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Supression of Purple Plague Growth in Gold-Aluminum Interconnections

IP.com Disclosure Number: IPCOM000119465D
Original Publication Date: 1991-Jan-01
Included in the Prior Art Database: 2005-Apr-01
Document File: 1 page(s) / 54K

Publishing Venue

IBM

Related People

Kang, SK: AUTHOR

Abstract

Disclosed is an interconnection metallurgy for gold-aluminum system. The formation of the various intermetallic phases, especially the so-called "purple plague," AuA12 phase, has long been a concern due to the reliability of the interconnections. The growth of the intermetallic phases is also known to induce a void layer underneath the intermetallics, which would worsen the problem. Generally speaking, suppression of the intermetallic growth, if possible, would be beneficial to the integrity/ reliability of the interconnections.

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Supression of Purple Plague Growth in Gold-Aluminum Interconnections

      Disclosed is an interconnection metallurgy for gold-aluminum
system.  The formation of the various intermetallic phases,
especially the so-called "purple plague," AuA12 phase, has long been
a concern due to the reliability of the interconnections.  The growth
of the intermetallic phases is also known to induce a void layer
underneath the intermetallics, which would worsen the problem.
Generally speaking, suppression of the intermetallic growth, if
possible, would be beneficial to the integrity/ reliability of the
interconnections.

      Silicon wafers were processed to have different Al
metallizations; pure Al and Al-Cu alloys with a copper content up to
5 weight percent.  The Al metallization had a thickness of 2 mm.  A
thin chromium layer, 500 A, was deposited prior to aluminum as an
adhesion layer.  Copper coupons of 50 mm thick were gold
electroplated to have a thickness of 2 mm.  The gold plated coupons
were then bonded to the aluminum metallized silicon chips at 500oC, 5
sec, 2,000 psi.  Some of the bonded specimens were heat treated in
nitrogen at 150oC, up to 300 h.  Both the as-bonded and heat-treated
specimens were cross-sectioned and polished to reveal the growth of
the gold-aluminum intermetallics at their bonding interface.

      The identification of the intermetallic layers was achieved by
using various analytical techniques, such as electron microprobe
analysis,...