JPS5835261B2 - Electrodes for sputtering targets - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an improvement in electrode 0 for disposing a sputtering target on an end face facing a sputtering substrate and applying a DC electric field between the substrate and the target to perform sputtering. It is.

Generally, G consists of a combination of rare earth metals and iron group metals.
Amorphous magnetic thin films such as dCo and GdFe have magnetic anisotropy in the direction perpendicular to the film surface, so they have attracted attention as high-density thermomagnetic recording materials and magnetic valve materials, and various studies have been conducted on them. ing.

When such an amorphous magnetic thin film is put to practical use as the above-mentioned material, it is necessary to form a homogeneous, large-area magnetic thin film.

Various thin film forming techniques such as sputtering and vapor deposition have been applied to produce such amorphous magnetic thin films, and although it is difficult to determine their superiority or inferiority, at least GdCo, which has perpendicular magnetic anisotropy, Practical amorphous thin films cannot be produced without sputtering, and this sputtering method can also be widely used to form thin films made of other magnetic materials. According to the method, it is possible to easily produce a homogeneous thin film having a much larger area than other thin film forming techniques, and therefore, the sputtering method has many advantages as a thin film forming technique. There is.

Therefore, first, to briefly explain the sputtering method with reference to Figure 1, when a vacuum container is filled with an inert gas such as argon and a DC high voltage is applied between opposing electrodes, the strong DC electric field creates a is ionized,
Particles of argon ions having a positive charge collide with the target 1 at a negative potential to release constituent materials of the target 1, and the released particles of the target material scatter and adhere to the substrate 2 at a positive potential. , a thin film of target material is formed on the substrate 2.

Targets used in such sputtering methods are conventionally used in the arc melt method, that is, an alloy target produced by heating and melting a mixed powder of the composition materials by arc discharge, and the hot press method, that is, the alloy target produced by heating and melting the mixed powder of the composition materials. A hot press target made by sintering mixed powder under pressure and heat, or a target made by depositing a rare earth metal on an iron group metal disk, which is used to make the aforementioned amorphous magnetic thin film, etc. Although it is difficult to determine the superiority or inferiority of these targets, in general, alloy targets are often used.

Therefore, although the main purpose of the present invention is to improve the sputtering method using an alloy target, the present invention can be widely applied to sputtering methods using other targets as will be described later.

To explain in more detail the case where an amorphous magnetic thin film having perpendicular magnetic anisotropy as mentioned at the beginning is manufactured by sputtering using GdCo as a constituent material, the thin film formed by sputtering generally has a film surface The composition ratio of the constituent materials changes along the curve, and in the example of a GdCo thin film, the composition ratio of Gd becomes larger at the center.

Such non-uniform distribution of the material composition ratio in the sputtered thin film can be easily explained as occurring as follows.

That is, although the composition ratio of the constituent materials flying from the target 1 and depositing on the substrate 2 is approximately equal to the composition ratio in the target 1, the absolute amount of the constituent materials depositing on the substrate 2 is It decreases in the periphery compared to .

On the other hand, the constituent materials once deposited on the substrate 2 are bombarded by argon ion particles and are ejected from the sputtered coating on the substrate 2 and respackled, but since the argon gas evenly surrounds the sputtered coating, The absolute amount of the constituent material released by re-sputtering is approximately equal between the center and the periphery, and the ratio of the amount released by re-sputtering to the amount deposited from the sputtered film consisting of a combination of Gd and Co is Gd is larger than Co.

Therefore, in a sputtered film formed to a required thickness, the composition ratio of Gd increases in the center.

In addition, for more details, R, J, Kobl 1ska
. R, Ruf J, Cuomo: Uni
form of amorphous bubble
e films, AIIP Conf, proc,
A24.

(1974) 570. It is described in.

If the above is expressed in a formula, it becomes as follows.

That is, the material set in the sputtered coating, G
In a sputtered film made of a combination of d and Co, the following is true.Therefore, FGd and FCo are smaller in the peripheral part of the sputtered film than in the center, and RGd and RCo are almost the same between the peripheral part and the central part. Since they are equal, the composition ratio of Gd in the peripheral area decreases relatively, and becomes as follows.

