JP4582465B2 - High purity nickel or nickel alloy target and method for producing the same - Google Patents

Description

  The present invention relates to a nickel or nickel alloy sputtering target excellent in film uniformity (film thickness uniformity) and plasma ignition (ignition) properties, and a method for producing the same.

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

  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.

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, as a gate material, nickel or nickel alloy is used instead of cobalt because of its low silicidation temperature, low electrical resistance of the film, and low silicon used in the silicidation reaction. Proposals to use have been made.

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 or a nickel alloy, if the thickness of the nickel or nickel alloy target is about 5 mm due to improvements in the magnetron sputtering apparatus such as using a strong magnet, a sufficient film forming speed is achieved. Can be obtained.
However, in other words, in a target such as nickel or a nickel alloy, it is necessary to reduce the thickness to 5 mm or less, preferably 3 mm or less, and to process the target so as to obtain a uniform film. There are challenges.
In addition, when using a target with non-uniform magnetic characteristics in the sputter plane, there is a problem that the deepest part of the erosion part is distorted and a predetermined film thickness distribution cannot be obtained. This is especially true.

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 or nickel alloy target utilizes this magnetic anisotropy, but has a drawback that strain or the like exists in the internal structure as it is.
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 film formation characteristics described above, the film uniformity (thickness uniformity) has a great influence on the characteristics of the gate film, and is a big problem particularly in the recent 300 mm wafer process.

  The present invention has been made in view of the above-mentioned problems or drawbacks, and can improve film uniformity (film thickness uniformity) even in a manufacturing process using a 300 mm wafer, and plasma. An object of the present invention is to provide a high-purity nickel or nickel alloy target for magnetron sputtering excellent in ignition (ignition) property and a method for producing the same.

In order to solve the above-mentioned problems, the present inventor has obtained the knowledge that, in the production of a sputtering target, it is rather better to have a high permeability in order to improve the uniformity (thickness uniformity) of the sputtered film. Furthermore, by improving the processing process, the film uniformity (thickness uniformity) can be improved, and stable production is achieved by magnetron sputtering using the high-purity nickel or nickel alloy target obtained thereby. It was found that a nickel or nickel alloy thin film with good reproducibility and quality can be obtained under conditions.
The present invention is based on this finding,
1. A high-purity nickel or nickel alloy target for magnetron sputtering, in which the magnetic permeability of the target is 100 or more , in the case of high-purity nickel, the average crystal grain size is 323 μm or more and 1215 μm or less, and in the case of a high-purity nickel alloy, the average crystal grain size Is 23.5 μm or more and 1290 μm or less, does not include coarse crystal grains grown more than 5 times the average crystal grain size, and has excellent uniformity with sputtered film uniformity (%, 3σ) of 10% or less A high-purity nickel or nickel alloy target for magnetron sputtering is provided.

The present invention further provides 2. After hot forging high-purity nickel or nickel alloy with a purity of 4N5 (99.995 wt%) or higher, it is cold-rolled at a rolling rate of 30% or higher and recrystallized at a temperature of 300 ° C or higher. In the case of a high purity nickel alloy, the cold rolling and the heat treatment are repeated at least twice, the magnetic permeability of the target is 100 or more, and in the case of high purity nickel, the average grain size is 323 μm or more and 1215 μm or less. 2. Method for producing high-purity nickel or nickel alloy target for magnetron sputtering having an average crystal grain size of 23.5 μm or more and 1290 μm or less and excellent uniformity of sputtered film (%, 3σ) of 10% or less 3. A method for producing a high-purity nickel or nickel alloy target for magnetron sputtering having excellent uniformity of the sputtered film according to 2 above, wherein the purity is 5N (99.999% by weight) or more. 4. The method for producing a high-purity nickel or nickel alloy target for magnetron sputtering excellent in uniformity of the sputtered film according to the above 2 or 3 , wherein hot forging of the high-purity nickel or nickel alloy is performed. High purity nickel or nickel for magnetron sputtering excellent in sputtered film uniformity as described in any one of 2 to 4 above, which does not contain coarse crystal grains grown more than 5 times the average crystal grain size An alloy target manufacturing method is provided.

  The high-purity nickel or nickel alloy target for magnetron sputtering according to the present invention and the method for producing the same have no abnormal crystal grains having a uniform crystal grain size and coarse, and even in a film forming process using a 300 mm wafer, the film uniformity ( (Uniformity of film thickness) and plasma ignition (ignition) can be improved.

