JP4006620B2 - Manufacturing method of high purity nickel target and high purity nickel target - Google Patents

Description

【００１７】
（比較例１〜比較例１３）
実施例と同様の純度９９．９９９％のニッケルを原料として電子ビーム溶解し、これを鋳造してインゴット（１２０φ×７０ｈ）とした。このインゴットを均熱化処理（９００〜１１５０°Ｃで２時間保持）した後、熱間鍛造を行った。熱間鍛造の開始温度は９００°Ｃ〜１１５０°Ｃであり、真歪み約５．５で行った。
これを圧延率５０〜８０％で冷間圧延し、２５０°Ｃ〜６００°Ｃで１時間熱処理した。この冷間圧延と熱処理は１回である。
これによって得た圧延板から試料を切り出し、厚さ３ｍｍ、直径４４０ｍｍの円盤状ニッケルターゲット試料とした。
ターゲット試料の平均粒径は下表に示す通り２０．５〜２１０．３μｍにあり、粗大結晶粒（１４９〜１１７０μｍ）が存在する組織のターゲットが得られた。なお、熱処理２００°Ｃの比較例１及び比較例９については、再結晶せず圧延組織が残存していた。
上記比較例１〜１３のニッケルターゲット製造条件の詳細並びに結晶組織の観察及び結晶粒径の測定結果を、表１に示す。なお、結晶粒径の測定及び組織観察位置は、実施例と同様に円盤状のニッケルターゲットを放射状に均一に１７点をとって観察し、結晶粒径の測定については、それらの平均値とした。
【００１８】
次に、このニッケルターゲットを用いて実施例と同一の条件でマグネトロンスパッタリングを実施し、膜のユニフォーミティ（％、３σ）及びプラズマのイグニッション（点弧）性を測定及び観察した。なお、膜のユニフォーミティの測定は間接的に４端子法による抵抗値から計算した。
膜のユニフォーミティの測定結果は上限値が７．５〜１５の範囲にあり、膜のユニフォーミティが著しく悪い結果となった。その詳細を、同様に表１に示す。なお、表１には、プラズマのイグニッション（点弧）性は不良であった。
【００１９】
（比較例１４〜比較例１９）
実施例と同様の純度９９．９９９％のニッケルを原料として電子ビーム溶解し、これを鋳造してインゴット（１２０φ×７０ｈ）とした。このインゴットを均熱化処理（９００〜１１５０°Ｃで２時間保持）した後、熱間鍛造を行った。熱間鍛造の開始温度は９００°Ｃ〜１１５０°Ｃであり、真歪み約５．５で行った。
但し、比較例１４と１５については、第１回目の圧延を、２０又は２５％の低い圧延率で冷間圧延し、３００°Ｃで１時間熱処理した。
また比較例１６と１７については、第２回目の圧延を、２０又は２５％の低い圧延率で冷間圧延し、さらに３００°Ｃで１時間熱処理した。このように２回の冷間圧延と２回の熱処理を実施したが、冷間圧延率は本発明の条件から逸脱している。
さらに比較例１８と比較例１９については、比較例１８では一回目の熱処理温度を５００°Ｃに、比較例１９では二回目の熱処理温度を６００°Ｃにしたものであるが、結晶粒のばらつきが大きくなった。
これによって得た圧延板から試料を切り出し、厚さ３ｍｍ、直径４４０ｍｍの円盤状ニッケルターゲット試料とした。
ターゲット試料の平均粒径は下表に示す通り２２．３〜８１．６μｍにあり、粗大結晶粒（２８８〜４０２μｍ）が存在する組織のターゲットが得られた。
上記比較例１４〜１９のニッケルターゲット製造条件の詳細並びに結晶組織の観察及び結晶粒径の測定結果を、表１に示す。なお、結晶粒径の測定及び組織観察位置は、実施例と同様に円盤状のニッケルターゲットを放射状に均一に１７点をとって観察し、結晶粒径の測定については、それらの平均値とした。
【００２０】
次に、このニッケルターゲットを用いて実施例と同一の条件でマグネトロンスパッタリングを実施し、膜のユニフォーミティ（％、３σ）及びプラズマのイグニッション（点弧）性を測定及び観察した。なお、膜のユニフォーミティの測定は間接的に４端子法による抵抗値から計算した。
膜のユニフォーミティの測定結果は上限値が６．７〜１２の範囲にあり、膜のユニフォーミティが著しく悪い結果となった。その詳細を、同様に表１に示す。なお、表１には、プラズマのイグニッション（点弧）性は不良であった。
【００２１】
【発明の効果】
本発明のマグネトロンスパッタリング用高純度ニッケルターゲットの製造方法及び同高純度ニッケルターゲットは、結晶粒径が均一で粗大化した異常結晶粒がなく、３００ｍｍウエハを用いた成膜プロセスにおいても、膜のユニフォーミティ（膜厚の均一性）とプラズマのイグニッション（点弧）性を良好にすることができるという優れた効果を有する。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method of manufacturing a nickel sputtering target excellent in film uniformity (film thickness uniformity) and plasma ignition (ignition), and a high-purity nickel target obtained thereby.
