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Polyimide Vias With Nitride Sidewall Structure for Improved Tungsten Fill

IP.com Disclosure Number: IPCOM000103242D
Original Publication Date: 1990-Aug-01
Included in the Prior Art Database: 2005-Mar-17
Document File: 1 page(s) / 39K

Publishing Venue

IBM

Related People

Chow, M: AUTHOR [+3]

Abstract

Using polyimide as a dielectric to replace oxide or quartz has provided many advantages: (1) low dielectric constant, (2) infinite dry etch selectivity to substrate, (3) inert to HF clean and (4) less cost.

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Polyimide Vias With Nitride Sidewall Structure for Improved Tungsten Fill

      Using polyimide as a dielectric to replace oxide or quartz has
provided many advantages:  (1) low dielectric constant, (2) infinite
dry etch selectivity to substrate, (3) inert to HF clean and (4) less
cost.

      When polyimide vias were filled by using a selective tungsten
process, however, a so-called "creep-up" effect was often observed.
This creep-up phenomenon, or sidewall W growth rate enhancement,
although not well understood, is postulated to be caused by reaction
between tungsten and polyimide outgassing during tungsten deposition.
A severe creep-up if it occurs inside a small via, will degrade
filling quality and eventually lead to stud failure.

      To avoid such a creep-up, a technique of using sidewall nitride
or oxide spacer is proposed.  After polyimide via etch, a thin layer
of PECVD nitride/oxide is deposited and etched back to open the
bottom of the via.  The purpose of this is to prevent direct contact
between tungsten and polyimide.  As a result, W-polyimide reaction is
avoided and a creep-free deposition is achieved.  Also, because
polyimide is completely sealed by nitride on the sidewalls and a
surface barrier layer, chance for further moisture absorption are
minimal, and interconnect reliability is greatly improved.  The above
scheme is incorporated in the via structure and is experimentally
well demonstrated.

      Disclosed anonymously.