In this paper, we present an overview of high-performance CMOS image sensor products developed at BAE SYSTEMS
Imaging Solutions designed to satisfy the increasingly challenging technical requirements for image sensors used in
advanced scientific, industrial, and low light imaging applications. We discuss the design and present the test results of a
family of image sensors tailored for high imaging performance and capable of delivering sub-electron readout noise,
high dynamic range, low power, high frame rates, and high sensitivity. We briefly review the performance of the
CIS2051, a 5.5-Mpixel image sensor, which represents our first commercial CMOS image sensor product that
demonstrates the potential of our technology, then we present the performance characteristics of the CIS1021, a full HD
format CMOS image sensor capable of delivering sub-electron read noise performance at 50 fps frame rate at full HD
resolution. We also review the performance of the CIS1042, a 4-Mpixel image sensor which offers better than 70% QE
@ 600nm combined with better than 91dB intra scene dynamic range and about 1 e- read noise at 100 fps frame rate at
full resolution.
As bio-technology transitions from research and development to high volume production, dramatic improvements in
image sensor performance will be required to support the throughput and cost requirements of this market. This includes
higher resolution, higher frame rates, higher quantum efficiencies, increased system integration, lower read-noise, and
lower device costs. We present the performance of a recently developed low noise 2048(H) x 2048(V) CMOS image
sensor optimized for scientific applications such as life science imaging, microscopy, as well as industrial inspection
applications. The sensor architecture consists of two identical halves which can be operated independently and the
imaging array consists of 4T pixels with pinned photodiodes on a 6.5μm pitch with integrated micro-lens. The operation
of the sensor is programmable through a SPI interface. The measured peak quantum efficiency of the sensor is 73% at
600nm, and the read noise is about 1.1e- RMS at 100 fps data rate. The sensor features dual gain column parallel ouput
amplifiers with 11-bit single slope ADCs. The full well capacity is greater than 36ke-, the dark current is less than
7pA/cm2 at 20°C. The sensor achieves an intra-scene linear dynamic range of greater than 91dB (36000:1) at room
temperature.
We evaluate the effects of 10 MeV proton irradiation on the performance of a 5.5 Mpixel scientific grade CMOS image
sensor based on a 5T pixel architecture with pinned photodiode and transfer gate. The sensor has on-chip dual column
level amplifiers and 11-bit single slope analog to digital converters (ADC) for high speed readout and wide dynamic
range. The operation of the sensor is programmable and controlled by on-chip digital control modules. Since the image
sensor features two identical halves capable of operating independently, we used a mask to expose only one half of the
sensor to the proton beam, leaving the other half intact to serve as a reference. In addition, the pixel array and the digital
logic control section were irradiated separately, at dose rates varying from 4 rad/s to 367 rad/s, for a total accumulated
dose of 146 krad(Si) to assess the radiation effects on these key components of the image sensor. We report the resulting
damage effects on the performance of the sensor including increase in dark current, temporal noise, dark spikes,
transient effects and latch-up. The dark signal increased by about 55 e-/pixel after exposure to 14 krad (Si) and the dark
noise increased from about 2.75e- to 6.5e-. While the number of hot pixels increased by 6 percent and the dark signal
non uniformity degraded, no catastrophic failure mechanisms were observed during the tests, and the sensor did not
suffer from functional failures.
In this paper we present radiation studies performed on a low-noise, high-speed, largearea
CMOS image sensor (CIS) based on the 0.18 μm CMOS process. The sensor has
2560(H) x 2160(V) pixels with a readout speed of 100 frames/sec and a readout noise of
less than 2 e- rms. The sensor features 5T pinned photodiode pixels on a 6.5 μm pitch. In
order to measure the impact of radiation exposure on the sensor performance, the device
was subjected to x-ray exposure of 50 kRads of incident radiation using a broad band 50
KVP x-ray source to assess Total Ionizing Dose (TID) sensitivity. The active area and the
digital control block and amplification circuitry were separately irradiated to evaluate the
damage to each. Dark data was captured as a function of radiation dose in order to
measure dark current and offset changes in the signal.
