JP6661951B2 - High purity copper sputtering target material - Google Patents

Description

  The present invention relates to a high-purity copper sputtering target material used for forming a wiring film (high-purity copper film) in a semiconductor device, a flat panel display such as a liquid crystal or an organic EL panel, a touch panel, and the like.

Conventionally, Al has been widely used as a wiring film for semiconductor devices, flat panel displays such as liquid crystal and organic EL panels, and touch panels. Recently, wiring films have been miniaturized (narrowed) and thinned, and a wiring film having a lower specific resistance than before has been demanded.
Therefore, with the miniaturization and thinning of the wiring film described above, a wiring film made of copper (Cu), which is a material having a lower specific resistance than Al, has been provided.

Incidentally, the above-mentioned wiring film is usually formed in a vacuum atmosphere using a sputtering target. Here, when film formation is performed using a sputtering target, abnormal discharge (arcing) may occur due to foreign matter in the sputtering target, and thus a uniform wiring film may not be formed. Here, the abnormal discharge is a phenomenon in which an extremely high current suddenly flows suddenly compared to the time of normal sputtering, and an abnormally large discharge suddenly occurs. This may cause particles to be generated or the thickness of the wiring film may be non-uniform. Therefore, it is desired that abnormal discharge during film formation be avoided as much as possible.
Therefore, Patent Documents 1 to 5 below propose a technique for suppressing the occurrence of abnormal discharge during film formation in a pure copper sputtering target.

  Patent Literature 1 proposes a sputtering target made of high-purity copper having a purity of 6N or more. In the high-purity copper sputtering target described in Patent Document 1, the content of P, S, O, and C is set to 1 ppm or less, respectively, and nonmetallic inclusions having a particle size of 0.5 μm or more and 20 μm or less are used. By controlling the number to 000 particles / g or less, foreign substances in the sputtering target are reduced, and abnormal discharge (arcing) and particles are suppressed.

  Patent Document 2 discloses that the purity of Cu excluding O, H, N, and C is in the range of 99.999980 mass% or more and 99.999998 mass% or less, the content of Al is 0.005 massppm or less, and the content of Si is A high-purity copper sputtering target having a content of 0.05 mass ppm or less has been proposed.

  Patent Document 3 discloses that pure copper ingot having a ratio of total special grain boundary length Lσ to total grain boundary length L of 25% or more is obtained by processing a pure copper ingot having a purity of 99.96 mass% or more under predetermined conditions. Plates (sputtering targets) have been proposed. The Vickers hardness is 40 to 90 and the average crystal grain size is 10 to 120 μm.

  Patent Document 4 discloses that pure copper having a purity of 99.99 mass% or more has an average crystal grain size of 40 μm or less, a total grain boundary length L measured by an EBSD method, a Σ3 grain boundary length Lσ3, A sputtering target has been proposed in which the ratio of (Σ3 + Σ9) grain boundary length (L (σ3 + σ9) / L), which is the ratio to the sum L (σ3 + σ9) of Σ9 grain boundary length Lσ9, is 28% or more.

  Patent Document 5 proposes a sputtering target in which pure copper having a purity of 99.995 mass% or more has a substantially recrystallized structure, an average crystal grain size of 80 μm or less, and a Vickers hardness of 100 or less. ing.

Japanese Patent No. 4680325 JP-A-2005-034337 JP 2011-162835 A JP 2014-201814 A JP-A-11-158614

By the way, recently, in semiconductor devices, flat panel displays such as liquid crystal and organic EL panels, touch panels, and the like, further densification of wiring films has been required, and miniaturization and thinning have been performed more than before. It is necessary to form a wiring film stably. Further, it is necessary to apply a high voltage for further high-speed film formation, and in this case, it is required to suppress occurrence of abnormal discharge.
Here, in the inventions described in Patent Literatures 1 to 5 described above, abnormal discharge (arcing) cannot be sufficiently suppressed during film formation, and a fine and thinned wiring film can be efficiently and stably formed. And could not be formed.

  The present invention has been made in view of the above-described circumstances, and provides a high-purity copper sputtering target material capable of suppressing occurrence of abnormal discharge even when a high voltage is applied and capable of performing stable film formation. The purpose is to do.

