JPH05109664A - Plasma etching system - Google Patents

Abstract

PURPOSE:To provide the title plasma etching system capable of diminishing the occurrence of polluted element to be processed as well as enhancing the evenness of etching step. CONSTITUTION:Within the title plasma etching system, gas is led into the space between the electrodes 4 and 6 and then high-frequency power is supplied to the space between the electrodes 4 and 6 to produce plasma for etching an element to be processed. On the other hand, a gas leading-in plate 2 comprising a bulk thermal decomposition carbon, a C-axis perpendicular to the surface is provided on the surface of the electrode 4 opposite to the electrode 6. A gap 3 is held between the gap leading-in plate 2 and the electrode 4. The outer periphery of the gas leading-in plate 2 is electrically and thermally in contact with the electrode 4. Furthermore, a gas outlet holes 9 communicating with the gap 3 are provided in the gas leading-in plate 2.

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 in which a gas introducing portion required for generating plasma is improved.

[0002]

2. Description of the Related Art Conventionally, there is known a plasma etching apparatus in which a gas is introduced between electrodes facing each other and etching is performed through plasma of the introduced gas. The gas is introduced from the surface of one of the electrodes facing each other (the counter electrode facing the support electrode that supports the workpiece) between the electrodes. Aluminum, stainless steel, quartz, alumina sintered bodies, graphite, glassy carbon, and composite materials in which the surface of the graphite is covered with a coating of, for example, silicon carbide or pyrolytic carbon have been used.

Further, the gas introduction plate made of any of the above-mentioned materials is provided with a hole for introducing gas between the electrodes facing each other, and this hole is used for plasma generated between the electrodes. In order to ensure the uniformity of the above, a plurality of them are arranged in a grid pattern, and a spacer ring or the like is further installed between the electrode and the gas introduction plate to provide a gap between the electrode and the gas introduction plate. Generally, the structure is such that the gas is uniformly ejected from all the gas introduction holes.

[0004]

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 or the like constituting the member is There are problems that the work piece is contaminated by sputtering, non-volatile reaction products remain on the work piece, and the electrical characteristics of the work piece (for example, a semiconductor device) are deteriorated. ..

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, it was difficult to say that any of the materials had all the characteristics that were satisfactory as the gas introduction plate due to the following problems.

That is, when quartz is used as the gas introduction plate, there is a problem that when the SiO ₂ film of the workpiece is etched, the quartz on the gas introduction plate side is also etched.

Further, when a dielectric such as quartz is used as the gas introducing plate, the dielectric power of the thickness is inserted between the electrodes so that the power supply for plasma generation is attenuated. Therefore, the thickness of the gas blowing plate must usually be 3 mm or less. Therefore,
150mm to 300 in diameter with a thickness of 3mm or less
If a quartz disk is formed to cover an electrode having a normal size of mm, and a large number of holes are mechanically formed in this disk, the strength is considerably unreasonable. Furthermore, if an insulator is placed on the electrode, the potential of the electrode does not match the potential of the surface of the insulator, so a discharge is introduced into the hole for introducing gas (gas blowing hole). Since the diameter of the hole gradually increases due to the spattering phenomenon when an electric discharge is introduced into the gas blowing hole, the electric discharge is more likely to occur and the plasma becomes extremely non-uniform, which makes it unusable. Instead of drilling mechanically,
It is also practiced to use a porous sintered body as a material and use its pores for gas introduction. However, in the case of sintered quartz having a fine pore diameter of 90 angstroms or 3000 angstroms at the maximum, a SiO ₂ film is used. When etching is performed, various reaction products generated by the reaction of gas plasma during etching are gas outlets (pores).
However, there are problems that the holes are blocked, the gas is blown out unevenly, and so on.

Further, when graphite is used as the gas introduction plate, there is no electrical problem, and even when the graphite is exposed to plasma and sputtered, the reaction between the generally used etching gas and graphite. Since the product is volatile, there is no problem. However, since graphite is mixed with a pitch component as a binder at the time of molding and is 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 no support for the aggregate part, and a phenomenon occurs in which the aggregate drops off as particles, and the particles that have fallen off adhere to the work piece, causing contamination. was there.