[0002]
[Prior art]
A sputtering method is widely used as a method for forming a magnetic film on a magnetic recording medium for a hard disk, a magnetic head, an LSI chip, or the like.
In the sputtering method, a substrate serving as an anode and a target serving as a cathode are opposed to each other, and an electric field is generated by applying a high voltage between these substrate and target in an inert gas atmosphere. Electrons and inert gas collide to form a plasma. The cations in the plasma collide with the target surface and strike target atoms, and the ejected atoms adhere to the opposing substrate surface to form a film. This is based on the principle that
[0003]
Currently, most of sputtering uses a so-called magnetron sputtering method. Magnetron sputtering is a method in which a magnet is set on the back side of a target and a magnetic field is generated in the direction perpendicular to the electric field on the target surface to perform sputtering. In such an orthogonal electromagnetic field space, plasma stabilization and densification are achieved. It is possible to increase the sputtering rate.
[0004]
In general, using such a magnetron sputtering method, a magnetic thin film such as a ferromagnetic material such as Ni or Co or a ferrimagnetic material is formed on a substrate. Magnetron sputtering captures electrons in the magnetic field and efficiently ionizes the sputtering gas. However, when the target has magnetization, the target itself affects the magnetic field in the vicinity of the sputtering surface due to the magnetic characteristics.
In recent years, there have been proposals to use nickel instead of cobalt, particularly as a gate material because of its low silicidation temperature, low film resistance, and low silicon used in the silicidation reaction. ing.
[0005]
In general, a ferromagnetic material has a problem that it is extremely difficult to perform magnetron sputtering in order to magnetically form a closed circuit. However, recently, even with a ferromagnetic target such as nickel, a sufficient film forming speed can be obtained if the thickness of the nickel target is about 5 mm by improving the magnetron sputtering apparatus such as using a strong magnet. ing.
However, in other words, a target such as nickel has a big problem that it is necessary to process the target so that the thickness is reduced to 5 mm or less, preferably 3 mm or less, and a uniform film is obtained. .
In addition, when using a target with non-uniform magnetic characteristics (with magnetic anisotropy) in the sputtering surface, the deepest part of the erosion part is distorted, and the expected film thickness distribution cannot be obtained. It can be said that this tendency is particularly remarkable in the nickel target utilizing the property.
[0006]
Naturally, the target material subjected to rolling is not isotropic. That is, it becomes a texture in which crystal grains are extended in one direction. For this reason, when viewed three-dimensionally, anisotropy occurs in the magnetic characteristics even in the rolling plane.
A nickel target utilizes this magnetic anisotropy, but has a drawback that strain and the like exist in the internal structure as they are.
When a disk-shaped target is cut out from such a rolled plate to produce the target, the originally circular erosion progresses in a shape extended in one direction. Originally, since it was originally expected to form a circular erosion during film formation on a circular substrate, there is a problem that a uniform film thickness cannot be obtained on the circular substrate.
From the above, since the thickness of the normal film formation affects the magnetic characteristics, it is necessary to have a certain film thickness and be uniform. However, the gate film may be thin, and the film formation speed and film thickness are not particularly problematic.
However, in the above film formation characteristics, film uniformity (film thickness uniformity) and plasma ignition (ignition) properties have a great influence on the characteristics of the gate film. It has become.
[0007]
[Problems to be solved by the invention]
The present invention has been made in view of the above problems or disadvantages, and even in a manufacturing process using a 300 mm wafer, film uniformity (film thickness uniformity) and plasma ignition (ignition) properties are achieved. An object of the present invention is to provide a method for producing a high-purity nickel target for magnetron sputtering that can be improved and a high-purity nickel target.
