AMAA 2012 Far Infrared Imaging Sensor for mass Production of Night Vision & Pedestrian Detection Systems Dr JL Tissot, E Bercier, P Robert, D Pochic, A. Arnaud*, JJ Yon* ULIS BP27-38113 Veurey-Voroize France *CEA/LETI 38054 Grenoble France Outline Automotive applications FIR imaging sensor Thermal imaging for automotive applications Non imaging applications Conclusion
FIR imaging sensors for automotive applications Far infrared (λ = 10 µm) is well adapted to pedestrian detection because of: High contrast based on object thermal detection Completely passive imaging system Two types of applications: Imaging applications Enhanced Driver Vision (EDV) Pedestrian Detection System (PDS) Short distance Detection applications Front & Back viewer Occupancy detection Imaging application Market forecasts Enhanced Driver Vision & Pedestrian Detection System Units / year 600 000 500 000 400 000 300 000 200 000 CAGR = + 61% 100 000 0 2011 2012 2013 2014 2015 2016 Tier 1 Aftermarket Forecasts from Yole Développement
Detection applications - Market forecasts It exists an important need of 2D arrays (# 64 x 64) which will be addressed mainly by microbolometer arrays and Thermopile arrays Units / year 25 000 000 20 000 000 15 000 000 THERMOGRAPHY AUTOMOTIVE COMMERCIAL SECURITY 10 000 000 5 000 000 BUILDING ENERGY Forecasts from Yole Développement 0 2012 2013 2014 2015 2016 2017 2018 2019 2020 Outline ABSORBER THERMOMETER Automotive applications THERMAL INSULATION FIR imaging sensor READOUT CIRCUIT Thermal imaging for automotive applications SIGNAL Non imaging applications Conclusion
FIR imaging sensor background Microbolometer Amorphous Pyroelectric silicon Ferroelectric (asi) Thermoelectric Vanadium Mechanical oxides (VOx) (µ-cantilever) Vacuum Packaging ABSORBER THERMOMETER IR THERMAL INSULATION READOUT CIRCUIT Thermal detector Uncooled detector SIGNAL Amorphous silicon background asi microbolometer: simple and uniform behavior R bolo =R 0.exp(E a /kt) Résistance (a.u.) 100 10 1-60 -40-20 0 20 40 60 80 100 Temperature ( C) E a distribution histogram asi 384 x 288 / 17µm array Uniform pixel behavior E a σ/m = 0.034%
Amorphous silicon background asi microbolometer: Predictable over large range -40 to +85 C operating temperature E a (ev) 0.20 0.18 0.16-40 -20 0 20 40 60 80 Bolometer temperature ( C) In addition to being very uniform over an array, E a is extremely stable with FPA temperature. Easier TEC-less operation Easier Shutter-less operation Amorphous silicon technology Only active layers in pixel structure Schematic pixel architecture Smaller suspended mass = Smaller thermal time constant Thermal time constant 10 ms + High thermal insulation (shorter leg length higher Fill Factor) + Low defect density & high uniformity
Microbolometer Readout IC Design IR I VDET Pixel Active bolometer Skimming Current voltage Conversion & Integration GAIN GFID «obscurity» V1 V2 V CTIA To Sampling VDDA VBUS Blind bolometer GSK Ground Signal = f(ir & bias) necessity to introduce a skimming function Amorphous silicon technology Pixel size (µm) 50 40 30 20 10 45 µm 35 µm 25 µm First image 12 µm April 2012 at mass production 17 µm Development 12 µm 2000 2004 2008 2012 Year Development of amorphous silicon technology at ULIS in cooperation with CEA / LETI
Outline Automotive applications FIR imaging sensor Thermal imaging for automotive applications Non imaging application Conclusion Imaging application Needs for a ¼ VGA imaging sensor currently tested by Tiers 1 and Equipment manufacturers Development of a new detector ¼ VGA / 17 µm pixel pitch
