Fundamentals ofMICROFABRICATIONThe Science of Miniaturization

Second Edition
Marc J. MadouCRC PRESS
Boca Raton London New York Washington, D.C,

Table of Contents
Chapter 1
Lithography
Introduction
Historical Note: Lithography's Origins
Photolithography Overview
Introduction
Masks
Spinning Resist and Soft Baking
Exposure and Postexposure Treatment
Development
De-scumming and Postbaking'.'.
Resists
Wafer Priming
Wafer Cleaning and Contaminants: The Clean Room
Resist Stripping
Critical Dimension, Overall Resolution, Line Width
Lithographie Sensitivity and Intrinsic Resist Sensitivity (Photochemical Quantum Efficiency)
Lithographie Sensitivity
Intrinsic Sensitivity ofa Resist (Photochemical Quantum Efficiency)
Resist Profiles
Overview of Profile Types
Lift-Off Profile
Contrast and Experimental Determination of Lithographie Sensitivity
Resolution in Photolithography
Introduction,Resolution in Contact and Proximity Printing (Shadow Printing)
Projection Printing
Planarization
Photolithography Resolution Enhancement TechnologyIntroduction
Strategies for Improved Resolution through Improved Resist Performance
Strategies for Improved Resolution through Improved Mask Technology
Beyond Moore's Law
Introduction
Moore's Law
Kurzweil
Next-Generation Lithographies
Introduction
Extreme Ultraviolet Lithography
X-Ray Lithography
Charged-Particle-Beam Lithography
Emerging Lithography Technologies
Introduction
Scanning Probe Lithography
Very Thin Resist Layers
Soft Lithography
3D Lithography Methods
Examples
1.1 Protein Patterning
1.2 Inclined LIGA Walls
1.3 PDMS-Based CDs

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Problems
References

Chapter 2
Pattern Transfer with Dry Etching Techniques
Introduction
Dry Etching: Definitionsand Jargon
Plasmas or Discharges
PhysicsofDC Plasmas
Spatial Zones in the Glow Discharge
Paschen's Law
PhysicsofRF Plasmas
Physical Etching: Ion Etching or Sputtering and Ion-Beam Milling
Introduction
Sputtering or Ion Etching
Ion-Beam Etching or Ion-Beam Milling.'.
Etching Profiles in Physical Etching
Plasma Etching (Radical Etching)Introduction
Reactor Configurations
Reaction Mechanism
Loading Effects—Uniformity and Nonuniformity
Atmospheric Downstream Plasma Etching or Plasma Jet Etching
Ion Energy vs. Pressure Relationship in a Plasma
Physical/Chemical Etching
Introduction
Energy-Driven Anisotropy
Inhibitor-Driven Anisotropy
Dopant-Driven Anisotropy
Gas Compositions in Dry Etching
Simplifying Rules
Deep Reactive Ion Etching (DRIE)
Introduction
New Plasma Sources
Common Problems Associated with DRIE
Vapor-Phase Etching without Plasma (XeF2)
Dry Etching Models—In Situ Monitoring
Comparing Wet and Dry Etching
Examples2.1 Via Etching in Si
2.2 Single-Crystal Reactive Etching and Metallization (SCREAM)
2.3 Post-CMOS Processing for High-Aspect-Ratio Integrated Silicon Microstructures
2.4 Dry Etching of Polymeric Materials
2.5 Combination Wet and Dry Etching
Problems
ReferencesChapter 3
Pattern Transfer with Additive Techniques
Introduction
Silicon Growth
Doping ofSi
Introduction
Conductivity of Semiconductors
Si Doping by Diffusion

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Doping by Implantation
Oxidation of Silicon
Kinetics
Orientation Dependence of Oxidation Kinetics
Properties of Thermal SiO2
Physical Vapor Deposition
Introduction
Thermal Evaporation
Sputtering
Molecular Beam Epitaxy
Laser Sputter Deposition or Ablation Deposition
IonPlating
Cluster Beam Technology
Chemical Vapor Deposition
Introduction
Reaction Mechanisms,.
Step Coverage
Energy Sources for CVD Processes
Overview ofCVD ProcessTypes
Epitaxy
CVDEquipment
Silk-Screening or Screen Printing
Introduction
Howlt Works
Typesof Inks
Sol-Gel Deposition TechniqueDoctor's Bladeor Tape Casting
Plasma Spraying
Introduction
Howlt Works
Deposition and Arraying Methods of Organie Layers in BIOMEMS
Introduction
Deposition Methods for Organie Materials
Patterningof Organie Materials
Thin vs. Thick Film Deposition
Selection Criteria for Deposition Method
Examples:3.1 Spray Pyrolysis
3.2 Plasma-Beam Deposition
3.3 Proposed Scenario for Continuous Manufacture of Polymer/Metal Based Biosensors—Beyond Batch
Problems.'.
References