In producing a high-purity nickel or nickel alloy target, first, high-purity nickel or a nickel alloy 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 400 ° C. or higher. 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.
It is important that the magnetic permeability of this high-purity nickel or nickel alloy target is 100 or more, which is one of the major features of the present invention. This is achieved by the manufacturing process described above.

As described above, when the magnetic permeability is high, plasma is difficult to occur and sputtering is difficult. As a general rule, the magnetic permeability is made as low as possible. However, it has been found that when the magnetic permeability is high, the target shape is changed by erosion by sputtering, whereby the change in magnetic flux is reduced and the variation in film formation uniformity is reduced.
In other words, the lower the permeability, the larger the leakage magnetic field, and the higher the plasma density near the erosion part. As this erosion progresses, the sputter deposition in this part becomes larger, and the uniformity changes throughout the target life. It will be bigger.
The present invention improves the uniformity of the sputtered film using the effect of such a high magnetic permeability, and is based on a technical idea completely different from the conventional one.

Further, high-purity nickel or nickel alloy is a soft material, tends to cause abnormal grain growth, and tends to have a non-uniform metal structure in which coarse grains are mixed in fine grains. This heterogeneous structure greatly affects the film uniformity.
In addition, it is considered that such coarse particles in the internal structure of the high-purity nickel or nickel alloy target adversely affect the ignition (ignition) property of the plasma.
As described above, in order to form a suitable plasma during magnetron sputtering, it is necessary to make the nickel or nickel alloy target 5 mm or less, preferably about 3 mm in thickness. If there is a heterogeneous texture of the target, it will have a large effect on 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.
Therefore, it is desirable that the high-purity nickel or nickel alloy target for magnetron sputtering does not contain coarse crystal grains that have grown to be five times or more the average crystal grain size. This further improves the uniformity of the film and the ignition of the plasma.

In order to make such a nickel or nickel alloy target having a uniform structure that does not cause abnormal grain growth, an ingot in which the solidified structure is broken as described above is cold-rolled at a rolling rate of 30% or more and 300 ° C. It is important to repeat the heat treatment at the above temperature twice or more to form a flat plate. In addition, the target plate can be made flat by repeating such processing.
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 300 ° C., the magnetic permeability does not become as large as that considered in the present invention. Therefore, the heat treatment range is set to 300 ° C. or higher.
In addition, in a single cold rolling at a rolling rate of 30% or more and heat treatment at a temperature of 300 ° C. or higher (even if strong processing of about 80%), the coarse structure in which abnormal grains have grown is sufficiently obtained. It cannot be lost.
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 or nickel alloy target for magnetron sputtering excellent in film uniformity and plasma ignition (ignition) properties can be produced.

The high-purity nickel or nickel alloy target is preferably a high-purity nickel or nickel alloy having a purity of 4N5 (99.995% by weight) or more, and further 5N (99.999% by weight) or more.
Nickel alloys include Ni-Ti, Ni-Zr, Ni-Hf, Ni-V, Ni-Nb, Ni-Ta, Ni-Cr, Ni-Co, Ni-Pt, Ni-Pd, Ni-Ir, Ni -Fe, Ni-Mn, etc. can be mentioned. Needless to say, the alloy element to be added does not have such a content that the properties as a ferromagnetic material greatly change, and the added amount is about 0.5 to 7 at%.
Further, it is desirable that the average crystal grain size in the target is 20 to 1200 μm, and the variation in the average crystal grain size on the erosion surface of sputtering is within a variation coefficient of 20%.
As a result, a suitable high-purity nickel or nickel alloy target for magnetron sputtering excellent in film uniformity and plasma ignition (ignition) throughout the target life can be obtained.
In addition, about the nickel alloy shown to the following Example and comparative example, although only a part of the said nickel alloy is illustrated, the same result was obtained also in any alloy.

  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.

( Reference Examples 1-2, Examples 3-5 )
Electron beam melting was performed using nickel having a purity of 99.995% as a raw material, and this was cast into an ingot (120φ × 70 h). 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 strain was about 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 300 ° C to 600 ° C for 1 hour, and recrystallized. Next, this was further cold-rolled at a rolling rate of 30 to 60%, heat-treated at 300 to 600 ° 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 116 to 1215 μm as shown in Table 1, and a target having a structure in which abnormal crystal grains were not observed was obtained. The average crystal grain size of 116 μm and 137 μm is a reference example . Moreover, the magnetic permeability of this nickel target was 121-255, and it had favorable flatness. In addition, the observation of the structure and the measurement of the magnetic permeability were carried out by measuring the targets uniformly at 17 points in a radial manner, and taking the average value. The following examples and comparative examples were measured in the same manner.

