Three-dimensional microanalysis of the wire-pad contact region of integrated circuits

We have developed a three-dimensional microanalyser by combination of a gal lium focused ion beam (Ga-FIB) a secondary electron detector and a time-of- flight (ToF) mass spectrometer, The Ga-FIB can create successive flat cross -sections parallel to the interface. We performed ToF-SIMS mapping by switc hing the d.c. mode of the Ga-FIB in the cross-sectioning to pulse mode afte r turning the cross-section through 90 degrees, Combination of these ToF ma ps on each cross-section yields detailed three-dimensional information from the interface region, The Au wire bonding interface after heat treatment w as analysed, Analysis of the three-dimensional elemental distribution in th e contact region of the Au wire and Al pad was realized, An Au-Al alloy was found in the deep section of the contact interface, Al was distributed in the outer part as a ring and the center part was enclosed by Au. The deduce d structure of the contact region of the Au wire and Al pad was discussed. Copyright (C) 2000 John Wiley & Sons, Ltd.