JPS6313333A - Dry etching device - Google Patents

Abstract

PURPOSE:To limit a plasma region to a region almost equivalent to a wafer diameter for unifying etching process by a method wherein an electrode opposing to a wafer holding electrode is formed into double layer structure comprising a projecting conductor part and a recessed covering part. CONSTITUTION:An electrode 2 is formed into a double layer structure comprising a conductive member in the shape of projecting section covered with an insulating cover 4 in the shape of recessed section. On the other hand, another electrode 3 is in the shape of projecting section with only the part in contact with a wafer 6 projecting; an insulating cover 5 is mounted on the peripheral part of electrode 3; and the size of upper and lower electrode 2, 3 is equivalent to that of wafer 6. The recessed insulating cover 4 covering the projecting conductor part is equivalent to a condenser inserted into the upper and lower electrodes 2 and 3. Furthermore, the step difference of recessed part works so that the impedance Zc in the central part of electrode may be lower than the impedance Z0 in the peripheral part. Resultantly, any highfrequency current impressed between the upper and lower electrodes 2 and 3 flows concentratedly to the central part of electrode making a plasma region be limited to thier own region.

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to a dry etching device.

[Conventional technology]

In conventional parallel plate type plasma etching apparatuses, the gas flow of the reaction gas has been controlled in order to improve the uniformity of etching. For example, a large number of gas ejection holes are provided in electrodes facing the wafer holding electrode, and optimal gas flow is achieved by completely changing the positions and sizes of the ejection holes.

In addition, as a device for this sustenance, Fi was developed in 1892.
There are inventions disclosed in Publication No. 38, Japanese Utility Model Application Publication No. 60-118236, Japanese Patent Application Publication No. 60-46029, etc.

[Problem that the invention seeks to solve]

A cross-sectional view of a conventional dry etching apparatus is shown in FIG.

2.3 is a parallel plate electrode, and the wafer 7 is held at the center of the plate electrode 3. 1o is a dispersion plate made of quartz and has a large number of φ holes, and 6 is an electrode cover. Curve 2o in FIG. 5 shows the experimental value of the etching rate when aluminum was etched using the conventional etching apparatus shown in FIG. Note that the first curve 21 is a predicted value based on the calculation method. By optimizing the flow of the gas blown out from the dispersion plate 4, the etching becomes fairly uniform at the center of the wafer, but at the outer periphery of the wafer, as the etching rate increases, the etching uniformity deteriorates.

This poses a problem in increasing the yield υ in conventional devices.

The object of the present invention is to provide a dry etching apparatus that can completely improve the uniformity of the entire wafer by eliminating non-uniform etching on the outer periphery of the riH wafer, and can significantly improve the yield compared to conventional methods. .

[Means for solving problems]

In order to clarify the cause of the increase, we analyzed the gas flow inside the device and analyzed the concentration of radicals (reactants) to evaluate the etching rate distribution on the wafer surface. According to the calculation results, the etching rate is higher at the wafer's outer periphery because a large amount of diradicals are brought in by diffusion from the outer electrode plate toward the wafer center. It turns out that this is because the concentration of oxidants is high, and as a result, the reaction progresses there. This is thought to be because the plasma region is distributed over a space wider than the wafer diameter, and a large amount of radicals are generated in the outer region of the wafer. Therefore, in order to suppress the local increase in the etching rate on the wafer's outer periphery and improve uniformity, it is necessary to maintain the plasma area at about the diameter of the wafer! ,−,.

Therefore, in the present invention, in consideration of the above points, a double laminated structure electrode consisting of a convex conductor part and a concave insulating cover is adopted as the electric lug facing the wafer holding electrode, so that the plasma region is almost directly above the wafer. By making the area equal to the diameter of the wafer, the generation of radicals on the outside of the wafer diameter is suppressed, and the concentration of radicals on the outer periphery of the wafer is suppressed, thereby improving the uniformity of etching. be.

