Spring 2007 Industrial Affiliates Meeting -...

Page 1Industrial Affiliates Meeting, April 20, 2007

IMPACT Center For Advancement of MEMS/NEMS VLSI

A DARPA N/MEMS Science and Technology Fundamentals Research Center

20 April 2007

Spring 2007Industrial Affiliates Meeting


Agenda

8:30 – 9:00 am Registration – Coffee

9:00 – 9:15 Welcome and Introductions

9:15 – 9:30 IMPACT Center Overview

9:30 – 10:15 Thrust 1. Physics of Failure of Contacting MEMS Devices

10:15 – 10:45 Coffee Break

10:45 – 11:30 Thrust 2. Physics of Failure of Non-Contacting MEMS Actuators

11:30 – 12:00 Parallel Sessions: Industry Partner Caucus Scientific Advisory Board Caucus

12:00 – 12:30 pm Feedback to PIs

12:30 – 1:30 Lunch


Challenges

Grand Challenge: Realization of Reliable and Cost-Effective MEMS/NEMS-based Microsystems to Enable Revolutionary Military Capabilities

Grand Challenge: Realization of Reliable and Cost-Effective MEMS/NEMS-based Microsystems to Enable Revolutionary Military Capabilities

The proposed, fundamental physics-based, experimentally validated MEMS/NEMS multi-physics models will serve as foundation for sophisticated computer-aided design environments that will enable and expedite the design process for future, cost-effective, MEMS-based microsystems

• Enhance the understanding of experimentally-observed physical principles and processes governing MEMS/NEMS performance

• Develop deterministic & stochastic computer tools for predictive assessment of MEMS/NEMS device and system long-term performance

• Expedite the design process of MEMS-enabled micro-systems

• Enable the full exploitation of MEMS/NEMS technology for enhancing the functionality of integrated micro- and nano-systems

• Surface Physics: Complex interactions between material properties and structural behavior

• Reliability Physics: Multi-domain physics of failure attributed to

–dielectric charging–mechanical deformations –micro-cracking as a result of material defects in complex micro-structures

• Modeling: Innovative models and modeling methodologies to capture the multi-domain physics and stochastic, multi-scale complexity of MEMS/NEMS devices

ImpactFocus Center ObjectivesFundamental Science


Center Mission

Experimentaldemonstrations

Physics-basedmodel formulation

MEMS Microsystems Design Environment

Physics-Based Models

Interactive Design Visualization

Physics• Mechanical• Materials• Thermal• Electrical

MEM

S S&

T Fu

ndam

enta

lsFo

cus

Futu

re O

ppor

tuni

ties • Through experimental investigation

and fine-scale, physics-based, multi-domain modeling, understand the fundamental principles governing MEMS/NEMS performance

• Demonstrate a set of multi-domain, multi-scale computer models for predictive device functionality and life-time assessment

• Demonstrate design methodologies, and a mature design environment

• Utilize the design environment for the full exploitation of MEMS/NEMS devices in highly integrated micro-and nano-systems


Personnel

RF MEMS characterizationDr. G. Papaioannou

Investigation of dielectric charging; RF MEMS reliability & packagingDr. C. Goldsmith

MEMtronicsMechanical modeling at the micro- and nano-scaleProf. F. Sadeghi

RF MEMS fabrication, characterization and modelingProf. D. Peroulis

Thermal modeling at the micro- and nano-scale; multi-scale modelingProf. J. Murthy

RF MEMS devices and circuitsDr. E. Martinez (Center Co-Director)

Purdue UniversityExperimental characterization of thin films and small-scale metal structuresProf. R. Vinci

Mechanical modeling of thin films and small-scale metal structuresProf. H. Nied

Characterization & modeling of dielectric charging in RF MEMS switchesProf. J. C. M. Hwang

Investigation of mechanical properties of thin metal filmsProf. W. L. Brown

Lehigh University

RF MEMS fabrication; investigation of failure mechanisms; dielectric charging Prof. J. Papapolymerou

Georgia TechMulti-domain, multi-scale physics modelingProf. U. Ravaioli

RF MEMS devices and circuit modelingProf. L. Katehi (Center Co-Director)

Mechanical modeling at the micro- and nano-scale; multi-scale modelingProf. P. Geubelle

Mechanical characterization at the micro- and nano-scaleProf. I. Chasiotis

Multi-domain, multi-scale physics modeling and model order reductionProf. A. Cangellaris (Center Director)

Multi-domain, multi-scale physics modeling and model order reductionProf. N. Aluru

University of Illinois


IMPACT Center Organization

NonNon--Contacting ActuatorsContacting ActuatorsCharacterization Characterization

and Model Validationand Model ValidationTask Lead: PapapolymerouTask Lead: Papapolymerou

Characterization Characterization Of Degradation Of Degradation

BehaviorBehaviorPurdue, Lehigh, UIUCPurdue, Lehigh, UIUC

Validation Validation TestbedsTestbedsGaTechGaTech, Purdue, Lehigh, Purdue, Lehigh

Reliable MEMS Switch DesignReliable MEMS Switch DesignThrust Lead: C. GoldsmithThrust Lead: C. Goldsmith

MultiMulti--Domain Domain Physics/MultiPhysics/Multi--ScaleScale

ModelingModelingTask Lead: AluruTask Lead: Aluru

ElectricalElectrical--Mechanical Mechanical

ModelingModelingUIUC, Purdue,UIUC, Purdue,

LehighLehigh

ThermalThermal--Mechanical Mechanical

ModelingModelingUIUC, PurdueUIUC, Purdue

Switch Characterization Switch Characterization and Model Validationand Model Validation

Task Lead: HwangTask Lead: Hwang

Dielectric Dielectric ChargingCharging

Lehigh, Lehigh, GaTechGaTech

Characterization Characterization Of Degradation Of Degradation

BehaviorBehaviorPurdue, Lehigh, UIUCPurdue, Lehigh, UIUC

Validation Validation TestbedsTestbedsGaTechGaTech, Purdue, Lehigh, Purdue, Lehigh

Reliable NonReliable Non--Contacting Contacting Actuators Device DesignActuators Device DesignThrust Lead: D. PeroulisThrust Lead: D. Peroulis

Dr. Dennis Polla, DARPA PMDr. Dennis Polla, DARPA PM

Andreas Cangellaris, DirectorAndreas Cangellaris, DirectorLinda Katehi, CoLinda Katehi, Co--DirectorDirector

