JPS63244728A - Target for sputtering - Google Patents

Abstract

PURPOSE:To form a ferromagnetic thin film at high speed using a simple method by providing the distortion necessary for the surface and the entire internal part of a target, to be used for the sputtering, formed by a magnetic material. CONSTITUTION:A part of the magnetic flux generated by the N-pole of a magnet 10 passes through a packing plate 12 and a target 14, other magnetic flux passes through a target 4 and leaked to outside, and a magnetic field is formed dn the surface of the target. However, when the target 14 is made of a ferromagnetic material, the magnetic reluctance of the magnetic path in the target is decreased remarkably, and the magnetic flux is concentrated. As a result, the intensity of the magnetic field on the surface of the target is reduced. The reason of the decrease in magnetic field intensity is the high permeability of the ferromagnetic material. Accordingly, the permeability of the target is lowered by adding distortion to the target, and the magnetic reluctance is increased. Besides, it is desirable that said distribution is added to the target by the deformation in thickness of 0.5 % or more. As a result, the magnetic field of a magnetic field generating means can be concentrated on the surface of the target excellently, and the speed of film formation can be improved.

Description

[Detailed Description of the Invention] [Industrial Field of Application] This invention relates to a sputtering target, and particularly relates to a sputtering target suitable for forming a magnetic thin film using a magnetron type sputtering device. .

[Prior Art] In recent years, various magnetic thin films have been used in fields such as perpendicular magnetic recording thin films, magnetic disks, magnetic bubbles, and magnetic heads. As a method for forming such a magnetic thin film, a magnetron sputtering apparatus is often used from the viewpoint of composition controllability and film formation rate. This device achieves high-speed film formation by increasing plasma density using orthogonal electric and magnetic fields.

FIG. 3 schematically shows an example of such a magnetron sputtering apparatus. In this figure, a target 14 made of a necessary GTi material is placed on the NS magnetic pole of the permanent magnet 10 on the cathode side with a supporting or reinforcing backing plate 12 interposed therebetween.

At a suitable position above the target 14, a substrate 16 on which a magnetic thin film is formed is arranged as an anode side. The above apparatus is placed in a suitable vacuum chamber, and a necessary sputtering gas, such as argon, is introduced into the chamber.

In the above device, the lines of magnetic force caused by the magnet 10 are
As shown by the arrow F1 in the figure, the magnetic field exits from N tpi and enters the S pole, forming a parallel magnetic field on the surface of the target 14.

On the other hand, an electric field is formed between the target 14 and the substrate 16 in a direction perpendicular to the above magnetic field by an appropriate power supply means (not shown).

Argon ions 18 are generated when a discharge is generated between the target 14 and the substrate 16 as described above using an appropriate power source. It is concentrated near the surface, increasing the plasma density.

The magnetic particles 20 are knocked out from the target 14 by the argon ions 18, and a magnetic thin H@
22 will be formed.

Incidentally, in order to perform sputtering at high speed, it is necessary to form a considerable magnetic field on the surface of the target 14. However, especially when a ferromagnetic material is used as the target 14, the target 14 constitutes a magnetic circuit with low magnetic resistance, and the magnetic flux generated from the magnet 10 is shielded inside the target.

For this reason, a magnetic field that can trap high-density plasma well is not formed on the target surface, and as a result, the film formation rate decreases significantly, making it impossible to perform sputtering at high speed.

In order to solve this problem, first, the cross-sectional area of the target 14 is reduced by making it thinner.
There are ways to increase magnetic resistance. However, with this method,
As the target 14 becomes thinner, the life span of the target 14 is shortened, and it becomes necessary to frequently replace the target 14, which is not preferable for mass production.

For this reason, Japanese Patent Application Laid-Open No. 57-16013, Japanese Patent Application Laid-open No. 58
JP-A-177468 and Japanese Patent Laid-Open No. 59-211211 disclose a technique in which a groove or a gap is formed in a target to lower the apparent magnetic permeability and thereby enable high-speed film formation.

[Problems to be Solved by the Invention] However, in the above method, it takes time and effort to form grooves or gaps, and it is necessary to handle the target as an integral part of the backing plate. There are various disadvantages in that it is necessary to devise the shape of the groove or gap.

The present invention has been made in view of these points, and an object of the present invention is to provide a sputtering target that can be manufactured by a simple method and is suitable for high-speed deposition of ferromagnetic thin films.

[Means for Solving the Problems] The present invention is characterized in that necessary strain is applied to the entire surface and interior of a sputtering target formed of a magnetic material.

According to a main aspect of the invention, said quantity is applied to the target by a thickness deformation of 0.5% or more.

[Function] According to the present invention, by applying strain to the target, the magnetic permeability of the target decreases and the magnetic resistance increases.

For this reason, the magnetic flux of the magnetic field generating means is well concentrated on the target surface, and the film formation rate is improved.Examples Embodiments of the present invention will now be described in detail with reference to the accompanying drawings.

First, an overview of the present invention will be explained. FIG. 4 shows the magnetic flux at the target 14 portion. In this figure, part of the magnetic flux generated from the N pole of the magnet 10 passes through the backing plate 12 and the target 14, and the other flux passes through the target 14 and leaks to the outside, forming a magnetic field on the target surface. It will be done.

Among the magnetic paths of each of the magnetic fluxes described above, the magnetic resistance of the magnetic path within the backing plate 12 can be sufficiently increased by forming the backing plate 12 from a non-magnetic material.

