Invited Paper
Silicon infrared focal plane arrays Masafumi Kimata*, Hirofumi Yagi, Masashi Ueno, Junji Nakanishi, Tomohiro Ishikawa, Yoshiyuki Nakaki, Makoto Kawai, Kazuyo Endo, Yasuhiro Kosasayama, Yasuaki Ohota, Takaki Sugino, and Takanori Sone Advanced Technology R & D Center, Mitsubishi Electric Corporation 8- 1- 1 ,
Tsukaguchi-Honmachi, Amagasaki City, Hyogo 661-8661 , Japan
ABSTRACT Using Si VLSI technology, we can fabricate various kinds of infrared focal plane arrays (FPAs) which cover spectral bands from short wavelength infrared (SWIR) to long wavelength infrared (LWJR). The Si-based technology offers many attractive features, such as monolithic integration, high uniformity, low noise, low cost, and high productivity. We have been developing Si-based infrared FPAs for more than 20 years and have verified their usefulness. The FPAs developed so far include PtSi
mid wavelength infrared (MWIR) FPAs with array sizes from 256x256 to 1040x1040 pixels, two PtSi SWIR linear FPAs for spaceborne applications, a 512x5 12 element GeSi LWIR FPA, and a 320x240 element uncooled LWIR FPA. For PtSi MWIR FPAs, we have developed an original readout architecture called Charge Sweep Device (CSD), which improves the sensitivity by enlarging the fill factor. We have also devised a novel structure with pn junction diodes on an 501 substrate
for uncooled infrared FPAs. Unlike other uncooled FPA technologies, the full structure of our uncooled FPA can be manufactured in a conventional Si VLSI production line except for the final release process. In this paper, we report our Si-
based infrared FPA technology.
Keywords: Focal plane array, PtSi Schottky-banier, GeSi heterojunction, 501, diode, uncooled focal plane array
1. INTRODUCTION Choice ofmaterial and fabrication process for infrared FPAs depends on the environment ofproduction. It is understandable
that most infrared focal plane array (FPA) suppliers which do not have Si LSI production lines should choose compound
semiconductors with high quantum efficiency (Q.E.) as photodetectors. They can make infrared FPAs by mating their photodetector chips with Si readout ICs that are manufactured by other Si foundries. However, building up compound semiconductor infrared FPA technology is expensive and time-consuming work if we consider pure commercial applications.
We have Si LSI production lines in our company, and have been developing infrared FPAs which can be manufactured using only a single Si-LSI production line. Our approach has reduced not only the production cost but also the research and development cost, and we have verified the usefulness of the Si-based infrared FPA technology. Figure 1 illustrates our Si-based technology map, including conventional intrinsic Si visible image sensors. We started our infrared activities with a 2-D PtSi Schottky-banier (SB) infrared FPA in 1980'. 2-D PtSi FPAs are for thermal imaging in
the mid wavelength infrared (MWIR) spectral band. We developed a readout architecture called Charge Sweep Device *
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Correspondence: Email:
[email protected]; Telephone: +81-6-6497-75 19; Fax:+8l-6-6497-7288
Photodetectors: Materials and Devices VI, Gail J. Brown, Manijeh Razeghi, Editors, Proceedings of SPIE Vol. 4288 (2001) © 2001 SPIE · 0277-786X/01/$15.00
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