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System for providing variable capacitance

  • US 10,431,428 B2
  • Filed: 06/29/2017
  • Issued: 10/01/2019
  • Est. Priority Date: 01/10/2014
  • Status: Active Grant
First Claim
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1. A radio frequency (RF) impedance matching network comprising:

  • an RF input configured to operably couple to an RF source;

    an RF output configured to operably couple to a plasma chamber having a variable impedance;

    electronically variable capacitors (EVCs) each comprising discrete capacitors operably coupled in parallel, the discrete capacitors comprising;

    fine capacitors each having a capacitance value substantially similar to a fine capacitance value; and

    coarse capacitors each having a capacitance value substantially similar to a coarse capacitance value, the coarse capacitance value being greater than the fine capacitance value;

    wherein each EVC has a variable total capacitance that is increased when the discrete capacitors are switched in and decreased when the discrete capacitors are switched out; and

    a control circuit operably coupled to the EVCs, the control circuit configured to determine the variable impedance of the plasma chamber;

    the control circuit further configured to;

    determine, based on the determined variable impedance, a total number of coarse capacitors of the coarse capacitors to have switched in;

    determine, based on the determined variable impedance, a total number of fine capacitors of the fine capacitors to have switched in; and

    cause an impedance match by causing the total number of coarse capacitors and the total number of fine capacitors to be switched in;

    wherein the increase of the variable total capacitance of each EVC is achieved by switching in more of the coarse capacitors or more of the fine capacitors than are already switched in without switching out a coarse capacitor that is already switched in.

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