7.9 1/2.74-inch 32Mpixel-Prototype CMOS Image Sensor with 0.64μ m Unit Pixels Separated by Full-Depth Deep-Trench Isolation

Abstract

For years, there has been a strong drive for sub-micron pixel development, in spite of reaching the visible light diffraction limit, because a smaller pixel pitch of CMOS image sensors (CISs) is inevitably required for ever-miniaturizing camera modules as mobile devices incorporate more cameras, few of which are dedicated to ultra-high-resolution zoomed images [1]. To that end, image sensor vendors have tried to find new ways to avoid reduction in sensitivity and more crosstalk in the sensor through pixel architecture change and/or fabrication process refinement [2] –[4]. For example, a $0.7 \mu m$ pixel sensor was demonstrated with acceptable photodiode (PD) full-well capacity (FWC) of $\gt 6$,000e- as well as signal-to-noise ratio (SNR) of $\sim32$ dB without optical/electrical crosstalk by employing state-of-the-art full-depth deep-trench isolations (FDTIs). [4] However, further scaling requires elaborate fabrication innovation and layout ideas. At the same time, meeting every aspect of pixel performance compared to the previous generation becomes even more difficult, e.g., with respect to dark or illuminated characteristics, fixed-pattern or temporal noises, etc. The latter, in particular, is associated with in-pixel source-follower (SF) amplifiers. Therefore, electrical performance of scaled in-pixel transistors cannot be overlooked. In this paper, a 32-megpixel (MP) CIS with $0.64 \mu m$ unit pixels is demonstrated with FDTI design. Innovations in terms of fabrication and design to achieve this performance with scaling are discussed.