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Reducing Stresses in Asymmetrical Studs on Silicon Chips Using Sacrificial Studs

IP.com Disclosure Number: IPCOM000109470D
Original Publication Date: 1992-Aug-01
Included in the Prior Art Database: 2005-Mar-24
Document File: 1 page(s) / 53K

Publishing Venue

IBM

Related People

Shi, LT: AUTHOR [+2]

Abstract

Disclosed is a modified design of asymmetric studs, which connect conductive metal lines in different layers and locate at the end of metal lines. The design can significantly reduce the imposed thermal stresses so that the stud failure can be dramatically decreased. (Image Omitted)

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Reducing Stresses in Asymmetrical Studs on Silicon Chips Using Sacrificial Studs

      Disclosed is a modified design of asymmetric studs, which
connect conductive metal lines in different layers and locate at the
end of metal lines.  The design can significantly reduce the imposed
thermal stresses so that the stud failure can be dramatically
decreased.

                            (Image Omitted)

      It has been constantly observed that in computer chips the
studs at the end of the conductive (metal) lines suffer much more
failure than those in the middle of the lines.  It has been
determined that the stud failure is caused by a stress-induced and
thermally activated process.  A finite-element stress analysis showed
that the stress in the stud 1 at the end of the line as shown
in the figure are about 40-90% higher than those in the stud 2 in the
middle of the line as a result of geometrical asymmetry.  Hence
adding a dummy stud 3 to the stud 1 at the end of the metal
line can dramatically reduce the magnitude of the resulted thermal
stresses in the stud 1 so that the life time of the stud is
significantly increased.  Since the stresses in the dummy stud 3 are
not reduced (based on the calculation), the dummy stud is prone to
fail in a quicker rate and is therefore named "sacrificial" stud.
However, the existence of the dummy or sacrificial stud 3 will
definitely prolong the life expectancy of the active stud 1 for more
than one to...