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

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

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.