JPH0393227A - Dry etching system - Google Patents

Abstract

PURPOSE:To improve uniformity of etching speed by curving ends of counter parallel plate electrodes. CONSTITUTION:A lower electrode and an upper electrode 10 each curved at electric ends are provided inside a vacuum container 1. Curving electrodes in this way uniformizes the distribution of electric fields between both the electrodes from the center to the outer periphery. As a result, the uniformity of etching speeds improves.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a dry etching apparatus with a parallel plate electrode configuration for dry etching semiconductor devices such as LSIs, and in particular, to a dry etching apparatus with a parallel plate electrode structure, which is capable of dry etching a semiconductor device such as an LSI. This relates to a dry etching device that can improve [Prior art] In recent years, dry etching technology using glow discharge plasma has been widely used as a microfabrication technology for LSI.
As LSIs become more highly integrated, the precision required for etching is becoming increasingly strict. In a device with a parallel plate electrode structure, etching characteristics such as etching speed and anisotropy depend on the high frequency electrode, power frequency, and electrode spacing.
It is known that it depends on many parameters such as gas pressure. In recent years, as the outer diameter of the sample to be etched (substrate) has become larger, the etching rate and its dependence on the substrate position, so-called uniformity of the etching rate, have become more important as etching performance. In a typical parallel plate electrode structure, the etching rate of the substrate differs between the periphery and the center of the substrate, and generally the periphery is etched faster. For this reason, for example, as shown in Japanese Unexamined Patent Publication No. 62-47132, there is a method in which the distance between the electrodes is varied between the center and the peripheral portion of the substrate, which is the material to be etched, in order to improve the uniformity of the etching rate. An example is shown in Figure 3.
In FIG. 3, l is the vacuum container of the device, 2 is the lower electrode on which the substrate is placed, 3 is the upper electrode, 4 is the substrate which is the material to be etched, 5 is the matching box (matching circuit), 6 is the high frequency power source, 7 is the reactant gas inlet, and 8 is the exhaust port. Next, we will explain the operation. Although the reaction mechanism of engineering is complex, it is thought to be a complex reaction of physical reactions caused by charged particles such as ions and scientific reactions caused by central species such as radicals. In RIE (reactive ion etching) mode, in which high-frequency power is applied to an electrode on which a substrate is placed, as shown in Figure 3, ions are accelerated by a DC electric field formed by a sheath near the substrate and are incident on the substrate. This increases the contribution of physical reactions, making anisotropic etching possible. Therefore, in RIE mode, etching is greatly affected by the electric field distribution between the electrodes. Conventionally, in etching using a parallel plate electrode structure, the etching rate at the center of the substrate is often slower than at the periphery. In the conventional device shown in FIG. 3, the portion of the upper electrode 3 facing the substrate is formed in a step-like manner convex downward from the center toward the periphery, as shown in the figure, and the electric field distribution between the electrodes is limited to the center. This is intended to make the etching rate of the substrate uniform by increasing the etching rate toward the periphery and decreasing it toward the periphery.

[Problem to be solved by the invention]

