JPH0697118A - Plasma processing system - Google Patents

Abstract

PURPOSE:To obtain a plasma processing system having such structure as uniformity can be ensured in the processing by keeping the impedance at power supply section substantially constant regardless of coupling/uncoupling of RF power supply section. CONSTITUTION:A first RF power supply section 16 having double pipe structure of outside and inside power supply pipes 16A, 16B and connected with the load side, and a second RF power supply section 20 constituted of an outside bracket 22 and an inside power supply pipe 24 and connected with the high frequency power supply side are provided to be coupled or uncoupled each other. At a joint A where the outside power supply pipe 16A and the bracket are fastened through bolts, a conductive ring member 28 is placed between the opposing faces.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a plasma processing apparatus, and more particularly to a structure for supplying power to a plasma generating electrode.

[0002]

2. Description of the Related Art Generally, there is a magnetron etching apparatus shown in FIG. 4 as an example of an apparatus for generating plasma for performing dry etching in a semiconductor wafer manufacturing process. In this apparatus, a process chamber 32 is provided at a position adjacent to a load lock chamber 30 which is a vacuum-atmosphere conversion chamber. The susceptor 32A placed inside the process chamber 32 for mounting a wafer is configured as one electrode, a so-called RF cathode electrode, and the other electrode is configured by the upper wall of the process chamber 32 which is grounded. By supplying high-frequency power from the high-frequency power source 36 to the RF cathode electrode via the impedance matching device 34, plasma is generated between the electrodes.

The electrons in the plasma thus generated are orthogonal to the electric field formed between the electrodes due to the rotating magnetic field formed by the rotating permanent magnet M located outside the process chamber 32. A cycloid motion is caused by the action with the magnetic field component, and by this,
The frequency of collision with gas molecules in plasma is increased to increase discharge efficiency and increase plasma density.

[0004]

By the way, in the plasma processing apparatus of this kind, repeated processing is carried out both when the single wafer processing is carried out as in the above-mentioned etching apparatus or when the batch processing is carried out. The uniformity of processing between wafers is required. Furthermore, in this type of plasma processing apparatus, reaction by-products adhere to the inner wall of the chamber, which reduces the processing yield,
It is necessary to perform regular maintenance. At this time, the present inventor has noticed that the uniformity of processing between wafers is impaired before and after the maintenance.

As a result of further study on the cause of impairing the uniformity of wafer processing before and after the maintenance, it was found that the characteristic impedance of the transmission line supplying the high frequency power changes before and after the maintenance. This will be explained below.

As a power supply structure to the susceptor forming one of the plasma generating electrodes, it is desirable to adopt the structure shown in FIG. 5, for example. That is, the RF power feeding tube 38 used for the power feeding structure is the RF power feeding tube 38 which is a ground side tube.
It is composed of a double tube consisting of A and an inner RF power feed tube 38B, and the power feed tubes are isolated from each other by an insulator arranged therebetween. And the RF power supply tube 38A on the ground side
6, the end portion on the impedance matching device 34 side is inserted and fitted into a split cylindrical bracket 40 fastened by bolts, for example, as shown in FIG. 6, and this bracket 40 is connected to the impedance matching device 34. An RF return path connected to the ground side is formed by bolting to the housing of the. Also, the inner RF power feed tube 38B is
R is connected to the matching circuit in the impedance matching device 34.
It constitutes a power supply path to the F cathode electrode.

Both of the above-mentioned power supply pipes 38 have a joint part in the middle of the current-carrying path. Specifically, in the case of the ground-side power supply pipe 38A, the inner surface of the bracket 40 and the outer surface of the end of the power supply pipe 38A. This corresponds to the facing position A of the bracket 40 and the facing position B of the bottom surface of the bracket 40 and the upper surface of the housing of the impedance matching device 34 connected to the bracket 40. Therefore, in these joints, as shown in FIG. 7, the joint surface does not become a flat surface due to the processing roughness, so-called surface contact is not possible, and there is a gap between the opposing surfaces. G is present. Therefore, an equivalent circuit as shown in FIG. 8 is formed between the facing surfaces, and has an equivalent impedance (Z0) represented by the following equation.

Z 0 = (L / C) ^1/2 This equivalent impedance is not constant before and after maintenance because the gap distance changes depending on the magnitude of the fastening force. Therefore, the RF power supplied to the load-side electrode changes before and after the maintenance, and the uniformity of wafer processing is impaired. Furthermore, due to insufficient tightening force or due to loose nuts, etc., the tightening force weakens over time,
There is a possibility that the equivalent impedance (Z0) will increase and the power supply efficiency will decrease.

