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Radio frequency monitor for semiconductor process control

  • US 5,467,013 A
  • Filed: 12/07/1993
  • Issued: 11/14/1995
  • Est. Priority Date: 12/07/1993
  • Status: Expired due to Fees
First Claim
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1. A radio frequency (RF) sensor, coupled to a transmission line disposed between a plasma reactor and an electrical source providing RF voltage and current to said plasma reactor, for monitoring said RE voltage and current on said transmission line comprising:

  • a first capacitance coupled between a first node and said transmission line;

    a second capacitance coupled between said first node and a second node;

    said first and second capacitances providing a capacitive voltage divider network wherein a first voltage output at said first node is a proportional representation of said RF voltage on said transmission line;

    a wire loop disposed next to said transmission line at a point on said transmission line where said first capacitance is coupled but having an air gap between said loop and said transmission line, such that electromagnetic field lines generated by current flow in said transmission line is inductively coupled to said loop, wherein voltage induced in said loop by said current flow provides a second voltage output which is a proportional representation of said RF current on said transmission line;

    an electromagnetic shielding, disposed around said first and second capacitances, inhibits electromagnetic interference from interacting with said first and second capacitances which interference can cause erroneous first voltage output at said first node;

    said first and second voltage outputs providing for accurate measurement of said RF voltage and current and said measurement is also used to accurately determine a phase relationship between said RF voltage and current.

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