Challenges for MEMS: Going from MEMS to NEMS for lower cost and higher integration

Jean-Philippe POLIZZI CEA Leti, France

Jean-philippe.polizzi@cea.fr

iNemi Workshop May 10th 2012- Pittsburgh

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Leti at a Glance Figures 2010

Founded 1967 as part of CEA

Staff 1700

Budget 250 M€

Capex 40 M€

Industrial Partners 265

Joint Labs 30

Value Creation

1700 Patent portfolio (265 filed in 2010)

40% Under license

37 Startups created; 5 within the last 2 years Léti/Minatec at Grenoble (F)

200 and 300mm lines

8,000 m² clean rooms

Continuous operation

© CEA. All rights reserved

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30 years background in MEMS

80 85 90 95 00 05

year

10 15

Tra

nsfe

rs

Quartz

accelerometer

Weight sensor Hygrometer Pressure sensor

Pacemaker accelerometer

Geophone Accelerometer Inertial

platform

Ke

y d

ate

s

bulk technology

Surface micro-

machining

« Intra-CMOS »

demonstration

Waferscale

packaging

M&NEMS concept

Thin film

packaging

Above IC MEMS

demonstration

Comb drive

accelero patent

MEMS

technology

NEMS for

gas detection

Startup

19

97

Startup

20

11

LETI / Caltech Alliance

20

07

NanoSystems

Partnership

20

09

Common lab.

20

10

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Why going from MEMS to NEMS ?

Large volume markets

(Automotive/Consumer)

Strong pressure

on prices

Smaller devices

Consumer markets More integration The 10 axis sensor

•3 axis accelerometer

•3axis gyrometer

•3axis magnetometer

•1 P sensor

Mobile phones, gaming, tablets, e-books,

digital cameras, camcorders, HDD

protection, laptop, Personal media

Players,set-up boxes, GPS, sport

equipments…

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| 5

Down scaling MEMS…a solution ?

Typical sizes : ~10 nm – 100 nm (X, Y, Z)

Used material : silicon structured by microelectronic tools

500 µm

80 nm

10 µm

1 µm

Source LETI – MIMOSA project

Seismic mass is reduced impact on the sensitivity

Smaller capacitance and capacitance variation lower S/N ratio

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Miniaturization issues

Electromagnetic

detection

Me

an

P

erform

an

ces

Typical dimensions / Complexity

Inte

grati

on

level

few cm3

Macr

osco

pic

senso

r

gM 2

Piezoresistive or

electrostatic out of

plane detection

few mm3

1000

M

Bulk

mic

rom

ach

inin

g

ME

MS

sensor

“In

IC

”M

&N

EM

S s

en

so

r

Electrostatic,

MOS detection,...

< 0,01mm²

710.5

M

1mm²

Electrostatic in

plane detection

50000

M

Surf

ace m

icro

machin

ing

ME

MS

sensor

new design

new design

new design

?

Electromagnetic

detection

Me

an

P

erform

an

ces

Typical dimensions / Complexity

Inte

grati

on

level

few cm3

Macr

osco

pic

senso

r

gM 2

Piezoresistive or

electrostatic out of

plane detection

few mm3

1000

M

Bulk

mic

rom

ach

inin

g

ME

MS

sensor

“In

IC

”M

&N

EM

S s

en

so

r

Electrostatic,

MOS detection,...

< 0,01mm²

710.5

M

1mm²

Electrostatic in

plane detection

50000

M

Surf

ace m

icro

machin

ing

ME

MS

sensor

new design

new design

new design

?

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Compared to standard MEMS

• Area gain design (suitable for consumer applications)

• Or Sensitivity improvement (suitable for defense applications)

• Mix on a same device two different thicknesses – A thick layer for the inertial mass (MEMS)

– A thin layer for the gauge (NEMS)

Investigated Solutions

Gauge Mass Separate optimization

The M&NEMS concept

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Piezoresistive gage

Rotation axis

Seismic mass

Principle

VS

V0

R

V0

R

F = M.

F

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Piezoresistive gage

Rotation axis

Seismic mass

Principle

VS

V0

R

S = 50 mV/V full scale

( max= 100MPa)

R

RR

V0

R

R- R

R+ R

F = M.

F

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Stress magnification induced by design lever effect

m

In-plane measurement

Stress magnification induced by the Nano-gauge

Total Magnification : x3000

Top view

Cross section

view

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2 different thicknesses

Out-of-plane detection

Rotation axis

m

Out of plane measurement

Anchor

Seismic mass

gauge

Stress magnification induced by design lever effect & nano-gauge

Total Magnification : x1000

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250nm

250nm

M&NEMS accelerometer demonstrator

15µm

• Proof of concept design and fabrication of

accelerometer have been achieved

• Typical dimensions of the sensitive element

≈ 0.1mm² / axis

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3-axis M&NEMS accelerometer

Focus on the nano-gauge of the Z-axis

accelerometer

Focus on the nano-gauge of the X-axis

accelerometer

3-axis accelerometer

• Range: 19 g

• Seismic mass 2 ng (240 x 460 µm²)

• Measured Sensitivity

– SdR/R=1.75e-3 / g

– S = 3.5 10-4 V/g (no amplification)

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3D Gyrometer

Typical dimensions of sensitive element:

< 0.5mm² / axis

3D sensor on chip

1 sensitive element / axis (avoid cross

sensitivity)

Differential measurement (drift limitation)

Open-loop detection (no need matched

frequencies - process control is relaxed)

Rough vacuum required (no need for

getter)

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• Gyroscope measurement

– Noise: 0.02 /s/√Hz (limited by electronics)

