Impact of temporary substrates & adhesives on die-to-wafer overlay

Abstract

A critical review of the alignment factors contributing to the final die-to-target wafer overlay in a collective die to wafer bonding flow is presented and discussed in terms of minimal residual bonding errors. The impact of several substrates, such as glass vs silicon wafers, and materials, such as thermoset vs thermoplastics, are evaluated, as well as the used tools (die placement & wafer bonder) and bonding conditions. Although polymer-based glass carriers allow for much more process control in terms of die-height variations and debonding options compared to polymer free silicon carriers, they add negative alignment contributions which, start to dominate with the new generation of die-pick-and place tools and wafer bonders.