JPH06333878A - Plasma etching device - Google Patents

Abstract

PURPOSE:To provide a plasma etching device wherein a work can be less contaminated and enhanced in etching uniformity. CONSTITUTION:Plasma etching is carried out in a plasma etching device through such a manner that plasma is generated between the counter electrodes 1 and 2 by supplying a high frequency power between the electrodes 1 and 2 as gas jetted out from the opposed surface of the electrode 1 is introduced between them, and a work 8 placed on the other electrode 2 is worked by the plasma concerned, wherein a gas introducing plate 5 of single crystal Si (silicon) or polycrystalline Si is provided to the opposed surface of the electrode 1 where gas is jetted out. Gas blowout, holes 7 0.2 to 1mm in diameter are provided to the gas introducing plate 5. A cavity 6 is provided inside the gas introducing plate 5, and the gas introducing plate 5 is brought into electrical and thermal contact with electrode 1 at the periphery of the cavity 5.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a plasma etching apparatus, and more particularly to a plasma etching apparatus having an improved electrode for introducing a gas required for generating plasma.

[0002]

2. Description of the Related Art Conventionally, when a gas is introduced between two electrodes facing each other between the electrodes, a gas introduction plate is provided on the surface of the electrode into which the gas is introduced. As the material of the gas introduction plate, aluminum, stainless steel, quartz, alumina sintered body, graphite, glassy carbon, or a composite material obtained by coating graphite with, for example, silicon carbide or pyrolytic carbon is used. Came. Further, the gas introduction plate made of any of the above materials is provided with a hole for introducing a gas between two electrodes facing each other, and this hole is provided for uniform generation of plasma generated between the electrodes. In order to ensure the property, a plurality of cells are arranged in a grid pattern, and a spacer ring or the like is installed between the electrode and the gas introduction plate to form a gap so that the gas is uniformly ejected from all the holes. It is generally structured.

[0003]

The problems of the gas introducing plate formed of each of the above materials will be described below.

When a material such as aluminum or stainless steel is used and a gas introduction plate having a large number of holes mechanically formed therein is used, aluminum, nickel, etc. constituting the material are sputtered and the workpiece is There are problems such as contamination, non-volatile reaction products remaining on the workpiece, and deterioration of electrical characteristics.

In order to avoid the above-mentioned problem of contamination of the workpiece with metals and metal compounds, quartz, alumina sintered body, graphite, glassy carbon, etc. may be used as the material of the gas introducing plate. However, since the following problems existed, it was difficult to say that any of the materials had all the characteristics that the gas introduction plate should satisfy.

That is, when quartz is used as the gas introduction plate, there is a problem that the quartz itself is also etched when the SiO ₂ film is etched.
Furthermore, when a dielectric such as quartz is used as the gas introduction plate, the dielectric of the thickness is inserted between the electrodes, so it is necessary to reduce the supply power for plasma generation. Therefore, the thickness of the gas blowing plate must normally be 3 mm or less. For this reason, a quartz disk having a thickness of 3 mm or less and a diameter of 150 to 300 mm covering an electrode of a normal size is formed, and a large number of holes are mechanically formed in the disk, so that the strength is considerably unreasonable. Cause Furthermore, when an insulator is placed on the electrode, the potential of the electrode and the surface potential of the insulator do not match, so discharge easily enters the hole for introducing gas, and the discharge in the hole When the temperature rises, the pore size becomes large due to the spattering phenomenon, so that discharge is more likely to occur and the plasma becomes significantly nonuniform, making it unusable. Instead of making holes mechanically, a porous sintered body is used as a material and its mechanism is used for gas introduction, but it has only a small pore diameter from 90 Å to 3000 Å at the maximum. With sintered quartz, when etching the SiO ₂ film, various reaction products generated by the reaction of gas plasma during etching are deposited on the gas outlets, blocking the holes or making the gas outlet uneven. There is a problem such as occurrence of.

