0.9-um 픽셀 CMOS 이미지 센서 광학 구조 설계 연구

Abstract

The pixel size of CMOS image sensors (CIS) has steadily decreased over the past few decades. As the pixel size decreases, the optical diffraction is difficult to ignore and effective photodiode area get smaller than previous CIS. Therefore, sub-micron pixel CIS has lower optical efficiency and higher optical crosstalk. We designed the anti-reflection spacer (AR spacer) and the digital microlens structure for backside illuminated CIS to improve the optical properties. We used a finite-difference time-domain (FDTD) analysis to evaluate the optical properties of the structures. In this paper, we represented new design concepts about digital microlens and found optimal anti-reflection coating conditions. Using these two methods, we can improve the optical properties of the 0.9-μm pixel CIS. Our results are expected to make a significant contribution to the developments of sub-micron CIS pixels.