Next, when the target 14 is made of a ferromagnetic material, the magnetic resistance of the magnetic path within the target is significantly reduced,
Magnetic flux is concentrated. Therefore, the strength of the magnetic field on the surface of the Yuichi target decreases.

As described above, the reason why it is difficult to form a magnetic field on the surface of a ferromagnetic target when a ferromagnetic target is used is that the ferromagnetic material has a high magnetic permeability. Therefore, if the magnetic permeability of the ferromagnetic target can be lowered, the original high-speed film formation performance of the magnetron sputtering apparatus can be obtained.

By the way, it is generally well known that when strain (processing) is applied to a magnetic material, its magnetic permeability decreases. The present invention is
Focusing on this phenomenon, the target is manufactured using a strained material.

Figure 1 shows an example of the relationship between the permeability of the target and the film formation rate when film formation is performed using a magnetron sputtering device using an Fe (iron) target manufactured by applying strain. .

In this figure, the horizontal axis is the amount of strain, and the vertical axis is the maximum relative magnetic permeability or film formation rate. Note that strain is applied to the material by rolling, forging, etc., and the amount of strain is expressed as a percentage of (original thickness of material - finished thickness)/original thickness.

As shown in Figure 1, the magnetic permeability is greatly reduced by the presence of a slight strain of 0.1%, and when further strain is added,
The magnetic permeability also decreases further. As the permeability rIfi rate decreases, the film formation rate increases significantly.

Next, FIG. 2 shows the relationship between target thickness and film formation rate with respect to the amount of strain applied to the material in the Fe target. The horizontal axis is the target thickness, and the vertical axis is the deposition rate. As shown in this figure, if sufficient strain is applied, it is possible to obtain a sufficient film formation rate even if the target thickness is increased.

These effects are not limited to Fe-3i, Fe-
Ni, Co-Cr, Co-Ni.

Fe-3i-ALL, Fe-Tb, Fe-Co.

Confirmed in ferromagnetic materials such as Gd-Tb, ferrite, and Nd-Fe-B.

However, the strain must remain as uniformly as possible over the entire target including the inside, and in order to increase the film formation rate, it is preferable to apply a strain of 0.5% or more.

Note that the strain introduced during the processing of the target is limited to the surface layer of the target, and is different from the strain described above. That is, the target is usually obtained by processing a plate material into a desired shape, but during such processing, a certain processing strain occurs on the target surface (for example, 1 to 2 μm), which is indicated by dashed lines in FIG.

Although such distortion also reduces the magnetic permeability of the target and enables high-speed film formation, this effect is a local phenomenon only on the target surface, and this effect cannot be obtained when the target surface is sputtered. I can't.

In contrast, in the present invention, since strain is applied to the entire target including the inside thereof, the effect of high-speed film formation can be continuously obtained.

Next, examples of sputtering targets according to the present invention will be described.

Pure iron, Tb3oFe, (1, C07ON 13o of 10
A plate with a thickness of 5 mm was obtained by rolling a plate with a thickness of 5 mm. That is,
A strain of 50% was applied. After stabilizing this at 400° C. for 1 hour, a target with a thickness of 2 mm was created.

On the other hand, after performing stabilization annealing without rolling, that is, without applying strain, a 2 mm thick target was created from a 10 mm thick plate for comparison.

Using these targets, 10 thin films with a thickness of 5 μm were formed using a magnetron sputtering device and then discarded, and then film growth was performed to measure the average film formation rate and erosion area.

In addition, in order to see how long the characteristics last, a total of 100
The film formation rate after sputtering for hours was measured.

The sputtering conditions are as follows.

Voltage (DC)・・・・・・・・・・・・・・・・・・
・・310■Current・・・・・・・・・・・・・・・・・・
・・・・・・・・・・・・700mA argon pressure・・
・・・・・・・・・・・・・・・・・・10mtor
r board/target distance current 70
Note that the film formation rate was calculated from the formed film thickness and the sputter link time.

The results are shown in the table below. Values are expressed as a ratio to the comparison target. As is clear from the results, according to this example, not only can a ferromagnetic thin film be formed at high speed, but also the yield of targets can be improved.

Note that the stabilization annealing of the target performed in the above embodiments is performed for the following reasons.

Generally, during sputtering, the temperature of the target increases, which causes a part of the strain to be lost and a change in sputtering characteristics to occur. In order to prevent such disadvantages, stabilization annealing is performed at a temperature below the recrystallization temperature of the material, for example.

Although the embodiments of the present invention have been described above, the present invention is not limited to the above embodiments; for example, the present invention can be applied to composite targets as well.

[Effects of the Invention] As explained above, the sputtering target according to the present invention has the advantage that it can be manufactured by a simple method and that a ferromagnetic thin film can be formed at high speed.

[Brief explanation of drawings]

Fig. 1 is a diagram showing the relationship between target strain, magnetic permeability, and film formation rate in an example of the present invention, and Fig. 2 is a diagram showing the relationship between target thickness and film formation rate with respect to strain in an example. , FIG. 3 is an explanatory diagram showing an example of magnetron sputtering, and FIG. 4 is an explanatory diagram showing the state of magnetic flux near the target. 10... Magnet, 12... Backing plate, 14
...Target, 16...Substrate, 22...Thin film.

Claims (2)

[Claims] (1) In a sputtering target made of a ferromagnetic material, which is used to form a film by magnetron sputtering using a magnetic field generated on the target surface by a magnetic field generating means, necessary for the entire surface and interior. A sputtering target characterized by adding a certain amount of distortion. (2) The sputtering target according to claim 1, wherein the strain is 0.5% or more.