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Improved Process Sequence for Fabricating Memory Cell Surface Straps

IP.com Disclosure Number: IPCOM000101891D
Original Publication Date: 1990-Sep-01
Included in the Prior Art Database: 2005-Mar-17
Document File: 2 page(s) / 61K

Publishing Venue

IBM

Related People

Duncan, BF: AUTHOR [+4]

Abstract

A semiconductor process sequence is shown which can be used to limit films to only horizontal surfaces while eliminating them from vertical structures. It can also be used in conjunction with masking layers to correct for re-entrant resist profiles.

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 81% of the total text.

Improved Process Sequence for Fabricating Memory Cell Surface Straps

       A semiconductor process sequence is shown which can be
used to limit films to only horizontal surfaces while eliminating
them from vertical structures. It can also be used in conjunction
with masking layers to correct for re-entrant resist profiles.

      A current process sequence for fabricating memory cell surface
straps results in problems of image overhang caused by reflections. A
new process sequence selectively removes material from sidewalls but
leaves it on horizontal surfaces or small steps where a strap is to
be formed, using the maximum horizontal image width for strap
formation.

      The process sequence follows:
Step 1.
On top of a polysilicon film covering an underlying topography,
deposit a thin layer of non-conformal masking material.
(Non-conformal implies a thinner film on sidewalls than on horizontal
surfaces.) The minimum film thickness is determined by the percent
coverage and the selectivity to the covering layer by the etch to
follow, as well as required step height coverage.
Step 2.
Define image using standard photo techniques.
Step 3.
Anisotropically dry etch the film deposited in step 1.
Step 4.
Strip photoresist.
Step 5.
Etch out the non-conformal film deposited in step 1 isotropically.
This will eliminate the film on the vertical sidewalls only, leaving
the film on the horizontal surfaces. The etch at this point will not
come into contact with any surface...