Edgar Martinez, CoEdgar Martinez, Co--DirectorDirector

IndustrialIndustrialAdvisory BoardAdvisory Board

ScientificScientificAdvisory CommitteeAdvisory Committee


Industry Partners

Industrial Advisory Board– Representatives from the Center’s

industrial affiliates– Advisory body to Center’s

Leadership on issues related to:• Research activities

– Changes in research focus or directions

– Review on new tasks and funding recommendation

• Opportunities for collaboration with other research teams in academia, industry and national labs

• Issues on technology transfer – Leveraging IR&D activities for

knowledge development in the Center

• MEMtronics• BAE Systems• EMAG Technologies• Fluent• Innovative Design & Technology• nGimat• Raytheon• Rockwell Collins• Rogers Corporation• Cadence Design Systems• Mentor Graphics• NASA Goddard Space Flight Center• Sandia National Laboratories

• MEMtronics• BAE Systems• EMAG Technologies• Fluent• Innovative Design & Technology• nGimat• Raytheon• Rockwell Collins• Rogers Corporation• Cadence Design Systems• Mentor Graphics• NASA Goddard Space Flight Center• Sandia National Laboratories


Scientific Advisory Board

• John (Jack) Ebel Air Force Research Lab

• Anantha Krishnan Lawrence Livermore Lab

• Art Morris wiSpry, Inc.

• Chris Nordquist Sandia National Lab

• Dev Palmer Army Research Office

• Barry Perlman US Army RDECOM

• Daniel Powell NASA


Research PlanThrust 1: Reliable contacting MEMS switches

Task 1.1: Fundamentals of material and structural effects and validated models for contacting MEMSTask 1.2: Fundamentals of electrostatic effects and dielectric charging in contacting MEMS Task 1.3: Multi-physics/multi-scale models and design framework for contacting MEMS

Thrust 2: Fundamentals of reliable non-contacting, large-displacement MEMS actuators

Task 2.1: Fundamentals of material and structural effects and validated models for non-contacting MEMS/NEMS actuators Task 2.2: Fundamentals of thermal transport and models for non-contacting MEMS/NEMS actuatorsTask 2.3: Multi-physics/multi-scale models and design framework for non-contacting MEMS/NEMS actuators

Phase 1: Demonstration of validated electrical, mechanical, and thermal models and definition of multi-physics/multi-scale framework for contact and non-contact MEMS Devices

Phase 2: Demonstration of validated multi-physics/multi-scale models for MEMS devices.

Phase 3: Demonstration of reduced order multi-physics/multi-scale models for the design of MEMS devices

Phase 4: Demonstration of validated time-domain multi-physics solver for life-time performance prediction of MEMS devices and components.

Phase 5: Demonstration of validated component-level design environment with life-time performance predictability.

Phase 6: Demonstration of validated component-level design environment with life-time performance predictability

0 12 MAC 24 MAC 36 MAC 48 MAC 60 MAC 72 MAC

Device-level ModelingDevice-level Modeling

Device-level Reduced-order ModelingDevice-level Reduced-order Modeling

Device-level Life-time Prediction Capability

Device-level Life-time Prediction Capability

Focused on Increased Complexity

Focused on Increased Complexity

FundamentalsFundamentals

OptionsOptions

Stochastic Multi-physics Analysis of MEMS Device

Reduced-Order Models

& Design

Methodology

Integrated Microsystems


Y3 Objectives & MilestonesY3 Objectives & Milestones• Y3 Quantitative Milestones

– Demonstration of non-linear, reduced-order, multi-physics/multi-scale models for the design of a MEMS/NEMS single device. Numerical solution time to be less than 1 hour.

– Design of: a) RF MEMS capacitive switch and RF resonator; b) 150o C temperature-sensing cantilever

• Y2 Quantitative Milestones– Demonstration of a validated multi-physics, multi-scale, stochastic design

framework for single-device (fixed-beam MEMS/NEMS) Numerical solution time to be less than 12 hours.

– Application to the design of capacitive contact switches, fixed-fixed beam resonators, and cantilevers.

• Y1 Quantitative Milestones– Demonstration of three validated single-physics models (electrical, mechanical,

and thermal). – Definition of a multi-physics, multi-scale, stochastic design framework for fixed-

beams MEMS/ NEMS devices (contact switch and non-contact cantilevers).


Model Validation with Experimental Data

Physics-based Model Formulation

Methodology for Methodology for PhysicsPhysics--based Model based Model

DevelopmentDevelopment

Extensive Characterization of Test Structures

Design of Appropriate Test Structures in

Support of DOE for a Given Physical Phenomenon

Definition of Design of Experiments

to Capture Physical Phenomena

DevicePerformance

Definition

Year 1

ExperimentalInvestigation ofGoverning PhysicalPhenomena

Model Development& Validation


Questions for the Scientific Advisory Board

• As every research activity, the scientific activity is expected to evolve as new discoveries are made. Currently the IMPACT Center activity is organized by MEMS-device class (i.e. contacting switches)Question: In the long run, how should we reorganize the IMPACT Center technical activity to ensure continuing progress and effective transitioning of the knowledge into practice, to achieve the vision of the Center?

• We are conscious of the fact that our research activities do not encompass all issues that could, in principle, be pursued, given the PIs expertise and interests

• Question: Are there pressing research questions pertinent to the Center’s mission that we must address over the next two years?


Questions for theIndustrial Advisory Board

• Our experimental work contributes to the better understanding of the mechanisms responsible for MEMS performance degradation– In addition to improved models, this understanding maps onto

opportunities for improved designs, better manufacturing practices, and even new MEMS-enabled devices

Question: How do we motivate industry input toward the development of new IP?

• Our long-term success is critically dependent on our ability to engage more EDA companies in our Center’s model development activities Question: How can our industry members help us with establishing strong working relationships with EDA Companies?


