Hybrid CMOS focal plane array with extended UV and NIR response for space applications

Abstract

Silicon-based hybrid CMOS focal plane array technology offers many advantages needed for both ground-based and space imaging applications. These advantages include enhanced UV and NIR sensitivity, extensive on-chip readout capability, inherent radiation hardness, flexible imaging readout and the ability to provide extremely low noise at high video rates. For infrared imaging applications that involve UV-through visible channels, the readout electronics commonality facilitates a great simplification to system designs. In this paper, Rockwell Scientific CMOS-based hybrid silicon FPA technology and the recent progress are presented. The hybrid FPAs developed include 640x480, 1024x1024 and 2048x2048 formats with pixel sizes ranging from 27 m to 18 m square, featuring a high optical fill factor (~100%), broad-band response (200nm to 1000nm) with high quantum efficiency, and low read noise (<6e-) that approaches astronomy CCDs at 100KHz video rate and surpasses astronomy CCDs at 1MHz rate. Other performance parameters, such as spatial uniformity, dark current, pixel crosstalk/MTF and CMOS features are also discussed. SENSOR TECHNOLOGY FOR SPACE APPLICATION CCD and CMOSThe key requirements for a sensor assembly to operate in space environments are high reliability, low weight, low power and high tolerance to radiation damage. Since its invention in 1969 1 , silicon charge-coupled device (CCD) has improved in performance and built its flight heritage. Both size and format of CCDs have increased in the past several years for much-improved field-of-view and imaging resolution. This technology has been made available for various space missions, such as Galileo spacecraft 2 and Hubble Space Telescope 3 . However, concerns about CCDs in space exist due to charge transfer degradation in radiation environments, excessive power consumption, blooming and image smearing.CMOS-based monolithic image sensor is another class of solid-state electronic imaging sensor that is rapidly evolving along with the advances in modern sub-micron CMOS technology. CMOS sensors offer important solutions to the CCD limitations encountered for use in orbit. The operation of CMOS sensors requires only one charge transfer (pixel-based charge-to-voltage conversion) for signal readout, consumes a very low power (typically operated at 3.3V and lower), and enables miniature cameras with on-chip integration of analog and digital circuitry, which significantly reduces the system mass, volume and complexity. In addition, the CMOS sensor can operate in a wide temperature range (cryogenic to 350K). CMOS wafer fabrication can use the mainstream commercial semiconductor foundries, and the cost of fabricating a monolithic 200mm CMOS wafer is less than that of a 150mm wafer using a specialized CCD process. More importantly, the CMOS imager is inherently tolerant to radiation damage. Space missions employing CMOS sensors, such as Deep Space-1 (256x256 format APS) 4 and TEAMSAT (512x512 format APS) 5 , have provided encouraging science data and high contrast images.Ad...

Characterization of Si hybrid CMOS detectors for use in the soft X-ray band

“…HCDs are already finding use in many astronomical applications in the optical/IR energy bands [4][5][6]. This technology will be a major improvement over CCD technology for astronomical applications and the James Webb Space Telescope will take advantage of it by flying a Teledyne Imaging Systems (TIS) infrared H2RG using a HgCdTe array absorber [7].…”

“…At slow read out speeds the read noise in HCDs is currently worse than that found in the best CCDs. However, at Megapixel/s read out speeds, HCDs have lower read noise than CCDs [4].…”

Telescope guiding with a HyViSI H2RG used in guide mode

“…For an introduction to these sensors, the reader is referred to Bai et al (2003), 1 and to Bai et al (2008) 2 for the latest in HyViSI technology. Simms et al 3 and Dorland et al 4 characterized the rst generation 10 micron pixel 4096 × 4096 HyViSI H4RGs in the context of astronomy and found they suered from very high leakage currents.…”

First use of a HyViSI H4RG for astronomical observations

“…As with most CMOS devices, operation of the H4RG sensor consumes very low power (operated at 3.3V and lower) and enables on-chip integration of analog and digital circuitry. 1 The CMOS architecture also eliminates the need to shift charge toward an output by allowing non-destructive, random access to the pixels; only one pixel-based charge-to-voltage conversion is necessary. Since any pixel can be accessed independently of the others, CMOS detectors do not suffer from charge transfer inefficiency (CTE) due to radiation damage, where a charge trap in one pixel can affect all of the ones following it in its row.…”