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Infrared Detector & ASIC Technology Markus Loose STScI, May 8, 2014.

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Presentation on theme: "Infrared Detector & ASIC Technology Markus Loose STScI, May 8, 2014."— Presentation transcript:

1 Infrared Detector & ASIC Technology Markus Loose STScI, May 8, 2014

2 Outline May 08, 2014STScI Lecture2 CMOS-based Detectors (infrared) – General Properties of Solid State Detectors – CMOS-based Multiplexers – Examples Control ASICs – General Description – Example: SIDECAR ASIC – Preamp, Biases, ADCs – Noise performance and issues Conclusion

3 CMOS-based Infrared Sensors May 08, 2014STScI Lecture3 ( CMOS: Complimentary Metal Oxide Silicon )

4 The Ideal Detector Detect 100% of photons Each photon detected as a delta function Large number of pixels Time tag for each photon Measure photon wavelength Measure photon polarization Oct 15, 20094Scientific Detector Workshop, Garching, Germany Up to 98% quantum efficiency One electron for each photon gfdg ~1,400 million pixels (>10 9 )  No - framing detectors  No – defined by filter Plus Read Noise and other “Features”

5 May 08, 2014STScI Lecture5 Hybrid Imager Architecture Image of indium bump array in comparison to human hair (credit: Laser Focus World) Image of indium bump array in comparison to human hair (credit: Laser Focus World)

6 Energy of a Photon May 08, 2014STScI Lecture6 Energy of photons is measured in electron-volts (eV) eV = energy that an electron gets when it “falls” through a 1 Volt field.

7 An Electron-Volt (eV) is extremely small May 08, 2014STScI Lecture7 1 eV = J (J = joule) 1 J = N m = kg m sec -2 m 1 kg raised 1 meter = 9.8 J = eV 1 eV = J (J = joule) 1 J = N m = kg m sec -2 m 1 kg raised 1 meter = 9.8 J = eV The energy of a photon is VERY small –The energy of a SWIR (2.5  m) photon is 0.5 eV Drop a peanut M&M ® candy from a height of 2 inches –Energy is equal to 6 x eV (a peanut M&M ® is ~2 g) –This is equal to 1.2 x SWIR photons 1 million x 1 million x 12,000 The number of photons that will be detected in ~1 million images from the James Webb Space Telescope (JWST) A 2-inch peanut M&M ® drop is more energy than will be detected during the entire 5-10 year lifetime of the JWST !

8 Photon Detection May 08, 2014STScI Lecture8 Conduction Band Valence Band EgEg For an electron to be excited from the conduction band to the valence band h > E g h = Planck constant ( Joulesec) n = frequency of light (cycles/sec) = /c E g = energy gap of material (electron-volts) c = / E g (eV)

9 May 08, 2014STScI Lecture9 CCD Approach CMOS Approach Pixel Charge generation & charge integration Charge generation, charge integration & charge-to-voltage conversion + Photodiode Amplifier Array Readout Charge transfer from pixel to pixel Multiplexing of pixel voltages: Successively connect amplifiers to common bus Sensor Output Output amplifier performs charge-to-voltage conversion Various options possible: - no further circuitry (analog out) - add. amplifiers (analog output) - A/D conversion (digital output) General CMOS Detector Concept

10 General Architecture of CMOS-Based Image Sensors May 08, 2014STScI Lecture 10 Pixel Array Horizontal Scanner / Column Buffers Vertical Scanner for Row Selection Control & Timing Logic (optional) Bias Generation & DACs (optional) Analog Amplification A/D conversion (optional) Analog Output Digital Output

11 IR Multiplexer Pixel Architecture May 08, 2014STScI Lecture11 V dd amp drain voltage V dd amp drain voltage Output Detector Substrate Photvoltaic Detector

12 IR Multiplexer Pixel Architecture May 08, 2014STScI Lecture12 V dd amp drain voltage V dd amp drain voltage Output Detector Substrate Photvoltaic Detector V reset reset voltage V reset reset voltage Reset

13 IR Multiplexer Pixel Architecture May 08, 2014STScI Lecture13 Output Detector Substrate Photvoltaic Detector V reset reset voltage V reset reset voltage Reset V dd amp drain voltage V dd amp drain voltage Enable “Clock” (red) “Bias voltage” (purple)

