JP2006165424A - O-ring structure of plasma generator - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an O-ring structure in a plasma generator for generating a halogen plasma having a high corrosive property, which structure can prevent the corrosion of an O-ring provided at an interconnection between a plasma chamber and an external device connected to the plasma chamber, and also can increase the gas tightness of the interconnection to the atmosphere. <P>SOLUTION: The O-ring structure of the plasma generator has an inner O-ring 33 of a small diameter made of a fluorine resin-based material higher in corrosion resistance than the halogen plasma, and an outer O-ring 34 of a large diameter made of a rubber-based material having a high gas-tightness. The inner and outer O-rings 33 and 34 are provided between an alumina plate 32 provided in an upper recess 31 of a plasma chamber 11 as a micro-wave window and the bottom of the recess 31. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a plasma generation device, and more particularly to an O-ring structure of a plasma generation device with improved airtightness due to an O-ring provided at a connecting portion between a plasma chamber and an external device.

  In the plasma generator, a parallel electrode is arranged in the plasma chamber, a high frequency voltage generator is applied to the parallel electrode to generate a plasma in the decompressed plasma chamber, and a high frequency coil is provided around the plasma chamber. A dielectric type plasma generator for generating plasma in a depressurized plasma chamber by supplying power to the coil with a high frequency power source, and further utilizing microwaves for generating plasma by supplying microwave power to the depressurized plasma chamber There are plasma generators.

FIG. 7 is a schematic configuration diagram illustrating a microwave plasma generation apparatus.
In the plasma generator 10, a microwave window 13 made of a quartz plate 12 is provided in an upper part of a plasma chamber 11, and microwave power is supplied from the microwave window 13 into the plasma chamber 11.

  That is, microwave power output from a microwave oscillator (not shown) is sent through the waveguide 14, passes through the coupling hole 15, the quartz plate 12, and the connection hole 16 of the plasma chamber 11, and enters the plasma chamber 11. Projected on.

  In addition to supplying microwave power, the quartz plate 12 functions to shut off the inside of the plasma chamber 11 from the atmosphere. Therefore, an O-ring 17 is provided at the position of the quartz plate 12. A quartz plate 12 is disposed in an airtight configuration.

  In addition, the plasma generator 10 is provided with a vacuum pipe 18 connected to a vacuum pump for decompressing the inside of the plasma chamber 11, a gas supply pipe 19 for supplying gas to the plasma chamber 11, and the like.

The microwave plasma generation apparatus 10 generates surface wave excitation plasma 20 and plasma-processes the workpiece 21. Often, halogen plasma is used.
Halogen plasma is generated by specifying the type of gas supplied to the plasma chamber 11, and performs a process such as etching of a semiconductor or a metal or ceramic component.

However, since halogen plasma is highly corrosive plasma, the quartz plate 12 and the O-ring 17 are likely to be chemically corroded.
Therefore, although the quartz plate 12 is mechanically strong and inexpensive, it is prone to chemically corrode, so that there is a problem that the corrode advances due to halogen plasma, holes are formed, and dust is generated. .

Further, the O-ring 17 made of rubber material cannot be kept airtight because it is chemically corroded by halogen plasma.
That is, the O-ring 17 of rubber-based material is generally highly airtight, but is corroded by halogen plasma, so that it is difficult to airtightly place the quartz plate 12, and dust caused by corrosion is treated. 21 is mixed.

Therefore, when halogen plasma is used, an alumina plate is used instead of the quartz plate 12, and an O-ring 17 made of a fluorine resin material (for example, polytetrafluoroethylene) is used.
The O-ring 17 made of an alumina plate or a fluororesin-based material hardly corrodes even when irradiated with halogen / plasma, but has the following problems.

  Since the alumina plate reflects more microwave power than the quartz plate, plasma is not generated unless the degree of vacuum in the plasma chamber 11 is maintained at a predetermined value or higher (for example, 1 Pa or higher). There arises a problem that the object 21 is restricted.

The O-ring 17 made of a fluororesin material is very expensive and plastically deforms at a temperature of 150 ° C. or higher. Therefore, the degree of vacuum in the plasma chamber 11 is not changed unless the workpiece 21 is replaced for each plasma treatment. It becomes difficult to keep.
Therefore, there is a problem that the cost of the O-ring 17 is increased and the replacement thereof takes time.

JP 2002-280196 A

  In view of the above-described circumstances, an object of the present invention is to propose an O-ring structure of a plasma generator having corrosion resistance and airtightness for an O-ring provided at a connecting portion between a plasma chamber and an external device.

  In order to achieve the above-described object, in the present invention, as a first invention, in an O-ring structure of a plasma generator in which an O-ring is provided at a connecting portion between a plasma chamber to be decompressed and an external device to seal the plasma chamber, A first O-ring having a small ring diameter formed from a highly corrosive material and a second O-ring having a large ring diameter formed from a highly air-tight material are provided, and the first O-ring is formed on the connecting hole side of the connecting portion. The present invention proposes an O-ring structure for a plasma generator, in which one O-ring is provided and the second O-ring is disposed outside the first O-ring.

