JPS6135695B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an electrode device in an apparatus that performs plasma processing on a wafer, for example, an apparatus that performs plasma anodic oxidation processing to form an insulating film on a Ga or As wafer.

Conventionally, this type of apparatus is known in which a wafer is placed on the top surface of an electrode and subjected to plasma treatment, but in this case, as the plasma treatment progresses, the wafer gradually loses electrical resistance due to film formation. The effective current flowing through the wafer is increased and therefore the effective current flowing through the wafer gradually decreases, and thus the current flowing directly onto the top surface of the electrode tends to gradually increase, with the disadvantage that the progress of film formation is impaired. In order to eliminate such inconvenience, it is conceivable to cover the upper surface of the electrode with an insulating cover, leaving the place where the wafer is placed in the transparent window, but in such a case, there is some dimensional error in the wafer. does not fit well when present.

That is, when the wafer is relatively large, it does not fit into the transparent window and thus does not come into contact with the top surface of the electrode, and when the wafer is relatively small, a gap is created at the outer periphery within the transparent window, This tends to cause plasma concentration and other problems.

The object of the present invention is to obtain an apparatus free of such inconveniences, and in a type in which a wafer is placed on the upper surface of an electrode and subjected to plasma processing, the upper surface of the electrode is placed on the wafer. A convex portion protruding upward is formed at the mounting location, and the remaining portion is covered with an insulating cover made of quartz or other material.

An example of implementing the present invention will be explained with reference to the attached drawings.

In the drawings, reference numeral 1 indicates an aluminum electrode or other electrode, and a positive bias voltage is applied to the electrode 1 from an external power source. A wafer 2 is placed on the upper surface of the electrode 1 and subjected to plasma treatment, and the upper surface of the electrode 1 is formed into a convex portion 3 that protrudes upward at the location where the wafer 2 is placed, and the remaining portion is An insulating cover 4 made of quartz or other material is applied to the surface. In the illustrated embodiment, the protrusion 3 is made of a disk made of aluminum or other material, and is fitted and bonded into the concave casing 5 previously formed above. Furthermore, as shown in the figure, a plurality of convex portions 3 are arranged as necessary to provide for a plurality of wafers 2, and furthermore, the convex portions 3 have a slightly smaller area than the wafer 2 placed thereon. It is common to make it. In the illustrated embodiment, the wafer 2 has a substantially sector-shaped shape, and the convex portion 3 has a circular shape substantially inscribed therein. As mentioned above, the insulating cover 4 is made of quartz or other material and is applied by covering the remaining part of the insulating cover 4.
Its wall thickness is relatively reduced so that it does not exceed the protruding height of the convex part 3, in other words, the convex part 3 covers the cover 4.
Generally, it protrudes slightly upwards beyond the upper surface of the.

In the drawings, reference numeral 6 indicates a jacket for water cooling inside the electrode 1, and reference numeral 7 indicates a cylindrical shield on the outer periphery. Note that the convex portion 3 and the insulating cover 4 described above do not have to be prepared separately in advance, but can be formed integrally with the upper surface of the electrode 1 by vapor deposition, sputtering, or other film forming means.

To explain its operation, when the wafer 2 is placed on the convex part 3 and brought into contact with it, the plasma concentrates on the wafer 2 and forms an oxide insulating film thereon. The remaining part of the upper surface of the electrode 1 is covered with a cover 4 and is not affected by plasma, and furthermore, at this time, the wafer 2 is supported by the protrusion 3 and exposed above the cover 4. It is possible to provide good plasma processing over the entire surface of the wafer 2, and even if the wafer 2 has some dimensional error, it can be well adapted to this.

In other words, whether it is relatively large or relatively small,
It is placed directly on the convex portion 3 and makes good contact with it, and does not cause the disadvantages of the transparent window type described above.

In this way, according to the present invention, the plasma acts concentratedly on the wafer, the path through which the current flows is constant, and the current density can be maintained uniformly, thereby eliminating the above-mentioned disadvantages of the conventional method in which the current flows directly on the upper surface of the electrode. Moreover, the convex portion has the effect of holding the wafer in an exposed state above the cover to provide good processing to the wafer, and also being able to accommodate dimensional errors of the wafer.

[Brief explanation of the drawing]

Fig. 1 is a cutaway side view of one example of the device of the present invention;
The figure is a top view. 1... Electrode, 2... Wafer, 3... Convex part, 4...
...Insulating cover.

Claims (1)

[Claims] 1. In a type in which a wafer is placed on the top surface of an electrode and subjected to plasma treatment, the top surface of the electrode is formed into a convex portion that protrudes upward at the beginning of the placement of the wafer, and the remainder is covered with quartz. An electrode device in a plasma processing apparatus provided with another insulating cover.