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Advanced CMOS Pixel Technology - Yashashree Wase
- 1. Advanced CMOS Pixel Technologies Presented by Yashashree Wase Graduate Student, Electrical Engineering Contact: ywase@uidaho.edu 15/19/2016 3:01 AM
- 2. Outline • CMOS image sensor (CIS) technology - Review • CMOS pixel types • Comparison between pixel architectures • Recent technologies and developments • Future prospects 5/19/2016 3:01 AM 2
- 3. CMOS Image Sensor (CIS) 35/19/2016 3:01 AM 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
- 4. CMOS Image Sensors Classification • Charge integration sensors • Passive pixel sensors(PPS) • Active pixel sensors(APS) • Non-integrating sensors • Retina-like sensors • Other functions • So many other architectures based on the applications 5/19/2016 3:01 AM 4 CMOS Image Sensor (CIS) Passive Pixel Active Pixel Hybrid Pixel PD-APS PPD-APSPG-APS HPDPG Dual PixelHybrid IRPD-PPS PG-PPS Log-APS CTIA-APS CAPS
- 5. First CMOS Imagers 5/19/2016 3:01 AM 5 A Photodiode type PPS schematic Source: M. Bigas, E. Cabruja, J. Forest, and J. Salvi, “Review of CMOS image sensors.” Microelectronics Journal, 37(5):433-451, 2006 • PPS pixel structure is similar to DRAM • Large fill factor • PPS are based on photodiodes without internal amplification • External readout circuitry on chip • Large smear • Large kTC noise • Large column FPN
- 6. Active Pixel Sensor (APS) 65/19/2016 3:01 AM • 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 same 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
- 7. Photogate-Type (PG) APS 75/19/2016 3:01 AM A Photogate type APS schematic Source: M. Bigas, E. Cabruja, J. Forest, and J. Salvi, “Review of CMOS image sensors.” Microelectronics Journal, 37(5):433-451, 2006 • Combines CCD charge transfer • Readout inside a pixel • Signal charge is integrated under photogate • Correlated Double Sampling (CDS) • High performance and low-light applications
- 8. Quick Comparison 5/19/2016 3:01 AM 8 Source: Photobit Tech., Eric Fossum, “CMOS Image Sensors.pdf”, http//:www.ericfossum.com
- 9. PPD APS and PPG APS • Pinned Photodiode and Pinned Photogate APS • Physical p+ layer – complex fabrication • Fixed VPIN voltage based on doping concentration • High quantum efficiency • Low dark current • Lower pixel noise • Widely used in industry • Low light imaging – astronomy and biotechnology 5/19/2016 3:01 AM 9
- 10. Photodiode-Type Logarithmic APS 5/19/2016 3:01 AM 10 A Photodiode type logarithmic APS schematic Source: M. Bigas, E. Cabruja, J. Forest, and J. Salvi, “Review of CMOS image sensors.” Microelectronics Journal, 37(5):433-451, 2006 • Non-integrating pixel • Logarithmic response – non-linear output • Increase on intrascene DR • High dynamic range Applications • Retina like sensors – silicon retinas • Slow response under low light • Large FPN
- 11. Comparison Between Pixel Architecture PPS 3T-APS 4T-APS(PD) 4T-APS(PG) Log Sensitivity Depends on the performance of a charge amp Good Good Fairly Good Good but poor at low light level Area consumption Excellent Good Fairly Good Fairly Good Poor Noise Fairly good Fairly 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 Note Very few commercialized Widely commercialized Widely Commercialized Very few Commercialized Recently Commercialized 5/19/2016 3:01 AM 11 Source: Jun Ohta, “Smart CMOS Inage Sensors and Applications,” CRC, 2008
- 12. Shared Pixel • Two-way shared PPD-APS – 2.5 T architecture • Four-way shared PPD-APS – 1.75 T architecture • Eight-way shared – 1.35 T architecture • PPD APS – 3T, 4T, 2.5T, 1.5T, 1T 5/19/2016 3:01 AM 12
- 13. PD-Type Shutter APS 5/19/2016 3:01 AM 13 • Addition of shutter transistor • High speed applications • Shutter efficiency is very high • Shutter node active pixel (SNAP) • CMOS SNAP (Efficiency>99.9%) • Global Shutter A Photodiode type shutter APS schematic Source: M. Bigas, E. Cabruja, J. Forest, and J. Salvi, “Review of CMOS image sensors.” Microelectronics Journal, 37(5):433-451, 2006
- 14. Thin Film on ASIC (TFA) Pixel 145/19/2016 3:01 AM • Higher absorption coefficient • Improve sensitivity • High dynamic range and high fill factor Source: M. Bigas, E. Cabruja, J. Forest, and J. Salvi, “Review of CMOS image sensors.” Microelectronics Journal, 37(5):433-451, 2006
- 15. PD-Type CAPS APS 155/19/2016 3:01 AM • Complimentary active pixels sensors • Reset transistor replaced by PMOS • Complimentary outputs Voutp & Voutn • Highly integrated • High performance • Alternative to conventional APS A Photodiode type CAPS schematic Source: M. Bigas, E. Cabruja, J. Forest, and J. Salvi, “Review of CMOS image sensors.” Microelectronics Journal, 37(5):433-451, 2006
- 16. PD-Type CTIAAPS 165/19/2016 3:01 AM • Capacitive transimpedance amplifier APS • Achieve low FPN by using divider circuit with switched capacitor voltage feedback A Photodiode type CTIAAPS schematic Source: M. Bigas, E. Cabruja, J. Forest, and J. Salvi, “Review of CMOS image sensors.” Microelectronics Journal, 37(5):433-451, 2006
- 17. Differential APS 175/19/2016 3:01 AM Differential APS Source: Jun Ohta, “Smart CMOS Image Sensors and Applications”, CRC 2008 • Suppress common mode noise • Uses pinned PD and PMOS SF • In-pixel CDS to reduce noise • Increased reset and readout noise • Ultra low light detection
- 18. Geiger Mode APD 5/19/2016 3:01 AM 18 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
- 19. CMOS APS SFG 5/19/2016 3:01 AM 19 J. Nakamura, S. E. Kemeny, and E. R. Fossum, “A CMOS active pixel image sensor with simple floating gate pixels,” IEEE Trans. Electron Devices, vol. 42, pp. 1693–1694, Sept. 1995 • Simple floating gate • No kTC noise and no image lag • High blooming overload protection • Non-destructive readout (NDRO) • Drawbacks of floating gate
- 20. Hybrid CMOS Pixels • Hybrid Photodiode-Photogate Pixel (HPDPG) 5/19/2016 3:01 AM 20 Standard Photodiode Pixels Source: SIIMPEL, Eric Fossum, “Adventures with Image Sensors.pdf”, http//:www.ericfossum.com
- 21. Recent Technologies and Development • Dual Pixel Sensors • EOS 70D: Dual Pixel CMOS AF • Dual Sensitivity Pixel Technology 215/19/2016 3:01 AM Source: www.imaging-resource.com
- 22. Future Prospects 225/19/2016 3:01 AM • JOT based sensors • Quantum Image Sensors • Quantum dots
- 23. Thank you! Your questions are valuable! 235/19/2016 3:01 AM