JPH07109568A - Target for sputtering device - Google Patents

Abstract

PURPOSE:To improve the quality of a formed film by reducing the liberation of an adsorbed gas from the target of a sputtering device and to mitigate the contamination of a sputtering chamber. CONSTITUTION:A target 1 is welded to a backing plate 2 without using solder as follows. Namely, the target 1 having a truncated conical part on its periphery is pressure-welded on the periphery with a presser ring 3 having a hole of the same shape as the external shape of the truncated conical part of the target 1, the center is screwed in, and the target 1 is inserted and held between the backing plate 2 and the presser ring 3 and fixed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a structure for joining a target material used in a magnetron sputtering apparatus to a back plate.

[0002]

2. Description of the Related Art A target material used in a sputtering apparatus is continuously hit by ion particles during a sputtering operation, and as a result, a large temperature rise occurs if it is left as it is, which causes various problems due to heat (for example, deformation of the target material). , Melting, cracking, etc.). Therefore, as a countermeasure against this, a method of exhausting heat from the back side of the target material with cooling water is often used, but at this time, since the cooling water is pressurized, in order to prevent the target from being deformed by water pressure, It is common to use a back plate to reinforce the target material. In this case, it is necessary that the back plate be made of a material having a high heat transfer coefficient and be in contact with the target without any void. And conventionally, when joining a back plate with a metal target material that requires relatively large input power,
It is common to use a tin-based low-temperature solder material.

A specific example of the prior art will be described with reference to FIG. A target 1 integrated with a back plate 2 is screwed to an electrode body 4 containing a magnetic field generating mechanism and a cooling water mechanism. In this case, the target material 1 and the back plate 2 are joined by the solder material 16 with a joining strength of about 2 kgf / mm 2. Therefore, a large amount of heat generated when a high-density sputtering power is applied to the target flows out to the cooling water side with high heat transfer efficiency, so the target temperature does not reach a very high temperature and maintains a steady state. Solder material 1
With 6 parts, peeling due to heat or thermal stress during sputtering does not occur, and normal sputtering can be continuously continued.

On the other hand, as a conventional example in which a solder material is not used, there is an example as shown in FIG. In this case, target material 1
Is sandwiched between the target material 1 and the back plate 2 by a pressing ring 3 fixed to the back plate 2 with screws, and as a result, the target material 1 and the back plate 2 are pressure-bonded to each other. It has become possible to suppress the abnormal rise in temperature and continue sputtering continuously.

[0005]

However, when the solder material 16 is used as in the first conventional example, impurities and adsorbed gas contained in the solder material 16 are released into the sputtering processing chamber and the atmosphere inside the processing chamber is increased. However, there is an unavoidable drawback that it contaminates and adversely affects the film formation. These adverse effects due to the use of the solder material did not become a problem as long as the degree of integration of the LSI element was low, but with the increase in the degree of integration, it has been urged to solve them as a fatal drawback. That is, contamination of the processing chamber due to impurities or adsorbed gas released from the solder material during sputtering may seriously affect the wiring life and reliability of the integrated circuit together with the processing chamber contamination from other components of the processing chamber. I understand (Semiconductor W
orld1991.12 p195).

Therefore, in order to prevent contamination of sources other than the solder material in the sputter chamber, in order to reduce residual gas as much as possible, evacuation from the atmospheric state is performed to reach an ultimate vacuum of 10-7 Pa, or to the sputter chamber. We have taken countermeasures such as electrolytic polishing of the inner wall surface. However, it is not enough effect by itself, and the conventional structure without solder material (Fig. 6) was considered, but in this case, the target material 1 was deformed and normal sputtering was maintained. Occurrence of trouble that cannot be done was inevitable.

This phenomenon was calculated by the inventor using the finite element method, and a large tensile stress was generated in the vicinity of the outer periphery of the target material due to water pressure and the thermal load of sputtering.
As a result, it has been clarified that a gap is generated between the back plate and the target material.

According to the present invention, no solder material is used in the joint structure of the target and the back plate, and the adhesion is enhanced, so that the heat generated by the sputtering of the target material is efficiently discharged to the back plate cooling water. The present invention provides a target structure for a sputtering apparatus, which can be heated to continuously perform normal sputtering.

