JP2012109458A - Focus ring for plasma processing apparatus and plasma processing apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a focus ring for a plasma processing apparatus capable of suppressing wear of the focus ring, keeping a replacement period of the focus ring long, and reducing processing costs of etching and so on.SOLUTION: The focus ring for a plasma processing apparatus comprises: a first ring member 7a disposed opposite to an electrode plate 3 and having a recessed stage part 71 to mount a peripheral edge part of a wafer 8 on an inner circumferential part; and a second ring member 7b to support a lower surface of the first ring member 7a. A cavity part 75, positioned outside of an outer peripheral edge of the recessed stage part 71 in a radial direction, is formed in a ring shape along the circumferential direction on at least one of the first ring member 7a and the second ring member 7b.

Description

  The present invention relates to a focus ring for a plasma processing apparatus and a plasma processing apparatus using the focus ring.

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 through 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.
In such a plasma processing apparatus, a focus ring is used in order to ensure the uniformity of the etching process even at the peripheral portion of the substrate to be processed. The focus ring is formed in a ring shape from a high-purity material such as silicon, and is provided so as to surround the outer peripheral portion of the substrate to be processed. Thereby, the density distribution of the plasma during the etching process can be made uniform, and the uniformity of the etching process and the like can be ensured.

However, when the substrate to be processed is etched using the focus ring, not only the substrate to be processed but also the surface of the focus ring is etched, so that the thickness of the focus ring gradually decreases as the usage time elapses. . This change in thickness becomes an impedance change in the chamber, which causes a change in the plasma discharge state. Therefore, the focus ring is replaced with a new one when the thickness decreases beyond a certain amount.
Moreover, when performing the above-mentioned process, it is inevitable that a part of the reaction product accumulates in the chamber. Then, particles caused by deposits increase in the chamber, and particles are thrown into the plasma, etc., making it impossible to obtain the desired processing characteristics, so the focus ring is discarded while leaving many unconsumed parts. Therefore, the material utilization efficiency is extremely low.

Therefore, Patent Documents 1 and 2 propose a focus ring having a two-body structure. The focus ring is formed of a first member disposed so as to surround the peripheral edge of the substrate to be processed, and a second member provided below to support the first member. Only the first member in which the accumulation of water is remarkable can be replaced.
Moreover, in patent document 3, it is set as the structure which urges | biases toward the center the focus ring piece divided | segmented into multiple along the circumferential direction, eliminates the clearance gap between a support stand and a focus ring, and is based on the wraparound of a plasma This prevents damage to the side wall of the support base and adhesion of particles to the substrate to be processed.

Japanese Patent Laid-Open No. 2002-9048 Japanese Patent Laid-Open No. 2004-79983 JP 2009-290087 A

  However, with the narrowing of the design of semiconductor devices, high uniformity of plasma processing has been strongly demanded, and the focus ring replacement cycle has become shorter. Then, the focus ring taken out from the apparatus at the time of this replacement cycle is disposed as a discarded product as it is. Further, silicon used for the focus ring is an expensive material purified to a high purity, so that it is difficult to reduce the cost.

  The present invention has been made in view of such circumstances, and it is possible to reduce the processing cost such as etching by suppressing the consumption of the focus ring and keeping the replacement period of the focus ring long. A focus ring for a plasma processing apparatus and a plasma processing apparatus are provided.

  The focus ring of the present invention is a focus ring for a plasma processing apparatus that is installed at a position facing the upper electrode in the chamber and supports the periphery of the substrate to be processed so as to surround the peripheral edge of the substrate, and is provided facing the upper electrode. The first ring member having a concave step for placing the peripheral edge of the substrate to be processed on the inner periphery, and the second ring member supporting the lower surface of the first ring member, In at least one of the first ring member and the second ring member, a cavity portion located radially outward from the outer peripheral edge of the concave step portion is formed in a ring shape along the circumferential direction. And

In this case, the first ring member of the focus ring is consumed because it is exposed to the plasma, but only the first ring member can be replaced and the focus ring can be used, thereby improving the use efficiency of the focus ring. Can do.
Moreover, since the cavity of the focus ring is interposed in at least one of the first ring member and the second ring member as a heat insulating space, it is possible to prevent the first ring member from being excessively cooled. Thereby, the accumulation of particles on the surface of the first ring member can be prevented, the replacement cycle can be kept long, and the cost can be reduced.

  In the focus ring of the present invention, the first ring member is made of the same material as the substrate to be processed, and the second ring member is made of a metal material. The peripheral end may be disposed radially inward from the outer peripheral edge of the placement region of the substrate to be processed, and the outer peripheral end of the contact surface may be disposed outward in the radial direction.

  By using a metal material for the second ring member, the strength of the entire focus ring can be improved. In this case, since the second ring member is made of a metal material, it is easy to be cooled. However, since the cavity between the second ring member and the first ring member is a heat insulating space, the temperature difference between the upper and lower surfaces of the first ring member can be reduced. Damage such as cracking can be prevented. Further, the inner peripheral edge of the contact surface between the first ring member and the second ring member is disposed radially inward from the outer peripheral edge of the mounting area of the substrate to be processed, and the outer peripheral edge of the contact surface is radially outward. By placing the substrate to be processed on the inner peripheral end of the contact surface and covering the inner peripheral end, only the surface of the first ring member is present in the plasma generation region. It can be set as the structure exposed. Since the first ring member is made of the same material as the substrate to be processed, it is possible to reduce contamination of impurities into the plasma generation region.