– Quadratic bias of few 100 /s

= 50°/s

time drift

Measurement calibration

Allan deviation

3D Gyrometer

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3-axis Magnetometer

Working principle :

A permanent magnet layer is deposited on top a moving part

The magnet tends to align along the external magnetic field

The torque induced by the magnetic force is detected by the nano-gauge

Magnetic material = Coupled ferro / anti-ferro magnetic multilayer

Integration of permanent magnet Low power consumption compare to Hall effect or Lorentz force approach

Multi-range sensor (range set by MEMS design)

- R1

+ R2

B

+ R2≈0

+ R1 ≈0 (no lever effect)

Rgauge2 – Rgauge1 B

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Y

X

Z

500µm

3-axis magnetometer

Torsion springs

3-axis Magnetometer

Magnetic layer patterning Nano-gauge

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3-axis Magnetometer

• Magnetometer sensitivity measurement • Correlation between X and Y sensitivity on the

same chip : 99.8%

3-axis measurement

Co-integration Accelero + Magneto

Low power consumption

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M&NEMS platform

M&NEMS Technology

3D

Accelerometer

1st Validation

Q2 / 2010

3D

Gyrometer

1st Validation

Q3 / 2010

3D

Magnetometer

1st Validation

Q4 / 2010

Pressure

sensor

1st Validation

Q4 / 2011

Microphone

1st Validation

Q1 / 2012

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M&NEMS global interests

• 3D accelerometers on chip

• 3D gyroscope on chip

• 3D low consumption magnetometer on chip

• Same process for accelerometer, gyroscope,

magnetometer, pressure sensor and

microphone,…

• CMOS compatible fabrication

• 6 mask levels (without packaging)

• Concepts and technology protected by +12 patents

• Drastic miniaturization of inertial sensor – Target : 2x2 mm² for 3-axis gyro

– Target : 4x4 mm² for 9-axis sensor

• No parasitic sensitive

Can address sensors fusion

1 common analog electronics

for accelero, magneto,

microphone, pressure

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NEMS for chemical sensing

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How do resonant NEMS work ?

• NEMS resonator for ultra sensitive detection

– Frequency shift of the NEMS due added mass….

Mass

loading

Electromechanical features:

– High frequency f0, low mass m , low or strong stiffness k: MHz-GHz

– Low consumption, low energy dissipation: aW-fW)

– Very sensitive to very weak forces (fN-aN) / fields / charges (e-)

– Very sensitive to mass loading (ag – zg)

Ultra sensitive sensors

HF-resonators

Fast sensors

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Why using resonant NEMS ?

40

2l

M

f

m

f

eff

32010 lQ

Mm

DReff

Mass detection below ato gram

(10-18 g) in ambient air

Detection of few molecules

aggregates

~ a few zg (10-21g) to yg (10-24 g)

Sensitivity Resolution

δm

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Technological platform

• Development of generic and mastered process lines – 200 mm

– CMOS compatible / Microelectronic tools

Metal + Si devices

Out of plane displacement

Thermo mechanical actuation

Piezoresistive detection

Full Si devices

In plane motion

Electrostatic actuation

Piezoresistive detection

200 mm wafer of NEMS VLSI More than 3,5 million NEMS

SOI wafer – 160 nm Si top

400 nm BOX

248 nm and 193 nm DUV design

Beam width: 100 to 200 nm width

Integration density ~ 60 000 NEMS/mm²

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“crossbeam” NEMS

Cantilever beam : 3.2 x 0.3 µm2

PZR nanogauges : 400 x 80 nm2

Sensitivity 17 zg/Hz

S2

S1

E O

1 µm

released beam

lateral nanogauges

E. Mile et al, Nanotechnology, 2010

Brownian displacement detected 0.001Å /√Hz

(detection limit)

NEMS Crossbeam concept: provides a very high signal and high SNR

Mass detection below ato gram in ambient air ( m = 10-18 g)

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Application to Gaz analysis: system considerations

Gas Chromatography (GC) is a well-known separation method

Introduction

GC column provides selectivity by separating in time and space the gas mixture components NEMS detectors sequentially detect the elution peaks at the GC output

Both GC column and NEMS detectors can be miniaturized and fabricated with VLSI silicon micro- and nanofabrication techniques.

Injection of the gas mixture

Carrier gas flow

GC column

NEMS chip

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Multi-Gas measurements

Chromatogram measured by a crossbeam NEMS

NEMS is placed behind a 1m long silicon μGC

NEMS reach the same limit of detection, below the ppm level (in dynamic mode)

Calibration with commercial Thermal Conductivity Detector (40x30x20 cm3) with

an optimal column

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Two devices with different Functionalization layers gives added selectivities: 1) PCL: unselective absorbing polymer 2) DKAP: sensitive to phosphonate nerve agents

GC separation + functionalized NEMS array gives increased discrimination ability LoD ~ 200 ppt demonstrated NEMS detect peaks as fast as 8 ms

Application – Multi Gas Analyzer

Mass

loading

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Applications

• Monitoring of industrial processes

• NRBC (National security)

• Air quality monitoring

• Food quality & safety

• Pharma-screening

• Diagnostics (cancer lung …through biomarkers)

Gas card A new born…

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Conclusion

MEMS technologies are now mature with large market acceptance: MEMS are planned to generate a turnover of 16 billions $ in 2015.

NEMS are logically the next step to bring Higher integration

Lower costs

Enhanced performances

New functionalities

But

NEMS cannot simply be scaled down version of MEMS

New concepts are needed Approach differs depending on sensor type

Combination of micron-sized proof mass with nano gauge detection presents many advantages for physical sensors

Nano scale resonators are well suited to extremely small mass or force detection

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Thank you for your attention