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Impact of process variability on a frequency‐Impact of process variability on a frequency‐addressed NEMS array sensor used for gravimetric detectiongravimetric detectionMARTIN Olivier 1, COLINET Eric*, SAGE Eric, DUPRE Cécilia, VILLARD Patrick, HENTZ Sébastien, DURAFFOURG Laurent and, ,ERNST Thomas
CEA‐Leti, Minatec Campus, 17 rue des Martyrs, 38054 Grenoble Cedex 9, France* APIX Technology, Grenoble, France
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APIX Technology, Grenoble, France1 [email protected]
Contents Introduction
State of the art & applications for NEMS used as gas sensors
The « Crossbeam » NEMS Presentation & fabrication
G i t i d t tiGravimetric detection
Readout of such NEMS by frequency tracking
Arrays of NEMS
Impacts of the process variation
Measurements and resultsOpen loop
Optical control
Conclusion
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Conclusion
Contents Introduction
State of the art & applications for NEMS used as gas sensors
The « Crossbeam » NEMS Presentation & fabrication
G i t i d t tiGravimetric detection
Readout of such NEMS by frequency tracking
Arrays of NEMS
Impacts of the process variation
Measurements and resultsOpen loop
Optical control
Conclusion
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Conclusion
NEMS resonators CMOS
NEMSNEMS
[1] [4]
[1] Capacitive A/D, metal, BE –University of Barcelona (UAB)
[2] Capacitive A/D, Polysilicon, ‐ UAB
[2]
[5]
[3] Capacitive A / piezoresistive D – Koumela et al. 2011 (Eurosensors)
[4] Capacitive A/D, Si+PolySi ‐ Colinet et al. 2010 (Frequency Control Symposium)
[5] Capacitive A/D ‐ Arcamone et al. 2008 (Journal of Physics: Conf. Ser. 100)
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[3] [6] [6] Piezoelectric ‐Mo Li et al. 2008 (Nature Nanotechnology)
Applications[8]
Air qualityq y
Industrial process monitoringPetrochemical industry, …
Volatile organic compounds (VOC) identificationTEOX (Toluene, Ethylbenzene, Octane, Xylene)
Securitychemical warfare agents detection
Promising biomedical applicationsPromising biomedical applications Early diagnosis of illness (lung cancer, …)
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[8] Max‐One gas analyzer (GC/NEMS sensor), APIX Technology, http://apixtechnology.com
Contents Introduction
State of the art & applications for NEMS used as gas sensors
The « Crossbeam » NEMS Presentation & fabrication
G i t i d t tiGravimetric detection
Readout of such NEMS by frequency tracking
Arrays of NEMS
Impacts of the process variation
Measurements and resultsOpen loop
Optical control
Conclusion
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Conclusion
The « Crossbeam » ‐ NEMS resonator
In‐plane motion of the beam
Differential electrostatic actuation
Piezoresistive detection by nanowire gauges
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Process of fabrication (LETI)
HF
Si TOPAlSi 1
BOX (SiO )
AlSi 2
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BULK (Si)
BOX (SiO2)
The « Crossbeam » as a mass sensorThe « Crossbeam » as a mass sensor
Equation of the beam flexion :q
Effect of mass loading :
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Frequency tracking readout (FLL)Frequency tracking readout (FLL)Principle :
Ph hif f 90° @ fPhase shift of 90° @ resonance frequency
Input/Output phase shift comparison
Controller feeds a VCO which actuates @ the new resonance frequency
DIFFERENTIALACTUATION
LPF
∆Φω
ω
Lock in detectionin
refH∞Phase
Splitter
0°
180°
‐ 90°
VCO @
ω
ω
PLLDC BIAS
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VCO @ ω PLL
Parallel NEMS array integration schemeParallel NEMS array integration scheme
Collectively addressedCollectively addressed resonator
Same resonance frequency
Better SNR proportional to
Global Q depends on process fluctuation
Same load needed on each NEMS
Frequency addressed resonatorEach NEMS is readed independantlyaround its resonance frequency
Limits : frequency bandwidth / Q
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Contents Introduction
