JP5787647B2 - Method for producing copper material for sputtering target - Google Patents

Description

The present invention relates to a manufacturing method of the copper alloy material used as a sputtering target.

  In recent years, flat panel displays have been used in various sizes from small electronic devices such as mobile PCs and mobile phone terminals to large televisions. In liquid crystal displays and organic EL displays, which are classified as flat panel displays, thin film transistor (hereinafter referred to as TFT) elements are incorporated in pixel dots in order to meet the demands for high-quality and high-speed drawing of moving images. Has been developed and is now mainstream.

  Conventionally, aluminum and its alloys have been used for TFT scanning lines, gate electrodes, and source-drain electrodes. However, as the liquid crystal display is enlarged and the number of pixels is increased, the wiring length is increased, and problems such as image display unevenness due to signal delay, power loss, etc. have become apparent. Therefore, attention has been focused on copper wiring with low electrical resistivity.

  The problem with using a copper wiring film for TFT element wiring is that when a copper film is formed directly on a glass substrate, the formed copper wiring film peels off from the glass due to poor adhesion at the Cu / glass interface. Problems can arise. In order to solve the problem of peeling, techniques described in the following Patent Documents 1 to 3 have been proposed.

  The invention of Patent Document 1 suppresses peeling by interposing a refractory metal such as molybdenum between a copper wiring and a glass substrate and forming a barrier layer having excellent adhesion to the glass substrate.

  The inventions of Patent Documents 2 and 3 use a target obtained by alloying copper to form an oxide at the interface between the copper wiring and the glass substrate, or concentrate an alloy element at the interface between the copper wiring and the glass substrate. , Peeling is suppressed.

  Techniques such as copper alloying have also been developed as in the inventions of Patent Documents 2 and 3, but industrially, as in the invention described in Patent Document 1, Mo, Ti, etc. having good adhesion to glass Is formed under the copper wiring as a barrier layer to improve peeling, and pure copper wiring is formed by sputtering.

  One of the important characteristics required in the process of forming the gate electrode of the TFT element is the uniformity of the wiring film within the substrate surface. Due to the uniformity of the film, that is, the difference in film thickness and the presence of irregularities, the electric capacity within the TFT becomes non-uniform, which adversely affects the display. In addition, in the TFT element manufacturing process, if there is a difference in film thickness or coarse clusters (particles, etc.), there is a concern that wiring defects such as disconnection and short circuit may be caused when wiring electrodes are created by etching. .

  In the case of forming a pure copper film to be a semiconductor wiring or the like in the sputtering process, the invention of a sputtering target capable of forming a uniform wiring film and suppressing coarse clusters and suppressing disconnection failure is described in Patent Documents 4 to 8, etc. Technology has been proposed.

  Patent Document 4 discloses that a defective disconnection is produced by using copper having a purity of 99.9999% or more excluding gas components of oxygen, nitrogen, carbon and hydrogen as a base and melting and solidifying at an oxygen concentration of 0.1 ppm or less. A sputtering target capable of obtaining wiring for VLSI with a low rate is described. This target material has an effect of reducing disconnection failure by reducing the amount of impurities in the copper material.

  Patent Document 5 uses a sputtering target material in which the average crystal grain size of the recrystallized structure is 80 μm or less and the Vickers hardness is 100 or less in copper having a purity of 99.995% or more. It is described that the expansion of protrusions and the generation of coarse clusters are suppressed.

Patent Document 6 discloses that in copper having a purity of 99.999% or more excluding gas components, the X-ray diffraction peak intensity I (111) of the (111) plane in the sputtering surface is increased, and the average particle size is 250 μm or less. In addition, it is described that the uniformity of the film thickness is improved by setting the variation of the particle diameter depending on the location within 20%.
In Patent Document 7, the volume of crystals facing the (110) plane on the surface is set to 80% or more, and the crystals are uniformly distributed from the surface to the center, so that the copper atoms jump out from the surface in the vertical direction. Further, it is described that a film can be formed up to a deep part of a groove having a large aspect ratio.
Patent Document 8 discloses that in copper having a purity of 99.999% or more, the average crystal grain size is controlled to 10 to 30 μm, and the particles having the orientations of (111), (200), (220), and (311) are used. It is described that uniformity and minimal particle generation can be achieved by reducing the amount to less than 50% and having a random orientation.

