Mark C. Farris

HAWAII-2RG: a 2k x 2k CMOS multiplexer for low and high background astronomy applications

The HAWAII-2RG is a major upgrade of our prior 2048 x 2048 CMOS readout for astronomy (HAWAII-2) to support the requirements of the Next Generation Space Telescope and enable breakthrough capability for ground-based astronomy. By migrating to 0.25μm CMOS, for the first time guide mode readout is simultaneously supported in combination with various programmable science modes on a frame-by-frame basis. Consequently, the readout simultaneously supports programmable guide mode window and full-field science using the rest of the 4.2 million pixels at read noise <5 e-. Also for the first time with any imaging sensor, low and high background astronomy is supported using from 1 to 32 low-noise outputs via low-speed and high-speed signal paths. The latter supports throughput rate of up 320 MHz for real time imaging at >60 Hz. As with the HAWAII-2, the readout can be mated to our infrared and visible detector arrays including low dark current MBE HgCdTe at cutoff wavelengths from 1.5μm to 14μm, 2.5μm PACE HgCdTe, and silicon p-i-n detectors with superior quantum efficiency to backside-illuminated CCDs.

Teledyne Imaging Sensors: silicon CMOS imaging technologies for x-ray, UV, visible, and near infrared

Teledyne Imaging Sensors develops and produces high performance silicon-based CMOS image sensors, with associated electronics and packaging for astronomy and civil space. Teledynes silicon detector sensors use two technologies: monolithic CMOS, and silicon PIN hybrid CMOS. Teledynes monolithic CMOS sensors are large (up to 59 million pixels), low noise (2.8 e- readout noise demonstrated, 1-2 e- noise in development), low dark current (<10 pA/cm2 at 295K) and can provide in-pixel snapshot shuttering with >103 extinction and microsecond time resolution. The QE limitation of frontside-illuminated CMOS is being addressed with specialized microlenses and backside illumination. A monolithic CMOS imager is under development for laser guide star wavefront sensing. Teledynes hybrid silicon PIN CMOS sensors, called HyViSITM, provide high QE for the x-ray through near IR spectral range and large arrays (2K×2K, 4K×4K) are being produced with >99.9% operability. HyViSI dark current is 5-10 nA/cm2 (298K), and further reduction is expected from ongoing development. HyViSI presently achieves <10 e- readout noise, and new high speed HyViSI arrays being produced in 2008 should achieve <4 e- readout noise at 900 Hz frame rate. A Teledyne 640×480 pixel HyViSI array is operating in the Mars Reconnaissance Orbiter, a 1K×1K HyViSI array will be launched in 2008 in the Orbiting Carbon Observatory, and HyViSI arrays are under test at several astronomical observatories. The advantages of CMOS in comparison to CCD include programmable readout modes, faster readout, lower power, radiation hardness, and the ability to put specialized processing within each pixel. We present one example of in-pixel processing: event driven readout that is optimal for lightning detection and x-ray imaging.

2Kx2K molecular beam epitaxy HgCdTe detectors for the James Webb Space Telescope NIRCam instrument

The NIRCam instrument will fly ten of Rockwell Scientific’s infrared molecular beam epitaxy HgCdTe 2048x2048 element detector arrays, each the largest available with current technology, for a total of 40 Megapixels. The instrument will have two varieties of MBE HgCdTe, a SWIR detector with λco = 2.5 μm, for the shortwave channel of NIRCam (0.6-2.3 μm); and a MWIR detector with λco = 5.3 μm, for the longwave channel of NIRCam (2.4-5.0 μm). Demonstrated mean detector dark currents less than 0.01 electrons per second per pixel at operating temperatures below 42 K for the MWIR and below 80 K for the SWIR, combined with quantum efficiency in excess of 80 percent and read noise below 6 electrons rms, make these detector arrays by far the most sensitive SWIR and MWIR devices in the world today. The unique advantages of molecular beam epitaxy as well as FPA data on noise, dark current, quantum efficiency, and other performance metrics will be discussed. In addition, the focal plane assembly package designs will be presented and discussed.

H2RG focal plane array and camera performance update

Teledyne’s H2RG focal plane arrays have been widely used in scientific infrared and visible instruments for ground-based and space-based telescopes. The majority of applications use the H2RG with 2.5 micron cutoff HgCdTe detector pixel at an operating temperature of ~77 K (LN2). The exceptionally low dark current of the 2.5 micron H2RG allows for operation at higher temperatures which facilitates simplified instrument designs and therefore lower instrument cost. Performance data of 2.5 micron H2RG arrays at 77K, 100 K, and 120 K are presented and are discussed as a function of detector bias and pixel readout rate. This paper also presents performance data of 1.75 micron and 5.3 micron H2RG focal plane arrays and discusses some of the inherent performance differences compared to 2.5 micron cutoff arrays. A complete infrared camera system that uses the H2RG focal plane array and SIDECAR ASIC focal plane electronics is introduced.

Development of hybrid CMOS visible focal plane arrays at Rockwell

Silicon-based hybrid CMOS visible focal plane array (FPA) technology is emerging as a strong contender for scientific applications that require broad spectral response with low noise, highly integrated functionality and radiation hardness. CMOS-based FPAs offer many advantages in high speed, low-noise detection and signal processing. As a high performance alternative to advanced CCD imaging arrays, the hybrid design enables independent optimization of the silicon detector array and silicon readout electronics. Multiplexer commonality with the instruments IR channels is another attractive feature for integrators of sensor sites such as for hyperspectral spectrometers. In this paper, the technical merits of Rockwells CMOS-based hybrid visible FPAs are described including key detector performance aspects, interface electronics requirements, radiation hardness and concomitant implications for diverse imaging applications. At this time we have developed 640 X 480 and 1024 X 1024 hybrid imagers with approximately equals 100% optical fill factor, high broadband QE spanning ultraviolet (UV) through near infrared (NIR), wide dynamic range, and high pixel operability. Dark current of approximately equals 0.01e-/sec and read noise approximately equals 6e- have been measured on one prototype 1024 X 1024 FPA that uses Hawaii readout integrated circuit (ROIC). Initial radiation data indicate a total ionization dose (TID) tolerance greater than 35 Krad for our standard CMOS process.

