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Structure and process for buried bitline and single sided buried conductor formation

  • US 6,518,118 B2
  • Filed: 03/15/2001
  • Issued: 02/11/2003
  • Est. Priority Date: 03/15/2001
  • Status: Expired due to Fees
First Claim
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1. A method for formation of a trench capacitor cell having a single-sided buried conductor comprising:

  • providing a semiconductor substrate successively layered with first pad SiN, hardened oxide, and second pad SiN and having a trench etched therein;

    providing trench liner about an interior wall of said trench, said liner comprising a first SiN liner, an oxide liner and a second SiN liner, said second SiN liner being outermost relative to said first SiN liner and said oxide liner being between said first and second SiN liners;

    filling the trench with trench dielectric;

    pulling back said second pad SiN;

    conformally layering polysilicon over said second pad SiN;

    performing angled boron implantation into a portion of said conformal polysilicon on one side of said trench, wherein the implantation divides said trench into first and second sides;

    etching undoped polysilicon from above said first side of said trench;

    etching said dielectric from said first side of said trench to expose said first SiN liner;

    etching exposed first SiN liner from said first side of said trench;

    forming and recessing a buried bitline conductor layer in said first side of said trench;

    etching further exposed oxide liner and first SiN liner from said first side of said trench to form space for a polysilicon strap;

    forming a polysilicon strap in said space;

    forming trench top oxide over said polysilicon strap;

    etching exposed said second SiN liner from said first side of said trench to expose semiconductor surface;

    growing gate oxide on exposed semiconductor surface;

    forming gate conductor layer adjacent to said gate oxide;

    forming a dielectric layer over said gate conductor;

    depositing a blanket of SiN over said dielectric layer; and

    depositing a blanket of BSG.

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