1

PRESSURE / STRESS SENSORS

Patrick PONS, Philippe MENINI

5 phD, 1 post doc1 RECIF Engineer

November 2006

INTRODUCTION

Objectives

• Development of silicon membrane pressure sensors for specific applications (automobile, aeronautic, medical)

• Pressure range• Temperature range• Sensitivity / accuracy

• Multisensors integration

• Integration of communication circuits / wireless sensor

• Development of new transduction type

Developments achieved : 1980 2005

• Capacitive transduction : silicon / pyrex

• Piezoresistive transduction : mono and polycristalline silicon gauges

Transduction Probre integration Packaging

Design Technology

3

CAPACITIVE SENSORS

Pyrex

Silicium H H1

H2

L

D

• 20 m < H < H1• 300 m < H1 < 500 m• 0.5 mm < H2 < 1.5 mm• 1.5 m < D < 3 m• 2 mm < L < 4 mm• Chip area : 5 x 5 mm2 to 7 x 7 mm2

Functional characteristicsFunctional characteristics • Pressure range : 0.1 to 100 bars • Nominal capacitance : 10 to 100 pF • Full scale response (FS) : 5 to 15 % • Nonlinearity : ± 1 to ± 3 % FS • TCO : < 100 ppm / °C • TCS : 100 to 2000 ppm / °C • Temperature range : - 40 to 180 °C

Pressure sensor for automobile tire : 0 / 6 bars, - 40 / 120 °C

CAPACITIVE SENSORS – Two linear range Two linear range

0 2 4 6 8 10 12 14 16 1820

30

40

50

60

70

80

90

100

110

Ca

pa

cita

nce

(p

F)

Pressure (bar)

Pressure (bar)

Ca

pa

cita

nce

(p

F)

4,0 4,5 5,0 5,5 6,0 6,5 7,0 7,5

36

37

38

39

40

41

42

43

44

45

Sp = 2.3 pF/barNL = ± 1.7% FS

0,0 0,1 0,2 0,3 0,4 0,5 0,6 0,7 0,8 0,9 1,0

21,6

21,8

22,0

22,2

22,4

22,6

22,8

23,0

23,2

23,4

23,6

Sp = 2 pF/barNL = ± 1.2% FS

Ca

pa

cita

nce

(p

F)

Pressure (bar)

Mohamad Al Bahri(Oct 2000 / May 2005)

Fouad KerrourMay 2006 / Oct 2007

PhD Univ. Constantine

5

CAPACITIVE SENSORS - Thermal drift in circular cavityThermal drift in circular cavity

-30 0 30 60 90 120 15080

90

100

110

120

130

140

150

160

170

180

190

200

210

220

1234567

ABCDEFG

abcdefg

Electrode thickness = 0,1µm (Al)

TC

[C(0

,T)]

(

pp

m/°

C)

Température (°C)

Electrode thickness = 0,8 µm (Al)

Offset : Offset : α(Pyrex-Alu)

Top view

Bottom view

Sensitivity : Sensitivity : α(Pyrex-Si)

-20 0 20 40 60 80 100 120 140 160

-2600-2400-2200-2000-1800-1600-1400-1200-1000-800-600-400-200

0200400600

h

qv00

Tv

Série P5 ( em= 0,1µm )

TC[Sv(T)] (ppm/°C)

Température (°C)

Membrane thickness (h) : 26 µm to 45 µm

Resonant frequency : Resonant frequency : α(Pyrex-Si)

-20 0 20 40 60 80 100 120 140 160-100

0100200300400500600700800900

1000110012001300140015001600170018001900

1

2

3

4

5

6

7

A

B

C

D

E

F

G

a

b

c

d

e

f

g

h

Tf

qf 00

Série P5,P2, et P1 (Circulaire)

TC[fr(0,T)] (ppm/°C)

Température (°C)

Membrane thickness (h) : 26 µm to 45 µm

-30 0 30 60 90 120 150

-1200-1100-1000-900-800-700-600-500-400-300-200-100

0100200300

TC[Sp]Sv=TC[Sv] -2TC[Co]

TC[Sp]fr=2TC[Co] -2TC[fr]

TC

[Sp(

T)]

(p

pm/°

C)

Temperature (°C)

Mohamad Al Bahri(Oct 2000 / May 2005)

Fouad KerrourMay 2006 / Oct 2007

PhD Univ. Constantine

6

PIEZORESISTIVE SENSORS

10 m < H < qq 100 mqq 100 µm < L < qq mm

Chip area : 1 mm2 to several 10 mm2

R3

R2 R1

R4

VaVs

Wheatstone bridge

⎟⎟

⎠

⎞

⎜⎜

⎝

⎛−−+≈

3

3

1

1

4

4

2

2

4

1

R

R

R

R

R

R

R

R

V

V

a

sΔΔΔΔΔ

HSilicon

L

Stress gauges

Functionnal characteristicsFunctionnal characteristics - Pressure range : 0.1 to 100 bars - Bridge resistance : 1 to 3 k - Full scale response (FS) : 0.5 to 3 % Va - Nonlinearity : < ± 1 % FS - Nominal Offset : < 1 % Va - TCO : 5 to 100 ppm / °C - TCS : 1000 to 2500 ppm / °C - Temperature range : - 40 to 125 °C (400°C)