Agenda

8:30 – 9:00 am Registration – Coffee

9:00 – 9:15 Welcome and Introductions

9:15 – 9:30 IMPACT Center Overview

9:30 – 10:15 Thrust 1. Physics of Failure of Contacting MEMS Devices

10:15 – 10:45 Coffee Break

10:45 – 11:30 Thrust 2. Physics of Failure of Non-Contacting MEMS Actuators

11:30 – 12:00 Parallel Sessions: Industry Partner Caucus Scientific Advisory Board Caucus

12:00 – 12:30 pm Feedback to PIs

12:30 – 1:30 Lunch

Page 1April 20, 2007

Thrust 1

Physics of Failureof

Contacting MEMS Devices


Thrust 1: Contacting MEMS Devices

• Objectives:– Develop an improved

understanding of the fundamental science governing the operation of MEMS/NEMS devices which make contact

– Implement this understanding into physics-based models that emulate the underlying principles and allow extrapolation of performance and lifetime improvements

– Validate both the physics and resulting models with test structures and actual switches (and later in phase shifters and antenna subarrays)

-1

-0.5

0

0.5

1

0 100 200 300 400 500TIME (s)

CU

RR

ENT

(pA

)

-20

0

20

40

60

VOLT

AG

E (V

)

30 V off

30 V on

-1

-0.5

0

0.5

1

0 100 200 300 400 500TIME (s)

CU

RR

ENT

(pA

)

-20

0

20

40

60

VOLT

AG

E (V

)

30 V off

30 V on

Mechanical, Mechanical, material, and material, and electricalelectricalpropertiesproperties

PhysicsPhysics--based based and equivalent and equivalent circuit modelscircuit models

Fabricated test Fabricated test structures and structures and switchesswitches


Y1 Milestones/Thrust 1 TasksY1 Milestones/Thrust 1 Tasks

Year 1 Milestones– Demonstration of

three validated single-physics models (mechanical, electrical, and thermal)

– Definition of a multi-physics, multi-scale, stochastic design framework for fixed-beams MEMS/ NEMS devices

Thrust 1 TasksTask 1.1: Fundamentals of material and structural effects and validated models for contacting MEMSTask 1.2: Fundamentals of electrostatic effects and dielectric charging in contacting MEMS Task 1.3: Multi-physics/multi-scale models and design framework for contacting MEMS

-0.6

0

0.6

1.2

0 200 400 600 800TIME (s)

CU

RR

ENT

(pA

)

Positive Charging Discharging

20V30V

40V50V

-0.6

0

0.6

1.2

0 200 400 600 800TIME (s)

CU

RR

ENT

(pA

)

Positive Charging Discharging

20V30V

40V50V


Thrust 1 Progress Overview

• Fabrication/Test Bed (J. Papapolymerou)– Completed design and layout of mask set of mechanical and electrical

test structures for device characterization– Completed first round of fabrication, passed along devices for testing

• Electrical Single-Physics (J. Hwang)– Completed detailed charging characterization of first silicon nitride

samples– Extracted model parameters, including time constants, densities, and

voltage dependence• Material/Mechanical Single-Physics (R. Vinci)

– Established Ansys mechanical models for switch test structures– Completed first set of time-dependant modulus measurements on gold

test samples• Modeling Framework (N. Aluru)

– Initial framework established for multi-physics simulation of mechanical, electrical, and fluidic domains

– Initial results derived for simple test structure-type examples


Multi-physics/multi-scale design framework Validation of physics-based models for contact switch

Electrical, and mechanical characterization

Fabrication of test structures

Design of contact switch mask

SepAugJulJunMayAprMarFebJan

Thrust 1: Schedule

Schedule (1/07-8/07)Month

Task

Phase IMilestone

Phase IMilestone

Page 1

Thrust 1

Development of MEMS/MIM Structures &Initial Study of Dielectric Charging

John PapapolymerouGeorgia Institute of Technology

[email protected]

Page 2

Thrust 1: Facilities

Microelectronics Research Center: Approximately 8,000 sq.ft. of cleanroom areasproviding complete microfabrication capabilities

Main Fabrication Services Include:• Substrate Cleaning• Deposition• Doping• Etching• Lithography (regular + e-beam)• Thermal Processing• Metrology• Mask Design and Production

Measurement Capabilities:• 15,000 sq.ft.• S-parameters (40MHz-110 GHz)• Load-Pull (20 GHz)• Noise (20 GHz)• Antenna Chamber• I-V, C-V MEMS• High Temperature, Cryogenic

High Frequency Lab Management

dc Testing

ac Testing

RF Noise Testing

Load-Pull Testing

Multi-Gigabits Testing

Cryogenic Testing

Infra-Red Testing

Antenna Testing

HF Noise System(2-26GHz)

S-Parameters System(0.045-50GHz)

S-Parameters System(2-110GHz)

Load-Pull System(0.8-18GHz)

RF Cryogenic Chamber(18-350K)

LF Noise System

Load-Pull System(1.8-18GHz)

Echo-Chamber

Multi-gigabits serial datacom itemTesting bench

S-Para. System(4-port / 50GHz)

Prototyping Station

HF Lab Management

Page 3

Thrust 1: Facilities

RF MEMS Testbed: C-V/I-V set-up

Page 4

Thrust 1: Fabrication of Test Structures

E-beam evaporate & pattern gold seed layer

Silicon Nitride Photoresist

Deposit & pattern Silicon Nitride (or Oxide)

RIE of Silicon Nitride and PR removal

PhotoresistGold

E-beam evaporate gold bridge seed layer

Photoresist

Patterning of sacrificial layer (photoresist)

Photoresist

Gold

Photoresist

Patterning of 4th PR layer & Au electroplating

PhotoresistGold

Remove PR & chemical etch of bridge seed layer

Strip photoresist and CO2 release

E-beam evaporate & pattern gold seed layer

Silicon Nitride PhotoresistSilicon Nitride Photoresist

Deposit & pattern Silicon Nitride (or Oxide)

RIE of Silicon Nitride and PR removal

PhotoresistGold


PhotoresistGold


Photoresist


Photoresist


Photoresist

Gold

Photoresist

Photoresist

Gold

Photoresist

Patterning of 4th PR layer & Au electroplating

PhotoresistGold


PhotoresistGold


Strip photoresist and CO2 releaseStrip photoresist and CO2 release

Capacitive RF MEMS Switch Fab Process

Page 5

Thrust 1: Fabrication ofTest Structures

Mask Layout• Mask 1 (Mechanical Mask)

– Mechanical/material test structure (top)

• Mask 2 (Switch Mask)– RF MEMS switches– Switch test structures– TRL calibration structures– Capacitor structures– Stress structures– Thickness structures– Resistivity structures– Mech/material test structure

(bottom)

Page 6

Thrust 1: Fabricated Samples forElectrical Characterization

Page 7

Fabrication Details for Switches/Capacitors:• SixNy with thickness of 200 nm and 400 nm• Metalization: Gold and Aluminum• Various switch geometries (meander, bow-tie etc.)• High temperature issue during evaporationcycle led to switch failure