[0009]

In order to achieve the above-mentioned object, the present invention provides a substantially disc-shaped target material having a frustoconical portion on the outer peripheral portion, and a large diameter male or female screw near the outer peripheral portion. Has a back plate having a portion and a beveled hole portion having substantially the same inclination angle and diameter as the frusto-conical portion of the target material, and the frusto-conical portion of the target material abuts at the frusto-conical hole portion. And a pressing ring for fixing the target material.The pressing ring has a large-diameter female screw or a male screw provided on the outer peripheral portion thereof in cooperation with the large-diameter male screw or the female screw of the back plate. The target material for a sputtering apparatus has a structure in which the target material is sandwiched between the back plate and the back plate and tightened, and the center part of the target and the center part of the back plate are joined and fixed using screws.

[0010]

In the present invention, a target material having a frusto-conical shape is fixed to the outer peripheral portion of the target material with a screw on the back plate at the central portion, and a hole having the same inclination angle as the target is attached from above. While connecting to the hole of the holding ring, the target has a large diameter screw part, and the target is sandwiched and fixed by being bitten by the screw provided on the back plate. It is possible to apply compressive stress in the direction that cancels the maximum tensile stress part of. At this time, since the screw of the meshing screw portion has a large diameter, the cross-sectional area to which a force is applied is large, so that a large load can be applied. In the center of the target,
Using the screw member, the back plate and the target material are closely fixed,
Deformation due to water pressure and the resulting gap between the target and the back plate are suppressed. The surface of the contact surface between the target material and the back plate is fine and flat so that heat can be exchanged well. With these configurations, the heat generated by the ion collision during the sputtering operation can be efficiently transferred to the cooling water flowing on the back surface of the back plate, and the deformation due to the thermal expansion of the target material can be suppressed. .

[0011]

Embodiments of the present invention will be described below with reference to the accompanying drawings.

FIG. 1 is an embodiment of the present invention and is a cross-sectional view of a main part of a sputtering apparatus according to the present invention. In the figure, a metallic (for example, aluminum alloy) target material 1 has a female screw threaded in the central portion thereof, and in cooperation with a male screw threaded in the central portion of the back plate 2 made of copper, a surface finish is obtained. The state is fine and flat, and it is sufficiently tightened until the large-area contact surfaces are completely in contact with each other. The small hole formed in the center of the target 1 is for preventing air from accumulating in the screw portion during tightening. The pressing ring 3 made of stainless steel and having an outer shape of a thick disc has a hole extending along the central axis thereof, and the upper half portion of the hole has an inclination angle substantially equal to that of the frustoconical portion of the target material 1. And the diameter of the beveled hole, and a large diameter female screw is cut in the lower half. Then, the large-diameter screw part of the pressing ring 3 is engaged with the large-diameter screw part of the outer peripheral portion of the back plate 2, and further,
Completely tighten using the four holes (not shown) on the upper side of the pressing ring 3, and press the pressing ring while making contact with the frustoconical portion of the target material 1 at the frusto-conical hole portion of the pressing ring 3. The target material 1 is sandwiched and fixed between 3 and the back plate 2. And this target assembly,
Further, it is fixed to the electrode body 4 using a back plate fixing screw 6. An O-ring 5 for preventing leakage of cooling water from a tightening portion with the back plate 2 is incorporated in the upper end portion of the electrode body 4, and a magnet 7 is attached to the yoke 8 to attach the electrode body 4 to the electrode body 4. Built into. Further, inside the electrode in which the magnet 7 is incorporated, a water passage is provided in which cooling water flows from the cooling water inlet side 9 to flow inside the electrode and flows out to the cooling water outlet side 11.

After evacuating the sputtering chamber of the sputtering apparatus having the target assembly unit having the above-described structure, Ar gas is introduced into the sputtering chamber to maintain a pressure of 10 -1 Pa and a negative DC voltage is applied to the cathode electrode. By applying, the magnetron sputtering phenomenon occurs. At this time, the surface of the target 1 generates heat due to ion bombardment and rises in temperature, but this heat moves to the target material 1, the back plate 2, and the cooling water and is discharged.

According to the result of the finite element method, the stress applied to the frusto-conical portion on the outer circumference of the target 1 has an outer shape of 2
It is known that the maximum load of 1.25 kg / mm ² is applied to the position of 246φ when the temperature of the 54φmm aluminum target is 90 ° C. Therefore, in the present invention, the vicinity of the maximum stress generating portion is mainly suppressed by the frustoconical hole portion of the pressing ring 3 having the same inclination as the target material. As a result, for example, in the case of an aluminum alloy target material, the target life determined by the erosion depth can be used without damage even with an applied power of 8 kW.