Chapter 4
Wet Bulk Micromachining
Introduction
Historical Note
Silicon Crystallography
Introduction
Miller Indices
Crystal Structure of Silicon
Geometrie Relationships between Some Important Planes in the Silicon Lattice
Silicon as Substrate
Silicon as a Mechanical Element in MEMS
Introduction
Stress-Strain Curve and Elasticity Constants

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Residual Stress in Si
Yield, Tensile Strength, Hardness, and Creep
Piezoresistivity in Silicon
Bending of Thin Si Piates
Silicon as a Mechanical MEMS Material: Summary
Other Si Sensor Properties
Thermal Properties of Silicon
Silicon Optical Properties
Wet Isotropie and Anisotropie Etching
Introduction
Isotropie Etching
Anisotropie Etching
Chemical Etching Models
Etching with Bias and/or Illumination of the Semiconductor
Introduction
Electropolishing and Microporous Silicon
Etch-Stop Techniques
Introduction
Boron Etch Stop
Electrochemical Etch Stop
Photo-Assisted Electrochemical Etch Stop (for n-Type Silicon)
Photo-Induced Preferential Anodization (for p-Type Silicon)
Etch Stop at Thin Insoluble Films
Issues in Wet Bulk Micromachining
Introduction
Extensive Real Estate Consumption
Corner Compensation
Computer Simulation Software
Examples4.1 Dissolved Wafer Process
4.2 An Electrochemical Sensor Array Measuring pH, CO2, and O2 in a Dual Lumen Catheter
4.3 Disposable Electrochemical Valves
4.4 Self-Aligned Vertical Mirrors and V-Grooves for a Magnetic Micro-Optical Matrix Switch
Problems
References

Chapter 5Surface Micromachining
IntroductionHistoricarNote
Mechanical Properties of Thin Films
Introduction
AdhesionStress in Thin Films
Stress-Measuring Techniques
Strength of Thin Films
Surface Micromachining Processes
Basic Process Sequence
Fabrication Step Details
Controlof Film Stress
Dimensional Uncertainties
Sealing Processes in Surface Micromachining
IC Compatibility
Poly-Si Surface Micromachining Modifications
Porous Poly-Si
Hinged Polysilicon

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Thick PolysiliconMilli-Scale Molded Polysilicon Structures
Surface Micromachining Modifications Not Involving Polysilicon
SOI Surface Micromachining
Resists as Structural Elements and Molds in Surface Micromachining
Comparison of Bulk Micromachining with Surface Micromachining
Materials Case Studies
Introduction
Polysilicon Deposition and Material Structure
Amorphous and Hydrogenated Amorphous Silicon
Silicon Nitride
CVD Silicon Dioxides
Metals in Surface Micromachining
Polycrystalline Diamond and SiC Films
GaAs
Examples,.
5.1 Analog Devices Accelerometer
5.2 TI Micromirrors
5.3 Design of SOI-Based High-Sensitivity Piezoresistive Cantilevers for Label-Less Sensing
Problems
References

Chapter 6
LIGA and Micromolding
Introduction
LIGA—Background
History
Synchrotron Orbital Radiation (SOR)
Access to the Technology
LIGA and LIGA-Like Process Steps
X-RayMasks
ChoiceofPrimary Substrate
Resist Requirements
Methods of Resist Application
Exposure
Development
Comparison of Master Micromold Fabrication Methods
Metal Deposition
Molding
Demolding
Sacrificial Layers
Alternative Materials in LIGA
Examples
6.1 Electromagnetic Micromotor
6.2 LIGA Spinneret Nozzles
6.3 LIGA Fiber-Chip Coupling
Problems
References325-.<•Chapter 7A Comparison of Miniaturization Techniques: Top-Down andBottom-Up Manufacturing
Introduction
Absolute and Relative Tolerance in Manufacturing
Historical Note: Human Manufacturing

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SectionI: Top-Down Manufacturing Methods
Introduction
Chemical Microfabrication
Electrochemical Machining
Wet vs. Dry Microfabrication
Electrothermal Processes
Mechanical Processes
Comparison of Top-Down Micromachining Techniques
Sectionll: Bottom-Up Approaches
Introduction
Nature's Engineering Feats
How to Apply Nature's Tools—Merging of Biotechnology with Nanofabrication
Examples
7.1 An Electrochemical Immunosensor
7.2 An Optical Immunosensor
Problemsv
References