Further, in the focus ring of the present invention, the outer peripheral portion of the contact surface between the first ring member and the second ring member opens radially outwardly, and a part of the plate thickness of at least one of these is provided. It is preferable that a gap formed by cutting out along the circumferential direction is provided.
When replacing the first ring member consumed by the plasma processing, the first ring member and the second ring member stacked by inserting a tool into the gap formed by the adjacent first ring member and second ring member. Can be easily peeled off.

  The plasma processing apparatus of the present invention is characterized in that the above-described focus ring is installed at a position facing the upper electrode in the chamber.

  According to the present invention, accumulation of particles due to the focus ring can be suppressed, the replacement period of the focus ring can be kept long, and only the consumed first member is replaced. Reduction can be achieved.

It is a schematic block diagram of a plasma processing apparatus. It is a longitudinal cross-sectional view which shows 1st Embodiment of the focus ring of this invention. It is a principal part enlarged view of the focus ring shown in FIG. 2, and is a figure explaining the state which inserted the tool in the space | gap part. It is a longitudinal cross-sectional view which shows 2nd Embodiment of the focus ring of this invention.

Hereinafter, embodiments of the focus ring 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 focus ring.
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 with respect to the wall of the vacuum chamber 2 by an insulator 5, and an electrostatic chuck 6 and a focus ring 7 that surrounds the electrostatic chuck 6 are mounted on the mount 4. And a wafer (substrate to be processed) 8 is placed on the electrostatic chuck 6 with a peripheral edge supported by a focus 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 is a gas passage hole provided in the electrode plate 3. 11 is made to flow toward the wafer 8 and discharged from the discharge port 12 on the side of the vacuum chamber 2 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, and the gas passing through the electrode plate 3 is also passed through the cooling plate 14. Through holes 15 are formed at the same pitch as the gas passage holes 11 so as to communicate with the 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.

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 gas passage hole 11 provided in the electrode plate 3, and is electrode plate. 3 is released into the space between the gantry 3 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, ie, physical reaction, and chemical reaction of the etching gas. The
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 focus ring 7 will be described with reference to FIGS.
The focus ring 7 is provided opposite to the electrode plate 3, and includes a first ring member 7a having a concave step portion 71 for placing the peripheral portion of the wafer 8 on the inner peripheral portion, and the first ring member 7a. The first ring member 7a is made of single crystal silicon, columnar crystal silicon, or polycrystalline silicon, and the second ring member 7b is alumite-treated on the surface. It is formed in a ring shape by the applied Al. The area up to the outer peripheral edge of the concave stepped portion 71 of the first ring member 7a is a mounting area for the wafer 8.

  The contact surface 72a of the first ring member 7a with the second ring member 7b is provided with a ring-shaped concave groove 73 along the circumferential direction radially outward from the outer peripheral edge of the concave stepped portion 71, Further, a chamfered surface 74 is provided on the outer peripheral portion of the contact surface 72a of the first ring member 7a. Then, by laminating the concave groove 73 and the chamfered surface 74 with the abutting surface 72b of the second ring member 7b facing each other, a gap is formed between the concave groove 73 of the first ring member 7a and the second ring member 7b. A hollow portion 75 is formed, and the focus ring 7 is opened radially outwardly between the chamfered surface 74 of the first ring member 7a and the second ring member 7b. It is formed.

  The inner peripheral ends 77 of the contact surfaces 72a and 72b of the first ring member 7a and the second ring member 7b are disposed on the inner peripheral surfaces of the ring members 7a and 7b. Since the diameter of the inner peripheral end 77 is smaller than the outer diameter of the wafer 8, the inner peripheral end 77 is disposed radially inward from the outer peripheral edge of the mounting region of the wafer 8. Further, the outer diameters of both the ring members 7a and 7b are formed to be the same diameter, and the outer peripheral ends 78 of the contact surfaces 72a and 72b are arranged outwardly in the radial direction of both the ring members 7a and 7b.

  In the focus ring 7 configured as described above, the cavity 75 provided in the focus ring 7 is interposed between the first ring member 7a and the second ring member 7b as a heat insulating space. It is possible to prevent the member 7a from being excessively cooled. Further, since the alumite coating 70b of the second ring member 7b becomes a heat insulating layer, heat transfer between the first ring member 7a and the second ring member 7b is hindered, and the lower surface (contact surface 72a) of the first ring member 7a. Becomes difficult to cool. Thereby, the temperature difference between the upper and lower surfaces of the first ring member 7a can be reduced, damage such as cracking can be prevented, particle deposition on the surface of the first ring member 7a can be prevented, and the replacement period of the focus ring 7 can be lengthened. Can keep.

