CMOS Image Sensor and Quanta Image

Sensors: Past, Present and FuturePresented

by

Yashashree WaseElectrical Engineering

Contact: ywase@uidaho.edu

Major Professor: James Frenzel, Ph.D., P.E.

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Outline

• Fundamentals of image sensors

• Review of CCD and CMOS technology

• Pixel architectures, widely commercialized pixels and comparison of pixel architectures

• Comparison of CCD and CMOS image sensors

• Applications and recent consumer products in the market

• Introduction to Quanta Image Sensor

• QIS progress review

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Image Sensor

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Fig. 1 Galaxy S5; a Samsung

S5K2P2XX 1/2.6” sensor with

an f/2.2 lens. Photo: iFixit

Fig. 2 Typical Camera

Modules on Mobile Phone

Fig. 3 CMOS Image Sensor Chip

Image Sensor Roadmap

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CCD was invented by Boyle

and Smith at AT&T Bell Labs

First Camera with built-in

CCD

CMOS APS Image Sensor at

NASA/JPL by E.Fossum

Worlds first fully digital

photographic camera

Quanta Image Sensor was

conceived

Quanta Image Sensor

research began from 2012 to

present

1950 1960 1970 1980 1990 2000 2010 2020 2030

MOS Photo-matrices

0th Generation Image Sensors

Charge Coupled Devices

1st Generation Image Sensors

CMOS ‘Camera On a Chip’

2nd Generation Image Sensors

QIS possible

3rd Generation

Film Photography

and vacuum tubes

Early CCD and CMOS

Research and Development

CCD

Commercialization CMOS Re-

emergence

Quanta Image Sensor

Research and Development

Charge Coupled Device

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By Michael Schmid - animated drawing created myself, CC BY

2.5,https://commons.wikimedia.org/w/index.php?curid=347838

• MOS-based CCDs are just like shift registers

• CCDs were the first solid state detectors

CCD Architecture has three basic

functions:a) Charge Collection

b) Charge transfer

c) The conversion of charge into a

measurable voltageFig. 4 Full-frame CCD array architecture

CMOS Image Sensor (CIS)

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Fig. 5 CMOS image sensor (CIS) Floorplan

Source: M. Bigas, E. Cabruja, J. Forest, and J. Salvi, “Review of CMOS image sensors.” Microelectronics Journal, 37(5):433-451, 2006

•“Achilles’ Heel” of CCD technology –

The need for perfect charge transfer

•Low power consumption

•High integration capability

•System-on-chip: miniaturization

•Cost-effective

Active Pixel Sensor (APS)

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• Active amplifier within a pixel

• 3T PD APS and 4T PD APS

• Transversal signal line (TSL)

• Overcomes SNR issue of PPS

• kTC noise exists

• Photodetection and photoconversion

regions are sameFig. 7 A 3T Photodiode type Active Pixel Sensor schematic

Source: M. Bigas, E. Cabruja, J. Forest, and J. Salvi, “Review of CMOS image sensors.” Microelectronics Journal, 37(5):433-451, 2006

Eric R. Fossum

Fig. 6 Active Pixel Sensor

Comparison Between Pixel ArchitecturePPS 3T-APS 4T-APS(PD) 4T-APS(PG) Log

SensitivityDepends on the

performance of a charge amp

Good Good Fairly GoodGood but poor at

low light level

Area consumption

Excellent Good Fairly Good Fairly Good Poor

Noise Fairly goodFairly good (no kTC

reduction)Excellent Excellent Poor

Dark Current Good Good Excellent Good Fairly good

Image LAG Fairly good Good Fairly good Fairly good Poor

Process Standard Standard Special Special Standard

NoteVery few

commercializedWidely

commercializedWidely

CommercializedVery few

CommercializedRecently

Commercialized

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Source: Jun Ohta, “Smart CMOS Inage Sensors and Applications,” CRC, 2008

Pinned Photodiode

• Addition of shallow p+ layer

• Fixed VPIN voltage based on doping

concentration

• High quantum efficiency

• Low dark current

• Lower pixel noise

• Low light imaging

• Widely used in industry

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Fig. 8 Cross section of pinned photodiode

Fig. 10 FSI PPD Potential well diagram

Fig. 9 BSI CMOS PPD

Geiger Mode APD

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Fig. 13 APD in standard CMOS technology

Source: Jun Ohta, “Smart CMOS Image

Sensors and Applications”, CRC 2008

• Single photon avalanche diode (SPAD)

