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Table of Contents
Front Cover
Handbook of Silicon Based MEMS Materials and Technologies
Copyright Page
Contents
List of contributors
Preface
Where is silicon based MEMS heading to?
References
I. Silicon as MEMS Material
1 Properties of silicon
1.1 Properties of silicon
1.1.1 Crystallography of silicon
1.1.1.1 Miller index (hkl) system
1.1.1.2 Stereographic projection
1.1.2 Defects in silicon lattice
1.1.3 Mechanical properties of silicon
1.1.4 Electrical properties
1.1.4.1 Introduction-dopants and impurities in silicon
1.1.4.2 Piezoresistive effect in silicon
General piezoresistive effect
Strain
Stress in anisotropic materials
Strain effect on resistivity
Linearity
Effect of temperature and doping
Example of a piezoresistive sensor design
Surface effects
References
2 Czochralski growth of silicon crystals
2.1 The Czochralski crystal-growing furnace
2.1.1 Crucible
2.1.2 Hot zone materials
2.1.3 Hot zone structure
2.1.4 Gas flow
2.2 Stages of growth process
2.2.1 Melting
2.2.2 Neck
2.2.3 Crown
2.2.4 Body
2.2.5 Tail
2.2.6 Shut-off
2.3 Selected issues of crystal growth
2.3.1 Diameter control
2.3.2 Doping
2.3.3 Hot zone lifetime
2.4 Improved thermal and gas-flow designs
2.5 Heat transfer
2.6 Melt convection
2.6.1 Free convection
2.6.2 Crucible rotation
2.6.3 Crystal rotation
2.6.4 Marangoni convection and gas shear
2.7 Magnetic fields
2.7.1 Cusp field
2.7.2 Transverse field
2.7.3 Melt flows under transverse field
2.7.4 Time-dependent fields
2.8 Hot recharging and continuous feed
2.8.1 Hot recharging
2.8.2 Charge topping
2.8.3 Crucible modifications
2.8.4 Continuous Czochralski growth
2.9 Heavily n-type doped silicon and constitutional supercooling
2.9.1 Constitutional supercooling.
2.9.2 Melting-point depression
2.9.3 Origin of dopant gradient in the melt
2.9.4 Path to lower resistivity
2.10 Growth of large diameter crystals
2.10.1 Neck growth for large crystals
2.10.2 Neck extension
2.10.3 Additional stresses on neck
2.10.4 Dislocations oriented in &
lang
100&
rang
direction in large diameter crystals
2.10.5 Crucible wall temperature
2.10.6 Double-layered crucible structure
2.10.7 Crucible deformations
2.10.8 Intentional devitrification
2.10.9 Transverse or cusp field for very large crystals
2.10.10 Boosting crystal weight
2.10.11 Seed chuck
2.10.12 Additional challenges
References
Further reading
3 Properties of silicon crystals
3.1 Dopants and impurities
3.2 Typical impurity concentrations
3.3 Concentration of dopants and impurities in axial direction
3.4 Resistivity
3.5 Radial variation of impurities and resistivity
3.6 Thermal donors
3.7 Defects in silicon crystals
3.8 Control of vacancies, interstitials, and the oxidation-induced stacking fault ring
3.9 Oxygen precipitation
3.9.1 Oxygen precipitation and its quality effects
3.9.2 Dependence of precipitation on oxygen level and annealing process
3.9.3 Bulk microdefects
