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Silicon single photon imaging detectors

Published in:
SPIE Vol. 8155, Infrared Sensors, Devices, and Applications; Single Photon Imaging II, 21 August 2011, 81551C.

Summary

Single-photon imaging detectors promise the ultimate in sensitivity by eliminating read noise. These devices could provide extraordinary benefits for photon-starved applications, e.g., imaging exoplanets, fast wavefront sensing, and probing the human body through transluminescence. Recent implementations are often in the form of sparse arrays that have less-than-unity fill factor. For imaging, fill factor is typically enhanced by using microlenses, at the expense of photometric and spatial information loss near the edges and corners of the pixels. Other challenges include afterpulsing and the potential for photon self-retriggering. Both effects produce spurious signal that can degrade the signal-to-noise ratio. This paper reviews development and potential application of single-photon-counting detectors, including highlights of initiatives in the Center for Detectors at the Rochester Institute of Technology and MIT Lincoln Laboratory. Current projects include single-photon-counting imaging detectors for the Thirty Meter Telescope, a future NASA terrestrial exoplanet mission, and imaging LIDAR detectors for planetary and Earth science space missions.
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Summary

Single-photon imaging detectors promise the ultimate in sensitivity by eliminating read noise. These devices could provide extraordinary benefits for photon-starved applications, e.g., imaging exoplanets, fast wavefront sensing, and probing the human body through transluminescence. Recent implementations are often in the form of sparse arrays that have less-than-unity fill factor. For...

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MBE back-illuminated silicon Geiger-mode avalanche photodiodes for enhanced ultraviolet response

Published in:
SPIE Vol. 8033, Advanced Photon Counting Techniques V, 25 April 2011, 80330D.

Summary

We have demonstrated a wafer-scale back-illumination process for silicon Geiger-mode avalanche photodiode arrays using Molecular Beam Epitaxy (MBE) for backside passivation. Critical to this fabrication process is support of the thin (< 10 um) detector during the MBE growth by oxide-bonding to a full-thickness silicon wafer. This back-illumination process makes it possible to build low-dark-count-rate single-photon detectors with high quantum efficiency extending to deep ultraviolet wavelengths. This paper reviews our process for fabricating MBE back-illuminated silicon Geigermode avalanche photodiode arrays and presents characterization of initial test devices.
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Summary

We have demonstrated a wafer-scale back-illumination process for silicon Geiger-mode avalanche photodiode arrays using Molecular Beam Epitaxy (MBE) for backside passivation. Critical to this fabrication process is support of the thin ( 10 um) detector during the MBE growth by oxide-bonding to a full-thickness silicon wafer. This back-illumination process makes...

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Adaptive optics wavefront sensors based on photon-counting detector arrays

Published in:
Proc. SPIE Vol. 7736, Adaptive Optics Systems II, 27 June 2010, 773610.

Summary

For adaptive optics systems, there is a growing demand for wavefront sensors that operate at higher frame rates and with more pixels while maintaining low readout noise. Lincoln Laboratory has been investigating Geiger·mode avalanche photodiode arrays integrated with CMOS readout circuits as a potential solution. This type of sensor counts photons digitally within the pixel, enabling data to be read out at high rates without the penalty of readout noise. After a brief overview of adaptive optics sensor development at Lincoln Laboratory, we will present the status of silicon Geiger· mode·APD technology along with future plans to improve performance.
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Summary

For adaptive optics systems, there is a growing demand for wavefront sensors that operate at higher frame rates and with more pixels while maintaining low readout noise. Lincoln Laboratory has been investigating Geiger·mode avalanche photodiode arrays integrated with CMOS readout circuits as a potential solution. This type of sensor counts...

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Hybridization process for back-illuminated silicon Geiger-mode avalanche photodiode arrays

Published in:
SPIE Vol. 7681, Advanced Photon Counting Techniques IV, 5 April 2010, 76810P.

