JPH0562814B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a plasma processing apparatus having an improved electrode structure for introducing gas necessary for generating plasma.

[Conventional technology]

BACKGROUND ART Conventionally, there is a gas introduction section shown in FIG. 4, for example, as a gas introduction section that introduces gas from one of opposing electrodes between the electrodes. The gas introduction part 21 is a circular plate made of aluminum or stainless steel, in which a large number of holes 22 having a diameter of 0.5 mm to several mm are mechanically bored. There is also one using sintered quartz with a pore diameter of about 0.3 microns.

[Problem that the invention seeks to solve]

The conventional gas introduction section 21 as shown in FIG.
Since a large number of holes 22 were mechanically punched in a circular plate made of aluminum or stainless steel, the amount of gas introduced between the electrodes could be uneven in some places due to the positional accuracy of the holes 22, the accuracy of the hole diameter, etc. There has been a problem in that the etching rate becomes uneven depending on the location due to abnormal discharge occurring at the edges of the holes 22. Further, when stainless steel is used as the gas introduction part 21, there is a problem in that nickel, which is a component of the stainless steel, is spattered and contaminates the workpiece. Furthermore, when porous sintered quartz is used as the gas introduction portion 21, there is a problem in that the porous sintered quartz itself is also etched when the silicon dioxide film is etched.

Furthermore, in the case of sintered quartz, the pore diameter is 90 or more.
It is 3000 Å, which is quite small, and when trying to obtain the required flow rate, for example, about 300 c.c./min, with a differential pressure of 0.5 to 1 Kgf/cm ² , such as in dry etching,
There is a problem that as the number of pores increases, the strength of the porous body becomes weaker. Furthermore, since the manufacturing method involves sintering powdered glass with a certain uniform particle size, there is a problem that the pore size and number of pores cannot be controlled as desired.

In addition, the thickness of this porous body is usually 3 mm.
It is desirable to keep the amount below. The reason for this is that the dielectric material corresponding to the thickness is inserted between the electrodes, causing attenuation of the power supplied for plasma generation. Therefore, if a porous sintered body of quartz with a thickness of 3 mm or less is to be made to cover an electrode of a normal size of 150 to 220 mm in diameter, it would be quite difficult to make it strong. Furthermore, in sintered quartz, which can only obtain pore diameters of 90 to 3000 Å,
For example, when etching a SiO ₂ film, various reaction products generated by gas plasma reactions during etching may accumulate at the gas outlet, blocking the hole or causing non-uniformity in the gas outlet. Therefore, there is a problem in that it causes non-uniformity in processing.

[Means for solving problems]

In order to solve the above-mentioned problems, a structure is adopted in which a porous material containing a metal oxide as a main component is placed on the electrode as the gas introduction part 2 that introduces gas between opposing electrodes, and a porous material that is attached to the electrode is used. Electrical connections are made by attaching a conductive substance to the inside of the porous body.

FIG. 1 shows a basic configuration diagram of the present invention. In the figure,
1 is a gas pipe for introducing gas, 2 is a gas introduction part made of a porous material mainly composed of metal oxide, and 3 is a conductive material, such as a sputtered aluminum film, attached to the inside of the gas introduction part. ,4,6
is an electrode for generating plasma by discharging,
Reference numeral 5 represents a workpiece for performing ion etching treatment, etc., and 7 represents a high frequency power source.

In FIG. 1, the gas introduction section 2 is the gas pipe 1.
It is for introducing the gas that has flowed in between the electrodes 3 and 5, and is made of a porous body of metal oxide, such as alumina. Gas that has flowed in through the gas pipe 1 is introduced between the electrodes 4 and 6 from the gas introduction section 2 . Then, by supplying high-frequency power from a high-frequency power source 7 between the electrodes 4 and 6, the introduced gas is turned into plasma, and the workpiece 5 placed on the electrode 6 is etched, for example. .

As explained above, since the gas introduction section 2 made of a porous material containing metal oxide as a main component is used, it is possible to uniformly spray the gas onto the workpiece 5 in a so-called diffusing manner. .

[Effect]

As shown in FIG. 1, gas that has flowed in through a gas pipe 1 is uniformly blown onto a workpiece 5 via a gas introduction section 2 according to the present invention. In addition, since a porous body containing metal oxide as the main component is used as the gas introduction section 2 for spraying gas onto the workpiece 5, even if the gas introduction section 2 is exposed to plasma, the etching rate will vary depending on the location. There will be no unevenness depending on the In addition, since a conductive substance is attached to the inside of the gas introduction part 2, which is made of a porous material mainly composed of metal oxides, to make it conductive, stable and high-density plasma can be generated. .

