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Method of Integrating Polysilicon Gate Nitride/Oxide Decoupling Capacitors

IP.com Disclosure Number: IPCOM000101239D
Original Publication Date: 1990-Jul-01
Included in the Prior Art Database: 2005-Mar-16
Document File: 2 page(s) / 61K

Publishing Venue

IBM

Related People

Chu, SF: AUTHOR [+2]

Abstract

A technique is described to integrate polysilicon gate nitride/oxide decoupling capacitors, as used in bipolar technology. Described is a method of applying a thin polysilicon film to protect the thin dielectric of the decoupling capacitor from damage during wet or dry etching processes and improve its yield and reliability.

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Method of Integrating Polysilicon Gate Nitride/Oxide Decoupling Capacitors

       A technique is described to integrate polysilicon gate
nitride/oxide decoupling capacitors, as used in bipolar technology.
Described is a method of applying a thin polysilicon film to protect
the thin dielectric of the decoupling capacitor from damage during
wet or dry etching processes and improve its yield and reliability.

      Generally, planar P-poly/nitride/oxide/n+Si structures are used
as the decoupling capacitors in bipolar circuits. Such structures
require the oxidation of the n+ silicon surface followed by low
pressure chemical vapor deposition (LPCVD) of a very thin nitride
layer.  However, this stacked dielectric must be removed from other
active areas where n-p-n and p-n-p transistors are fabricated.
Problems can occur in masking this thin dielectric in the capacitor
area by direct photoresist.  First, unhardened resist may not sustain
the chemical or dry etch for the removal of this thin nitride/oxide
film from the active areas.  Second, if the resist is hardened,
subsequent removal of this resist- masking layer will damage or etch
the thin nitride/oxide/film.  Third, the standard buffered
hydrofluoric (BHF) acid dip etch prior to graft (extrinsic) base
polysilicon deposition may further aggravate the nitride integrity.

      The concept described herein provides a simple method of
solving the above problems.  The method consists of depositing a thin
undoped...