0.9-μm CMOS Image Sensors based on Digital Microlens

Abstract

The pixel size of CMOS image sensors (CIS) has steadily decreased over the past few decades. As the pixel size decrease, optical diffraction is difficult to ignore. We designed and optimized digital microlens for backside illuminated (BSI) CMOS image sensors (CIS) to reduce optical diffraction. Using two-dimensional finite-difference time-domain (FDTD) analysis, we designed several types of digital microlens and evaluated their optical characteristics. We applied the designed digital mircolens to a 0.9μm Hynix CIS structure and performed two-dimensional FDTD simulation. The optical properties of the CIS structures using the designed digital microlens were evaluated. In this paper, we represented new design concepts about digital microlens which can reduce optical diffraction of the CIS. Our results and proposed concepts are expected to make a significant contribution to the developments of sub-micron CIS pixels.