Lecture 18 Mems Cad

8/6/2019 Lecture 18 Mems Cad

1/13

CAD Application to MEMS

TechnologyBruce K. Gale, University of Utah

Acknowledgment: Nora Finch, Intellisense

M. Mehregany, Case Western ReserveJohn R. Gilbert, Microcosm Technologies

Abdelkader Tayebi, Louisiana Tech

Definition of Computer Aided Designin Microsystems Technology

In MEMS technology, CAD is defined as atightly organized set of cooperating computer

programs that enable the simulation of manufacturing processes, device operationand packaged Microsystems behavior in a

continuous sequence, by a Microsystemsengineer.

Commercially Available Software Coventorware from Coventor

http://www.memcad.com

IntelliSuite from Intellisense Inc. (Corning) http://www.intellisense.com

MEMS ProCAETool from Tanner Inc. http://www.tanner.com

MEMScap from MEMScap Inc. http://www.memscap.com

SOLIDIS from ISE Inc. http://www.ise.com

MEMS CAD Motivation

Match system specifications Optimize device performance

Design package Validate fabrication process

Shorten development cycle Reduce development cost

1 2 8 T r a n s m

i t t e r s

1 2 8 R e c e i v e r s

:

:

::

MEMS micro-mirrors

Collimator Lens Arrays


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Example: IntelliSuite System

M a t e r i a l s d a t a b a s e

F a b r ic a t io n d a t a b a s e

Anis o tropic e tch simula tor

M a s k e d i t o r

Fabrication Simulation

Solid Modeling& Meshing

Performance Analysis

Thermo-electro-mechanical

P i ez o el e c t r i c E

l e c

t r o m a g n e

t i c

Thermal-fluid-structure

Model courtesy of Auburn University

Example: IntelliSuite Advantages Design for manufacturability

Fabrication database Thin-film materials engineering Virtual prototyping

Ease of use Consistent user interface Communication with existing tools

Accuracy

MEMS-specific meshing and analysis engines In-house code development Validated by in-house MEMS designers ISO certified for quality

The Design Process

All systems have some common threads totheir design Device design

Design a manufacturable component

Package design Design a practical package

System design Design the system into which the device fits.

Goal: concurrent design at these levels

MEMS CAD System Flow

Device Modeling

Device Modeling

System Modeling

System Modeling

Package Design

Package Design

ProcessDesign

ProcessDesign

Layout

Layout

ManufacturingData and QA

Structures

ManufacturingData and QA

Structures


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Types of MEMS Design

Custom Level Design New MEMS in New Process Goal: A New MEMS component

Semi-Custom Design Existing MEMS in New Process Goal: A Better MEMS component

Standard/IP

Re-Use Existing MEMS and MEMS Process Making Existing MEMS Available to IC level

Designers to Build new systems

Who Designs?

SystemArchitect

Digital

MEMS

Packaging

AnalogSystem Design

What is Top Down Design System Architect

Designs and Simulates Mixed Technology System at ahigh level

Subsystem Designers Receive subsystem target specs in Hardware Description

Language (HDL) form from SA Design and pass back HDL model of realizable subsystem Iterate with SA until realizable design is acceptable

Top Down Design Enables SA to make tradeoffs among subsystem design

teams Enables Design teams and SA to quantitatively

communicate their goals and constraints

Implementing Top Down Design Iterative design in each subsystem Implementing the

Architect to Designer Loop Behavioral Model to Layout (Design)

Layout to Behavioral Model (Verify) Enable Communication in the Design Team Interoperability (Composite CAD VHDL-AMS working

group)

System

Design

Subsystem

Design

MEMSAnalogDigital

Verificationagainst HDL

HDLSpecification


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MEMS IC Design Flow

ModelBehavior

ModelBehavior

SystemRequirements

Stimulus Response

Stimulus Response

Sub-SystemRequirements

Layout 3D PhysicsModel

ModelExtraction

Top-downDesign

Bottom-upVerification

Cornering the Design Space

Simulated von Mises stressin Analog Devices ADXL76Simulated von Mises stressin Analog Devices ADXL76 -0.006

