Cu-Cu insertion bonding technique using photosensitive polymer as WLUF

In this paper optimized fabrication process flow for insertion bonding is reported. Processing challenges for top wafer including selection and patterning photosensitive polymer as underfill (UF), pick and place optimization and TSV reveal, and processing issues for bottom die such as sloped uniform oxide etching over 300mm wafer, Cu electroplating and CMP will be reported. Furthermore, die to die stacking process optimization for polymer to oxide and Cu-Cu bonding, electrical results and cross section images will be discussed.