JPH0663107B2 - Parallel plate type dry etching device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (1) Description of the Field of the Invention The present invention relates to an improvement in a parallel plate type dry etching apparatus for forming a fine pattern of an integrated circuit on a wafer.

(2) Description of Prior Art In manufacturing a large scale integrated circuit, it is necessary to form a fine pattern on a semiconductor wafer, and therefore a dry etching apparatus is used. Various types of dry etching apparatuses have been devised so far, but in the manufacture of large-scale integrated circuits, a parallel plate type dry etching apparatus capable of forming a fine pattern with high reproducibility is the mainstream. However, it is hard to say that this parallel plate type dry etching apparatus has a higher processing capacity than a conventional wet etching apparatus or a cylindrical plasma etching apparatus that processes a large number of wafers at once.
For this reason, it is an important issue to provide an etching apparatus capable of performing high-speed etching while maintaining excellent parallel plate type fine processing characteristics and having high processing capability. Further, with the recent increase in the diameter of wafers, it is inevitable that a parallel plate type single wafer processing type dry etching apparatus for processing each wafer with good controllability will be further generalized. In this single-wafer processing type apparatus, it is obvious that the high-speed etching technique is more important than that in the conventional patch type apparatus that collectively processes a plurality of wafers in order to increase the processing capacity.

As described above, the technique of etching at a high speed will become more important in the future, but the use of the electric field concentration ring is one of the effective methods for increasing the etching rate. This is to increase the etching rate by concentrating the generated plasma on the upper portion of the wafer, as described below.

FIG. 1 is a sectional view of an example of a parallel plate type dry etching apparatus using a conventional electric field concentration ring. As shown in the drawing, a high frequency applying electrode 2 and a wafer mounting electrode on which a wafer 3 is mounted are installed in parallel in the processing chamber 1 so as to face each other. After the processing chamber 1 is evacuated by the vacuum exhaust system 5, a reaction gas of a predetermined flow rate is introduced from the reaction gas supply system 6 and the inside of the processing chamber 1 is maintained at a predetermined constant pressure by adjusting the exhaust capacity of the vacuum exhaust system 5. To do. When high-frequency power is applied from the high-frequency power source 7 to the high-frequency applying electrode 2 in such a state, the reactive gas is turned into plasma and the etching process is performed.

At this time, if the electric field concentrating ring 8-a is installed on the outer circumference of the wafer, the etching rate is increased by the following action. The electric field concentration ring is made of an insulator, a semiconductor, an insulator, or a conductor covered with a semiconductor. For this reason, the electric field in the portion where the electric field concentration ring 8-a on the wafer mounting electrode 4 is placed is shielded and weakened, and at the same time concentrated on the wafer mounting portion. Therefore, the plasma on the upper part of the wafer 3 becomes locally high in density, and as a result, the etching rate can be increased.

In FIG. 1, the use of the electric field concentrating ring has been described by taking as an example an anode-coupled parallel plate type dry etching apparatus in which the wafer mounting electrode 4-a is at ground potential. The action of the electric field concentrating ring is the same in a cathode coupling type device in which the electrodes are at the ground potential.

However, the conventional electric field concentration ring has not solved the following problems. That is, in the conventional ordinary electric field concentrating ring, as shown in FIG. It was a simple thing to put a wafer inside the hole. Although the etching rate will increase even with such a simple electric field concentration ring, the etching rate at the outer peripheral portion of the wafer is usually different from that at the central portion of the wafer because the electric field changes sharply at the boundary between the wafer and the electric field concentration ring. It was This means that the uniformity of etching in the wafer is deteriorated, and as a result, in the conventional parallel plate type dry etching apparatus using the electric field concentration ring, defects of semiconductor elements often occur in the outer peripheral portion of the wafer. There was a flaw.

(3) Object of the Invention It is an object of the present invention to provide a parallel plate type dry etching apparatus which eliminates the above drawbacks and precisely controls the concentration of an electric field to maintain a high etching rate and good etching uniformity in a wafer. It is intended.

(4) Features of the Invention In order to achieve the above object, in the parallel plate type dry etching apparatus of the present invention, an annular outer peripheral edge portion around the central portion on which a wafer is placed is inclined in the radial direction. A plasma is generated between the first electrode having a main surface that faces the second electrode, the second electrode facing the main surface of the first electrode, and the first electrode and the second electrode. A high-frequency power source for applying a high-frequency power for causing the first electrode to be annularly provided on the annular outer peripheral edge portion of the main surface of the first electrode, and the thickness in the direction perpendicular to the wafer mounting surface is the radial direction. The electric field concentrating ring gradually changes along the inclination of the first electrode.

(5) Example Hereinafter, an example of the present invention will be described with reference to the drawings.

2 (a), (b) and (c) are views for explaining one embodiment of the present invention, and FIG. 2 (a) is a structure of a conventional wafer mounting electrode and electric field concentration ring. 2B and 2C are partially enlarged views showing the structure of the wafer mounting electrode and the electric field concentration ring according to the present invention. The wafer mounting electrode and the electric field concentrating ring according to the present invention can be replaced with the conventional wafer mounting electrode and the electric field concentrating ring, for example, in the parallel plate type dry etching apparatus shown in FIG. In that case, the configuration and operation of the other units are the same as those described in the section of the description of the related art.

As shown in FIG. 2A, in the conventional case, the upper surface of the wafer mounting electrode 4-a is a flat surface and the electric field concentration ring 8 is formed.
-A had a uniform thickness. On the other hand, in the present invention, as shown in FIGS. 2B and 2C, the upper surfaces of the wafer mounting electrodes 4-b and 4-c are not flat surfaces and the wafer 3
The ring-shaped outer peripheral edge portion is inclined in the radial direction with respect to the center portion on which the electric field concentration ring 8-b,
8-c has a thickness that gradually changes in the radial direction of the ring.

