JP2008311297A - Electrode plate for plasma treatment apparatus, manufacturing method thereof, and plasma treatment apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a plasma treatment apparatus for forming efficiently pores having small diameters in an electrode plate for the plasma treatment apparatus having a relatively large thickness. <P>SOLUTION: This electrode plate for the plasma treatment apparatus has a plurality of through-pores 11 in the thickness direction, wherein each through-pore 11 is composed of a drill-processed pore 21 at the side of the electrode plate from a middle point of the penetrating direction of the through-pore to one surface 3a of the plate and of a laser-processed pore 22 at the side of the electrode plate from a middle point of the penetrating direction of the through-pore to the other surface 3b of the plate. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an electrode plate for a plasma processing apparatus having a through hole through which a plasma generating gas passes, a manufacturing method thereof, and a plasma processing apparatus using the electrode plate.

  A plasma processing apparatus such as a plasma etching apparatus or a plasma CVD apparatus used in a semiconductor device manufacturing process has, for example, an electrode plate connected to a high frequency power source and a frame placed in a chamber facing each other in a vertical direction, and silicon is placed on the frame. With the wafer placed, plasma is generated by applying a high-frequency voltage from a through-hole formed in the electrode plate toward the silicon wafer, and processing such as etching is performed on the silicon wafer. ing.

The electrode plate used in the plasma processing apparatus is made of, for example, single crystal silicon as a material, and has a disk shape with an outer diameter of 300 mm and a thickness of several mm, for example. The through-holes formed in the electrode plate are, for example, those having an inner diameter of about 0.5 mm and many formed at a pitch of about 8 mm. For example, as described in Patent Documents 1 and 2, a diamond drill is used. It is generally formed by the drilling process used. Patent Document 1 discloses a drilling method by ultrasonic machining, electric discharge machining, laser machining, and the like in addition to drilling.
Japanese Patent Laid-Open No. 11-104950 JP-A-11-281307

  By the way, since the opening edge part of the through-hole in a discharge surface wears out and spreads with use of an electrode plate, the direction where it makes a through-hole as small as possible becomes long. In addition, since the entire discharge surface is consumed at the same time, it is preferable that the electrode plate is thick. In addition, the electrode plate is prevented from warping and cracking due to an increase in the diameter of the electrode plate, and the electrode plate is also used to extend the life of the electrode plate. There is an increasing demand for thicker plates.

In each of the above-described drilling processes, a relatively small diameter through hole having an inner diameter of 0.3 mm or less can be easily formed by laser processing, but there is a limit to forming it deeply. For this reason, for example, in the case of an electrode plate having a thickness of about 10 mm, a hole is formed by laser processing from one side to the middle of the thickness, and laser processing is performed from the opposite surface so as to communicate with the previously opened hole. Thus, a method of connecting the holes from both sides at the center of the thickness is considered.
However, laser processing is generally slow, and it takes a considerable amount of time for the holes from both sides to be in communication with each other, and the positional accuracy is also inferior. The problem of poor workability because it is difficult to adjust the position to match the axial centers of the holes formed from both sides, such as the need to drill holes from the other side while taking into account variations in hole positions. There is.

  The present invention has been proposed in view of the above circumstances, and an object thereof is to efficiently form a small-diameter hole in a relatively thick electrode plate.

  The electrode plate of the present invention is a plasma processing apparatus electrode plate having a plurality of through-holes in the thickness direction, and each through-hole is formed by drilling on one surface side from a midway position in the through-direction. It is a hole, and the other surface side is a laser processing hole formed by laser processing.

In other words, by using a hole in the middle of the electrode plate as a drilling hole, and making only laser drilling the remaining thickness, the burden of laser processing, which makes it difficult to form a long hole at once, is reduced. It is a shortened one. In addition, drilling has a higher processing speed and higher positioning accuracy than laser processing, and can process a large number of holes in a relatively short time with high accuracy. Therefore, when forming the laser processed hole from the opposite side of the drilled hole, there is little need to take into account variations in the positions of the drilled holes, so that positioning work during laser processing is facilitated.
In this case, the drilling hole is preferably formed to have a larger inner diameter than the laser processing hole, and the positioning of the laser processing hole can be facilitated by the larger inner diameter.

Further, in the method of manufacturing an electrode plate according to the present invention, after a hole is drilled from one surface of the electrode plate to a middle position of the thickness of the electrode plate by drilling, the bottom surface of the hole and the other surface of the electrode plate The through hole is formed by forming a hole in a through state by laser processing.
That is, the laser processing hole is formed after the drilling hole is formed first. When a hole is formed by drilling, a minute chipping may occur at the opening edge of the hole at the moment when the drill penetrates the plate. The occurrence of chipping can be reliably prevented.