3.9.4 Oxygen precipitation in highly doped wafers
3.9.5 Effect of precipitation on lifetime and oxidation-induced stacking faults
3.10 Conclusion
Acknowledgments
References
4 Silicon wafers preparation and properties
4.1 Silicon wafer manufacturing process
4.1.1 Ingot cutting and shaping
4.1.2 Wafering
4.1.2.1 ID cutting
4.1.2.2 Wire cutting
4.1.3 Wafer marking
4.1.4 Edge grinding
4.1.5 Lapping/grinding
4.1.6 Chemical etching
4.1.6.1 Donor killing
4.1.7 Polishing
4.1.8 Clean room operations
4.2 Standard measurements of polished wafers.
4.2.1 Oxygen and carbon concentration
4.2.2 Metal concentration measurements
4.2.3 Resistivity
4.2.4 Wafer geometry
4.2.5 Particles
4.2.6 Other measurements
4.3 Sample specifications of microelectromechanical systems wafers
4.4 Standards of silicon wafers
References
5 Epi wafers: preparation and properties
5.1 Silicon epitaxy for MEMS
5.2 Silicon epitaxy-the basics
5.2.1 Surface preparation
5.2.2 Silicon precursors and deposition temperature
5.2.3 Choice of doping species
5.2.4 Choosing an operating pressure
5.2.5 Monitoring wafer average temperature and on-wafer thermal profile
5.3 The epi-poly process
5.4 Etch stop layers
5.4.1 Heavily boron-doped epitaxial etch stop layers
5.4.2 Pseudomorphic epitaxial SiGe etch stop layers
5.5 Epi on silicon on insulator substrates
5.6 Selective epitaxy and epitaxial layer overgrowth
5.7 Considerations for chemical mechanical polishing
5.8 Metrology
5.8.1 Measurement of Si Epi layer thickness
5.8.2 Measurement of epi layer resistivity
5.8.3 Measurement of Ge in Si and SiGe epi layer thickness
5.8.4 Defectivity measurements
5.8.5 Stress measurements
5.9 Commercially available epitaxy systems
5.9.1 Single wafer systems
5.9.2 Batch systems
5.10 Summary
References
6 Thin films on silicon
6.1 Thin films on silicon: silicon dioxide
6.1.1 Introduction
6.1.2 Growth methods of silicon dioxide
6.1.2.1 Thermal oxidation
6.1.2.1.1 Thermal oxidation processes
6.1.2.1.2 Consumption of Si during oxidation
6.1.2.1.3 Dopant effects
6.1.2.1.4 Chlorine effects
6.1.2.1.5 Pressure effects-high-pressure oxidation
6.1.2.1.6 Oxidation of polysilicon
6.1.2.1.7 Stress in silicon dioxide
6.1.2.1.8 Oxidation-induced defects in silicon
6.1.2.2 Chemical vapor deposition oxide growth methods.
6.1.2.2.1 Chemical vapor deposition oxides
6.1.2.3 Multidimensional effects
6.1.3 Structure and properties of silicon dioxides
6.1.4 Processing of silicon dioxides
6.1.4.1 Cleaning
6.1.4.2 Etching
References
6.2 Thin films on silicon: silicon nitride
6.2.1 Introduction
6.2.2 Growth of silicon nitride
6.2.2.1 Low-pressure chemical vapor deposition
6.2.2.2 Plasma enhanced chemical vapor deposition
6.2.2.3 Other methods
6.2.3 Structure and properties of silicon nitride
6.2.3.1 Stoichiometry
6.2.3.2 Stress in silicon nitride
6.2.3.2.1 Low-stress silicon nitride
6.2.4 Processing of silicon nitride
6.2.4.1 Etching
6.2.4.1.1 Wet etching
6.2.4.1.2 Dry etching
6.2.4.2 Etch mask and etch stop
