Investigations on an Ultra-Thin Bendable Monolithic Si CMOS Image Sensor

In this paper, theoretical as well as experimental results of the investigations on a bendable ultrathin Si monolithic CMOS image sensor are presented. The electro-optical behavior of a thinned flexible CMOS active pixel sensor for the application of uniaxial mechanical stress is theoretically and experimentally analyzed. The necessity of a correlated double sampling readout scheme to achieve a stress-independent operation is underlined. Optical as well as electrical characteristics of standard photodiodes on ultrathin silicon chips embedded into a polyimide foil under several bending configurations are discussed and experimental data are presented. Moreover, design rules for the stress-independent operation of a flexible ultrathin image sensor are given and the thinning and the encapsulation processes are shortly presented.