Image Sensors at IEDM 2011

IEDM 2011 promises to be quite rich on image sensor content. Session 8 program includes 7 image sensors presentation vs the last year's five. All the leaders - Sony, TSMC, Omnivision, Panasonic, Samsung, and others, are there and presenting.

Some notable achievements:

TSMC and Ominivision are going to demo their 0.9um pixel quality
Panasonic is reporting 72% QE in its 1.4um FSI pixel - better than BSI

The presentation list:

8.1 A Novel “FLAT” Device Structure for High Quality CMOS Image Sensors
K. Itonaga, K. Mizuta, T. Kataoka, M. Yanagita, H. Ikeda, H. Ishiwata, Y. Tanaka, T. Wakano, Y. Matoba, T. Oishi, R. Yamamoto, S. Arakawa, J. Komachi, M. Katsumata, S. Watanabe, S. Saito, T. Haruta, S. Matsumoto, K. Ohno, T. Ezaki, T. Nagano and T. Hirayama, Sony

We have developed the flat device structure with no isolation grooves / ridges and no Si substrate etching in the imaging area of the CMOS Image Sensor. We successfully fabricated a high quality 1.12um pixel pitch CIS, achieving both high Qs under low dark current and low random noise.

8.2 High Performance 300mm Backside Illumination Technology for Continuous Pixel Shrinkage
D.N. Yaung, B.C. Hsieh, C.C.Wang, J.C. Liu, T.J. Wang, W.D. Wang, C.C. Chuang, C. Chao, Y.L. Tu, C.S.Tsai, T.L. Hsu, F. Ramberg, W.P. Mo, H. Rhodes*, D. Tai*, V.C. Venezia*, S.G. Wuu, TSMC, OmniVision*

In order to reap the full advantages of BSI structures, it is very crucial to well control BSI process, particularly for small pixel size (<0.9um). In addition, as pixel transistors shrink with pixel scaling, an undesirable RTS could dominate noise and degrade CMOS sensor quality, which can be improved by BSI process. In this paper, we exhibit the progress of 300mm BSI process and a methodology to reduce RTS noise. Finally, a high quality 0.9um BSI pixel is demonstrated.

8.3 A 1.4μm Front-side Illuminated Image Sensor with Novel Light Guiding Structure Consisting of Stacked Lightpipes
H. Watanabe, J. Hirai, M. Katsuno, K. Tachikawa, S. Tsuji, M. Kataoka, S. Kawagishi, H. Kubo, H. Yano, S. Suzuki, G. Okazaki, K. Yamamoto, H. Fujinaka, T. Fujioka, M. Suzuki, Panasonic

A frontside illuminated image sensor with novel light guiding structures consisting of stacked lightpipes has been developed using 45nm Cu processing on 300 mm wafers. We demonstrated a high quantum efficiency of 72% and maximum incident angle of 40°, which exceeds the performance of backside illuminated image sensors

8.4 Investigation of Dark Current Random Telegraph Signal in Pinned Photodiode CMOS Image Sensors
V. Goiffon, C. Virmontois, P. Magnan, ISAE

The characteristics of Dark Current Random Telegraph Signal (DC-RTS) in pinned photodiode are investigated thanks to a dedicated analysis tool. Our results demonstrate, for the first time in pinned photodiode CIS, that this DC-RTS is due to meta-stable oxide interface SRH generation centers located in the transfer gate depletion region.

8.5 A CMOS Compatible Ge-on-Si APD Operating in Proportional and Geiger Modes at Infrared Wavelengths
A. Sammak, M. Aminian*, L. Qi, W.D. de Boer, E. Charbon, L.K. Nanver, University of Delft, *EPFL

A family of CMOS compatible Ge-on-Si APDs operating both in Geiger and proportional mode is proposed. The APDs exhibit the lowest reported dark current and amongst the smallest geometries. Low defect density n-Ge is grown on Si using a special CVD technique and a nm-thin Ga+B layer deposited for ultrashallow p+doping. The APDs have a good sensitivity in near infrared wavelengths and moderate DCR.

8.6 Enhanced Angle Sensitive Pixels for Light Field Imaging
S. Sivaramakrishnan, A. Wang, P.R. Gill, A. Molnar, Cornell University

Previously demonstrated Angle Sensitive Pixels (ASPs) for integrated digital light-field imaging suffer from poor pixel quantum efficiency and large sensor size. This work demonstrates an ASP device that uses phase gratings and a pair of interleaved diodes to double pixel density and improve quantum efficiency by a factor of 4.

8.7 A 192X108 Pixel ToF-3D Image Sensor with Single-tap Concentric-gate Demodulation Pixels in 0.13 um Technology
T.-Y. Lee, Y. Lee, D.-K. Min, S. Lee, W. Kim, S. Kim, J.-K. Jung, I. Ovsiannikov, Y.-G. Jin, Y. Park, E. R. Fossum, C. Chung, Samsung

A single-tap concentric photogate pixel of 28 um pitch is developed for application in ToF-3D image sensor. Image sensor formed with the 198X108 pixel array exhibits demodulation contrast higher than 50% and distance error less than 1%, over 1 to 7 m range, with 20MHz modulation of 850 nm LED.