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Integrated process for fabricating raised, source/drain, short-channel transistors

  • US 5,312,768 A
  • Filed: 03/09/1993
  • Issued: 05/17/1994
  • Est. Priority Date: 03/09/1993
  • Status: Expired due to Term
First Claim
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1. In a partially completed, N-channel MOSFET device having a gate structure, a pair of oxide spacers adjacent the gate structure, a pair of silicon nitride barrier spacers adjacent the oxide spacers, a doped source and drain area over a P-well in a substrate, and a field oxide layer adjacent the source and drain area, a process for completing fabrication of a raised source/drain N-channel MOSFET device comprising the steps of:

  • a growing a second field oxide layer over the source and drain areas;

    b. selectively etching the silicon nitride barrier spacers, thereby exposing a narrow source and drain area between the oxide spacer and the second field oxide layer;

    c. depositing a transition metal nitride layer over the MOSFET device;

    d. depositing a polysilicon layer over the metal nitride layer; and

    simultaneouslye. in situ doping the polysilicon layer to create a conducting polysilicon layer, wherein the transition metal nitride layer acts as a barrier to ion migration to the source and drain areas;

    f. etching the polysilicon layer to form an opening over the gate structure and a boundary over the field oxide layer wherein the metal nitride layer acts as an etch barrier;

    g. etching the transition metal nitride layer to form openings over the gate structure and a boundary over the field oxide layer, thereby forming a raised source/drain electrical connection;

    h. depositing an oxide isolation layer over the MOSFET device;

    i. patterning and etching a pair of contact openings in the oxide isolation layer over the conducting polysilicon wherein the nitride layer acts as an etch barrier;

    j. depositing a thin titanium nitride layer within the contact openings;

    k. depositing and patterning a metal conductor within the contact opening; and

    thenl. depositing and patterning a pair of bit line metal conductors over the metal conductor in the contact opening thereby providing a low-resistance electrical connection from the bit line through the raised source/drain electrical connection to the narrow source and drain areas.

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