JPH0551662B2 - - Google Patents

Description

[Detailed Description of the Invention] <Industrial Application Field> The present invention relates to a sputtering target used in the manufacture of thin-film magnetic heads or ferromagnetic thin-film resistive elements, and particularly to a sputtering target that is optimal as a cathode for a magnetron-type sputtering device. Regarding the target.

<Conventional technology> In recent years, in the field of magnetic applications, there has been a trend toward smaller magnetic cores, higher frequencies, and higher densities.In particular, in the field of magnetic recording, with the increase in recording densities, there has been a trend toward narrower tracks, shorter wavelengths, and higher frequency bands. be. For example, 8mm VTR,
Examples include fixed head digital audio, PCM, and perpendicular magnetic recording.

Although thin plates and ribbons of soft magnetic materials are being used to reduce the size and increase the frequency of magnetic elements, these materials cannot be said to be sufficiently compatible.
Therefore, soft magnetic thin films manufactured by the sputtering method are attracting attention. Although this thin film is inferior in terms of coercive force and magnetic permeability in the low frequency range, it is significantly superior in the high frequency range due to its advantageous shape. This is because the soft magnetic thin film can significantly reduce the eddy current loss characteristic of metal materials with low electrical resistance, and thus can suppress the decrease in magnetic permeability in the high frequency band.

In general, the basic principle of the sputtering method is to apply a high DC or AC voltage (several kV) between a cathode (cathode) to which a target is attached, and an anode (substrate) facing it to cause a glow discharge. It is to perform sputtering. For example, if a vacuum chamber is maintained in an argon atmosphere of 1×10 ^-1 Torr and a voltage is applied between the electrodes, a glow discharge will occur between the electrodes. This glow discharge forms argon plasma in the discharge space. The argon positive ions in this plasma are accelerated by the cathode potential drop near the cathode, collide with the target cathode surface, and evaporate the target surface in spatter. The spatter particles are deposited on a substrate disposed on the anode to form a thin film of target material.

Here, a drawback of forming a thin film using the sputtering method is that the forming speed of the thin film is slow. A magnetron type sputtering method is one of the sputtering methods that improves this drawback of slow formation speed. In the magnetron type sputtering method, an electric field and a magnetic field are applied in a two-pole sputtering method, and as a result, electrons are captured near the cathode and a region is formed near the cathode where the current caused by electrons is closed. In other words, secondary electrons ejected from the target (cathode) surface act in a direction perpendicular to the electric and magnetic fields due to the Lorentz force. Electrons trapped in the magnetic field formed on the target surface undergo cycloidal motion, collide with gas molecules, and promote ionization. Electrons that repeatedly collide lose energy each time,
While changing its orbit, it reaches the substrate (anode) and ends its life. In this way, the lifetime of the electrons is extended under the influence of the magnetic field, providing enough electrons to sustain the discharge even at low pressures, and creating a high-density plasma. Therefore, a large current density discharge is possible, and the sputtering speed can be significantly increased.

<Problems to be solved by the invention> Here, with the magnetron type sputtering method, for example,
If you try to sputter a ferromagnetic target whose main constituent element is at least one of Fe, Co, and Ni, the target will short-circuit the magnetic path of the magnet on the back side (form a closed magnetic path). Therefore, the lines of magnetic force are focused inside the target, making magnetron discharge difficult. Therefore, the following method has been devised to generate a leakage magnetic field on the target surface.

1. Make use of the magnetic field component that leaks to the surface after magnetically saturating the target by increasing the strength of the magnet on the back of the target or by reducing the thickness of the target (see Figure 2).

2. Create a gap on the target to encourage magnetic field leakage.

3 Raise the temperature of the target to reduce its magnetic permeability and encourage magnetic field leakage.

However, if you strengthen the magnet on the back of the target,
Increasing the temperature of the target not only requires modification of the sputtering device, but also makes the device large-scale and complicated, which is undesirable. Further, when the magnet 1 is arranged as shown in FIG. 2, a magnetic field is generated locally, and the ferromagnetic target 2 is locally weakened, thereby shortening the life of the target. Furthermore, if the target is partially damaged, there will be many unusable parts, resulting in a lot of waste. Note 3
is a bucking plate made of copper.

Furthermore, reducing the thickness of the target increases processing costs and shortens the life of each target, requiring frequent replacement of the target. Furthermore, providing a gap in the target by machining increases the processing cost and is not practical.

If it were possible to easily and inexpensively provide a magnetic gap on the target, there would be no need to modify the magnetron type sputtering equipment, and there would be no need to modify the magnetron type sputtering equipment, and there would be no shortening of the lifespan due to local edges of the target. This can greatly contribute to the practical application of magnetic heads.

SUMMARY OF THE INVENTION In view of the above-mentioned problems, an object of the present invention is to provide a sputtering target having a long life (high efficiency of use) and suitable as a cathode for a sputtering apparatus, particularly a magnetron type sputtering apparatus.

<Means for solving the problem> The above purpose is to disperse a non-magnetic phase on the surface and inside of a ferromagnetic sputtering target whose main constituent element is at least one of Fe, Co, and Ni. This is achieved by making it exist.
That is, referring to FIG. 1, when a non-magnetic phase 4 exists on or near the surface of the ferromagnetic target 2', this non-magnetic phase acts as a magnetic gap, and the magnet 1 on the back surface of the target 2' The magnetic flux leaks uniformly from the non-magnetic phase 4.