In order to overcome the drawbacks of graphite as described above, it is also practiced to cover the surface of graphite with a coating film made of a material such as silicon carbide or pyrolytic carbon to prevent the particles from falling off. However, due to the residual stress at the time of film formation and the difference in thermal expansion coefficient between the material of the film and graphite, the thicker the film is, the easier the film is to peel off. It Therefore, such a composite material is unsuitable as a gas introduction plate whose surface is exposed to plasma and is constantly eroded, because the electrical and thermal properties of the composite material change every moment as the thickness of the coating changes. .. Furthermore, when the surface coating film is sputtered and the graphite of the base material is exposed, particles fall off in the same way as in the case of graphite, and it is judged to be the lifespan, but a film thickness of 200 μm is very short. It is inconvenient because parts need to be replaced between them.

Further, when glassy carbon is used as the gas introducing portion, no particles are generated due to variations in etching resistance inside a material such as a graphite molding material. However, glassy carbon has very high hardness and is apt to cause chipping, and it is difficult to process pores for introducing gas. Moreover, in the case of glassy carbon, when it is exposed to plasma and becomes high temperature, crystallization occurs due to thermal shock, and microcrystals are generated, and the generated microcrystals adhere to the work piece. However, there is a problem in that it causes contamination.

Further, since the gas introducing plate is directly exposed to plasma and heated, it is necessary to cool it by some means and keep its temperature below a certain value. Quartz, alumina sintered body, graphite When forming the gas introduction plate with a material such as glassy carbon or a composite material having graphite as a base material, it is impossible to embed a water channel for direct water cooling with these materials. Therefore, the cooling is indirectly performed by contact with the electrode or the spacer interposed between the electrode and the electrode. Under these conditions, if a gap is provided between the gas introduction plate and the electrode for uniformly ejecting the gas, the heat transfer between the gas introduction plate and the electrode is equivalent to the contact area. Is reduced and deteriorates, and the temperature of the gas introduction plate is likely to rise. In addition, heat is transferred in the in-plane direction of the gas introduction plate at a portion that is not in contact with the electrode or the spacer between the electrode and the above material, especially for the reasons described above. Insulators such as quartz and alumina, where the thickness of the gas introduction plate is limited, and materials such as glassy carbon are exposed to plasma due to the difference in distance between the gas contact plate and the contact part with the electrode or spacer. This causes temperature unevenness, which is a cause of etching unevenness particularly in etching SiO ₂ . 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 plane direction becomes smaller, and 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 in etching characteristics over time.

[0012]

The present invention has been made in view of the above problems, and is a plasma capable of reducing the occurrence of contamination of a workpiece and improving the uniformity of etching. An object is to provide an etching apparatus.

In the plasma etching apparatus of the present invention which achieves this object, a gas is introduced between a support electrode supporting a workpiece and a counter electrode facing the support electrode,
High frequency power is supplied between the electrodes to generate plasma,
In a plasma etching apparatus for etching the work piece, on the surface of the counter electrode facing the support electrode,
A gas introduction plate made of bulk pyrolytic carbon with the c-axis perpendicular to the plane is installed with a gap between the counter electrode and the outer periphery of the gas introduction plate to prevent electrical and thermal And the gas introduction plate is provided with a gas blowing hole communicating with the gap.

FIG. 1 shows this configuration in principle. In the figure, 1 is a gas pipe for introducing gas, 2 is a gas introduction plate made of bulk pyrolytic carbon, 3 is a gap provided inside the gas introduction plate, and 4 and 6 are discharged to generate plasma. Electrode, 5 is a workpiece for performing ion etching, 7 is a high frequency power source, 9 is the c-axis direction of bulk pyrolytic carbon, and 9 is for introducing the gas provided on the gas introduction plate between the electrodes. Represents the gas blow-out hole. The bulk pyrolytic carbon has a hexagonal crystal structure, and the C-axis is perpendicular to the hexagonal plane, as shown in FIG.

