<200 nm Wafer-to-wafer overlay accuracy in wafer level Cu/SiO2 hybrid bonding for BSI CIS

Sub 200 nm wafer-to-wafer (w2w) overlay accuracy on the entire 300 mm wafer was successfully demonstrated via wafer level Cu/SiO₂ hybrid bonding. Cu bonding pads relevant for back-side illuminated (BSI) complementary metal oxide semiconductor (CMOS) image sensor (CIS) were used for the experiment. Further, a crucial component to improve the overlay accuracy, namely the overlay model which identifies systematic alignment errors, was described.