-0.004

-0.002

0

0.002

0.004

200 250 300 350 400

Central LocationBottom Location

C h a n g e

i n r e

l a t i v e

C a p a c

i t a n c e

Temperature [K]

Outline of the Task SequenceAccomplished by a CAD Tool

Layout and process

Topography simulation Boundaries, IC process results and Material

properties Mesh generation Device simulation

System-Level Simulation MEMS Control CAD

Layout and Process Resources

First Resource: The Process Description of theinterface and the driving circuitry: Can be acompished using a layout file editor (eg.

CADENCE, http://www.cadence.comor L-Edit,http://www.tanner.com)

Second Resource: The Process flow descriptionfile: Relates a processing step to each lithography mask in

the layout file Can be optimized by using the MISTIC software from

the University of Michigan(http://www.eecs.umich.edu/mistic/)


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Layout Editor Layout process

Multi-layer mask sets

Cell hierarchy Boolean operations Curved shapes

MEMS-specific features Any-angle feature creation Multi-copy by translation

or rotation

Links directly to processsimulation and meshgeneration

Compatible with GDSII &DXF

Topography Simulation

Goal: Obtain a realistic topography of theconsidered device by: Realistically representing complex 2D and 3D

structures to simulate the manufacturing process

Process Simulation

Document & validate process steps or process flows

Model creation directlyfrom fabrication process

Link process & designto reduce prototype runs

Process database MEMS process steps Standard foundry templates

Expandable for customsteps or templates

Model courtesy of the University of Windsor SEM courtesy of IME Singapore

Anisotropic Etch Simulation(AnisE)

Etch rate databases Single & double sided

etching Multiple etch stops Real time etch visualization 3D geometry visualization Direct measurements of

etch depths and featuresizes

Study process deviationsAbove: Examples of corner compensation

Below: Rounded edge after 1 hour (left) and 5 hours (right)

Lower models courtesy of OptIC


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Virtual Prototyping

Validate process Verify mask set View 3D geometry after each process step

Surface micromachining simulation

Anisotropic etch simulation

Model (left) courtesy of Tennessee Technological University

Boundaries, IC Process Resultsand Material Properties

Description of the material interface

boundary Dopant Distribution within each layer of the

device Distribution of residual stresses Optimization of the Material Properties (eg.

MEMCAD from Microcosm Inc.)

Thin-film Material Expertise Accurate material property

estimation for deviceanalysis

Provide insight intomaterial behavior Expandable for custom

materials or processes Reduce number of

materials characterizationfabrication runs

Increase device performance Improve yields

Youngs Modulus variation in deposited layer due to processtemperature and film thickness

Mesh Operations

Generate a computational mesh for devicesimulation by either using boundary

element methods or finite element methodsor coupling of both


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Automatic Mesh Generation

From fabrication simulation 3D model based on mask set and process sequence

Material properties transferred to analysis

Import or export ANSYS, ABAQUS, PATRAN models

Models courtesy of the University of Windsor (left), Raytheon (center),and Tennessee Technological University(right)

Interactive Mesh Refinement

Mesh optimization provides faster simulation times 100% Automated or 100% user-driven Local or global

Mesh optimization results in greater accuracy Independent refinement of electrostatic & mechanical

meshes

Model (right) courtesy of DSI, Singapore

Device Simulation

Compute the coupled response of a MEMSdevice using numerical methods

Also provide many coupling effect thatMEMS rely on (eg. electromechanical,thermomechanical, optoelectrical, andoptomechanical coupling behaviors)

Extract behavioral models for system-levelsimulation.

Modeling of All Contributing Factors Process induced effects

Deformation Stiffening

Micro-assembly &

post-contact behavior Coupled dynamic analysis

Frequency vs. voltage bias RF switching time

Macro-model extraction Electrostatic force vs.

