High Index Spin-on Photosensitive Material and Process Optimization for Image Sensor Devices

This paper presents the developments of a new high refractive index material that can be used as a light guide in the back-end of CMOS image sensor to achieve optical path improvement and better light collection. Depending on the process conditions, the refractive index of the material can be tuned from 1.6 to 1.8 (RI@633nm). Moreover, this material can be patterned when exposed to i-line leading to a very simple and efficient cost- of-ownership process in the device fabrication flow. Material characteristics as well as patterning performance of a high refractive index precursor material are discussed here in the frame of a 1.4 μm pixel technology development.