasma melting Ar + H.sub.2 Added after 0.2 0.5  7 particles mixing or less Example 14 Mn 1 Plasma melting Ar     Ar + H.sub.2 Added after 0.3 0.2  5 particles mixing or less Example 15 Mn 1 Electron beam H.sub.2 Added after 1 0.4  8 particles melting mixing or less Example 16 Mn 1 Electron beam Vacuum     H.sub.2 Added after 1 0.1  7 particles melting mixing or less Example 17 Mn 2 Plasma melting Ar + H.sub.2 Added after 0.3 0.4  6 particles mixing or less Example 18 Mn 2 Plasma melting Arm     + H.sub.2 Added after 0.2 0.1  5 particles mixing or less Example 19 Mn 2 Electron beam H.sub.2 Added after 0.9 0.5  9 particles melting mixing or less Example 20 Mn 2 Electron beam Vacuum     H.sub.2 Added after 1 0.2  5 particles melting mixing or less Example 21 Mn 4 Plasma melting Ar + H.sub.2 Added after 0.3 0.4  8 particles mixing or less Example 22 Mn 4 Plasma melting Ar     Ar + H.sub.2 Added after 0.2 0.2  5 particles mixing or less Example 23 Mn 4 Electron beam H.sub.2 Added after 0.9 0.6  8 particles melting mixing or less Example 24 Mn 4 Electron beam Vacuum     H.sub.2 Added after 2 0.2  7 particles melting mixing or less Comparative Al 1 Plasma melting Ar Added after 10 0.2 Up to 30 Example 1 mixing particles Comparative Al 1 Plasma melting Ar + H.sub.2 Added before 0.8 0.9 Up to 20 Example 2 mixing particles Comparative Al 1 Plasma melting Ar     Ar + H.sub.2 Added before 1 0.9 Up to 19 Example 3 mixing particles Comparative Al 1 Electron beam H.sub.2 Added before 3 1 Up to 23 Example 4 melting mixing particles Comparative Al 1 Electron beam Vacuum Added after 4 0.2 Up to 26 Example 5 melting mixing particles Comparative Al 2 Plasma melting Ar Added after 17 0.3 Up to 28 Example 6 mixing particles Comparative Al 2 Plasma melting Ar + H.sub.2 Added before 1 2 Up to 23 Example 7 mixing particles Comparative Al 2 Plasma melting Ar     Ar + H.sub.2 Added before 1 1 Up to 21 Example 8 mixing particles Comparative Al 2 Electron beam H.sub.2 Added before 5 2 Up to 27 Example 9 melting mixing particles Comparative Al 2 Electron beam Vacuum Added after 7 0.2 Up to 18 Example 10 melting mixing particles Comparative Al 4 Plasma melting Ar Added after 25 0.3 Up 10 40 Example 11 mixing particles Comparative Al 4 Plasma melting Ar + H.sub.2 Added before 2 2 Up to 31 Example 12 mixing particles Comparative Al 4 Plasma melting Ar     Ar + H.sub.2 Added before 3 2 Up to 22 Example 13 mixing particles Comparative Al 4 Electron beam H.sub.2 Added before 10 2 Up to 30 Example 14 melting mixing particles Comparative Al 4 Electron beam Vacuum Added after 16 0.3 Up to 25 Example 15 melting mixing particles Comparative Mn 1 Plasma melting Ar Added after 5 0.2 Up to 15 Example 16 mixing particles Comparative Mn 1 Plasma melting Ar + H.sub.2 Added before 4 0.4 Up to 18 Example 17 mixing particles Comparative Mn 1 Plasma melting Ar     Ar + H.sub.2 Added before 6 0.5 Up to 14 Example 18 mixing particles Comparative Mn 1 Electron beam H.sub.2 Added before 3 0.8 Up to 17 Example 19 melting mixing particles Comparative Mn 1 Electron beam Vacuum Added after 4 0.1 Up to 14 Example 20 melting mixing particles Comparative Mn 2 Plasma melting Ar Added after 9 0.1 Up 10 21 Example 21 mixing particles Comparative Mn 2 Plasma melting Ar + H.sub.2 Added before 8 0.8 Up to 16 Example 22 mixing particles Comparatiw Mn 2 Plasma melting Ar     Ar + H.sub.2 Added before 8 0.8 Up to 19 Example 23 mixing particles Comparative Mn 2 Electron beam H.sub.2 Added before 6 0.7 Up to 22 Example 24 melting mixing particles Comparative Mn 2 Electron beam Vacuum Added after 6 0.2 Up to 18 Example 25 melting mixing particles Comparative Mn 4 Plasma melting Ar Added after 16 0.2 Up 10 19 Example 26 mixing particles Comparative Mn 4 Plasma melting Ar + H.sub.2 Added before 13 1 Up to 25 Example 27 mixing particles Comparative Mn 4 Plasma melting Ar     Ar + H.sub.2 Added before 11 1 Up to 31 Example 28 mixing particles Comparative Mn 4 Electron beam H.sub.2 Added before 6 1 Up to 23 Example 29 melting mixing particles Comparative Mn 4 Electron beam Vacuum Added after 6 0.2 Up to 16 Example 30 melting mixing particles

