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Self Aligned, Borderless Polysilicon Contacts using Polysilicon Pillars

IP.com Disclosure Number: IPCOM000109099D
Original Publication Date: 1992-Jul-01
Included in the Prior Art Database: 2005-Mar-23
Document File: 4 page(s) / 127K

Publishing Venue

IBM

Related People

Stanasolovich, D: AUTHOR [+2]

Abstract

Polysilicon borders are frequently used to protect electrical integrity over thick oxide regions when alignment errors between first level metal contacts to polysilicon occur. If perfect alignment could be reliably achieved, polysilicon borders would not be required.

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Self Aligned, Borderless Polysilicon Contacts using Polysilicon Pillars

       Polysilicon borders are frequently used to protect
electrical integrity over thick oxide regions when alignment errors
between first level metal contacts to polysilicon occur.  If perfect
alignment could be reliably achieved, polysilicon borders would not
be required.

      This article describes a process for achieving self-aligned
polysilicon contacts using polysilicon contacts which eliminate the
need for polysilicon borders:

      First, a composite composed of successive layers of
polysilicon, silicon nitride, polysilicon, silicon nitride, and
silicon dioxide is covered by a photoresist layer, as shown in Fig.
1.  The photoresist layer is then exposed by a stepper expose tool
using two reticles at different exposure energies.  A reticle
management system (RMS) is used to align the reticles to each other
within 0.025 um.  The field areas where no polysilicon should be
present in the finished product are exposed to a high dose of energy.
Those areas where the polysilicon lines to be fabricated are exposed
to a moderate dose, and those areas where a polysilicon pillar is to
be placed are not exposed at all.

      After the resist is developed, the silicon oxide and silicon
nitride are etched in the field areas in a CHF3/O2 plasma.  The etch
conditions are chosen so that the passivation layers etch much more
quickly than the photoresist.  The resulting structure is depicted in
Fig. 2.

      Next, the resist is etched in an O2 RIE such that all the
re...