Chapter 8
Modeling, Brains, Packaging, Sample Preparation, andSubstrate Choice
Introduction
Modeling
Introduction
Finite Element Analysis
CADforMEMS
FutureofCADforMEMS
Brains in MEMS
Introduction
State ofthe Art in Computer Development
Brains in Nature
Artificial Intelligence
Packaging
Introduction
Packaging in Integrated Circuits vs. in Mechanical Micromachines
Dicing...,Cavity Sealing and Bonding
Higher Levels of Packaging—L2 to L5
Stress Isolation and Thermal Management
Multichip Packaging
Connections between Layers (Vias)
Partitioning
Micro and Nano Assembly
Biocompatibility
Sample Preparation in Molecular Diagnostics
Introduction
Types of Samples
Sample Preparation Protocols for Integrated DNA Analysis Devices
Substrate Choice
Introduction
QuartzMEMS
Micromachining and Surface Microstructuring of Ceramics
Polyimide MEMS
Examples
8.1 Packaging of a Variable Entrance Slit for a Spectrophotometer
8.2 A Miniature Surface Plasmon Resonance (SPR) Sensor—Spreeta™

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References

Chapter 9
Scaling, Actuators, and Power in Miniaturized Systems
Introduction
Scaling
Introduction
Micro Intuition and Nature as a Guide
Scaling of Length, Surface Area, and Volume
Scaling in Flyingand Swimming.
Scaling and Surface Tension
Scaling and Diffusion
Scaling of Minimal Analytical Sample Size
Scaling in Electrochemistry».
Scaling in Optics
Scaling of Strength-to-Weight Ratio and Inertia
Fundamental Frequency and Quality Factor
Muscle, Flagellum, and Protein Motors
Trimmer's Vertical Bracket Notation
Actuators
Introduction
Electric Actuators
Magnetic Actuators
Fluidics
Introduction
Macroseale Laws for Fluid Flow
BreakdownofFlowContinuum
Capillary Forces
Thermal Actuators
Introduction
Macroseale Laws in Heat Conduction
Breakdown of Continuum in Heat Transfer
Example Thermal Actuators
Scaling in Analytical Separation Equipment
Introduction
Commonly Used Terms in Separation ChemistryBand Broadening in the Column
Other Band-Broadening Effects
Other Actuators
Power in MEMS
Introduction
MEMS Batteries and Capacitors
Beam Energy to the MEMS
Heat-Powered MEMS
Kinetic Energy Driven MEMS
Combustion Engines in MEMS
Examples
9.1 The Bead Array Counter (BARC)
9.2 The Nanogen Chip
9.3 Field Ionization Sources
Problems
References

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Chapter 10
Miniaturization ApplicationsIntroduction
Defmitions and Classification Method
Introduction
Definitions
Classification Method
DecisionTreeSpecifications
Scaling CharacteristicsofMicromechanisms
Checklist„
Overall Market for Micromachines
Introduction
Why Use Miniaturization Technology?
From Perception to Realization>v
Overall MEMS Market Size
MEMS Market Characteristics
MEMS in the Automotive Market
Introduction
Pressure
Accelerometers
Angular Rate Sensors and Gyroscopes
Conclusions
MEMS in Medical and Biomedical Markets
Introduction
Market Character
In Vitro Diagnostics
In Vivo MEMS Applications
Miniaturization in Biomedical Instruments
Environmental Monitoring
Introduction
MEMS and Solid State Gas Sensors and Solid State Gas Sensor Arrays
Electrochemical Gas Sensors
Optochemical Gas Sensor
Instrumentation..v
Industrial/Automation
Introduction
ISFETsMicrohygrometer
Valves
IT/Peripheral
Introduction
Memory Read/Write Devices
Ink-Jet Cartridges
Other MEMS IT Applications
Telecommunications
Introduction
Optical Communications
Wireless Communications
Problems
References

Appendix A
Metrology Techniques for MEMS

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Appendix B
Living Book

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Appendix C
Si and SiO2 Etch Rates in KOH

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Appendix DGenetics

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The 20 Amino Acids Found in Biological Systems
The Genetic CodeAppendix E
Suggested Further Reading
Books on Top-Down and Bottom-Up Miniaturization
Journals and Periodicals on Micromachining and Sensors
Series on Micromachining and Sensors
Market Studies on Micromachining and Sensors
Important Proceedings/Conferences on Micromachining and Sensors:
Hilton Head Conferences
MEMS
Chemical Sensors
International Conference on Solid-State Sensors and Actuators (Transducers)
International Society for Optical Engineers (SPIE)
MicroTotalAnalysis Systems (uTAS)
NanotechEurosensors
Commercial Conference planners
Knowledge Foundation
BBCCHI

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Appendix F
MEMS Companies

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Appendix G
Glossary

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Index

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