JP2000212778A - Silicon electrode for plasma etching - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a silicon electrode for plasma etching excellent in economicity and capable of stably preventing the contamination of a wafer over a long period. SOLUTION: A silicon electrode is divided into an electrode body 10 composed of a silicon sheet and an annular supporting member 20 supporting the electrode body 10 and fitted to an etching device, and they are made mechanically attachable and detachable. The annular supporting member 20 is formed of glassy carbon-impregnated graphite. Although the annular member 20 is composed of inexpensive graphite having high strength, the contamination of a wafer caused by the dropping of carbon particles can stably be prevented over a long period.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a silicon electrode used in a plasma etching apparatus, and more particularly, to a silicon electrode used in a plasma etching apparatus.
The present invention relates to a composite silicon electrode divided into an electrode body that is consumed by etching and an annular support member that supports the electrode body and is attached to an etching apparatus.

[0002]

2. Description of the Related Art As an etching apparatus used for etching a semiconductor wafer, there is a parallel plate type plasma etching apparatus. In this etching apparatus, a semiconductor wafer is placed on a lower electrode also serving as a base, the wafer is opposed to the upper electrode from below, and an etching gas is supplied to the wafer through a large number of through-holes provided in the upper electrode. By applying a high-frequency voltage between the lower electrode and the upper electrode, the etching gas is turned into plasma,
The upper surface of the wafer is etched by the plasma gas.

Here, carbon is used as the upper electrode. However, in the case of a carbon electrode, there are problems of wafer contamination and poor etching due to carbon particles and impurities contained in the electrode material. To solve this problem, an electrode made of silicon is disclosed in
No. 936.

[0004] The silicon electrode has the advantages that it has less problems of wafer contamination and poor etching than the carbon electrode, and that the electrode itself is less consumed by etching. However, one of the advantages is that silicon is a hard and brittle metal, which tends to cause cracks due to mechanical stress during installation and thermal stress during use. It is not as long as expected.

In order to solve this drawback, a disk-shaped electrode body which consumes a silicon electrode by etching and an annular support member which supports the electrode body and is attached to an etching apparatus are divided into two parts. The applicant has developed a split-type composite silicon electrode which is mechanically detachable by a body (screw) (Japanese Patent Application Laid-Open No. Hei 8-27406).
No. 8).

Further, from the viewpoint of preventing wafer contamination and defective etching, which are problems with carbon electrodes, an integrated composite silicon electrode obtained by brazing an electrode body made of a silicon plate to an annular support member also made of silicon. Is proposed in Japanese Patent Application Laid-Open No. 9-321027.

[0007]

However, these composite silicon electrodes still have the following problems.

Since the silicon electrode is divided into a disk-shaped electrode main body and an annular support member, stress concentration in the electrode main body is reduced, thereby preventing cracking. Also,
The fabrication process is easier than the integrated silicon electrode. However, since the electrode body and the support member are both made of silicon, they are still expensive.

There is a risk that the silicon support member will break when it is attached to the etching apparatus.

When the means for fixing the electrode body to the support member is a screw member made of silicon, it is difficult to machine the screw member and it is difficult to machine a screw hole in the support member. For this reason, these processes take a lot of cost,
From this point, economic efficiency is also deteriorated. In addition, there is a possibility that cracks or chips may occur during fixing.

If the means for fixing the electrode body to the support member is brazing, cracks may occur in silicon due to the difference in heat conduction between silicon and the brazing material. The brazing material may cause wafer contamination.

[0012] Damage to silicon causes a reduction in the service life of the electrode and an increase in electrode cost.

In order to solve these problems in the composite silicon electrode, it is conceivable that the support member is made of carbon.

In the case where the electrode body is made of silicon and the support member is a composite silicon electrode made of carbon, breakage of the support member is effectively prevented. Furthermore, it is possible to form a screw hole in the support member, and as a result, the electrode body is detachably fixed to the support member by screwing, and the electrode body can be replaced. Moreover, according to the screwing, stress concentration in the electrode body is reduced, and damage to the electrode body is also effectively prevented. Therefore, the service life is greatly extended as compared with the integrated silicon electrode. Further, since the amount of expensive silicon used is reduced, the economic efficiency is improved in terms of material costs.