Further, when the alumina sintered body is used as the gas introduction plate, the alumina sintered body is superior to quartz in terms of mechanical strength, but since the dielectric loss is larger, the interelectrode gap is increased. If the high frequency power is applied by arranging the sintered body in, the plasma generation efficiency will decrease,
When the surface is exposed to plasma and is sputtered, there is a problem that the work piece is contaminated with alumina or aluminum, or a reaction product remains on the work piece.

Further, when graphite is used as the gas introduction plate, there is no electrical problem, and a reaction product of the generally used etching gas and graphite is used even when exposed to plasma and sputtered. Since it is volatile, there is no problem. However, since graphite is mixed with pitch components during firing and fired, when exposed to gas plasma, the portion composed of this pitch has a higher chemical reactivity than the aggregate portion and is consumed quickly. As a result, there is a problem that there is no support for the aggregate and particles fall off as particles, and the particles that have fallen off adhere to the work piece to cause contamination.

In order to overcome the disadvantages of graphite as described above, it has been attempted to coat the surface of graphite with a film made of a material such as silicon carbide or pyrolytic carbon to prevent the particles from falling off. The thickness of these coatings is limited to at most 200 μm because the thicker the coating, the easier the peeling due to the residual stress at that time and the difference in thermal expansion coefficient between the material of the coating and graphite. Therefore, such a composite material, the surface of which is exposed to plasma and constantly eroded, changes its electrical and thermal properties every moment as the thickness of the coating changes, and is unsuitable as a gas introduction plate. . Furthermore, when the surface coating film is sputtered and the graphite of the base material is exposed, the particles come off like graphite, and it is considered that the life has expired, but with a film thickness of about 200 μm, it is very short. It is inconvenient because it requires parts replacement.

When glassy carbon is used as the gas introduction plate, no particles are generated due to variations in etching resistance inside a material such as a graphite molding material. However, glassy carbon has a very high hardness and is prone to chipping, and it is difficult to form holes for introducing gas. Moreover, in the case of glassy carbon, when exposed to plasma and heated to high temperature, crystallization occurs due to thermal shock and fine crystals are generated,
There is a problem in that the generated fine crystals adhere to the work to cause contamination.

Furthermore, since the gas introducing plate is exposed to plasma, it is necessary to cool it by some means and keep its temperature below a certain value.
When forming a gas introduction plate with a material such as graphite or glassy carbon or a composite material that uses graphite as a base material, it is not possible to bury the water channel for direct water cooling with these materials, so Cooling is indirectly performed by contact with the spacer. Under such conditions, if an attempt is made to provide a gap for uniformly ejecting the gas between the gas introduction plate and the electrode, heat transfer between the gas introduction plate and the electrode will be limited to the area of the gap. Since the contact area decreases, it deteriorates and the temperature of the gas introduction plate easily rises. In addition, heat is transferred in the in-plane direction of the gas introducing plate at the portions not in contact with the electrodes or the spacers between the electrodes. Insulators such as quartz and alumina whose thickness is limited, and materials such as glassy carbon cause temperature unevenness in the surface exposed to plasma due to the difference in distance between the electrode and the contact area with the spacer. In particular, etching of SiO ₂ causes uneven etching. Furthermore, if the thickness of the gas introducing plate, including graphite, is reduced by being exposed to plasma for a long period of time and sputtered, the heat transfer rate in the surface direction becomes smaller, so the temperature is more likely to rise. There is also a problem that in-plane temperature unevenness becomes severe, causing not only etching unevenness but also a change over time in etching characteristics.

In view of the above-mentioned problems, an object of the present invention is to provide a plasma etching apparatus in which the occurrence of contamination of the work piece is reduced and the etching uniformity is improved.

[0013]

The plasma etching apparatus according to the present invention has the following configuration.

