Observation of stress-induced voiding with an ultra-high voltage electron microscope

An investigation of stress-induced voiding at temperatures 400 to 500 degrees C in passivated Al metallizations (0.5 by 1 mu m wide) with a bamboo grain structure by ultra-high voltage (2 MV) electron microscopy is discussed. Emphasis is placed on the study of nucleation and growth of voids. Conventional and in situ observations of initial stages of voiding indicate that voids start not only at grain boundaries (GBs), but also at passivation/Al interfaces with no GBs. Void growth toward the Al metallization with direction, however, is always associated with GBs. From the observed results it is suggested that dislocation glide as well as GBs may play a role in voiding at the temperature range studied.<
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