In the configuration example of FIG. 2B, the wafer mounting electrode 4-b
Of the electric field concentrating ring 8-b has an upper surface (a surface facing the high frequency applying electrode 2 in FIG. 1) of the electric field concentrating ring 8-b. It is substantially parallel to the central portion (wafer mounting portion) of the wafer mounting electrode 4-b, and the lower surface thereof gradually increases toward the outer side in the radial direction following the annular outer peripheral edge portion of the wafer mounting electrode 4-b. Is inclined to become. As a result, the electric field concentration ring 8-b has a thickness that gradually decreases toward the outer side in the radial direction.

In the configuration example of FIG. 2C, the wafer mounting electrode 4-c
Of the electric field concentrating ring 8-c, the upper surface of the electric field concentrating ring 8-c is located at the center of the wafer mounting electrode 4-c (wafer mounting). Section), and the lower surface thereof is inclined so as to gradually lower toward the outer side in the radial direction following the annular outer peripheral edge of the wafer mounting electrode 4-c. As a result, the electric field concentration ring 8-c has a thickness that gradually increases toward the outer side in the radial direction.

FIG. 3 shows the etching rate in the wafer when the silicon oxide film (SiO ₂ film) formed on the 5-inch silicon wafer is etched by the parallel plate type dry etching device using the electric field concentration ring shown in FIG. It shows the distribution of.

Hereinafter, a specific example in which the etching distribution in the wafer is improved by the electric field concentration ring according to the present invention will be described with reference to FIGS. 2 and 3.

In FIG. 3, the solid line 9 indicates the case where no electric field concentrating ring is used, that is, the electric field concentrating ring 8− in FIG.
It is an example of the distribution in the wafer of the etching rate used by the apparatus which removed a. The broken lines 10-1 and 11-1 are examples of the results of etching using a conventional electric field concentrating ring having a uniform thickness. The etching rate increases as a whole, but the etching of the periphery of the wafer is uniform. Sex worsens. The etching rate at the peripheral area of the wafer is lower than that at the central area of the wafer but is higher than that at the central area of the wafer depending on the processing conditions such as high-frequency power, distance between electrodes, composition of reaction gas, pressure and flow rate. It is extremely difficult to obtain a uniform etching rate over the entire surface of the wafer while optimizing processing accuracy or damage to the wafer. When a distribution like the broken line 10-1 is obtained by the conventional electric field concentration ring 8-a,
By using the electric field concentration ring 8-b according to the present invention, the thickness of which decreases toward the outside in the radial direction, the electric field concentration around the wafer is preferably controlled, and the distribution of the etching rate within the wafer is improved as shown by the solid line 10-2. To be done. Also,
When the etching rate at the outer peripheral portion of the wafer is higher than that at the central portion as indicated by the broken line 11-1 by the conventional electric field concentrating ring 8-a, the thickness is increased toward the outer side in the radial direction as shown in FIG. When the electric field concentrating ring is used, the etching distribution in the wafer is improved as shown by the solid line 11-2.

As described above, according to the present invention, it is possible to obtain a good etching distribution in the wafer at the same time while increasing the etching rate which is the original function of the electric field concentration ring.

The operation of the present invention described with reference to FIGS. 2 and 3 above is merely an example, and the essence of the present invention is to change the radial thickness of the electric field concentrating ring so as to cancel the nonuniformity of etching. By doing so, the distribution of the etching rate in the wafer can be improved. Therefore, it is needless to say that the cathode coupling type is also effective in addition to the anodic coupling type illustrated in FIG.

(6) Description of Effects As described above, according to the present invention, it is possible to realize a parallel plate type dry etching apparatus capable of simultaneously achieving both a high etching rate and good etching uniformity in a wafer.

[Brief description of drawings]

FIG. 1 is a view showing a cross section of an example of a parallel plate type dry etching apparatus for explaining the action of the electric field concentration ring, and FIG.
Figure (a) is a partially enlarged view of Figure 1, and Figures 2 (b) to (c).
Are views showing embodiments of the present invention, and FIG. 3 is a view for explaining effects of the embodiments of the present invention. In the figure, 1 ... Processing chamber, 2 ... High frequency applied power, 3 ... Wafer, 4-a, 4-b, 4-c ... Wafer mounting electrode, 5 ... Vacuum exhaust system, 6 ... Reaction gas introduction system, 7
…… High frequency power source, 8-a, 8-b, 8-c …… Electric field concentration ring.

Claims (2)

[Claims] 1. A first electrode having a main surface in which an annular outer peripheral edge portion around the central portion on which a wafer is placed is inclined in the radial direction, and a main surface of the first electrode. Second electrodes arranged to face each other; a high-frequency power source for applying high-frequency power for generating plasma between the first electrode and the second electrode; and the main electrode of the first electrode. An electric field concentrating ring which is annularly provided on the annular outer peripheral edge of the surface, and whose thickness in the direction perpendicular to the wafer mounting surface gradually changes in the radial direction along the inclination of the first electrode. A parallel plate type dry etching apparatus characterized by: 2. A surface of the electric field concentration ring facing the second electrode is substantially parallel to a central portion of the main surface of the first electrode, and an annular shape of the main surface of the electric field concentration ring. The parallel plate type dry etching apparatus according to claim 1, wherein a surface on the side facing the outer peripheral edge portion is inclined in the radial direction following the annular outer peripheral edge portion.