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Sidewall Structure for Enhanced FETs

IP.com Disclosure Number: IPCOM000122763D
Original Publication Date: 1991-Dec-01
Included in the Prior Art Database: 2005-Apr-04
Document File: 1 page(s) / 45K

Publishing Venue

IBM

Related People

Hovel, HJ: AUTHOR

Abstract

Disclosed is a structure consisting of thick sidewalls on FETs needed for low short channel effects coupled with a thin throughcap implant layer for n+ source and drain implants. The structure is most suitable for enhanced GaAs MESFETs or FETs made from other III-V materials, including InP and InGaAs.

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Sidewall Structure for Enhanced FETs

      Disclosed is a structure consisting of thick sidewalls on FETs
needed for low short channel effects coupled with a thin throughcap
implant layer for n+ source and drain implants.  The structure is
most suitable for enhanced GaAs MESFETs or FETs made from other III-V
materials, including InP and InGaAs.

      A FET made from a III-V compound, such as GaAs, is processed up
to the Gate level using any of several well-known process sequences.
Thick sidewalls along the sides of the gate are then applied which
act as the "stand-off" for the self-aligned sourcedrain implants.
Such sidewalls are typically produced by CVD deposition of a
dielectric layer 1000-4000 Ao thick followed by reactive ion etching
down to the GaAs surface.  Next a thinner dielectric layer is
deposited, thin enough (200 - 700 Ao) that donor ion implantation can
be carried out through this layer at relatively low implant energies
(30-75 keV instead of 150-200 keV for thicker layers).  The thin
second dielectric layer and low implant energy aid in producing low
implant straggling and reduced short channeling while still
protecting the GaAs surface during the implant for low device leakage
currents.  The thick sidewall is also crucial for standing-off the n+
implant from underneath the gate region and, therefore, minimizing
short channel effects.

      The thin oxide can also be used as the cap layer for capped
annealing of the implant, or can be left...