7

High temperature sensor for aeronautic applicationHigh temperature sensor for aeronautic application - SOI wafer - Temperature range : - 40 à 400 °C - Pressure range : 0.1 à 10 bars - Offset : 0.1 % de la tension d’alimentation - Sensitivity : 2 mV/V/bar - TCS : 1200 ppm / °C

2001 : Industrial transfer (Auxitrol)Industrial transfer (Auxitrol)

Miniature sensor for medicalMiniature sensor for medical application (intracranial)application (intracranial) - Temperature range : 20 à 45 °C - Pressure range : - 80 à 400 mbars - Offset : 0.1 % de la tension d’alimentation - Sensitivity : 5 µV/V/mbar - TCO : 0.2 mbar / °C

Validation phase (HEMODIA)

PIEZORESISTIVE SENSORS

1.5 mm

Mohamad Al BahriPost doc (Dec 2005 – Dec 2006)

EFFECT OF GAUGE LENGHT (L) AND POSITION ON PIEZORESISTIVE SENSOR SENSITIVITY

180 190 200 210170160150

L = 100

L = 2

L = 80L = 40

L = 60

Membrane position

R/R (%)

X axis (µm)

EFFECT OF NON IDEAL CLAMPED MEMBRANE ON PIEZORESISTIVE SENSOR

Silicon die Silicon membrane

Clamped die Clamped membrane

x

y

Rotation at anchorageClamped die

Clamped membrane

MPa

x - y

X axis (µm)

EFFECT OF NON IDEAL CLAMPED SILICON DIE ON PIEZORESISTIVE SENSOR

Silicone joint

500 µm

Silicon die

Sensor deformation under pressure

Silicone joint deformation No significant effects on sensor sensitivity

Objectives- Sensor miniaturization : local measurement, reduce probe traumatism

Die width < 500µm Membrane thickness 1µm (SOI) Implanted gauge thickness 0.1µm, Gauge width < 1µm

- In situ-autocalibration : eliminate external calibration (reduce infection risks) SOI / Pyrex technology Integration of electrostatic pressure generator Integration of high stability voltage source (INSERM)

- Sensor integration into the probe (stress assembly, bio-compatibility)

- Telemetric output (INSERM) : eliminate external cable

MINIATURE TELEMETRIC PIEZORESISTIVE PESSURE SENSOR WITH IN SITU SELF-CALIBRATION

Framework- ANR project (Dec 06 / Dec 09)

Partners : HEMODIA, INSERM, Toulouse Hospital, Epsilon - Regional project (submitted)- Joint Laboratory with HEMODIA (submitted)

Michal OlszackiOct 2005 / Nov 2008

PhD Lodtz Univ. grant

Cesary MajOct 2005 / Nov 2008

PhD Lodtz Univ grant.

Mohamad Al BahriDec 2006 / Dec 2009

Post doc ANR

Pierre YameogoJanv 2007 / Dec 2009)

PhD CIFRE HEMODIA

Applications : Intracranial and Intravascular pressure sensor

WIRELESS PASSIVE PRESSURE SENSOR

S21

(dB

)

RF transduction : resonance frequency modification of planar resonator

Example of 30GHz resonator Others frequency possible (resonator design) Frequency : Size Very high sensitivity to pressure

P

Mehdi JatlaouiOct 2005 / Dec 2008PhD Tunisia grant

MINC collaboration (Hervé Aubert)

Aerospace Valley project (submitted) : Sept 07 / Sept 10

COLLECTIVE PACKAGING FOR PRESSURE SENSOR

Framework : Auxitrol collaboration (Oct 06 / Oct 09) Jean François Le NéalNov 2006 / Oct 2009

PhD CIFRE AUXITROL Objectives :

- Oil suppression (increase temperature range, reduce drift)- Collective process : reduce costs

Studies - Cap assembly

Pyrex, silicon Anodic bonding, thermocompression, eutectic bonding

- Surface micromaching Polymer sacrificial layers Thick dielectric cap layers

SUPERCRITICAL CO2 FOR MEMS APPLICATION Framework :

- Regional project (Oct 06 / Oct 08)- RECIF collaboration- Joint Laboratory with RECIF ?

Laurent Rabbia – Vincent PerrutRECIF Engineer

Objectives : Use of supercritical CO2 properties (low interfacial tension)- Wet etching of polymer sacrificial layer and C02 drying in the same chamber- Complete micromachining under supercritical state- Surface conditionning with Self Assembled Monolayer into CO2

Applications- MEMS release- Packaging release- Microfluidics

??????Oct 2007 / Sept 2010

PhD CIFRE RECIF ?

15

POSSIBLE NEW PROJECTS

Integration of pressure sensors with chemical sensors (FET gauge)

Stress sensors for buried pipes (Veolia)

Stress sensors for satellite (Astrium / Regional project submitted)- Wireless stress network- MINC collaboration