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Post gate etch cleaning process for self-aligned gate mosfets

  • US 6,242,350 B1
  • Filed: 03/18/1999
  • Issued: 06/05/2001
  • Est. Priority Date: 03/18/1999
  • Status: Expired due to Term
First Claim
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1. A method for stripping photoresist and cleaning polymer residues from a silicon wafer after plasma etching of a gate electrode comprising:

  • (a) providing a silicon wafer having;

    (i) a gate oxide;

    (ii) a conductive layer overlying said gate oxide;

    (iii) a photoresist layer overlying said conductive layer and patterned to define a gate electrode;

    (b) plasma etching said conductive layer to form a gate electrode;

    (c) loading said wafer into an ashing chamber of a plasma asher;

    (d) ashing said photoresist and said polymer residues by the steps of;

    (i) flowing oxygen in said chamber at for a first time period;

    (ii) flowing a first gas mixture containing oxygen and nitrogen in said chamber while initiating and maintaining a gas plasma in said chamber at a first rf power for a second time period;

    (iii) flowing a second gas mixture containing oxygen and nitrogen in said chamber while maintaining a gas plasma in said chamber at a second rf power for a third time period;

    (iv) flowing a third gas mixture containing oxygen and a fluorine containing gas in said chamber while maintaining a gas plasma in said chamber at a third rf power for a fourth time period;

    (v) flowing a fourth gas mixture containing oxygen and nitrogen in said chamber for a fifth time period;

    (e) retrieving said wafer from said plasma asher; and

    (f) rinsing said wafer in de-ionized water and drying said wafer.

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