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Adjustable dc bias control in a plasma reactor

  • US 5,605,637 A
  • Filed: 12/15/1994
  • Issued: 02/25/1997
  • Est. Priority Date: 12/15/1994
  • Status: Expired due to Fees
First Claim
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1. A plasma reactor with selectable direct current (dc) bias control, comprising:

  • a grounded reactor chamber having conductive walls;

    a grounded first electrode located in the chamber;

    a second electrode spaced apart from the first electrode, for supporting a workpiece to be processed in the reactor chamber;

    at least one inlet port for supplying process gases to the reactor chamber;

    at least one outlet port for evacuating gases from the chamber;

    a high-frequency power source connected between the second electrode and ground, to generate and sustain a plasma in the reactor chamber; and

    a plasma shield installed in the reactor chamber to prevent the plasma from reaching a portion of the reactor chamber;

    wherein the plasma shield has a plurality of narrow slits through it to permit the flow of process gases but not the plasma, the slits each having a cross-sectional area defined by a slit length dimension that is long relative to a slit width dimension, and the slits each having a length in the direction of gas flow that is also long relative to the slit width;

    and wherein the effective area of the grounded first electrode is reduced because the plasma is prevented from contacting the full extent of the chamber walls, and the reduced effective area results in a reduced dc bias on the second electrode.

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