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 calculated from a resistance value of 49 points by a four-terminal method indirectly by depositing a 1000-mm film on a new wafer every target life of about 5 kwh.
The measurement results of the film uniformity were all 10% or less, and lasted up to a target life of 90 kwh (sputtering power 1 kw), indicating an excellent film uniformity. The details are also shown in Table 1. However, the target life of 0 to 10 kWh was an unstable period and was outside the measurement range.
In addition, although the ignition (ignition) property of plasma is not displayed in Table 1, all were favorable.

(Comparative Examples 1-8)
Electron beam melting was performed using nickel having a purity of 99.99% as a raw material in the same manner as in the examples, 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 strain was about 5.
This was cold-rolled at a rolling rate of 50 to 80% and heat-treated at 300 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. Coarse crystal grains were observed in the target structure.

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 12 to 20, and the film uniformity was extremely bad. The details are also shown in Table 1. In particular, in Comparative Examples 1 to 8, there was a tendency that the uniformity of the film suddenly deteriorated after the target life exceeded 40 kwh.
In addition, although the ignition (ignition) property of plasma is not displayed in Table 1, the ignition property was poor.

(Examples 6 to 10)
Electron beam melting was performed using nickel of purity 99, 995% as a raw material. Separately, titanium with a purity of 99.995% is used as a raw material, and 5nm% of titanium is added to the nickel. Then, it is melted in a cold wall type vacuum induction furnace to form a nickel-titanium alloy, which is cast and ingot. (120φ × 70 h).
The ingot was subjected to a soaking treatment (held at 750 to 1150 ° C. for 2 hours), and then hot forging was performed. The starting temperature of hot forging was 750 ° C. to 1150 ° C., and the true forging was performed at about 5. In hot forging below 750 ° 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 300 ° C to 600 ° C for 1 hour, and recrystallized. Next, this was further cold-rolled at a rolling rate of 30 to 60%, heat-treated at 300 to 600 ° C. for 1 hour, and recrystallized.

A sample was cut out from the rolled plate obtained in this manner, and used as a disk-shaped nickel alloy target sample having a thickness of 3 mm and a diameter of 440 mm. The average particle size of the target sample was 24 to 850 μm as shown in Table 2, and a target having a structure in which abnormal crystal grains were not observed was obtained. Moreover, the magnetic permeability of this nickel alloy target was 107 to 235 and had good flatness.
Next, magnetron sputtering was performed using this nickel alloy target, and the uniformity (%, 3σ) of the film and the ignition (ignition) property of the plasma 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 10% or less, and lasted up to a target life of 90 kwh (sputtering power 1 kw), indicating an excellent film uniformity. The details are similarly shown in Table 2.
In addition, although the ignition (ignition) property of plasma is not displayed in Table 2, all were favorable.

(Comparative Examples 9-16)
Electron beam melting was performed using nickel of purity 99, 995% as a raw material. Separately, titanium with a purity of 99.995% is used as a raw material, and 5nm% of titanium is added to the nickel. Then, it is melted in a cold wall type vacuum induction furnace to form a nickel-titanium alloy, which is cast and ingot. (120φ × 70 h).
The ingot was subjected to a soaking treatment (held at 750 to 1150 ° C. for 2 hours), and then hot forging was performed. The starting temperature of hot forging was 750 ° C. to 1150 ° C., and the true forging was performed at about 5. In hot forging below 750 ° 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 50 to 80% and heat-treated at 300 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, and used as a disk-shaped nickel alloy target sample having a thickness of 3 mm and a diameter of 440 mm. Coarse crystal grains were observed in the target structure.

Next, magnetron sputtering was performed using this nickel alloy target under the same conditions, and the film uniformity (%, 3σ) and plasma ignition (ignition) 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 13 to 22, and the film uniformity was extremely bad. The details are similarly shown in Table 2. In particular, in Comparative Examples 9 to 16, there was a tendency that the uniformity of the film suddenly deteriorated when the target life exceeded 30 kwh.
In Table 2, the ignition (ignition) property of the plasma is not displayed, but the ignition property is poor.

(Examples 11 to 15)
Electron beam melting was performed using nickel of purity 99, 995% as a raw material. Separately, manganese with a purity of 99.995% is used as a raw material, 0.5 at% of manganese is added to this nickel, and it is melted in an argon gas atmosphere in a cold wall type vacuum induction furnace to form a nickel-manganese alloy. Ingot (120φ × 70h).
The ingot was subjected to a soaking treatment (held at 750 to 1150 ° C. for 2 hours), and then hot forging was performed. The starting temperature of hot forging was 750 ° C. to 1150 ° C., and the true forging was performed at about 5. In hot forging below 750 ° 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 300 ° C to 600 ° C for 1 hour, and recrystallized. Next, this was further cold-rolled at a rolling rate of 30 to 60%, heat-treated at 300 to 600 ° C. for 1 hour, and recrystallized.