14 May 08, 2014STScI Lecture14 Special Scanning Techniques in CMOS Different scanning methods are available to reduce the number of pixels being read: – Allows for higher frame rate or lower pixel rate (reduction in noise) – Can reduce power consumption due to reduced data

15 Possible Reset Schemes for HxRG May 08, 2014STScI Lecture15 Reticle Stitched CMOS Sensor

16 Astronomy Application: Guiding May 08, 2014STScI Lecture16 Special windowing can be used to perform full- field science integration in parallel with fast window reads.  Simultaneous guide operation and science data capture within the same detector. Full field rowWindowFull field row Window Full field row Two methods possible: –Interleaved reading of full-field and window No scanning restrictions or crosstalk issues Overhead reduces full-field frame rate –Parallel reading of full-field and window Requires additional output channel Parallel read may cause crosstalk or conflict No overhead  maintains maximum full-field frame rate

17 Guide Mode Demonstration May 08, 2014STScI Lecture17 Video shows a small window in the center, read frequently for guiding, while the full field is read slowly in the background

18 May 08, 2014STScI Lecture18 H A W A I I - 2 R G H gCdTe A stronomy W ide A rea I nfrared I mager with 2 k 2 Resolution, R eference pixels and G uide Mode 2k x 2k HAWAII-2RG with HyViSI detector 2 x 2 Mosaic of HAWAII-2RG detectors Teledyne HAWAII-2RG Hybrid Detector Array

19 May 08, 2014STScI Lecture19 All pads located on one side (top) Approx. 110 doubled I/O pads (probing and bonding) Three-side close buttable 18 µm pixels Total dimensions: 39 x 40.5 mm² H2RG Block Diagram

20 May 08, 2014STScI Lecture20 JWST - James Webb Space Telescope 15 Teledyne 2K×2K infrared arrays on board (~63 million pixels) International collaboration 6.5 meter primary mirror and tennis court size sunshield 2018 launch on Ariane 5 rocket L2 orbit (2.4 million km from Earth) Two 2x2 mosaics of SWIR 2Kx2K Two individual MWIR 2Kx2K NIRCam (Near Infrared Camera) Wide field imager Studies morphology of objects and structure of the universe U. Arizona / Lockheed Martin Spectrograph Measures chemical composition, temperature and velocity European Space Agency / NASA NIRSpec (Near Infrared Spectrograph) 1x2 mosaic of MWIR 2Kx2K FGS / NIRISS (Fine Guidance Sensors / Near-Infrared Imager and Slitless Spectrograph) Acquisition and guiding Images guide stars for telescope stabilization Canadian Space Agency 3 individual MWIR 2Kx2K

21 May 08, 2014STScI Lecture21 Control ASICs

22 How to Operate an Image Sensor? Sensor/Detector requires: – DC bias and reference voltages Set properties like offset, bandwidth, reverse detector bias Voltages need to be programmable to allow optimal performance Very low noise to not contribute to the read noise (< 10µV noise) – Clocks/Digital control signals Responsible for controlling the readout timing and sensor configuration Configurable timing required – Video Signal Readout If digital output sensor, job is mostly done. Simply route to FPGA for data acquisition and storage If analog output sensor: – Amplify/buffer analog signal – Perform analog-to-digital conversion, then route digital data to FPGA May 08, 2014STScI Lecture22

23 ASIC as Control Electronics May 08, 2014STScI Lecture23 Replace this with this! 1% volume 1% power 1% hassle

24 May 08, 2014STScI Lecture24 S ystem for I mage D igitization, E nhancement, C ontrol A nd R etrieval SIDECAR ASIC Architecture

25 May 08, 2014STScI Lecture25 SIDECAR ASIC Features 36 analog input channels, each channel provides: – 500 kHz A/D conversion with 16 bit resolution – 10 MHz A/D conversion with 12 bit resolution – gain = 0 dB …. 27 dB in steps of 3 dB – optional low-pass filter with programmable cutoff – optional internal current source (as source follower load) 20 analog output channels, each channel provides: – programmable output voltage and driver strength – programmable current source or current sink – internal reference generation (bandgap or vdd) 32 digital I/O channels to generate clock patterns, each channel provides: – input / output / high-ohmic – selectable output driver strength and polarity – pattern generator (16 bit pattern) independent of microcontroller – programmable delay (1ns - 250µs) 16 bit low-power microprocessor core (single event upset proof) – responsible for timing generation and data processing – 16 kwords program memory (32 kByte) and 8 kwords data memory (16 kByte) – 36 kwords ADC data memory, 24 bit per word (108 kByte) – additional array processor for adding, shifting and multiplying on all 36 data channels in parallel (e.g. on-chip CDS, leaky memory or other data processing tasks)

