JP7172717B2 - Electrode plate for plasma processing equipment - Google Patents

Description

TECHNICAL FIELD The present invention relates to an electrode plate for a plasma processing apparatus that discharges while passing a plasma generating gas in the thickness direction.

2. Description of the Related Art A plasma processing apparatus such as a plasma etching apparatus or a plasma CVD apparatus used in a semiconductor device manufacturing process has a configuration in which a pair of electrodes connected to a high frequency power supply are vertically opposed in a vacuum chamber. In this configuration, the substrate to be processed is placed on the lower electrode, and a high-frequency voltage is applied between the upper and lower electrodes while the plasma generation gas is circulated toward the substrate to be processed through a plurality of ventilation holes formed in the upper electrode. By applying the voltage to generate plasma, the substrate to be processed is subjected to processing such as etching.

As an upper electrode used in such a plasma processing apparatus, an electrode plate made of silicon and having a plurality of vent holes of the same diameter is generally used. A cooling plate is fixed on the opposite side (rear side) of the electrode plate to the side exposed to the plasma in order to release the heat that rises during plasma processing.
In this electrode plate, when the plasma treatment is performed for a long time, the by-products of the plasma reaction adhere to the surface as solid matter (this adherent matter is referred to as deposit matter). There is a demand for an electrode plate that suppresses the generation of particles, since they may adhere to the substrate to be processed and cause defects.

Patent document 1 or patent document 2 discloses an electrode plate that suppresses the generation of such particles.
In Patent Document 1, based on the recognition that particles are generated from the contact portion between the support protrusion of the shield support electrode that supports the silicon electrode plate and the silicon electrode plate, a mirror surface with a center line surface roughness Ra of 1 μm or less is disclosed. In the disk-shaped silicon electrode plate having the above, at least the portion covered with the upper surface of the support portion of the shield support electrode has a center line surface roughness Ra of more than 1 μm to 1.6 μm.
In Patent Document 2, based on the recognition that deposits adhering to the inner surface of the ventilation hole through which the etching gas flows fall off and become particles, the inner wall surface of the ventilation hole (through pore) is treated as a surface with a large surface roughness. The rough surface portion is formed on the inner wall surface of the ventilation hole on the etching gas inflow side, and the smooth portion is formed on the etching gas outflow side of the ventilation hole. Formation on the side inner wall surface is described. In Patent Literature 2, a deposit is attached to the rough surface portion so as not to fall off.

JP 2008-85027 A JP 2006-196491 A

The technique described in Patent Document 1 attempts to eliminate the source of particle generation, and although it is effective in itself, it cannot completely eliminate the generation of particles. On the other hand, the technique described in Patent Document 2 is intended to prevent particles from scattering by causing deposits that cause particles to adhere to the inner surface of the ventilation hole on the back side (opposite side to the plasma surface). The pores have a diameter of 0.5 mm, for example, and have a small inner surface area, which limits the amount of deposits that can be adhered and fixed.

SUMMARY OF THE INVENTION It is an object of the present invention to provide an electrode plate for a plasma processing apparatus that can efficiently trap deposits generated during plasma processing and prevent the generation of particles. With the goal.

An electrode plate for a plasma processing apparatus according to the present invention is an electrode plate for a plasma processing apparatus, the outer peripheral region of one side of which is supported and fixed to a plasma processing apparatus by a ring-shaped shield supporting electrode, wherein the one side is attached to the shield supporting electrode. Between the inner peripheral edge of the covered outer peripheral area and the outer peripheral edge of the vent hole forming area in which a large number of vent holes are formed, the center line average roughness Ra is 0.5 μm or more and 20 μm larger than the vent hole forming area. An annular region is provided along the radial direction and the circumferential direction and is exposed to the plasma processing space .

The outer side of the vent hole forming region is less affected by plasma and less affected by the flow of plasma gas, so deposits tend to adhere. For this reason, by providing an annular region having a large center line average roughness Ra outside the air hole formation region, the shape is such that deposits can easily adhere and are less likely to come off. In this case, if the center line average roughness Ra is less than 0.5 μm, the attached deposits are likely to fall off, and if the surface is rough enough to exceed 20 μm, particles may be generated due to plasma wear. be.

In this electrode plate for a plasma processing apparatus, the distance from the outer peripheral edge of the vent hole formation region to the inner peripheral edge of the annular region is preferably 3 mm or more. If the inner peripheral edge of the annular region is too close to the outer peripheral edge of the vent hole formation region, there is a risk that the adhered deposits will be caught in the plasma gas from the vent hole and fall off. For this reason, it is preferable that the annular region is separated from the outer peripheral edge of the vent forming region by 3 mm or more.

