JPH04350163A - Magnetron sputtering target for ferromagnetic material - Google Patents

Abstract

PURPOSE:To decrease the volume of the unused part of a target by specifying the thickness of the target consisting of a ferromagnetic material. CONSTITUTION:A magnet is arranged on the back of a target. The density of plasma on the target surface is increased by using a magnetic field leaked from the magnet. Sputtering is carried out by the magnetron sputtering method. In this case, the thickness of the target consisting of a ferromagnetic material is controlled to <=2mm. Consequently, a ferromagnetic target for magnetron sputtering high in utilization efficiency is provided.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetron sputtering target for ferromagnetic materials.

0002

2. Description of the Related Art In the production of thin films, magnetron sputtering is one of the methods that has improved the drawback of slow thin film formation speed and has made sputtering practical. This magnetron sputtering method will be explained below. First, a pair of magnets is installed behind a cathode target placed to face an anode in a vacuum container, and a magnetic field perpendicular to the electric field for discharge is applied to the discharge space. Then, the magnetic flux generated from the magnet captures electrons flying in the discharge space near the surface of the target, increasing the electron density on the target surface. Therefore, the probability of collision between electrons and working gas molecules increases, and the plasma density increases, making it possible to knock out many atoms or molecules from the target surface. Although this magnetron sputtering method has increased the formation speed of sputtered thin films by more than an order of magnitude, the distribution of the magnetic field generated on the target surface is not uniform in this method. For this reason, if the ratio of the target volume before sputtering to the volume of the target that is actually consumed by sputtering is defined as the target utilization efficiency, in the case of a ferromagnetic target, only a part of the target erodes sharply, so The efficiency was very low.

[0003] As a method to solve the above problems, Ryuichi Takahashi, Masaaki Yoneda, Masahiko Naoe, "Development of toroidal plasma type magnetron sputtering method using a confining magnetic field" (Toyama University Faculty of Engineering Bulletin Vol. 40, 198)
9, pp. 13-20), methods such as drilling a hole in the center of a disk target are being considered in order to facilitate leakage of magnetic flux. However, a fundamental solution has not been reached because it is extremely difficult to form a uniform consumable part, especially when the target is a ferromagnetic material, or the equipment costs are extremely high. .

0004

2, 3, and 4 show conventional ferromagnetic targets and the magnetic flux leaking from the targets. Here, 3 is a target, 4 is a backing plate that supports the target, and 5 is a magnet for generating a magnetic field. Let A be the middle part between the poles of the magnet 5, where the magnetic field and the electric field are perpendicular to each other. First, explanation will be given with reference to FIG. A magnetic flux 10 generated from one of the magnets 5 passes through the backing plate 4 and is focused inside the target 3 because the target has a relatively high magnetic permeability of several tens or more. By the way, for this reason, in the initial stage of sputtering, most of the magnetic flux enters another magnetic pole without leaking to the outside, and only a part of the magnetic flux that has become oversaturated within the target leaks to the outside. Furthermore, the magnetic field at the target surface due to this leakage magnetic field becomes the strongest.

[0005] As a result, the plasma density in this part increases, and the target gradually erodes into a valley shape with A as the center.

On the other hand, when the thickness of a ferromagnetic target partially becomes thinner due to plasma erosion, the magnetic resistance of the target increases, so that leakage magnetic flux increases at that location. This is shown in FIG. As the leakage magnetic flux increases, the localization of the plasma progresses, and the erosion area in that area becomes smaller. As the erosion progresses further, the magnetic flux leaking also increases as shown in FIG. Eventually, the target will erode steeply, with a trailing tail centered on A, as shown in FIG. In this case, the target utilization efficiency is extremely low. Currently, targets made of ferromagnetic materials are widely used with a thickness of around 5 mm, but the utilization efficiency of targets with this plate thickness is approximately 7% to 9%, and the utilization efficiency of ferromagnetic targets is extremely low. It has become a thing.

An object of the present invention is to provide a ferromagnetic target for magnetron sputtering with high utilization efficiency.

[0008]

[Means for Solving the Problems] In order to achieve the above object, the present invention reduces the thickness of the ferromagnetic target to 2 mm or less, reduces the unused portion, and increases the utilization efficiency of the target.