• Ultra low light detection

Fig. 11 Transistor level diagram of pixel

Fig. 12 I-V characteristics of SPAD

Comparison of CCD and CMOS Sensors

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• CCD advantages over CMOS are the sensors’ higher quantum efficiency (QE) and generally

lower noise

• A strong advantage for CMOS technology is that it provides digital output and can be

controlled at the pixel level

• CMOS Camera-on-a-chip technology is better than CCDs because:

– Much lower power - important for portable applications

– System-on-a-chip integration allows smaller cameras

– Lower cost of sensor chip and fewer components in camera

– Easy digital interface for faster camera design & time to market

– Less image artifacts - no blooming or smear, with same sensitivity

– Higher dynamic range for security and auto applications

– Digital output for faster readout speeds and frame rates

– Direct addressing of pixels allows electronic pan/tilt/zoom

– Faster design cycles means faster evolution path

Recent Technologies and Development

• Dual Pixel Sensors

• EOS 70D: Dual Pixel CMOS AF

• Dual Sensitivity Pixel Technology

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Source: www.imaging-resource.com

Deep Trench Isolation

• In 2015, Deep Trench Isolation

in Iphone 6s and 6s plus for low

light image capture

• Hold electrons and avoid

leakage from pixel

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QuantumFilm by InVisage

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• QuantumFilm has a natural light response curve matching the

human eye

• High absorption capacity increases High Dynamic Range

• Thin layer, less crosstalk

Quanta Image Sensors

• Quanta Image Sensor concept was conceived in 2004

• Aim: Shrink pixel size

• “Count every photon that strikes the sensor” – E. Fossum

• Specialized photoelement: “Jot” (Greek for “smallest thing”)

• Sub-diffraction limit (SDL) pixels – Digital Camera Sensors

• Compatibility with a CMOS fabrication line

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Creating Image from Jots

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• Jots readout at 1000 fps resulting

series of bit planes

• This bit data results in the Jot

data cube as shown in Fig 16

• Image can be created from the

sum of a small x-y-t “cubicle”

• The cubicle determine the spatial

and temporal resolution of the

output image Fig. 17 Concept to obtain image from jots. From [3]

Jot Devices

• Pump-gate jot and bipolar-based jot

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Fig. 18 (a) Pump-gate jot schematic (b) TCAD simulation (c) Bipolar-based jot TCAD simulation. From [4]

(c)

Single Bit QIS Vs Multi-bit QIS

Single Bit Multi-bit

• Each jot produces 1 bit • Each jot produces n bits

• 1 bit ADC • n-bit ADC

• For same flux capacity,

need higher frame rate

readout

• For same flux capacity,

lower relative frame rate

1/2(𝑛−1)

• Conceptual simplicity,

easier on chip digital

electronics

• Like current CMOS APS but

low FW capacity and high

conversion gain

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QIS Vs Conventional CIS

• The major difference is sub-electron read noise and

photoelectron counting capability

• Improved CG and reduction in read noise

• QIS may be faster than conventional CIS

• QIS will consume less power than conventional CIS

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QIS Progress Review• Specialized SDL photodetectors called “jots”

• Low power readout of high volume data

• Implementation of pump-gate jot device in 65 nm CIS BSI

process yields

– Read noise as low as 0.22 e– r.m.s.

– Conversion gain (CG) as high as 420 µV / e-

– Power efficient readout electronics

– High dynamic range images from jot data

• Possible major paradigm shift in image capture

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References1] E.R. Fossum, “The Quanta Image Sensor (QIS): Concepts and Challenges” in Proc. 2011 Opt. Soc.

Am. Topical Meeting on Computational Optical Sensing and Imaging, Toronto, Canada July 10-14,

2011.

2] S. Masoodian, Y. Song, D. Hondongwa, JJ Ma, K. Odame and E.R. Fossum, “Early Research

Progress on Quanta Image Sensors”, in Proceedings of the 2013 International Image Sensor

Workshop, Snowbird, Utah USA June 12-16, 2013.

3]Zizza, R., “Jots to Pixels: Image Formation Options for the Quanta Image Sensor”, M.S. Thesis,

Thayer School of Engineering at Dartmouth College, Hanover, NH, USA, July 2015

4] Jiaju Ma, D. Hondongwa and E. R. Fossum, “Jot devices and the Quanta Image Sensor,” 2014

IEEE International Electron Devices Meeting, San Francisco, CA, 2014, pp. 10.1.1-10.1.4.

5] E.R. Fossum, J. Ma, S. Masoodian, L. Anzagira, and R. Zizza, “The Quanta Image Sensor: Every

Photon Counts”, MDPI Sensors, vol. 16, no. 8, 1260; August 2016. doi:10.3390/s16081260 (Special

Issue on Photon-Counting Image Sensors)

6] http://www.image-sensors-world.blogspot.com

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Thank you!

Your questions are valuable!

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