ee c245 – me c218 introduction to mems design fall 2008

EE C245 – ME C218Introduction to MEMS Design

Fall 2008Fall 2008

Prof Clark T C NguyenProf. Clark T.-C. Nguyen

Dept of Electrical Engineering & Computer SciencesDept. of Electrical Engineering & Computer SciencesUniversity of California at Berkeley

Berkeley, CA 94720y

L t 1 D fi iti d I ti f MEMS

EE C245: Introduction to MEMS Design Lecture 1 C. Nguyen 8/28/08 1

Lecture 1: Definition and Incentives for MEMS

Instructor: Prof. Clark T.-C. Nguyen

• Education: Ph.D., University of California at Berkeley, 1994• 1995: joined the faculty of the Dept. of EECS at the U i it f Mi hiUniversity of Michigan

• 2006: (came back) joined the faculty of the Dept. of EECS at UC Berkeleyy

• Research: exactly the topic of this course, with a heavy emphasis on vibrating RF MEMS

• T hi ( t th U fM) i l t i t i it d i • Teaching: (at the UofM) mainly transistor circuit design courses, from undergraduate to graduate

• 2001: founded Discera, the first company to commercialize f , f mp y mmvibrating RF MEMS technology

•Mid-2002 to 2005: DARPA MEMS program managerran 10 different MEMS based programsran 10 different MEMS-based programstopics: power generation, chip-scale atomic clock, gas analyzers, nuclear power sources, navigation-grade gyros,

hip li mi i m t l t l


on-chip cooling, micro environmental control

Course Overview

• Goals of the course:Accessible to a broad audience (minimal prerequisites)D i h iDesign emphasis

Exposure to the techniques useful in analytical design of structures, transducers, and process flowsof structures, transducers, and process flows

Perspective on MEMS research and commercialization circa 2008

• Related courses at UC Berkeley:EE 143: Microfabrication TechnologyCS 194 (EE 147): Introduction to MEMSCS 194 (EE 147): Introduction to MEMSME 119: Introduction to MEMS (mainly fabrication)BioEng 121: Introduction to Micro and Nano Bi t h l d Bi MEMSBiotechnology and BioMEMSME C219 – EE C246: MEMS Design

• Assumed background for EE C245: graduate standing in


Assumed background for EE C245: graduate standing in engineering or physical/bio sciences

Course Overview

• The mechanics of the course are summarized in the course handouts, given out in lecture today

C I f i ShCourse Information SheetCourse descriptionCourse mechanicsCourse mechanicsTextbooksGrading policy

S ll bSyllabusLecture by lecture timeline w/ associated reading sectionsMidterm Exam: tentatively set for Thursday, Oct. 23Final Exam: Saturday, Dec. 20, 12:30-3:30 p.m.Change this Final Exam time?Change this Final Exam time?Project due date TBD (but near semester’s end)


Lecture Outline

• Reading: Senturia, Chapter 1g p• Lecture Topics:

Definitions for MEMSMEMS roadmapMEMS roadmapBenefits of MiniaturizationExamplesp

GHz micromechanical resonatorsChip-scale atomic clockMicro gas chromatographMicro gas chromatograph


MEMS: Micro Electro Mechanical System

d d h ( E ) h• A device constructed using micromachining (MEMS) tech.• A micro-scale or smaller device/system that operates mainly via a mechanical or electromechanical meansvia a mechanical or electromechanical means

• At least some of the signals flowing through a MEMS device are best described in terms of mechanical variables, e.g., , g ,displacement, velocity, acceleration, temperature, flow

Input: Output:

MEMSvoltage, currentacceleration, velocity

light, heat …

voltage, currentacceleration, velocity

light, heat, …

Control:voltage current

[Wu, UCLA]Transducer to Convert Controlto a Mechanical voltage, current

acceleration velocity

light heat

to a Mechanical Variable (e.g., displacement,

velocity, stress,


Angle set by mechanical meansto control the path of light

light, heat, …y, ,heat, …)

