Effect of High Energy Implantation on the Photoresist for Smaller Size CMOS Image Sensor

High energy implantation has become a key process to form n- and p-type well structures in small size CMOS image sensors (CIS) for higher full well capacity (FWC) purpose. However, high energy application needs relatively thicker photo-resist (PR) above 3µm in thickness than conventional ion implantation process depending on the ion energy and ion dosages. This thick PR will shrink during the ion implantation, which contribute additional side effect on the PR critical dimension and PR effective thickness to against next implantation step. Such effect will has an impact on the CIS performance, especially on smaller pixel products. To study the effect of high energy implantation on the PR for small size CIS, the shrinkage behavior of 3µm PR under different implantation energy and dosages was investigated in this work.