However, when an abnormal discharge occurs between the electrode body and the support member when the glow discharge occurs, carbon particles are generated from the support member by sputtering. The carbon particles fall on the wafer through a large number of through-holes provided in the electrode body, contaminate the wafer, and reduce the yield of integrated circuits on the wafer.
The contamination by the carbon particles is caused by the SiO 2 on the surface of the wafer.
_This is particularly serious when plasma etching is performed on ₂ or the like. This is because when etching SiO ₂ , plasma using fluorine gas as a substrate is generally used. However, in plasma using fluorine gas as a substrate, carbon particles scraped off from a supporting member are not volatilized and fall directly onto a wafer. This is because they remain as particles.

In order to prevent the carbon particles from dropping from the support member, it is conceivable to coat the surface of the support member with a ceramic or the like. It is difficult to prevent.

An object of the present invention is to provide excellent economical efficiency and
It is an object of the present invention to provide a plasma etching silicon electrode capable of stably preventing contamination due to a drop of carbon particles from a support member for a long period of time.

[0018]

In order to achieve the above object, a silicon electrode for plasma etching according to the present invention mechanically comprises an electrode body made of a silicon plate and an annular support member for supporting the electrode body. In a detachable composite type silicon electrode for plasma etching, a supporting member is formed of glassy carbon impregnated graphite.

The glassy carbon-impregnated graphite is obtained by impregnating a carbon-containing thermosetting resin (glassy carbon) into a graphite substrate, heat-treating it at a high temperature, and calcining and carbonizing the graphite substrate. The surface is further coated with the above resin, and heat-treated at a high temperature to be calcined and carbonized. The area impregnated with the resin is several mm (usually 5 to 6 mm) from the surface of the graphite substrate, and the coating thickness when coating is performed is 5 mm.
It is about μm. This processing itself is known as, for example, a glass coat (trade name).

Since the glass surface of this glassy carbon impregnated graphite is dense, the generation of carbon particle dust from the surface is extremely small, and the gas reactivity is also extremely low.
For this reason, the falling of the carbon particles from the support member is prevented. Further, since not only the surface but also the inside of the graphite is densified, even if it is repeatedly used, the drop does not occur again. Therefore, contamination due to the drop of the carbon particles from the support member can be stably prevented for a long time.

[0021] Glassy carbon impregnated graphite is also inexpensive and has high strength compared to silicon. For this reason, breakage of the support member is effectively prevented. Further, precision machining such as a screw hole for the support member is possible, and as a result, the electrode body is detachably fixed to the support member by screwing or the like,
The exchange becomes possible. In addition, the screwing or the like alleviates stress concentration in the electrode main body, and effectively prevents damage to the electrode main body. Therefore, economical efficiency is remarkably improved in terms of both material cost and service life.

Preferably, a conductive film is interposed between the electrode body and the support member. This film improves the adhesion between the electrode body and the support member, improves thermal conductivity and electric conductivity, and functions as a buffer when a force is applied to the electrode body and the support member. Aluminum, tantalum, molybdenum, gold,
Silver is preferred.

As means for fixing the electrode body to the support member, it is preferable to use a coupling jig such as a screw. A coupling jig such as a screw facilitates partial replacement of the electrode body and the support member, and also effectively reduces stress concentration in the electrode body. As a material of the coupling jig, a resin that does not cause contamination, such as a fluorine resin having excellent chemical resistance and a polyimide resin having excellent heat resistance, is preferable, and glassy carbon impregnated graphite is also preferable. These are easy to process into screw members.

[0024]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a front view of a silicon electrode for plasma etching according to an embodiment of the present invention, FIG. 2 is a longitudinal sectional view of the silicon electrode, FIG. 3 is an exploded longitudinal sectional view of the silicon electrode, and FIG. It is a longitudinal cross-sectional view of the connection part of a main body and a support member.