In order to solve the above-mentioned problem, the high-purity copper sputtering target material of the present invention has a purity of Cu of 99.9999 mass% or more excluding O, H, N, and C, and an Al content of 0.005 massppm. Hereinafter, the content of Si is 0.05 mass ppm or less, the content of Fe is 0.02 mass ppm or less, the content of S is 0.03 mass ppm or less, the content of Cl is 0.1 mass ppm or less, and the content of O is 1 mass ppm or less. The content of H is 1 mass ppm or less, the content of N is 1 mass ppm or less, and the content of C is 1 mass ppm or less. Measurement) Local orientation difference in the crystal orientation (Kernel Average Misorientation: KAM) is Ri der 1.5 ° or less, is the average crystal grain size and 70μm or less, that the Vickers hardness is in a range of less 50Hv than 35Hv Features.

  In the high-purity copper sputtering target material having this configuration, the purity of Cu excluding O, H, N, and C is set to 99.9999 mass% or more, the content of Al is 0.005 massppm or less, and the content of Si is 0. 0.05 mass ppm or less, Fe content of 0.02 mass ppm or less, S content of 0.03 mass ppm or less, Cl content of 0.1 mass ppm or less, O content of 1 mass ppm or less, H content of 1 mass ppm or less, Since the content of N is 1 mass ppm or less, and the content of C is 1 mass ppm or less, it is possible to suppress the generation of foreign substances such as oxides, carbides, nitrides, sulfides, and chlorides in the sputtering target. It is possible to suppress the occurrence of abnormal discharge caused by the discharge. Further, generation of gas during film formation can be suppressed to maintain a degree of vacuum, and film formation can be performed stably.

  Further, since the local orientation difference (KAM) of the crystal orientation obtained by the EBSD measurement is set to 1.5 ° or less, the local orientation difference in the crystal grains is small, and the generation state of secondary electrons during sputtering is stable. Therefore, occurrence of abnormal discharge can be suppressed.

Scan Pattareto, since different depending on the crystal orientation, the sputtering surface when the sputtering progresses, irregularities caused by the difference in sputtering rate described above. If the grain size of the crystal grains on the sputter surface is large, the irregularities become large, and the electric charges are concentrated on the convex portions, so that abnormal discharge is likely to occur. Therefore, by limiting the average crystal grain size on the sputtered surface to 70 μm or less, it is possible to further suppress the occurrence of abnormal discharge.

In addition , since the Vickers hardness of the sputtered surface is limited to 50 Hv or less, the internal strain in the crystal grains is small, the secondary electron emission during sputtering is uniform, and the film can be stably formed. it can. In addition, by reducing the internal strain, the sputter rate becomes uniform, and it is possible to suppress the formation of irregularities on the sputter surface when the sputtering proceeds, thereby suppressing the occurrence of abnormal discharge.
On the other hand, since the Vickers hardness of the sputtered surface is 35 Hv or more, the crystal grain size can be made relatively small, and the formation of irregularities on the sputtered surface when sputtering proceeds can be suppressed, and abnormal discharge can occur. Can be suppressed.

  According to the present invention, it is possible to provide a high-purity copper sputtering target material capable of suppressing occurrence of abnormal discharge even when a high voltage is applied and capable of performing stable film formation.

Hereinafter, a high-purity copper sputtering target material according to an embodiment of the present invention will be described.
The high-purity copper sputtering target material of the present embodiment is used when a high-purity copper film used as a wiring film in a semiconductor device, a flat panel display such as a liquid crystal or organic EL panel, a touch panel, etc. is formed on a substrate. It is something that can be done.

  The composition of the high-purity copper sputtering target material according to the present embodiment is such that the purity of Cu excluding O, H, N, and C is 99.99998 mass% or more, the content of Al is 0.005 massppm or less, Content of 0.05 mass ppm or less, Fe content of 0.02 mass ppm or less, S content of 0.03 mass ppm or less, Cl content of 0.1 mass ppm or less, O content of 1 mass ppm or less, H content The amount is 1 mass ppm or less, the N content is 1 mass ppm or less, and the C content is 1 mass ppm or less.

