Practical Guide to RF-MEMS

Closes the gap between hardcore-theoretical and purely experimental RF-MEMS books. The book covers, from a practical viewpoint, the most critical steps that have to be taken in order to develop novel RF-MEMS device concepts. Prototypical RF-MEMS devices, both including lumped components and complex networks, are presented at the beginning of the book as reference examples, and these are then discussed from different perspectives with regard to design, simulation, packaging, testing, and post-fabrication modeling. Theoretical concepts are introduced when necessary to complement the practical hints given for all RF-MEMS development stages. * Provides researchers and engineers with invaluable practical hints on how to develop novel RF-MEMS device concepts* Covers all critical steps, dealing with design, simulation, optimization, characterization and fabrication of MEMS for radio-frequency applications* Addresses frequently disregarded issues, explicitly treating the hard to predict interplay between the three-dimensional device structure and its electromagnetic functionality* Bridges theory and experiment, fundamental concepts are introduced with the application in mind, and simulation results are validated against experimental results Appeals to the practice-oriented R&D reader: design and simulation examples are based on widely known software packages such as ANSYS and the hardware description language Verilog.

Table of Contents:
Foreword XI Preface XV 1 RF-MEMS Applications and the State of the Art 1 1.1 Introduction 1 1.2 A Brief History of MEMS and RF-MEMS from the Perspective of Technology 2 1.3 RF-MEMS Lumped Components 3 1.3.1 Variable Capacitors 4 1.3.2 Inductors 10 1.3.3 Ohmic and Capacitive Switches 12 1.4 RF-MEMS Complex Networks 20 1.4.1 Reconfigurable Impedance-Matching Networks 20 1.4.2 Reconfigurable RF Power Attenuators 23 1.4.3 Reconfigurable Phase Shifters and Delay Lines 26 1.4.4 Reconfigurable Switching Matrices 26 1.5 Modeling and Simulation of RF-MEMS Devices 28 1.5.1 The Finite Element Method Approach 28 1.5.2 Compact Modeling of RF-MEMS 28 1.5.3 Mixed-Domain Electromechanical Simulation Environment 30 1.6 Packaging of RF-MEMS 31 1.7 Brief Overview of Exploitation of RF-MEMS in RF Systems 33 1.8 Conclusions 38 2 The Book in Brief 41 2.1 Introduction 41 2.2 A Brief Introduction to the FBK RF-MEMS Technology 42 2.3 An RF-MEMS Series Ohmic Switch (Dev A) 44 2.4 RF-MEMS Capacitive Switches/Varactors 49 2.4.1 Design 1 (Dev B1) 49 2.4.2 Design 2 (Dev B2) 50 2.4.3 RF-MEMS Ohmic Switch with Microheaters (Dev C) 50 2.4.4 MEMS-Based Reconfigurable RF Power Attenuator (Dev D) 52 2.4.5 MEMS-Based Reconfigurable Impedance-Matching Network (Dev E) 55 2.5 Conclusions 55 3 Design 57 3.1 Introduction 57 3.2 Design Rules of the Fondazione Bruno Kessler RF-MEMS Technology 58 3.3 Design of an RF-MEMS Series Ohmic Switch (Dev A) 60 3.4 Generation of 3D Models Starting from the 2D Layout 77 3.5 Conclusions 83 4 Simulation Techniques (Commercial Tools) 85 4.1 Introduction 85 4.2 Static Coupled Electromechanical Simulation of the RF-MEMS Ohmic Switch (Dev A) in ANSYS Multiphysics(TM) 86 4.2.1 Block 1: Definition of the Geometry and Properties of the Material 88 4.2.2 Block 2: Meshing of the Structure 92 4.2.3 Block 3: Generation of the Elements for the Electromechanical Coupling 93 4.2.4 Block 4: Definition of the Mechanical Boundary Conditions 95 4.2.5 Block 5: Definition of the Simulation 97 4.2.6 Block 6: Simulation Execution 99 4.2.7 Block 7: Postprocessing and Visualization of Results 99 4.3 Modal Analysis of the RF-MEMS Capacitive Switch (Dev B2) in ANSYS Multiphysics 101 4.4 Coupled Thermoelectromechanical Simulation of the RF-MEMS Ohmic Switch with Microheaters (Dev C) in ANSYS Multiphysics 104 4.5 RF Simulation (S-parameters) of the RF-MEMS Variable Capacitor (Dev B1) in ANSYS HFSS(TM) 121 4.6 Conclusions 130 5 On-Purpose Simulation Tools 133 5.1 Introduction 133 5.2 MEMS Compact Model Library 134 5.2.1 Suspended Rigid Plate Electromechanical Transducer 134 5.2.2 Flexible Beam 140 