[Effect]

The concave insulating cover covering the entire convex conductor is equivalent to inserting a capacitor between the upper and lower electrodes. FIG. 2 is an electrical circuit diagram of the etching apparatus, and the step of the concave structure operates so that the impedance Zc at the center of the electrode is smaller than the impedance Zo at the periphery. Therefore, the high frequency current applied between the upper and lower electrodes 2 and 3 flows in a concentrated manner at the center of the electric sign, and the plasma region can be limited to that region.

Further, covering the conductor portion with an insulating cover prevents release of electrode metal due to sputtering, and can eliminate the influence of metal contamination on the wafer.

〔Example〕

An embodiment of the present invention will be specifically described below with reference to the drawings. FIG. 1 shows a sectional view of a dry etching apparatus according to the present invention. In the figure, 1 is a casing for maintaining the inside at low pressure, 2 and 3 are upper and lower electrodes, respectively, and 9 is a high frequency power source for generating plasma between the electrodes 2 and 3. On the other hand, the limestone gas is introduced through the gas supply lower and is turned into plasma between the electrodes.

While performing etching on the wafer surface, it flows through the apparatus and is exhausted through the exhaust port 8. Incidentally, the electrode 2 has an insulating cover 4 having a concave cross-section attached to a conductive member having a convex cross-section, thereby forming an electrode with a double laminated structure. On the other hand, the electrode 3 has a convex cross-sectional shape with only the portion that comes into contact with the electrode protruding, and an insulating cover ring 5 is placed around it. Note that the thickness of the convex portions of the upper and lower electrodes 2.3 is equal to that of the wafer 6. FIG. 3 shows the results of the etching rate distribution obtained using the double laminated structure electrode according to the present invention using the calculation method described above. Curve 31 is for the present invention; curve 30 is for the conventional device. By using a double-layer structure electrode as in the present invention, the plasma region can be kept limited to an area comparable to the diameter of the wafer, which suppresses the etching rate at the outer periphery of the wafer and improves the uniformity of etching throughout. It shows that it will improve.

Therefore, according to the present invention, in order to limit the plasma region to a desired region, the electrode facing the wafer holding electrode whose outer periphery is made of an insulator is replaced with a double electrode made of a convex conductor portion and a concave insulating cover. By adopting a laminated structure, it is possible to avoid local concentration of radicals at the outer periphery of the wafer as seen in conventional methods, and etching can be performed uniformly.

〔Effect of the invention〕

As explained above, according to the present invention, in a dry etching apparatus in which a reactive gas is sent between opposing electrodes and etching is performed by promoting a reaction using plasma,
This can be seen in the conventional method by making the electrode facing the wafer holding electrode a double laminated structure electrode consisting of a convex conductor portion and a concave insulating cover. This method suppresses the local increase in the etching rate at the outer periphery of the wafer, enables uniform etching, and greatly improves the yield (F) compared to the conventional method.

[Brief explanation of drawings]

Fig. 1 is a longitudinal sectional view showing an embodiment of the present invention, Fig. 2 is an electric circuit diagram of the device shown in Fig. 1, and Fig. 3 is a diagram showing the etching characteristics of the device shown in Fig. 1, and an experiment in the process. It is a line diagram showing values. 1...Casing, 2...Upper electrode, 3...Lower electric grinder. 4... Insulating cover, 5... Insulating cover ring, 6...
...Wafer, 7...Gas supply port, 8...Exhaust port, 9
・・・High frequency yζri ノ [j2]l 2nd concave 3 concave sea urchin high standing '84 Fig.

Claims (1)

[Claims] 1. In a dry etching apparatus that holds a wafer on one side of parallel plate electrodes provided in a vacuum container, and sends a reactive gas between the electrodes to etch the wafer surface through physical and chemical action, the wafer holding electrode and Dry etching characterized in that the opposing electrodes have a double laminated structure consisting of a convex conductor part and a concave cover part covering the conductor part, and the plasma region is limited to an area approximately equal to the wafer diameter. Device.