A model to estimate QE/MTF of thinned, back-side illuminated image sensors

An analytical model to estimate the quantum efficiency and the modulation transfer function of image sensors is proposed. Proposed approach follows similar prior studies, and tries to improve them in two directions: first, the impact of internal reflections on the optical generation profile is taken into account; second, the diffusion current calculations are extended for sensors utilizing graded-epi wafers and back-side passivation implants. A back-side illuminated photo diode sensor is used as a case study to demonstrate the model response.