Plasma is generated by introducing gas injected from the facing surface of one of the electrodes between two electrodes facing each other and by supplying high-frequency power between the electrodes, and is installed on the other electrode. In the plasma etching apparatus for processing the processed object, a gas introduction plate made of single crystal Si (silicon) or polycrystalline Si is attached to the facing surface of the electrode for injecting the gas.

In the above construction, preferably, the gas introducing plate is formed with a plurality of gas blowout holes having a diameter of about 0.2 to 1 mm.

In the above structure, preferably, a gap is provided inside the gas introduction plate, and the gas introduction plate and the electrode are electrically and thermally contacted with each other at the outer periphery of the gap.

In the above construction, preferably, the volume resistance value of the single crystal Si or the polycrystal Si forming the gas introduction plate is a value included in the range of 0.01 to 20Ω.

[0018]

According to the present invention, in a structure in which a gas is introduced between opposing electrodes and a high frequency power is supplied to generate plasma to process a workpiece, a single crystal provided on the electrode facing surface into which the gas is introduced. The gas introduction plate made of Si or polycrystalline Si eliminates the source of metal contamination, and when a fluorine-based gas is used, the reaction product is almost volatile and the product is not deposited on the workpiece. Further, since the gas introduction plate has a high heat transfer coefficient, the temperature difference between the contact portion with the electrode and the central portion where the gap portion is present is very small, and the temperature unevenness does not occur. Therefore, etching unevenness does not occur. Since a gap for allowing the supplied gas to flow is formed inside the gas introduction plate, the gas is dispersed in advance and blown out from a large number of pores and blown onto the workpiece in a uniform manner.
The gas introducing plate is efficiently cooled by the contact portion between the electrode and the gas introducing plate, the reproducibility of the temperature thereof is maintained, and the reproducibility of the etching characteristics can be obtained.

[0019]

Embodiments of the present invention will be described below with reference to the accompanying drawings.

FIG. 1 is a vertical cross-sectional view showing a principle structure of a main part of a plasma etching apparatus according to the present invention. In FIG. 1, reference numerals 1 and 2 denote two electrodes that are opposed to each other with a predetermined space therebetween, and are electrodes for generating plasma in a space between them by discharge. The shape of the facing surface of each electrode is generally circular. A required power is supplied between the electrodes 1 and 2 by a high frequency power supply 3. In the case of this embodiment, the electrode 1 located on the upper side is provided with a gas pipe 4 for introducing a gas between the two electrodes. Further, a gas introduction plate 5 made of single crystal Si or polycrystalline Si is provided on the opposite surface of the electrode 1.
Is attached. The gas introducing plate 5 is provided with a gap 6 in the space between the gas introducing plate 5 and the electrode 1 by forming a recess on the inner surface.
Is formed. The gap 6 serves as a flow path (or a void) for allowing the gas introduced by the gas pipe 4 to flow. The gas introduction plate 5 is a portion formed around the gap portion 6 and is in contact with the peripheral portion of the facing surface of the electrode 1 and is fixed to the electrode 1 by using, for example, a fastening means (not shown). Further, a large number of holes 3 for ejecting the gas introduced by the gas pipe 1 into the space between the two electrodes are formed in the gas introduction plate 5. A workpiece 8 to be ion-etched is placed on the upper surface of the electrode 2 located on the lower side.

In the structure shown in FIG. 1, the gas supplied through the gas pipe 4 diffuses in the gap 6 along the surface of the electrode 1, and passes through a large number of holes 7 formed in the gas introduction plate 5 to form the electrodes 1, 2. It is introduced into the space between two. Next, when high-frequency power is supplied from the high-frequency power source 3 between the electrodes 1 and 2, the introduced gas is turned into plasma, and the workpiece 8 placed on the electrode 2 is etched.

