Plasma process uniformity across a wafer by controlling RF phase between opposing electrodes

  • US 8,076,247 B2
  • Filed: 04/11/2007
  • Issued: 12/13/2011
  • Est. Priority Date: 01/30/2007
  • Status: Expired due to Fees
First Claim
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1. A method of processing a workpiece in a plasma reactor chamber, comprising:

  • coupling, to a plasma in the chamber, power of an RF frequency via a ceiling electrode and coupling, to the plasma, power of at least approximately the same RF frequency via a workpiece support electrode;

    providing an edge ground return path; and

    adjusting the proportion between (a) current flow through a center RF current path between said electrodes and (b) current flow to the edge ground return path from said electrodes, wherein said adjusting comprises;

    (a) determining non-uniformity of radial distribution of plasma ion density in said chamber,(b) performing one of;

    (i) responding to a center-high nonuniformity by reducing a phase difference between RF voltages or currents at said ceiling electrode and said workpiece support electrode,(ii) responding to an edge high nonuniformity by increasing a phase difference between RF voltages or currents at said ceiling electrode and said workpiece support electrode.

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