Pinning voltage model of vertical pinned photodiode for Dual-Pixel image sensor

Abstract

This paper presents a simple solution for the pinning voltage of vertical pinned photodiode used in a dual-pixel configuration for phase-detection autofocus applications. Analytic solution of the conventional square deep photodiode has been presented elsewhere. However, this model cannot be adopted to dual pixel where a square pixel contains two rectangular photodiodes. Therefore, we propose a simple analytical model for the rectangular deep photodiode for dual pixels and validate its accuracy by TCAD simulations. The presented model accurately predicts the pinning voltage and potential inside the deep photodiode for dual pixels, thereby confirming its usefulness in the ab-initio design of the pixel as well as in the analysis of the photodiode design.