Other Common Attributes of MEMS• Feature sizes measured in microns or less

Gimballed, SpinningMacro-Gyroscope

MicromechanicalVibrating Ring Gyroscope

80 mm[Najafi, Michigan]

Macro-Gyroscope Vibrating Ring Gyroscope

MEMSTechnologygy

1 mm

(for 80X sizeReduction)

•Merges computation with sensing and actuation to change the i d l h h i l ld

Signal Conditioning Circuits

way we perceive and control the physical world• Planar lithographic technology often used for fabrication

can use fab equipment identical to those needed for IC’s


can use fab equipment identical to those needed for IC showever, some fabrication steps transcend those of conventional IC processing

Bulk Micromachining and Bonding

• Use the wafer itself as the

MicromechanicalVibrating Ring Gyroscope

• Use the wafer itself as the structural material

• Adv: very large aspect Adv very large aspect ratios, thick structures

• Example: deep etching and f wafer bonding 1 mm

[Najafi, Michigan] [Pisano, UC Berkeley][Pisano, UC Berkeley]

Silicon SubstrateSilicon SubstrateSilicon SubstrateSilicon Substrate

MovableStructure Electrode

Silicon Substrate

Gl S b t t

Silicon SubstrateSilicon Substrate

Gl S b t t


Glass SubstrateGlass SubstrateMetal Interconnect

AnchorMicrorotor

(for a microengine)

Surface Micromachining

EE C245: Introduction to MEMS Design Lecture 1 C. Nguyen 8/28/08 9• Fabrication steps compatible with planar IC processing

Single-Chip Ckt/MEMS Integration• Completely monolithic, low phase noise, high-Q oscillator (effectively, an integrated crystal oscillator)

OscilloscopeOscilloscopeOutput

Waveform

• To allow the use of >600oC processing temperatures

[Nguyen, Howe 1993][Nguyen, Howe 1993]


To allow the use of >600oC processing temperatures, tungsten (instead of aluminum) is used for metallization

3D Direct-Assembled Tunable L


[Ming Wu, UCLA]

Technology Trend and Roadmap for MEMSs

108

109

DistributedStructural Digital Micromirror

Pentium 4

ompu

te

sist

ors

106

107Structural

ControlTerabit/cm2

Data Storage

DisplaysADXL-50

Digital MicromirrorDevice (DMD)CPU’s

Phased Array

bilit

y to

co

of T

rans

104

105

10

Adaptive

Integrated FluidicSystems

InertialNavigationOn a Chip

Displays

W

OMM 32x32

i-STAT 1Caliper

Phased-ArrayAntenna

crea

sing

ab

mbe

r o

2

103

104 AdaptiveOptics

Optical Switches& Aligners

Weapons,Safing, Arming,

and FusingADXL-278

Future MEMSIntegration Levels

Enabled Applications

Caliper

inc

Num

101

102

ADXL-78ADXRS

Number of Mechanical Components

100

100 101 102 103 104 105 106 107 108 109Majority of

Early MEMS


increasing ability to sense and actNumber of Mechanical Componentsy

Devices(mostly sensors)

Benefits of Size Reduction: IC’s

•Numerous benefits attained by scaling of transistors:

Higher Current Drive FasterSpeed

Higher Current DriveLower Capacitance

Higher Integration DensityLower Supply Voltage

LowerPower Lower Supply VoltagePower

Hi h Ci it C l it & E f S lHigher Circuit Complexity & Economy of Scale

• But … some drawbacks:poorer reliability poorer reliability (e.g., hot e- effects)lower dynamic range ( l kt ff )


(analog ckts suffer)

Example: Micromechanical Accelerometer

• The MEMS Advantage:>30X size reduction for accelerometer mechanical element m

Tiny mass means small output need

accelerometer mechanical elementallows integration with IC’s

Basic Operation Principle

400 μmintegrated transistor

circuits to compensate

xo

Basic Operation Principle

maFx i =∝

xSpring

Displacement

a Inertial Force

Spring

A l ti

Proof Mass


AccelerationAnalog Devices ADXL 78

ee c245 – me c218 introduction to mems design fall 2008

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