JP-A-7-66423 Japanese Patent No. 4065959 JP 2008-166742 A Japanese Patent No. 3727115 Japanese Patent No. 3975414 Japanese Patent No. 3403918 Japanese Patent No. 3997375 Japanese Patent No. 3971171

  According to the above-described conventional invention, it has become possible to control spattering of sputtered particles and control uniform film formation and coarse clusters by controlling the components, crystal grain size, strain and crystal orientation. However, in recent years, the size of a substrate such as a liquid crystal display for a large television has been increased, and the substrate size exceeding 2 m, such as 1870 mm × 2200 mm, has been achieved in the seventh generation. Accordingly, it has become necessary to form a film on a large substrate also in a sputtering process for creating wiring. As the power applied in film formation on a large substrate has increased, the problem of abnormal discharge has become apparent as a manufacturing problem. Abnormal discharge is a phenomenon in which electric power increases rapidly during sputtering, and is a phenomenon caused by local arc discharge. When an abnormal discharge occurs, the target material jumps out rapidly, which greatly affects the uniformity of the film and leads to a load on the apparatus.

In view of the above-mentioned demands, the present invention reduces the frequency of abnormal discharge during use even when high power is applied when creating wiring in a sputtering process on a large substrate used for a TFT liquid crystal panel or the like. It is another object of the present invention to provide a method for producing a copper material for a sputtering target that suppresses the occurrence of splash or the like.

The inventors of the present invention have made extensive studies to solve the above-described problems of the conventional techniques, and found that defects (microvoids, oxides) in the sputtering target material cause abnormal discharge. It was found that a copper material suitable for a sputtering target that reduces abnormal discharge can be provided by controlling the size and number of these defects in the sputtering plane.
The present invention has been made based on this finding.

That is, the product of the present invention is
(1) It is made of pure copper having a purity of 99.99% by mass , the average size of voids and inclusion defects inside the target is 30 μm or less, and the number of defects is 10 per unit area of the surface to be subjected to sputtering. / M ² or less, a method for producing a copper material for a sputtering target ,
It has a step of producing pure copper having a purity of 99.99% by mass or more by hot rolling, and after hot rolling with a processing rate of 20% or more in total at a temperature of 700 to 1000 ° C., as a final pass, A method for producing a copper material for a sputtering target, characterized by performing hot working at a processing rate of 10% or more at a temperature of 400 to 600 ° C. ,
(2) In the copper material for a sputtering target, the average crystal grain size on the sputtering surface is 50 to 200 μm, and the arithmetic average of hardness on the sputtering surface is 60 to 100 Hv. the process for producing a sputtering target for a copper material, and (3) after the step of performing water cooling at a cooling rate 50 ° C. / sec or more immediately after the hot rolling, characterized by performing the cold rolling, (1) or The manufacturing method of the copper material for sputtering targets as described in (2) is provided.

When a wiring film is formed in a sputtering process on a large substrate used for a TFT liquid crystal panel or the like by the method for producing a copper material for a sputtering target of the present invention, the frequency of occurrence of abnormal discharge is reduced. A copper material for a sputtering target capable of uniform film formation can be provided .

  The copper material for the sputtering target of the present invention is preferably copper having a purity of 99.99% by mass or more. Electrolytic copper, which is a raw material for producing a pure copper ingot, contains a certain amount of impurities, and they also appear as inevitable impurities in the pure copper ingot. In particular, it is desirable that the impurities contain B, Al, Si, P, As, Sb, and Bi in an amount of 5 ppm or less. Since these elements are elements used as dopants for Si semiconductors and may adversely affect semiconductor characteristics, the more preferable purity is 99.995% by mass or more of copper.

