A novel 3D stacking method for opto-electronic dies on CMOS ICs

A high speed, high density and potentially low cost solution for realizing a compact transceiver module is presented in this paper. It is based on directly bonding an Opto-electronic die on top of CMOS IC chip and creating a photoresist ramp to bridge the big step (around 220µm) from Opto-electronic pads to CMOS IC pads. The required electrical connection between them is realized lithographically with a process than can be scaled to full wafer production. A 12-channel transmitter based on the technique was fabricated and test shows good performance up to 12.5 Gb/s/ch.