• Issue is currently being addressedwith assistance from cleanroom staff• MIM capacitors ok• Older switches with 200nm thick

nitride ok

Thrust 1: Fabricated Samples forElectrical Characterization

Page 8

Thrust 1: Investigation ofDielectric Charging

Contact-less charging• Dipoles orientation, produced by rotation of

charges or migration of charges• Space charge (intrinsic) arising from

redistribution of pre-existing and/or filed generated charge carriers

Contacted charging• Space charge (extrinsic) arising from charges

injected into dielectric through various mechanisms

Dipoles

Space charge

Space charge, injected charges

Space charge

Dipoles

Physics of the Dielectric-Charging

Page 9

Thrust 1: Investigation ofDielectric Charging

Contact-less charging

ΔV -ΔV +

Charge build-up induced C-V hysterisis

• Charge build-up at dielectric surface increases the charge of suspended electrode

• As a result the electrostatic force increases with time, hence the capacitance

• The C-V characteristic will exhibit a hysterisis

• The bias for capacitance minimum indicates the sign of dielectric surface charge

• Opposite polarity of bias voltage for capacitance minimum

G. Papaioannou, G. Wang, D. Bessas and J. Papapolymerou in EuMW 2006

-40 -30 -20 -10 0 10 20 30 40

0.2

0.4

0.6

0.8

1.0

1.2

1.4

1.6

C

[

pF]

V [V]

T = 300K

Charge build-up induced C-V hysterisis

Contacted charging

G. Papaioannou, M. Exarchos, V. Theonas, G. Wang and J. Papapolymerou, IEEE MTT 53, 3467, (2005)

Page 10

Summary/Future Work

• Developed first set of MEMS/MIM and mechanical structures for gold metalization

• Initial study of dielectric charging effect based on C-V characteristics

• Complete fabrication of MEMS switches and MIMs for 200 nm/400 nm of SixNy and possibly other dielectric materials for both gold and Aluminum metals

• Electrical characterization (C-V) for MEMS switches under different temperatures for model extraction


Electrical Characterization

Jim HwangLehigh [email protected]

Thrust 1


Objective ofElectrical Characterization

• Leverage methodology developed under HERMIT program to separate top and bottom charging of dielectric

• Extract trap densities and charging/ discharging time constants from transient current and capacitance measurements on capacitive test structures

• Validate charging model on MEMS switches

• Extrapolate charging model for different control-voltage waveforms and temperatures

• Extend understanding and model to different metal/dielectric combinations

DIELECTRIC

TOP METAL ELECTRODEC

ON

TRO

L VO

LTA

GE

BOTTOM METAL ELECTRODE

DIELECTRIC

TOP METAL ELECTRODEC

ON

TRO

L VO

LTA

GE

0.001

0.01

0.1

1

10

0 100 200 300 400 500

TIME (s)

CU

RR

ENT

(pA

)

20 V

30 V

40 V Discharging

Charging

0.001

0.01

0.1

1

10

0 100 200 300 400 500

TIME (s)

CU

RR

ENT

(pA

)

20 V

30 V

40 V Discharging

Charging

1 10 100 100060

61

62

63

64

65PositiveNegative

Δ C

[fF]

t [sec]


Electrical Test Structures

LPCVD SiO2,, 6µm

Plated Au, 1µm

Evaporated Ti/Au/Ti, 0.2µm

Air, 1.7µm

PECVD SiN, 0.45µmTi/Au, 0.2µm

300µmSwitch Cross Section

@ 100:1 aspect ratio

Test Capacitors


-1.5

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(pA

)Charging/Discharging of

500µm x 500µm Capacitors

0 01,2

exp( / )[1 exp( / )]exp( / )J J J JON C OFF D

J

Q Q V V t tτ τ=

= − − −∑

Charging

50V40V30V20V

Discharging

Charging Discharging

−20V−30V−40V−50V


1.0E+09

1.0E+10

1.0E+11

1.0E+12

-60 -30 0 30 60

CONTROL VOLTAGE (V)

Q0

(q/c

m2)

0

100

200

300

-60 -40 -20 0 20 40 60

CONTROL VOLTAGE (V)

TIM

E C

ON

STA

NT

(s)

Time & Voltage Dependence

Positive Voltage

J Q00+ (q/cm2) V0+ (V) τC+ (s) τD+ (s)

1 2 x 109 17 11 18

2 3 x 109 16 85 178

Negative Voltage

J Q00− (q/cm2) V0− (V) τC− (s) τD− (s)

1 - 2 x 109 20 11 15

2 - 4 x 109 16 88 172

(□)τC1 (х)τD1 (Δ)τC2 (+)τD2

QO2+

QO1+

QO2−

QO1−


-1.5

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TIME (s)

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DEN

SITY

(µA

/cm

2 )

-0.4

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(pA

) 2

2

2

2

Uniformity and Scaling

−30V Charging −70V Charging


• Dielectric charging study methodology developed under HERMIT program appears to be applicable to present samples

• Charging model parameters such as steady-state charge density, time constants, and voltage dependence extracted from metal-insulator-metal capacitors

• Next quarter – 1) use the extracted charging model to predict actuation-voltage shift of switches, 2) validate model on switches, 3) asses top vs. bottom charging of switches, and 4) repeat on more wafers

Summary ofElectrical Characterization


Task 1.1: Fundamentals of material and

structural effects and validated models for

contacting MEMS

X. Yan, B. Baloglu

R.P. Vinci, W.L. Brown, H.F. Nied


Goals and Approach

1.1 Mechanical

testing and

modeling

1.3 Finite

Element

Modeling

1.2 Electrostatic

testing and

modeling DIELECTRIC

BOTTOM ELECTRODE

AIR

POST POST

TOP ELECTRODE

MOVABLE MEMBRANE

HINGE HINGE

Combined electrostatic and

mechanical structures, leading to

validated physics-based models

Goal: characterize coupled mechanical and dielectric charging contributions to stiction

failure; develop and validate physics-based models for test structures and real switches


1.1 Mechanical testing

2cm

Si :730µm

SiNx : 210nm

SiNx : 210nm

After metal deposition:

Au or Al

SiNx membrane : 2 ! 12 or 3 ! 12 mm

KOH etch

Retain nitride membrane during

testing for integrity and to allow

metal compressive residual stress

Strip backside nitride to create

freestanding metal film for

separation of interface effects on

behavior (film must be pinhole

free and tensile)

Mechanical test

specimen fabrication:

Intention: approximate electrostatic load & uniaxial strain with pressure load and

pseudo-uniaxial strain to allow purely mechanical test of time-dependent behavior

N2 gas

Metal plategap

Bulge height increases & capacity

increases; center region is under

approximately uniaxial strain


Load-unload cycles

MPa

GPaE

comp

comp

1.40

6.94

)(0

)(

=

=

!