In this paper we present radiation studies performed on a low-noise, high-speed, large-area CMOS
image sensor (CIS) based on the 0.18 μm CMOS process. The sensor has 2560(H) × 2160(V) pixels
with a readout speed of 100 frames/sec and a readout noise of less than 2 e- rms. The sensor features
5T pinned photodiode pixels on a 6.5 um pitch. In order to measure the impact of radiation exposure
on the sensor performance, the device was subjected to x-ray exposure of 50 kRads of incident
radiation using a broad band 50 KVP x-ray source to assess Total Ionizing Dose (TID) sensitivity.
The active area and the digital control block and amplification circuitry were separately irradiated to
evaluate the damage to each. Dark data was captured as a function of radiation dose in order to
measure dark current and offset changes in the signal.
KEYWORDS: Sensors, CMOS sensors, Modulation transfer functions, Camera shutters, Quantum efficiency, Diffusion, Infrared sensors, Analog electronics, Amplifiers, Sun
We present the performance of a CMOS image sensor optimized for next generation fused day/night vision systems.
The device features 5T pixels with pinned photodiodes on a 6.5μm pitch with integrated micro-lens. The 5T pixel
architecture enables both correlated double sampling (CDS) to reduce noise for night time operation, and a lateral antiblooming
drain for day time operation. The measured peak quantum efficiency of the sensor is above 55% at 600nm,
and the median read noise is less than 1e- RMS at room temperature. The sensor features dual gain 11-bit data output
ports and supports 30 fps and 60 fps. The full well capacity is greater than 30ke-, the dark current is less than 3.8pA/cm2
at 20ºC, and the MTF at 77 lp/mm is 0.4 at 550nm. The sensor also achieves an intra-scene linear dynamic range of
greater than 90dB (30000:1) for night time operation, and an inter-scene linear dynamic range of greater than 150dB for
complete day/night operability.
In this paper we describe a 5.5Mpixel 100 frames/sec wide-dynamic-range low-noise CMOS image sensor (CIS)
designed for scientific applications. The sensor has 6.5μm pitch 5T pixels with pinned photodiodes and integrated
microlenses. The 5T pixel architecture enables low noise rolling and global shutter operation. The measured peak
quantum efficiency of the sensor is greater than 55% at 550nm, the Nyquist MTF is greater than 0.4 at 550nm, and the
linear full well capacity is greater than 35ke-. The measured rolling and global shutter readout noise are 1.28e- RMS
and 2.54e- RMS respectively at 30 f/s and 20°C. The pinned photodiode dark current is less than 3.8pA/cm2 at 20°C.
The sensor achieves an intra-scene linear dynamic range in rolling shutter operation of greater than 86dB (20000:1) at
room temperature. In global shutter readout the shutter efficiency is greater than 1000:1 with 500nm illumination.
In this paper we present a VNIR solid state sensor technology suitable for next generation fused night vision systems.
This technology is based on a highly optimized low power 0.18um CMOS image sensor (CIS) process. We describe a
320(H) x 240(V) pixel prototype sensor based on this technology. The sensor features 5T pixels with pinned
photodiodes on a 6.5μm pitch with integrated micro-lens. The 5T pixel architecture enables both correlated double
sampling (CDS) and a lateral anti-blooming drain. The measured peak quantum efficiency of the sensor is greater than
50% at 600nm, and the read noise is less than 1e- RMS at room temperature. The sensor does not have any
multiplicative noise. The full well capacity is greater than 40ke-, the dark current is less than 3.8pA/cm2 at 20ºC, and the
MTF at 77 lp/mm is 0.4 at 600nm. The sensor also achieves an intra-scene linear dynamic range of greater than 90dB
(30000:1) at room temperature.
We present the design and test results of a prototype 4T CMOS image sensor fabricated in 0.18-μm technology
featuring 20 different 6.5 μm pixel pitch designs. We review the measured data which clearly show the impact of the
pixel topologies on sensor performance parameters such as conversion gain, read noise, dark current, full well capacity,
non-linearity, PRNU, DSNU, image lag, QE and MTF. Read noise of less than 1.5e- rms and peak QE greater than
70%, with microlens, are reported.
