Browse Prior Art Database

Methods for Repairing Voids in Buried or Passivated Circuits

IP.com Disclosure Number: IPCOM000106559D
Original Publication Date: 1993-Nov-01
Included in the Prior Art Database: 2005-Mar-21
Document File: 2 page(s) / 63K

Publishing Venue

IBM

Related People

Dreyfus, RW: AUTHOR [+3]

Abstract

There are many instances where voids are formed in Al lines during fabrication which may only be discovered after passivation with a layer of SiO&sub2. or polyimide. The problem at hand is how to repair these voids before they open up in the 'field'. What is needed is either to close the void to eliminate the thinned region of the electrical line or a method for adding metal or a conducting material to the void without disturbing the otherwise intact circuit.

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This is the abbreviated version, containing approximately 52% of the total text.

Methods for Repairing Voids in Buried or Passivated Circuits

      There are many instances where voids are formed in Al lines
during fabrication which may only be discovered after passivation
with a layer of SiO&sub2.  or polyimide.  The problem at hand is how
to repair these voids before they open up in the 'field'.  What is
needed is either to close the void to eliminate the thinned region of
the electrical line or a method for adding metal or a conducting
material to the void without disturbing the otherwise intact circuit.

      The two solutions of this invention relate specifically to
circuits containing micron-sized wiring, consisting of Al in
particular though the concepts are not limited to that metallurgy or
small wiring dimensions.  Both proposed schemes use  directed laser
energy but in a manner uniquely different from those previously
described in the open and patent literature lbrk 1-3 rbrk.  A major
distinction between the present and the earlier work is that our
methods do not require the removal of the passivation layer to
implement repair of the defect.

      The first method consists in accessing the defective line with
a focused short pulsed laser, with one or more pulses in the range
10-1000 ns.  The laser wavelength is selected to have little or no
absorption in the overlay, here SiO&sub2.  (on the order of 1 micron
in thickness) but some absorption in the Al (or circuit line).  Argon
or Q switched frequency doubled YAG lasers would be suitable.  The
line defect consists of a void, typically described as a small hole
in the line but one which does not make the line electrically
discontinuous.  The absorbed laser energy causes local melting of the
Al.  Since the line is in compression, the void will be filled in
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