However, the non-uniform distribution of the composition ratio in the sputtering film described above can be prevented from occurring by arranging sputtering targets that have a much larger area than the required film area. If a sputtering target with a uniform area is used, it is possible to produce a sputtering film with a uniform distribution of constituent materials.

However, depending on the arc melt method, which is suitable for producing homogeneous alloy targets, there is a limit to the size of the target alloy that can be produced. The more you
In the process of manufacturing an alloy target, the target being manufactured breaks irregularly, and it is usually difficult to manufacture a homogeneous alloy target with a diameter of 10α or more. Therefore, using such an alloy target, the distribution of material composition ratio The sputtering coating that can be uniformly produced is limited to a small area of several centimeters in diameter.

Note that when sputtering is performed using an alloy target manufactured to have a large area even if it is cracked as described above, the constituent material of the electrode 3 is also sputtered through the cracked gap in the alloy target, as shown in Figure 2. 2 and mixed into the sputtering film as an impurity, it is impossible to produce a sputtering film with a desired uniform composition by using a cracked alloy target even if it has a large area.

The purpose of the present invention is to solve the above-mentioned conventional problems and eliminate their drawbacks, and to produce a desired large-area sputtered thin film with a uniform material composition distribution without requiring a large-area homogeneous alloy target. An object of the present invention is to provide an electrode for a sputtering target that is suitable for manufacturing.

That is, the electrode for sputtering target of the present invention is
The method is characterized in that a plurality of electrode blocks on which a sputtering target is arranged in a plane are arranged close to each other, and a shielding electrode is provided that almost fills the gap between the electrode blocks. Multiple blocks of targets, including cracked alloy targets, are lined up flat on the block, and the gaps between the blocks are closed with shield electrodes to prevent sputtering of the electrode constituent materials, resulting in an equivalently large area. This made it possible to use a homogeneous alloy target.

In the following, the invention will be described in detail by way of example embodiments with reference to the drawings.

As mentioned above, a plurality of blocks, for example seven blocks, of homogeneous alloy targets are manufactured by, for example, the arc melt method, and the targets of the plurality of blocks are arranged closely to each other to effectively use a large area homogeneous alloy target. Examples of the structure of the electrode for sputtering target of the present invention, which is capable of performing sputtering, are shown in FIGS. 3a, 3b, and 3c.

Therefore, Figure 3a is a top view with the target block placed, Figure 3S is a longitudinal sectional view taken along the broken line in Figure 3a, and Figure 3C is a diagram with the target block removed. FIG.

As is clear from these figures, the electrode in which the end face portion where the target is placed is divided into a plurality of blocks, that is, the plurality of blocks of targets 1 closely arranged on the cathode 3 in the configuration shown in the first figure, has a shape of each block. For example, positive E
Any shape such as a square or a regular square may be selected, but in order to form a large-area target with efficient close contact, it is preferable that the shape of each target block be a regular hexagon with approximately equal area.

On the other hand, the shape of each electrode block 3 is commonly adapted to a target block of any shape, and in order to simplify and facilitate the manufacture of the electrodes themselves, including the shield electrode 4 described later, the shape of the end face is changed. A circular shape is preferred.

Note that, as will be described later, the gaps between the electrode blocks 3 are closed with the shield electrodes 4, so the target blocks do not have to be placed in close contact with each other, and there is no problem even if there are some gaps. The shape of each target block need not be strictly, for example, a regular hexagon, and therefore each target block can be manufactured easily.

Alternatively, only the boundary portions between the target blocks may be appropriately melted and bonded to each other.

Although the above-mentioned cracks are likely to occur in such joints, as described above, there is no problem even if cracks occur.

However, as is clear from FIG. 3, in the electrode of the present invention, it is necessary that the end face of each electrode block 3 is smaller than the target block 1 disposed above each, and A potential approximately the same as that of the anode on which the substrate 2 is placed is applied to the shield electrode 4 that closes the gap.

Furthermore, the gap d between the target block 1 and the shield electrode 4 and the gap d2 between the cathode block 3 and the shield electrode 4 shown in FIG. D>L between the width D of the target block 1 and the diameter of each cathode block 3
If the relationship of +2d2 is maintained, the cathode block 3 is always hidden behind the target block 1 when viewed from the anode side, and the gap between each target block 1 is closed by the shield electrode 4, the electrode The constituent material is no longer sputtered off.

