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Fast transition RF impedance matching network for plasma reactor ignition

  • US 5,815,047 A
  • Filed: 11/27/1995
  • Issued: 09/29/1998
  • Est. Priority Date: 10/29/1993
  • Status: Expired due to Fees
First Claim
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1. An impedance matching network for an RF plasma reactor having RF excitation apparatus receiving RF power through said impedance matching network from an RF generator to ignite and maintain a plasma in said reactor, and presenting a plasma impedance to said impedance matching network, said network comprising:

  • a current path including an input conductor connectable to said RF generator and an output conductor connectable to said RF excitation apparatus;

    a common return connection;

    at least one vacuum variable capacitor connected between said current path and said common return connection and having a variable capacitance value corresponding to a match to said plasma impedance during a steady state of said plasma;

    at least a first air variable capacitor connected in parallel with said at least one vacuum variable capacitor, said first air variable capacitor being switchable between a high capacitance value providing a match to said plasma impedance during an onset of plasma ignition, and a negligible capacitance value with respect to said high capacitance value; and

    means coupled to said first air variable capacitor for setting said first air variable capacitor to said high capacitance value prior to ignition of said plasma in said reactor and for switching said first air variable capacitor from said high to said negligible capacitance value upon said plasma reaching said steady state.

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