〔Example〕

FIG. 2 shows a side view of one embodiment of the present invention. In the figure, 8 represents a processing tank, and 9 represents an electrode ring for electrically connecting the gas introduction part 2 and the electrode 4. Note that 1 to 7 in the figure correspond to those shown in FIG. 1, respectively.

In FIG. 2, gas flowing in through the gas pipe 1 spreads into the space formed between the electrode 4 and the gas introduction section 2. In FIG. Then, the gas that has passed through the gas introduction section 2 made of a porous material containing metal oxide as a main component is sprayed onto the workpiece 5 placed on the electrode 6 with good uniformity in a so-called diffusion manner. When high frequency power generated by the high frequency power source 7 is supplied between the electrodes 4 and 6 in this state, plasma is generated between the electrodes, and the workpiece 5 can be etched.

At this time, it is effective to use a porous plate containing metal oxide as the main component as the gas introduction part 2 in order to always spray a uniform amount of gas to any location on the workpiece 5. In order to obtain the high plasma potential necessary for particularly high-speed etching, the distance between the electrodes 4 and 6 is made small, and the gas is distributed uniformly to any part of the workpiece 5. A conventional shower-type structure as shown in FIG. 4 has been considered as a gas introduction section in order to spray gas onto the air. However, when holes are formed mechanically or using laser light, even if the hole diameter is made small, the non-uniformity of the hole diameter causes non-uniformity in plasma processing, and sometimes strong local discharges occur. I was letting it happen. In contrast, by using the porous gas introduction part 2 according to the present invention, the gas can be sprayed uniformly to any location on the workpiece 5 in a manner that diffuses the gas, thereby generating uniform plasma. In addition, since this is a porous plate, there are no edges that occur when holes are drilled in the conventional method, and localized strong discharges do not occur.

Furthermore, when the inter-electrode distance between the electrodes 4 and 6 is reduced, the impedance of the workpiece 5 on the electrode 6 is generally higher than the impedance of the plasma during discharge. If the plasma comes into contact with a metal surface that has not been exposed, short-circuit current is likely to occur there. This short-circuit current destroys (damages) the workpiece 5, and in the case of etching, the etching speed decreases or the etching becomes uneven depending on the location. In particular, when an aluminum gas introduction part with an alumite treatment on the surface of the gas introduction part 2 is used as in the past, the coating on the perforated part of the gas introduction part may be etched due to localized strong electrical discharge. At the same time, the metal surface is exposed. As a result, a short circuit current flows, damaging the workpiece 5, reducing the etching processing speed, and causing problems in durability and reliability. In contrast, the gas introduction section 2 according to the present invention, which uses a porous body mainly composed of a metal oxide, does not generate strong discharge because it is a porous body, and is not corroded by plasma. Further, since the metal can be prevented from being exposed by covering a part of the electrode 4, it is possible to prevent the generation of short circuit current due to the exposed metal and eliminate the above-mentioned trouble.

Alumina is particularly excellent as a metal oxide used in the porous body of the present invention. For example, the porous alumina body can be manufactured by the following method. That is, muddy alumina is poured into a foamed resin body whose pore size has been adjusted to a predetermined pore size, and it is fired to form a porous alumina body. By adjusting the pore size of the foamed resin, the pore size of the porous material can be controlled within a fairly large range of 0.5 to several tens of microns, and it is possible to improve uniformity or partially change the pore size. You can also do it. Moreover, it is possible to produce a fairly dense body using the same process and the same ingredients, and moreover, it is possible to manufacture it as a continuous body. It has superior strength compared to sintered quartz, and even a porous body with a thickness of 2 mm has sufficient strength for practical use.

Incidentally, with a large pore diameter as described above, there is no fear that the pores will be blocked by reaction products. In addition, alumina has superior corrosion resistance when compared to quartz, and can withstand plasma of fluorine-based gases such as CF ₄ and CHF ₃ used when etching SiO ₂ , making uniform etching possible.

Furthermore, in the present invention, since the conductive substance 3 is attached directly to the inner surface of the gas introduction part 2 which is made of a porous body mainly composed of metal oxide, the conductive substance 3 can be brought into electrical contact with the electrode. , this can be used as a new electrode. The attenuation of the applied power due to the insertion of the dielectric is reduced, and the reduction in etching rate can be suppressed to, for example, 5% or less, even when compared with the case of an aluminum electrode (shower head type) whose surface is alumite-treated. Conventional methods suffer from a 40 to 45% reduction in etching speed due to power attenuation.