6.2.4.3 Local oxidation
References
6.3 Thin films on silicon: poly-SiGe for MEMS-above-CMOS applications
6.3.1 Introduction
6.3.2 Material properties of poly-SiGe
6.3.3 Poly-SiGe microelectromechanical systems manufacturing
6.3.3.1 Poly-SiGe deposition technology
6.3.3.2 Standard manufacturing process of a poly-SiGe microelectromechanical systems
6.3.4 SiGe microelectromechanical systems demonstrators
6.3.4.1 Pressure sensors
6.3.4.2 Capacitive micromachined ultrasound transducer
6.3.4.3 Timing devices
6.3.5 Conclusion and future poly-SiGe research
References
6.4 Atomic layer deposition of thin films
6.4.1 Introduction
6.4.2 Operation principles of atomic layer deposition
6.4.3 Atomic layer deposition processes and materials
6.4.4 Molecular layer deposition
6.4.5 Characteristics of atomic layer deposition processes and films
6.4.6 Atomic layer deposition reactors
6.4.7 Summary
References
Further reading
6.5 Piezoelectric thin film materials for microelectromechanical systems
6.5.1 Introduction.
6.5.2 Short introduction to piezoelectric theory and important thin-film constants
6.7.3 AlN
6.7.3.1 Material properties
6.7.3.2 Doped AlN
6.5.3.3 Deposition methods
6.5.3.4 Process integration and application areas
6.5.4 PZT
6.5.4.1 Material composition
6.5.4.2 Choice of electrode and seeding
6.5.4.3 Deposition methods
6.5.4.3.1 Radio frequency-sputtering
6.5.4.3.2 Chemical solution deposition
6.5.4.3.3 Pulsed laser deposition
6.5.4.4 Process integration
6.5.4.5 PiezoMEMS application areas
6.5.5 Other (future?) piezoelectric materials for microelectromechanical systems
References
6.6 Black silicon
6.6.1 Introduction
6.6.2 Fabrication methods
6.6.2.1 Electrochemical etching
6.6.2.2 Stain etching
6.6.2.3 Metal-catalyzed chemical etching
6.6.2.4 Reactive ion etching
6.6.2.5 Laser treatment
6.6.3 Characteristic properties
6.6.3.1 Optical properties
6.6.3.2 Electrical properties
6.6.3.3 Superhydrophobicity
6.6.4 Applications
6.6.4.1 Solar cells and photodiodes
6.6.4.2 Biological and chemical sensors
6.6.4.3 Batteries
References
6.7 Thin films for antistiction
6.7.1 Introduction
6.7.2 Typical characterization techniques
6.7.3 Self-assembled monolayers
6.7.3.1 Organosilane self-assembled monolayers
6.7.3.2 Thiol-based self-assembled monolayers
6.7.3.3 Alkene/alkyne-based self-assembled monolayers
6.7.3.4 Carboxylic acid-based self-assembled monolayers
6.7.3.5 Phosphonic acid-based self-assembled monolayers
6.7.3.6 Other types of self-assembled monolayers
6.7.3.7 Process of fabricating self-assembled monolayers
6.7.3.7.1 Liquid-phase processes
6.7.3.7.2 Vapor-phase processes
6.7.3.7.3 Advantages/disadvantages of liquid- and vapor-phase processes
6.7.4 Ceramic coatings
6.7.5 Fluoropolymer coatings.
6.7.6 Diamond-like carbon and other carbon-based coatings.
Handbook of Silicon Based MEMS Materials and Technologies
Copyright Page
Contents
List of contributors
Preface
Where is silicon based MEMS heading to?