State of the art & applications for NEMS used as gas sensors
The « Crossbeam » NEMS Presentation & fabrication
G i t i d t tiGravimetric detection
Readout of such NEMS by frequency tracking
Arrays of NEMS
Impacts of the process variation
Measurements and resultsOpen loop
Optical control
Conclusion
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Conclusion
Impact of the variations (I)Impact of the variations (I)
Dependance of the Resonance frequency:geometrical parameters
E : Young’s Modulus of elasticity (169 GPa)
th d it f th ili (2330 k / 3)ρ : the density of the silicon (2330 kg/m3)
S : the cross‐section of the lever beam
k1=2.1178/Lb : the wave vector (anchorage)
I : the bending moment of inertiaWith Lb > 15~20.Wb
I : the bending moment of inertia
Wb is 10 times more impacting than Lb
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impacting than Lb
Impact of the variations (II)Impact of the variations (II)
Resonance frequency shift : Bandwidth of the NEMS: *For NEMS resonating at 20 MHz, 40
MHz and 60 MHz
With a 10 nm width fluctuation error
ΔΩ1=Ω1/Q with Q ≈ 100*
500 kHz for a 50‐MHz resonance frequency NEMSDownshift of 1.21 MHz, 2.46 MHz
and 3.63 MHz respectively
resonance frequency NEMS
A 6% variation on the widthleads to a 6% downshift of the resonance frequencyresonance frequency
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* In air
Contents Introduction
State of the art & applications for NEMS used as gas sensors
The « Crossbeam » NEMS Presentation & fabrication
G i t i d t tiGravimetric detection
Readout of such NEMS by frequency tracking
Arrays of NEMS
Impacts of the process variation
Measurements and resultsOpen loop
Optical control
Conclusion
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Conclusion
Measurement setup (I) – Open LoopMeasurement setup (I) Open Loop
First bench:Frequency control
Open loop
L k i A lifi SR 830Image multifrequences
Δω Lock in detectioninPhase
Splitter
0°
Lock‐in Amplifier : SR 830
Sources : Agilent 81160A (Double)
2468
nitu
de (m
V) LPF
ω‐Δω
refSplitter180°
Δω
3.5 4 4.5 5x 10
7
0
f(MHz)
Mag
RF Source @ ω
Ref @ Δω
ω
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[9] E. Sage et al. ‐ Transducers 2013
Measurement (I) ‐ ResultsMeasurement (I) Results1.1
y
Nominal frequencies at Wb = 270 nm
Nominal frequencies at Wb
+ 5nm
1.05
Freq
uenc
y qb
Nominal frequencies at Wb +10 nm
Measured frequencies
1
rmal
ized
F
36 40 44 48 52
0.95
Nominal Frequency (MHz)
Nor
Nominal Frequency (MHz)
Dispersion on the width below 10 nm
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Dispersion on the width below 10 nm
Measurement setup (II) – OpticalMeasurement setup (II) Optical
YSecond bench:Z
Y
Y
X
Tsi
Wb
g
Lb
Lg
Second bench:Morphology of each NEMS characterized by SEM (Scanning Electron Microscopy) Tsi g
Wga
Electron Microscopy)
Characterization of:L W
8
10
12
14
occu
renc
e
Target = 270 nm
µ = 268.43 nm
σ = 6.55 nm
Lb, Wb, g
Exemple of Wb for a 40 MHz NEMS:
0
2
4
6N
umbe
r of oσΩ1 = 1.83 MHz (cf Bench 1)
σWbshould be 7 nm (Bench 1)
Results : 6.55 nm
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240 250 260 270 280 2900
Measured dimension (nm)
Contents Introduction
State of the art & applications for NEMS used as gas sensors
The « Crossbeam » NEMS Presentation & fabrication
G i t i d t tiGravimetric detection
Readout of such NEMS by frequency tracking
Arrays of NEMS
Impacts of the process variation
Measurements and resultsOpen loop
Optical control
Conclusion
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Conclusion
ConclusionConclusion
Process variations impact on a new NEMS devicep
was studied
Most impacting parameters are indentifiedMost impacting parameters are indentified
Toward VLSI sensors with a better capture area
Design of frequency‐addressed NEMS arraysDesign of frequency addressed NEMS arraysWithout overlap of frequencies
More robust
With a maximum of density
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Thank you forThank you for your attentionyour attention
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