Defects in the copper material copper material for the sputtering target cause abnormal discharge and must be managed. The defect here refers to inclusions such as voids and oxides. Here, the void means a void in the copper material, which is considered to be caused by a gas defect, crack or the like. The oxide is an oxide such as copper oxide or cuprous oxide. Since the contribution to abnormal discharge is small if the size of the defect is 30 μm or less, it is necessary to manage the defect size. The defect size is preferably smaller, more preferably 20 μm or less. Furthermore, defects of 10 μm or less do not substantially contribute to abnormal discharge. The number of defects is preferably 10 or less per unit area of 1 m ^{2 on} the sputtering surface. When the number of defects is larger than this, the frequency of occurrence of abnormal discharge increases.
In the present invention, the average defect size means an average of the number of each defect size per unit area 1 m ² . In the present invention, “defect” refers to an internal defect (a defect existing inside, not on the surface).

  Specifically, the defect in the sputtering target can be detected using an ultrasonic flaw detector or the like.

  Since the copper material for the sputtering target of the present invention is required to have a uniform structure, it is desirable that the copper material has a substantially recrystallized structure. When the crystal grain size is large, high energy is required to make the target material fly off, and a large number of target atoms solidify and fly out, so that the formation of coarse clusters tends to be uneven and the formed film tends to be non-uniform. A preferable crystal grain size is 50 to 200 μm. If the crystal grain size is too small, a large amount of strain remains in the crystal grains and the target material jumps out unevenly. On the other hand, if it is too large, high energy is required to make the target atoms jump out, so that abnormal discharge is likely to occur, and the generated film becomes non-uniform. The control of the crystal grain size can be carried out in the following hot working process.

  In addition, when strain is inherent in the copper material of the present invention, it affects the pop-out of the target material, so it is preferable to control this. If the strain inherent in the material varies from site to site, the energy differs from the surroundings, and the target material jumps out from site to site, making uniform film formation impossible. The strain inside the copper material can be evaluated by measuring the hardness. The hardness is desirably in the range of 60 to 100 Hv. If the strain is too large, a large number of target atoms will harden and fly out, and the formation of coarse clusters will increase, resulting in non-uniform film formation, and it is desirable that the hardness be 100 HV or less. In the step of attaching to the backing plate of the sputtering apparatus, it is desirable that the sputtering target is hard in terms of preventing deformation and the like during attachment. If the hardness is less than 60 Hv, defects are likely to occur in the attachment process.

  In order to control the size and number of defects in the sputtering target, the following points should be noted in the manufacturing process. The production of the copper material in the present invention takes the steps of melt casting, hot working, cold rolling, and heat treatment. If necessary, a chamfering step may be included between hot working and cold working. Further, cold rolling and heat treatment may be repeated. Here, hot working is hot rolling, hot extrusion, or the like, and refers to a process of working an ingot obtained by a melt casting process at a high temperature. By manufacturing in consideration of the following, it becomes possible to produce a copper material that satisfies the above-mentioned metal structure specifications, and as a target material for a large display that performs target production by combining strip-shaped plates. When used, the effect of facilitating uniform formation of a sputtering film with little abnormal discharge is obtained.

  In melt casting, it is desirable to minimize defects as much as possible. Pure copper having a purity of 99.99% or more is dissolved in an inert gas atmosphere or vacuum casting, and cast into a mold.

  The hot working process can be performed by hot rolling, hot extrusion, hot forging, or the like. In a copper material used as a sputtering target, the crystal grain size is almost determined by this hot working. Further, it is possible to press-bond solidification defects caused by casting by hot working.