  In the high-purity copper sputtering target material of the present embodiment, the local azimuth difference (KAM) of the crystal orientation obtained by EBSD measurement is set to 1.5 ° or less.

Furthermore, in the high-purity copper sputtering target material according to the present embodiment, the average crystal grain size is set to 70 μm or less, and the Vickers hardness is set to a range of 35 to 55 Hv.
Hereinafter, the reason why the composition, the local orientation difference (KAM), the average crystal grain size, and the Vickers hardness of the high-purity copper sputtering target material according to the present embodiment are specified as described above will be described.

(Cu: 99.99998 mass% or more)
When a wiring film (high-purity copper film) is formed by sputtering, it is preferable to reduce impurities as much as possible in order to suppress abnormal discharge (arcing). Here, if the purity of Cu is 99.9999 mass% or more, it is not necessary to perform the purification treatment more than necessary, and it is possible to suppress a significant increase in manufacturing cost.

(Al: 0.005 mass ppm or less)
Al is an element that easily forms oxides, carbides, nitrides, and the like, and therefore tends to remain as foreign matter in the sputtering target. Therefore, by limiting the content of Al to 0.005 mass ppm or less, it is possible to suppress the occurrence of abnormal discharge (arcing) during film formation even when the purity of Cu is 99.9998 mass% or more. .

(Si: 0.05 mass ppm or less)
Since Si is an element that easily forms oxides, carbides, nitrides, and the like, it tends to easily remain as foreign matter in the sputtering target. Therefore, by limiting the content of Si to 0.05 mass ppm or less, it is possible to suppress the occurrence of abnormal discharge (arcing) during film formation even when the purity of Cu is 99.9999 mass% or more. .

(Fe: 0.02 mass ppm or less)
Fe is an element that easily forms oxides, carbides, nitrides, and the like as compared with copper, and thus tends to easily remain as foreign matter in a high-purity copper sputtering target. Therefore, by limiting the Fe content to 0.02 mass ppm or less, it becomes possible to suppress the occurrence of abnormal discharge (arcing) during film formation even when the purity of Cu is 99.9998 mass% or more. .

(S: 0.03 mass ppm or less)
S is an element that reacts with another impurity element to form a sulfide and easily remains as a foreign substance in the sputtering target. Further, when it exists alone, there is a possibility that gasification and ionization occur during film formation, the degree of vacuum is reduced, and abnormal discharge (arcing) is induced. From the above, in the present embodiment, the content of S is limited to 0.03 mass ppm or less.

(Cl: 0.1 mass ppm or less)
Cl is an element that reacts with another impurity element to form a chloride and easily remains as a foreign substance in a sputtering target. Further, when it exists alone, there is a possibility that gasification and ionization occur during film formation, the degree of vacuum is reduced, and abnormal discharge (arcing) is induced. From the above, in the present embodiment, the Cl content is limited to 0.1 mass ppm or less.

(O, H, N: 1 mass ppm or less each)
When a film is formed using a sputtering target, the film is formed in a vacuum atmosphere. Therefore, if a large amount of these gas components are present, the degree of vacuum may be reduced during film formation and abnormal discharge (arcing) may be induced. In addition, particles may be generated due to abnormal discharge, and the quality of the high-purity copper film may be degraded. From the above, in the present embodiment, the contents of O, H, and N are each limited to 1 mass ppm or less.

(C: 1 mass ppm or less)
C reacts with other impurity elements to form carbides and is likely to remain as foreign matter in the sputtering target. In addition, since C easily remains in the sputtering target as a simple substance, there is a possibility that abnormal discharge (arcing) may be induced. From the above, in the present embodiment, the content of C is limited to 1 mass ppm or less.

In this embodiment, as described above, the upper limits of the contents of the various impurity elements are set, but the purity of Cu excluding O, H, N, and C is 99.9999 mass% or more. Thus, it is necessary to regulate the total amount of impurity elements.
Here, analysis of impurity elements except O, H, N, and C can be performed using a glow discharge mass spectrometer (GD-MS).
The analysis of O can be performed by an inert gas fusion-infrared absorption method, the analysis of H and N can be performed by an inert gas fusion-heat conduction method, and the analysis of C can be performed by a combustion-infrared absorption method.

