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Enhanced performance bipolar transistor process

  • US 5,407,842 A
  • Filed: 06/08/1994
  • Issued: 04/18/1995
  • Est. Priority Date: 03/05/1993
  • Status: Expired due to Term
First Claim
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1. A method of forming a bipolar transistor comprising:

  • a. forming a subcollector layer, having a doping type and a doping level, on a substrate;

    b. forming a first layer, of the same doping type and a lower doping level than said subcollector layer, over said subcollector layer;

    c. increasing the doping level of first and second regions of said first layer;

    d. forming a second layer, of the same doping type and a lower doping level than said subcollector layer, over said first layer;

    e. increasing the doping level 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 the collector of the transistor;

    f. forming a base layer over said second layer of an opposite doping type than said subcollector layer; and

    g. forming an emitter layer of the same doping type as said subcollector layer over said base layer.

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