Browse Prior Art Database

Local Nitride Spacer to Prevent Silicon Oxidation

IP.com Disclosure Number: IPCOM000114283D
Original Publication Date: 1994-Dec-01
Included in the Prior Art Database: 2005-Mar-28
Document File: 2 page(s) / 94K

Publishing Venue

IBM

Related People

Coronel, P: AUTHOR [+2]

Abstract

Disclosed is the formation of local nitride spacers on vertical surfaces of a silicon substrate to prevent subsequent oxidation thereof. The spacers are made from deposition of a thin nitride layer followed by a selective plasma etching.

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Local Nitride Spacer to Prevent Silicon Oxidation

      Disclosed is the formation of local nitride spacers on vertical
surfaces of a silicon substrate to prevent subsequent oxidation
thereof.  The spacers are made from deposition of a thin nitride
layer followed by a selective plasma etching.

      The purpose of this process is to cover a vertical surface of
silicon which is exposed after a plasma oxide etching.  As shown in
Fig. 1, a vertical region of silicon (shadow area) under the gate
spacer is left bare after plasma etching.  During subsequent
processing steps, this area can be oxidized leading to local stresses
which could generate dislocations into the silicon substrate.
  The protecting nitride layer is formed according to a two step
process:
  Step 1: Plasma Assited CVD deposition of 25 nm of silicon
           nitride on the wafer.  Silicon nitride is conformally
           deposited and covers the entire wafer.
  Step 2: Selective silicon nitride etching in a CHF3/O2 plasma
           with in-situ end point detection to automatically stop
           the process at the end of the etching.  (Optical end
           point wavelength=25nm, N2 line).

      With the above described process sequence, the nitride layer
remains in situ and perfectly protects the underlying silicon
material from oxidation (Fig. 2).

      This technique shows that it is possible to create a local and
specific pro...