Monolithic Thin Wafer Stacking Using Low Temperture Direct Bonding

The high process temperature required for silicon oxide fusion bonding (e.g. ~1000°C) prevented its use for 3D applications. In the recent years low-temperature fusion bonding processes (200°C – 400°C) have been developed for addressing such applications. In this study, low-temperature fusion bonding in combination with standard thin wafer manufacturing processes based on temporary bonding/debonding technology in order to demonstrate thin layer direct bonding with subsequent multi-layer stacking capability using standard semiconductor manufacturing bonding equipment. Monolithic integration of two 10µm thin temporary bonded silicon layers onto a standard 775µm thick Si wafer is shown and discussed in detail.