MPa

GPaE

Au

Au

4.16

6.68

)(0

)(

!=

=

"


Au stress relaxation

Keep strain = 0.00248 tfinal ! 11 hours

E(t ) = 70.888 + 3.7326e(

!t

3367.6)

+ 1.8563e(

!t

151.71)

+ 0.71619e(

!t

7.4307)

+ 0.71619e(

!t

7.3974)

Effect is larger for Al, and larger

at elevated temperatures


1.3 Viscoelastic model

Si Substrate

Post Post

tm

tox

tetd

g0

MembraneSi3N4

Lower ElectrodeSiO2

Si Substrate

Post Post

tm

tox

tetd

g0

MembraneSi3N4

Lower ElectrodeSiO2

Intention: develop and validate models for mechanical and electrostatic pull-down and

release behaviors


Viscoelastic results

UY vs Time

-6.00E-08

-5.50E-08

-5.00E-08

-4.50E-08

-4.00E-08

-3.50E-08

-3.00E-08

-2.50E-08

-2.00E-08

-1.50E-08

-1.00E-08

-5.00E-09

0.00E+00

0 10 20 30 40 50 60

Time

UY

Held for 10s Held for20s Held for 30s Held for 60s Held for 300s

• Relaxation behavior (60 seconds) for different hold times

• Associated with reduced pull-off force, enhanced stiction


Real Membrane Designs

Photos taken from switch samples tested in the Compound

Semiconductor Technology Laboratory at Lehigh University


Linear Elastic Displacements

Membrane-1 Membrane-2 Membrane-3

Membrane-4Membrane-5 Membrane-6


Resultant Forces

9382.202.061AuMembrane-6 (M-6)

362.200.0791AuMembrane-5 (M-5)

1842.200.411AuMembrane-4 (M-4)

442.200.0961AuMembrane-3 (M-3)

4000.960.381AuMembrane-2 (M-2)

1141.120.130.3AlMembrane-1 (M-1)

FAvarage (N/m2)A (m2 x10-8)Ftotal (Nx10-5)tm (µm)Mat.

Calculated Pull-down Forces for each Membrane Geometry

Assumes linear elasticity


Issues/Improvements

• Successes

– 1.1: Initial mechanical structures fabricated at Lehigh and GA Tech

– 1.1: Initial combined structures fabricated at GA Tech

– 1.1: Initial room temperature measurements of Lehigh gold

– 1.1 & 1.3: Transfer of viscoelastic model to Task 1.3

– 1.3: viscoelastic modeling of simple structure

– 1.3: linear elastic modeling of realistic structures

• Sample fabrication across facilities has had growing pains, newfabrication approach conceived

• Mechanical testing upgraded for true constant strain

• Temperature control capability being added to mechanical test

• Finite Element Modeling along two separate paths (simplegeometry/complex physics & reverse)

– Currently combining models to allow use of viscoelastic mechanicalmeasurements for analysis of real structures


Plans for Next Quarter

• Deposition of Al alloys by MEMtronics

• Deposition of Au at GA Tech and Purdue

• Extensive mechanical testing of Lehigh,

GA Tech, and Purdue gold

• Coupling between viscoelastic

measurements and realistic FE modeling

• Initial electrostatic measurements of hybrid

test structure


Computational Framework for Multi-Physics Multi-Scale Modeling

N. Aluru, A.C. Cangellaris


Multi-Physics Modeling

• Lagrangian framework for mechanical, electrical and fluidic energy domains• No mesh movement

• Fast computational methods• Full Newton methods: all cross-coupling terms are computed

accurately enhancing convergence• Efficient stochastic modeling to account for fabrication process induced

variations and uncertainties in model parameters• Uncertainties in mechanical energy domain

• Material properties (e.g. Young’s modulus, Poisson ratio, etc.)• Geometry (roughness, gaps, non-uniformity, etc.)• Noise in applied signals, boundary conditions

• Uncertainties in electrostatic energy domain• Material properties (e.g. dielectric constant)• Geometry (roughness, gaps, etc.)• Applied electrical potentials

• Design iteration-oriented macromodel generation through model order reduction

Desirable Attributes


Coupled Electrostatic-Mechanical Modeling of Capacitive Switch

• Model development based on experimentally-obtained understanding and data

• Coupled electro-mechanical modeling• Incorporate modeling of dielectric charging

• Comprehensive geometry/material modeling• Inhomogeneous domains favor a a finite element-based model

• Explore ways to enhance efficiencyof numerical solution • Lagrangian framework• Equivalent electrostatic problem• Algebraic multigrid solver for electrostatic and mechanical domains


Equivalent Electrostatic Problem (1)

Initial position of top surface

x

Bottom electrode (ground)

Equipotential surface: V0

x0

L1(x0)Top electrode

Flux lines are perpendicular to the two electrodes

L2(x0)

Mathematical non-equipotential surface Sf

xV(x0)

Bottom electrode (ground)

1 0 2 00 0

2 0

( ) ( )( )( )

L x L xV x VL x+

≈

Physical Domain

Equivalent Problem



Advantages:

• Grid remains constant, so no mesh updates needed

• Enhances efficiency of multigrid/iterative solution

• Facilitates coupling with mechanical modeling tool

2d

0 d

( , ) 0 in ( ) on

x yx Vφ

φ∇ = Ω

= Γ

20

0

( , ) 0 in ( ) ( ( )) on

x yx V u xφ

φ∇ = Ω

= Γ

Electrostatic Problem on Deformed Domain Equivalent Problem on Fixed Domain

ΓdΓ0

u(x)



Validation Study 1: Cantilever MEMS SwitchDimensions (μm)bl = 150bh = 2.0gap = 4.5gl = 90gh = 1.5

Tip deflection (microns)

-1.1872-1.1479120-0.5519-0.556390-0.2253-0.228960

Equivalent BVPANSYSVoltage

(V)



Validation Study 2: RF MEMS Capacitive Switch

Dimensions (μm)Lupper = 300t = 0.8g0 = 3.15td = 0.15Llower = 100tm = 0.8tox = 0.4


On-going Activities

• Demonstration of transient coupled electrical-mechanical simulation (June 2007)

• Incorporation of dielectric charging physics model in the coupled electrical-mechanical simulation (August 2007)


Thrust 2Thrust 2

Physics of Failure of

Non-contacting, Large Displacement MEMS/NEMS Actuators


Thrust 2: Non-ContactingMEMS/NEMS Actuators

Extraction of accurate stress-strain curves for large-displacement actuatorsCapture the impact of material microstructure, texture and grain size on mechanical modelingFully-coupled, dynamic, stochastic, multi-physics (electric, mechanical, thermal, fluidic) modeling and systematic, non-linear, reduced-order modeling of MEMS/NEMSThermal transport across interfaces and at sub-micron scales Characterization of fabrication process-induced variations/uncertainties in geometric and material parameters