Examples 5-12

[0034] As shown in Table 1, the additive amount of Al was changed to 2 at % (Examples 5-8) or 4 at % (Examples 9-12), and alloy ingots and sputtering targets were prepared according to the same method as Example 1, respectively. Consequently, in all cases, the total content of metal impurities was 1 wtppm or less, the carbon content was 1 wtppm or less, and the oxygen content was 1 wtppm or less. The concentration of gas components could be reduced considerably. Furthermore, sputtering was performed using the obtained targets in the same manner as Example 1, and the number of particles was measured. The result was favorable at 13 particles or less throughout the enter Life of the targets.

Examples 13-24

[0035] As shown in Table 1, Mn was used as the additive element, and the additive amount of Mn was changed to 1 at % (Examples 13-16), 2 at % (Examples 17-20), or 4 at % (Examples 21-24), and alloy ingots and sputtering targets were prepared according to the same method as Example 1, respectively. Consequently, in all cases, the total content of metal impurities was 1 wtppm or less, the carbon content was 0.6 wtppm or less, and the oxygen content was 2 wtppm or less. The concentration of gas components could be reduced considerably. Furthermore, sputtering was performed using the obtained targets in the same manner as Example 1, and the number of particles was measured. The result was favorable at 9 particles or less throughout the enter Life of the targets.

Comparative Example 1

[0036] High-purity Cu having a purity of 6N or higher was prepared, and the Cu was placed into a water-cooled copper hearth and melted via plasma arc melting of being irradiated with plasma in an argon atmosphere. Note that a reducing gas was not added. Subsequently, the resulting molten metal was placed into a subsequent-stage water-cooled copper hearth, and high-purity Al having a purity of 4N or higher was added to achieve an amount of 1 at %, and melted via plasma arc melting. Subsequently, the molten metal was poured into a water-cooled copper mold and melted via vacuum induction melting, and the solidified ingot was extracted from the bottom of the mold.

[0037] Subsequently, the obtained ingot was processed into a sputtering target according to the same method and conditions as Example 1, and the target was bonded with a backing plate via diffusion bonding. As a result of examining the impurity concentration in a part cut out of the ingot, with regard to the gas components, the carbon content was 0.2 wtppm and the oxygen content was 10 wtppm. The oxygen value was higher in comparison to the case of introducing hydrogen. Furthermore, sputtering was performed using the obtained target in the same manner as Example 1, and the number of particles was measured. The result was sporadic generation of numerous particles; specifically, up to 30 particles.

Comparative Example 2

[0038] Cu having a purity of 6N or higher and 1 at % of Al having a purity of 5N or higher were prepared and placed in a water-cooled copper hearth, and the Cu and Al were simultaneously melted via plasma arc melting of being irradiated with plasma in an argon atmosphere into which 4 vol % of hydrogen was introduced. Subsequently, the molten metal was poured into a water-cooled copper mold and melted via vacuum induction melting, and the solidified ingot was extracted from the bottom of the mold.

[0039] Subsequently, the obtained alloy ingot was processed into a sputtering target according to the same method and conditions as Example 1, and the target was bonded with a backing plate via diffusion bonding. As a result of examining the impurity concentration in a part cut out of the ingot, with regard to the gas components, the carbon content was 0.9 wtppm and the oxygen content was 0.8 wtppm. The values were slightly higher in comparison to the case of adding Al later. Furthermore, sputtering was performed using the obtained target in the same manner as Example 1, and the number of particles was measured. The result was sporadic generation of numerous particles; specifically, up to 20 particles.

Comparative Example 3

[0040] Cu having a purity of 6N or higher and 1 at % of Al having a purity of 5N or higher were prepared and placed in a water-cooled copper hearth, and the Cu and Al were simultaneously melted via plasma arc melting of being irradiated with plasma in an argon atmosphere. Subsequently, 4 vol % of hydrogen was introduced into the melting atmosphere, and the Cu and Al were further melted. Subsequently, the molten metal was poured into a water-cooled copper mold and melted via vacuum induction melting, and the solidified ingot was extracted from the bottom of the mold.

