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 (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 2K×2K NGST InSb
2009: HAWAII-4RG NSF grant (last week)

3. Materials for Infrared Detectors

4. Temperature and Wavelengths of High Performance Detector Materials
Si:As IBC
Si PIN
InGaAs
SWIR HgCdTe
LWIR HgCdTe
MWIR HgCdTe
InSb
Approximate detector temperatures for dark currents << 1 e-/sec

8. Collection of High-Performance CMOS Detectors
3D stacked CMOS wafer sandbox
HgCdTe 2K x 2K, 20 µm pixels
InSb 2K x 2K,
25 µm pixels
HgCdTe 4K x 4K mosaic, 18 µm pixels
HgCdTe 2K x 2K, 18 µm pixels
Monolithic CMOS 4K x 4K, 5 µm pixels

9. NICMOS PICNIC HAWAII HAWAII-2RG
Hawaii-2RG Heritage
All Successfully Developed on 1st Design Pass
NICMOS
PICNIC
HAWAII
1987
1990
1994
1994
1998
2000 -2 -1
4.2 million pixels
>13 million FETs
Expect CDS <10e-
16,384 pixels
70,000 FETs
CDS: <50e-
65,536 pixels
250,000 FETs
CDS: <30e-
-1R
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

10. Infrared Arrays
Diode Array
Multiplexer
Readout Electronics

11. 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 n p
Potential along this line shown
in graph above.
Cross section through the thickness of the CCD

13. 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

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

16. 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

17. 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

18. Double Correlated Sampling
Open Shutter
Close Shutter
kTC noise
0.5 V
Reset
Reset
Readout
Diode Bias Voltage
CDS Signal
Double Correlated Sampling
Readout
0 V
Time

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

20. Up-the-Ramp Sampling 0.5 V Diode Bias Voltage 0 V Time Reset
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

22. External JFETs
optimized

26. HAWAII-1 Rockwell Science Center
1024 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

27. HAWAII-1 Focal Plane Array

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

30. 3600 s
128 samp
T= 65K

31. Internal FETs

32. External JFETs
optimized

34. Fringing in PACE-1 material

35.
Residual Images in PACE-1 HAWAII-1 Arrays

37. Aladdin Raytheon 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

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

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

40. NIRI Aladdin Image of AFGL2591

41. HAWAII-2 Rockwell Science Center
2048 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

42. 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)

43. 20482 Readout Provides Low Read Noise for Visible and MWIR
HAWAII-2: Photolithographically Abut 4 CMOS Reticles to Produce Each ROIC
Twelve ROICs per 8” Wafer
20482 Readout Provides Low Read Noise for Visible and MWIR

45. HAWAII-2 Reference Signal

46. New Developments Multiplexers: Detector Materials: 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

47. 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

48. 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

49. NGST Multiplexer Overview
2048 x 2048 resolution with 18 µm square pixels
True stitched design (electrical connections across stitching lines)
Close buttable die : mm mux overlap on top (pad) side 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

50. 3-D Barrier to Prevent Glow from Reaching the Detector

51. Prototype 2×2 Mosaic for NGST

53. Ground-Based Camera Projects
2K*2K IR Arrays
IfA ULB
UKIRT WFC
CFHT WIRCAM
Gemini GSAOI
ESO VISTA
Keck KIRMOS

54. Detailed HAWAII-2RG Descriptions

56. 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

57. 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
Improvement: Doubling of the horizontal bus structure
Use bus A and bus B alternately
While one bus is connected to the output, use the other one for precharging the next column bus
Simulation of analog signal chain including double bus structure (next slide).

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

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

60. 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
Parallel (interleaved) readout of guide data and full field data
Guide window can be reset while the remaining pixels keep integrating (also allows individual reset of bright objects during long integrations)
Provides redundancy for science operation in case full field mode fails
Multiplexer Approach:
Use independent shift registers for normal mode and guide mode
Use reset scheme which allows individual pixel reset

61. Guide Mode Shift Register (Window Mode)
Additional MUX and AND - gate in each register cell
Decoder for selection of start and stop position
Stop Address
Start Address
Qpre
Start
&
n-1
MUX D Q
Row n FF n C
start decoder
Set start address to n+1
& n
Selection of row n+1
MUX D Q
Row n+1 FF C
stop decoder
n+1
&
n+1
MUX D Q
Selection of row n+2
Row n+2 FF C
n+2
Clk
Qout

62. 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

63. Reset Schemes

64. 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
SDATA
Bit 15
Bit 14
Bit 13
Bit 12
Bit 0

65. Major FPA Components Shortwave Focal Plane Array
Detector Mask
4 2Kx2K Sensor Chip Assemblies on Molybdenum Mounts
Flex Cables
Interface Plates
Mosaic Baseplate
Titanium Flexures
Interface Baseplate
GSE Handles
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

66. FPA Housings in NIRCam LW FPAs and Housings Module A Module B
SW FPAs and Housings
*OBA Struts and Brackets not shown