JP6014994B2 - Electrode plate for plasma processing equipment - Google Patents

Description

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

  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 upper electrode and a lower electrode connected to a high-frequency power source disposed in a chamber facing each other in the vertical direction, With the substrate to be processed disposed on the electrode, plasma is generated by applying a high-frequency voltage while etching gas is circulated from the air hole formed in the upper electrode toward the substrate to be processed, and etching is performed on the substrate to be processed. And the like.

As the upper electrode used in this plasma processing apparatus, a laminated electrode plate is generally used in which a silicon electrode plate is fixed to a cooling plate and overlapped, and the heat of the electrode plate rising during the plasma processing is cooled. It is configured to dissipate heat through the plate.
The air holes (through-holes) provided in the electrode plate are usually formed in parallel to the thickness direction (see Patent Document 1). However, by repeatedly performing the plasma treatment, the portion exposed to the plasma is reduced. The diameter of the vent hole changes greatly because it is worn away. In particular, the opening facing the substrate to be processed on the plasma generation region side of the air hole is eroded. Along with this, a part of the plasma flows back against the flow of the etching gas, and when the plasma enters from the vent hole toward the back surface of the electrode plate, a part of the cooling plate is sputtered and the substrate to be processed is contaminated. There is a risk of being.

  Therefore, Patent Document 2 and Patent Document 3 propose electrode plates formed with bent air holes. In Patent Document 2, holes are formed in different directions on the front side and the back side of the electrode plate, and bent holes are formed by connecting both holes inside the electrode plate (through pores). In Patent Document 3, a gas hole member that fits tightly into the mounting hole of the electrode plate body is provided, and a vent hole (through hole) in which at least two bent portions are formed is formed in the gas hole member. ing.

In this way, when a bent portion is provided in the middle of the vent hole, it is possible to prevent plasma that flows backward against the flow of the etching gas from passing through the back surface of the electrode plate as it is, so that damage to the cooling plate can be suppressed. Has been.
In addition, the etching gas ejected from the vent hole diffuses to the surroundings while gradually decreasing the flow velocity, but the etching gas flow is inclined with respect to the thickness direction of the electrode plate so that the etching gas is uniformly distributed around the surroundings. Can be diffused.

Japanese Patent Laid-Open No. 2003-289064 Japanese Patent Laid-Open No. 2008-60197 JP 2010-103225 A

  However, when the hole located on the substrate side of the vent hole is inclined with respect to the thickness direction of the electrode plate, the flow of the etching gas ejected from the vent hole is attracted to the surface of the electrode plate. Flowing into. In this case, the etching gas cannot be supplied along the inclined hole, and it is difficult to obtain a target etching gas diffusion effect. Therefore, the density of the etching gas becomes non-uniform, and there is a possibility that uniform etching cannot be performed on the entire substrate to be processed.

  The present invention has been made in view of such circumstances, and it is possible to prevent the cooling plate from being damaged by suppressing the backflow of the plasma and to perform the in-plane uniform plasma processing on the substrate to be processed. An object of the present invention is to provide an electrode plate for a plasma processing apparatus capable of performing

The electrode plate of the present invention is an electrode plate for a plasma processing apparatus disposed opposite to a substrate to be processed in the plasma processing apparatus, and is provided with a plurality of vent holes penetrating in the thickness direction. On the discharge surface side facing the substrate to be processed, there is an inclined hole portion that is formed obliquely with respect to the thickness direction, and the discharge surface is formed with a recess that cuts off the opening end of the inclined hole portion. In the cross section along the inclination direction of the inclined hole portion, the angle formed between two peripheral edges of the inclined hole portion that are 180 ° opposite to each other and the notch surface of the concave portion that intersects the inclined hole portion is It is set to the right angle or acute angle of the same angle , The said notch surface is a plane, The opening edge part of the said inclined hole part is opening to this notch surface, It is characterized by the above-mentioned.

