JPS6017031B2 - plasma etching equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a plasma etching apparatus that generates plasma using high frequency power.

More specifically, the present invention relates to a plasma etching apparatus that is provided with a cathode electrode that generates a holo-cathode effect and performs powerful etching with a reactive gas blown out through the cathode electrode. In conventional plasma etching, when the high-frequency power applied between the electrodes is increased in order to increase the etching rate, the self-bias voltage generated between the electrodes also increases, causing ions to violently collide with the semiconductor substrate and cause crystal defects. Become.

Furthermore, the amount of heat generated by the collision of ions also increases, causing a sharp rise in temperature on the surface of the semiconductor substrate, causing a problem that the mask covering this surface may be burnt. In addition, in the case of a multilayer laminated wiring board made of epoxy resin, after drilling holes,
Chips remaining on the side wall of the hole or the conductive film of the intermediate layer that should be exposed on the side wall of the hole after drilling may be fused and covered by the frictional heat from the drill.

Even if plasma etching is performed to remove these chips and fusion properties, there is a problem in that the intermediate portion of the hole is difficult to be etched. The present invention has been made to solve these problems, and it can be used without causing crystal defects for semiconductor substrates, and completely to the inside of thin drill holes for multilayer wiring boards made of epoxy resin. An etching device capable of etching is provided.

This will be explained in detail below with reference to the drawings.

Before explaining the structure, the hollow cathode effect will be explained.

A cathode having two or more U-shaped or cylindrical cathodes in which a negative glow discharge appears at a fixed location from each cathode surface is called a holo-cathode. If the distance between these two or more cathodes is selected to an appropriate value, or if the gas pressure is selected to an appropriate value, the negative glow discharges on each cathode side are combined to form one glow discharge. This is called the hollow cathode effect. In this case, the sustaining voltage of the glow discharge decreases, but the cathode current density increases dramatically. The present invention applies this principle. FIG. 1 shows the main structure of an apparatus suitable for etching a semiconductor substrate as described above, in which only one of the mutually opposing electrodes has a holo-cathode effect.

Here, 1 is an anode, 2 is a cathode with a hollow cathode effect, and 3 is a cathode with a hollow cathode effect.
4 is a capacitor, 4 is a high frequency power supply, and 5 is an object to be etched. When a high-frequency power source is operated, a high-frequency electric field is generated between the electrodes facing each other, and gas molecules between the electrodes are ionized and separated into ions and electrons. In this case, since electrons have extremely light mass, they respond to rapid changes in the high-frequency electric field and rush to the positive electrode at each point, but ions have large mass, so they cannot respond to rapid changes in the high-frequency electric field and It stays in. In this case, electrode (anode) 1 is grounded, so it is always at zero potential, but the electrons that reach electrode (cathode) 2 are charged in capacitor 3, so electrode 2 becomes negative potential and connects the cathode. forming the anode 1
A self-bias voltage is generated between Note that the structure of the cathode for providing the hollow cathode effect will be described later. Figure 2 shows a holo-cathode effect on both electrodes facing each other, and the major difference from Figure 1 is that a capacitor and a high-frequency power source are connected separately between each electrode and ground. There is.

In this way, each electrode forms a cathode as described above, regardless of the phase of the high frequency power source on the other side, and has the hollow cathode effect as described above. This embodiment is suitable for internal etching of a drilled hole in a multi-layer wiring board made of epoxy resin, and etching proceeds from both sides of the hole. FIG. 3 is a cross-sectional view of a reaction chamber portion of an etched diamond plate having a hollow cathode effect, and corresponds to the case of FIG. 1.

In the figure, 1 is an anode, and 2-1 is an electrode rod that is part of the cathode 2. As shown in FIG. 4, this cathode 2 consists of a plurality of electrode rods 2-1, a connecting plate 2-2, and a high-frequency power introduction terminal 2-3. 5 is an object to be etched, 6 is a vacuum container, 7 is a gas inlet, and 8 is a gas outlet, which are provided between the adjacent electrodes 2-1, and even if a plurality of holes are arranged in a row. It's fine, and just one hole is fine.

9 is a gas exhaust port, and 10 is a gas chamber.

By introducing a reaction gas into the vacuum container 6 from the gas inlet 7 and exhausting it from the gas exhaust port 9 with an exhaust pump (not shown) to adjust the amount of introduction and discharge of the reaction gas, the inside of the vacuum container 6 can be It is possible to create a reaction gas atmosphere in a constant reduced pressure state.

Only the reaction gas introduced is from the gas chamber 10 through the gas outlet 8.
Since the air is blown out into the interior of the vacuum container S through the air, the path of this blown air passes between the electrode fins 2-1 of the cathode 2.
When the high frequency power source is turned on and high frequency power is applied to the anode 1 and the cathode 2, a negative glow discharge is generated between the electrode rods 2-1 of the cathode 2 as described above.

