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Near-Infrared Detector Arrays - The State of the Art -

Near-Infrared Detector Arrays - The State of the Art -. Klaus W. Hodapp Institute for Astronomy University of Hawaii. Historic Milestones. 1800: Infrared radiation discovered 1960s and 70s: Single detectors (PbS, InSb …) 1980s: First infrared arrays (32 2 , 58 62, 64 2 , 128 2 )

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Near-Infrared Detector Arrays - The State of the Art -

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  1. Near-Infrared Detector Arrays- The State of the Art - Klaus W. Hodapp Institute for Astronomy University of Hawaii

  2. Historic Milestones • 1800: Infrared radiation discovered • 1960s and 70s: Single detectors (PbS, InSb …) • 1980s: First infrared arrays (322, 5862, 642, 1282) • 1990: NICMOS-3 (2.5m PACE-1 HgCdTe) • 1991: SBRC 2562 (InSb) • 1994: HAWAII-1 (2.5m PACE-1 HgCdTe) • 1995: Aladdin (InSb) • 2000: HAWAII-2 (2.5m PACE-1 HgCdTe) • 2002: HAWAII-1RG (5.0μm MBE HgCdTe) • 2002: HAWAII-2RG (5.0μm MBE HgCdTe) • 2002: RIO 2K×2K NGST InSb • 2002: RIO 2K×2K Orion

  3. Hawaii-2RG Heritage All Successfully Developed on 1st Design Pass NICMOS PICNIC HAWAII 1987 1994 1990 1994 2000 1998 -2 -1 4.2 million pixels >13 million FETs Expect CDS <10e- -1R 65,536 pixels 250,000 FETs CDS: <30e- 16,384 pixels 70,000 FETs CDS: <50e- 65,536 pixels 250,000 FETs CDS: <20e- 1.05 million pixels >3.4 million FETs CDS: <10e- CDS: <TBD e- HAWAII-2RG Exploiting Many Lessons Learned to Minimize Development Risk And Enable Next Generation Performance Transition to 0.25µm CMOS With Full Wafer Stitching and Low-Power System-on-Chip ASIC

  4. Infrared Arrays • Diode Array • Multiplexer • Readout Electronics

  5. n p Electric Field in a CCD 1. The n-type layer contains an excess of electrons that diffuse into the p-layer. The p-layer contains an excess of holes that diffuse into the n-layer. This structure is identical to that of a diode junction. The diffusion creates a charge imbalance and induces an internal electric field. The electric potential reaches a maximum just inside the n-layer, and it is here that any photo-generated electrons will collect. All science CCDs have this junction structure, known as a ‘Buried Channel’. It has the advantage of keeping the photo-electrons confined away from the surface of the CCD where they could become trapped. It also reduces the amount of thermally generated noise (dark current). Electric potential Electric potential Potential along this line shown in graph above. Cross section through the thickness of the CCD

  6. p-type silicon n-type silicon Charge Collection in a CCD. Photons entering the CCD create electron-hole pairs. The electrons are then attracted towards the most positive potential in the device where they create ‘charge packets’. Each packet corresponds to one pixel pixel boundary pixel boundary incoming photons Electrode Structure Charge packet SiO2 Insulating layer

  7. NIR Photodiode Array Technologies • Problems: • Substrate availability • Thermal expansion match to Si • Lattice match to detector material • LPE HgCdTe on Sapphire (PACE-1): Rockwell, CdTe buffer • MBE HgCdTe on CdZnTe: Rockwell, thin or substrate removed, AR coated • InSb (Raytheon): Bulk material, p-on-n, thinned, AR coated • LPE HgCdTe on CdZnTe: Raytheon, thick • MBE HgCdTe on Si: Raytheon, ZnTe and CdTe buffer, thick, thin in future

  8. Open Shutter Close Shutter 0.5 V Reset Reset Diode Bias Voltage kTC Noise Reset-Read Sampling Readout 0 V Time

  9. Recharge Noise in Capacitors Energy stored in a capacitor: E = ½ Q²/C Noise Energy must be: E_n = ½kT Noise Charge: ½ (Q_n)²/C = ½kT (Q_n)² = kTC Q_n = √ kTC

  10. Example: Capacitance: 50 fF, T=37 K k = 1.38 e-23 J/K Q_n = √ kTC Q_n = 5 e-18 C With q_e = 1.6 e-19 C Q_n = 32 electrons rms

  11. Open Shutter Close Shutter kTCnoise 0.5 V Reset Reset Readout Diode Bias Voltage CDS Signal Double Correlated Sampling Readout 0 V Time

  12. Open Shutter Close Shutter kTCnoise 0.5 V Reset Reset Readout Diode Bias Voltage MCS Signal Fowler (multi) Sampling Readout 0 V Time

  13. Open Shutter Close Shutter kTCnoise 0.5 V Reset Reset Diode Bias Voltage MCS Signal Up-the-ramp Readout Up-the-Ramp Sampling 0 V Time

  14. HAWAII-2: Photolithographically Abut 4 CMOS Reticles to Produce Each 20482 ROIC Twelve 20482 ROICs per 8” Wafer 20482 Readout Provides Low Read Noise for Visible and MWIR