  In addition, since the first ring member 7a is formed of high-purity silicon that is the same material as the wafer 8, it is possible to reduce contamination of impurities in the plasma generation region. In the present embodiment, the wafer 8 is placed on the concave step portion 71 of the first ring member 7a, and only the surface of the first ring member 7a is exposed in the plasma generation region. . Accordingly, it is possible to prevent problems such as the second ring member 7b being damaged by being exposed to the plasma, or impurities being generated and particles adhering to the wafer 8.

  Further, since the first ring member 7a is consumed by being exposed to plasma, it is replaced according to the degree of wear. In this replacement operation, as shown in FIG. 3, the first ring member 7a is provided on the first ring member 7a. The formed chamfered surface 74 serves as a guide for the tool T. By inserting the tool T into the gap 76 along the chamfered surface 74, the first ring member 7a and the second ring member 7b can be easily peeled off, and only the first ring member 7a can be replaced. In this case, the tool T inserted as shown by the arrow y in FIG. 3 is pushed inward in the radial direction as it is, or the second ring member 7b is moved from the second ring member 7b by the lever principle while rotating the tool T as shown by the arrow z. The first ring member 7a and the second ring member 7b can be separated by either peeling off the first ring member 7a or by any method.

  FIG. 4 shows a second embodiment of the present invention. The hollow portion 75 of the focus ring 7 only needs to have a hollow portion formed in at least one of the first ring member 7a or the second ring member 7b. Deposition can be prevented. Therefore, in the first embodiment, the hollow portion 75 is formed by the concave groove 73 provided in the first ring member 7a and the contact surface 72b of the second ring member 7b. However, the focus ring of the second embodiment is used. In 90, the hollow part 95 is formed by forming the concave grooves 93a and 93b in both the contact surface surfaces 92a and 92b of the first ring member 90a and the second ring member 90b.

  Further, the second ring member 90b has a convex portion 91 formed along the circumferential direction on the inner peripheral side portion of the ring shape, and the inner surface of the first ring member 90a is formed on the outer peripheral surface of the convex portion 91. The peripheral surface is fitted and laminated. The inner peripheral ends 97 of the contact surfaces 92a and 92b of the first ring member 90a and the second ring member 90b are disposed radially inward from the outer peripheral edge of the mounting area of the wafer 8, and are located above the focus ring 90. However, the diameter of the inner peripheral edge 97 is smaller than the outer diameter of the wafer 8. The outer diameters of both ring members 90a and 90b are formed to be the same diameter, and the outer peripheral ends 98 of the contact surfaces 92a and 92b are arranged outwardly in the radial direction of both ring members 90a and 90b.

  As a result, the inner peripheral ends 97 of the contact surfaces 92a and 92b of the ring members 90a and 90b are covered by placing the wafer 8, and only the surface of the first ring member 90a is exposed in the plasma generation region. It is the composition to do. And since the part exposed to plasma is only the 1st ring member 90a which is a high purity silicon | silicone, mixing of an impurity can be reduced also in this case similarly to 1st Embodiment. 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.

  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.

DESCRIPTION OF SYMBOLS 1 Plasma etching apparatus 2 Vacuum chamber 3 Electrode plate (upper electrode)
Reference Signs List 4 Stand 5 Insulator 6 Electrostatic chuck 7, 90 Focus ring 7a, 90a First ring member 7b, 90b Second ring member 8 Wafer (substrate to be processed)
DESCRIPTION OF SYMBOLS 9 Etching gas supply pipe 10 Diffusion member 11 Gas passage hole 12 Discharge port 13 High frequency power supply 14 Cooling plate 15 Through-hole 16 Plasma generation region 17 Shield ring 70b Anodized coating 71 Concave step part 72a, 72b Contact surface 73, 93a, 93b Concave Groove 74 Chamfered surface 75,95 Cavity 76 Cavity 91 Projection 77,97 Inner peripheral edge 78,98 Outer peripheral end

Claims (4)

  A focus ring for a plasma processing apparatus, which is installed at a position facing the upper electrode in the chamber and supports the periphery of the substrate to be processed so as to surround the periphery, and is provided facing the upper electrode, A first ring member having a concave step for placing the peripheral edge of the processing substrate; and a second ring member that supports the lower surface of the first ring member, the first ring member or the A focus for a plasma processing apparatus, wherein a cavity portion located radially outward from the outer peripheral edge of the concave step portion is formed in at least one of the second ring members in a ring shape along the circumferential direction. ring.   The first ring member is made of the same material as the substrate to be processed, the second ring member is made of a metal material, and the inner peripheral ends of the contact surfaces of both the ring members are formed on the substrate to be processed. The focus for a plasma processing apparatus according to claim 1, wherein the focus is disposed radially inward from an outer peripheral edge of the mounting region, and an outer peripheral end of the contact surface is disposed radially outward. ring.   The outer peripheral portion of the contact surface between the first ring member and the second ring member is opened radially outward, and a part of at least one of the plate thicknesses is cut out along the circumferential direction. The focus ring for a plasma processing apparatus according to claim 1, wherein a gap is provided. A plasma processing apparatus, wherein the focus ring according to any one of claims 1 to 3 is installed at a position facing the upper electrode in the chamber.

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