HNA Wet Etching Optimization in Wafer Thinning of BSI Process

In order to achieve higher quantum efficiency and sensitivity of image sensor, the Backside-Illumination (BSI) has been developed by turning FSI's metal wiring and photosensitive area upside down. Together with the benefits, a series of new challenges are also brought along with this new technology. Among them, how to achieve uniform wafer thinning has become a critical issue for wet clean process. This paper focuses on wet etching optimization of HNA, the chemical applied in wafer thinning process. With help of advanced Lam Research SP323 single wafer clean hardware and software, an improved wafer thinning performance throughout long-time running can be achieved.