By forming the concave portion set as described above at the opening end portion of the inclined hole portion, the etching gas is supplied in the axial direction (inclined direction) without affecting the flow of the etching gas ejected from the vent hole. Direction). Thus, the etching gas can be ejected along a desired direction, and the etching gas can be uniformly diffused, so that the in-plane uniform plasma treatment can be performed on the substrate to be processed.
In addition, since the air holes are provided so as to be inclined with respect to the thickness direction of the electrode plate, when the recess is not formed, a part of the inner peripheral surface of the inclined hole is formed in the plasma generation region at the opening end. There is a possibility that a phenomenon occurs in which the plasma is reflected on the inner peripheral surface thereof and flows backward against the flow of the etching gas. However, by providing a recess at the opening end, a part of the inner peripheral surface of the inclined hole is cut out, so that the surface facing the plasma generation region is reduced and the plasma is reflected on the inner peripheral surface of the inclined hole. Thus, it is possible to prevent the air from entering the vent hole. Therefore, the back flow of plasma can be suppressed and damage to the cooling plate due to plasma can be prevented.

In addition, since the opening end of the inclined hole portion is opened in the flat cut-out surface, the etching gas can be reliably flowed along the axial direction of the inclined hole portion, so that the etching gas can be diffused smoothly. Can do. Further, in this case, since the concave portion is formed by cutting out with a flat surface, the processing is easy.

In the electrode plate of the present invention, the vent hole has an inlet side hole portion formed from the opposite surface located on the opposite side of the discharge surface to the middle of the thickness direction toward the discharge surface. It is preferable that the portion and the inclined hole portion are bent and provided by communicating with each other.
By providing a vent hole that is bent halfway in the thickness direction of the electrode plate, even if the plasma enters the inclined hole portion and flows back against the flow of the etching gas, the plasma passes through the back surface of the electrode plate as it is. This can prevent the damage to the cooling plate due to plasma more reliably.

  According to the present invention, it is possible to prevent the reverse flow of the plasma and prevent the cooling plate from being damaged, to keep the etching gas flow uniform, and to perform the in-plane uniform plasma processing on the substrate to be processed.

It is a schematic block diagram of a plasma processing apparatus. It is a principal part longitudinal cross-sectional view of the ventilation hole part of the electrode plate of 1st Embodiment of this invention. It is a principal part longitudinal cross-sectional view of the ventilation hole part of the electrode plate of 2nd Embodiment of this invention. It is a principal part longitudinal cross-sectional view of the ventilation hole part of the electrode plate of 3rd Embodiment of this invention.

Hereinafter, a first embodiment of an electrode plate of the present invention will be described with reference to the drawings.
First, a plasma etching apparatus 1 will be described as a plasma processing apparatus using this electrode plate.
As shown in the schematic cross-sectional view of FIG. 1, the plasma etching apparatus 1 is provided with an electrode plate (upper electrode) 3 in the upper part of the vacuum chamber 2 and a gantry (lower electrode) 4 that can be moved up and down in the lower part. Are provided in parallel with the electrode plate 3 at a distance from each other. In this case, the upper electrode plate 3 is supported in an insulated state by the insulator 5 with respect to the wall of the vacuum chamber 2, and the electrostatic chuck 6 and the silicon-made surrounding material are placed on the mount 4. A support ring 7 is provided, and a wafer (substrate to be processed) 8 is placed on the electrostatic chuck 6 with the peripheral edge supported by the support ring 7. 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 the air holes 11 provided in the electrode plate 3. Through the discharge port 12 on the side of the vacuum chamber 2 and discharged to the outside. 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.

  The electrode plate 3 is formed in a disk shape with silicon, and a cooling plate 14 made of aluminum or the like having excellent thermal conductivity is fixed to the back surface of the electrode plate 3. The cooling plate 14 also has a vent hole in the electrode plate 3. Through holes 15 are formed at the same pitch as the air holes 11 so as to communicate with the air holes 11. The electrode plate 3 is fixed in the plasma processing apparatus 1 by screwing or the like with the back surface in contact with the cooling plate. The detailed structure of the electrode plate 3 will be described later.

In the plasma etching apparatus 1, when an etching gas is supplied by applying a high-frequency voltage from a high-frequency power source 13, the etching gas passes through the diffusion member 10, passes through the vent holes 11 provided in the electrode plate 3, and is then connected to the electrode plate 3. Is released into a space between the pedestal 4 and the gantry 4 and becomes plasma in this space, hits the wafer 8, and the surface of the wafer 8 is etched by sputtering, that is, physical reaction and 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 the plasma, the plasma generation region 16 is usually surrounded by a silicon shield ring 17.

