Post on 19-Mar-2020
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CMOS THz Detectors for CMOS THz Detectors for ImagingImaging
1CEA-LETI, MINATEC, Grenoble, FRANCE
2University of Montpellier, FRANCE
F. Schuster1,2, D. Coquillat2, H. Videlier2, M.Sakowicz2, JP. Rostaing1, B. Dupont1, B. Giffard1,
W. Knap2
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Outline
I. Introduction and Background
II. Detector Implementation
III. Detector Characterization
IV. THz Transmission Imaging
V. Summary
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I. Introduction and Background
• THz radiation:– THz band: 300GHz – 3THz, λ0 = 1mm -100µm– Unique physical properties– Applications
• Non-destructive testing/ quality control• Security imaging• Wireless communications
106 108 1010 1012 1014 1016 1018 f [Hz]
radio & µ waves IR UV X-ray
THz
VIS
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I. Introduction and Background
• FETs as THz detectors– Rectification of THz radiation
• Radiation coupling: antenna or grating• Theories: Dyakonov-Shur plasma wave theory;
distributed resistive self-mixing
Vgs
Ua
∆U
• Vgs: gate bias• Ua: irradiation
induced ac voltage• ∆U: photoresponse
GDS
THz , modulated
: fmod
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I. Introduction and Background
• Si CMOS THz detectors– First demonstration in 2004, Knap group – Focal plane arrays in 2008, Pfeiffer & Roskos groups– This work: single detectors and arrays for 0.3-1.05 THz
[1] Tauk et al. APL, 2006
650GHz Focal Plane Array [2]Single FETS at 700GHz [1]
[2] Öjefors et al. ESSCIRC, 2010
0 0.2 0.4 0.6 Vgs,V
200
100
0Res
pons
ivity
, V/W Lg=300nm
Lg=200nm
Lg=130nm
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II. Detector Implementation• Test chip micrograph
– 0.13µm CMOS– Bulk Si substrate
– 210µm pixel pitch– Pixel variants
• FET, antenna• amplifiers
– 3x4 pixel imager prototype: amps + multiplexing
2.2 mm
2.2
mm
210 µm 190 µm
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II. Detector Implementation• Pixel architecture
Bow tieantenna
Vout
– Bow tie antenna in metal back end
– Rectifying nMOSFET, variations:L=130nm – 300nm, W=250nm – 10µm
– Optional: in pixel baseband amplifier, G=31dB
FET ∆U
optional
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II. Detector Implementation• Amplifier schematic
– pMOSFETs– MIM capacitor for
feed back– G=31dB, 2MHz BW– Low consumption
97µW@1.2V– Low input noise:
16nV/Hz0.5@30kHz
∆U Vout
Vdd
bias
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II. Detector Implementation• Pixel micrograph
210 µm
210
µm
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II. Detector Implementation• 3x4 pixel imager with multiplexing
Shift Register
Clk 1Rst 1
Clk 2Rst 2
Shi
ft R
egis
terPixel
Array Output
• Pixel multiplexing with:– 2 shift registers– 2 clock, 2 reset
signals
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II. Detector Implementation• Pixel multiplexing
– Shift register with D-flip-flops
ClkRst
D QSD
C
D QSD
C
D Q
CDC
D Q
CDC
D Q
CDC
D Q
CDC
D Q
CDC
D Q
CDC
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III. Detector Characterization • Set-up
Lock-In
THzSource
Test Chip on Translation Stage
ParabolicMirror Plane
Mirror
Ref.Chopper
X,Y
Vout
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III. Detector Characterization • Set-up
THzSource
Imager
ParabolicMirrors
Chopper
Translation Stage
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III. Detector Characterization • Set-up: beam power measurement
– THz power meter, Thomas Keating– Large aperture: 3 x 4cm
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III. Detector Characterization • Results 1/5: pixels without amplifier
Raster scan image of source beam at 300GHz
Used for responsivity calculation
Vgs=0.1V
Pbeam=0.8mW Adet = (pixel pitch)2
detAP
dydxU
Rbeam
image
v ⋅
∆=∫∫
Vgs=0.1V
Pbeam=2mW
∆Umax = 19mV
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III. Detector Characterization • Results 2/5: pixels without amplifier
Responsivity & NEP at 300GHz
0.0 0.2 0.4 0.60
1k
2k
3k
4k
5k
0.0 0.2 0.4 0.6
10p
100p
1n
10n
Vgs
(V)
R
v (V
/W)
C14, 125µm C5, 125µm C14, 370µm x 2 C15, 125µm x 10
substrate
Vgs
(V)
C14, 125µm C5, 125µm C14, 370µm / 2 C15, 125µm / 10
N
EP
(W
/Hz0.
5 )
vds RRTkNEP /4=
NEPmin=8 pW/Hz0.5
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III. Detector Characterization • Results 3/5: pixel C14 without amplifier
Responsivity from 270- 1050 GHz
300 400 500 600 700 800 900100010
100
1k
10k
Rv (
V/W
)
Frequency (GHz)
1 2 3 4 51
2
3
4
5
C14, 125um
Vgs
=0.2V
1050GHz, 180µW Beam
∆∆∆∆U (V)Y p
ositi
on (m
m)
X position (mm)
0.017µ34µ51µ68µ
34µ
Rv,max =5kV/W
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III. Detector Characterization • Results 4/5: pixel with amplifier,
Raster scan image of source beam at 300GHz
X position (mm)
Y p
ositi
on (
mm
)
Vout (V)
Vgs=0.1V
Pbeam=0.8mW
Vout,max = 165mV
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III. Detector Characterization • Results 5/5: pixel with amplifier
Detector signal & responsivity at 300GHz
Rv,max = 90kV/W
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IV. THz Imaging• Transmission imaging of objects
Object on Translation Stage
Lock-In
THzSource
Test Chip on Translation Stage
ParabolicMirror Plane
Mirror
Ref.Chopper
X,Y
Vout
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IV. THz Imaging, 300GHz• chocolate with metal object inside
→ application: food control
Metal wire
225x300 scanned points
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IV. THz Imaging, 300GHz• tree leaves → agriculture: water saving
225x600 scanned points
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V. Summary
• Demonstration of sensitive THz detectors & 3x4 pixel array in CMOS– nMOSFET THz detectors– Integrated broad band bow tie antennas
– Pixel consumption <100µW– High responsivities: 90kV/W @300GHz,
1.8kV/W @1.05THz
– Low NEP: <10pW/Hz0.5 @300GHz– High quality THz images @300GHz
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Recent Publications
[1] F. Schuster, A. Dupret, W. Knap et al. A Broadband THz Imager in a Low-cost CMOS Technology. International Solid-State Circuits Conference, 2011.
[2] F. Schuster, D. Coquillat, W. Knap et al.Broadband terahertz imaging with highly sensitive silicon CMOS detectors. Opt. Expr.vol. 19, pp. 7827–7832, 2011.
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Acknowledgements
• Partial funding from:– French Ministry of Defense– STMicroelectronics through Nano
2012 Project
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Thank you!Questions?