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

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

• Klaus W. Hodapp
• Institute for Astronomy
• University of Hawaii

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Historic Milestones

• 1800 Infrared radiation discovered (Herschel
  with his thermometers)
• 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 2K2K NGST InSb
• 2009 HAWAII-4RG NSF grant (last week)

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Materials for Infrared Detectors
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Temperature and Wavelengths ofHigh Performance
Detector Materials
Approximate detector temperatures for dark
currents ltlt 1 e-/sec
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Collection of High-Performance CMOS Detectors
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Hawaii-2RG Heritage
All Successfully Developed on 1st Design Pass
NICMOS
PICNIC
HAWAII
1987
1994
1990
1994
1998
2000
-2
-1
4.2 million pixels gt13 million FETs Expect CDS
lt10e-
-1R
65,536 pixels 250,000 FETs CDS lt30e-
16,384 pixels 70,000 FETs CDS lt50e-
65,536 pixels 250,000 FETs CDS lt20e-
1.05 million pixels gt3.4 million FETs CDS lt10e-
CDS ltTBD 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
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• Infrared Arrays
• Diode Array
• Multiplexer
• Readout Electronics

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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
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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

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Open Shutter
Close Shutter
0.5 V
Reset
Reset
Diode Bias Voltage
kTC Noise
Reset-Read Sampling
Readout
0 V
Time
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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 v kTC
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Example Capacitance 50 fF, T37 K k 1.38 e-23
J/K Q_n v kTC Q_n 5 e-18 C With q_e 1.6
e-19 C Q_n 32 electrons rms
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Open Shutter
Close Shutter
kTC noise
0.5 V
Reset
Reset
Readout
Diode Bias Voltage
CDS Signal
Double Correlated Sampling
Readout
0 V
Time
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Open Shutter
Close Shutter
kTC noise
0.5 V
Reset
Reset
Readout
Diode Bias Voltage
MCS Signal
Fowler (multi) Sampling
Readout
0 V
Time
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Open Shutter
Close Shutter
kTC noise
0.5 V
Reset
Reset
Diode Bias Voltage
MCS Signal
Up-the-ramp Readout
Up-the-Ramp Sampling
0 V
Time
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External JFETs optimized
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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

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HAWAII-1 Focal Plane Array
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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

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3600 s 128 samp T 65K
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Internal FETs
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External JFETs optimized
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Fringing in PACE-1 material
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1997
1998 Residual Images in PACE-1
HAWAII-1 Arrays
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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

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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

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Aladdin frame taken with SPEX (J. Rayner)
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NIRI Aladdin Image of AFGL2591
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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

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Continuing to Aggressively Use CMOS

• 5 Designs in 0.25µm
• 3.3/1.8V 0.18µm CMOS underway for ProCam-2
• Also migrating to 0.13µm on newest programs to
  boost performance via Cu and low-k interlayer
  dielectrics

After Isaac (1999)
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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
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HAWAII-2 Reference Signal
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New Developments

• 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

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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

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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

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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
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3-D Barrier to Prevent Glow from Reaching the
Detector
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Prototype 22 Mosaic for NGST
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Ground-Based Camera Projects 2K2K IR Arrays

• IfA ULB
• UKIRT WFC
• CFHT WIRCAM
• Gemini GSAOI
• ESO VISTA
• Keck KIRMOS

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Detailed HAWAII-2RG Descriptions
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Block Diagram

• 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

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Doubled Bus Structure

• Old HAWAII-1/2 architecture
• Discharge of the column bus results in a
  significant drop of the output signal when
  switching from one pixel to the next.
  ? longer settling time
  
  ? higher power
  consumption due to the charging of the external
  load

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Output Options
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Output Options (2)
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Support of Full Field and Guide Mode with Low
Risk

• Guide mode (tracking of a guide star) is required
  to keep the orientation of the telescope constant
  with respect to the observed object.
• Guide mode requires the readout of a small
  subarray (variable size, arbitrarily located) at
  a high frame rate
• It is highly desirable not to lose the rest of
  the guide FPA for full field integration

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Guide Mode Shift Register (Window Mode)
Stop Address
Start Address

• Additional MUX and AND - gate in each register
  cell
• Decoder for selection of start and stop position

Qpre
Start

n-1
Q
D
MUX
Row n
FF
C
n
start decoder

• Set start address to n1

n
Selection of row n1
D
Q
MUX
FF
Row n1
C
stop decoder
n1

n1
Selection of row n2
Q
D
MUX
FF
Row n2
C
n2
Qout
Clk
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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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Reset Schemes
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Serial Interface

• Three-wire serial interface allows to program the
  multiplexer
• choose start/stop addresses for guide window
• select different operation and test modes
• Interface lines can be shared with shift register
  clock lines

CS
SCLK
Bit 12
SDATA
Bit 15
Bit 14
Bit 13
Bit 0
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Major FPA Components
Items in Blue are provided by Arizona Sensor
chip assemblies are provided by RSC. Longwave
architecture similar but simpler (only one SCA).
Shortwave Focal Plane Array
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FPA Housings in NIRCam
LW FPAs and Housings
Module A
Module B
SW FPAs and Housings
OBA Struts and Brackets not shown
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