Simultaneous Cu-Cu and Compliant Dielectric Bonding for 3D Stacking of ICs

This paper, for the first time reports the 3D stacking and interconnection of an extremely thinned IC by simultaneous Cu-Cu thermocompression and compliant glue layer bonding. Inclusion of a compliant glue layer serves reinforcement of the mechanical stability of the stack in areas where the inter-die interconnect density is low. It also enables separation in time of stacking on one hand and bonding on the other hand, thus enabling collective bonding after die to wafer stacking. We demonstrate electrically yielding 10 k through-wafer via chains without observable impact of the dielectric glue layer on the via chain resistance.