Moreover, it is preferable that the radial width of the annular region is 5 mm or more. The larger the area of the region where the deposition material is attached, the better, and it is preferably formed with a width of 5 mm or more.

Furthermore, the center line average roughness of the vent hole formation region is preferably less than 0.5 μm, and when formed on a smooth surface, the occurrence of defects such as abnormal discharge is prevented, and the generation of particles is also suppressed. .

According to the present invention, it is possible to efficiently capture deposits generated during plasma processing and prevent the generation of particles.

1 is a plan view showing one embodiment of an electrode plate for a plasma processing apparatus according to the present invention; FIG. 2 is a vertical cross-sectional view of the electrode plate for the plasma processing apparatus of FIG. 1 supported by a shield support electrode; FIG. It is process drawing which shows the example of the manufacturing method of the electrode plate for plasma processing apparatuses.

As shown in FIG. 1, an electrode plate for a plasma processing apparatus (hereinafter simply referred to as an electrode plate) 10 is formed in a disc shape and has a large number of vent holes 11 penetrating in the thickness direction in the central portion thereof excluding the outer peripheral portion. have.
This electrode plate 10 is a disk having a thickness of 8 to 12 mm and a diameter of 200 to 600 mm. The inner diameter of each ventilation hole 11 is 0.5 to 1.0 mm, and the center-to-center distance between the ventilation holes 11 is 5 to 10 mm.
This vent hole 11 is formed in a circular area in the central portion of the electrode plate 10 excluding the outer peripheral portion. This air hole forming region has a diameter of about 199 to 330 mm. 2, the outer peripheral portion of the electrode plate 10 is fixed to a plasma processing apparatus (not shown) by a ring-shaped shield support electrode 20. As shown in FIG. The shield support electrode 20 has a shape in which a cylindrical portion 21 and a support portion 22 extending radially inward from the lower end of the cylindrical portion 21 in an inward flange shape are integrally formed. The outer peripheral portion of the electrode plate 10 is placed on the upper surface of the support portion 22 of the shield support electrode 21, and is supported inside the inner peripheral edge of the support portion 22 with the ventilation holes 11 open.

In this case, if the circular area in which the vent hole 11 is formed in the electrode plate 10 is defined as the vent hole forming area A1, the vent hole is spaced radially inward from the inner peripheral edge of the support portion 22 of the shield support electrode 20 . An outer peripheral edge of the formation area A1 is arranged. The vent hole forming area A1 is formed to have a center line average roughness Ra of less than 0.5 μm in a range slightly radially outward from the outer peripheral edge. This Ra is less than 0.5 μm is defined as a smooth area A2.

On the other hand, the annular region A3 formed between the outer peripheral edge of the smooth region A2 and the inner peripheral edge of the support portion 22 of the shield support electrode 20 has a center line average roughness Ra of 0.5 μm or more and 20.0 μm or less. be. The annular region A3 is an outer region slightly spaced from the outer peripheral edge of the vent forming region A1, specifically, the region from the outer peripheral edge of the smooth region A2 to the inner peripheral edge of the support portion 22 of the shield support electrode 20. is. The distance L from the outer peripheral edge of the vent hole forming area A1 to the inner peripheral edge of the annular area A3 (the outer peripheral edge of the smooth area A2) is 3 mm or more, and the radial width W of the annular area A3 is 5 mm or more.
Further, when the outer peripheral portion of the electrode plate 10 covered with the support portion 22 of the shield supporting electrode 20 is defined as the outer peripheral region A4, the center line average roughness Ra is formed to be more than 1.0 μm and 1.6 μm or less. be.

The inner surface of the vent hole 11 may have a uniform surface roughness over the entire length within a range of, for example, a center line average roughness Ra of less than 0.5 μm. Different surface roughness may be set on the surface side (back surface 10b side). For example, the plasma surface 10a side may be a smooth surface with a center line average roughness Ra of less than 0.5 μm, and the back surface 10b side may be a center line average roughness Ra of 0.5 μm or more and 20 μm or less. When the smooth surface is provided, the length of the smooth surface should be 1/3 or more and 2/3 or less of the thickness of the entire electrode plate 10 .

As shown in FIG. 3, the electrode plate 10 configured in this manner is produced by an ingot forming step (S1) of forming a silicon ingot of single crystal silicon, and slicing the silicon ingot to form a disk-shaped base plate. a slicing step (S2), a heat treatment step (S3) in which the base plate is heat-treated, a vent hole forming step (S4) in which vent holes are formed in the base plate, and an etching process on the perforated base plate in which the vent holes are formed a polishing step (S6) of polishing the upper and lower surfaces of the perforated base plate after the etching process; and an outer peripheral portion (annular region A3 and a roughening step (S7) of roughening the outer peripheral region A4).