(KAM value is 1.5 ° or less)
When the local average misorientation (KAM) of crystal orientation exceeds 1.5 °, the strain in the crystal grains is relatively large, and the generation of secondary electrons during sputtering in a region where this strain exists is generated. The situation may become unstable.
Therefore, in the present embodiment, by setting KAM to 1.5 ° or less, it is possible to reduce the strain in the crystal grains and to stabilize the generation of secondary electrons during sputtering.
In order to reliably stabilize the generation of secondary electrons during sputtering, the above KAM is preferably set to 1.0 ° or less, more preferably 0.7 ° or less.

(Average crystal grain size: 70 μm or less)
Since the sputter rate differs depending on the crystal orientation, as the sputtering proceeds, irregularities corresponding to the crystal grains are generated on the sputter surface due to the difference in the sputter rate.
Here, when the average crystal grain size exceeds 70 μm, irregularities generated on the sputtered surface become large, and charges are concentrated on the protruding portions, so that abnormal discharge is likely to occur.
For these reasons, in the high-purity copper sputtering target of the present embodiment, the average crystal grain size is specified to be 70 μm or less.
In order to suppress abnormal discharge by suppressing irregularities on the sputter surface when sputtering proceeds, the average crystal grain size is preferably 60 μm or less, more preferably 50 μm or less.

(Vickers hardness: 35Hv or more and 55Hv or less)
In the high-purity copper sputtering target according to the present embodiment, when the Vickers hardness exceeds 55 Hv, the internal strain in the crystal grain becomes large, the generation state of secondary electrons during sputtering becomes unstable, and the film is formed. May not be performed stably. In addition, the sputter rate becomes non-uniform due to internal strain, and irregularities are generated on the sputtered surface, which may increase the number of micro-arc discharges. On the other hand, when the Vickers hardness is less than 35 Hv, the crystal grain size becomes coarse, so that as the sputtering proceeds, irregularities are generated on the sputtered surface, and abnormal discharge easily occurs.
For this reason, in the present embodiment, the Vickers hardness is defined in the range from 35 Hv to 55 Hv.
Note that, in order to suppress the crystal grain size from becoming coarse and to reliably suppress abnormal discharge, the lower limit of the Vickers hardness is preferably 37 Hv or more, and more preferably 39 Hv or more. Further, in order to make the sputtering rate uniform and to suppress the variation in the film thickness and the micro arc discharge reliably, the upper limit of the Vickers hardness on the sputtering surface is preferably 53 Hv or less, more preferably 50 Hv or less. .

Next, a method for manufacturing a high-purity copper sputtering target material according to the present embodiment will be described.
First, an electrolytic copper having a copper purity of 99.99 mass% or more is prepared and electrolytically purified. The electrolytic copper is used as an anode, the titanium plate is used as a cathode, and the anode and the cathode are immersed in an electrolytic solution to perform electrolysis. Here, the electrolytic solution is prepared by diluting copper nitrate as a reagent with water and further adding hydrochloric acid. Thus, by adding hydrochloric acid to the copper nitrate electrolyte, the generation of nitrous acid gas can be suppressed, and the amount of impurities in the electrodeposited copper can be reduced (see Patent No. 3102177). By performing such electrolytic refining, high-purity copper in which the purity of Cu excluding O, H, N, and C is 99.9999 mass% or more can be obtained.

  In the present embodiment, the contents of Al, Si, and Fe of the anode (electrolytic copper) used in the electrolytic refining step are specified to be 1 mass ppm or less, respectively, and the contents of Al, Si, and Fe in the electrolytic solution are further defined. The amounts are specified at 1 mass ppm or less. Further, the degree of cleanliness in the room where the electrolytic refining is performed is set to class 10000 or less. By performing the electrolytic refining under such conditions, it becomes possible to reduce the Al content to 0.005 mass ppm or less, the Si content to 0.05 mass ppm or less, and the Fe content to 0.02 mass ppm or less.