26 May 08, 2014STScI Lecture26 SIDECAR Operating a HAWAII-2RG / 1RG PC Software for SIDECAR Control and Data Capture PCI Card or USB interface Vreset Dsub Clock 000 w 384 w 0cd w HAWAII-2RG SIDECAR ASIC Analog Supply Data In Data Out Master Clock Digital Supply 3.3V Analog Video Biases Power Supply Serial Interface Clocks Only 7 lines needed to operate the SIDECAR ASIC in base configuration (3 signal & 4 power lines) The SIDECAR ASIC provides all 27 signals required to operate the HAWAII-2RG The microcontroller driven SIDECAR ASIC generates all biases & clocks and digitizes the analog video outputs Sensor Chip Assembly Inside the dewar at cryogenic temperatures

27 May 08, 2014STScI Lecture27 SIDECAR ASIC Flight Package for JWST Ceramic board with ASIC die and decoupling caps Invar box with top and bottom lid Two 37-pin MDM connectors – FPE-to-ASIC connection – ASIC-to-SCA connection Qualified to NASA Technology Readiness Level 6 (TRL-6) 15 mW power when reading out of four ports in parallel, with 16 bit digitization at 100 kHz per port. FPE side SCA side SIDECAR Comparison: LGA Package ACS (HST)

28 May 08, 2014STScI Lecture28 Missions Employing SIDECAR ASICs James Webb Space Telescope – NIRCam, NIRSpec, FGS/NIRISS instruments – H2RG IR detectors, T = 38K (ASIC), planned launch in 2018 Hubble Space Telescope – ACS (Advanced Camera for Surveys) – CCD detector, T = 300K (ASIC), launched in 2009 Landsat Data Continuity Mission – TIRS (Thermal InfraRed Sensor) instrument – QWIP detector, T = 300K (ASIC), launched in 2013 OSIRIS-REx Asteroid Mission – OVIRS (OSIRIS-REx Visible and IR Spectrometer) instrument – H1RG IR detector, T = 300K (ASIC), planned launch in 2016 Euclid Mission – NISP (Near IR Spectrometer Photometer) instrument – H2RG IR detector, T = ~140K (ASIC), planned launch in 2020 MOSFIRE (Multi-Object Spectrometer For Infra-Red Exploration) – H2RG IR detector, T < 120K (ASIC), deployed at the Keck Telescope FourStar Wide Field Infrared Camera – H2RG IR detector, T < 120K (ASIC), deployed at the Magellan Baade 6.5m Telescope JWST HST LDCM OSIRIS-REx Euclid

29 May 08, 2014STScI Lecture29 Pre-Amplifier Block Diagram Capacitor Feedback Design Gain programmable by setting Cin and Cfb Gain = Cin/Cfb Low pass filter with programmable cutoff

30 May 08, 2014STScI Lecture30 Preamp Drift and Mitigation Data taken as 512 x 64 frames for efficiency, Gain = 4 Drift kTC row noise kTC removed (CCD mode) σ= 52 ADU σ= 2.6 ADU σ= 13.9 ADU

31 May 08, 2014STScI Lecture31 Noise Reduction by Using Multiple ADC Channels 1 ADC 2 ADCs 4 ADCs 6 ADCs 8 ADCs PreAmp inputs shorted to ground (lowest noise signal in order to be dominated by ADC noise) PreAmp gain set to 4 (12 dB) Noise measured by using multiple preamp and ADC channels in parallel (1, 2, 4, 6, and 8) Noise reduces almost as the square root of the number of channels used

32 Bias Generator Block Diagram SIDECAR has 20 Channels Each Channel provides programmable voltage and current sources Noise is caused mostly by buffer (1/f noise of MOS transistors) Drive strength of buffer can be adjusted to modulate the bandwidth Feedback compensation can be adjusted for stability Buffer can be configured for single or dual stage operation => Tuning required for optimal noise performance May 08, 2014STScI Lecture32