Among these processes, in the vent hole forming process, each vent hole 11 is formed while descending a drill parallel to the thickness direction from one surface of the base plate. is different between the plasma surface 10a side and the back surface 10b side, the surface roughness of the machined surface is adjusted by changing the machining speed of the drill, for example. A smooth surface is obtained when the machining speed is slower than fast.
Also, in the etching process, damaged portions (such as microcracks) on the surface caused by the slicing process and the vent hole forming process are removed by etching. As an etchant, hydrofluoric nitric acid, which is a mixture of hydrofluoric acid (HF), nitric acid (HNO ₃ ), and acetic acid (CH ₃ COOH), is used.

In the polishing step, the base plate is placed on a rotating polishing pad and polished while supplying a slurry containing an abrasive such as diamond abrasive grains. In this polishing process, the surface of the base plate is formed to have a center line average roughness Ra of less than 0.5 μm.
Next, in the surface roughening step, on one side (plasma surface 10a) of the base plate, except for a region (smoothed region A2) slightly radially outward from the outer peripheral edge of the vent hole forming region, the outer portion is The surface is roughened by grinding. In this case, the grinding speed or the like is changed so that the annular region A3 and the outer peripheral region A4 outside thereof have the aforementioned surface roughness ranges. Instead of grinding, the surface may be roughened by blasting or the like. Also in the case of blasting, the diameter of the blast particles is changed between the annular area A3 and the outer peripheral area A4.

Finally, the electrode plate 10 manufactured in this manner is washed before use.
When the electrode plate 10 is installed in the plasma processing apparatus, its inner surface is exposed to the plasma processing space while its outer peripheral portion is covered with the support portion 22 of the shield support electrode 20 . On this exposed surface (plasma surface 10a), the vent forming region A1 is exposed to the plasma environment. Since the vent hole formation region A1 is formed on a smooth surface having a center line average roughness Ra of less than 0.5 μm, problems such as abnormal discharge are prevented from occurring, and particles are generated from this smooth surface. is also suppressed.

On the other hand, the annular area A3 is exposed to the plasma environment side, but is less affected by the plasma because it is outside the air vent formation area A1. For this reason, if the plasma treatment is continued, as indicated by the chain double-dashed line in FIG. 2, the ventilation hole forming area A1 is mainly worn, and the outer annular area A3 is little worn. Therefore, deposits are likely to adhere to this annular region A3. In addition, the annular region A3 is separated from the outer peripheral edge of the vent hole forming region A1 in the surface direction of the electrode plate 10, and the difference in level with the surface of the support portion 22 of the shield support electrode 20 makes it difficult for the plasma gas to flow around. It is also less susceptible to the flow of plasma gas flowing out from the outlet of the ventilation hole 11 .

Therefore, the central line average roughness Ra of the annular region A3 is set to 0.5 μm or more and 20.0 μm or less, which is larger than that of the vent hole forming region A1, so that the deposits are firmly adhered and are difficult to fall off. In this case, if the center line average roughness Ra is less than 0.5 μm, the attached deposits are likely to fall off, and if the surface is rough enough to exceed 20 μm, plasma wear will conversely cause particle generation. There is a risk.

However, if the inner peripheral edge of the annular area A3 is too close to the outer peripheral edge of the vent hole formation area A1, there is a risk that the adhered deposits will be caught in the plasma gas from the vent hole 11 and fall off. It is preferable that the distance L from the outer peripheral edge of the pore forming region A1 is 3 mm or more. Further, if the radial width W of the annular region A3 is 5 mm or more, a large area can be secured as the region for depositing the deposit.
By forming such an annular region A3, even if the plasma processing is performed for a long time, the adhered deposits can be prevented from coming off, the generation of particles can be suppressed, and the plasma processing can be performed stably and with high quality. be able to.

The present invention is not limited to the configurations of the above-described embodiments, and various modifications can be made to the detailed configurations without departing from the gist of the present invention.
For example, the surface roughness of the inner peripheral surface of the vent hole 11 is formed to be different between the plasma surface 10a side and the back surface 10b side. It may be a smooth surface over the entire length.

A single-crystal silicon ingot with a diameter of 300 mm was prepared, and this ingot was sliced into 10-mm thick single-crystal silicon disks with a diamond band saw. : 0.5 mm perforated to form a rough surface portion with a surface roughness Ra of 10 μm, and then from the opposite side of the single crystal silicon plate in which the hole was made in this rough surface portion, a diamond drill was used to change the processing speed to obtain a diameter : A hole of 0.5 mm is made to have a smooth surface portion with a surface roughness Ra of 0.3 μm, so that the inner surface of the vent hole has a rough surface portion over a length of 1/2 at a ratio to the thickness of the electrode plate. An electrode plate was produced. The air hole formation area A1 had a diameter of 199 mm, and the center-to-center distance of the air holes was 7 mm.