  In the present embodiment, a nitric acid-based electrolyte is used to reduce S during electrolytic refining. In the electrolyte, impurities such as S are contained in glue or an organic polymer added for smoothing the cathode surface, and when these are taken into the cathode, the S concentration in the cathode increases. . Therefore, in the present embodiment, a synthetic polymer such as a mixture of polyethylene glycol and polyvinyl alcohol having a low S content is used as an additive in a nitric acid-based electrolytic solution.

Further, by dissolving Cl, O, H, and N in a high vacuum of 10 ⁻⁴ Pa or less, the Cl, O, H, and N are volatilized as a gas in the vacuum and can be reduced to a predetermined concentration.
The solubility of C in Cu increases when the dissolution temperature is increased, but if the dissolution temperature is kept low, it becomes possible to keep the concentration below a predetermined level even when dissolved in a high-purity graphite container. Specifically, if dissolved at 1150 ° C. or lower, a predetermined C concentration can be maintained.

  As described above, the purity of Cu excluding O, H, N, and C is set to 99.9999 mass% or more, the content of Al is 0.005 massppm or less, the content of Si is 0.05 massppm or less, and the content of Fe is The content is 0.02 mass ppm or less, the content of S is 0.03 mass ppm or less, the content of Cl is 0.1 mass ppm or less, the content of O is 1 mass ppm or less, the content of H is 1 mass ppm or less, and the content of N is 1 mass ppm. Hereinafter, high-purity copper having a C content of 1 mass ppm or less can be obtained.

Next, this high-purity copper is used as a raw material for melting and is melted in a vacuum melting furnace to produce a high-purity copper ingot.
Hot forging is performed on the obtained high-purity copper ingot in a temperature range of 450 to 700 ° C. Thereby, the cast structure is destroyed and adjusted to a structure having equiaxed crystal grains. Thereafter, in order to reduce the local orientation difference (KAM) of the crystal orientation, heat treatment is performed at a temperature of 500 to 700 ° C. for 1 to 2 hours.

  Next, cold working is performed on the heat-treated material. Here, it is effective to increase the rolling reduction in cold rolling in order to reduce the local orientation difference between crystal orientations in a fine and uniform manner and to reduce strain in crystal grains. By doing so, recrystallization easily occurs in the subsequent heat treatment after cold working, the local difference in the crystal orientation is small, and the strain in the crystal grain is small. For this reason, the rolling reduction in one rolling pass is preferably in the range of 15% or more and 25% or less. Further, the rolling ratio in the entire rolling is preferably set to 40% or more.

Next, recrystallization heat treatment is performed on the cold work material. The heat treatment temperature is preferably in the range of 350 ° C. to 450 ° C., and the holding time is preferably in the range of 1 hour to 2 hours.
The local orientation difference (KAM) of the crystal orientation may be adjusted to 1.5 ° or less by repeating the cold working and the heat treatment a plurality of times.

  As described above, the high-purity copper sputtering target material of the present embodiment is manufactured.

According to the high-purity copper sputtering target material of the present embodiment having the above-described configuration, the purity of Cu excluding O, H, N, and C is set to 99.9999 mass% or more. Does not need to be performed more than necessary, and it is possible to manufacture at relatively low cost.
In addition, the content of Al, which is an element that easily forms oxides, carbides, nitrides, sulfides, and chlorides and remains as foreign matter, is 0.005 massppm or less, the Si content is 0.05 massppm or less, The content is 0.02 mass ppm or less, the content of S is 0.03 mass ppm or less, the content of Cl is 0.1 mass ppm or less, the content of O is 1 mass ppm or less, the content of H is 1 mass ppm or less, and the content of N is 1 mass ppm. Hereinafter, since the content of C is set to 1 mass ppm or less, generation of foreign matter in the sputtering target can be suppressed, and occurrence of abnormal discharge due to the foreign matter can be suppressed.
Further, since the contents of S, Cl, O, H, and N, which cause gas generation during film formation, are regulated as described above, the degree of vacuum can be maintained, and film formation can be stably performed. Can be implemented.

  Further, in the high-purity copper sputtering target material according to the present embodiment, the local orientation difference (KAM) of the crystal orientation is set to 1.5 ° or less. The generation state of electrons becomes stable, and it becomes possible to suppress the occurrence of abnormal discharge.

