An Efficient Method for Modeling Parasitic Light Sensitivity in Global Shutter CMOS Image Sensors

Abstract

Parasitic Light Sensitivity (PLS) is a key performance parameter for Global Shutter CMOS Image Sensors (GSCIS), which quantifies the sensor sensitivity to light when the shutter is supposed closed. Its modeling and understanding would allow for an optimization in developing future sensors. This paper aims to present an efficient method for 2D modeling PLS in GSCIS through separation of the optical problem from the carriers motion one. The optical problem is solved thanks to Finite-Differences Time-Domain (FDTD) simulations, while solution to the carriers motion problem is given through the application of the Boltzmann Transport Equation (BTE). This method is presented as a faster alternative to the coupled use of FDTD and TCAD simulations: since it is supposed that the two problem solutions are independent, the two simulations can be performed in parallel. The results show good match between the developed method and the TCAD solutions, thus showing fair agreement with experimental data, probably due to a poor knowledge of the back-end process.