For the purpose of avoiding the occurrence of such a problem, it is conceivable to increase the fastening force at the joint portion at any time after maintenance, or to carry out a surface treatment or the like to improve the conductive efficiency. When increasing the force, it is difficult to set the fastening force one by one according to the change in mechanical strength at that position, and depending on the surface treatment, new problems such as decrease in conductivity due to oxidative corrosion may occur. May trigger.

Therefore, an object of the present invention is to improve the uniformity of processing in view of the problem in the power supply structure in the plasma processing apparatus, and to prevent the efficiency of power supply to the plasma generating electrode from decreasing. It is an object of the present invention to provide a plasma processing apparatus having a structure capable of achieving this.

[0011]

According to the present invention, plasma is generated by supplying high-frequency power to electrodes from a high-frequency power source side through an RF power supply section, and an object to be processed disposed facing the plasma is processed. In the plasma processing apparatus, the RF power feeding unit has a first R connected at one end to the electrode side.
The F power supply section and a second end whose one end is connected to the high frequency power supply side
A conductive member which has a RF power feeding part, and which is configured as a joint part capable of fastening and releasing the other end sides in a face-to-face relationship and which is compressed and deformed by fastening between the facing faces of the joint part. It is characterized by the interposition.

[0012] Here, the RF power feeding unit is composed of a double tube, an outer tube is a grounding section connected to a casing of an impedance matching device, and an inner tube is connected to the high frequency power source through an impedance matching circuit. The outer side,
The conductive member may be disposed between the facing surfaces of the joint portion of one or both of the inner pipes.

[0013]

The characteristic impedance of the line of the RF feeder, particularly the equivalent impedance at the joint, is required in order to improve the uniformity of the processing between the objects to be plasma-processed before and after attaching and detaching the joint of the RF feeder. Should be almost constant. According to the present invention, the flexible conductive member interposed between the facing surfaces of the joint makes it possible to make the contact resistance substantially constant despite the slight fluctuation of the fastening force, and the inductance L in the contact region of the joint is almost constant. I am trying.
Furthermore, since the gap between the facing surfaces is also substantially constant by the conductive member, the capacitance C is also constant. Therefore, even before and after maintenance, the equivalent impedance (Z0) at the joint can be made substantially constant, so that the treatment can be made uniform among the objects to be treated. Further, since the contact resistance is reduced by the conductive member, the inductance L in the above equation is reduced and the equivalent impedance (Z0) is reduced, so that the power feeding efficiency can be improved.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment in which the plasma processing apparatus of the present invention is applied to a dry etching apparatus of RIE system will be specifically described below with reference to the drawings.

FIG. 1 is a diagram showing the structure of a process chamber in a dry etching apparatus of the RIE system. This process chamber 10 is a lower chamber 1.
0A and the upper chamber 10B. The lower chamber 10A has a bottomed cylindrical portion that exposes only the wafer mounting surface side of the susceptor 12 in the chamber and covers the other portions, and the lower end thereof is the upper chamber 10B.
An airtight container is formed by being connected to the airtight container. The chamber 10 can be evacuated and an etching gas can be introduced.

On the other hand, the susceptor 12 is composed of a conductive plate of Al or the like which is electrically isolated from the lower chamber 10A through an insulator 14 which is arranged between the lower chamber 10A and the lower chamber 10A. The semiconductor wafer W, which is the object to be processed, can be placed. The susceptor 12 functions as an RF cathode in the RIE method, and therefore, the upper chamber 10B facing the susceptor is grounded and functions as a counter electrode.

Then, a first RF power feeding section for supplying RF power to the susceptor 12 is provided. The first RF power feeding section 16 has a double tube structure, and the outer power feeding tube 16A has an upper end portion which is the lower chamber 10.
It is integrally molded with A and is formed so as to extend downward in a hollow cylindrical shape. The power supply pipe 16B inside the power supply pipe 16A is also formed in a hollow cylindrical shape.

A second RF power feeding section 20 is provided which is attachable to and detachable from the first RF power feeding section 16. The second RF power feeding unit 20 includes a bracket 22 connected to the outer power feeding tube 16A and a power feeding tube 24 connected to the inner power feeding tube 16B.

