Study and Control of the Distortion Induced by the Bonding Process for BSPDN Approaches

With the development of the Back-Side Power Delivery Network (BSPDN), new challenges and specifications in terms of alignment for subsequent exposure steps arise. Indeed, for 2-nm node technology this requires a very fine correction of the distortion induced by all the process steps on the transferred thin layer. One process step in particular seems to have a predominant effect on this aspect: the bonding. This paper introduces the methodology developed at CEA-Leti in collaboration with ASML and EVGroup, to characterize the distortion induced by the direct bonding process step at global and local scale. The integration flow simulates BSPDN approach, considering a thin silicon layer to be transferred to another substrate, and allows developing innovative immersion scanner correction strategies.