  Further, in the high-purity copper sputtering target material of the present embodiment, the average crystal grain size is 70 μm or less, so that the sputter proceeds and irregularities corresponding to the crystal grains are formed on the sputtered surface. However, unevenness does not become large, and the occurrence of abnormal discharge can be further suppressed.

Further, in the high-purity copper sputtering target material according to the present embodiment, the Vickers hardness is 35 Hv or more, so that the crystal grain size can be made relatively small, and the sputtering proceeds and the crystal grain Even when irregularities corresponding to the above are formed, occurrence of abnormal discharge can be suppressed.
In addition, since the Vickers hardness is 55 Hv or less, internal strain in crystal grains is small, secondary electron emission during sputtering is uniform, and a sputter film can be stably formed. In addition, it is possible to suppress the sputter rate from becoming non-uniform due to the internal strain, to suppress the formation of large irregularities on the sputter surface due to the progress of sputtering, and to suppress the occurrence of abnormal discharge.

As described above, the embodiments of the present invention have been described, but the present invention is not limited thereto, and can be appropriately changed without departing from the technical idea of the present invention.
In the present embodiment, a sputtering target for forming a high-purity copper film as a wiring film has been described as an example.However, the present invention is not limited to this, and a high-purity copper film may be used for other purposes. Can be applied.
Further, the manufacturing method is not limited to the present embodiment, and may be manufactured by another manufacturing method.

  Hereinafter, results of an evaluation test for evaluating the high-purity copper sputtering target material according to the above-described embodiment will be described.

(Inventive Examples 1 to 7)
Electrolytic refining conditions exemplified in the embodiment using electrolytic copper containing Al of 1 mass ppm or less, Si of 1 mass ppm or less, Fe of 1 mass ppm or less, and other impurities (excluding O, H, N, and C) of 20 mass ppm or less. , To produce a copper raw material.
The raw material manufactured by the above manufacturing method was put into a crucible made of high-purity carbon, and was melted under vacuum (at a pressure of 10 ⁻⁵ Pa) at 1130 ° C. Thereafter, it was poured into a mold made of high-purity carbon in a vacuum state (pressure of 10 ⁻⁵ Pa) to prepare a high-purity copper ingot having a diameter of 150 mm and a height of 200 mm.

The obtained high-purity ingot was hot forged at 500 ° C., and then heat-treated at 600 ° C. for 2 hours.
Next, the above heat-treated material was subjected to cold rolling at a rolling reduction of 20% to obtain a cold-rolled sheet having a thickness of 10 mm. The rolling reduction at this time was 95%.
Next, the cold-worked material was subjected to a heat treatment at a temperature of 400 ° C. and a holding time of 1.5 hours.
Then, it was cut out to a diameter of 125 mm and a thickness of 5 mm, used as a high-purity sputtering target material, and HIP-bonded to a Cr-Zr-Cu (C18150) backing plate.

(Example 8 of the present invention)
Electrolytic refining conditions exemplified in the embodiment using electrolytic copper containing Al of 1 mass ppm or less, Si of 1 mass ppm or less, Fe of 1 mass ppm or less, and other impurities (excluding O, H, N, and C) of 20 mass ppm or less. , To produce a copper raw material.
The raw material manufactured by the above manufacturing method was put into a crucible made of high-purity carbon, and was melted under vacuum (at a pressure of 10 ⁻⁵ Pa) at 1130 ° C. Thereafter, it was poured into a mold made of high-purity carbon in a vacuum state (pressure of 10 ⁻⁵ Pa) to prepare a high-purity copper ingot having a diameter of 150 mm and a height of 200 mm.

The obtained high-purity ingot was hot forged at 500 ° C., and then heat-treated at 500 ° C. for 2 hours.
Next, the above heat-treated material was subjected to cold rolling at a rolling reduction of 20%. The rolling ratio at this time was 80%.
Next, the cold-worked material was subjected to a heat treatment at a temperature of 500 ° C. for a holding time of 2 hours.
Then, it was cut out to a diameter of 125 mm and a thickness of 5 mm, used as a high-purity sputtering target material, and HIP-bonded to a Cr-Zr-Cu (C18150) backing plate.