Summary

We present a unique hybridization process that permits high-performance back-illuminated silicon Geiger-mode avalanche photodiodes (GM-APDs) to be bonded to custom CMOS readout integrated circuits (ROICs) - a hybridization approach that enables independent optimization of the GM-APD arrays and the ROICs. The process includes oxide bonding of silicon GM-APD arrays to a transparent support substrate followed by indium bump bonding of this layer to a signal-processing ROIC. This hybrid detector approach can be used to fabricate imagers with high-fill-factor pixels and enhanced quantum efficiency in the near infrared as well as large-pixel-count, small-pixel-pitch arrays with pixel-level signal processing. In addition, the oxide bonding is compatible with high-temperature processing steps that can be used to lower dark current and improve optical response in the ultraviolet.
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Summary

We present a unique hybridization process that permits high-performance back-illuminated silicon Geiger-mode avalanche photodiodes (GM-APDs) to be bonded to custom CMOS readout integrated circuits (ROICs) - a hybridization approach that enables independent optimization of the GM-APD arrays and the ROICs. The process includes oxide bonding of silicon GM-APD arrays to...

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Three-dimensional integration technology for advanced focal planes

Summary

We have developed a three-dimensional (3D) circuit integration technology that exploits the advantages of silicon-on-insulator (SOI) technology to enable wafer-level stacking and micrometer-scale electrical interconnection of fully fabricated circuit wafers. This paper describes the 3D technology and discusses some of the advanced focal plane arrays that have been built using it.
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Summary

We have developed a three-dimensional (3D) circuit integration technology that exploits the advantages of silicon-on-insulator (SOI) technology to enable wafer-level stacking and micrometer-scale electrical interconnection of fully fabricated circuit wafers. This paper describes the 3D technology and discusses some of the advanced focal plane arrays that have been built using...

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A multi-frame, megahertz CCD imager

Published in:
IEEE Trans. Nuclear Sci., Vol. 56, No. 3, June 2009, pp. 1188-1192.

Summary

The Los Alamos National Laboratory's Dual Axis Radiographic Hydrodynamic Test Facility (DARHT) generates flash radiographs of explosive experiments using two linear induction electron accelerators situated at right angles. The DARHT second axis accelerator generates an 18-MeV, 2 kA, 2 sec electron beam which is converted or "chopped" into four individual pulses ranging from 20 to 100 nsec in length at 2 MHz frequency. The individual electron beam pulses are down-converted by a segmented lutetium oxyorthosilicate scintillator, creating four visible light flashes, to image explosively driven events. To record these events, a high efficiency, high speed, imager has been fabricated which is capable of framing rates of 2 MHz. This device utilizes a 512 512 pixel charge coupled device (CCD) with a 25 cm2 active area, and incorporates an electronic shutter technology designed for back-illuminated CCD's, making this the largest and fastest back-illuminated CCD in the world. Characterizing an imager capable of this frame rate presents unique challenges. High speed LED drivers and intense radioactive sources are needed to perform basic measurements.We investigate properties normally associated with single-frame CCDs such as read noise, gain, full-well capacity, detective quantum efficiency (DQE), sensitivity, and linearity. In addition, we investigate several properties associated with the imager's multi-frame operation such as transient frame response and frame-to-frame isolation while contrasting our measurement techniques and results with more conventional devices.
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Summary

The Los Alamos National Laboratory's Dual Axis Radiographic Hydrodynamic Test Facility (DARHT) generates flash radiographs of explosive experiments using two linear induction electron accelerators situated at right angles. The DARHT second axis accelerator generates an 18-MeV, 2 kA, 2 sec electron beam which is converted or "chopped" into four individual...

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A 4-side tileable back illuminated 3D-integrated Mpixel CMOS image sensor

Summary

The dominant trend with conventional image sensors is toward scaled-down pixel sizes to increase spatial resolution and decrease chip size and cost. While highly capable chips, these monolithic image sensors devote substantial perimeter area to signal acquisition and control circuitry and trade off pixel complexity for fill factor. For applications such as wide-area persistent surveillance, reconnaissance, and astronomical sky surveys it is desirable to have simultaneous near-real-time imagery with fast, wide field-of-view coverage. Since the fabrication of a complex large-format sensor on a single piece of silicon is cost and yield-prohibitive and is limited to the wafer size, for these applications many smaller-sized image sensors are tiled together to realize very large arrays. Ideally the tiled image sensor has no missing pixels and the pixel pitch is continuous across the seam to minimize loss of information content. CCD-based imagers have been favored for these large mosaic arrays because of their low noise and high sensitivity, but CMOS-based image sensors bring architectural benefits, including electronic shutters, enhanced radiation tolerance, and higher data-rate digital outputs that are more easily scalable to larger arrays. In this report the first back-illuminated, 1 Mpixel, 3D-integrated CMOS image sensor with 8 mum-pitch 3D via connections. The chip employs a conventional pixel layout and requires 500 mum of perimeter silicon to house the support circuitry and protect the array from saw damage. In this paper we present a back-illuminated 1 Mpixel CMOS image sensor tile that includes a 64-channel vertically integrated ADC chip stack, and requires only a few pixels of silicon perimeter to the pixel array. The tile and system connector design support 4-side abuttability and fast burst data rates.
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Summary