  In the hot working process, in order to press the solidification defects caused by casting at a high temperature, it is desirable that the heating temperature of the material before hot rolling is in the range of 700 to 1000 ° C. When the heating temperature of the material is lower than 700 ° C., defects are not pressure-bonded by hot working, and dynamic recrystallization does not occur sufficiently and a uniform metal structure cannot be obtained. When the temperature is higher than 1000 ° C., it is difficult to control the crystal grain size. For pressure bonding of rolling, it is desirable to perform hot working between 700 ° C. and 1000 ° C. at a working rate of 20% or more. From the viewpoint of controlling the crystal grain size, it is preferable to heat the material before hot rolling at the above temperature for 30 to 300 minutes.

  When hot working is performed by hot rolling, it is necessary not to stagnate the material in order to avoid cooling from the end. In order to control the crystal grain size, it is desirable to perform processing at a processing rate of 10% or more at a temperature of 400 to 600 ° C. in the final pass of hot rolling. It is desirable to cool with water cooling after the final pass. In order to set the crystal grain size to the above-mentioned 50 to 200 μm, it is desirable that the time from the last pass to the water cooling is within 60 seconds and the water cooling rate is 50 ° C./second or more.

In the hot extrusion process of the present invention, the extruded material can be immediately water-cooled without being exposed to the atmosphere, so that it is possible to cool at a high rate immediately after dynamic recrystallization. Therefore, a metal structure with little variation in temperature inside the material and a very small variation in crystal grain size and hardness in the longitudinal direction and the width direction can be obtained. When performing by a hot extrusion process, it is preferable to carry out by one pass in the processing temperature of the material before a hot extrusion in the range of 700-1000 degreeC.
When the heating temperature of the material is lower than 700 ° C., defects are not pressed and dynamic recrystallization does not occur sufficiently during extrusion, and a uniform metal structure cannot be obtained. When the temperature is higher than 1000 ° C., it is difficult to control the crystal grain size. From the viewpoint of controlling the crystal grain size, it is desirable to set the cooling rate immediately after hot extrusion to 50 ° C./second or more.

  The material after hot working may be tempered by cold rolling and annealing. The total cold working rate is desirably 30% or less (including 0%, which means that rolling is not performed). If the sum of the cold working rates exceeds 30%, the amount of strain inside the material increases, which may exceed the specified hardness value.

  Hereinafter, the present invention will be described in more detail based on examples, but the present invention is not limited thereto.

(Example)
Invention Example No. using the purity copper shown in Table 1. 1-8 and Comparative Example No. Ingots having a thickness of 9 to 18 with a plate thickness of 180 mm, a width of 720 mm, and a length of 3000 mm were produced. After heating them at the temperature shown in Table 1, hot rolling was performed to produce a plate having a thickness of 23 mm, a width of 720 mm, and a length of about 23 m. The temperature of the material during hot rolling was measured by a radiation thermometer. The temperature was adjusted by controlling the time between each pass. Next, detailed manufacturing conditions of each invention example and comparative example will be described in detail.

  Invention Example No. 1, heating is performed at 900 ° C. before hot rolling, and then a rolling rate of 5.6% → 5.9% → 7.5% → 5.4% is passed in a temperature range of 850 to 750 ° C. Carried out. Moreover, after that, the pass was repeated at 750 to 550 ° C., and the final pass was applied at 550 ° C. to a rolling rate of 14.8%, so that the thickness was 23 mm. Immediately after hot rolling, water cooling was performed at a cooling rate of about 50 ° C./second through a water cooling zone equipped with a shower. From the obtained base plate, a length of 3 m was cut and sampled, and the oxide film on the surface of the obtained base plate was chamfered to a plate thickness of 20 mm. Then, the flat plate of thickness 18mm * width 720mm was created by cold rolling.

  Invention Example No. In No. 2, no. A length of 3 m was cut from 1 base plate and sampled, and the oxide film on the surface of the obtained base plate was chamfered to a plate thickness of 18 mm, and cold rolling was not performed.

