Albert (“Al”) P. Pisano, Ph. D.

Chair, Department of Mechanical EngineeringProfessor of Mechanical Engineering

FANUC Professor of Mechanical SystemsProfessor of Electrical Engineering and Computer Sciences

Director, Berkeley Sensor & Actuator Center(510) 643-7013

appisano@me.berkeley.eduhttp://www.me.berkeley.edu/faculty/Pisano

The MINOTAUR Project

MIcro and NanO Technologies for AUtomotive Research

Slide 2

Reason for the MINOTAUR Project

Phase 1 Automotive Sensors (completed)New Sensors for Enhanced Driver Information

Phase 2 Automotive Sensors (completed)Sensor Communication with Control Computers

Phase 3 Automotive Sensors (entering)Software Programmable Automotive Experience

The New Paradigm for Automotive Sensors

Slide 3

Reason for the MINOTAUR Project

Reduced Cost & Ease of ManufactureIntroduction of Micro and Nano Technologies

Higher PerformanceEnhanced Sensitivity and Bandwidth

Greater RobustnessThermal, Shock and Chemical Resistance

New Sensor ModesDirect Measurement of DataReduced Use of Computer Models to Guess

New Requirements for Automotive Sensors

Slide 4

Review of Existing Sensors

Cylinder PressureCombustion TemperatureCombustion Flame SpeedEngine Output TorqueWheel Forces on ChassisRoad Forces on WheelsSuspension Forces and Torques

Existing Sensors Do Not Directly Measure Engineering Phemonena

Slide 5

Review of Existing Sensors

Slide 6

Advanced Safety Vehicle (ASV)

Slide 7

Direct Measurement of Forces

MEMS Strain Gauge

COTS RF Transceiver

MEMS Sensor on Wheel Communicates via RF to Transcieveron Chassis

MEMS Strain Gauge

MEMS Sensor on Shock Tower Measures Vertical Forces On Chassis for DSC Application

Slide 8

Projects Overview

SiC TAPS Sensors for

Harsh Environments

NanowireArray Gas Sensors

MEMS REPS Smart

Plate

MINOTAUR Research Projects

MEMS Strain

Sensors

Integration of NEMS Integration of NEMS and MEMS and MEMS

by Localized Growth of by Localized Growth of NanowiresNanowires

Slide 9

steel substrate

sensorFoil gauges are limited in application and size:

Sensitivity limits length to ~1.5 mmRequire complicated & time consuming bonding

MEMS gauges offer solution:Inherently smallCan incorporate bonding structures into deviceIntegration with control, and data analysis CMOS also a possibility.

Example: Auto BearingRoller / Race interaction creates strain field ~100 μm wideThis field dictates fatigue life of the bearing and relates directly to the force on the bearing, allowing for improvements in traction control applications.Require 0.1μЄ resolution at 10kHz bandwidth

~100 μm

~100 μm~500 μstrain

MEMS resonant strain sensor

MEMS Strain Sensors

Slide 10

Sensor Resolution Vs. Bandwidth

Bandwidth [ Hz ]

με [rms]

100 101 102 10310-4

10-3

10-2

10-1

TargetTargetTargetTarget

104

216.8

217

217.2

217.4

217.6

217.8

218

218.2

0 5 10 15 20 25

Measured = 39 Hz/με Calculated = 36 Hz/με

Applied strain [ microstrain,με ]

SWO

frequ

ency

[ kHz

]

216.8

217

217.2

217.4

217.6

217.8

218

218.2

0 5 10 15 20 25

Measured = 39 Hz/με Calculated = 36 Hz/με

Applied strain [ microstrain,με ]

SWO

frequ

ency

[ kHz

]

Measured Strain Sensitivity

On-chip StrainActuator

MEMS Die Photo

AnchorTines

Anchor

MEMS DiETF

Slide 11

Induction bonding is a fast, clean, and inexpensive heating process.Generating an alternating magnetic field induces eddy currents in the metal.Eddy currents cause localized heat generation from Joule heating.Heat profile can be analyzed and controlled to prevent damage to the heat treatment of the steel.

Silicon-to-Steel Induction BondingSilicon-to-Steel Induction Bonding

Slide 12

Pb/Sn layer is then reflownusing infrared heating.Silicon test structures with Ti/Cu layer are cleaned.Test specimen are then exposed to infrared heating for a short period of time (30-60 seconds).The result: silicon bonded to steel!

Si Test Die Spring Steel Test Structure

CopperTitanium

Pb/SnNitride

Steel parallel with bonded silicon under high strain

Silicon test chips bonded to steel

Silicon-to-Steel IR BondingSilicon-to-Steel IR Bonding

Slide 13

P3: Amorphous SiC,

P1: Epitaxial 6H-SiC, (SiC Electronics)

P2: Poly 3C-SiC, (SiC MEMS structures)

6H-SiC Substrate

Silicon Carbide TAPS Sensors

Extreme Environment Sensor600 °C temperature, 300 atm pressure, 150,000 g

shock

Layers of 3 Different Silicon Carbide Materials

Slide 14

Works at high temperature > 600 °C Inherently small

Can incorporate bonding structures into deviceIntegration capability with control logic systemLess susceptibility to fatigue due high fracture

toughness of SiCNano strain resolution in 100 Hz bandwidth at

600 °C SEM image of a SiC double-folded comb-

drive resonator fabricated at UCB

– Works at high temperature applications (600°C) in oxidative environments

– Si based MEMS pressure sensors fails in harsh conditions (>150 °C, oxidation envionments, and very high pressure conditions).