Next, the detailed structure of the electrode plate 3 according to the first embodiment of the present invention will be described with reference to FIG.
The electrode plate 3 of the first embodiment is provided with a plurality of vent holes 11 penetrating in parallel with the thickness direction. The air holes 11 are used to supply an etching gas between the electrode plate 3 and the wafer 8 when performing plasma etching. The electrode plate 3 is formed in a disc shape from single crystal silicon, columnar crystal silicon, or polycrystalline silicon.

As shown in FIG. 2, the vent hole 11 has an inclined hole portion 21 formed obliquely with respect to the thickness direction of the electrode plate 3 on the discharge surface 30 a side facing the wafer 8, and the opposite side to the discharge surface 30 a. On the opposite surface 30b side, a vertical inlet-side hole portion 22 formed in parallel with the thickness direction is formed to communicate with each other. A bent portion 25 is formed between the inclined hole portion 21 and the inlet side hole portion 22, and the vent hole 11 is bent and provided. Further, the tip of the inclined hole portion 21 is extended from the inlet side hole portion 22 and an extension portion 26 is provided.
On the discharge surface 30 a of the electrode plate 3, a recess 23 is formed by notching the opening end of the inclined hole portion 21, and the inner peripheral surface at the opening end is notched. The recessed portion 23 is formed so that the opening end portion of the inclined hole portion 21 opens in a plane (notched surface 24) intersecting at right angles to the axial direction. In addition, the code | symbol 21O has shown the axis line of the inclined hole part 21 in the figure, and the code | symbol 22O has shown the axis line of the inlet side hole part 22. FIG.
In addition, as shown in FIG. 2, the recess 23 intersects the two peripheral edges 21 </ b> A and 21 </ b> B facing each other at 180 ° of the inclined hole portion 21 and the inclined hole portion 21 in the cross section along the inclined direction of the inclined hole portion 21. The angles α and β formed with the notch surface 24 of the recess 23 are set to the same angle (approximately 90 ° in FIG. 2) at both peripheral portions.

  In the present embodiment, the vent hole 11 is processed by a drill. For example, with respect to the electrode plate 3 having a plate thickness t of 5 mm or more and 20 mm or less, the hole diameter of the inclined hole portion 21 and the hole diameter of the inlet side hole portion 22 are formed to be 0.3 mm or more and 0.8 mm or less. Has been.

In the electrode plate 3 configured as described above, the angles α and β of the opening end portion of the inclined hole portion 21 are formed at the same angle, which affects the flow of the etching gas ejected from the vent hole 11. The etching gas can be made to flow along the inclination direction of the inclined hole portion 21 without any problem. Thus, the etching gas can be ejected along a desired direction, and the etching gas can be diffused uniformly, so that the wafer can be subjected to a uniform plasma treatment in the surface.
Moreover, since the recessed part 23 is provided in the opening edge part of the inclination hole part 21, and the inner peripheral surface in the opening edge part is notched, the surface which opposes a plasma generation area | region reduces, and plasma is inclined. It is possible to prevent the light from being reflected on the inner peripheral surface of the hole 21 and entering the air hole 11. Further, by providing the bent portion 25 in the vent hole 11, it is possible to suppress the backflow of the plasma having high straightness, and it is possible to prevent the cooling plate from being damaged by the plasma. Furthermore, in the electrode plate 3 of this embodiment, even if plasma penetrates along the inclined hole portion 21, it is blocked by the extension portion 26, so that it is reliably prevented from entering the inlet side hole portion 22. Can do.

  FIG. 3 shows a second embodiment of the present invention. In the electrode plate 31 of the second embodiment, the vent hole 41 has an inclined hole portion 21 formed obliquely with respect to the thickness direction of the electrode plate 31 and a direction different from the inclined direction of the inclined hole portion 21. The inlet side hole portion 27 formed obliquely is formed so as to communicate with it. A bent portion 29 is formed between the inclined hole portion 21 and the inlet side hole portion 27, and the tip of the inclined hole portion 21 is provided so as to extend beyond the inlet side hole portion 27.

