Thomas M. Adams Richard A. Layton. Introductory MEMS. Fabrication and Applications. Springer

Size: px
Start display at page:

Download "Thomas M. Adams Richard A. Layton. Introductory MEMS. Fabrication and Applications. Springer"

Transcription

1 Thomas M. Adams Richard A. Layton Introductory MEMS Fabrication and Applications Springer

2 Contents Preface xiü Part I Fabrication Chapter 1: Introduction What are MEMS? Why MEMS? Low cost, redundancy and disposability Favorable scalings How are MEMS made? Roadmap and perspective 12 Essay: The Role of Surface to Volume Atoms as Magnetic Devices Miniaturize 12 Chapter 2: The substrate and adding material to it Introduction The silicon substrate Silicon growth It's a crystal Miller indices It's a semiconductor Additive technique: Oxidation Growing an oxide layer Oxidation kinetics Additive technique: Physical vapor deposition Vacuum fundamentals Thermal evaporation Sputtering Other additive techniques 57

3 viii Introductory MEMS: Fabrication and Applications Chemical vapor deposition Electrodeposition Spin casting Wafer bonding 58 Essay: Silicon Ingot Manufacturing 59 Chapter 3: Creating and transferring patterns Photolithography Introduction Keeping it clean Photoresist Positive resist Negative resist Working with resist Applying photoresist Exposure and pattern transfer Development and post-treatment Masks Resolution Resolution in contact and proximity printing Resolution in projection printing Sensitivity and resist profiles Modeling of resist profiles Photolithography resolution enhancement technology Mask alignment Permanent resists 89 Essay: Photolithography Past, Present and Future 90 Chapter 4: Creating structures Micromachining Introduction Bulk micromachining processes Wet chemical etching Dry etching Surface micromachining Surface micromachining processes Problems with surface micromachining Lift-off Process integration A surface micromachining example 115

4 Contents Designing a good MEMS process flow Last thoughts 124 Essay: Introduction to MEMS Packaging 126 Chapter 5: Solid mechanics Introduction 5.2 Fundamentals of solid mechanics Stress Strain Elasticity Special cases Non-isotropic materials Thermal strain 5.3 Properties of thin films Adhesion Stress in thin films Peel forces Part II Applications Chapter 6: Thinking about modeling What is modeling? Units The input-output concept Physical variables and notation Preface to the modeling chapters 163 Chapter 7: MEMS transducers An overview of how they work What is a transducer? Distinguishing between sensors and actuators Response characteristics of transducers Static response characteristics Dynamic performance characteristics MEMS sensors: principles of operation 178

5 x Introductory MEMS: Fabrication and Applications Resistive sensing Capacitive sensing Piezoelectric sensing Resonant sensing Thermoelectric sensing Magnetic sensing 7.5 MEMS actuators: principles of operation Capacitive actuation Piezoelectric actuation Thermo-mechanical actuation Thermo-electric cooling Magnetic actuation 7.6 Signal conditioning 7.7 A quick look at two applications RF applications Optical applications Chapter 8: Piezoresistive transducers Introduction Modeling piezoresistive transducers Bridge analysis Relating electrical resistance to mechanical strain Device case study: Piezoresistive pressure sensor 221 Chapter 9: Capacitive transducers Introduction Capacitor fundamentals Fixed-capacitance capacitor Variable-capacitance capacitor An overview of capacitive sensors and actuators Modeling a capacitive sensor Capacitive half-bridge Conditioning the signal from the half-bridge Mechanical subsystem Device case study: Capacitive accelerometer 250

6 Contents Chapter 10: Piezoelectric transducers Introduction Modeling piezoelectric materials Mechanical modeling of beams and plates Distributed parameter modeling Statics Bending in beams Bending in plates Case study: Cantilever piezoelectric actuator 276 Chapter 11: Thermal transducers Introduction Basic heat transfer Conduction Convection Radiation Case study: Hot-arm actuator Lumped element model Distributed parameter model FEA model 306 Essay: Effect of Scale on Thermal Properties 310 Chapter 12: Introduction to microfluidics Introduction Basics of fluid mechanics Viscosity and flow regimes Entrance lengths Basic equations of fluid mechanics Conservation of mass Conservation of linear momentum Conservation equations at a point: Continuity and Navier-Stokes equations Some solutions to the Navier-Stokes equations Couetteflow Poiseuille flow Electro-osmotic flow Electrostatics 340

7 xii Introductory MEMS: Fabrication and Applications Ionic double layers Navier-Stokes with a constant electric field Electrophoretic separation 357 Essay: Detection Schemes Employed in Microfluidic Devices for Chemical Analysis 362 Part III Microfabrication laboratories Chapter 13: Microfabrication laboratories Hot-arm actuator as a hands-on case study Overview of fabrication of hot-arm actuators Cleanroom safety and etiquette Experiments 377 Experiment 1: Wet oxidation of a silicon wafer 377 Experiment 2: Photolithography of sacrificial layer 384 Experiment 3: Depositing metal contacts with evaporation 388 Experiment 4: Wet chemical etching of aluminum 392 Experiment 5: Plasma ash release 395 Experiment 6: Characterization of hot-arm actuators 397 Appendix A: Notation 405 Appendix B: Periodic table of the elements 411 Appendix C: The complimentary error function 413 Appendix D: Color chart for thermally grown silicon dioxide 415 Glossary 417 Subject Index 439