(Example 9 of the present invention)
Electrolytic refining conditions exemplified in the embodiment using electrolytic copper containing Al of 1 mass ppm or less, Si of 1 mass ppm or less, Fe of 1 mass ppm or less, and other impurities (excluding O, H, N, and C) of 20 mass ppm or less. , To produce a copper raw material.
The raw material manufactured by the above manufacturing method was put into a crucible made of high-purity carbon, and was melted under vacuum (at a pressure of 10 ⁻⁵ Pa) at 1130 ° C. Thereafter, it was poured into a mold made of high-purity carbon in a vacuum state (pressure of 10 ⁻⁵ Pa) to prepare a high-purity copper ingot having a diameter of 150 mm and a height of 200 mm.

The obtained high-purity ingot was hot forged at 500 ° C., and then heat-treated at 650 ° C. for 2 hours.
Next, the above heat-treated material was subjected to cold rolling at a rolling reduction of 20%. The rolling reduction at this time was 95%.
Next, the cold-worked material was subjected to a heat treatment at a temperature of 350 ° C. for a holding time of 1 hour.
Then, it was cut out to a diameter of 125 mm and a thickness of 5 mm, used as a high-purity sputtering target material, and HIP-bonded to a Cr-Zr-Cu (C18150) backing plate.

(Comparative example)
In Comparative Example 1, electrolysis was performed without adding hydrochloric acid to the electrolytic solution, and electrolysis was performed in a general room instead of the clean room. Normal glue and ethylene glycol were used as additives for smoothing the cathode. Melt casting was performed at 1300 ° C. using a high-purity graphite crucible in a nitrogen atmosphere at atmospheric pressure. The obtained ingot (diameter 150 mm × height 200 mm) is hot forged at 500 ° C. to break the cast structure, made into an equiaxed crystal, and then cold-rolled at a rolling reduction of 5% without heat treatment. Heat treatment was performed at 450 ° C. for 1 hour. The rolling reduction at this time was 40%.

In Comparative Example 2, electrolytic purification was performed in a general room, and electrolysis was performed using glue and ethylene glycol as additives. Using a high-purity graphite crucible, melting was performed at 1300 ° C. in a vacuum (at a pressure of 10 ⁻⁵ Pa). The obtained ingot (having the same shape) is similarly hot forged at 500 ° C. to break the cast structure, made into an equiaxed crystal, and then cold-rolled at a rolling reduction of 10% without heat treatment. A heat treatment for one hour was performed. The rolling ratio at this time was 80%.

  In Comparative Example 3, electrolytic purification was performed in a general room, and polyethylene glycol and polyvinyl alcohol were used as additives during electrolysis. Melting was performed at 1150 ° C. using a high-purity graphite crucible at atmospheric pressure in a nitrogen atmosphere instead of vacuum melting. The obtained ingot was similarly forged, cold-rolled at a rolling reduction of 10% without heat treatment, and heat-treated at 400 ° C. for 1 hour. The rolling ratio at this time was 60%.

  In Comparative Example 4, melting was performed at atmospheric pressure in a nitrogen atmosphere, and melting was performed at 1300 ° C. using a graphite crucible. The obtained ingot was hot-forged at 500 ° C., cold-rolled at a rolling reduction of 10% without heat treatment, and heat-treated at 400 ° C. for 1 hour. The rolling ratio at this time was 60%.

  About the obtained sputtering target material, the following procedures evaluated component composition (impurity amount), KAM, average crystal grain size, Vickers hardness, and abnormal discharge frequency. Tables 1 and 2 show the evaluation results.

(Impurity amount)
The analysis of the impurity elements except for O, H, N, and C was performed using a glow discharge mass spectrometer (VG-9000, manufactured by VG Elemental). The analysis procedure was performed according to ASTM.
The analysis of O was carried out by an inert gas melting-infrared absorption method (JIS H 1067). Specifically, the analysis was performed according to JIS Z 2613 using TCEN600 manufactured by LECO.
The analysis of H was performed by the inert gas melting-heat conduction method. Specifically, the analysis was performed using RHEN602 manufactured by LECO in accordance with JIS Z2614.
The analysis of N was performed by the inert gas melting-heat conduction method. Specifically, the analysis was performed using TCEN600 manufactured by LECO.
The analysis of C was performed by a combustion-infrared absorption method. Specifically, analysis was performed according to JIS Z 2615 using CSLS600 manufactured by LECO.