A recess 28 is formed on the discharge surface 30 a of the electrode plate 31 so as to partially cut away the opening end of the inclined hole portion 21. In this embodiment, the concave portion 28 is processed by a drill, and the hole diameter thereof is the same as or larger than the hole diameter of the inclined hole portion 21. Further, the concave portion 28 is formed to extend in a plane along the inclination direction of the inclined hole portion 21, and as shown in FIG. 3, in the cross section along the inclination direction of the inclined hole portion 21, Of the two peripheral edges 21A and 21B facing each other by 180 °, the peripheral edge 21A side is notched. The angles α and β formed by the peripheral edges 21A and 21B and the notch surface 24 of the recess 28 intersecting the inclined hole 21 are set to the same angle at both peripheral edges. In the electrode plate 31 shown in FIG. 3, the angles α and β are provided at acute angles. In the figure, reference numeral 27O indicates the axis of the inlet-side hole 27, and reference numeral 28O indicates the axis of the hole forming the recess 28.
Similarly to the electrode plate 3 of the first embodiment, the electrode plate 31 configured as described above can flow the etching gas along the inclined direction of the inclined hole portion 21 by providing the concave portion 28, and plasma Can be suppressed.

FIG. 4 shows a third embodiment of the present invention. In the above-described embodiment, the vent hole is provided by bending the inclined hole portion and the inlet-side hole portion so as to communicate with each other. In the electrode plate 32 of the third embodiment, as shown in FIG. As described above, the vent hole 51 is formed by the inclined hole portion 21 penetrating from the discharge surface 30a of the electrode plate 32 to the opposite surface 30b. And the recessed part 23 which notches the opening edge part of the inclination hole part 21 of the inclination hole part 21 is formed in the discharge surface 30a. Other configurations are the same as those of the first embodiment, and the same reference numerals are given to common portions, and descriptions thereof are omitted.
Also in the electrode plate 32 of the third embodiment, by providing the recess 23 that cuts out the opening end of the inclined hole portion 21, the etching gas can flow along the inclined direction of the inclined hole portion 21, and the backflow of plasma Can be suppressed.

In addition, this invention is not limited to the said embodiment, A various change can be added in the range which does not deviate from the meaning of this invention.
For example, in the cross section along the inclination direction of the inclined hole portion, the angle formed between two peripheral edges of the inclined hole portion that are 180 ° opposite to each other and the notch surface of the concave portion that intersects the inclined hole portion is the same angle at both peripheral edge portions. However, it is not always necessary to set the angles of both peripheral portions to be exactly the same. Similarly, the concave portion is preferably formed so that the opening end portion of the inclined hole portion opens in a plane intersecting at right angles to the axial direction, but in a strict sense, it is not necessarily in a plane intersecting 90 °. It does not have to be formed.

DESCRIPTION OF SYMBOLS 1 Plasma etching apparatus 2 Vacuum chamber 3, 31, 32 Electrode plate (upper electrode)
4 frame (lower electrode)
5 Insulator 6 Electrostatic chuck 7 Support ring 8 Wafer (substrate to be processed)
DESCRIPTION OF SYMBOLS 9 Etching gas supply pipe 10 Diffusion member 11, 41, 51 Vent hole 12 Exhaust port 13 High frequency power supply 14 Cooling plate 15 Through hole 16 Plasma generation area 17 Shield ring 21 Inclined hole part 21O, 22O, 27O, 28O Axis 21A, 21B Periphery 22, 27 Entrance side hole 23, 28 Recessed portion 24 Notch surface 25, 29 Bent portion 30a Discharge surface 30b Opposite surface

Claims (2)

An electrode plate for a plasma processing apparatus disposed opposite to a substrate to be processed in the plasma processing apparatus, comprising a plurality of vent holes penetrating in a thickness direction, the vent holes facing the substrate to be processed. The discharge surface has an inclined hole portion formed obliquely with respect to the thickness direction, and the discharge surface has a recess formed by cutting out an opening end of the inclined hole portion. In the cross-section along the inclination direction of the portion, the angle formed by the two peripheral edges facing each other at 180 ° of the inclined hole portion and the notch surface of the concave portion intersecting the inclined hole portion is the same right angle or acute angle at both peripheral portions. An electrode plate for a plasma processing apparatus , wherein the notched surface is a flat surface, and an opening end of the inclined hole portion is opened in the notched surface . The vent hole has an inlet side hole portion formed from the opposite surface located on the opposite side of the discharge surface to the middle of the thickness direction toward the discharge surface, the inlet side hole portion and the inclined hole portion, The electrode plate for a plasma processing apparatus according to claim 1, wherein the electrode plate is bent by being communicated.

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