The bracket 22 to which the end portion of the outer feed tube 16A of the first RF feed section 16 is attached has a split cylindrical shape having a bottom plate flange 22A as in the structure shown in FIG. The flange 22A is joined to the upper surface of the housing of the impedance matching device 18 by being fastened with the bolt 26, and is tightened with the bolt (not shown) in a state where the divided surfaces are aligned, so that the outside The lower end of the power supply pipe 16A can be integrally joined. On the other hand, the power supply pipe 24 arranged coaxially inside the bracket 22 has its upper end at the power supply pipe 16B.
It is possible to fasten and release it with a screw and its lower end through a matching circuit in the impedance matching device 18,
It is connected to a high frequency power source 27 which is a source of high frequency, for example, 13.56 MHz and 40 MHz.

A joint A between the outer feed tube 16A of the first RF feed section 16 and the bracket 22 of the second RF feed section 20, and a joint between the bracket 22 and the upper surface of the housing of the impedance matching box 18. In B, as shown in FIG. 2, a conductive ring member 28 is interposed. In the case of this embodiment, the conductive ring member 28 is composed of an O-ring, and is compressed and deformed as shown in FIG. 9 when the facing surfaces of the joints A and B are tightened by the bolts 22. The adhesion between the facing surfaces is improved.

Next, the operation will be described.

When the semiconductor wafer W is mounted and fixed on the susceptor 12, high frequency power is supplied to the susceptor 12 via the high frequency power supply 27, the impedance matching device 18, and the first and second RF power supply parts 16 and 20. , Plasma is generated between the upper chamber 10B, which is a counter electrode, and etching is started.

According to the apparatus of this embodiment, the uniformity of the processing between the semiconductor wafers W to be plasma-processed can be improved even before and after the joining portions A and B of the RF power feeding portion are attached and detached. The reason will be described below.

(1) When the joints A and B are fastened with bolts, the conductive ring 28 interposed between the opposing surfaces is compressed and deformed, and the conductive ring 28 and the conductive portions on both sides thereof have high adhesion. Sex is obtained. This adhesiveness can be maintained even if the bolt fastening force fluctuates to some extent, and the contact resistance between the conductive ring 28 and the conductive portions on both sides thereof can be made substantially constant. Therefore, the inductance (L) generated in the region of the conductive ring 28 serving as the contact portion can be maintained substantially constant even if the bolt fastening force slightly changes before and after the maintenance. Further, the contact portions of the joint portions A and B are only at the positions where the conductive ring 28 is interposed. This contact position is constant before and after maintenance, and other positions do not contact. For this reason,
The position where the inductance L component occurs is always constant,
In addition, since the contact resistance is almost constant as described above, this inductance L can be always kept substantially constant. Further, the gap distance between the facing surfaces of the joints A and B is kept substantially constant by the conductive ring 28, and this gap distance is invariable despite some fluctuation of the bolt fastening force. Therefore, the capacitance C formed by the gap at the junctions A and B is also constant. As described above, the equivalent impedance Z0 at the junctions A and B is almost constant without changing the inductance L and the capacitance C before and after the maintenance. Therefore, the impedance of the line in the power feeding path is constant before and after the maintenance. Can be Therefore,
The high frequency power consumed by the susceptor 12 on the load side can be kept substantially constant. Therefore, it is possible to improve the uniformity of processing between the semiconductor wafers W that are repeatedly processed.

(2) By disposing the conductive ring 28 between the facing surfaces of the joints A and B, it is possible to reduce the change in impedance with time. This change over time
For example, this occurs due to loosening of the nut, but according to the present embodiment, even if the fastening force slightly fluctuates due to loosening of the nut, the contact resistance does not fluctuate as described above. It is possible to prevent the fluctuation of the equivalent impedance Z0 at the junctions A and B.

(3) Further, according to the present embodiment, only the regions where the conductive ring 28 is disposed in the joints A and B are provided, and even if the conductive portions on both sides are oxidized, the conductive portions on both sides are oxidized. It is possible to constantly maintain a gap in which the oxide films do not come into contact with each other. Therefore, even if the state of the surface of the conductive portion changes due to corrosion or the like, the inductance L does not change, and the equivalent impedance Z0 at the junctions A and B can be maintained substantially constant.

In addition to the fact that the equivalent impedances at the junctions A and B can be made substantially constant in a single device, the equivalent impedances at the junctions A and B can be made uniform among a plurality of devices, and a plurality of devices It can also contribute to improvement of processing uniformity between the wafers processed as described above.

