Small pixel development for novel CMOS image sensors

Abstract

Modern trends in camera module design for both mobile and DSC applications are driving the race to shrink pixel and increase pixel array size. At the same time higher demands on the quality of color images - DSC-like quality for mobile applications - require maintaining a large pixel capacity, quantum efficiency (QE), and sensitivity to preserve color image quality. This becomes extremely difficult as the size of the pixel shrinks. This paper discusses the Common Element Pixel Architecture (CEPA) for image sensors with small pixels as well as new pixel designs and process changes, that have enabled a new generation of image sensors with high performance 2.2-μm, 1.75-μm, and smaller pixels. Advanced algorithms of capturing the image help to overcome the challenges associated with the limited pixel capacity of small pixels. The paper considers an HDR mode of operation for the small pixel and its effect on the image quality. Achieving good color crosstalk performances is one of the big challenges in CMOS Image Sensors with small pixels. The paper presents results of an experimental study of crosstalk for different pixel sizes, analyzes the effect of crosstalk on the quality of color image and signal-to-noise ratio after color processing, and discusses ways of cross talk reduction for small pixels.