Subsequently, the entire surface of the electrode plate 10 was subjected to surface polishing so as to have the center line average roughness Ra shown in the air hole formation region A1 in Table 1.
Further, by grinding the annular region A3 outside the vent hole formation region A1 by a predetermined distance and the outer peripheral region A4 in contact with the upper surface of the support portion 22 of the shield support electrode 20 of the plasma processing apparatus, the center shown in Table 1 A rough surface having a line average roughness Ra was formed. The outer peripheral region A4 had a surface roughness Ra of 1.3 μm common to all electrode plates. For the annular region A3, the distance L from the outer peripheral edge of the vent hole forming region A1 and its width (the width from the inner peripheral edge of the support portion 22 of the shield support electrode 20) W are roughened so as to have the dimensions shown in Table 1. formed the surface.

The prepared electrode plate 10 is set on the upper surface of the support portion 22 of the shield support electrode 20, and a silicon wafer is placed as a substrate to be processed,
Chamber pressure: 10 ^-1 Torr
Etching gas composition: 90 sccm CHF ₃ +4 sccm O ₂ +150 sccm He
RF power: 2kW
Frequency: 20kHz
Plasma etching was performed for 500 hours under the conditions of . Note that sccm is an abbreviation for standard cc/min, and refers to the flow rate (cc) per minute normalized at a constant temperature such as 0°C or 25°C at 1 atm (atmospheric pressure 1013 Pa).

The number of particles on the silicon wafer was measured after 200 hours, 300 hours, 400 hours and 500 hours from the start of etching, and the results are shown in the table. The number of particles is measured by scanning the wafer surface with a laser beam using a particle counter (WM-3000) manufactured by Topcon Co., Ltd., and measuring the light scattering intensity from the adhering particles to determine the position and size of the particles. by recognizing the
Table 1 shows the results.

As can be seen from the results in Table 1, between the inner peripheral edge of the outer peripheral portion covered with the shield supporting electrode and the outer peripheral edge of the air hole forming region, the center line average roughness Ra was 0.00% larger than that of the air hole forming region. Particle generation is suppressed when the annular region of 5 μm or more and 20 μm or less is provided along the circumferential direction.
On the other hand, in Comparative Example 1 in which the central line average roughness Ra of the annular region and the vent hole forming region is the same and is Ra 5 μm, the vent hole forming region is worn by the plasma, and the Ra is 0.3 μm. In Comparative Example 2, a large number of particles are generated because deposits are less likely to adhere to the annular region and more likely to fall off.
In addition, in Example 4, in which the distance between the annular region and the vent hole forming region is less than 3 mm, the deposition material adhering to the annular region is caught in the gas flow from the vent hole and falls off, so the deposit is in the initial stage of etching. However, after a long time, particles are more likely to be generated than in Example 2.
In Example 5, in which the center line average roughness Ra of the vent hole forming region is 0.5 μm or more, abnormal discharge is likely to occur, and thus particles are more likely to be generated than in Example 2.
In Example 6, in which the width of the annular region is less than 5 mm, few particles are generated in the initial stage of etching, but since the area to which the deposited material can adhere is small, after a long period of time, compared to Example 2, Particles are generated a little more easily.

10 plasma processing apparatus electrode plate 11 vent hole 20 shield support electrode 22 support part A1 vent hole forming area A2 smooth area A3 annular area A4 outer peripheral area (peripheral part)

Claims (4)

An electrode plate for a plasma processing apparatus having an outer peripheral region on one side supported and fixed to a plasma processing device by a ring-shaped shield supporting electrode, wherein the one side includes an inner peripheral edge of the outer peripheral region covered with the shield supporting electrode and a plurality of and an annular region exposed to the plasma processing space and having a central line average roughness Ra greater than that of the vent hole forming region and being 0.5 μm or more and 20 μm or less. are provided along the radial direction and the circumferential direction. 2. The electrode plate for a plasma processing apparatus according to claim 1, wherein the distance from the outer peripheral edge of said vent hole forming area to the inner peripheral edge of said annular area is 3 mm or more. 3. The electrode plate for a plasma processing apparatus according to claim 1, wherein said annular region has a radial width of 5 mm or more. 4. The electrode plate for a plasma processing apparatus according to any one of claims 1 to 3, wherein the central line average roughness of said vent hole forming region is less than 0.5 [mu]m.

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