– Deposition vs. Etching: precise control of diaphragm thickness through deposition gives high resolution

– 1% resolution at baseline of 300 atm up to 600 °C.

SiC Double Ended Tuning Fork Strain GaugeSiC Double Ended Tuning Fork Strain Gauge

SiC Membrane

6H-SiC Substrate

SiC Membrane

6H-SiC Substrate

SiC High-Resolution Strain Gauge

SiC Diaphragm Pressure Sensor

Slide 15

– High material toughness, high band gap, and oxidation resistance.

– Silicon-based accelerometers do not work in high-g, high electromagnetic radiation, and high temperatures (>150°C).

– Successful operation even above 150,000 g’s

– 1g resolution at 600 °C

SiC membrane

Metallization

Piezoresistive elements

Outer resisterInner resister

Compressive Stress

Tensile Stressg-force g-force

Proof mass

SiC membrane

Metallization

Piezoresistive elements

Outer resisterInner resister

Compressive Stress

Tensile Stressg-force g-force

Proof mass

SiC membrane

Metallization

Piezoresistive elements Piezoresistive elements

Outer resisterInner resister

Compressive Stress

Tensile Stressg-force g-force

Outer resisterInner resister

Compressive Stress

Tensile Stressg-force g-force

Proof mass

– Material compatibility.

– Monolithic integration with other sensors and logic circuits due to process compatibility whereas commercial sensors can not be integrated with this chip technology

SiC Substrate

SiC Circular Diaphragm

Metallization

Piezoresistive element (SiC or High Temp. metal)

SiC Accelerometer

SiC High-G Accelerometer

Slide 16

MEMS REPS Smart Plate

Flexible Fuel Delivery

Advanced Auxiliary

Combustion Stability & Characterization

High Specific Power Generation

MEMS Smart Plate

Signature Control

100-250 Watts

Slide 17

Engine Performance Monitoring & Control Sensors

Oxygen Sensor

Knock SensorPressure Sensors

Silicon CarbideWear Plate

Fuel Valve

Fuel Delivery

Temperature Sensors

Crank Shaft Angle Sensor

Slide 18

MEMS Enabled Portable Power

Low cost manufacturing + Low unit cost MEMS High functionality, performance

Electrical Power Shaft Work

17-4 Stainless Steel

Silicon

17-4 Stainless Steel

Silicon

Magnetic Flywheel

MEMS SystemIntegration

Low Cost ProductionLow Part Count

Traditional Materials

Slide 19

Nanowire Array Gas SensorsBackground

FabricationElectrodeposition of metal in

alumina nano-template

Advantages of DesignHigh surface area to volume ratioHigh sensitivityFast response timeLower power requirement than

conventional sensors

Porous anodic alumina template

Tin Oxide (SnO) Nanowires

A. Kolmakov, Y. Zhang, G. Cheng, M Moskovits, Adv. Mater. 2003, 15, 12.

Slide 20

Integration of NEMS and MEMS Localized Growth of Nanowires

Englander, L.Lin UC Berkeley

– Microscale structures serve as the platform for silicon nanowire synthesis resistive heaters/microbridges

– Heat is provided locally rather than globally

– Single crystal silicon & polysilicon structures serve as platforms

– Wirebond individual microbridges to a chip carrier

– Place chip carrier in a converted PECVD vacuum chamber

Slide 21

Integration of NEMS and MEMS Process Schematics Englander, L.Lin UC Berkeley

MEMS bridges are positioned in close proximity to each other

The growth bridge is resistively heated to reach the synthesis temperature

The cold bridge serves to create local electric field to assist in SiNW orientation

SiNW growth ends once contact with cold bridge takes place

E

Cold Bias Hot Growth Bridge Bridge

5μm

gap

E

Cold Bias Hot Growth Bridge Bridge

5μm

gap

Slide 22

Nanowire Array Gas Sensors Oxygen & Hydrogen Sensors

H2 Molecules

PdNi Nanowires Anode

Cathode

Change in resistance of the sensing element in the presence of hydrogen

molecules.

H

H

H

H H

HR R*

– Hydrogen gas molecules change in the electrical resistance of Pd sensing material

Oxygen Ambient Reducing Gas

Depletion O-

+

++

+

+

+

O-

O-

O-

O-

O-

CO2CO2

CO2

CO2

CO2

CO2

e-e-e-

O2 Molecules

Metal-OxideNanowires

Anode

Cathode

Schematic of the principle of operation

– Metal oxide material reacts to oxidizing and reducing gases

– 1/2O2 + e- O-

– CO + O- CO2 + e-

– The small diameter of nanowires allows the surface chemistry to alter the bulk conductivity of the wires.

Oxygen Sensor Hydrogen Sensor

Slide 23

The MINOTAUR Project

New Micro and Nano SensorsNew Manufacturing Methods

Enhanced Sensitivity and BandwidthIncreased Performance for Closed-Loop Control

Thermal, Shock and Chemical ResistanceImproved Sensor Robustness and Lifetime

Direct Sensor Measurement of DataNew Modes of Vehicle Control and Programmability

CONCLUSIONS