Imaging application Development of a new detector ¼ VGA / 17 µm pixel pitch 1 Current Skimming with Blind bolometer Pixel Array 384 x 288 17 µm Skimming TEST Device OTP Memory BIAS DIGITAL Internal BUS Sequencer Serial Link I2C MC PSYNC HSYNC VSYNC SCL SDA 2 Current Voltage Conversion 3 Sampling 4 Multiplexing to output stage Current Voltage Conversion & Integration Sampling Multiplexer Analog Interface Output Stage 14 bits ADC FPA FPA Temperature Temperature 2x7 bits VR+ VMC VR- Digital output Analog output VTEMP Imaging application with 384 x288 / 17 µm IRFPA Power consumption (mw) 150 100 50 2006 25 µm 2008 2010 17 µm 2012 Design date Improvement of ¼VGA power consumption (analog output)
Imaging application with 384 x288 / 17 µm IRFPA Device performance 10 20 30 40 50 60 70 80 NETD (mk) RFPN = 250 µv = 75% of rms noise Mean NETD* : 35 mk (f/1, 300 K, 30 Hz) Thermal time constant : 10 ms * NETD: Noise Equivalent Temperature Difference # detector sensitivity Imaging application with 384 x288 / 17 µm IRFPA Device performance
Outline Automotive applications FIR imaging sensor Thermal imaging for automotive Non imaging application Conclusion Non Imaging application with microbolometer NETD Size / pixel pitch Frame rate Uniformity Vacuum Operating range Manufacturability Thermopile/ Pyroelectric -- 0.15 C @1Hz, 100 C -- 100 to 250 µm -- + - Chip Level Package + + µbolometer ++ 0.05 C @50Hz, 20 C ++ 17 to 25 µm ++ + + Pixel Level Package ++ -40 C to +85 C + Comments Both require calibration process Both require vacuum package Performance stability over the operating temperature PIR detectors versus Microbolometer detectors Comparison
Microbolometer Packaging technology Packaging cost Metallic Ceramic Silicon Low volume Hard environment Qty > 10 4 Large volume Qty > 10 5 Very large volume Qty > 10 6 Ceramics packaging technology Vacuum Life time evaluation Storage temperature 90 C, 110 C, 130 C and 170 C Normalized Vacuum variation 1 0 100 200 300 400 500 600 700 800 Storage Time (days) Vacuum Life time > 15 years Compliant with Automotive Standards AEC-Q-100 Grade 3 (TC, HTSL) No getter activation = no maintenance
Silicon packaging technology: Pixel Level Packaging For small sensor generation Advanced vacuum Pixel Level Packaging Single-pixel micro-capsule Front end manufacturing process reflector Silicon packaging technology: Pixel Level Packaging 1 Sacrificial layer 3 Micro-capsule build up 5 Micro-capsule sealing and AR coating 2 Sacrificial layer etching 4 Micro-capsule evacuation Contact CMOS integrated Circuit Microbolometer membrane Reflector
Silicon packaging technology: Pixel Level Packaging First image / PLP April 2012 at Outline Automotive applications Uncooled IR Focal Plane Array Imaging automotive application Non imaging application Conclusion
Conclusion Key benefits of a-si a are extensive a-si physical properties Thin microbridge architecture / fast sensor Enhanced thermal insulation / fast & sensitive sensor Easy downscaling for small pixel a-si thin film uniformity a-si is Compatible with silicon technology for advanced packaging techniques Conclusion Key benefits of a-si a imaging sensor for automotive a-si paves the way to very large volume applications required by automotive security enhancement like: Long distance pedestrian detection (DVE) Short distance pedestrian detection (small arrays) Blind spot detection HVAC management & seat occupancy
Contact: Dr Jean-Luc Tissot Tel: +33 476 53 74 70 Email: jl.tissot@ulis-ir.com ULIS ZI les iles cordées BP 27 38113 Veurey-Voroize - France INNOVATION INTEGRITY PERFORMANCE SOLIDARITY