  15. External JFETs optimized

  16. HAWAII-1Rockwell Science Center • 10241024 2.5m HgCdTe detector array • 4 Quadrant architecture • 4 Output amplifiers • 18.5 m pixels • LPE HgCdTe on sapphire (PACE-1) • Use of external JFETs possible • Available for purchase

  17. HAWAII-1 Focal Plane Array

  18. HAWAII-1 • Quantum efficiency (50% - 60%) • Dark current 0.01 e-/s (65K) • Read noise about 10 - 15 e- rms CDS • Residual image effect • Some multiplexer glow • Fringing

  19. 3600 s 128 samp T= 65K

  20. Internal FETs

  21. External JFETs optimized

  22. Fringing in PACE-1 material

  23. 1997 1998 Residual Images in PACE-1 HAWAII-1 Arrays

  24. AladdinRaytheon Center for Infrared Excellence • 10241024 InSb detector array • 4 Quadrant architecture • 32 Output amplifiers • 27 m pixels • Thinned, AR coated InSb • Three generations of multiplexers • “Foundry Run” distribution mode

  25. Aladdin • Quantum efficiency high (80% - 90%) • Dark current 0.2 - 1.0 e-/s • Read noise about 40 e- rms CDS • Charge capacity 200,000 e- • Residual image effect • No amplifier glow

  26. Aladdin frame taken with SPEX (J. Rayner)

  27. NIRI Aladdin Image of AFGL2591

  28. HAWAII-2Rockwell Science Center • 20482048 2.5m HgCdTe detector array • 4 Quadrant architecture • 32 Output amplifiers • 3 Output modes available • 18.0 m pixels • Use of external JFETs possible • Reference signal channel

  29. HAWAII-2: Photolithographically Abut 4 CMOS Reticles to Produce Each 20482 ROIC Twelve 20482 ROICs per 8” Wafer 20482 Readout Provides Low Read Noise for Visible and MWIR

  30. HAWAII-2 Reference Signal

  31. Multiplexers: HAWAII-1R HAWAII-1RG HAWAII-2RG Abuttable 2K2K RIO developments Detector Materials: MBE HgCdTe on CdZnTe MBE HgCdTe on Si Cutoff wavelength Thinning Substrate removal AR coating New Developments

  32. NGST H-2RG & H-1R Packaging Critical Design Review May 8th, 2001 Rockwell Science Center Thousand Oaks, CA

  33. HAWAII - 2 1998 2048 x 2048 pixels 13 million FETs 0.8 µm CMOS 3-4 e- (8/8 Fowler) 10 e- (CDS) Guide mode & additional read/reset opt. HAWAII - 2RG True stitching 2048 x 2048 pixels 25 million FETs 0.25 µm CMOS HAWAII Heritage HAWAII - 1 HAWAII - 1R 2000 1994 Stitching (four independ. Quadrants) Reference pixels WFC 3 1024 x 1024 pixels 3.4 million FETs 0.8 µm CMOS 3-4 e- (8/8 Fowler) 10 e- (CDS) 1024 x 1024 pixels 3.4 million FETs 0.5 µm CMOS no noise data

  34. RSC Approach H A W A I I - 2 R G HgCdTe Astronomy Wide Area Infrared Imager with 2k2 Resolution, Reference pixels and Guide Mode • HgCdTe detector • substrate removed to achieve 0.6 µm sensitivity • Specifically designed multiplexer • highly flexible reset and readout options • optimized for low power and low glow operation • three-side close buttable • Two-chip imaging system: MUX + ASIC • convenient operation with small number of clocks/signals • lower power, less noise

  35. HAWAII-2RG: UMC 0.25µm CMOS • 3.3/2.5V Process on Epi Wafers • 1 Poly/4- or 5-Metal • 65/33Å Oxide • Low, Normal and High Threshold Voltage Options • MIM (Analog) Capacitor • 22 mm by 22 mm Stepper Field • Full Intra-Reticle Stitching • One Mask Set Comprising Modular Blocks to Photocompose Each CMOS Multiplexer on 200 mm Wafers

  36. NGST Multiplexer Overview • 2048 x 2048 resolution with 18 µm square pixels • True stitched design (electrical connections across stitching lines) • Close buttable die : - 2.5 mm mux overlap on top (pad) side - 1 mm mux overlap on each side  gap  2 mm) • 1, 4, or 32 output mode selectable • Slow mode (100 kHz) and fast mode (5 MHz with additional column buffers) selectable, both usable with internal and external buffers NGST

  37. 4 Output Mode Single Output Mode Fast scan direction selectable Fast scan direction individually selectable for each subblock default scan directions default scan directions Single output for all 2048 x 2048 pixels (guide mode always uses single output) Separate output for each subblock of 512 x 2048 pixels Slow scan direction selectable Slow scan direction selectable Output Options

  38. 32 Output Mode Separate output for each subblock of 64 x 2048 pixels Four different patterns for fast scan direction selectable Slow scan direction selectable default scan directions Output Options (2)

  39. Interleaved readout of full field and guide window FPA • Switching between full field and guide window is possible at any time •  any desired interleaved readout • pattern can be realized • Three examples for interleaved readout: Full field 1. Read guide window after reading part of the full field row 2. Read guide window after reading one full field row Guide window 3. Read guide window after reading two or more full field rows

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