Such conditions need to be maintained at all times, regardless of the number, size, or shape of the electrode blocks.

In addition, if the end face shape of each electrode block is made circular,
It is suitable to maintain the above-mentioned conditions even when used by piecing together cracked alloy blocks having irregular shapes and dimensions.

The results of measuring the characteristics of an amorphous magnetic thin film when a sputtering film having an area almost the same as the total area of the target was formed on a substrate using the split electrode according to the present invention shown in FIG. As shown in fig.
FIG. 5 shows the measurement results for an amorphous magnetic thin film formed in substantially the same manner using a conventional integrated electrode and a small-area target integrally formed to the extent possible.

The measurement results shown in Figure 4 are obtained when seven GdCo alloy target blocks having a composition ratio of 73at and %Co, manufactured by the Amert method, are closely arranged on the divided electrodes shown in Figure 3 to form a target with a diameter of 70 mm. The hysteresis characteristic curve of the GdCo amorphous thin film obtained was measured every 2.5 mπ in the diametrical direction on the film surface.
A desired characteristic curve that is almost uniform over a relatively wide area of 100 m or more is obtained, indicating that the holding force is almost uniform.

In addition, in order to improve the uniformity of the material composition ratio between each block, the above-mentioned alloy target is produced by crushing and mixing the alloy produced by the arc melting method, and then producing a new alloy by the arc melting method again. Each target block was manufactured by repeating the process several times, and each of the obtained alloy target blocks was shaped using a cutter and then placed closely together as shown in FIG. 3a.

In addition, the negative electrode has the structure shown in Figure 3, c.
The distances d1 and d2 between the shield electrode 4 and the target block 1 and negative electrode block 3 are both 2 mm,
The potential of the anode and shield electrode 4 is O■, the potential of the cathode 3 is -1.5 kV, and the argon gas pressure is 5 x 10-2 To.
rr, sputtering was performed under the condition that the distance between target 1 and substrate 2 was about 40 mm.

On the other hand, the measurement results shown in FIG. The same measurements as above were carried out on an amorphous thin film, and as mentioned above, the composition ratio of Gd in the peripheral part of the magnetic thin film decreases due to resputtering by argon ions. Compared to the case, almost uniform desired characteristics are obtained only in the center of the range of about H. Comparing this measurement result with the measurement result shown in FIG. 4, it is clear that the effect of the present invention is is clearly recognized.

Now, another advantage of the sputtering method according to the present invention, which is performed by arranging an alloy target consisting of a set of a plurality of blocks on the divided cathode, is that by appropriately combining and closely arranging alloy target blocks having different material composition ratios, The material composition ratio of the resulting sputtered coating can be precisely controlled to significantly increase its uniformity.

That is, as mentioned above, when a GdCo thin film is manufactured by sputtering, for example, the central part of the obtained GdCo thin film generally has a large Gd composition ratio. If an alloy target having a Gd composition ratio with a distribution characteristic opposite to the distribution is constructed and the Gd composition ratio is increased in advance in the periphery of the entire surface of the target, an alloy target having a uniform distribution characteristic can be used. In some cases, an alloy target with an area several times the size of the desired sputtering film was required, whereas a sufficiently uniform sputtering film can be obtained using a much smaller alloy target with an area comparable to that of the desired sputtering film. Although it is possible to produce a sputtering film having a material composition ratio, for example, if the individual material composition ratio of each target block placed on the electrode of the present invention having the configuration shown in Figure 3 is changed to the above-mentioned inverse distribution characteristic. By adapting, it is possible to easily and reliably realize the above-described method for producing a homogeneous film.

Therefore, in a state where the material composition ratio of such a target block can be finely controlled, strict homogeneity is no longer required for each target block.
When using the electrode of the present invention, not only an alloy target produced by the arc melt method but also other types of targets that are easy to manufacture, such as a hot press target, can be arbitrarily used to form a desired homogeneous coating relatively easily. can be produced.