Moreover, in the plasma processing apparatus using the electrode plate of the present invention, one surface of the electrode plate in which the laser processing hole is opened is a discharge surface.
The drilled hole may cause micro cracks on the inner surface due to vibration during processing, whereas the laser processed hole has a relatively smooth inner surface. For this reason, generation | occurrence | production of the particle | grains to a plasma atmosphere can be suppressed by making the opening surface of this laser processing hole into a discharge surface. Further, when the back surface of the electrode plate is fixed to the cooling plate in contact with the cooling plate, since the drilling hole with high positioning accuracy is connected to the hole of the cooling plate, the positional deviation can be prevented.
Note that the hole formed by laser processing is not limited to a circular cross section, and may have a different shape, and the ejection of the gas flow can be controlled to a desired state.

According to the electrode plate for a plasma processing apparatus of the present invention and the manufacturing method thereof, since a part of the thickness of the electrode plate is a drilling hole and the rest is a laser processing hole, the burden of laser processing can be reduced. Even a thick electrode plate can efficiently form small-diameter holes.
In addition, by setting the surface where the laser processing hole is opened as the discharge surface, the one with less damage due to processing will be opened in the discharge surface, so the generation of particles can be suppressed, and high quality Plasma treatment can be performed.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
First, a plasma etching apparatus will be described as an embodiment of a plasma processing apparatus in which this electrode plate is used.
As shown in the schematic cross-sectional view of FIG. 4, the plasma etching apparatus 1 is provided with an electrode plate 3 in the upper part of the vacuum chamber 2, and a gantry 4 that can move up and down in the lower part. Are provided in parallel. In this case, the upper electrode plate 3 is supported by an insulator 5 in an insulated state with respect to the wall of the vacuum chamber 2, and an electrostatic chuck 6 is provided on the gantry 4. A wafer 8 is placed together with a support ring 7 on the substrate. Further, an etching gas supply pipe 9 is provided in the upper part of the vacuum chamber 2, and the etching gas sent from the etching gas supply pipe 9 passes through the diffusion member 10 and then passes through the through holes 11 provided in the electrode plate 3. It is configured to flow toward the wafer 8 and be discharged to the outside from the discharge port 12 on the side of the vacuum chamber 2. On the other hand, a high frequency voltage is applied between the electrode plate 3 and the gantry 4 by a high frequency power source 13.

When an etching gas is supplied to the plasma etching apparatus 1 in a state where the high-frequency voltage is applied, the etching gas passes through the diffusion member 10, passes through the through hole 11 provided in the electrode plate 3, and the electrode plate 3 and the pedestal. 4 is discharged into a space between the two and becomes a plasma in the space, hits the wafer 8, and the surface of the wafer 8 is etched by sputtering, that is, a physical reaction by the plasma and a chemical reaction of the etching gas.
Further, for the purpose of uniformly etching the wafer 8, the generated plasma is concentrated on the central portion of the wafer 8, and is prevented from diffusing to the outer peripheral portion, thereby generating a uniform plasma between the electrode plate 3 and the wafer 8. In order to generate it, the plasma generation region 14 is normally surrounded by a shield ring 15.

The electrode plate 3 used in the plasma etching apparatus 1 is formed in a disk shape by, for example, single crystal silicon, and a large number of the through holes 11 are formed as shown in FIG.
As shown in FIG. 1B, the through hole 11 has a drilling hole 21 formed by drilling from one surface 3a of the electrode plate 3 and a laser processing formed by laser processing from the other surface 3b. The hole 22 is formed in communication with the central portion of the thickness of the electrode plate 3.
In this case, as shown in the drawing, the drilling hole 21 is formed to have a slightly larger diameter than the laser processing hole 22, and the laser processing hole 22 includes the inner bottom surface of the drilling hole 21 and the electrode plate 3. It is formed between the other surface 3b. Further, the inner surface of the laser processing hole 22 is formed to be smoother than the inner surface of the drilling hole. For example, the average roughness is Ra = 0.5 μm for the drilling hole 21 and the laser is processed. The direction of the processing hole 22 is Ra = 0.1 μm.

  The electrode plate 3 is disposed in the plasma etching apparatus 1 so that the surface 3b where the laser processing hole 22 is opened faces the gantry 4. That is, in FIG. 4, the surface 3 a where the drilling hole 21 is opened is directed upward, and the surface 3 b where the laser machining hole 22 is opened is directed to the lower frame 4. That is, the surface 3b where the laser processed hole 22 is open is the discharge surface.

Next, a method for manufacturing the electrode plate 3 will be described.
As shown in FIG. 2, a hole 21 is formed in the single crystal silicon plate formed in a disc shape from one surface 3a to a midway position of the thickness by drilling. A tool such as a carbide drill or a diamond drill is used for the drilling.
Next, as shown by a dotted line in FIG. 2, a hole 22 that communicates between the bottom surface of the drilled hole 21 and the other surface 3 b of the electrode plate 3 is formed by laser processing. As this laser, a carbon dioxide laser, a YAG laser, an excimer laser, or the like can be applied. In particular, the excimer laser can make fine holes.