33 May 08, 2014STScI Lecture33 Bias Generator Noise Bias output 1 routed back into PreAmp PreAmp gain set to 22 (27 dB) Use 4 ADCs in parallel to reduce PreAmp & ADC noise Noise on bias without filtering is about 35µV (11.6 ADU) Noise can be reduced by RC filtering to less than 5µV Bias noise as a function of RC filter time constant PreAmp & ADC noise floor Unfiltered Noise of Bias Output 1 Filtered Noise of Bias Output 1 (t RC = 360 ms)

34 May 08, 2014STScI Lecture34 Noise Power Spectrum of the Bias Outputs FFT of temporal noise measurement with RC filter set to t RC = 3 µ s FFT of temporal noise measurement with RC filter set to t RC = 3 ms

35 May 08, 2014STScI Lecture35 FFT of temporal noise measurement with RC filter set to t RC = 360ms FFT of temporal noise measurement with grounded PreAmp inputs (i.e. noise floor) Noise Power Spectrum of the Bias Outputs, Part 2

36 May 08, 2014STScI Lecture36 Analog-to-Digital Conversion Quantization noise of an ADC is (1/ √ 12) Least Significant Bit = LSB Typically set gain of amplifier chain so that quantization noise is much less than readout noise. If readout noise is 4 electrons, set gain so that LSB equals ~2 electrons 16 bit ADC is most commonly used in astronomy. At ~2 electrons per ADU (analog to digital unit), or LSB, full well of a 16 bit ADC will be ~130,000 electrons; good match to the typical full well of a CCD or Short-Wave IR detector of 100,000 electrons. Highly exaggerated quantization noise “Don’t do this at home”

37 May 08, 2014STScI Lecture37 Differential Non-Linearity (DNL) DNL = (V D+1 – V D ) / V LSB-Ideal – 1 Code 10 is missing DNL = -1 Code 10 is reduced DNL = -0.5 Code 100 is increased DNL = +1 DNL describes the distance of an ADC code from its adjacent code. It is measured as a change in input voltage magnitude, and then converted to number of Least Significant Bits (LSBs).

38 May 08, 2014STScI Lecture38 Integral Non-Linearity (INL) INL describes the deviation of the ADC transfer function from a straight line It can be computed as the integral of the DNL, and is expressed in LSB INL = (V D – V Zero ) / V LSB-Ideal – D

39 May 08, 2014STScI Lecture39 16-bit ADC Linearity Output Code DNL [ LSB ] DNL Output Code INL [ LSB ] INL Differential Non-Linearity: < ± 0.3 LSB Integral Non-Linearity: < ± 0.2 LSB Temporal Noise: 2.7 LSB

40 May 08, 2014STScI Lecture40 ADC Linearity Pitfalls Optimal Vcm Vcm off by 80 mV Vcm off by 160 mV Differential ADC is composed of 2 separate single-ended ADCs – If one of the two ADCs saturates before the second one does, the transfer slope changes by 2 Slope change Requires careful adjustment of the ADC reference and common mode voltages Simultaneous optimal tuning for all channels does not exist due to component mismatch Avoid lower and upper end of ADC for science

41 May 08, 2014STScI Lecture41 1/F Noise in NIRSpec/JWST Traditional CDS Optimal CDS σ CDS ~ 18 e- rmsσ CDS ~ 8 e- rms

42 May 08, 2014STScI Lecture42 IRS^2 Noise Reduction Mode Example: NIRSpec 1000s Dark Up-the-Ramp Signal Improved Reference Sampling & Subtraction (IRS^2) is a method to utilized reference pixels in a more efficient way – In every output channel, read reference pixels from the top or bottom or rows in- between the regular science pixels (e.g. read 4 reference pixels every 16 science pixels) – Use Fourier analysis to determine the frequency-dependent correlation between signal and reference pixels, and subtract the reference pixel signal accordingly Nominal (no IRS^2)IRS^2 (using real pixels as reference)

43 May 08, 2014STScI Lecture43 ACS 1/f Noise Bias Frame without correction (superbias subtracted) Bias Frame with correction (superbias subtracted)

44 Conclusion Infrared Detectors (Image Sensors) – Hybrid design: Detector material bump-bonded to readout chip – Different detector materials possible HgCdTe for astronomy: lowest dark current and adjustable bandgap – Flexible readout options like guide mode or single-pixel reset Control ASICs – Provide all functions to operate the detector Clocking, Biasing, A/D conversion – Single-chip solution in contrast to discrete electronics Lower power, space, weight – Can run cryogenically (next to the cooled detector) – Performance Improvements desired (lower noise, no artifacts) May 08, 2014STScI Lecture44

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