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Three-Step Polysilicon Gate Electrode Etch Process

IP.com Disclosure Number: IPCOM000103416D
Original Publication Date: 1990-Nov-01
Included in the Prior Art Database: 2005-Mar-17
Document File: 1 page(s) / 45K

Publishing Venue

IBM

Related People

Huynh, C: AUTHOR [+4]

Abstract

Etching parameters are changed three times within a reactive ion etch system to cleanly remove doped polysilicon (Si) without damaging underlying silicon dioxide (SiO2) and without creating a heavy oxide layer on the surface of photoresist which could require excessive hydrofluoric acid (HF) etch removal time before photoresist can be stripped. Though the process is especially useful in defining polysilicon gate conductor patterns, it can be used for etching any Si (doped or pure). The three basic steps are applicable within batch or single wafer systems.

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Three-Step Polysilicon Gate Electrode Etch Process

      Etching parameters are changed three times within a reactive
ion etch system to cleanly remove doped polysilicon (Si) without
damaging underlying silicon dioxide (SiO2) and without creating a
heavy oxide layer on the surface of photoresist which could require
excessive hydrofluoric acid (HF) etch removal time before photoresist
can be stripped. Though the process is especially useful in defining
polysilicon gate conductor patterns, it can be used for etching any
Si (doped or pure).  The three basic steps are applicable within
batch or single wafer systems.

      A first set of etching conditions is used to provide etch
chamber conditioning, moisture elimination, and to remove native
oxide (SiO2) from Si surfaces:
   Etch gas: BCl3  at an approximate rate of flow of 40 standard
cubic centimeters per second (sccm)
           System pressure: approximately 20 mTorr
           Substrate bias: -200 volts DC
           Time: approximately one minute

      A second set of conditions is used to remove most of the Si:
           Etch gas: HCl at 90 sccm + Cl2 at 30 sccm
           System pressure: approximately 15 mTorr
           RF power: approximately 650 watts, no DC bias

      A third set of conditions is used to assure complete, very
selective, removal of Si, e.g., "stringers", without damage to
exposed SiO2:
   Etch gas: O2 at 5 sccm +...