  Invention Example No. 3, heating is performed at 980 ° C. before hot rolling, and then a pass of a rolling rate of 5.6% → 5.9% → 7.5% → 5.4% is performed in a temperature range of 950 to 850 ° C. Carried out. Moreover, after that, the pass was repeated at 850 to 600 ° C., and the final pass was applied at 580 ° C. with a rolling rate of 11.5%, so that the thickness was 23 mm. After hot rolling, it was passed as soon as possible through a water-cooling zone equipped with a water-cooled shower, and the cooling rate was approximately 50 ° C./second. From the obtained base plate, a length of 3 m was cut and sampled, and the oxide film on the surface of the obtained base plate was chamfered to a plate thickness of 20 mm. Then, the flat plate of thickness 18mm * width 720mm was created by cold rolling.

  Invention Example No. In No. 4, heating is performed at 780 ° C. before hot rolling, and then a rolling rate of 5.6% → 5.9% → 7.5% → 5.4% is passed in a temperature range of 750 to 700 ° C. Carried out. Further, the pass was repeated thereafter at 700 to 500 ° C., and the final pass was applied at 500 ° C. with a rolling rate of 14.8%, so that the above-mentioned thickness was 23 mm. Immediately after hot rolling, water cooling was performed at a cooling rate of about 50 ° C./second through a water cooling zone equipped with a shower. From the obtained base plate, a length of 3 m was cut and sampled, and the oxide film on the surface of the obtained base plate was chamfered to a plate thickness of 20 mm. Then, the flat plate of thickness 18mm * width 720mm was created by cold rolling.

  Invention Example No. In No. 5, heating was performed at 890 ° C. before hot rolling, and then a rolling rate of 11.1% → 12.5% → 7.1% was performed in a temperature range of 840 to 720 ° C. Further, the pass was repeated thereafter at 720 to 600 ° C., and the final pass was applied at a rolling rate of 14.8% at 550 ° C. to obtain the above-mentioned thickness of 23 mm. Immediately after hot rolling, water cooling was performed at a cooling rate of about 50 ° C./second through a water cooling zone equipped with a shower. From the obtained base plate, a length of 3 m was cut and sampled, and the oxide film on the surface of the obtained base plate was chamfered to a plate thickness of 20 mm. Then, the flat plate of thickness 18mm * width 720mm was created by cold rolling.

  Invention Example No. 6, heating is performed at 900 ° C. before hot rolling, and then a rolling rate of 5.6% → 5.9% → 4.7% → 4.3% is performed in a temperature range of 850 to 700 ° C. Carried out. Moreover, after that, the pass was repeated at 700 to 600 ° C., and the final pass was applied at 550 ° C. to a rolling rate of 14.8%, so that the thickness was 23 mm. Immediately after hot rolling, water cooling was performed at a cooling rate of about 50 ° C./second through a water cooling zone equipped with a shower. From the obtained base plate, a length of 3 m was cut and sampled, and the oxide film on the surface of the obtained base plate was chamfered to a plate thickness of 20 mm. Then, the flat plate of thickness 18mm * width 720mm was created by cold rolling.

  Invention Example No. 7, heating is performed at 900 ° C. before hot rolling, and then a rolling rate of 5.6% → 5.9% → 7.5% → 5.4% is passed in the temperature range of 850 to 750 ° C. Carried out. Moreover, after that, the pass was repeated at 750 to 430 ° C., and the final pass was applied at 430 ° C. to a rolling rate of 14.8%, so that the thickness was 23 mm. Immediately after hot rolling, water cooling was performed at a cooling rate of about 50 ° C./second through a water cooling zone equipped with a shower. From the obtained base plate, a length of 3 m was cut and sampled, and the oxide film on the surface of the obtained base plate was chamfered to a plate thickness of 20 mm. Then, the flat plate of thickness 18mm * width 720mm was created by cold rolling.

