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Method for fabricating a concave bottom oxide in a trench

  • US 6,265,269 B1
  • Filed: 08/06/1999
  • Issued: 07/24/2001
  • Est. Priority Date: 08/04/1999
  • Status: Expired due to Term
First Claim
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1. A method for forming a concave bottom oxide layer in a trench, comprising:

  • providing a semiconductor substrate;

    forming a pad oxide layer on said semiconductor substrate;

    forming a silicon nitride layer on said pad oxide layer;

    etching said silicon nitride layer, said pad oxide layer and said semiconductor substrate to form said trench in said semiconductor substrate;

    depositing a silicon oxide layer to refill into said trench and cover on said silicon nitride layer, wherein said silicon oxide layer has overhang portions at the silicon nitride corners of said trench;

    anisotropically etching said silicon oxide layer to form a concave bottom oxide layer in said trench;

    etching said silicon oxide layer to remove said silicon oxide layer on said silicon nitride layer and on sidewalls of said trench; and

    removing said silicon nitride layer and said pad oxide layer.

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