The silicon electrode of this embodiment is used as an upper electrode of a plasma etching apparatus. The silicon electrode includes a disk-shaped electrode body 10 and a ring-shaped support member 20 that supports the electrode body 10.
Are fixed to the support member 20 via a conductive film 40 by a plurality of screws 30 as a connecting jig.

The electrode body 10 is a thin plate made of single crystal silicon or polycrystalline silicon by a known method. A large number of through-pores 11, 11... For allowing an etching gas to pass therethrough are formed in portions other than the outer peripheral portion of the electrode body 10.
Are formed. A screw 3 is provided on the outer periphery of the electrode body 10.
A plurality of through-holes 12, 12,.
Are formed at equal intervals in the circumferential direction.

The support member 20 is made of glassy carbon-impregnated graphite obtained by impregnating a graphite base with glassy carbon. The support member 20 includes a ring portion 21 that supports the outer peripheral portion of the electrode body 10, and a flange portion 22 that protrudes outward from the rear end of the ring portion 21. On the tip surface of the ring portion 21,
A plurality of screw holes 23 into which the plurality of screws 30 are screwed are formed at equal intervals in the circumferential direction. The flange portion 22 is a projection for attaching the silicon electrode to the plasma etching device.

The screws 30, 30,... Are made of a resin (for example, a fluorine resin or a polyimide resin) or a graphite impregnated with glassy carbon which does not have a risk of contaminating the wafer.

The method of assembling the silicon electrode of the present embodiment having the above-described configuration is as follows.

A conductive film 40 made of aluminum or the like is attached to the end surface of the supporting member 20 with which the electrode body 10 contacts. The electrode body 10 is brought into contact with the distal end surface of the support member 20 via the conductive film 40. The screws 30 are passed through the through holes 12 of the electrode body 10 and screwed into the screw holes 23 of the support member 20, respectively. Thereby, the electrode main body 10 is attached to the distal end surface of the support member 20. In order to improve the airtightness of the attachment portion, a resin tape 50 is attached to the outer peripheral surfaces of the electrode body 10 and the support member 20 so as to straddle both of them.

The silicon electrode assembled in this manner is mounted on a plasma etching apparatus as an upper electrode. The characteristics of this silicon electrode are as follows.

Since the support member 20 is made of graphite impregnated with glassy carbon, the generation of carbon particles from the support member 20 is slight. Therefore, the contamination of the wafer due to the drop of the carbon particles is prevented. Since glassy carbon is not merely a coating but is impregnated in carbon, wafer contamination due to falling of carbon particles from the support member 20 can be stably prevented for a long period of time.

Since the screws 30, 30,... Are made of resin or graphite impregnated with glassy carbon, wafer contamination due to this is also prevented.

Since the support member 20 is made of glassy carbon-impregnated graphite, the material cost is lower than that of a silicon support member.

Since the screws 30, 30,... Are made of resin or graphite impregnated with glassy carbon, their fabrication is easy and the cost is low. Since the support member 20 is made of the graphite impregnated with glassy carbon, the screw holes 23, 23,...

Since the support member 20 is made of graphite impregnated with glassy carbon, there is no possibility that the support member 20 will be damaged when the support member 20 is fixed to the etching apparatus.

The support member 20 is made of graphite impregnated with vitreous carbon, and the screws 30, 30,... Are made of resin or graphite impregnated with glassy carbon. Does not occur.

As described above, the silicon electrode of this embodiment can stably prevent wafer contamination due to the drop of carbon particles from the support member 20 for a long period of time, and is low in material cost and manufacturing / processing cost. As it can be used for a long time without chipping and has a long service life,
Extremely economical.

The silicon electrode of this embodiment was actually manufactured and used for a plasma etching apparatus. When fixing the electrode main body 10 to the support member 20, any of them could be easily joined without cracking. The assembled silicon electrode was set in a plasma etching apparatus, and plasma etching was performed on 10,000 silicon wafers having an SiO ₂ layer. The number of particles on the wafer surface was examined. Eyes, 100
No particles were observed on any of the 00 wafers.