  Invention Example No. 8, heating is performed at 850 ° C. before hot rolling, and then a pass of a rolling rate of 5.6% → 5.9% → 7.5% → 5.4% is performed in a temperature range of 800 to 720 ° C. Carried out. Further, the pass was repeated thereafter at 720 to 550 ° C., and the final pass was applied at 550 ° C. to a rolling rate of 10.2%, so that the above-mentioned thickness was 23 mm. Immediately after hot rolling, water cooling was performed at a cooling rate of about 50 ° C./second through a water cooling zone equipped with a shower. From the obtained base plate, a length of 3 m was cut and sampled, and the oxide film on the surface of the obtained base plate was chamfered to a plate thickness of 20 mm. Then, the flat plate of thickness 18mm * width 720mm was created by cold rolling.

  Comparative Example No. 9, heating is performed at 900 ° C. before hot rolling, and then a pass of a rolling rate of 5.6% → 5.9% → 7.5% → 5.4% is performed in a temperature range of 850 to 750 ° C. Carried out. Moreover, after that, the pass was repeated at 750 to 550 ° C., and the final pass was applied at 550 ° C. to a rolling rate of 14.8%, so that the thickness was 23 mm. Immediately after hot rolling, water cooling was performed at a cooling rate of about 50 ° C./second through a water cooling zone equipped with a shower. From the obtained base plate, a length of 3 m was cut and sampled, and the oxide film on the surface of the obtained base plate was chamfered to a plate thickness of 20 mm. Then, the flat plate of thickness 18mm * width 720mm was created by cold rolling.

  Comparative Example No. 10, heating is performed at 900 ° C. before hot rolling, and then a rolling rate of 5.6% → 5.9% → 7.5% → 5.4% is passed in a temperature range of 850 to 750 ° C. Carried out. Moreover, after that, the pass was repeated at 750 to 550 ° C., and the final pass was applied at 550 ° C. to a rolling rate of 14.8%, so that the thickness was 23 mm. Cooling after hot rolling was performed at a cooling rate of approximately 10 ° C./second through a water cooling zone equipped with a shower. From the obtained base plate, a length of 3 m was cut and sampled, and the oxide film on the surface of the obtained base plate was chamfered to a plate thickness of 20 mm. Then, the flat plate of thickness 18mm * width 720mm was created by cold rolling.

  Comparative Example No. 11, heating is performed at 1020 ° C. before hot rolling, and then a rolling rate of 5.6% → 5.9% → 7.5% → 5.4% is passed in a temperature range of 1000 to 950 ° C. Carried out. Further, after that, the pass was repeated at 950 to 700 ° C., and the final pass was applied to the rolling rate of 14.8% at 700 ° C. to the above-mentioned thickness of 23 mm. Immediately after hot rolling, water cooling was performed at a cooling rate of about 50 ° C./second through a water cooling zone equipped with a shower. From the obtained base plate, a length of 3 m was cut and sampled, and the oxide film on the surface of the obtained base plate was chamfered to a plate thickness of 20 mm. Then, the flat plate of thickness 18mm * width 720mm was created by cold rolling.

  Comparative Example No. 12, heating is performed at 780 ° C. before hot rolling, and then a rolling rate of 5.6% → 5.9% → 7.5% → 5.4% is passed in the temperature range of 690 to 620 ° C. Carried out. Further, the pass was repeated thereafter at 620 to 500 ° C., and the final pass was applied at 450 ° C. to a rolling rate of 14.8%, so that the above-mentioned thickness was 23 mm. Immediately after hot rolling, water cooling was performed at a cooling rate of about 50 ° C./second through a water cooling zone equipped with a shower. From the obtained base plate, a length of 3 m was cut and sampled, and the oxide film on the surface of the obtained base plate was chamfered to a plate thickness of 20 mm. Then, the flat plate of thickness 18mm * width 720mm was created by cold rolling.

