Wafer reconstitution with precision dry front-to-front registration

This paper demonstrates a dry heterogeneous integration process for embedding CMOS chips into a partially-complete MEMS silicon wafer. By using standard IC processing, we create passive alignment structures in backside cavities on the MEMS wafer. The precision dry assembly utilizes front-to-front registration, removing the need for sidewall slope control of the backside Deep Reactive Ion Etch (DRIE). With dummy dice emulating CMOS chips, we show better than plusmn3 mum alignment in both the x- and y-directions after manual die insertion. This process allows formation of high density and low parasitic contacts between the embedded chips and wafer, by sputter deposition of metal to form vias and interconnects.