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Enhanced performance bipolar transistor process

  • US 5,369,042 A
  • Filed: 03/05/1993
  • Issued: 11/29/1994
  • Est. Priority Date: 03/05/1993
  • Status: Expired due to Term
First Claim
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1. A method of forming complementary NPN and PNP bipolar transistors comprising:

  • a. forming a n-type subcollector layer, having a doping concentration, on a substrate;

    b. forming a n-type first layer, of a lower doping concentration than said subcollector layer, over said subcollector layer;

    c. increasing said doping concentration of first and second regions of said first layer in an NPN transistor area;

    d. counter-doping portions of said n-type subcollector and said n-type first layer, thereby forming a p-type subcollector in a PNP transistor area;

    e. forming a n-type second layer, of a lower doping concentration than said n-type subcollector layer, over said first layer;

    f. increasing said doping concentration of a first region of said second layer which is over said first region of said first layer, whereby said subcollector layer, said first region of said first layer, and said first region of said second layer are a collector of an NPN transistor;

    g. counter-doping a second region of said second layer in said PNP portion of said transistor, whereby said p-type subcollector and said second region of said second layer are a collector of a PNP transistor;

    h. forming a n-type base layer over said second layer in said PNP transistor area;

    i. forming a p-type emitter layer over said n-type base layer;

    j. forming a p-type base layer over said second layer in said NPN transistor area; and

    k. forming an n-type emitter layer over said p-type base layer.

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