References
I. Silicon as MEMS Material
1 Properties of silicon
1.1 Properties of silicon
1.1.1 Crystallography of silicon
1.1.1.1 Miller index (hkl) system
1.1.1.2 Stereographic projection
1.1.2 Defects in silicon lattice
1.1.3 Mechanical properties of silicon
1.1.4 Electrical properties
1.1.4.1 Introduction-dopants and impurities in silicon
1.1.4.2 Piezoresistive effect in silicon
General piezoresistive effect
Strain
Stress in anisotropic materials
Strain effect on resistivity
Linearity
Effect of temperature and doping
Example of a piezoresistive sensor design
Surface effects
References
2 Czochralski growth of silicon crystals
2.1 The Czochralski crystal-growing furnace
2.1.1 Crucible
2.1.2 Hot zone materials
2.1.3 Hot zone structure
2.1.4 Gas flow
2.2 Stages of growth process
2.2.1 Melting
2.2.2 Neck
2.2.3 Crown
2.2.4 Body
2.2.5 Tail
2.2.6 Shut-off
2.3 Selected issues of crystal growth
2.3.1 Diameter control
2.3.2 Doping
2.3.3 Hot zone lifetime
2.4 Improved thermal and gas-flow designs
2.5 Heat transfer
2.6 Melt convection
2.6.1 Free convection
2.6.2 Crucible rotation
2.6.3 Crystal rotation
2.6.4 Marangoni convection and gas shear
2.7 Magnetic fields
2.7.1 Cusp field
2.7.2 Transverse field
2.7.3 Melt flows under transverse field
2.7.4 Time-dependent fields
2.8 Hot recharging and continuous feed
2.8.1 Hot recharging
2.8.2 Charge topping
2.8.3 Crucible modifications
2.8.4 Continuous Czochralski growth
2.9 Heavily n-type doped silicon and constitutional supercooling
2.9.1 Constitutional supercooling.
2.9.2 Melting-point depression
2.9.3 Origin of dopant gradient in the melt
2.9.4 Path to lower resistivity
2.10 Growth of large diameter crystals
2.10.1 Neck growth for large crystals
2.10.2 Neck extension
2.10.3 Additional stresses on neck
2.10.4 Dislocations oriented in &
lang
100&
rang
direction in large diameter crystals
2.10.5 Crucible wall temperature
2.10.6 Double-layered crucible structure
2.10.7 Crucible deformations
2.10.8 Intentional devitrification
2.10.9 Transverse or cusp field for very large crystals
2.10.10 Boosting crystal weight
2.10.11 Seed chuck
2.10.12 Additional challenges
References
Further reading
3 Properties of silicon crystals
3.1 Dopants and impurities
3.2 Typical impurity concentrations
3.3 Concentration of dopants and impurities in axial direction
3.4 Resistivity
3.5 Radial variation of impurities and resistivity
3.6 Thermal donors
3.7 Defects in silicon crystals
3.8 Control of vacancies, interstitials, and the oxidation-induced stacking fault ring
3.9 Oxygen precipitation
3.9.1 Oxygen precipitation and its quality effects
3.9.2 Dependence of precipitation on oxygen level and annealing process
3.9.3 Bulk microdefects
3.9.4 Oxygen precipitation in highly doped wafers
3.9.5 Effect of precipitation on lifetime and oxidation-induced stacking faults
3.10 Conclusion
Acknowledgments
References
4 Silicon wafers preparation and properties
4.1 Silicon wafer manufacturing process
4.1.1 Ingot cutting and shaping
4.1.2 Wafering
4.1.2.1 ID cutting
4.1.2.2 Wire cutting
4.1.3 Wafer marking
4.1.4 Edge grinding
4.1.5 Lapping/grinding
4.1.6 Chemical etching
4.1.6.1 Donor killing
4.1.7 Polishing
4.1.8 Clean room operations
4.2 Standard measurements of polished wafers.
4.2.1 Oxygen and carbon concentration
4.2.2 Metal concentration measurements
4.2.3 Resistivity
4.2.4 Wafer geometry
4.2.5 Particles
4.2.6 Other measurements
4.3 Sample specifications of microelectromechanical systems wafers
4.4 Standards of silicon wafers
References
5 Epi wafers: preparation and properties
5.1 Silicon epitaxy for MEMS
5.2 Silicon epitaxy-the basics
5.2.1 Surface preparation
5.2.2 Silicon precursors and deposition temperature
5.2.3 Choice of doping species
5.2.4 Choosing an operating pressure
5.2.5 Monitoring wafer average temperature and on-wafer thermal profile
5.3 The epi-poly process
5.4 Etch stop layers
5.4.1 Heavily boron-doped epitaxial etch stop layers
5.4.2 Pseudomorphic epitaxial SiGe etch stop layers
5.5 Epi on silicon on insulator substrates
5.6 Selective epitaxy and epitaxial layer overgrowth
5.7 Considerations for chemical mechanical polishing
5.8 Metrology
5.8.1 Measurement of Si Epi layer thickness
5.8.2 Measurement of epi layer resistivity
