Power distribution for multiple electrode plasma systems using quarter wavelength transmission lines

• US 5,733,511 A
• Filed: 11/21/1995
• Issued: 03/31/1998
• Est. Priority Date: 06/21/1994
• Status: Expired due to Fees

• Current Assignee: BOC Group Pty Limited (Linde Plc)
• Original Assignee: BOC Group Pty Limited (Linde Plc)
• Inventors: De Francesco, Frank
• Primary Examiner(s): Jordan, Charles T.
• Assistant Examiner(s): JENKINS, DANIEL J
• Application Number:
  US08/563,881
• Time in Patent Office: 861 Days
• Field of Search: 422/186, 422/186.85, 422/907, 118/715, 118/723 R, 118/723 E, 315/111.21
• US Class Current: 422/186.05
• CPC Class Codes: B01J 2219/0894 Processes carried out in the presence of a plasma
• CPC Class Codes: H01J 37/32082 Radio frequency generated discharge H01J37/32357, H01J37/32366, H01J37/32394 and H01J37/32403 take precedence
• CPC Class Codes: H01J 37/32174 Circuits specially adapted for controlling the RF discharge
• CPC Class Codes: H05H 1/46 using applied electromagnetic fields, e.g. high frequency or microwave energy H05H1/26 takes precedence
• CPC Class Codes: Y10S 422/907 Corona or glow discharge means

Abstract

A multiple electrode plasma reactor power splitter and delivery system to provide balanced power to a plurality of powered electrodes by utilizing the properties of quarter wave length transmission lines. Each electrode is supplied power by a separate (2N+1)λ/4 wavelength cable, where N=0,1,2 . . . , connected to a common point at a load matching network'"'"'s output. The impedance transformation properties of these lines are also employed to convert the plasma load to one that is more efficiently matched into by a standard network. Also disclosed is a technique of splitting a single large active electrode into smaller active electrodes powered by the above distribution scheme in order to achieve maximum uniformity of the reactive plasma throughout the working volume.

Claims

1. A multiple electrode plasma reactor comprising:

a reactor chamber;

an RF generator;

an electrical matching network connected to the RF generator;

two or more powered electrodes being disposed within said reactor chamber;

at least one separate transmission line being connected to said matching network and to each said powered electrode, each said transmission line having a length approximately equal to a 1/4 wavelength transmission line.

2. A multiple electrode plasma reactor as described in claim 1 wherein two or more of said transmission lines are connected in parallel to at least one said electrode.

3. A multiple electrode plasma reactor as described in claim 1 wherein the length of each said transmission line is within 5% of an experimentally determined length of a 1/4 wavelength transmission line.

4. A multiple electrode plasma reactor as described in claim 1 wherein the length of each said transmission line is within 2% of an experimentally determined length of a 1/4 wavelength transmission line.

5. A multiple electrode plasma reactor as described in claim 1 wherein at least one of said transmission lines has a length equal to a 1/4 wavelength line and at least one of said transmission lines have a length equal to a 3/4 wavelength transmission line, such that the voltage is 180°

out of phase in opposed pairs of said electrodes, so as to differentially excite the plasma between said opposed electrodes.

6. A multiple electrode plasma reactor as described in claim 5 wherein two or more of said transmission lines are connected in parallel to at least one said electrode.

7. A multiple electrode plasma reactor as described in claim 1 wherein at least two of said electrodes are connected electrically in parallel, are closely spaced inside the reactor so as to function as a single large area having a uniform plasma over the surface of the area, and are separated by a gap that is small enough to inhibit the formation of a plasma between said electrodes.