[0008]
[Means for Solving the Problems]
In order to solve the above problems, the present inventor paid attention to the manufacturing process of the sputtering target, and improved the film processing uniformity (film thickness uniformity) and plasma ignition (ignition) by improving the processing process. It was possible to improve, and the knowledge that reproducible and good quality nickel thin film can be obtained under stable manufacturing conditions by magnetron sputtering using the high-purity nickel target obtained thereby was obtained. .
The present invention is based on this finding,
1. After hot forging high-purity nickel, it is cold-rolled at a rolling rate of 30% or more and further heat-treated at a temperature of 250 ° C. or more, and the cold rolling and heat treatment are repeated at least twice or more. 1. A method for producing a high-purity nickel target for magnetron sputtering having excellent film uniformity. A sputtering target made of high purity nickel having a purity of 4N5 (99.995% by weight) or more, having an average crystal grain size of 10 to 150 μm, and a variation coefficient of 18 in the variation of the average crystal grain size on the erosion surface of sputtering. 2. High-purity nickel target for magnetron sputtering excellent in film uniformity characterized by being within% 3. The high purity nickel target for magnetron sputtering according to the above item 2, which has excellent film uniformity, characterized in that the average crystal grain size is 30 to 120 μm. 4. The high-purity nickel target for magnetron sputtering according to the above 2 or 3, which is excellent in film uniformity, characterized by not containing coarse crystal grains grown to 5 times or more of the average crystal grain size. After hot forging high-purity nickel, it is cold-rolled at a rolling rate of 30% or more and further heat-treated at a temperature of 250 ° C. or more, and the cold rolling and heat treatment are repeated at least twice or more. The high purity nickel target for magnetron sputtering according to each of the above 2 to 4, which is excellent in film uniformity characterized by being obtained by the above.
[0009]
DETAILED DESCRIPTION OF THE INVENTION
In producing a high purity nickel target, first, high purity nickel is melted and cast into a block (ingot).
Next, this is hot forged, further cold-rolled at a rolling rate of 30% or higher, and heat-treated at a temperature of 250 ° C. or higher and 400 ° C. or lower. In the present invention, the cold rolling and heat treatment are repeated at least twice.
Finally, it is processed into a target shape that can be set in a flat plate or other magnetron sputtering apparatus.
High-purity nickel is a soft material in the first place, tends to cause abnormal grain growth, and tends to form a non-uniform metal structure in which coarse grains are mixed in fine grains.
And it was found that this heterogeneous structure greatly affects the film uniformity. In addition, it is considered that the presence of such coarse grains in the internal structure of the high-purity nickel target also adversely affects the ignition (ignition) property of the plasma.
[0010]
As described above, in order to form a suitable plasma during magnetron sputtering, the nickel target needs to be 5 mm or less, preferably about 3 mm thick. The presence of heterogeneous tissue will greatly affect the entire target, as the target is thin. As a result, the uniformity of the sputtering film and the ignition property of the plasma are further deteriorated.
In order to obtain a nickel target having a uniform structure that does not cause such abnormal grain growth, the ingot in which the solidified structure is broken as described above is cold-rolled at a rolling rate of 30% or more and 250 ° C. or more and 400 ° C. It is important to repeat the heat treatment at a temperature of C or less twice or more to form a flat plate. In addition, the target plate can be made flat by repeating such processing.
[0011]
If the rolling rate is less than 30%, the coarse structure in which abnormal grains have grown cannot be sufficiently broken (divided), and if it is less than 250 ° C., fine crystals cannot be produced by recrystallization. On the other hand, if the temperature exceeds 400 ° C., the recrystallized structure tends to be coarsened. Therefore, the heat treatment range is 250 ° C. or more and 400 ° C. or less. In addition, in a single cold rolling at a rolling rate of 30% or more and a heat treatment at a temperature of 250 ° C. or more and 400 ° C. or less (even if strong processing of about 80% is performed), coarse grains with abnormal grain growth The tissue cannot be lost sufficiently.
Therefore, this process needs to be repeated at least twice. Note that the cold rolling and the heat treatment are not necessarily performed under the same conditions.
Through the above steps, a high-purity nickel target for magnetron sputtering excellent in film uniformity and plasma ignition (ignition) properties can be produced.