Research Activities


Conventional MEMS ActuatorsDesign Methodology

Assumed Material Assumed Material PropertiesProperties

Deterministic Deterministic MultiMulti--Physics Physics

ModelingModeling

Device PerformanceDevice Performance

Device Device Model Model

Questionable Questionable Agreement Agreement

between models between models and experimentsand experiments

Series of unquantifiable hypotheses and “best guesses” for actualmaterial and geometricproperties


Thrust-2 New Design Methodology

Probability of Probability of Device FailureDevice Failure

Assumed Material Assumed Material PropertiesProperties

Deterministic Deterministic MultiMulti--Physics Physics

ModelingModeling

Device PerformanceDevice Performance

InIn--situ situ extracted extracted

material and material and geometrical geometrical propertiesproperties

Stochastic Stochastic Models for Models for Materials Materials StructureStructure

Device Device Model Model

Good Agreement Good Agreement between models between models and experimentsand experiments


Objectives/Milestones

• Y1 Quantitative Milestones– Demonstration of validated single-physics models

(mechanical, and thermal). – Definition of a multi-physics, multi-scale, stochastic design

framework for non-contact MEMS actuators.

40%60%Thermal Domain

60%50%Uncertainty Quantification

40%70%Mechanical Domain

Modeling EffortsCompleted for Y1

Experimental EffortsCompleted for Y1

Current Status (April 2007)


Accomplishments to Date

Strain Rate Dependence of Mechanical Behavior of Metallic MEMS (Au and Pt). Models incorporating these results are currently under development.

Uncertainty modeling of microstructures with fast and accurate methods initiated. Experimental efforts that focus on characterizing the fabrication process uncertainties is currently underway.

Thermal transport model across interfaces and at sub-micron scales initiated. Experimental effort to support this activity is currently underway.


Multi-physics/multi-scale design framework Validation of physics-based models for non-contact actuators

Electrical, thermal and mechanical characterization

Fabrication of test structures

Design of non-contact actuator mask

AugJulJunMayAprMarFebJan

Thrust 2: Schedule

Schedule (1/07-6/07) – We are on schedule so farMonth

Task


Mechanical Behavior Experiments and ModelsX. Tang, K. Jonnalagadda, I. Chasiotis, P. Geubelle

Aerospace Engineering, University of Illinois at Urbana-Champaign

Sample Fabrication D. Peroulis1, R. Polcawich2

1Purdue University, 2Army Research Laboratory, Adelphi, MD

Strain Rate Dependence of MechanicalBehavior of Metallic MEMS

Acknowledgements:DARPA IMPACT Center, Program Manager: Dr. D. Polla

ARO, Program Manager: Dr. B. LaMattina

Page 9Industrial Affiliates Meeting, April 20, 2007• I. Chasiotis, et al. "Strain Rate Effects on the Mechanical Behavior of Nanocrystalline Au Films," Thin Solid

Films 515, pp. 3183-3189, (2007)

Microscale tension testing apparatus

UV adhesive gripping

Nominal strain rates: 10-6 - 10-3 s-1

200× and 500× optical images at 15 fps50,000 fps camera to be implementedStrain is calculated from optical images by Digital Image Correlation (DIC)

Approach: Full-Field MechanicalBehavior Experiments


Sample dimensions: L= 1000 μmT= 400 nmW= 100-200 μm

Specimen grip

Specimen Preparation and Geometry


100 μm 100 μm

Strain Measurement - Digital Image Correlation (DIC)

Page 12Industrial Affiliates Meeting, April 20, 2007 shear failure

Unloading elastic modulus 178.7 GPa (consistent with bulk value of 172 GPa)Proportional limit of 680 MPa (much higher than bulk value: 125-165 MPa)Ultimate stress and strain: 1800 MPa and 4.25%Ductility increased but proportional limit decreased significantly compared to higher strain rates

Pt Films: Tests @ = 10-6 s-1ε&


1490

1537

1541

1640

Yield stress (MPa)

4.2%1800680178.78.3 x 10-65

4.3%1920720181.88.3 x 10-54

3.9%1870904173.17.0 x 10-43

4.0%1870876173.87.1 x 10-42

3.4%19901000186.73.6 x 10-31

Ultimate strain

UTS (MPa)Proportional limit (MPa)

E (GPa)Strain rate (s-1)Pt

Effect of Strain Rate on Mechanical Behavior of Pt Films


Elastic modulus E= 178.3 ± 6.2 GPa was not affected by the strain rateTensile strength increased marginally with strain rate (1800-2000 MPa) and was significantly larger than bulk (~240 MPa), which is potentially a consequence of limited defect density in the filmsThe proportional limit decreased by more than 30% in the entire strain range

Ductility changed by 20% between 10-6 to 10-3 s-1

Tensile Properties of Pt Films


Tensile Response of Notched Pt Film


500 x Magnification

CPW Au: Width 50 μm, thickness 1.2 μm

Test of SiO2 - Au Films


Multiscale Modeling of Damage in MEMS

Objective: Multiscale framework to relate grain-level damage evolution (Experiments by I. Chasiotis) to macroscale performance of MEMS (Experiments by D. Peroulis and simulations by N. Aluru)

Approach: Mathematical theory of homogenization, based on asymptotic expansion of stress and strain fields

Current activities:

Generation of realistic granular microstructure using and experimental inputs (texture data from I. Chasiotis) Voronoitessellation

Multiscale prediction of elastic properties


Implemented a method (with Pt films) and test apparatus to measure full field strains with optical microscopy and at a variety of strain rates relevant to MEMS operation

The mechanical response of Pt samples was measured at 4 strain rates and the elastic modulus, elastic limit, and ductility were computed

Pt films were less susceptible to strain rate compared to Au films tested in the past

Deformation and failure of Pt was due to micro-plasticity without the formation of shear bands (contrary to Au)

Decreasing loading rate resulted in 40% reduction in the elastic limit of Pt

The elastic range of Pt films was 0.4%. In comparison, the elastic limit of Au/SiO2 films was less than 0.1%: rather small given common operating and thermal loading conditions

Concluding Remarks


Uncertainty ModelingN.R. Aluru, A. Cangellaris

University of Illinois at Urbana-Champaign


Uncertainties or stochastic parameters are variations in the physical quantities that are important for device function

ExamplesUncertainties in geometrical features such as dimensions, gap between electrodes, etc.Uncertain operating environments (e.g. temperature, pressure, fluctuations in applied volatges, etc.)Uncertainties in material and physical properties can be significantFabrication errors can lead to imperfect contacts and uncertainties in boundary conditions

Uncertainties


Why are uncertainties important?Reliability, failure and life-cycle tests can not be quantified with out accounting for uncertaintiesDevices can fail sooner than expectedDevices can operate in a different regime than what they were designed/intended for (e.g. chaotic behavior, nonlinear regime, etc.)

