Cu-Cu Thermo-Compression Bonding for TSV Integration

Abstract

We developed total solutions for the optically aligned Cu-Cu direct bonding process. The quantitative analyses of the interfacial adhesion energy and seam voids of Cu-Cu bonds performed with varying process parameters showed that bonding temperature and post-bond annealing have the most significant influence on bond properties. By optimizing experimental parameters, we could achieve, even with a short bonding time, the sufficient interfacial adhesion energy ({greater than or equal to}5 J/m2) with no interfacial voids. Post-bond annealing performed at 250-300ºC drastically improves the interfacial adhesion energy. SmartView alignment enables the face-to-face Cu-Cu bonding of non-IR transparent wafers while maintaining less than 0.2µm (3σ) and 1.0µm (3σ) of the pre-bond and post-bond alignment accuracy, respectively. Temporary bonding and debonding based on a new spin-on adhesive has such benefits as temperature stability up to 250ºC, compatibility with bumped structures, short debonding time, low-temperature (<200ºC) slide-off release, easy cleanup with polar solvents, etc.