[0041] Subsequently, the obtained alloy ingot was processed into a sputtering target according to the same method and conditions as Example 1, and the target was bonded with a backing plate via diffusion bonding. As a result of examining the impurity concentration in a part cut out of the ingot, with regard to the gas components, the carbon content was 0.9 wtppm and the oxygen content was 1 wtppm. The values were slightly higher in comparison to the case of adding Al later. Furthermore, sputtering was performed using the obtained target in the same manner as Example 1, and the number of particles was measured. The result was sporadic generation of numerous particles; specifically, up to 19 particles.

Comparative Example 4

[0042] Cu having a purity of 6N or higher and 1 at % of Al having a purity of 5N or higher were prepared and placed in a water-cooled copper hearth, and the Cu and Al were simultaneously melted via electron beam melting in an atmosphere where hydrogen was introduced into a vacuum at a flow rate of 400 ml/min or more. Subsequently, the molten metal was poured into a water-cooled copper mold and melted via vacuum induction melting, and the solidified ingot was extracted from the bottom of the mold.

[0043] Subsequently, the obtained alloy ingot was processed into a sputtering target according to the same method and conditions as Example 1, and the target was bonded with a backing plate via diffusion bonding. As a result of examining the impurity concentration in a part cut out of the ingot, with regard to the gas components, the carbon content was 1 wtppm and the oxygen content was 3 wtppm. The values were higher in comparison to the case of adding a reducing gas. Furthermore, sputtering was performed using the obtained target in the same manner as Example 1, and the number of particles was measured. The result was sporadic generation of numerous particles; specifically, up to 23 particles.

Comparative Example 5

[0044] Cu having a purity of 6N or higher was prepared, and the Cu was placed into a water-cooled copper hearth and melted via electron beam melting in a vacuum. Note that a reducing gas was not introduced therein. Subsequently, the resulting molten metal was placed into a subsequent-stage water-cooled copper hearth, high-purity Al having a purity of 4N or higher was added to achieve an amount of 1 at %, and melted via electron beam melting. Subsequently, the molten metal was poured into a water-cooled copper mold and melted via vacuum induction melting, and the solidified ingot was extracted from the bottom of the mold.

[0045] Subsequently, the obtained alloy ingot was processed into a sputtering target according to the same method and conditions as Example 1, and the target was bonded with a backing plate via diffusion bonding. As a result of examining the impurity concentration in a part cut out of the ingot, with regard to the gas components, the carbon content was 0.2 wtppm and the oxygen content was 4 wtppm. The oxygen value was higher in comparison to the case of adding a reducing gas. Furthermore, sputtering was performed using the obtained target in the same manner as Example 1, and the number of particles was measured. The result was sporadic generation of numerous particles; specifically, up to 26 particles.

Comparative Examples 6-15

[0046] As shown in Table 1, the additive amount of Al was changed to 2 at % (Comparative Examples 6-10) or 4 at % (Comparative Examples 11-15), and alloy ingots and sputtering targets were prepared according to the same method as Comparative Example 1, respectively. Consequently, the oxygen content was 1 wtppm or more. The concentration of oxygen could not be reduced sufficiently. Furthermore, sputtering was performed using the obtained targets in the same manner as Example 1, and the number of particles was measured. The result was up to 18 particles or more, and the number of particles increased throughout the enter Life of the targets.

Comparative Examples 16-30

[0047] As shown in Table 1, Mn was used as the additive element, and the additive amount of Mn was changed to 1 at % (Comparative Examples 16-20), 2 at % (Comparative Examples 21-25, or 4 at % (Comparative Examples 26-30), and alloy ingots and sputtering targets were prepared according to the same method as Comparative Example 1, respectively. Consequently, the oxygen content was 3 wtppm or more. The concentration of oxygen could not be reduced sufficiently. Furthermore, sputtering was performed using the obtained targets in the same manner as Example 1, and the number of particles was measured. The result was up to 14 particles or more, and the number of particles increased throughout the enter Life of the targets.

INDUSTRIAL APPLICABILITY

[0048] The present invention can manufacture a copper alloy sputtering target containing extremely low amounts of oxygen and carbon, and, when this kind of sputtering target is subject to sputtering, it is possible to considerably suppress the generation of particles. The copper alloy sputtering target manufactured based on the present invention is particularly useful for forming a wiring film of semiconductor integrated circuits.