5.8.3 Measurement of Ge in Si and SiGe epi layer thickness
5.8.4 Defectivity measurements
5.8.5 Stress measurements
5.9 Commercially available epitaxy systems
5.9.1 Single wafer systems
5.9.2 Batch systems
5.10 Summary
References
6 Thin films on silicon
6.1 Thin films on silicon: silicon dioxide
6.1.1 Introduction
6.1.2 Growth methods of silicon dioxide
6.1.2.1 Thermal oxidation
6.1.2.1.1 Thermal oxidation processes
6.1.2.1.2 Consumption of Si during oxidation
6.1.2.1.3 Dopant effects
6.1.2.1.4 Chlorine effects
6.1.2.1.5 Pressure effects-high-pressure oxidation
6.1.2.1.6 Oxidation of polysilicon
6.1.2.1.7 Stress in silicon dioxide
6.1.2.1.8 Oxidation-induced defects in silicon
6.1.2.2 Chemical vapor deposition oxide growth methods.
6.1.2.2.1 Chemical vapor deposition oxides
6.1.2.3 Multidimensional effects
6.1.3 Structure and properties of silicon dioxides
6.1.4 Processing of silicon dioxides
6.1.4.1 Cleaning
6.1.4.2 Etching
References
6.2 Thin films on silicon: silicon nitride
6.2.1 Introduction
6.2.2 Growth of silicon nitride
6.2.2.1 Low-pressure chemical vapor deposition
6.2.2.2 Plasma enhanced chemical vapor deposition
6.2.2.3 Other methods
6.2.3 Structure and properties of silicon nitride
6.2.3.1 Stoichiometry
6.2.3.2 Stress in silicon nitride
6.2.3.2.1 Low-stress silicon nitride
6.2.4 Processing of silicon nitride
6.2.4.1 Etching
6.2.4.1.1 Wet etching
6.2.4.1.2 Dry etching
6.2.4.2 Etch mask and etch stop
6.2.4.3 Local oxidation
References
6.3 Thin films on silicon: poly-SiGe for MEMS-above-CMOS applications
6.3.1 Introduction
6.3.2 Material properties of poly-SiGe
6.3.3 Poly-SiGe microelectromechanical systems manufacturing
6.3.3.1 Poly-SiGe deposition technology
6.3.3.2 Standard manufacturing process of a poly-SiGe microelectromechanical systems
6.3.4 SiGe microelectromechanical systems demonstrators
6.3.4.1 Pressure sensors
6.3.4.2 Capacitive micromachined ultrasound transducer
6.3.4.3 Timing devices
6.3.5 Conclusion and future poly-SiGe research
References
6.4 Atomic layer deposition of thin films
6.4.1 Introduction
6.4.2 Operation principles of atomic layer deposition
6.4.3 Atomic layer deposition processes and materials
6.4.4 Molecular layer deposition
6.4.5 Characteristics of atomic layer deposition processes and films
6.4.6 Atomic layer deposition reactors
6.4.7 Summary
References
Further reading
6.5 Piezoelectric thin film materials for microelectromechanical systems
6.5.1 Introduction.
6.5.2 Short introduction to piezoelectric theory and important thin-film constants
6.7.3 AlN
6.7.3.1 Material properties
6.7.3.2 Doped AlN
6.5.3.3 Deposition methods
6.5.3.4 Process integration and application areas
6.5.4 PZT
6.5.4.1 Material composition
6.5.4.2 Choice of electrode and seeding
6.5.4.3 Deposition methods
6.5.4.3.1 Radio frequency-sputtering
6.5.4.3.2 Chemical solution deposition
6.5.4.3.3 Pulsed laser deposition
6.5.4.4 Process integration
6.5.4.5 PiezoMEMS application areas
6.5.5 Other (future?) piezoelectric materials for microelectromechanical systems
References
6.6 Black silicon
6.6.1 Introduction
6.6.2 Fabrication methods
6.6.2.1 Electrochemical etching
6.6.2.2 Stain etching
6.6.2.3 Metal-catalyzed chemical etching
6.6.2.4 Reactive ion etching
6.6.2.5 Laser treatment
6.6.3 Characteristic properties
6.6.3.1 Optical properties
6.6.3.2 Electrical properties
6.6.3.3 Superhydrophobicity
6.6.4 Applications
6.6.4.1 Solar cells and photodiodes
6.6.4.2 Biological and chemical sensors
6.6.4.3 Batteries
References
6.7 Thin films for antistiction
6.7.1 Introduction
6.7.2 Typical characterization techniques
6.7.3 Self-assembled monolayers
6.7.3.1 Organosilane self-assembled monolayers
6.7.3.2 Thiol-based self-assembled monolayers
6.7.3.3 Alkene/alkyne-based self-assembled monolayers
6.7.3.4 Carboxylic acid-based self-assembled monolayers
6.7.3.5 Phosphonic acid-based self-assembled monolayers
6.7.3.6 Other types of self-assembled monolayers
6.7.3.7 Process of fabricating self-assembled monolayers
6.7.3.7.1 Liquid-phase processes
6.7.3.7.2 Vapor-phase processes
6.7.3.7.3 Advantages/disadvantages of liquid- and vapor-phase processes
6.7.4 Ceramic coatings
6.7.5 Fluoropolymer coatings.
6.7.6 Diamond-like carbon and other carbon-based coatings.