In situ transmission electron microscopy study of thermal-stress-induced dislocations in a thin Cu film constrained by a Si substrate

Thermal-stress-induced dislocation motion in a Cu film on an amorphous SiNx (a-SiNx) passivated Si substrate was investigated by in situ transmission electron microscopy (TEM). Plan-view, in situ TEM experiments revealed a relatively constant dislocation density of 3.4 x 10(9)-5.9 x 10(9) cm(-2) throughout thermal cycling. However, dislocation motion was strongly temperature dependent. At elevated temperatures dislocation moved continuously, while at temperatures below similar to 220 degreesC dislocation motion became jerky with a projected mean free path of similar to 70 nm. Furthermore, cross-sectional TEM specimens revealed that dislocations were attracted and pulled into the Cu/a-SiNx interface, where upon dislocation contrast disappeared. The limited dislocation mobility observed at low homologous temperatures may contribute to the high yield stress of the Cu films. (C) 2001 Elsevier Science B.V. All rights reserved.