Cross Dual-Pixel Twisted-Photodiode Image Sensor for All-Directional Auto Focus

We present a CMOS image sensor with twisted photodiode (PD) that enables all-directional autofocus (AF) for high-speed and high-accuracy AF. The newly developed 3D-stacked back side illuminated (BSI) sensor with twisted PD achieves a comparable AF angular response for horizontal and vertical directions, realizing AF in all pixels and in all directions. In addition, full well capacity (FWC) of 121,000e- and image lag of <1e- were achieved by adopting a structure that increases p-n junction capacitance. Sub-pixel saturation of 41,000e- was achieved, a property which determines the illuminance range of AF in high-light conditions. The AF performance under low light condition was also improved by using high-sensitivity phase detection auto focus (PDAF) in all pixels of the sensor to achieve a minimum AF illuminance level of 0.007 lux.