Acoustic modulation during laser debonding of collective hybrid bonded dies

Laser debonding is assessed as an alternative to mechanical peel debonding in a collective hybrid bonding flow. Potential risks associated with the laser, such as the UV-photon energy, thermal energy and mechanical/acoustic energy are evaluated both on dummy wafers as on electrically yielding device wafers. It is shown that the laser ablation of a so called laser release layer generates an acoustic shock wave that in the case of ultra-thin dies can lead to die damage and thus a lower transfer yield. A model is proposed and based on it and an `acoustic layer' is added to the flow which is successful in preventing this type of damage. The influence of this additional layer on the established bonding process of reference is assessed in detail. A 100% die-transfer yield with an average sub 150 nm die-to-target-wafer alignment yield is achieved.