The dominant trend with conventional image sensors is toward scaled-down pixel sizes to increase spatial resolution and decrease chip size and cost. While highly capable chips, these monolithic image sensors devote substantial perimeter area to signal acquisition and control circuitry and trade off pixel complexity for fill factor. For applications...

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A 64 x 64-pixel CMOS test chip for the development of large-format ultra-high-speed snapshot imagers

Summary

A 64 x 64-pixel test circuit was designed and fabricated in 0.18- m CMOS technology for investigating high-speed imaging with large-format imagers. Several features are integrated into the circuit architecture to achieve fast exposure times with low-skew and jitter for simultaneous pixel snapshots. These features include an H-tree clock distribution with local and global repeaters, single-edge trigger propagation, local exposure control, and current-steering sampling circuits. To evaluate the circuit performance, test structures are periodically located throughout the 64 x 64-pixel device. Measured devices have exposure times that can be varied between 75 ps to 305 ps with skew times for all pixels less than +-3 ps and jitter that is less than +-1.2 ps rms. Other performance characteristics are a readout noise of approximately 115 e- rms and an upper dynamic range of 310,000 e-.
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Summary

A 64 x 64-pixel test circuit was designed and fabricated in 0.18- m CMOS technology for investigating high-speed imaging with large-format imagers. Several features are integrated into the circuit architecture to achieve fast exposure times with low-skew and jitter for simultaneous pixel snapshots. These features include an H-tree clock distribution...

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Geiger-mode quad-cell array for adaptive optics

Published in:
CLEO-QELS, 2008 Conf. on Lasers and Electro-Optics/Quantum Electronics and Laser Science Conf., 4-9 May 2008.

Summary

We report an array of Shack-Hartmann wavefront sensors using high-fill-factor Geiger-mode avalanche detector quad cells hybridized to all-digital CMOS counting circuits. The absence of readout noise facilitates fast wavefront sensing at low light levels.
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Summary

We report an array of Shack-Hartmann wavefront sensors using high-fill-factor Geiger-mode avalanche detector quad cells hybridized to all-digital CMOS counting circuits. The absence of readout noise facilitates fast wavefront sensing at low light levels.

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Scaling three-dimensional SOI integrated-circuit technology

Published in:
2007 IEEE Int. SOI Conf. Proc., 1-4 October 2007, pp. 87-88.

Summary

Introduction At Lincoln Laboratory, we have established a three dimensional (3D) integrated circuit (IC) technology that has been developed and demonstrated over seven designs, bonding two or three active circuit layers or tiers to form monolithically integrated 3D circuits. Key features of our 3DIC technology include fully depleted SOI (FDSOI) circuit fabrication, low-temperature wafer-scale oxide-to-oxide bonding, precision wafer-to-wafer alignment, and dense unrestricted 3D vias interconnecting stacked circuit layers, successfully demonstrated in a large area 8 x 8 mm2 high-3D-via-count 1024 x 1024 visible imager. In this paper, we describe details of our bonding protocol for 150-mm diameter wafers, leading to a 50% increase in oxide-oxide bond strength and demonstration of +--0.5 am wafer-to-wafer alignment accuracy. We have established design rules for our 3DIC technology, have quantified process factors limiting our design-rule 3D via pitch, and have demonstrated next generation 3D vias with a 2x size reduction, stacked 3D vias, a backmetal interconnect process to reduce 2D circuit exclusion zones, and buried oxide (BOX) vias to allow both electrical and thermal substrate connections. All of these improvements will allow us to continue to reduce minimum 3D via pitch and reduce 2D layout limitations, making our 3DIC technology more attractive to a broader range of applications.
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Summary

Introduction At Lincoln Laboratory, we have established a three dimensional (3D) integrated circuit (IC) technology that has been developed and demonstrated over seven designs, bonding two or three active circuit layers or tiers to form monolithically integrated 3D circuits. Key features of our 3DIC technology include fully depleted SOI (FDSOI)...

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