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

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 27μm to 18μm 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.

Hybrid CMOS x-ray detectors: the next generation for focused x-ray telescopes

In a joint program of Penn State University and Teledyne Imaging Sensors, hybrid CMOS sensors have been developed for use as X-ray detectors. This detector technology can provide major improvements in performance relative to CCDs, which are the current standard technology used in the focal planes of X-ray telescopes (e.g. Chandra, XMM, Suzaku, and Swift). Future X-ray telescope missions are all likely to have significantly increased collection area. If standard CCDs are used, the effects of saturation (pile-up) will have a major impact, while radiation damage will impact the quality and lifetime of the detectors. By reading out the hybrid CMOS detector in a pixel-by-pixel fashion at high speeds, with an energy resolution similar to CCDs, CMOS sensors could increase the range of pile-up free operation by several orders of magnitude. They are also several orders of magnitude more radiation hard than typical CCDs since they transfer charge through the thickness of the device, rather than across the length of its surface. Furthermore, hybrid CMOS detectors can be programmed to read out any variety of windowed regions, which leads to versatility and speed. All of this can be achieved, in principle, while maintaining the same quantum efficiencies achievable in CCDs. Results of this development effort and preliminary tests of fabricated detectors will be presented, along with potential applications for future missions such as EDGE and Constellation-X.

Measurements of Si Hybrid CMOS X-Ray Detector Characteristics

The development of Hybrid CMOS Detectors (HCDs) for X-Ray telescope focal planes will place them in contention with CCDs on future satellite missions due to their faster frame rates, flexible readout scenarios, lower power consumption, and inherent radiation hardness. CCDs have been used with great success on the current generation of X-Ray telescopes (e.g. Chandra, XMM, Suzaku, and Swift). However their bucket-brigade readout architecture, which transfers charge across the chip with discrete component readout electronics, results in clockrate limited readout speeds that cause pileup (saturation) of bright sources and an inherent susceptibility to radiation induced displacement damage that limits mission lifetime. In contrast, HCDs read pixels with low power, on-chip multiplexer electronics in a random access fashion. Faster frame rates achieved with multi-output readout design will allow the next generations larger effective area telescopes to observe bright sources free of pileup. Radiation damaged lattice sites effect a single pixel instead of an entire row. Random access, multi-output readout will allow for novel readout modes such as simultaneous bright-source-fast/whole-chip-slow readout. In order for HCDs to be useful as X-Ray detectors, they must show noise and energy resolution performance similar to CCDs while retaining advantages inherent to HCDs. We will report on readnoise, conversion gain, and energy resolution measurements of an X-Ray enhanced Teledyne HAWAII-1RG (H1RG) HCD and describe techniques of H1RG data reduction.

4K×4K format 10μm pixel pitch H4RG-10 hybrid CMOS silicon visible focal plane array for space astronomy

Teledyne’s silicon hybrid CMOS focal plane array technology has matured into a viable, high performance and high- TRL alternative to scientific CCD sensors for space-based applications in the UV-visible-NIR wavelengths. This paper presents the latest results from Teledyne’s low noise silicon hybrid CMOS visible focal place array produced in 4K×4K format with 10 μm pixel pitch. The H4RG-10 readout circuit retains all of the CMOS functionality (windowing, guide mode, reference pixels) and heritage of its highly successful predecessor (H2RG) developed for JWST, with additional features for improved performance. Combined with a silicon PIN detector layer, this technology is termed HyViSI™ (Hybrid Visible Silicon Imager). H4RG-10 HyViSI™ arrays achieve high pixel interconnectivity (<99.99%), low readout noise (<10 e- rms single CDS), low dark current (<0.5 e-/pixel/s at 193K), high quantum efficiency (<90% broadband), and large dynamic range (<13 bits). Pixel crosstalk and interpixel capacitance (IPC) have been predicted using detailed models of the hybrid structure and these predictions have been confirmed by measurements with Fe-55 Xray events and the single pixel reset technique. For a 100-micron thick detector, IPC of less than 3% and total pixel crosstalk of less than 7% have been achieved for the HyViSI™ H4RG-10. The H4RG-10 array is mounted on a lightweight silicon carbide (SiC) package and has been qualified to Technology Readiness Level 6 (TRL-6). As part of space qualification, the HyViSI™ H4RG-10 array passed radiation testing for low earth orbit (LEO) environment.

Recent progress of hybrid CMOS visible focal plane array technology

Silicon-based hybrid CMOS visible focal plane array technology is emerging as a viable high performance alternative to scientific CCDs. The progress is attributed to the rapid advances in CMOS technology, mature precision flip-chip hybridization of large size and fine pixel arrays, and detector array performance improvements. Its technology readiness level (TRL) for space applications is being enhanced by relevant environmental tests and in-depth characterization of sensor performance. In this paper, we present recent results of Rockwell Scientifics hybrid CMOS silicon focal plane array technology, including large format arrays up to 2048x2048, broadband QE, sensor noise improvement, high radiation hardness, and the higher degree of system integration through on-chip ADCs and companion ASICs.