Displacement characterization Coupled boundary element &

finite element analysis

Large & small displacement theory 3D static & dynamic analysis

Model courtesy of Auburn University


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3D Device Modeling Structural Mechanics (including contact) Electrostatics & Capacitance Extraction

Thermo-mechanics Coupled Electro-Thermo-Mechanics (including contact) Thermal Flow Analysis Piezoresistive Devices Electro-Thermal Devices CFD for Compressible and Incompressible Flow

Electrokinetics and Chemical Transport in Liquids Inductance (RL) and RL-Thermo-Mechanics Damping of complex structures Electrokinetic Switching

for Chemical Transport

Coupling Effects

A. K. Noor and S. L Venneri, bulletin for the international association for computationalmechanics, n o6, summer 1998

System-Level Simulation

Conversion of a numerical matrix to anequivalent subcircuit

Translate specific changes in deviceconfiguration, dimensions, and material

properties into the circuit-equivalent behavioral model

XL76 Layout ProcessFlow

MemBuilder 3-D

SolidModel

Device to System

92.00

92.50

93.00

93.50

94.00

94.50

95.00

0 0.5 1 1.5 2 2.5 3 3.5Time (ms)

S e n s o r

F i n g e r

C a p a c

i t a n c e

( f F )

Cross-axissensitivity

SystemPerformance

System Model


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System Modeling

y posi tio n_o ut

vi n

vbia s

zposi tio n_m as s

z positi on _ ma ss

y pos iti on_ mass

k: 0.6 5 pos1

pos2

mas s

m: 2e- 10

pos

ma ss

m:2 e- 10

pos

d:. 57e- 6

pos1

pos2

d: .23 u

pos1

pos2

v

50

100Meg

vout

v

50

CLK

v initial:0 pulse:30 period:50mtr:.1utf :.1u

y

z

pos itio n

120 u

pos1

pos2

die le ct ri c2d_ mic ro c

delt a0:6 0u

zpos1

e1 e2

ypos2y pos1

zpos2

die le ct ri c2d_ mic ro c

del ta 0: 60u

zpos1

e1e2

y pos2 yp os1

z pos2

k:0 .325

delta 0:3 0u

pos1

pos2

k: 0. 325

delt a0: 30u

pos1

pos2

posi ti on

90u

pos1

pos2

posi ti on

30u

pos1

pos2

60

0.00

0.50

1.00

1.50

2.00

2.50

3.00

0 0.5 1 1.5 2 2.5Time (ms)

Demodulator Outpu

t(V)

92.00

92.50

93.00

93.50

94.00

94.50

95.00

0 0.5 1 1.5 2 2.5 3 3.5Time (ms)

S e n s o r

F i n g e r

C a p a c

i t a n c e

( f F )

Cross AxisSensitivity

-60

-40

-20

0

20

40

60

0 0 .5 1 1 .5 2 2.5 3 3.5Time (ms)

A c c e

l e r a t

i o n

( g ' s )

Demodulator Output

Input Acceleration

Sensor HDL Model

HDL (Macromodel) Generationfrom Device Modeling

Extract from 3D model: Auto Fit of Behavior Curves

Mechanical Spring Electrostatic Forces Mass Damping Coefficients

Auto generation of 6-DOFHDL Model

Industry standardsystem/circuit modelingtools: SABER, SPICE,Matlab, etc.

ADXL76 finger-cell 3D model

Capacitancecharacterization

Effect Of 10% Tether MisalignmentOn Response

Effect Of A +/- 10% Variation Of Tether Spring Constants


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Packaging Simulation

Automated package-device interactionsimulation by: Separating FEA of both the package and the

device Coupling the results through parametric

behavioral package models (MEMCAD fromMicrocosm Inc.

