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Narrow Basewidth Advanced Transistor without Reoxidation

IP.com Disclosure Number: IPCOM000103025D
Original Publication Date: 1990-May-01
Included in the Prior Art Database: 2005-Mar-17
Document File: 1 page(s) / 41K

Publishing Venue

IBM

Related People

Habitz, PA: AUTHOR [+2]

Abstract

For an advanced bipolar transistor, the process of reoxidation after intrinsic base on implantation causes a large variation in base width and integrated base doping. Although the reoxidation is by low temperature and high pressure, about one-half of the implanted boron segregates into the oxide layer of about 500A. During this same step, the base width increases drastically due to oxidation enhanced diffusion.

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Narrow Basewidth Advanced Transistor without Reoxidation

      For an advanced bipolar transistor, the process of reoxidation
after intrinsic base on implantation causes a large variation in base
width and integrated base doping. Although the reoxidation is by low
temperature and high pressure, about one-half of the implanted boron
segregates into the oxide layer of about 500A.  During this same
step, the base width increases drastically due to oxidation enhanced
diffusion.

      We have proposed a process of substituting the base reoxidation
step by plasma enhanced chemical vapor deposited (PECVD) oxide.  The
quality of this PECVD oxide has proved to be as good as the thermally
grown oxide.  However, we have to redesign the sidewall structure in
order to guarantee isolation between the extrinsic base polysilicon
and the emitter polysilicon layers.

      After emitter window opening:
           A 300A thermal oxide is grown
           A 300A silicon nitride layer is deposited
           Anisotropic RIE 300A of Si3N4
           Strip 300A oxide by 10:1 DHF etch
           Intrinsic Base Ion-Implant
           Intrinsic Base Anneal
           500A PECVD oxide is deposited
           800A Sidewall Si3N4 is deposited
           1,000A TEOS is deposited and annealed
           Sidewall RIE: 1000A TEOS and 800A Si3N4
           Strip oxide

      The...