The gas flowing in through the gas pipe 4 is diffused in the inside of the gap 6 provided inside the gas introducing plate 5, and then passes through the hole 7 formed in the gas introducing plate 5 to be processed 8 Is sprayed on in a uniform manner. Further, since single crystal Si or polycrystalline Si is used as the material of the gas introduction plate 5 for introducing the gas between the electrodes 1 and 2, even if the gas introduction plate 5 is exposed to plasma, a metal such as aluminum is used. There is no pollution source, especially when a fluorine-based gas is used, the reaction product is almost volatile, and
No product is deposited on top. Further, since the gas introduction plate 5 made of single crystal Si or polycrystalline Si has a heat transfer coefficient as high as that of aluminum, even if the surface of the gas introduction plate 5 is heated by plasma, it is close to the contact portion with the electrode 1. The temperature difference between the portion and the central portion where the gap portion 6 exists is very small, and the temperature unevenness on the surface of the gas introduction plate 5 which causes the etching unevenness does not occur.

Further, since the entire gas introducing plate 5 is efficiently cooled from the contact portion with the electrode 1, the gas introducing plate 5 maintains the reproducibility of the temperature repeatedly even if repeatedly exposed to the plasma for a long time, and the etching is performed. Good reproducibility of characteristics can be obtained. Further, by forming the gas introducing plate 5 with the above-mentioned material, even if the gas introducing plate is sputtered by plasma and eroded for a long period of time to reduce its thickness, the material of the surface exposed to plasma does not change, There is no generation of particles that contaminate the wafer or the like, and changes in thermal properties and electrical properties can be made smaller than those of other materials. Furthermore, since the gas introducing plate 5 is made of conductive single crystal Si or polycrystalline Si, it is possible to efficiently generate stable and high-density plasma with little power loss.

In the above structure, by selecting the diameter of the hole 7 for ejecting the gas in the gas introducing plate 5 to be 0.2 to 1 mm, strong discharge is less likely to occur in the hole portion, and further, the gas introducing plate 5 The above-mentioned gap 6 is provided in the above, the gas is diffused between the electrode 1 and the gas introduction plate 5 in the direction along the facing surface in advance, and then the gas passes through a large number of holes 7 provided at appropriate intervals. By doing so, a gas with good uniformity can be ejected.

The width d of the gap 6 is set so that the diffusion of the gas in the surface direction of the electrode is sufficiently faster than the speed at which the gas is introduced between the electrodes 1 and 2 through the hole 7. Let it be the length. The thickness of the gas introduction plate 5 is 6 mm to 10 mm.
The degree is desirable. With such a thickness, there is little power loss, and even if the thickness is reduced by being exposed to plasma and sputtered, sufficient heat conduction in the direction parallel to the electrode surface can occur. It is possible to obtain stable etching characteristics over a long period of time. Further, it is desirable that the volume resistance value of the single crystal Si or the polycrystalline Si forming the gas introduction plate 5 is a value included in the range of 0.01 to 20Ω. In the gas introduction plate 5 having such a volume resistance value, the potential is maintained at a desired potential in relation to the electrical contact portion with the electrode 1, and contributes to the stability of plasma.

FIG. 2 shows another specific embodiment of the present invention. In FIG. 2, elements that are substantially the same as the elements described in FIG. 1 are given the same reference numerals. In the configuration of FIG. 2, the two electrodes 1 and 2 described in FIG. The electrode 1 is provided with a gas introduction plate 5 on its opposite surface. Flow paths 10 and 11 are formed in the electrodes 1 and 2 for flowing a heat medium for adjusting the temperature of each electrode to a desired temperature. Cooling water is an example of the heat medium. An exhaust device (not shown) is attached to the processing bath 9, and the inside of the processing bath 9 is exhausted in advance by this exhaust device and is maintained in a vacuum state. The gas flowing into the vacuum processing tank 9 through the gas pipe 4 diffuses into the gap 6 formed between the electrode 1 and the gas introduction plate 5. Then, the gas that has passed through the holes 7 formed in the gas introduction plate 5 made of single crystal Si or polycrystalline Si is sprayed onto the workpiece 8 placed on the electrode 2. When high-frequency power generated by the high-frequency power supply 3 is supplied between the electrodes 1 and 2 in this state, plasma is generated between the electrodes and the workpiece 8 is etched. Electrode 1,
In the present embodiment, 2 is cooled by the cooling water flowing through the flow paths 10 and 11, and indirectly prevents the gas introduction plate 5 and the workpiece 8 from being heated to a high temperature by the etching process.