Package to Device

Device

Package

Coupled Packageand Device Effects

Compact

Package

Model

Package Model Calibration

m

Metal foil strain gaugesMetal foil strain gauges

Displacement along the sensitiveaxis of the resistor element

Displacement along the sensitiveaxis of the resistor element

Potential distribution in the metal foilPotential distribution in the metal foil

Silicon die,wirebonds,

and leadframeof plasticpackage

Silicon die,wirebonds,

and leadframeof plasticpackage

Packaging Sensitivity Analysis

Temperature BC

Package MechanicalAnalysis

Displacement

Extraction

MEMCAD

- 0 . 0 0 6

- 0 . 0 0 4

- 0 . 0 0 2

0

0 . 0 0 2

0 . 0 0 4

2 0 0 2 5 0 3 0 0 3 5 0 4 0 0

C e n t r a l L o c a t i o nB o t t o m L o c a t i o n

C h a n g e

i n r e

l a t i v e

C a p a c i

t a n c e

T e m p e r a t u r e [K ]

Device Mechanical /Electrical Analysis


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Summary

MEMS/MST tools exist today. The Tools can support the design of RF devices

and systems. The Design Process needs to support the

integration of MEMS and ASIC subsystems. ALL players in the design process (Architect,

Analog, Digital, MEMS, Package) mustcommunicate.

Communications are enabled by specific layers inthe design tool set which allow models from onesubsystem to influence the others.

IntelliSuite ApplicationExamples

Raytheon Systems

RF switch Corrugated geometry contact analysis Electrostatically actuated

CAD

Fabricated device SEM

Von Mises Stress

Device model

NASA

Radiation detectors

CAD stress results Fabricated array


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Ford Microelectronics, Inc.

Capacitive pressuresensor Capacitance as a function

of applied pressure

Comparison between IntelliSuite simulation andFords experimental results

3

3.2

3.4

3.6

3.8

4

4.2

4.4

0 50 100 150

Differential Pressure (PSI)

Ford Experimental Data

IntelliSuite Simulation Data

D e v i c e

C a p a c

i t a n c e

( p F )

*Ford Microelectronics, Inc. Colorado Springs, CO,JMEMS , June96, p 98

Gyro / Accelerometer

Natural frequency shift Electrostatic or thermal frequency tuning Only 3D simulation available Accounts for levitation & other 2nd order

effects

Voltage (V)

N o r m .

F r e q u e n c y

( 4 8 8 5 4

. 3 H z )

Natural Frequency vs. Voltage

Corning IntelliSense

Mirror array packaging analysis

IntelliSense Packaging Group

Integrate With System-level Design

Electro-mechanical outputas input to optical model 3D mirror profile

Maximum mirror angle Jitter angle associated with

mirror stability Surface material

Micro-mirror radius vs.fraction of geometric encircledenergy in an 8 micron diameter

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

-6000 -4000 -2000 0 2000 4000 6000

Radius of micro-mirror (mm)

F r a c

t i o n o

f g e o m e

t r i c

e n c

i r c

l e d e n e r g y

i n a n

8 m

i c r o n

d i a m e

t e r

Rangeofsilicon wafer naturalradius

Range ofsiliconwafer naturalradius

Model courtesy of NASA, Goddard Space Flight Center


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Fluidic analysis overview

3D Navier-Stokes solution Incompressible, laminar,

single-phase flow Heat transfer Steady-state and transient Squeeze-film damping Electro-kinetic phenomena

Electro-osmosis Electro-phoresis

Finite element & finitevolume solvers

Electrophoresis channels

Clockwise from top: AnisE simulation of channels,velocity vectors, flow profile

Electro-osmosis

Pressure Plot Vector Plot

Injection Port10 V

0 V

Ambient Pressure at all Ports

5 V

5 V

Ref.: Patankar and Hu; Analytical Chemistry, Vol. 70, No. 9, May 1, 1998

Cross-channel fluid flow Cross-channel fluid flow

Lecture 18 Mems Cad

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