Electronically-probed Measurements of MEMS Geometries (2000)
Raj K. Gupta,
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,
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.
- "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,
- "Material Property Measurements of Micromechanical Polysilicon Beams",
SPIE Micromachining & Microfabrication Conference,
Austin, TX, October 1996.
- "Pull-in Dynamics of Electrostatically-Actuated Beams",
Solid-State Sensor and Actuator Workshop, Late News Session,
Hilton Head, SC, June 1996.
- "Monitoring Plasma Over-etching of Wafer-bonded Microstructures",
Proceedings of Transducers, I, Stockholm, June 1995.
- "A Noise Study of a High-Tc Josephson Junction under
Near-millimeter-wave Irradiation", Applied Physics Letters,
64, February 14, 1994.
- "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.