  According to a second invention, in the O-ring structure of the first invention, the first O-ring is formed of a fluororesin material and the second O-ring is formed of a rubber material. The O-ring structure of the device is proposed.

  As a third invention, in the O-ring structure of the first invention, a connecting portion of a waveguide for supplying microwave power into the plasma chamber, a connecting portion of a spectrometer for confirming a plasma generation state in the plasma chamber, The first and second O-rings are arranged on all or a part of each connecting portion such as a connecting portion of a vacuum gauge for measuring the degree of vacuum in the plasma chamber. A ring structure is proposed.

  As a fourth invention, in the O-ring structure of the first invention, an alumina plate or an alumina thin film is provided on a plate surface on the plasma side of a quartz plate constituting a microwave window for supplying microwave power into the plasma chamber. Proposed is an O-ring structure of a plasma generator, characterized in that the first and second O-rings are disposed between the quartz plate and a plasma chamber where the quartz plate is installed. .

According to the first to third inventions, since the first O-ring having high corrosion resistance formed of the fluororesin-based material is disposed close to the connection hole, the plasma hits the first O-ring. .
And the plasma which passed through the clearance gap between a 1st O-ring and the arrangement | positioning location hits the 2nd O-ring provided in the outer side of the 1st O-ring.
From this, since the plasma irradiated to the second O-ring is extremely small, the second O-ring can be formed of a rubber material having high airtightness.

  In other words, when highly corrosive halogen plasma is generated, the first O-ring is plastically deformed at a high temperature, making it difficult to maintain hermeticity, but this first O-ring hits the second O-ring. Stop most.

  Therefore, even if the second O-ring is formed of a rubber-based material having high airtightness, the second O-ring is not corroded by halogen plasma, and the connecting portion has an airtight structure by the second O-ring. , The atmosphere is cut off and the vacuum degree of the plasma chamber is maintained.

A fourth invention is an O-ring structure in which first and second O-rings are disposed in a microwave window connecting waveguides, and the microwave window is a quartz plate.
The quartz plate is provided with an alumina plate or an alumina thin film to prevent corrosion by halogen plasma, and further, first and second O-rings are disposed between the quartz plate and the plasma chamber, Maintains the degree of vacuum in the chamber.

Next, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a schematic configuration diagram of a plasma generator showing an embodiment of the present invention, and FIG. 2 is a partial view of a plasma chamber showing a microwave window without a waveguide.

  As shown in the figure, this plasma generator 30 is provided with an alumina plate 32 as a microwave window 13 in an upper recess 31 of the plasma chamber 11, and between the alumina plate 31 and the bottom surface of the recess 31, An inner O-ring (first O-ring) 33 and an outer O-ring (second O-ring) 34 are provided, and the alumina plate 32 is hermetically arranged.

  Since the rest of the configuration is the same as that of the conventional plasma generator shown in FIG. 7, the same members and the same portions are denoted by the same reference numerals, and description thereof is omitted.

The inner O-ring 33 is formed in a ring shape with a fluororesin-based material that is less corrosive to halogen / plasma, and is disposed at a position close to the connecting hole 16 of the plasma chamber 11 as shown in FIG.
The outer O-ring 34 is formed in a ring shape with a highly airtight rubber material, and is disposed outside the inner O-ring 33 as shown in FIG.

  The plasma generator generates halogen plasma 20 and plasma-treats the workpiece 21 in the same manner as in the conventional example. During the processing, the plasma 20 is also irradiated to the inner O-ring 33. The ring 33 is heated and plastically deforms.

Although the inner O-ring 33 is not corroded by the halogen plasma, a slight gap is formed between the alumina plate 32 and the bottom of the recess 31 due to the deformation thereof. There is almost no airtightness.
However, since the plasma 20 that reaches the outer O-ring 34 through the gap generated by the deformation of the inner O-ring 33 is very little, the outer O-ring 34 hardly corrodes.

As a result, since the space between the plasma chamber 11 and the alumina plate 32 is sealed by the highly airtight outer O-ring 34, the degree of vacuum of the plasma chamber 11 is reliably maintained.
That is, the inner O-ring 33 blocks the plasma 20 reaching the outer O-ring 34, and the outer O-ring 34 performs an airtight action to reliably block the inside of the plasma chamber 11 from the atmosphere.

The airtight action of the inner O-ring 33 and the outer O-ring 34 will now be described in detail with reference to FIGS.
3 is an enlarged cross-sectional view taken along the line AA in FIG. 2. In this figure, d is a wire diameter of the outer O-ring 34, D is a ring diameter of the outer O-ring 34, and g is a deformation of the inner O-ring 33. The thickness (r) of the gap (gap) generated by, r represents the radius of the gap.
As shown in FIG. 4, the gap is formed above and below the inner O-ring 33, but for the sake of simplicity, the gap is assumed to be a single layer and will be described as g = g 1 + g 2.

If the density of radicals eroding the outer O-ring 34 among the radicals generated by the halogen plasma 20 is Nr and the average velocity is Vr, the flux F1 passing through the gap of the inner O-ring 33 is
F1 = (1/4) · Nr · Vr · 2πr · g
This flux F1 radiates and erodes the outer O-ring 34.

