THERMOMECHANICAL FAILURES IN MICROELECTRONIC INTERCONNECTS

Thermomechanical Fatigue failures are an important class of failures i n microelectronic interconnect structures. Thermomechanical stresses a rise from differences in the coefficients of thermal expansion of the various materials comprising a microelectronics circuit. Polymer diele ctrics and adhesives have larger coefficients of expansion than metal conductors. Dielectrics and adhesives may also exhibit large anisotrop y in the coefficient of expansion, producing significant thermomechani cal stresses in vias or other metal interconnect structures. During am bient thermal cycling or operational power dissipation, cyclic stresse s are induced, which cause fatigue failures. The basic elements of the rmomechanical fatigue behavior of microelectronic interconnect structu res, such as lines and vias, are presented in this paper. In addition, a case study illustrating many of the concepts is presented for a com plex 3-D interconnect. (C) 1998 Elsevier Science Ltd. All rights reser ved.