However, in the example of JP-A-62-47132, the distance between the electrodes changes discontinuously, so the electric field distribution also becomes discontinuous, and no improvement in the uniformity of the etching rate can be expected. For example, even if the electrode shape is not step-like, but the upper electrode is thinly curved from the center, there is not necessarily a proportional relationship between the electric field and the etching rate, and the electric field changes depending on the plasma state, so under certain conditions Even if the distance between the two electrodes is changed to make the etching rate uniform, if the conditions such as high frequency power, gas pressure, and gas type are changed, the etching rate will no longer be uniform. was there. This invention was made to solve the above-mentioned problems, and aims to provide a dry etching apparatus that can improve the uniformity of semiconductor etching rate within a substrate. [Means for Solving the Problems] A semiconductor processing apparatus according to the present invention has two opposing electrodes arranged in parallel, and a curvature at the end (outer periphery) of both electrodes or one side of the electrode. [Operation] In this invention, since the ends of the opposing parallel plate electrodes are curved, the electric field distribution between the two electrodes is uniform from the center to the outer periphery, and the experimental conditions such as high frequency power can be adjusted. The electric field distribution between the electrodes can be kept uniform even when the electrodes are changed, improving the uniformity of the etching rate. [Example] An example of the present invention will be described below with reference to the drawings. FIG. 1 is a diagram showing the structure of a dry etching apparatus according to an embodiment of the present invention. In the figure, 9 is a lower electrode with a curvature at the end of the electrode, and 10 is a lower electrode with a curvature at the end of the electrode. This is the upper electrode. Also, l in the figure indicates the distance between the electrodes. Figure 2 shows an enlarged example of the electrode end. R in the figure is the radius of curvature. The reaction mechanism of etching is thought to include physical reactions caused by charged particles such as ions, chemical reactions caused by neutral active species such as radicals, and their competing reactions. In recent years, as the demand for microfabrication precision has increased, so-called RIE (reactive ion etching), which applies high-frequency power to an electrode on which a processed substrate is placed and uses a DC electric field created by a sheath near the substrate, has become the mainstream etching method. Moreover, in order to further increase the anisotropy of etching, it has become more common to operate in a higher vacuum than before. In such cases, the physical effects of ions that are reactive with the substrate contribute more to etching, and the uniformity of the etching rate is greatly influenced by the electric field distribution between the electrodes. In general, RIE mode etching equipment uses upper and lower electrodes facing each other in parallel, and the ends of the electrodes have an acute angle (corner) shape, as shown in FIG. 4(a). Therefore, when the substrate is placed at the center of the electrode, uniform etching can be achieved because the magnitude of the electric field (field strength) is almost constant at the center of the electrode, as shown in Figure 4 (c). However, as the size of the substrate increases, the electric field increases at the edge of the electrode, so the etching rate in this area becomes higher than in the center, and the uniformity of the etching rate deteriorates. In addition, as explained in the conventional example, in the apparatus shown in FIG. 3, the distance between the electrodes in the central part is made shorter than that in the peripheral part, and the electric field distribution between the electrodes is brought closer to uniformity, thereby improving the uniformity of the etching rate. I'm trying to make money. However, the electric field distribution may change discontinuously, and even if the electric field distribution becomes approximately uniform under certain conditions and the etching rate becomes approximately uniform, as shown in FIG. 5(a). As shown in (b), when the distance between the electrodes is shortened, the electric field distribution becomes non-uniform and the etching rate also becomes non-uniform, making it necessary to change the electrode shape each time the etching experimental conditions are changed. In the electrode shape according to the present invention, the electric field distribution between the electrodes becomes uniform as shown in FIG. 6(c) by adding curvature to the electrode end (outer periphery) as shown in FIG. 6(a), which increases the etching rate. The uniformity of the process also improves. Furthermore, even when the distance between the electrodes is shortened, although the electric field strength increases, the electric field distribution remains uniform, and the uniformity of the etching rate remains unchanged. As described above, in this example, in the parallel plate type dry etching apparatus, since the upper and lower electrodes have curvatures at the ends, the electric field distribution between the electrodes becomes uniform, and the uniformity of the etching rate can be improved. In the above embodiment, the ends of both the upper and lower electrodes are curved, but the same effect can be expected even if only one of the ends is curved.

〔Effect of the invention〕

As described above, according to the present invention, in a parallel plate type dry etching apparatus, since the electrode ends are curved, the electric field distribution between the electrodes becomes uniform, and the uniformity of the etching rate can be improved.

[Brief explanation of drawings]

FIG. 1 is a diagram showing a dry etching apparatus according to an embodiment of the present invention, FIG. 2 is a sectional view showing the electrode end of the apparatus in FIG. 1, and FIG. 3 is a diagram showing a conventional dry etching apparatus. Figure 4 (al. (bl) is a schematic diagram of the electrode configuration and electric field strength distribution diagram of a conventional dry etching device, respectively, and Figures 5 (a) and (b) are respectively the electrode configuration of the conventional example in Figure 3. 6(a) and 6(b) are a schematic diagram and an electric field strength distribution diagram of the dry etching apparatus according to the present invention, respectively.

Claims (1)

[Claims] (1) A vacuum vessel whose interior is evacuated to a predetermined pressure has first and second electrodes provided facing each other, a workpiece is placed on the first electrode, and the first and second electrodes are placed opposite each other. In a dry etching apparatus that applies high frequency power between two electrodes to generate plasma and etch a workpiece, the first and second electrodes are arranged parallel to each other, and at least one of the two electrodes is A dry etching device characterized by providing a curvature at the end of the electrode.