In this case, these glow discharges
If the spacing between the electrode fins 2 and 1 is adjusted so that they are combined at one place between the electrodes, or if the pressure inside the vacuum container is adjusted, dense ions are generated by the combined glow discharge. For this reason, even without increasing the high frequency power, a much larger amount of ions is generated than in the case of a simple parallel plate electrode. Moreover, since the high-frequency power is not increased, the self-bias voltage accompanying this does not increase, and the moving speed of ions does not increase. No crystal defects are generated in the semiconductor substrate. Although the illustrated anode 1 has small holes for discharging the reactive gas from the gas outlet 9, it may also have a passageway for the reactive gas in the center or the periphery. The structure of the cathode in this embodiment is simple as shown in FIG. 4, but since the tips of each electrode rod 2-1 are free ends and are not connected, if the frequency of the applied high-frequency power is high, A potential difference occurs even within the same electrode due to inductance within the electrode.

As a result, arc discharge may occur from places with high potential, so it cannot be used at very high frequencies. FIG. 5 shows another embodiment in which the cathode portions shown in FIG. 3 and 4 are different.

That is, the cathode is formed by integrating the electrode rim 2-1, the connecting plate 2-2, the high-frequency power introduction shield 2-3, the gas inlet 7, the gas outlet 8, and the gas chamber 10. For this purpose, in place of the electrode rod 2-1, a plurality of parallel jetties 2-4 were provided on the surface facing the anode 1, and a row was formed between the adjacent jets 2-4. multiple small holes or one
A gas outlet 8 in the form of a long hole is provided. As a result, when high-frequency power is applied to both military poles 1 and 2, a strong glow discharge is generated between the jetties 2 and 4, and a large amount of ions are supplied. Moreover, since this cathode 2 has a monolithic structure, the inductance within the electrode is small, and the potential difference within the electrode as described above is 4 mm, so arc discharge does not occur and it can be used even at high frequencies. . As described above, in the apparatus of the present invention, the applied high frequency power is not increased in order to increase the amount of ions generated and speed up the etching rate, so as a result, the self-bias voltage does not increase and the kinetic energy of the ions does not increase. No crystal defects occur. Furthermore, in the case of a wiring board made of multi-layered epoxy resin, etching can be performed from both sides of the object at the same time, which has the effect of shortening the working time. Note that although the device of the present invention can generate a large amount of ions due to the hollow cathode effect, this hollow cathode effect is not generated over the entire cathode surface.

0 For this reason, there is some variation in the etching rate depending on the location of the object to be etched, but this can be easily made uniform by rotating or moving the object to be etched.

As described above, the apparatus of the present invention not only solves the problems of the conventional method, but also has the effect of shortening the working time, so it is extremely effective in practice.

[Brief explanation of drawings]

1 and 2 are explanatory diagrams explaining the operating principle 0 of the apparatus of the present invention, FIG. 3 is a sectional view of a reaction chamber portion of an embodiment of the present invention, and FIG. 4 is a cathode in the case of FIG. 3. FIG. 5 is a sectional view of the reaction chamber portion of another embodiment of the present invention. In the figure, 1 is an anode, 2 is a cathode, 3 is a capacitor,
4 is a high frequency power source, and 5 is an object to be etched. Figure 1 r Figure 2! Figure 3 Figure 4 Figure 5

Claims (1)

[Claims] 1. In a plasma etching device that generates plasma using high-frequency power, one of the opposing electrodes is provided with a means for expressing a hollow cathode effect, and this electrode is connected to a capacitor and a high-frequency power supply. A plasma etching apparatus characterized in that the other of the mutually opposing electrodes is directly grounded, and a reactive gas outlet is provided between the hollow cathode effect means. 2. In a plasma etching device that generates plasma using high-frequency power, both of the electrodes facing each other are provided with means for expressing a hollow cathode effect, and both electrodes are individually grounded via a capacitor and a high-frequency power source. A plasma etching apparatus characterized in that a reactive gas outlet is provided between the means for expressing the hollow cathode effect of each of the electrodes. 3. A plasma etching apparatus according to one of claims 1 and 2, including a plurality of electrode rods arranged in parallel and at equal intervals as electrodes provided with means for expressing a hollow cathode effect; The plasma etching apparatus is characterized in that it comprises a connecting plate that connects one end of each of these electrode rods. 4. In the plasma etching apparatus according to one of claims 1 and 2, the electrode is provided with a means for expressing a hollow cathode effect, which has a hollow structure and is arranged at equal intervals on the surface facing the other electrode. A plurality of jetties are provided parallel to each other, a gas outlet is provided at the bottom between these jetties, and a gas inlet is provided on the surface opposite to the surface facing the other electrode. The plasma etching apparatus.