Uncertainties

Design for worst caseVery conservative approachCan be quite expensive, inefficientDesigners would like to do better!

Standard approaches for uncertainty quantificationMonte Carlo methods (expensive)Sensitivity analysis (limited to small variations)Perturbation methods (limited to small variations)


Important variationsMechanical properties (e.g. Young’s modulus, Poisson’s ratio)Physical properties (e.g. thermal conductivity, electrical conductivity, diffusion coefficients, etc.)GeometryBoundary conditions (imperfect metal contacts, fluctuations in the applied voltages, etc.), residual stresses, etc.

UQ in MEMS

ApproachExtend our earlier research on deterministic analysis of electrostatic MEMS (coupled electrostatic and mechanical domains) to account for uncertaintiesInvestigate the effect of uncertainties in material properties in mechanical analysisUncertainties in mechanical properties lead to uncertain displacementsInvestigate the effect of uncertain geometries in electrostatic analysisPerform coupled analysis of stochastic mechanical/electrostatic domains


Geometrical Uncertainties

Deterministic problem: For a given set of conductors and applied potential difference, compute the surface charge density and the capacitanceStochastic problem: For a given set of conductors with uncertain geometry and applied potential difference, quantify the uncertainty associated with the surface charge density and the capacitance

Approach: Model the uncertain geometry and unknown surface charge density as random fields, which are then expanded in terms of independent random variables using polynomial chaos expansions


Deterministic Lagrangian Electrostatics

Lets assume the conductors have undergone some shape changes (e.g. due to electrothermal effects, etc.)In classical electrostatic analysis, we need to solve a potential equation in the domain exterior to all the conductorsAn efficient approach is to use boundary integral equation formulationThe boundary integral equations for electrostatic analysis are given by

Green’s function (2D)

Question: Instead of using the deformed geometry, can we use the original geometry to perform electrostatic analysis?


Deterministic Lagrangian Electrostatics

Lagrangian electrostatics: Mathematical transformation to solve the electrostatic equations on the undeformed geometry of the conductors

Lagrangian BIEBoundary integral equations (BIE)

[Li and Aluru, 2002]

Deformed geometry = Undeformed geometry + a displacement at each point


Stochastic Lagrangian Electrostatics

Uncertain geometry Mean geometry Uncertain displacement

Stochastic Lagrangian BIE


Stochastic Discretization

Input uncertainty:

Using Galerkin projection in the space of PC basic functions :

Discretize in space using Boundary Element Method (BEM)


Example: Single Line Over a Ground Plane

Mean: ; Standard deviation

We assume , Gaussian RV

Objective: Study the effect of uncertain gap H on the capacitance between the line and ground plane

Surface charge density profilein the mean configuration

Mean surfacecharge density with error barsat the bottomsurface


Example: Single Line Over a Ground Plane

Empirical formula for capacitance:

PDF of capacitance for PC, Emp and MC


Example: Comb Drive

Transverse comb drive

Movable tooth Fixed tooth

Effect of uncertain tooth thickness on the capacitance and net electrostatic force

Uncertain displacement :


Example: Comb Drive

PDF of capacitance using PC

Mean vertical force with error bars for different applied voltages


Coming Soon …….Treatment of uncertainties in material propertiesCoupled electromechanical analysis with uncertainties in material properties

The only thing we can be certain of is the uncertainty; so why not deal with it

ImpactWe will be able to quantify for the first time how uncertainties in material properties can effect electromechanical behavior (e.g. pull-in voltages, etc.)Identify the critical parameter(s) that deteriorate device performanceImprove device reliability by controlling the critical parameter(s)Significant reduction in cost and resources when compared to worst-case designs


Experimental Investigation of Fabrication Uncertainties: Fast and Accurate Metrology Methods

D. Peroulis, J.V. ClarkSchool of Electical and Computer Engineering, Birck Nanotechnology Center,

School of Mechanical Engineering, Purdue University


What are the basic properties of your materials?

How do they vary across your wafer?

How do they vary from run-to-run?

How does your layout compare to the actual fabricated device?

What is the cost (time & $$$) for measuring onegeometrical/material property?

How accurately can you measure your geometrical/materialproperties ?

What is the reliability or failure mechanisms of your devices?

Basic Questions


Example: Tang Resonator

Tang Resonator

Example question: How Δw affects performance?


Example: Tang Resonator

Δw affects width, gap, length; mass, damping, stiffness; resistance, capacitance; etc.


Material UncertaintyPolySi – Most common MEMS material

Various methods and group (year published)

You

ng’s

mod

ulus

of p

olys

ilicon

[GPa

]


Relative Error Due to Both Δw and ΔE

Rel

ativ

e er

ror i

n st

iffne

ss


What Needs to Be Measured?

Material Propertieso E, vo stresso densityo CTEo piezo coefficiento conductivityo …

Geometric Propertieso length, width, gapo thicknesso displacement/forceo radius of curvatureo …

Material degradationo creepo fatigueo …

Fabrication process variationso run-to-runo across the wafero …

Post-process variationso packagingo flip-chip bondingo …


Example Test Structure


Example Test Structure

Tensile fracture by W. Sharpe (JHU)

Hypothesis: Fabrication errors are locally identical


Derivation of Δw2

, 012

aa eff a a

a

CF k y Vy

Δ= Δ = Δ

Δ2

, 012

bb eff b b

b

CF k y Vy

Δ= Δ = Δ

Δ

1 3

,1 3

1

1

aa layou

b

t

a

b

b

Cn

C

Cw w

C

⎛ ⎞⎛ ⎞⎜ ⎟−⎜ ⎟Δ⎜ ⎟⎝ ⎠Δ = ⎜ ⎟

⎛ ⎞⎜ ⎟−⎜ ⎟⎜ ⎟Δ⎝ ⎠⎝ ⎠

Δ

Δ

,

3,

,

3,

eff a a

a

eff

eff b b

eff

a a

b b

b

k y

yk w

k y

k wy

Δ

Δ

Δ =

⇓

Δ= =

02

02 1

212

b

b

b

a

a

a a

b

CCVy

y

Vy

y CC

ΔΔΔ =

Δ

⇓Δ Δ

=

ΔΔ

Δ Δ

=

Measurement of Δw is in terms of precisely measured capacitanceand exactly known layout parameters.

