(a) A schematic image of the prototype BI-CIS pixels with the inverted pyramid array structures (IPA) and deep trench isolation (DTI). Each pixel equips on-chip micro lens (OCL) and RGB on-chip color filter (OCCF) in Bayer format. At the bottom of each pixel, there are CMOS transistors to readout collected carriers, which are not illustrated for simplicity. (b) A schematics of light rapping pixel concept. Normal incident light has the incident angle θ
1. It is refracted with the angle of θ
2 following Snell’s law. The refracted light is totally reflected at the pixel sidewall in case that the angle is larger than the critical angle. As a result, the effective optical path length elongate with in the Si substrate. (c,d) SEM cross-section and top-view images of c-Si with the IPA.