Abstract

The optical effects of dielectric film properties and thickness are investigated for 0.18um enhanced CMOS image sensor. The spectral response degradation caused by destructive interference was observed in the photodiode under Si surface with thicker contact etch stop layer (CESL) and thicker oxide on Si surface. Investigations of optical effect on dielectric films show proper film structure and thickness that can result in higher quantum efficiency. In this paper, a low extinction coefficient (low-k) SIN for CESL combined with CESL/Oxide/Si films structure have been proposed by the experimental and simulation results of quantum efficiency. The spectral response can be improved and offer an optimized dielectric film thickness for CESL/Oxide/Si film structure. To improve photo-sensitivity, a high refraction-index (R.I.) inner microlens in CMOS image sensor, which result in increasing photo-sensitivity by 50% at least.