Although the case of using an aluminum material as the target material has been described above, the present invention is not limited to aluminum, and the same effect can be obtained with a metal target such as titanium, copper or tungsten. Occurs. Also, shield 1
2 is provided in order to prevent the pressing ring 3 from being scraped due to a sputtering phenomenon and to prevent electric discharge during this period. In addition, the screw portion at the center of the target described first is effective in preventing the center from being deformed due to the water pressure of the cooling water flowing on the cooling surface of the back plate.

A second embodiment of the present invention will be described with reference to FIG. The target material 1 has a substantially frusto-conical shape, and a central portion of the bottom surface thereof has a male screw protruding toward the back plate 2 side.
The back plate 2 is in the shape of a round dish with the edges raised, with a female screw portion at the center of the inner bottom surface, and the inner surface of the rising edge,
A large-diameter female screw is provided, and the female screw of the back plate 2 and the male screw of the target material 1 are engaged with each other to form the target material 1
And the back plate 2 are in close contact with each other at the center. The outer shape of the stainless steel holding ring 3 is a substantially thick disk shape, and a large-diameter hole penetrates along the central axis thereof.
A frusto-conical portion of the target material 1 forms a frusto-conical portion having substantially the same inclination angle. A large-diameter female screw is cut on the outer peripheral portion of the ring 3. By engaging the large-diameter male screw portion of the pressing ring 3 with the large-diameter female screw portion of the back plate 2 and screwing them in, the frustoconical portion of the target 3 is suppressed by the steep hole portion of the pressing ring 3, 1, the back plate 2 and the pressing ring 3 are integrally assembled. still,
A cover 13 is attached to the upper part of the back plate 3. The cover 13 is for preventing abnormal discharge from the shield 12 by hiding a screw for fixing the back plate 2 which is the target assembly by incorporating the target material 1 to the electrode body 4 with the target material 1. Other basic operations are the same as in the first embodiment.

A third embodiment will be described with reference to FIG.
There is a concave step portion on the back plate surface side in the center portion of the target material 1, and a hole for screwing is formed in the center thereof. And the side is shaped like a cylinder on top of a frusto-conical shape. The back plate 2 is integrally formed with the electrode body 4 by processing or welding. The pressing ring 3 has a disk-shaped outer shape, and a large hole is provided along the central axis thereof, and the shape of the hole is made to match the outer circumference of the target 1. Back plate 2 with screws 14 at the center of the target
It is fastened to. Other basic configurations are similar to those of the first embodiment. By doing so, in addition to the effects of the other embodiments, there is another effect that there is no danger of cooling water entering the sputter chamber when the target material is replaced.

Example 4 is shown in FIG. As a substitute for the air vent holes formed in the target material 1 in FIG. 1, a groove 15 is dug in the back plate 2. This is a substitute for the air vent hole of Example 1, and this is effective for an electrode in which the target surface is flat and the central portion is sputtered.

[0019]

As described above, according to the present invention, it is possible to firmly and closely fix the target material to the back plate without using the solder material. Therefore, the target to the back plate can be fixed. As a metal target material fixing mechanism for a high-vacuum sputtering device that can obtain good heat transfer and dislike impurities,
The industrial effect is very large.

[Brief description of drawings]

FIG. 1 is a sectional view showing a first embodiment showing a target assembly of the present invention.

FIG. 2 is a sectional view showing a second embodiment showing the target assembly of the present invention.

FIG. 3 is a sectional view showing a third embodiment of the target assembly of the present invention.

FIG. 4 shows a main part of a target assembly part of the present invention.

FIG. 5 is a sectional view showing a conventional target assembly.

FIG. 6 is a cross-sectional view showing a conventional target assembly.

[Explanation of symbols]

 1: Target material 2: Back plate 3: Pressing ring 4: Electrode body 6: Set screw 7: Magnet 8: Yoke 9: Cooling water inlet 10: Cooling water outlet 11: Cooling water flow direction 12: Shield 13: Cover 14 : Set screw 15: Back plate air vent groove 16: Solder material

Claims (1)

[Claims] 1. A substantially disk-shaped target material having a frusto-conical portion on the outer periphery, a back plate having a large diameter male or female screw portion near the outer periphery, and a frusto-conical portion of the target material. It has a capped hole part having substantially the same inclination angle and diameter, and in the said capped circular hole part, it is brought into contact with the frusto-conical part of the target material, and consists of a pressing ring for fixing the target material, Pressing ring, with a large diameter female screw or male screw provided in the vicinity of the outer peripheral portion, in cooperation with the large diameter male screw or female screw of the back plate, to sandwich the target material between the back plate,
Moreover, a target for a sputtering device in which the central portion of the target material and the central portion of the back plate are joined and fixed with screws.