Publication: Improvement of cu-al bond integrity on low k pad structures
Date
2011
Authors
Ooi Xin Yi
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Abstract
Since 1950's, Gold wire-bonding has been introduced into the field of interconnection of ICs and it becomes the main interconnection process in the semiconductor packaging industry. Gold wires are commonly used for wire-bonding and it fits well the industrial requirements. However, the price of Gold wires increasing significantly, Copper wires is a potential replacement for Gold due to their superior electrical and mechanical properties. In general, Cu-Al intermetallics have better electrical and thermal qualities than Cu-Al intermetallics. In order to incorporate Cu in the wire- bonding process, substantial data regarding aging and intermetallic formation of Cu- Al bonds is required and the results are compared with Au samples. In this study, the bond integrity and thermal aging of Cu-Al and Au-Al wire-bonds were investigated. The Copper and Gold wire-bonds samples were heat-treated at 175°C for 168, 504 and 1008 hours while at temperature of 225°C for 4.5, 13.5, 26, 52 and 97 hours respectively. The intermetallics of the wire-bonds, and in particular the Al-Cu interface, were studied. Discontinuous and non-uniform of Cu-Al intermetallics regions were found in the thermal aging samples. The thickness of Cu-Al intermetallics is growing linearly with the temperature as the diffusion rate increases in higher temperature. The Cu-Al bond is weak compare to Au-Al in accordance with aging through wire pull test.
Description
TS270.O54 2011
Keywords
Copper wire