Browse Prior Art Database

Postsloped Vias

IP.com Disclosure Number: IPCOM000099519D
Original Publication Date: 1990-Jan-01
Included in the Prior Art Database: 2005-Mar-15
Document File: 3 page(s) / 70K

Publishing Venue

IBM

Related People

Koblinger, O: AUTHOR [+3]

Abstract

By a) transfer of a photolithographically defined angle in a steep photoresist to the insulation layers polyimide/nitride without enlargement by dry etching and b) subsequent resist reflow and transfer of that angle to the polyimide by dry etching, vias with very small tolerances, small dimensions and soft angles are obtained. The method requires only one photolithographic step instead of two as previously.

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Postsloped Vias

       By a) transfer of a photolithographically defined angle in
a steep photoresist to the insulation layers polyimide/nitride
without enlargement by dry etching and b) subsequent resist reflow
and transfer of that angle to the polyimide by dry etching, vias with
very small tolerances, small dimensions and soft angles are obtained.
 The method requires only one photolithographic step instead of two
as previously.

      A process for producing vias with slope control starts by
applying the photoresist, followed by imagewise exposure and
development.  After the substrates have been introduced into an RIE
system, about two- thirds of the polyimide is etched by CF4, while
the remainder is etched to end point by O2 .  Then, about 60% of the
nitride is etched by CF4 . Lateral ashing of polyimide and resist in
O2 produces a double step.  A soft O2 etch step removes the "skin"
from the photoresist, which is a prerequisite for a good resist
reflow.  Another prerequisite for a good reflow is that the nitride
via must not be opened down to the metal before reflowing the resist.
 Reflowing is effected by heating on a hot plate, followed by
transfer of the resist angle to the polyimide by O2 RIE.  The
remaining nitride layer is etched by CF4 RIE.  Then, a further soft
etch step is implemented which permits wet resist stripping.
Finally, the photoresist is stripped in N-methylpyrrolidone.  The
parameters for the individual steps may be seen from the e...