Modeling and Simulation Tools in MEMS DesignJoe Johnson

IntelliSense Corporation

1

OutlineIntroduction

Behavioral modeling

Virtual fabrication and cross-sectioning tools

Automated meshing and FEM-BEM solvers

MEMS/IC co-development

Summary

2

Introduction

MEMS design is highly interdisciplinary

Mechanics

Electrostatics

ElectrostaticLevitation

Squeezefilm damping

Couettedamping

Anchor Losses

(TED, Acoustic)

ContactPhysics

VIBROMOTOR DRIVE

MEMS Design Is A Collaboration Challenge…

System Architect

Test Engineer

Process Engineer

Electrical Engineer

Program Manager

Packaging Engineer

Manufacturing Engineer

The chain of pain…

Device Engineer

Behavioral modeling

Hierarchical multi-domain design

Atomic elements

Compound elements

Device elements

Transistor RLC Plate Anchor Beam Gap

-

+

Op-AmpShuttle mass Folded flexure spring Comb drive

-

+

Interface circuit Resonator

Schematic based design exploration

Mode 1: In Phase

Mode 2: Anti Phase

Band pass filter

Schematic based design exploration

Compute time: 4 hr (Full 3D) vs 30s (compact)

Band pass filter

Monte Carlo basedprocess variation analysis

Schematic to mask

Attention to detail

Stress relief curves Dimples Comb bumpers Etch compensationfeatures

Automated layout synthesis

Schematic to mesh

Automated Hexahedral Meshing of the Structure

BenefitsSave time100-1000X faster than FEA models.

Design exploration and optimizationQuickly prototype and explore multiple designs

Automated mask and mesh exportEasy transition to next stages in design cycle

Process development

Virtual process traveller

Virtual FabricationCourtesy, Prof Tim Dallas, Texas Tech

Virtual FabricationCourtesy, Prof Tim Dallas, Texas Tech

Virtual FabricationCourtesy, Prof Tim Dallas, Texas Tech

process to model

Cross-SectioningStep by step process visualization

Design Rule CheckPhysical verification

all angle support

Error navigation

Simulate composite MEMS processes

Composite processes, Shikida Mitsuhiro, J. Micromech. Microeng. 14

Combination of multi-step mask transfers, oxide and nitride layers, sacrificial layer deposition and wet etching and DRIE processes.

Validate processes in design

110 um100 min

166 um150 min

225 um200 min

56 um50 min

166.40 um139.62 min

110.93 um95.27 min

226.13 um190.44 min

56.89 um51.27 min

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The chain of pain… How do you fine tune TSV processes?

Process Engineer

Multiphysics analysis

The chain of pain…

Solid Model Creation

Analysis Model Creation

Geometry Decomposition

Meshing

Mesh Manipulation

Assign Model Parameters

Assemble Simulation Model

Run Simulation

Post Process Results

1%

5%

4%

4%

6%

6%

14%

32%

21%

8%

Packaging EngineerDevice Engineer

Courtesy: Matt Staten, Computing and Modeling Dept, Sandia National Labs

80%

How do you efficiently create MEMS + Package models?Close to 80% of the time spent in mesh creation and manipulation…

1 Click Hex Meshing…

FEM-BEM mesh

Mechanical mesh

Electrostatic mesh

FEM-BEM advantagesBest solver for each physics domainBoundary Element Method (BEM): Electrostatics, Electromagnetics Finite Element Method (FEM): Thermal, Mechanical and ElectromagneticsVolume of Flow (VoF) and Finite Volume (FV): Fluidics, Electrokinetics, Chemical Reactions

Speed and efficiency2-10X Faster than pure FEA formulation

Surface meshing vs volume meshesInternal volumes, air gaps, etc do not need to be meshedEase of meshing, no costly re-meshing during deformation

Ease of convergenceDeal with large deformations, contact and post-contact without convergence issues

MEMS+IC integration

The chain of pain…

MEMS+Package ASIC

ElectroMechanical InteractionPackaging Interaction

Thermal Interaction

?

Electrical EngineerPackaging Engineer Device Engineer

How do you compensate packaging and temperature effects?

System Model Extraction (SME)

❶ Capture total energy of relevant mode(Mechanical, Electrostatic, Dissipation)

❷ Krylov/Arnoldi methods to generate Lagrangian formulation

❸ Create Compact model for system modeling

System Model Extraction (SME)

First mode

Second mode

Third mode

Capture strain energy associated with each mode

Capture electrostatic energyassociated with each mode

Capture fluid dampingcharacteristics

Arnoldi/Krylov sub-spacereduction

N-DOF behavioral modelbased on Lagrangian

formulation

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d

dt

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HDL formulation

CompactRepresentation

HardwareDescription

HDL

Final MEMS Device design

Transistor level design(SPICE or other EDA tools)

Gate level design(Cadence/Synopsys/Mentor/Tanner etc)

Design Exploration/Optimization1

2

4

5

Final Layout(L-Edit/Virtuoso/other)

6

Reduced-order Model Extraction3

MEMS-CMOS integrationdesign flow can be based on :

√ VHDL-AMS

√ Verilog-A

√ SPICE netlist

√ Matlab/Simulink .MEX

Integrated design flow for MEMS + IC

Summary

MEMS Design is a collaboration challenge

Behavioral modeling tools assist design exploration

Virtual fabrication tools save time and money in the cleanroom

Automated meshing and FEM-BEM solvers speed up design cycle

Model extraction methods link MEMS/IC development

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