A sample was cut out from the rolled plate obtained in this manner, and used as a disk-shaped nickel alloy target sample having a thickness of 3 mm and a diameter of 440 mm. The average particle diameter of the target sample was 62 to 1290 μm as shown in Table 3, and a target having a structure in which abnormal crystal grains were not observed was obtained. Moreover, the magnetic permeability of this nickel alloy target was 105 to 215 and had good flatness.
Next, magnetron sputtering was performed using this nickel alloy target, and the uniformity (%, 3σ) of the film and the ignition (ignition) property of the plasma 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 10% or less, and lasted up to a target life of 90 kwh (sputtering power 1 kw), indicating an excellent film uniformity. The details are similarly shown in Table 3.
In Table 3, the plasma ignition (ignition) properties are not shown, but all were good.

(Comparative Examples 17-24)
Electron beam melting was performed using nickel of purity 99, 995% as a raw material. Separately, manganese with a purity of 99.995% is used as a raw material, 0.5 at% of manganese is added to this nickel, and it is melted in an argon gas atmosphere in a cold wall type vacuum induction furnace to form a nickel-manganese alloy. Ingot (120φ × 70h).
The ingot was subjected to a soaking treatment (held at 750 to 1150 ° C. for 2 hours), and then hot forging was performed. The starting temperature of hot forging was 750 ° C. to 1150 ° C., and the true forging was performed at about 5. In hot forging below 750 ° 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 50 to 80% and heat-treated at 300 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, and used as a disk-shaped nickel alloy target sample having a thickness of 3 mm and a diameter of 440 mm. Coarse crystal grains were observed in the target structure.
Next, magnetron sputtering was performed using this nickel alloy target under the same conditions, and the film uniformity (%, 3σ) and plasma ignition (ignition) 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 15 to 25, and the film uniformity was extremely bad. The details are similarly shown in Table 3. In particular, in Comparative Examples 17 to 24, there was a tendency that the uniformity of the film suddenly deteriorated when the target life exceeded 30 kwh.
In Table 3, the plasma ignition (ignition) property is not shown, but the ignition property is poor.

  The high-purity nickel or nickel alloy target for magnetron sputtering according to the present invention and the method for producing the same have no abnormal crystal grains having a uniform crystal grain size and coarse, and even in a film forming process using a 300 mm wafer, the film uniformity ( (Uniformity of film thickness) and plasma ignition (ignition) can be improved, so that it can be used as a material for forming magnetic films on magnetic recording media for hard disks, magnetic heads, LSI chips, etc. Is preferred.

Claims (4)

A high-purity nickel or nickel alloy target for magnetron sputtering having a purity of 4N5 (99.995% by weight) or more, and in the case of nickel, the magnetic permeability is 185 or more and 255 or less , the average crystal grain size is 323 μm or more and 1215 μm or less, In the case of a nickel alloy, the alloy elements include Ti, Zr, Hf, V, Nb, Ta, Cr, Co, Pt, Pd, Ir, Fe, and Mn, and the addition amount is 0.5 to 5 at% and is ferromagnetic. The magnetic permeability is 105 or more and 235 or less , the average crystal grain size is 23.5 μm or more and 1290 μm or less, and any nickel or nickel alloy target has coarse crystal grains grown to 5 times or more of the average crystal grain size. High purity Ni for magnetron sputtering, characterized in that the sputtered film uniformity (%, 3σ) is 10% or less. A nickel or nickel alloy target.   After hot forging high-purity nickel or nickel alloy with a purity of 4N5 (99.995 wt%) or higher, it is cold-rolled at a rolling rate of 30% or higher and recrystallized at a temperature of 300 ° C or higher. The method for producing a high-purity nickel or nickel alloy target for magnetron sputtering according to claim 1, wherein the cold rolling and the heat treatment are repeated at least twice.   The method for producing a high-purity nickel or nickel alloy target for magnetron sputtering according to claim 2, wherein the purity is 5N (99.999% by weight) or more. 4. The method for producing a high-purity nickel or nickel alloy target for magnetron sputtering according to claim 2, wherein the forging is carried out during hot forging of the high-purity nickel or nickel alloy.