(Measurement of KAM)
First, for each sample, a longitudinal section (viewed in the TD direction) along the rolling direction (RD direction) is mechanically polished using water-resistant abrasive paper and diamond abrasive grains, and then finish-polished using a colloidal silica solution. Was done. Then, an EBSD measuring device (Schottky field emission scanning electron microscope JSM-7001F manufactured by Nidec Corporation, OIM Data Collection manufactured by EDAX / TSL) and analysis software (OIM Data Analysis ver. 5.2 manufactured by EDAX / TSL). ) Was used. The acceleration voltage of the electron beam of the EBSD measuring device was 15 kV, and the measurement visual field was 800 μm × 1200 μm. The shape of an arbitrary measurement point was a regular hexagon, and the average value of the angular difference in crystal orientation between the EBSD measurement point measured at 2.5 μm intervals and six EBSD measurement points adjacent to the measurement point was determined. However, adjacent measurement points having an angle difference of 5 ° or more were regarded as having a grain boundary between the measurement points, and were excluded when calculating the average value.

(Average crystal grain size)
The average crystal grain size was measured based on JIS H 0501: 1986 (cutting method) by observing a microstructure on a rolled surface (ND surface) using an optical microscope.

(Vickers hardness)
The hardness of the sample was measured on a surface used as a target with a Macro Vickers hardness tester in accordance with JIS Z 2244.

(Abnormal discharge)
The sputtering method was a DC magnetron sputtering method. A target to be sputtered was attached to the cathode in the chamber, and vacuum was drawn so that the ultimate vacuum was 5 × 10 ⁻⁴ Pa or less. First, in order to remove stains and processing flaws on the target processing surface, pre-sputtering was performed by gradually increasing the sputtering power, and the sputtering power was increased to 3000 W. The power for pre-sputtering was 660 Wh.
Subsequently, discharging and stopping for 1 minute at a sputtering power of 3000 W and a sputtering pressure of 0.4 Pa were repeated until the sputtering power reached 10 kWh. Then, the number of abnormal discharges generated during the discharge was measured by a micro arc monitor (MAM Genesis) manufactured by Landmark Technology.

In Comparative Example 1, the amount of impurities was large, the purity of copper was out of the range of the present invention, the value of KAM was also out of the range of the present invention, and the number of abnormal discharges was as large as 770.
In Comparative Example 2, the contents of Al, Si, Fe, and S were outside the range of the present invention, and the value of KAM was outside the range of the present invention. The number of abnormal discharges was as large as 550.
In Comparative Example 3, the contents of Cl, O, H, and N were outside the range of the present invention, and the value of KAM was outside the range of the present invention, and the number of abnormal discharges was as large as 650.
In Comparative Example 4, the contents of Cl, O, H, N, and C were out of the range of the present invention, and the number of abnormal discharges was as large as 800 times.

On the other hand, in the example of the present invention in which the purity of copper, the amount of impurities, and the value of KAM were within the range of the present invention, the number of abnormal discharges was 190 times or less.
From the above, according to the example of the present invention, it is possible to provide a high-purity copper sputtering target material that can suppress occurrence of abnormal discharge even when a high voltage is applied and can perform stable film formation. confirmed.

Claims (1)

The purity of Cu excluding O, H, N, and C is 99.99998 mass% or more, the content of Al is 0.005 massppm or less, the content of Si is 0.05 massppm or less, and the content of Fe is 0.02 massppm. Hereinafter, the content of S is 0.03 mass ppm or less, the content of Cl is 0.1 mass ppm or less, the content of O is 1 mass ppm or less, the content of H is 1 mass ppm or less, the content of N is 1 mass ppm or less, and the content of C. Is 1 massppm or less,
Ri der local orientation differences 1.5 ° or less crystal orientation obtained by the crystal orientation measurement using electron backscatter diffraction,
A high-purity copper sputtering target material having an average crystal grain size of 70 μm or less and a Vickers hardness of 35 to 50 Hv .