On the other hand, as in the conventional example, when there is no inner O-ring 33 and the outer O-ring 34 is directly irradiated by the halogen plasma 20, the flux F2 hitting the outer O-ring 34 is
F2 = (1/4) · Nr · Vr · π · D · d
It becomes.
Therefore, F1 / F2 = 2 rg / Dd
It becomes.
Here, if 2r≈D, g = 0.01 mm, d = 5 mm,
F1 / F2 = 2 × 10 ⁻³
Thus, it can be seen that the corrosion of the outer O-ring 34 is greatly reduced.

On the other hand, since the molecules generated by the corrosion of the outer O-ring 34 return to the plasma side, they pass through the gap of the inner O-ring 33.
(F1 / F2) ² = 4 × 10 ⁻⁶
Therefore, the influence of plasma contamination due to corrosion hardly occurs.

As described above, the O-ring structure of the inner O-ring 33 and the outer O-ring 34 can surely prevent air leakage at the place where the alumina plate 32 is disposed, and the O-ring does not corrode. I don't need it.
Furthermore, no plasma contamination of dust generated by O-ring corrosion occurs.

FIG. 5 is a sectional view similar to FIG. 3, showing another embodiment of the present invention.
In this embodiment, a quartz plate 35 is provided as the microwave window 13.
As described above, since the quartz plate 35 is chemically corroded by the irradiation of the halogen plasma 20, the alumina thin plate 36 is bonded to one side surface which becomes the plasma side.
Note that an alumina thin film may be formed by depositing an alumina material instead of the alumina thin plate 36.

  The plasma generating apparatus configured as described above can use the quartz plate 35 that is advantageous for generating plasma and can maintain airtightness by the outer O-ring 34.

  As described above, in the present invention, the O-ring structure of the inner O-ring 33 and the outer O-ring 34 is provided at the connecting portion between the microwave window 13 and the waveguide 14, but the present invention is otherwise as shown in FIG. In addition, the connecting portion 38 of the spectroscope 37 connected to the plasma chamber 11 and the connecting portion 40 of the vacuum gauge 39 can be similarly provided.

  That is, the plasma generator 30 is generally provided with a spectroscope 37 for confirming plasma, a vacuum gauge 39 for measuring the degree of vacuum in the plasma chamber 11, and the like. The portions 38 and 40 also have two O-rings 41 and 42 similar to the inner O-ring 33 and the outer O-ring 34 described above, thereby providing a connection portion having high corrosion resistance against halogen plasma.

  Note that the present invention is not limited to the plasma generator using microwaves, but can be implemented in the same manner as described above with respect to the connecting portion of the high-frequency plasma generator and dielectric plasma generator.

  The present invention can be applied to a plasma generator that generates highly corrosive halogen plasma.

It is a schematic block diagram of the plasma generator which shows embodiment of this invention. It is the fragmentary figure of the said plasma generator which abbreviate | omitted the waveguide and showed the microwave window part. It is an AA line expanded sectional view on FIG. FIG. 4 is a partially enlarged view of FIG. 3. It is an expanded sectional view similar to FIG. 3 showing another embodiment. It is a schematic block diagram of the plasma generator which shows embodiment implemented in the connection part of the spectrometer connected to a plasma chamber, or a vacuum gauge. It is a schematic block diagram of the plasma generator shown as a prior art example.

Explanation of symbols

11 Plasma chamber 13 Microwave window 16 Connecting hole 30 Plasma generator 32 Alumina plate 33 Inner O-ring (first O-ring)
34 Outer O-ring (second O-ring)
35 Quartz plate 36 Alumina thin plate

Claims (4)

In the O-ring structure of the plasma generator that seals the plasma chamber by providing an O-ring at the connecting portion between the plasma chamber to be decompressed and the external device,
A first O-ring with a small ring diameter formed from a highly corrosion-resistant material and a second O-ring with a large ring diameter formed from a highly air-tight material are provided,
An O-ring structure for a plasma generating apparatus, wherein the first O-ring is disposed on the coupling hole side of the coupling portion, and the second O-ring is disposed on the outer side of the first O-ring. The O-ring structure according to claim 1,
An O-ring structure of a plasma generator, wherein the first O-ring is made of a fluororesin material and the second O-ring is made of a rubber material. The O-ring structure according to claim 1,
Each of the connecting part of the waveguide for supplying microwave power into the plasma chamber, the connecting part of the spectrometer for checking the plasma generation state in the plasma chamber, the connecting part of the vacuum gauge for measuring the degree of vacuum in the plasma chamber, etc. An O-ring structure for a plasma generating apparatus, wherein the first and second O-rings are disposed on all or a part of the connecting portions. The O-ring structure according to claim 1,
An alumina plate or an alumina thin film is provided on the surface of the quartz plate that constitutes the microwave window that supplies microwave power to the plasma chamber, and the quartz plate and the plasma chamber portion in which the quartz plate is installed An O-ring structure for a plasma generator, wherein the first and second O-rings are disposed between the first and second O-rings.

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