In this laser processing, a through hole having a diameter of 0.3 mm can be formed by continuously irradiating a single crystal silicon plate with a laser beam of 11 J / cm ² using a YAG laser. Further, the machining time can be shortened by about 20% in the drilling process compared with the laser machining, and by using the drilling process and the laser machining together, for example, 1000 through holes are formed in an electrode plate having an outer diameter of 300 mm. In this case, the working time can be greatly reduced as compared with the case where all the through holes are opened by laser processing.

Then, the electrode plate 3 formed in this way is attached to the plasma etching apparatus 1 with the surface (discharge surface) 3b where the laser processing hole 22 is opened facing the mount 4 as described above, and plasma etching treatment is performed. Since the gas flows out from the laser processed hole 22 on the smooth surface, the generation of particles can be extremely reduced. For example, the state of particle generation when plasma etching is performed using an electrode plate having a drilling hole with the entire thickness and an electrode plate formed by continuously drilling and laser processing holes. As a result of the investigation, under the condition that the output of the high-frequency power is 2 KW, the frequency is 20 KHz, and CHF ₃ + O ₂ + He gas is used as the plasma generating gas, the former has 48 particles of 0.16 μm or more on the wafer within 100 hours from the start of etching. In contrast, the number of particles having a size of 0.16 μm or more was about 10 even after 100 hours.

  If the through-hole 11 is made small in diameter, the flow velocity is increased, so that it is easy to generate particles. However, in the case of the laser processing hole 22, the inner surface is made smooth and the generation of particles is suppressed. The diameter of the hole 22 can be reduced. In this case, since the drilling hole 21 is formed to have a relatively large diameter, the flow velocity when passing through the drilling hole 21 is reduced. Since 21 is not a penetrating through-hole, the occurrence of chipping is prevented. Therefore, the plasma etching apparatus 1 using the electrode plate 3 generates very few particles and can perform a high quality etching process.

  FIG. 3 shows an example in which the back surface of the electrode plate 3 is fixed to the cooling plate 31. The cooling plate 31 is made of a material having excellent thermal conductivity, and through holes 32 are formed at the same pitch as the electrode plate 3. Then, the cooling plate 31 and the electrode plate 3 are integrated with the through holes 32 being in communication with the through holes 11 of the electrode plate 3. In this case, the drilling hole 21 (see FIG. 1B) with good processing accuracy communicates with the through-hole 32 of the cooling plate 31, and the positional deviation between them can be effectively prevented.

  The present invention is not limited to the above-described embodiment, and various modifications can be made without departing from the spirit of the invention. For example, the dimensions of the through holes described above are examples, and the laser processing holes are not limited to a circular cross section, and may be formed in a different cross section, and the gas flow to be injected according to the cross sectional shape is in an appropriate state. It is possible to control. In addition to the plasma etching apparatus of the embodiment, the plasma processing apparatus using this electrode plate can be used for a plasma CVD apparatus or the like.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 shows an embodiment of an electrode plate of the present invention, in which (a) is an overall sectional view and (b) is an enlarged sectional view of a through hole portion. It is an expanded sectional view which shows the middle state of the punching process of the electrode plate of FIG. FIG. 2 is an overall cross-sectional view showing an example in which a cooling plate is integrated with the back surface of the electrode plate of FIG. 1. It is a schematic sectional drawing which shows the example of the plasma etching apparatus using the electrode plate of FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Plasma etching apparatus 2 Vacuum chamber 3 Electrode plate 3a One side 3b The other side (discharge surface)
DESCRIPTION OF SYMBOLS 4 Base 8 Wafer 9 Etching gas supply pipe 11 Through-hole 12 Discharge port 13 High frequency power supply 14 Plasma generation area 21 Drilling hole 22 Laser processing hole 31 Cooling plate 32 Through-hole

Claims (4)

  In the electrode plate for a plasma processing apparatus having a plurality of through holes in the thickness direction, each through hole is a drilled hole formed by drilling on one surface side from the middle position in the through direction, and the other surface An electrode plate for a plasma processing apparatus, wherein the side is a laser processing hole formed by laser processing.   The electrode plate for a plasma processing apparatus according to claim 1, wherein the drilling hole has an inner diameter larger than that of the laser processing hole.   3. A method of manufacturing an electrode plate for a plasma processing apparatus according to claim 1, wherein a hole is drilled from one surface of the electrode plate to a middle position of the thickness of the electrode plate by drilling, and then the bottom surface of the hole is formed. A method of manufacturing an electrode plate for a plasma processing apparatus, wherein the through hole is formed by forming a hole in a penetrating state between the first surface and the other surface of the electrode plate by laser processing.   The plasma processing apparatus using the electrode plate according to claim 1 or 2, wherein one surface of the electrode plate in which the laser processing hole is opened is a discharge surface.

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