Lecture 18 Mems Cad
Transcript of Lecture 18 Mems Cad
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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
:
:
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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
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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
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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