In this paper, we present an overview of large area detector arrays and new sensor technologies currently under development at Fairchild Imaging. We discuss on-going development efforts aimed at satisfying the increasing need for large format, scientific grade detectors, and review significant progress in achieving higher spatial resolution in large area back-illuminated CCDs. We also present the performance characteristics of a new prototype CCD/CMOS hybrid sensor designed for low light level imaging and capable of high speed, low power, and very low noise.
We present a CCD / CMOS hybrid focal plane array (FPA) for low light level imaging applications. The hybrid approach combines the best of CCD imaging characteristics (e.g. high quantum efficiency, low dark current, excellent uniformity, and low pixel cross talk) with the high speed, low power and ultra-low read noise of CMOS readout technology. The FPA is comprised of two CMOS readout integrated circuits (ROIC) that are bump bonded to a CCD imaging substrate. Each ROIC is an array of Capacitive Transimpedence Amplifiers (CTIA) that connect to the CCD columns via indium bumps. The proposed column parallel readout architecture eliminates the slow speed, high noise, and high power limitations of a conventional CCD. This results in a compact, low power, ultra-sensitive solid-state FPA that can be used in low light level applications such as live-cell microscopy and security cameras at room temperature operation. The prototype FPA has a 1280×1024 format with 12-um square pixels. Measured dark current is less than 5.8 pA/cm2 at room temperature and the overall read noise is as low as 2.9e at 30 frames/sec.
Fairchild Imaging has established a unique capability for high volume production of wafer-scale, scientific grade CCD (charge-coupled device) image sensors with active areas ranging from 6 x 6 cm, with 16 million pixels, to 8 x 8 cm devices with 85 million pixels. Large format back-illuminated CCDs are currently in volume production. This paper provides a detailed description of two recent products, and the technologies associated with their development.
Phosphor-coupled CCDs are established as one of the most successful technologies for x-ray diffraction. This application demands that the CCD simultaneously achieve both the highest possible sensitivity and high readout speeds. Recently, wafer-scale, back illuminated devices have become available which offer significantly higher quantum efficiency than conventional devices (the Fairchild Imaging CCD 486 BI). However, since back thinning significantly changes the electrical properties of the CCD the high speed operation of wafer-scale, back-illuminated devices is not well understood. Here we describe the operating characteristics (including noise, linearity, full well capacity and CTE) of the back-illuminated CCD 486 at readout speeds up to 4 MHz.
We have prototyped and characterized a very large format X-ray detector for macromolecular crystallography. The X-ray field strength is converted to visible light in a phosphor film. Light from the phosphor is focused onto a CCD imager by a lens specially designed for this detector, that has a very high numerical aperture. The CCD is very large (61 mm, 4,096 × 4,096 pixels), and employs a very low-noise on-chip preamplifier.
Lens coupling between phosphor film and CCD avoids many of the optical imperfections of fiber optic coupling, but it remains a challenge to make a lens system with optical transfer efficiency matching or exceeding that of fiber optical systems. We have met this challenge by enhancing system gain in our detector through implementation of modern lens technologies and imaginative CCD design. At this point the system gain equals that of conventional CCD-based X-ray crystallography detectors, which couple the CCD to the phosphor through a fiber optic taper. Although many of our technical developments could also be used in fiber optic detectors, the overriding virtues of the lens-couple detector are simplicity, optical perfection, and cost.
The University of Arizona Imaging Technology Laboratory has processed 4096 X 4096 15-micron Charge Coupled Devices (CCDs) fabricated at Lockheed Martin Fairchild Systems for back illuminated scientific applications. The devices have been optimized for astronomical observations in a direct imaging mode. Three types of back illuminated devices have been developed. The oldest devices are CCD4096JJ detectors which were custom fabricated for astronomical applications. The CCD485 devices are commercial sensors, originally fabricated for digital photography and medical applications. Because no frontside ground contact was included on either device, a backside contact was developed and applied as part of the backside processing. With this addition, very high quality back illuminated sensors have been developed. The CCD486 is a newer version of the 4k by 4k CCD with low noise amplifiers and a backside contact. These sensors have now been produced back illuminated with > 90 percent QE and read noise under 4 electrons. The devices show CTE of > 0.999998. Back illuminated versions CCDs have been fabricated with peak-valley flatness non-uniformity of less than 10 microns. A new epoxy underfill technique was developed to achieve this flatness and to avoid underfill voiding during epoxy application and curing. The new method applies a contact force on the CCD during the entire 48 hour cycle.
