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Method for preventing to form a spacer undercut in SEG pre-clean process

  • US 6,991,991 B2
  • Filed: 11/12/2003
  • Issued: 01/31/2006
  • Est. Priority Date: 11/12/2003
  • Status: Active Grant
First Claim
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1. A method for preventing to form a spacer undercut in SEG Pre-clean process, comprising:

  • providing a semiconductor substrate;

    forming a gate structure on said semiconductor substrate;

    forming a spacer of double-film structure on a side-wall of said gate structure, wherein said spacer of double-film structure comprises a first spacer and a second spacer, said first spacer being formed between said side-wall of said gate structure and said second spacer;

    removing a portion of a surface of said semiconductor substrate by using a DHF (hydrofluoric acid diluted in deionized water) solution to remove a native oxide layer on said surface of said semiconductor substrate; and

    etching said first spacer and said second spacer, wherein an etching rate of said second spacer is faster than an etching rate of said first spacer.

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