5.2.3 Simulation Validation of a MEMS Toggle Switch 144 5.3 A Hybrid RF-MEMS/CMOS VCO 149 5.4 Excerpts of Verilog-A Code Implemented for MEMS Models 151 5.4.1 Anchor Point 152 5.4.2 Force Source 154 5.4.3 Flexible Beam 157 5.5 Conclusions 165 6 Packaging and Integration 167 6.1 Introduction 167 6.2 A WLP Solution for RF-MEMS Devices and Networks 168 6.2.1 Package Fabrication Process 169 6.2.2 Wafer-to-Wafer Bonding Solutions 173 6.3 Encapsulation of RF-MEMS Devices 177 6.3.1 The Issue of Wafer-to-Wafer Alignment 178 6.3.2 Hybrid Packaging Solutions for RF-MEMS Devices 180 6.4 Fabrication Run of Packaged Test Structures 181 6.5 Electromagnetic Characterization of the Package 185 6.5.1 Validation of the S-parameter Simulations of Packaged Test Structures 186 6.5.2 Parameterized S-parameter Simulation of Packaged Test Structures 187 6.6 Influence of Uncompressed ACA on the RF Performance of Capped MEMS Devices 191 6.7 Conclusions 194 7 Postfabrication Modeling and Simulations 195 7.1 Introduction 195 7.2 Electromechanical Simulation of an RF-MEMS Varactor (Dev B2) with Compact Models 196 7.3 RF Modeling of an RF-MEMS Varactor (Dev B2) with a Lumped Element Network 202 7.4 Electromechanical Modeling of an RF-MEMS Series Ohmic Switch (Dev A) with Compact Models 213 7.5 Electromagnetic Modeling and Simulation of an RF-MEMS Impedance-Matching Network (Dev E) for a GSM CMOS Power Amplifier 218 7.5.1 Introduction 219 7.5.2 Electromagnetic Design and Optimization of the RF-MEMS Impedance-Matching Network 219 7.5.3 Deign of a Reconfigurable Class E PA 224 7.5.4 Experimental Results for the Hybrid RF-MEMS/CMOS PA 227 7.6 Electromagnetic Simulation of an RF-MEMS Capacitive Switch (Dev B1) in ANSYS HFSS(TM) 229 7.7 Electromagnetic Simulation of a MEMS-Based Reconfigurable RF Power Attenuator (Dev D) in ANSYS HFSS 234 7.8 Conclusions 238 Appendix A Rigid Plate Electromechanical Transducer (Complete Model) 241 A.1 Introduction 241 A.2 Mechanical Model of the Rigid Plate with Four DOFs 242 A.3 Extension of the Mechanical Model of the Rigid Plate to Six DOFs 249 A.3.1 Placement of Nodes along the Edges of a Rigid Plate 253 A.4 Contact Model for Rigid Plates with Four and Six DOFs 255 A.5 Electrostatic Model of the Rigid Plate 258 A.5.1 The Four DOFs Condition 258 A.5.2 Extension to the Case of Six DOFs 262 A.5.3 Curved Electric Field Lines Model 266 A.6 Electrostatic Model of the Plate with Holes 268 A.7 Electrostatic Model of the Fringing Effect 272 A.7.1 Fringing Effect on the Vertical Faces of the Plate 278 A.8 Viscous Damping Model 281 A.8.1 Squeeze-Film Viscous Damping of the Rigid Plate with Holes 281 A.8.2 Viscous Damping Model for Lateral Movements 284 A.8.3 Effect of the Mean Free Path of GasMolecules 285 A.9 Conclusions 286 Appendix B Flexible Straight Beam (Complete Model) 287 B.1 Mechanical Model of the Flexible Beam with Two Degrees of Freedom 287 B.1.1 The Stiffness Matrix 288 B.1.2 The Mass Matrix 290 B.2 Mechanical Model of the Flexible Beam with 12 DOFs 292 B.2.1 The Stiffness Matrix for 12 DOFs 293 B.2.2 The Mass Matrix for 12 DOFs 297 B.3 Complete Mechanical Model of the Euler Beam with 12 DOFs 302 B.4 ElectrostaticModel of the Euler Beamwith 12 DOFs 304 B.4.1 Fringing Effect Model 310 B.5 Viscous Damping Model 312 B.6 Conclusions 315 References 317 Index 331

About the Author :
Jacopo Iannacci is MEMS Researcher at the Fondazione Bruno Kessler in Trento, Italy, where he focuses on compact modeling, design, optimization, integration, packaging and reliability of MEMS/RF MEMS devices and networks for sensors and telecommunication systems. He received his PhD in Information Technology from the ARCES Research Center of the University of Bologna, Italy, and afterwards worked at the HiTeC DIMES Technology Center of the Technical University of Delft, the Netherlands, on developing packaging solutions for RF-MEMS. Jacopo Iannacci authored and co-authored about 100 scientific contributions for international journals and conference proceedings as well as two books and numerous book chapters in the field of RF-MEMS technology.