In the above case, single crystal Si is used as the gas introduction plate 5.
Alternatively, since polycrystalline Si is used, there is an advantage that even if the surface of the gas introducing plate 5 is continuously eroded by the sputtering action of plasma, the effect of preventing metal contamination or contamination by peeling particles on the workpiece 8 does not change at all. can get.

In the above embodiment, the high frequency power source 3 is connected to the electrode 2 on the side where the workpiece 8 is placed, but the high frequency power source 3 may be provided to the electrode 1 provided with the gas introduction plate 5. it can.

FIG. 3 is a partial sectional view of another embodiment. In this embodiment, the gas conductive plate 5 is formed into a flat plate shape, and the metal ring 12 is provided between the gas conductive plate 5 and the electrode 1 to attach the gas conductive plate 5 to the electrode 1. Metal ring 12
By interposing, the gap portion 6 is formed between the gas conductive plate 5 and the electrode 1. The metal ring 12 is arranged in a place where it is not exposed to the plasma as much as possible.

[0030]

As is apparent from the above description, according to the present invention, since the gas introducing plate attached to the electrode into which the gas is introduced is made of single crystal Si or polycrystalline Si, the gas introducing plate is sputtered by plasma. Even if it is eroded and eroded over a long period of time to reduce its thickness, the work piece will not be contaminated by metal or exfoliated particles. In addition, a gap is formed between the gas introduction plate and the electrode to allow gas to pass, and the introduced gas is diffused along the electrode surface in the gap and then introduced between the electrodes through the dispersively formed pores. With this configuration, uniform plasma can be generated, and good etching uniformity can be obtained. Further, since the gas introduction plate is directly attached to the electrode at the outer peripheral portion of the gap to realize electrical and thermal contact, repetitive reproducibility of etching can be obtained. Particularly in a narrow gap type etching apparatus, since the surface temperature of the electrode facing the electrode on which the workpiece is placed is easily affected, the present invention is effective in such an apparatus.

[Brief description of drawings]

FIG. 1 is a vertical sectional view showing a basic embodiment of a plasma etching apparatus according to the present invention.

FIG. 2 is a vertical cross-sectional view showing a specific example.

FIG. 3 is a longitudinal sectional view of an essential part showing another embodiment.

[Explanation of symbols]

 1, 2 electrodes 3 high frequency power supply 4 gas pipe 5 gas introduction plate 6 gap 7 hole 8 workpiece 9 processing tank 10, 11 flow path

Claims (4)

[Claims] 1. A plasma is generated by introducing a gas injected from the facing surface of one of the electrodes between two electrodes facing each other and supplying high-frequency power between the two electrodes to generate plasma. In a plasma etching apparatus for processing a workpiece placed on the electrode, a single crystal Si or a polycrystalline Si is formed on a surface facing the electrode for injecting the gas.
A plasma etching apparatus, characterized in that a gas introduction plate consisting of is attached. 2. The plasma etching apparatus according to claim 1, wherein the gas introducing plate is provided with a plurality of gas outlet holes having a diameter of about 0.2 to 1 mm. 3. The plasma etching apparatus according to claim 1, wherein a gap portion is provided inside the gas introduction plate, and the gas introduction plate and the electrode are electrically and thermally contacted with each other at an outer peripheral portion of the gap portion. A plasma etching apparatus characterized in that 4. The plasma etching apparatus according to claim 1, wherein the volume resistance value of the single crystal Si or the polycrystalline Si forming the gas introduction plate is 0.01.
A plasma etching apparatus having a value within a range of -20Ω.