  Comparative Example No. 13, heating is performed at 850 ° C. before hot rolling, and then a pass of a rolling rate of 2.8% → 2.9% → 2.9% → 3.0% is performed in a temperature range of 800 to 700 ° C. Carried out. Moreover, after that, the pass was repeated at 700 to 550 ° C., and the final pass was applied at a rolling rate of 14.8% at 550 ° C. to the above-mentioned thickness of 23 mm. Immediately after hot rolling, water cooling was performed at a cooling rate of about 50 ° C./second through a water cooling zone equipped with a shower. From the obtained base plate, a length of 3 m was cut and sampled, and the oxide film on the surface of the obtained base plate was chamfered to a plate thickness of 20 mm. Then, the flat plate of thickness 18mm * width 720mm was created by cold rolling.

  Comparative Example No. 14, heating is performed at 900 ° C. before hot rolling, and then a rolling rate of 5.6% → 5.9% → 7.5% → 5.4% is passed in the temperature range of 850 to 750 ° C. Carried out. Moreover, after that, the pass was repeated at 750 to 650 ° C., and the final pass was applied at 620 ° C. to a rolling rate of 14.8%, so that the thickness was 23 mm. Immediately after hot rolling, water cooling was performed at a cooling rate of about 50 ° C./second through a water cooling zone equipped with a shower. From the obtained base plate, a length of 3 m was cut and sampled, and the oxide film on the surface of the obtained base plate was chamfered to a plate thickness of 20 mm. Then, the flat plate of thickness 18mm * width 720mm was created by cold rolling.

  Comparative Example No. 15, heating is performed at 900 ° C. before hot rolling, and then a rolling rate of 5.6% → 5.9% → 7.5% → 5.4% is passed in a temperature range of 850 to 750 ° C. Carried out. Further, the pass was repeated thereafter at 750 to 400 ° C., and the final pass was applied at 385 ° C. to a rolling rate of 14.8%, so that the thickness was 23 mm. Immediately after hot rolling, water cooling was performed at a cooling rate of about 50 ° C./second through a water cooling zone equipped with a shower. From the obtained base plate, a length of 3 m was cut and sampled, and the oxide film on the surface of the obtained base plate was chamfered to a plate thickness of 20 mm. Then, the flat plate of thickness 18mm * width 720mm was created by cold rolling.

  Comparative Example No. 16, heating is performed at 900 ° C. before hot rolling, and then a rolling rate of 5.6% → 5.9% → 7.5% → 5.4% is passed in the temperature range of 850 to 750 ° C. Carried out. Further, the pass was repeated thereafter at 750 to 550 ° C., and the final pass was applied at 550 ° C. to a rolling rate of 6.1%, so that the thickness was 23 mm. Immediately after hot rolling, water cooling was performed at a cooling rate of about 50 ° C./second through a water cooling zone equipped with a shower. From the obtained base plate, a length of 3 m was cut and sampled, and the oxide film on the surface of the obtained base plate was chamfered to a plate thickness of 20 mm. Then, the flat plate of thickness 18mm * width 720mm was created by cold rolling.

  Comparative Example No. In No. 17, no. Cut and sample 3 mm length from the base plate of 1 and chamfer the oxide film on the surface of the obtained base plate to a plate thickness of 20 mm, then cold-roll a plate 15 mm thick x 720 mm wide It was created.

Comparative Example No. 18, no. A length of 3 m was cut from the base plate of 3 and sampled. The oxide film on the surface of the base plate was chamfered to a plate thickness of 18 mm, and cold rolling was not performed.
Comparative Example No. Nos. 9, 12, and 13 are comparative examples for the invention of the above (1). Reference numerals 10, 11, and 14 to 18 are comparative examples for the invention of (2).

  With respect to the flat plate thus obtained, the diameter and number of internal defects, the crystal grain size on the plate surface, and the hardness were measured by the following methods. In addition, sputtering characteristics were investigated.

[1] Evaluation of internal defects 1 m of each of the obtained flat plate of about 3 m was sampled, and at the target surface, an ultrasonic flaw detection imaging apparatus manufactured by Nippon Kraut Kramer Co., Ltd. was used. Size and number were measured. The defect diameter was regarded as equivalent to a circle, and the average value was obtained. The number of defects was converted to the number of defects of 10 μm or more as the number per 1 m ² of unit area.

