High-Fidelity and Behavioral Simulation of Air Damping in MEMS

The paper presents simulations of air damping in MEMS, including squeeze-film and viscous dissipation, using different level models: 3D numerical solution of Navier-Stokes equations (using CFD-ACE from CFDRC), and circuit/behavioral model (in SPICE and Saber/MAST formats). Results of the squeeze film compact model, based on an equivalent circuit, agree very well with the 3D results even for very large amplitudes of plate motion (up to 90% of the nominal gap), accompanied by significant changes of pressure (up to 15 times bigger than the static ambient pressure). All previous squeeze film simulations published by other authors were limited to small amplitudes and small pressure changes only. To derive behavioral models for torsional micromirrors, comb-drive resonators, and moving plates with holes, a comprehensive analysis of shear and squeeze forces acting on moving MEMS elements has been performed.

[1]  S. Mukherjee,et al.  Squeeze film damping effect on the dynamic response of a MEMS torsion mirror , 1998 .

[2]  W. E. Langlois.  Isothermal squeeze films , 1961 .

[3]  R. Howe,et al.  Viscous damping model for laterally oscillating microstructures , 1994 .

[4]  William C. Tang,et al.  Viscous air damping in laterally driven microresonators , 1994, Proceedings IEEE Micro Electro Mechanical Systems An Investigation of Micro Structures, Sensors, Actuators, Machines and Robotic Systems.

[5]  R. Muller,et al.  Solid-State Sensor and Actuator Workshop Held in Hilton Head Island, South Carolina on 4-7 June 1990 , 1990 .

[6]  Gary K. Fedder,et al.  Hierarchical Representation and Simulation of Micromachined Inertial Sensors , 1998 .

[7]  Tamal Mukherjee,et al.  Multi-Mode Sensitive Layout Synthesis of Microresonators , 1998 .

[8]  W. Dotzel,et al.  Simulation of gas damping in microstructures with nontrivial geometries , 1998, Proceedings MEMS 98. IEEE. Eleventh Annual International Workshop on Micro Electro Mechanical Systems. An Investigation of Micro Structures, Sensors, Actuators, Machines and Systems (Cat. No.98CH36176.

[9]  T. Veijola,et al.  Equivalent-circuit model of the squeezed gas film in a silicon accelerometer , 1995 .

[10]  A. J. Przekwas,et al.  A FINITE-VOLUME METHOD FOR FLUID FLOW SIMULATIONS WITH MOVING BOUNDARIES , 1994 .