Next, considering the power feeding efficiency, the junction A between the outer feed tube 16A forming the RF return path and the bracket 20 and the junction B between the bracket 20 and the upper surface of the housing of the impedance matching device 18 are electrically conductive. Since the flexible ring member 24 is closely attached,
The contact resistance between the facing surfaces can be reduced. Therefore, the inductance (L) component in the equivalent circuit is reduced by the presence of the conductive ring member, and thus the impedance (Z0) in the power feeding path can be reduced. As a result, the conductivity in the power supply path is improved, and the power supply efficiency is improved as compared with the conventional structure.

In the above embodiment, as the material for the conductive ring member, for example, an elastic body such as conductive rubber containing fine metal powder can be used. The conductive member is not limited to a member such as an O-ring that is locally arranged between the facing surfaces of the joint, but may be, for example, a sheet-shaped conductive member that is arranged in the entire region between the facing surfaces. May be.

Although the present invention is applied to the power supply section on the RF return side in the above-described embodiment, the present invention can also be applied to the power supply section on the RF hot side, that is, the joint between the power supply tubes 16B and 24. For example, as shown in FIG. 3, it is possible to interpose the above-mentioned conductive ring member 28 between the opposed end faces of the joint portion C of the power supply pipes 16B and 24 joined by screw connection.

Further, the first and second RF power feeding units 16 and 2
By interposing the conductive ring member 28 in each of the joints of the outer tube and the inner tube that form 0,
As compared with the case where the present invention is applied only to the joint portion of the outer pipe or the inner pipe described above, it is possible to secure better processing uniformity and power supply efficiency.

Although the above-described embodiment is an embodiment in which the present invention is applied to an RIE type etching apparatus, the plasma processing apparatus to which the present invention is applied is not limited to the above-mentioned etching apparatus, and various other types. In addition to the etching system of the type, it can be similarly applied to, for example, a sputtering, ashing or CVD apparatus using plasma.

[0033]

As described above, according to the present invention,
By interposing a conductive member in the joint between the first and second RF power feeding units, the equivalent impedance at the joint can be made substantially constant before and after the joint is attached and detached, and before and after the joint is detached due to maintenance or the like. It is possible to suppress fluctuations in the RF power supplied to the electrode on the load side and improve processing uniformity. Further, the power supply efficiency can be improved by reducing the equivalent impedance at the joint.

[Brief description of drawings]

FIG. 1 is a schematic sectional view of a dry etching apparatus to which the present invention is applied.

FIG. 2 is an enlarged schematic cross-sectional view of a part of a power feeding path in the dry etching apparatus shown in FIG.

3 is an enlarged schematic cross-sectional view of another portion of the power feeding path shown in FIG.

FIG. 4 is a diagram showing an example of a conventional plasma processing apparatus.

5 is a schematic cross-sectional view showing a part of the plasma processing apparatus shown in FIG.

6 is a perspective view showing the structure of a part of the joint shown in FIG.

FIG. 7 is a diagram for explaining a surface state of the joint portion shown in FIG.

8 is a circuit diagram for explaining an equivalent circuit in a gap due to the surface state shown in FIG.

FIG. 9 is an enlarged view showing a state of a joint portion in which a conductive member is interposed.

[Explanation of symbols]

 Reference Signs List 10 process chamber 10A lower chamber 10B upper chamber forming counter electrode 12 susceptor forming RF cathode electrode 16 first RF power supply unit 16A outer power supply tube forming ground side 16B inner power supply tube forming high frequency power application side 18 impedance matching Container 20 second RF power supply unit 28 conductive ring member

Claims (2)

[Claims] 1. A high-frequency power source side through an RF power feeding unit,
Plasma is generated by supplying high frequency power to the electrodes,
In the plasma processing apparatus for processing an object to be processed which is arranged facing the plasma, the RF power feeding unit has a first end connected to the electrode side.
And a second RF power supply portion having one end connected to the high-frequency power supply side, and the other end side is configured as a joint part capable of fastening and releasing the other end sides face-to-face, and
A plasma processing apparatus, wherein a conductive member that is compressed and deformed by fastening is interposed between the facing surfaces of the joining portion. 2. The RF power feeding unit according to claim 1, wherein the RF power feeding unit is a double pipe, the outer pipe is a grounding unit connected to a casing of an impedance matching device, and the inner pipe is the high frequency wave through an impedance matching circuit. Connected to the power supply,
A plasma processing apparatus, wherein the conductive member is arranged between the facing surfaces of the joint portion of one or both of the outer and inner tubes.