=

Experiments are underway


Systematic Errors: Food for Thought

Ti/SiO2 beams

How can this be modeled?

How can it be experimentally characterized?

Can such effects be used formore robust devices?


Thermal ModelingJ. Murthy

School of Mechanical Engineering, Purdue University

U. RavaioliECE Department, University of Illinois


Contacting and Non-Contacting MEMS

Contacting MEMS

Non-Contacting MEMS

Complex physics involving coupling of electrical, thermal and mechanical domains

Radant MEMS Memtronics switch Lincoln Lab switch

Pourkamali, et al (2003)


Thermal Transport Issues in MEMS

For silicon MEMs structures:– Heat transfer in semiconductors and dielectrics is by phonon transport– When phonon mean free path (~300 nm) becomes comparable to layer

thickness, sub-continuum transport must be considered– Phonon transport across multi-material interfaces poorly understood– Electro-thermal coupling poorly understood

L

Λ<<L

L

Λ>>L

Two regimes, (a) Fourier’s law is valid, (b) Fourier’s law is invalid, Λ is the mean free path of the heat carrier (phonons or electrons)

(a) (b)


Heat Transport in Silicon

.

( )scat

f fft t

∂ ∂⎛ ⎞+∇⋅ = ⎜ ⎟∂ ∂⎝ ⎠v

Boltzmann transport equation for phonons:

Phonons are characterized by polarization and dispersion.

Electron-phonon scattering during Joule heating transfers energy to specific phonon groups

MEMs temperature depends on which phonons receive this energy and how fast they move

Efficient solution techniques have been devised to solve BTE

Frequency vs. reduced wave number in (100) direction for silicon

Narumanchi, Murthy and Amon, ASME JHT 2003,2005

Wang and Murthy, ASME IMECE 2006


Example: Electrothermal Transportin PD/SOI nMOSFET

STI

BOX

M1

Silicon substrate

Metallization Layers

Kumar, S., Kim, K., Joshi, R. V., Chuang, C. T., and Murthy, J. Y.; Self-Consistent Electro-Thermal Modeling For FinFetTechnologies; ICCAD, San Jose, CA, November 5-9, 2006.Pascual-Gutiérrez, J., Murthy, J.Y., Viskanta R., Joshi, R.V., Chuang,C-T, and Kang, S.S.;Simulation of Nano-Scale Multi-

Fingered PD/SOI MOSFETs using Boltzmann Transport Equation; ASME National Heat Transfer Conference, HT-FED2004-56375, Charlotte, NC, July 2004

ChannelCoupled Fourier and phonon BTE calculations of temperature field in multi-material complex structures.

Heat generation from TAURUS simulation


Interface Physics: Acoustic Impedance

B: Heavy atoms (Mass 4M)

A: Light atoms (Mass M)

0.0 0.2 0.4 0.6 0.8 1.00

2

4

6

8

10

12

14

16

2 / aπ

dispersion for A dispersion for B

frequ

ency

(Thz

)wave vector

K/(2π/a)

Freq

uenc

y (T

Hz)

Material B has much lower frequency range. So high-frequency phonons cannot cross from A to B


Phonon Transmissivity Across Interface

• Only low-frequency phonons are transmitted

• Only these phonons have a density of states on the heavy side

• High frequency phonons have no counterpart on the heavy side and are reflected

0 2 4 6 8 10 120 .0

0 .1

0 .2

0 .3

0 .4

0 .5

0 .6

0 .7

0 .8

0 .9

1 .0

trans

mis

sion

f re q u e n cy (T H z)

Frequency-dependent transmissivity of LA phonons across interface (Lin and Murthy, 2006)

Tran

smis

sivi

ty

Frequency (THz)

Cut-off


Thermal Transport in Metals

• In metals, thermal transport is primarily by free electrons• Thermal and electrical transport are related through the

Wiedemann-Franz Law

• For thin metal films, size effects become important when the carrier mfp (~40nm) competes with layer thickness. A simplified Boltzmann transport equation (BTE) could be used.

• For thicker layers, ohmic conduction may be assumed.• Thermal and electrical conductivity may be found for confined

structures from the BTE.

k: Thermal conductivity

σ: Electrical conductivity

L: Lorenz number

T: Temperature

k LTσ=


Electro-Thermal Models

• Initial approach is to assume continuum theory to be valid

• Fourier transport for heat• Ohmic conduction for computing Joule heating

source• Simple interface resistance models for multilayered

structures• Detailed modeling of heat losses to environment,

both convective and radiative• Predict temperature and adjust models and

properties to match experiment• More expensive BTE models will be employed to gain

better understanding once limits of conventional models are reached

• Focus on Au and Ti/Au structures in Year 1.


Simulation Approach

• Unstructured, solution-adaptive finite volume scheme widely used for continuum fluid flow and heat transfer simulation

• Fourier conduction & Joule heating in solid layers

• Navier-Stokes and energy equation solution for fluid flow and heat transfer outside

• Gray-diffuse surface-to surface exchange model for radiativeexchange

S.R. Mathur and J.Y. Murthy, Numerical Heat Transfer, Vol. 31, No. 2,1997.

J.Y. Murthy and S.R. Mathur, Journal of Heat Transfer, Vol.120, 1998.


Closure

• Thermal modeling of MEMS structures is underway

• Continuum-based models for thermal transport with Joule heating are being completed

• Comparisons with measurements will be completed this summer


Questions for the Scientific Advisory Board

• As every research activity, the scientific activity is expected to evolve as new discoveries are made. Currently the IMPACT Center activity is organized by MEMS-device class (i.e. contacting switches)Question: In the long run, how should we reorganize the IMPACT Center technical activity to ensure continuing progress and effective transitioning of the knowledge into practice, to achieve the vision of the Center?

• We are conscious of the fact that our research activities do not encompass all issues that could, in principle, be pursued, given the PIs expertise and interests

• Question: Are there pressing research questions pertinent to the Center’s mission that we must address over the next two years?


Questions for theIndustrial Advisory Board

• Our experimental work contributes to the better understanding of the mechanisms responsible for MEMS performance degradation– In addition to improved models, this understanding maps onto

opportunities for improved designs, better manufacturing practices, and even new MEMS-enabled devices

Question: How do we motivate industry input toward the development of new IP?

• Our long-term success is critically dependent on our ability to engage more EDA companies in our Center’s model development activities Question: How can our industry members help us with establishing strong working relationships with EDA Companies?

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