Impact of process variability on a frequency sensor used for · Impact of process variability on a...

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

© CEA. All rights reserved

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






Arrays of NEMS



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






Arrays of NEMS



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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Arrays of NEMS



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






Arrays of NEMS



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)






Arrays of NEMS



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

[email protected]


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