[0012]
The high-purity nickel target is desirably high-purity nickel having a purity of 4N5 (99.995% by weight) or more, preferably 5N (99.999% by weight) or more, and has an average crystal grain size in the target. It is 10 to 150 μm, preferably 30 to 120 μm, and it is desirable that the variation of the average crystal grain size on the erosion surface of sputtering is within a variation coefficient of 18%. As a result, it is possible to obtain a suitable high-purity nickel target for magnetron sputtering excellent in film uniformity and plasma ignition.
Furthermore, it is desirable that the high-purity nickel target for magnetron sputtering does not contain coarse crystal grains that have grown to 5 or more times the crystal grain size. This further improves the uniformity of the film and the ignition of the plasma.
[0013]
Examples and Comparative Examples
Hereinafter, description will be made based on Examples and Comparative Examples. In addition, a present Example is an example to the last, and is not restrict | limited at all by this example. In other words, the present invention is limited only by the scope of the claims, and includes various modifications other than the embodiments included in the technical idea of the present invention.
[0014]
(Example 1 to Example 5)
Electron beam melting was performed using nickel having a purity of 99.999% as a raw material, and this was cast into an ingot (120φ × 70h). After this ingot was soaked (held at 900 to 1150 ° C. for 2 hours), hot forging (kneading forging) was performed. The starting temperature of hot forging was 900 ° C. to 1150 ° C., and the true forging was performed at about 5.5. In hot forging below 900 ° C., cracks often occur, and at temperatures exceeding 1150 ° C., the material is significantly oxidized, so the temperature is set in the above range.
This was cold-rolled at a rolling rate of 30 to 60%, heat-treated at 250 ° C. to 400 ° C. for 1 hour, and recrystallized. Next, this was further cold-rolled at a rolling rate of 30 to 60%, heat-treated at 250 to 400 ° C. for 1 hour, and recrystallized.
A sample was cut out from the rolled plate obtained in this manner to obtain a discoid nickel target sample having a thickness of 3 mm and a diameter of 440 mm. The average particle diameter of the target sample was 38.6 to 142.1 μm as shown in the table below, and a target having a structure in which abnormal crystal grains were not observed was obtained.
Table 1 shows the details of the nickel target production conditions of Examples 1 to 5 above, the observation of the crystal structure, and the measurement result of the crystal grain size. In addition, the measurement of the crystal grain size and the structure observation position were observed by observing a disk-shaped nickel target at 17 points uniformly and radially, and the measurement of the crystal grain size was an average value thereof.
[0015]
Next, magnetron sputtering was performed on a 300 mm wafer using this nickel target, and the film uniformity (%, 3σ) and plasma ignition (ignition) were measured and observed. The film uniformity was indirectly calculated from the resistance value by the four-terminal method.
The measurement results of the film uniformity were all less than 4, and lasted up to a target life of 90 kwh (sputter power of 1 kw), indicating an excellent film uniformity. The details are also shown in Table 1. In addition, although the ignition (ignition) property of plasma is not displayed in Table 1, all were favorable.
[0016]
[Table 1]

[0017]
(Comparative Examples 1 to 13)
Electron beam melting was performed using nickel having a purity of 99.999% similar to that in the example as a raw material, and this was cast into an ingot (120φ × 70 h). The ingot was subjected to a soaking treatment (held at 900 to 1150 ° C. for 2 hours), and then hot forging was performed. The starting temperature of hot forging was 900 ° C. to 1150 ° C., and the true forging was performed at about 5.5.
This was cold-rolled at a rolling rate of 50 to 80% and heat-treated at 250 ° C to 600 ° C for 1 hour. This cold rolling and heat treatment are performed once.
A sample was cut out from the rolled plate obtained in this manner to obtain a discoid nickel target sample having a thickness of 3 mm and a diameter of 440 mm.
The average particle diameter of the target sample was 20.5 to 210.3 μm as shown in the table below, and a target having a structure with coarse crystal grains (149 to 1170 μm) was obtained. In Comparative Example 1 and Comparative Example 9 at a heat treatment of 200 ° C., the rolled structure remained without recrystallization.
Table 1 shows the details of the nickel target production conditions of Comparative Examples 1 to 13, the observation of the crystal structure, and the measurement result of the crystal grain size. In addition, the crystal grain size measurement and the structure observation position were observed by observing 17 points of the disk-shaped nickel target uniformly in a radial manner in the same manner as in the examples, and the measurement of the crystal grain size was an average value thereof. .
[0018]
Next, using this nickel target, magnetron sputtering was performed under the same conditions as in the example, and the uniformity (%, 3σ) of the film and the ignition (ignition) property of the plasma were measured and observed. The measurement of the film uniformity was indirectly calculated from the resistance value by the 4-terminal method.