In FIG. 1, the gas that has flowed in through the gas pipe 1 has a gap portion 3 provided inside the gas introduction plate 2.
Is diffused along the surface of the electrode 4 and introduced between the electrode 4 and the electrode 6 through the gas blowing hole 9 provided in the gas introduction plate 2. By supplying high-frequency power from the high-frequency power source 7 between the electrodes 4 and 6, the introduced gas is turned into plasma between the electrodes and the workpiece 5 placed on the electrodes 6 is processed.
Are etched.

[0016]

As shown in FIG. 1, the gas flowing in through the gas pipe 1 is diffused in the inside of the gap portion 3 provided inside the gas introducing plate 2 according to the present invention and then penetrated into the gas introducing plate 2. The gas is blown through the gas blowing hole 9 to the workpiece 5 in a uniform manner. Further, since bulk pyrolytic carbon is used as the gas introduction plate 2 for supplying the gas between the electrode 4 and the electrode 6, even if the gas introduction plate 2 is exposed to plasma, there is no metal contamination source such as aluminum. In particular, when a fluorine-based gas is used, the reaction product is almost volatile and the product is not deposited on the work piece 5. Further, a gas introduction plate 2 made of bulk pyrolytic carbon
Is configured such that its c-axis 8 is aligned with the direction perpendicular to the surface of the electrode 4, so that the heat transfer coefficient in the direction parallel to the surface of the electrode 4 is as high as that of aluminum. Even if the surface of the plate 2 is heated, the electrode 4
The part close to the contact part (outer peripheral part) and the gap part 3 inside
The temperature difference from the central portion where the gas is present is very small, and temperature unevenness on the surface of the gas introducing plate 2 which causes etching unevenness does not occur. Further, since the entire gas introducing plate 2 is efficiently cooled from the contact portion with the electrode 4, the gas introducing plate 2
Even when repeatedly exposed to plasma for a long time, the reproducibility of the temperature is maintained, and good reproducibility of etching characteristics can be obtained. Further, since the gas introducing plate 2 is made of bulk pyrolytic carbon, the gas introducing plate 2 is sputtered by plasma and eroded for a long period of time, and even if its thickness is reduced, the material of the surface exposed to plasma is Since it is invariable, no particles that contaminate the wafer are generated, and the change in thermal and electrical properties can be made smaller than that of the conventionally used material. Furthermore, since the gas introduction plate 2 is made of conductive bulk pyrolytic carbon, power loss is small, and stable and high-density plasma can be efficiently generated.

[0017]

FIG. 3 shows a plasma etching apparatus according to an embodiment of the present invention. In the figure, 10a and 10b are cooling water channels formed to cool the electrodes 4 and 6, and 11 is a processing tank. 1 to 9 correspond to those shown in FIG. 1, respectively.

In FIG. 3, the gas that has flowed through the gas pipe 1 into the processing tank 11 that has been evacuated and evacuated in advance has a gap portion 3 formed between the electrode 4 and the gas introduction plate 2.
Spread to. Then, the gas that has passed through the gas blowing hole 9 formed in the gas introduction plate 2 made of bulk pyrolytic carbon is blown onto the workpiece 5 placed on the electrode 6.
When high-frequency power generated by the high-frequency power supply 7 is supplied between the electrodes 4 and 6 in this state, plasma is generated between the electrodes 4 and 6 and the workpiece 5 can be etched. The electrodes 4 and 6 are cooled by the cooling water flowing through the cooling water passages 10a and 10b, respectively, and indirectly prevent the gas introduction plate 2 and the workpiece 5 from being heated to a high temperature by the etching process.

At this time, by using bulk pyrolytic carbon as the gas introducing plate 2, even if the surface of the gas introducing plate 2 is continuously eroded by the sputtering action of the plasma, metal contamination or peeled particles on the work piece 5 is caused. The effect is that the effect of preventing pollution does not change at all.

When the diameter of the gas blowing hole 9 is selected to be 0.2 mm to 1.0 mm, strong discharge is less likely to occur in the hole portion, and the gap portion 3 is provided inside the gas introducing plate 2, and the electrode 4 is provided. The gas can be jetted with good uniformity by preliminarily diffusing the gas in the plane direction between the gas introduction plate 2 and the gas introduction plate 2 and then passing the gas through the gas blowing holes 9 provided at appropriate intervals.