Furthermore, as described above, when the distribution of the material composition ratio between each target block arranged on the divided electrode according to the present invention is changed in the radial direction of the circular target, the divided electrode according to the present invention can be used as shown in the third figure. It is preferable to have a configuration in which the negative electrode is divided into concentric circles according to the concentric distribution characteristics of the material composition ratio of the target, without having to configure
Examples of such configurations are shown in FIGS. 6 and 7.

FIG. 6 shows that similarly concentric alloy target blocks are arranged on the electrode block group 3 according to the present invention in which the negative electrode is divided concentrically as described above, and the material composition ratio of each target block is determined, e.g. Gdxi Cot-xi
xi+1≧ so that GdX1 becomes larger in the peripheral area.
FIG. 3 is a vertical cross-sectional view showing an example of the configuration when xi.

In addition, FIG. 7 shows a target in the case where concentric hot press targets having different material composition ratios in the radial direction are arranged on the same concentric electrode of the present invention to perform sputtering, as shown in FIG. 6. It is a top view showing block arrangement.

As described above, when the negative electrode is divided into concentric electrode blocks according to the present invention, at least the outer annular target has a large radius and requires substantially the same manufacturing equipment as that for large-area targets. If the block is further divided into multiple blocks, it will be much easier to manufacture the target block, and each concentric electrode block can also be redivided into multiple blocks corresponding to the redivision of the annular target block. It becomes easy to manufacture and assemble the electrode blocks themselves, and in particular, it becomes much easier to construct and manufacture shield electrodes that seamlessly close the gaps between the electrode blocks and hold them at the same potential.

Further, according to the present invention, the negative electrode is divided into a plurality of blocks, and the voltage applied to each electrode block is appropriately varied for each individual cathode block, for example, by connecting each block through a resistive element, Therefore, if the sputtering current value for each block is made different and the sputtering current is increased by increasing the voltage applied to the electrode blocks in the peripheral area, for example, the material composition ratio of the GdCo alloy target itself will be the same as that in the central area. Even if they are the same, the absolute emitted amount in the peripheral area increases, so it is possible to obtain the same effect as the concentric distribution of the target material composition ratio described above, and this effect is shown in FIGS. 6 and 7. This is particularly noticeable in the electrode of the present invention having a concentrically divided structure shown in FIG.

In this mode of applying the negative electrode voltage, it goes without saying that each electrode block is assembled in an insulated manner, and that each target block is also spaced apart from each other.

In the above description, embodiments of the present invention have been described with respect to an example in which an amorphous magnetic thin film such as GdCo is produced by a sputtering method, but the present invention is not limited to this example, and generally applicable to large area The production of targets, especially
The present invention can be widely applied to the production of homogeneous sputtering films using materials for which it is difficult to produce homogeneous large-area targets, and the same effects as described above can be obtained.

[Brief explanation of the drawing]

Fig. 1 is a layout diagram showing an overview of the sputtering method, Fig. 2 is a cross-sectional view showing the sputtering mode when the target has cracks, and Figs. 3 a, b, and C are target arrangement on the electrode of the present invention. FIG. 4 is a top view, longitudinal cross-sectional view, and top view showing an example of the structure of the electrode of the present invention and a configuration example of the electrode of the present invention, FIG. 6 is a characteristic curve diagram sequentially showing characteristic examples of a sputtering film produced by a conventional method, FIG. 6 is a longitudinal cross-sectional view showing an example of target arrangement on the electrode of the present invention with another configuration, and FIG. 7 is a diagram showing the same target. FIG. 7 is a top view showing another example of arrangement. 1...Target, 2...Substrate, 3.
...Cathode, 4...Shield electrode.

Claims (1)

[Scope of Claims] 1. An electrode for a sputtering target, characterized in that a plurality of electrode blocks on which sputtering targets are disposed in a plane are arranged close to each other, and a shielding electrode is provided that substantially fills the gap between the electrode blocks. 2. The sputtering target electrode according to claim 1, wherein the plurality of electrode blocks are concentrically solid. 3. The sputtering target electrode according to claim 2, wherein the voltages applied to the plurality of electrode blocks are different. 4. The sputtering target electrode according to claim 1, wherein the plurality of sputtering target blocks arranged in a plane on the plurality of electrode blocks have different composition ratios.