Application of a Bevel Etch Process for Improving Particle Performance in CMOS Image Sensor Manufacture

Due to the continuing improvements of CMOS image sensor (CIS) technology, the back side-illumination (BSI) structure was involved to overcome optical characteristics deterioration in smaller pixels. In BSI structure, bonding loop is necessary to adhere two wafers. However, multiple dielectric and metal layer on the bevel of the device wafer possibly to be the source of defect as it is so loose that peeling particles will fall on the wafer after trimming step and bubble defect will formed at last. The main objective of the work is to improve peeling particle performance. After insertion of bevel etch, the number of peeling particles was reduced to less than 5ea compared with more than 300ea without bevel etch. Ultimately, no more bubble defect was found due to peeling particles clear off. What's more, we also discuss the mechanism of peeling particles and bubble defect forming. And the roles of different components of the gas mixtures in the bevel etch process.