Bulk pyrolyzed carbon is used as the material of the gas introduction plate 2, and the as-deposited surface (as
When the depo surface (final surface of the grown bulk) is used without processing, it has better corrosion resistance than quartz, alumite (aluminum anodized film), and general graphite. For example, SiO ₂ Since the etching rate of plasma of a fluorine-based gas such as CF ₄ or CHF ₃ used when etching the film is low, uniform etching can be performed for a long period of time.

The distance of the gap portion 3 (d in the figure) is set so that the gas diffusion in the direction of the electrode surface is higher than the speed at which the gas is introduced between the electrode 4 and the electrode 6 through the gas blowing hole 9. It has an appropriate thickness so that it is sufficiently fast. For example, the diameter of the gas blowing hole 9 is 0.5 mm, and 15,000 holes / m
^When provided at a density of ² (corresponding to 260 in a circle having a diameter of 145 mm), d is preferably about 2 mm. Further, the thickness of the gas introduction plate 2 (the portion provided with the gas blowing hole 9) is 3
It is desirable to set it to mm or more. With this thickness, there is little power loss, and even if the thickness is reduced, it is sputtered, and even if the thickness decreases, there is a thickness that can sufficiently conduct heat in the direction parallel to the electrode surface, so it is stable for a long time. It is possible to obtain the specified etching characteristics.

Although the electrode 4 on the gas introduction side is grounded in the above embodiment, the electrode 6 side on which the workpiece 5 is mounted may be grounded. Further, the workpiece 5 may be supported on the lower surface of the upper electrode, and the gas may be introduced from the upper surface of the lower electrode.

Further, the electrical and thermal contact between the outer periphery of the gas introduction plate 2 and the electrode 4 is such that the thick annular step 2a formed on the outer periphery of the gas introduction plate 2 and the electrode 4 are brought into contact with each other. Besides, as shown in FIG. 4, a structure in which a metal ring 12 of aluminum, copper, or the like is interposed may be used.

[0025]

As described above, according to the present invention, even if the gas introduction plate is sputtered by plasma and corroded for a long period of time, and the thickness thereof is reduced, metal or peeled particles remain on the work piece. It is possible to obtain good etching uniformity and repetitive etching reproducibility without causing contamination due to the like. In a narrow gap type etching apparatus with a small electrode spacing, the etching characteristics of the work piece are particularly susceptible to the surface temperature of the electrode facing the supported electrode of the work piece. Since the surface temperature of the introduction plate can be made uniform, there is an effect that uniform etching can be performed.

[Brief description of drawings]

FIG. 1 is a diagram showing a basic configuration of the present invention.

FIG. 2 is a diagram showing a crystal structure of bulk pyrolytic carbon.

FIG. 3 is a vertical sectional view of an embodiment of the present invention.

FIG. 4 is a partial cross-sectional view of another embodiment of the present invention.

[Explanation of symbols]

 1 Gas Pipe 2 Gas Inlet Plate 3 Gap 4, 6 Electrode 5 Workpiece 7 High Frequency Power Supply 8 c-axis Direction of Bulk Pyrolytic Carbon 9 Gas Blowout Holes 10a, 10b Cooling Water Channel 11 Processing Tank 12 Metal Ring

Claims (1)

[Claims] 1. A gas is introduced between a support electrode supporting a workpiece and a counter electrode facing the support electrode, and high-frequency power is supplied between the electrodes to generate plasma, In a plasma etching apparatus for etching a work piece, the surface of the counter electrode facing the support electrode is c
A gas introduction plate made of bulk pyrolytic carbon with its axis perpendicular to the surface is installed with a gap between it and the counter electrode, and the outer periphery of the gas introduction plate is electrically and thermally connected to the counter electrode. The plasma etching apparatus is characterized in that the gas introduction plate is provided with a gas blowing hole communicating with the gap while being in contact with the gas introduction plate.