The measurement result of the film uniformity was in the range of 7.5 to 15, and the film uniformity was extremely bad. The details are also shown in Table 1. In Table 1, the plasma ignition (ignition) property was poor.
[0019]
(Comparative Examples 14 to 19)
Electron beam melting was performed using nickel having a purity of 99.999% similar to that in the example as a raw material, and this was cast into an ingot (120φ × 70 h). The ingot was subjected to a soaking treatment (held at 900 to 1150 ° C. for 2 hours), and then hot forging was performed. The starting temperature of hot forging was 900 ° C. to 1150 ° C., and the true forging was performed at about 5.5.
However, in Comparative Examples 14 and 15, the first rolling was cold-rolled at a rolling rate as low as 20 or 25% and heat-treated at 300 ° C. for 1 hour.
In Comparative Examples 16 and 17, the second rolling was cold-rolled at a rolling rate as low as 20 or 25%, and further heat-treated at 300 ° C. for 1 hour. As described above, two cold rollings and two heat treatments were performed, but the cold rolling rate deviates from the conditions of the present invention.
Further, in Comparative Example 18 and Comparative Example 19, in Comparative Example 18, the first heat treatment temperature was set to 500 ° C., and in Comparative Example 19, the second heat treatment temperature was set to 600 ° C. Became larger.
A sample was cut out from the rolled plate obtained in this manner to obtain a discoid nickel target sample having a thickness of 3 mm and a diameter of 440 mm.
The average particle size of the target sample was 22.3 to 81.6 μm as shown in the table below, and a target having a structure with coarse crystal grains (288 to 402 μm) was obtained.
Table 1 shows the details of the nickel target production conditions of Comparative Examples 14 to 19, the observation of the crystal structure, and the measurement result of the crystal grain size. In addition, the crystal grain size measurement and the structure observation position were observed by observing 17 points of the disk-shaped nickel target evenly in the same manner as in the examples, and the crystal grain size was measured using the average value thereof. .
[0020]
Next, magnetron sputtering was performed using this nickel target under the same conditions as in the example, and the film uniformity (%, 3σ) and plasma ignition (ignition) properties were measured and observed. The measurement of the film uniformity was indirectly calculated from the resistance value by the 4-terminal method.
The measurement result of the film uniformity was in the range of 6.7 to 12, and the film uniformity was extremely bad. The details are also shown in Table 1. In Table 1, the plasma ignition (ignition) property was poor.
[0021]
【The invention's effect】
The method for producing a high-purity nickel target for magnetron sputtering of the present invention and the high-purity nickel target have a uniform crystal grain size and are free from abnormal crystal grains. It has an excellent effect that the Mitty (thickness uniformity) and plasma ignition (ignition) properties can be improved.

Claims (5)

After hot forging high-purity nickel having a purity of 4N5 (99.995 wt%) or higher, it is cold-rolled at a rolling rate of 30% or higher, and further heat treated at a temperature of 250 ° C. or higher and 400 ° C. or lower. to consist step, the cold-rolling and the heat treatment to repeat at least twice, for magnetron sputtering which is excellent in uniformity of the film an average crystal grain size of 10 to 150 m, purity of 4N5 (99.995 wt% ) A method for producing a high-purity nickel target as described above. A sputtering target made of high-purity nickel having a purity of 4N5 (99.995% by weight) or more, having an average crystal grain size of 10 to 150 μm, and a variation coefficient of 18 in the variation of the average crystal grain size on the erosion surface of sputtering. High-purity nickel target with a purity of 4N5 (99.995 wt%) or more for magnetron sputtering with excellent film uniformity of less than 10% .   The high-purity nickel target for magnetron sputtering according to claim 2, which is excellent in uniformity of a film having an average crystal grain size of 30 to 120 µm.   The high-purity nickel target for magnetron sputtering according to claim 2 or 3, which is excellent in uniformity of a film not containing coarse crystal grains grown to 5 times or more of the average crystal grain size. After hot forging high-purity nickel, it is cold-rolled at a rolling rate of 30% or more, and further heat-treated at a temperature of 250 ° C. or higher and 400 ° C. or lower. The high-purity nickel target for magnetron sputtering according to any one of claims 2 to 4, which is excellent in uniformity of a film having an average crystal grain size of 10 to 150 µm obtained by repeating twice or more.