When the support member 20 is made of silicon and brazed using the electrode body 10 made of silicon and a brazing material of iridium, cracks are formed in the silicon due to the difference in thermal conductivity between silicon and iridium during brazing. Sometimes entered. The silicon electrode without cracks was set in a plasma etching apparatus, plasma etching was performed on 10,000 silicon wafers having an SiO ₂ layer, and the number of particles on the wafer surface was examined. Not recognized, but 1000th, 5000th, 100th
On each of the 00 wafers, there were 15 particles / sheet each of which appeared to have been etched with Jedium.
88 / sheet and 361 / sheet were observed.

When the support member 20 was made of silicon and the attempt was made to join the electrode body 10 made of silicon and a screw member made of silicon, this joining could not be performed because the silicon member was cracked.

FIG. 5 is a longitudinal sectional view of a main part of a silicon electrode for plasma etching according to another embodiment of the present invention.
Is a perspective view of the main part.

In the silicon electrode of the present embodiment, the protrusions 14 are provided at a plurality of positions on the outer peripheral surface of the disk-shaped electrode body 10 made of silicon. A concave portion 24 into which the convex portion 14 of the electrode body 10 fits is provided on the inner peripheral surface of the ring-shaped support member 20 made of graphite impregnated with glassy carbon. Recess 2
4 is bent in a reverse L-shape when viewed from the inside of the support member 20, and the lower end thereof is open to the lower surface of the support member 20.

In order to fix the electrode body 10 to the support member 20, after inserting each protrusion 14 of the electrode body 10 into each recess 24 of the support member 20 from below, the electrode body 10 is slightly rotated in the circumferential direction. Thereby, the electrode body 10 and the support member 2
0 is fixedly connected without using a connecting jig. Also in this case, it is possible to interpose a conductive film at the joint.

The silicon electrode according to the present embodiment is also
Since 0 is made of glassy carbon-impregnated graphite, it is economically excellent similarly to the above-mentioned silicon electrode, and can stably prevent contamination due to the drop of carbon particles from the support member 20 for a long time.

[0046]

As described above, the silicon electrode for plasma etching of the present invention is a composite type silicon electrode for plasma etching divided into an electrode body made of a silicon plate and an annular support member for fixing the electrode body. Since the support member is formed of glassy carbon impregnated graphite, it is economical and can stably prevent contamination due to the drop of carbon particles from the support member for a long period of time.

[Brief description of the drawings]

FIG. 1 is a front view of a silicon electrode according to an embodiment of the present invention.

FIG. 2 is a vertical sectional view of the silicon electrode.

FIG. 3 is an exploded longitudinal sectional view of the silicon electrode.

FIG. 4 is a vertical cross-sectional view of a joint between an electrode body and a support member.

FIG. 5 is a longitudinal sectional view of a main part of a silicon electrode for plasma etching according to another embodiment of the present invention.

FIG. 6 is a perspective view of the main part.

[Explanation of symbols]

 Reference Signs List 10 electrode body made of silicon 20 support member made of graphite impregnated with glassy carbon 30 screw (joining jig) 40 conductive film

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 4G032 AA04 AA07 BA05 4K057 DA01 DB06 DD01 DE06 DM03 DM06 DM10 DN01 5F004 AA13 AA15 BA04 BA06 BD03 DB03 EB02

Claims (3)

[Claims] 1. A split-type composite plasma etching silicon electrode in which an electrode body made of a silicon plate and an annular support member for supporting the electrode body are mechanically detachable, wherein the support member is made of glass. A silicon electrode for plasma etching, comprising carbon-impregnated graphite. 2. The silicon electrode for plasma etching according to claim 1, wherein a conductive film is interposed between the electrode body and the support member. 3. The silicon electrode for plasma etching according to claim 1, wherein a coupling jig is used for fixing the electrode body and the support member.