CMOS wafer bonding for back-side illuminated image sensors fabrication

Backside illuminated CMOS image sensors were developed in order to encompass the pixel area limitation due to metal interconnects. In this technology the fully processed CMOS wafer is bonded to a blank carrier wafer and then back-thinned in order to open the photosensitive sensor area. The process flows of the two main competing wafer bonding technologies used for this manufacturing process (adhesive bonding and low temperature plasma activated direct wafer bonding with polymer layers) will be reviewed.