Dismiss
InnovationQ will be updated on Sunday, Oct. 22, from 10am ET - noon. You may experience brief service interruptions during that time.
Browse Prior Art Database

Circular Terminal Polyimide Vias for Wirebond Products

IP.com Disclosure Number: IPCOM000111190D
Original Publication Date: 1994-Feb-01
Included in the Prior Art Database: 2005-Mar-26
Document File: 2 page(s) / 37K

Publishing Venue

IBM

Related People

Balbo, G: AUTHOR [+2]

Abstract

Disclosed is a special design for wet-etched vias in polyimide terminal passivation layer on wire bond products. Current vias design involve square/rectangular vias which allow wire bonding on the terminal metallurgy layer. From manufacturing experience, the following problems may occur which are a direct consequence of this square design :

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 96% of the total text.

Circular Terminal Polyimide Vias for Wirebond Products

      Disclosed is a special design for wet-etched vias in polyimide
terminal passivation layer on wire bond products.  Current vias
design involve square/rectangular vias which allow wire bonding on
the terminal metallurgy layer.  From manufacturing experience, the
following problems may occur which are a direct consequence of this
square design :

1.  Cracking of the polyimide film at one or more corners of the
    etched via.  This is the result in part of the action of the
    developer and in part of the stress concentration created at the
    corners.

2.  Delamination of the underlaying square metal pad in case of
    polyimide overetching.  The uncovered metal pad may lift from the
    underlaying structure due to stress effects and adhesion
    problems.

The circular via designs are the way to eliminate these problems (see
photograph):

1.  They are free from stress concentration sites, and are therefore
    not submitted to cracking effects under normal process
    conditions.

2.  They avoid terminal metal delamination since the circular design
    holds the pads even upon significant overetching.  This ensures a
    mechanical cohesion of the pad/via structure over a large etch
    process window.

      Edge cracks and pad delamination are reliability concerns for
inte- grated circuits.  Cracks can expose the underlaying metal
signal lines to corrosion; delamin...