Since the surface of the target is worn away by sputtering, in order for the nonmagnetic phase to always exist on the target surface, this nonmagnetic phase must also exist inside the target. Moreover, if the non-magnetic phase exists locally, the target will be consumed locally and the efficiency of use will be low, so the non-magnetic phase must be present in a dispersed manner within the target.

As a ferromagnetic sputtering target,
It is a material whose constituent element is at least one of Fe, Co, and Ni. For example, Fe-Si, Fe-Si-Al,
Co−Zr, Co−Nb, Co−Cr, Co−Fe, Co−Ni,
These include Ni-Fe, Ni-Fe-Mo alloys, metal materials to which elements effective for improving magnetic properties are added, and oxide-based ferromagnetic materials.

The nonmagnetic phase may be composed of a metal, an alloy, a compound, or a nonmetallic substance such as an oxide or nitride, as long as it exists in the ferromagnetic material and can form a magnetic gap. Even if this non-magnetic phase exists, the target itself must be ferromagnetic, so the volume ratio of the non-magnetic phase is 10.
% or less is preferable. If the amount exceeds 10%, the magnetic properties of the thin film obtained by sputtering will deteriorate.

An example of a method for dispersing a nonmagnetic phase in a ferromagnetic material is shown below.

1. A ferromagnetic powder and a nonmagnetic powder that do not have mutual solubility or have a low solubility are mixed and sintered to disperse the nonmagnetic phase in the ferromagnetic material.

2. Precipitate or crystallize the nonmagnetic substance dissolved in supersaturated solid solution in the ferromagnetic material to disperse the nonmagnetic phase.

Next, examples of the present invention will be described.

<Example> 1 Ag equivalent to 1% of the weight of the molten metal was added to a molten metal adjusted to 81% Ni and 19% Fe, and after thorough stirring, the molten metal was poured into a cast iron mold to obtain an ingot. This ingot undergoes hot processing, cold processing,
Cutting was performed to produce a disc-shaped target with an outer diameter of 150 mm and a thickness of 6 mm. It was observed that a non-magnetic phase containing Ag as a main component was dispersed at and near the grain boundaries of this target. Using this target, Ar8×10 ^-3
Magnetron sputtering was performed under Torr and 3kW conditions. Usage efficiency of both targets with and without a non-magnetic phase dispersed (with the volume of the target before use as 100, calculate the volume of the target that is no longer usable, and conversely calculate the volume of the used target in %). (shown)
The former is about 25%, while the latter is about 6%.
It was %. Furthermore, in the former case, erosion (a phenomenon in which the metal is subject to wear and tear due to external force) occurred over a wide range, whereas in the latter case, erosion progressed only locally.

2 Ni powder (-#
100) and Fe powder (-#100) were mixed in a ball mill, and NbC powder (average particle size 20 μm) corresponding to 5% of the total weight was further added and mixed.
Next, add this mixed powder to a powder with internal dimensions of φ160mm x 12
The mixture was placed in a stainless steel container with a diameter of 150 m and a thickness of 6 mm. After vacuum degassing and sealing, the target was sintered at 1250° C. under a hydrostatic pressure of 1000 atm to produce a disc-shaped target with an outer diameter of 150 m and a thickness of 6 mm. This target had a matrix of 81% Ni-19% Fe, and was formed by a composite structure in which non-magnetic NbC was dispersed. Magnetron sputtering was performed under the same conditions as described above to examine the target usage efficiency. When the non-magnetic phase is dispersed, the usage efficiency is approximately
It was 30%, and in the case of only Ni and Fe, it was about 7%. Erosion was also observed over a wide range when the nonmagnetic phase was dispersed.

3 Ti equivalent to 4% of the weight of the molten metal was added to the molten metal adjusted to 84% Fe, 10% Si, and 6% Al, and after thorough stirring, the molten metal was poured into a water-cooled copper mold to obtain an ingot. This ingot has an outer diameter of 150 mm and a thickness of 8 mm.
A disc-shaped target was prepared by grinding. At this time, the target is Fe-Si-Al-Ti
It had a composite structure of a ferromagnetic region consisting of Ti and a non-magnetic phase mainly composed of Ti. Magnetron sputtering was performed under the same conditions as described above to examine target usage efficiency and erosion. Comparing the case where the non-magnetic phase was dispersed and the case where it was not dispersed, the usage efficiency in the former was about 20%, while in the latter it was about 6%. In addition, erosion was widespread in the former case and localized in the latter case.

From the above, by dispersing a non-magnetic phase in a ferromagnetic target, the target usage efficiency can be increased by 3.
It can be seen that the improvement is more than double.

The magnetic properties of the thin films formed in each example were investigated, and no differences were observed between those using a target with a non-magnetic phase dispersed therein and those using a conventional target. I couldn't help it.

<Effects of the Invention> As described above, according to the present invention, a sputtering target with excellent usage efficiency can be realized.

[Brief explanation of the drawing]

FIG. 1 is a principle diagram showing the magnetic field distribution when a sputtering target according to an embodiment of the present invention is used, and FIG. 2 is a principle diagram showing the magnetic field distribution when a conventional ferromagnetic sputtering target is used. It is a diagram. 1...Magnet, 2,2'...Target, 4...
Non-magnetic phase.

Claims (1)

[Claims] 1. A ferromagnetic sputtering target whose main constituent element is at least one of Fe, Co, and Ni, characterized in that a nonmagnetic phase is present in a dispersed manner.