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Method of making high performance bipolar transistor with polysilicon base contacts

  • US 4,319,932 A
  • Filed: 03/24/1980
  • Issued: 03/16/1982
  • Est. Priority Date: 03/24/1980
  • Status: Expired due to Term
First Claim
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1. A process for fabricating NPN bipolar transistors having a self-aligned polysilicon base contact in close-spaced relationship to the emitter contact therefor, comprising the following sequence of steps;

  • forming a layer of P+ doped polysilicon on a substrate at least a portion of which is an N-type silicon material;

    forming a layer of insulating material over said layer of P+ doped polysilicon;

    etching said layer of insulating material and polysilicon down to said N-type material to form an opening therethrough;

    forming a thin layer of insulating material on said N-type material at the bottom of said opening and along the sidewalls of said polysilicon layer exposed by said opening;

    diffusing the P+ doping material from said polysilicon layer into said N-type silicon material to form an extrinsic base region;

    etching by directional reactive ion etching the said thin layer of insulating material at the bottom of said opening as delineated by said sidewalls so as to remove the said insulating material at the bottom of said opening while leaving said insulating material on said sidewalls;

    forming through said opening with insulating sidewalls an intrinsic P-type base region therebelow; and

    forming through said opening with insulating sidewalls an N-type region above said intrinsic P-type base region, said N-type region forming a shallow N-type emitter.

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