Electronically-probed Measurements of MEMS Geometries (2000)
Raj K. Gupta, Downloadable pdf

Abstract:
Measurement of microelectromechanical systems (MEMS) geometry is critical for device design and simulation, for material property extraction, and for post-fabrication trimming. In this paper, electrostatically-driven laterally resonant comb-drive test structures with prescribed changes in spring width are used to ascertain systematic variations in process offsets (edge biases) and sidewall angles. The technique is both in-situ and non-destructive. An analytical model for the resonant frequency, tuned with three-dimensional (3D) simulations using MEMCAD, includes effects of a distributed mass, residual stress, and compliant supports.

Pull-in Time Dynamics as a Measure of Absolute Pressure (1997)
Raj K. Gupta and Stephen D. Senturia, Downloadable pdf

Abstract:
The squeezed-film damping component of the pull-in time of an electrostatically-actuated micromechanical fixed-fixed beam is shown to be a sensitive, and nearly linear function of ambient air pressure in the measured range of 0.1 mbar to 1013 mbar (1 atm or 760 Torr). The data and simulations show that pull-in type devices will enable MEMS sensors for broad-range absolute pressure measurements, and for in-situ leak monitoring of hermetically sealed packages containing other sensors or IC´s. The sensors are compatible with any MEMS fabrication processes that allow out-of-plane electrostatic actuation, including surface micromachining and silicon wafer-bonding, and they do not require a cavity sealed at vacuum or at a reference air pressure.

Additional co-authored research publications:

  • "Electrostatic Pull-in Test Structure Design for in-situ Mechanical Property Measurements of Microelectromechanical Systems (MEMS)", MIT, 1997.
    Downloadable pdf  
  • "The Effect of Release-Etch Holes on the Electromechanical Behavior of MEMS Structures", Transducers 1997, Chicago, IL.  
  • "An Approach to Macromodeling of MEMS for Nonlinear Dynamic Simulation", ASME Congress and Exposition, Atlanta, GA, November 1996.  
  • "Material Property Measurements of Micromechanical Polysilicon Beams", SPIE Micromachining & Microfabrication Conference, Austin, TX, October 1996.
    Downloadable pdf  
  • "Pull-in Dynamics of Electrostatically-Actuated Beams", Solid-State Sensor and Actuator Workshop, Late News Session, Hilton Head, SC, June 1996. Downloadable pdf  
  • "Monitoring Plasma Over-etching of Wafer-bonded Microstructures", Proceedings of Transducers, I, Stockholm, June 1995.
    Downloadable pdf  
  • "A Noise Study of a High-Tc Josephson Junction under Near-millimeter-wave Irradiation", Applied Physics Letters, 64, February 14, 1994.
    Downloadable pdf  
  • "A Protease-sensitive Site in the Proposed Ca2+-Binding Region of Human Serum Amyloid P component and other Pentraxins", Protein Science, 1, 1992.  
  • "Metastable Defect States and Equilibrium Temperatures in a-SiNX:H, a-SiOX:H, and a-SiCX:H", Journal of Non-Crystalline Solids, 137 & 138, 1991.