[2] Crystal grain size Using samples subjected to internal defect evaluation, the microstructure was observed on the target surface at each of the rolling front end and the rear end at 6 locations, and measured based on JIS H 0501 (cutting method). . The obtained six values were averaged to obtain the average crystal grain size of the target.

[3] Hardness measurement Using samples subjected to internal defect evaluation, measurement was performed with a micro Vickers hardness tester in accordance with JIS Z 2244 at the target surface at each of the rolling front end portion and the rear end portion. went. The obtained six values were averaged to obtain the average hardness of the target.

[4] Sputtering characteristics From the obtained flat plate, a width of 630 × length 710 was sampled, and the upper and lower surfaces were chamfered and polished to prepare a sputtering target having a thickness of 10 mm. In order to exclude the influence of the roughness of the target surface, the roughness was all adjusted by polishing the maximum roughness Ra to 0.5 to 0.8 μm. Using a DC magnetron sputtering apparatus, sputtering was performed on an OA-10 glass substrate manufactured by Nippon Electric Glass Co., Ltd. having a film thickness of 0.7 mm, thereby forming a copper wiring having a thickness of 0.3 μm. The sputtering conditions were an Ar gas pressure of 0.4 Pa and a discharge power of 12 W / cm ² . Thereafter, heat treatment was performed in a vacuum at 300 ° C. for 30 minutes. Ten film thicknesses of the copper wiring after the heat treatment were measured. The measurement position was measured at 9 points every 300 mm square and 2 points at the center of the substrate with the center of the base as a reference so as to cover the entire surface of the obtained target material. In the total data of 90 target materials cut out from the same plate, the plate with the maximum film thickness and the minimum film thickness range of ± 7% is “good” and the one with more variation is “bad” "

[5] Frequency of abnormal discharge The frequency of abnormal discharge was determined to be good when the sputtering was generated 15 times or less per 10 batches, but not when it was generated more than 16 times. Abnormal discharge was observed with an arc counter (the number of times arcing occurred was counted).

  The results are also shown in Table 1. In all of the examples of the present invention, the abnormal discharge is small and excellent sputtering characteristics are exhibited. Comparative Example No. 9 had a large amount of impurities, resulting in poor sputtering characteristics. Comparative Example No. Nos. 10, 11, 13, and 16 have a crystal grain size defined by Comparative Example No. Nos. 12 and 13 indicate that the defect is defined as Comparative Example No. No. 15 is a comparative example No. 15 in terms of crystal grain size and hardness. In No. 17, the hardness was not specified, so there were many abnormal discharges or the sputtering characteristics deteriorated. Comparative Example No. 18 was too hard to be evaluated because it was distorted when joined to the backing plate.

Claims (3)

It is made of pure copper having a purity of 99.99% by mass or more, the average size of voids and inclusion defects inside the target is 30 μm or less, and the number of defects is 10 / m ² per unit area of the surface used for sputtering. A method for producing a copper material for a sputtering target , which is as follows:
It has a step of producing pure copper having a purity of 99.99% by mass or more by hot rolling, and after hot rolling with a processing rate of 20% or more in total at a temperature of 700 to 1000 ° C., as a final pass, A method for producing a copper material for a sputtering target, characterized by performing hot working at a processing rate of 10% or more at a temperature of 400 to 600 ° C. 2. The sputtering target according to claim 1, wherein the copper material for a sputtering target has an average crystal grain size of 50 to 200 μm on a sputtering surface and an arithmetic average of hardness on the sputtering surface of 60 to 100 Hv. Method for manufacturing copper material. The method for producing a copper material for a sputtering target according to claim 1 or 2 , wherein cold rolling is performed immediately after the hot rolling after the step of water cooling at a cooling rate of 50 ° C / second or more.