Davis Lange, Paul Vu, Samuel Wang, Steven Jost, Michael Winn, John Roussis, Robert Cook, Darrel Endres, Gregg Dudoff, Colin Jones, Glenn Kincaid, Jeffery Heath
This paper discusses the design, architecture, and performance of a 6000 element Indium Antimonide Infrared focal plane array. The focal plane array architecture allows for any N x 1000 element sized array to be constructed from its base elements. A uniquely constructed bi-staggered detector geometry is utilized to provide 2:1 over-sampling having 10 micron effective pitch in both the across track and along track directions. Additionally, the detector geometry allows for physical pixel sizes up to 25 microns while sampling at a 10 micron effective pitch to provide alias free imaging with the high signal capture capability of a large pixel. The Indium Antimonide detectors are front-side illuminated P-on-N type mesa diodes having no measurable crosstalk. A complimentary CMOS based Multiplexor in a M x 250 segmented design having up to 10 million electrons full-well output with greater than 14 bits instantaneous dynamic range provides a flexible and low noise readout for the focal plane array. Hybridization of the Indium Antimonide detectors and multiplexor is provided via a Lockheed Martin patented beam-lead technology to provide reliable and producible long linear focal plane arrays for reconnaissance applications. Characterization of the 6000 element Infrared focal plane array is presented including dynamic impedance of the diodes, read-noise, linearity, and non-uniformity. Meadured characteristics of the CMOS multiplexor are also presented in addition to data from the hybridized modules making up the Focal Plane Array.
We present data from a charge-coupled device (CCD), collaboratively designed by PSU/JPL/Loral, which incorporates several novel features that make it well suited for soft X-ray spectroscopy. It is a three-phase, front-side illuminated device with 1024x1024 pixels. Each pixel is 18 microns by 18 microns.The device has four output amplifiers: two conventional floating diffusion amplifiers (FDAs) and two floating gate amplifiers (FGAs). The FGA non-destructively samples the output charge, allowing the charge in each pixel to be measured multiple times. The readnoise of a given pixel is reduced as the square root of the number of readouts, allowing one to reduce the amplifier noise of these devices to well below the 1/f knee. We have been able to achieve sub-electron readnoise performance with the floating gate amplifier (0.9 e+-) rms with 16 reads per pixel). Using the FGA, the measured energy resolution at 5.9 keV is 120 eV (FWHM). The CCD also has a thin poly gate structure to maximize soft X-ray quantum efficiency. Two-thirds of the active area of the chip is covered only by an insulating layer (1000 angstrom) and a thin poly silicon electrode (400 angstrom). This design enhances the soft X-ray quantum efficiency, but retains the excellent charge transfer efficiency and soft X-ray charge collection efficiency of front-side illuminated devices. The measured energy resolution at 277 eV is 38 eV (FWHM) with a measured quantum efficiency of 15%. We also show that this device performs well below 100 eV, as demonstrated by the detection of Al L fluorescence at 72 eV with a measured FWHM of 16 eV.
KEYWORDS: Sensors, Signal processing, Detector arrays, Charge-coupled devices, CCD image sensors, Optical signal processing, High dynamic range imaging, Acousto-optics, Photodetectors, Signal detection
Efforts to improve the state-of-the-art in charge-coupled device (CCD) detector arrays for acoustooptic applications have had considerable success. A program for the improvement of detectors for acoustooptic applications sponsored by Harry Diamond Laboratories in conjunction with Loral Fairchild Imaging Sensors, formerly Fairchild Weston Systems, is aimed at increasing high speed CCD detector dynamic range to over 65 dB. Other device specifications such as crosstalk and image lag are being addressed in order to match the increased dynamic range performance in a 1024 element detector. This paper outlines the key device specifications which needed to be addressed, the methods used to achieve improved performance in these areas, the testing considerations, and the results of recent device testing.
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