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Oxide strip that improves planarity

  • US 5,766,971 A
  • Filed: 12/13/1996
  • Issued: 06/16/1998
  • Est. Priority Date: 12/13/1996
  • Status: Expired due to Term
First Claim
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1. A method of making an integrated circuit in a silicon substrate having a set of transistors formed in active areas of said substrate and interconnections therebetween, comprising the steps of:

  • preparing said substrate, including forming a pad oxide thereon;

    etching at least one isolation trench about at least one active area;

    filling said at least one isolation trench with fill oxide and removing excess fill oxide outside said at least one isolation trench, thereby forming a composite layer of oxide containing said pad oxide and said fill oxide meeting at at least one oxide interface having interface sidewalls;

    etching said composite layer of oxide by reacting said composite layer of oxide with HF in a vacuum to form a first reaction product, said first reaction product containing a removal amount of Si, having a first volume, removed from said layer of oxide;

    reacting said first reaction product with NH3 in said vacuum to form a second reaction product in situ, said second reaction product having a second volume substantially greater than said first volume, said second reaction product also being substantially resistant to diffusion of HF, whereby said etching step is self-limiting;

    continuing said step of reacting said oxide with HF until said pad oxide thickness is removed;

    removing said second reaction product;

    forming transistors in said active areas; and

    interconnecting said transistors to form said integrated circuit.

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