[0009]

[Operation] Therefore, in order to improve utilization efficiency by reducing the volume of the unused portion of the target, we have considered reducing the curve that resembles the tail of the target consumption portion. In other words, it is good if the target is completely consumed before the erosion of the target becomes steep. Therefore, in the present invention, we considered reducing the thickness of the target. Figure 7 shows the relationship between target plate thickness and utilization efficiency. This clearly shows that reducing the thickness of the target improves the utilization efficiency. Therefore, in the present invention, the plate thickness of the target is set to 2 mm or less, thereby improving the utilization efficiency of the target.

[0010] If the life of the target is defined as the time it takes for a part of the target to wear out, then in this case it is conceivable that the target life will be shortened. However, the utilization efficiency of conventional targets is only about 7% to 9%, and it is known from the above that the target erodes into a valley shape with a steep curve. This indicates that the volume of the target that is actually eroded is very small at the bottom of the target. That is, the time the target is sputtered is longer at the top of the target and shorter at the bottom of the target. Therefore, even if the target thickness is reduced, the life of the target does not substantially change.

[0011]

[Embodiment] An embodiment of the present invention will be explained below with reference to FIG.

<Example 1> FIG. 1 shows a block diagram of a magnetron sputtering apparatus and a ferromagnetic target used in this example. Here, 1 is an anode, 3 is a cathode target, 4 is a backing plate for holding the target, 5 is a magnet for generating a magnetic field, and 7 is a vacuum container. The magnet used was SmCo, and the ferromagnetic material of the target was an Fe target with a thickness of 2 mm according to the present invention and an Fe target with a thickness of 5 mm that had been used in the past, and the state of wear of both targets was compared. did.

FIG. 5 is a sectional view showing the state of wear of an Fe target having a thickness of 5 mm. The horizontal axis represents the distance in the left and right radial directions when the center of the target is O, and the vertical axis represents the film thickness. The area near the surface of the target is eroded relatively uniformly, but as you move away from the surface, the erosion occurs in the central area between the magnets.
Erosion begins to concentrate on the part A, and eventually only the part A erodes steeply, as if it were a tail.

FIG. 6 shows the state of wear of an Fe target with a plate thickness of 2 mm. Similar to the 5 mm thick target, the area near the surface is eroded relatively uniformly. However, since the target according to the present invention has a thin film thickness, even the bottom part of the target has a sharp valley-like curve with a tail as seen in FIG.
bu is not often observed. Therefore, it can be seen that the ratio of the unused portion of the target consumption portion to the unused portion is increasing. Therefore, FIG. 7 shows the relationship between the plate thickness of the Fe target and the target utilization efficiency. As the plate thickness of the target decreases, the utilization efficiency increases, and by using a ferromagnetic target with a plate thickness of 2 mm, it was possible to obtain a utilization efficiency of about 25% or more. In addition, the life of the target was not significantly different from that of a target with a thickness of 5 mm.

<Example 2> Table 1 shows the utilization efficiency of a 2 mm thick target according to the present invention using various ferromagnetic materials.

[0016]

[Table 1]

From this, it can be seen that when the target according to the present invention is used, the target utilization efficiency is 25% or more, which is higher than the conventional value of about 7% to 9%.

[0018]

As described above, according to the present invention, since the thickness of the ferromagnetic target is set to 2 mm or less, the volume of the unused portion of the target can be reduced, and a high utilization efficiency of 25% or more can be achieved. You can get it.

[Brief explanation of drawings]

[Fig. 1] A configuration diagram of a magnetron sputtering apparatus showing an embodiment of the present invention.

[Figure 2] Principle of ferromagnetic target and its leakage magnetic flux Figure 1

[Figure 3] Principle diagram of ferromagnetic target and its leakage magnetic flux 2

[Figure 4] Principle diagram of ferromagnetic target and its leakage magnetic flux 3

[Figure 5] Cross-sectional view of a conventional target in a worn state

[Fig. 6] Cross-sectional view of the target in a worn state according to the present invention

[Figure 7] Relationship diagram between target plate thickness and utilization efficiency

[Explanation of symbols]

1...Anode, 2...Substrate, 3...Target, 4...backing plate, 5...Magnet, 6... York, 7...Vacuum container, 8...Power supply, 9...Vacuum pump, 10...Magnetic flux.

Claims (1)

[Claims] 1. In a magnetron sputtering method in which a magnet is placed on the back surface of a target and a magnetic field leaking from the magnet is used to improve the plasma density on the surface of the target to perform sputtering, the target is made of a ferromagnetic material. A magnetron sputtering target for ferromagnetic materials characterized by having a thickness of 2 mm or less.