The conductive film added to the porous body is applied to a thickness of, for example, 1 micron or more by sputtering or the like in order to obtain the necessary adhesion strength. When this conductive film is deposited, for example, even if the distance between the electrodes 4 and 6 is reduced to perform high-speed etching, the plasma is significantly reduced compared to when no conductive material is deposited. In addition to being able to generate stable etching, the distance between the electrodes can be further reduced to increase the plasma density and increase the etching rate.

FIG. 3 shows principal part plan views and side sectional views of various embodiments of the gas introduction section 2 according to the present invention. In the figure, 10 is a porous body with relatively high air permeability, 11 is a porous body with relatively low air permeability, 12 is a normal porous body, 13 is a dense porous body, and 14 and 15 are porous bodies. Bodies 16 and 17 represent compact bodies.

As shown in FIG. 3a, by using a porous body 11 in the central portion of the gas introduction section 2 that has a low air permeability, a uniform gas can be blown onto the workpiece 5. That is, since the inside of the processing tank 8 shown in FIG. 2 tends to be large near the center and small near the edges. Therefore, if the ventilation rate is made the same from the center to the edge of the gas introduction section 2, the amount of gas blown onto the workpiece 5 will be large near the center, and the amount will decrease as it approaches the edge. becomes less. For this reason, in order to reduce the gas permeability near the center of the gas introduction part 2, a porous body 11 with a low permeability is used near the center in FIG.
In FIG. 3b, a dense porous body 13 is used near the center, in FIG. 3c, a dense porous body 16 is used to cover the back surface near the center, and in FIG. 3d, a dense porous body 17 is used.
The area near the center is replaced with . The porous body 11 with low air permeability, the dense porous body 13, the dense body 16, and the dense body 17 described above need to be made of materials that do not have an adverse effect on plasma processing, but generally For convenience of manufacture, it is convenient to use a porous material having the same components as other porous materials. Note that the change in the amount of gas blown onto the workpiece 5 that occurs as it approaches the edge from the center of the gas introduction section 2 is due to the exhaust characteristics of the processing tank 8 and the difference between the electrodes 4 and 6. This is determined by the distance, the diameter of the gas pipe 1, etc., and the embodiments of the present invention are selected accordingly.

〔Effect of the invention〕

As explained above, according to the present invention, as the gas introduction section 2 that introduces gas between opposing electrodes,
Since a porous material mainly composed of metal oxide is attached to the electrode, gas can be sprayed uniformly onto the workpiece 5, and the gas introduction section 2 can be heated by plasma. Since it is rarely etched, the workpiece 5 is not contaminated. Furthermore, by attaching the conductive substance 3 to the inner surface of the gas introduction part 2 which is made of a porous body containing metal oxide as a main component, stable and high-density plasma can be generated.

[Brief explanation of the drawing]

FIG. 1 is a side view of the basic configuration of the present invention, FIG. 2 is a side view of the configuration of one embodiment of the present invention, FIG. 3 is a plan view and side sectional view of the main configuration of the present invention, and FIG. 4 is a side view of the basic configuration of the present invention. 1 shows a plan view of the configuration of a conventional plasma processing apparatus. In the figure, 1 is a gas pipe, 2 is a gas introduction part, 3 is a conductive material, 4 and 6 are electrodes, 5 is a workpiece, and 7 is a high frequency power source.

Claims (1)

[Claims] 1. A workpiece placed on the electrodes is processed by introducing gas injected from the electrode surface between opposing electrodes and supplying high frequency power between the electrodes to generate plasma. In the plasma processing apparatus for processing, in order to introduce gas between the opposing electrodes, the plasma processing apparatus is arranged on a corresponding surface of one of the opposing electrodes,
In addition to changing the gas permeability from other parts, a gas introduction part 2 of a porous body is provided, the inside of which does not face other electrodes is made conductive and electrically connected to the electrode, and the gas of this porous body is 1. A plasma processing apparatus characterized in that a uniform plasma is generated by gas injected through an introduction part 2 to treat a workpiece. 2. Claim No. 2, characterized in that when the permeability of the gas is changed from that of other parts, the part is replaced with a porous body having a different permeability, or the part is covered with a porous body. The plasma processing apparatus according to item 1.