Publications

Applications of Ultrasonic Lamb Waves

Stuart Wenzel
Richard M. White
1992

Ultrasonic flexural Lamb waves in thin films have applications for sensing and actuation. We begin with a review of the Rayleigh-Lamb dispersion relation, which governs the propagation of Lamb waves in free, homogeneous, isotropic plates. We derive the dispersion relation for the lowest-order flexural (A0) mode in terms of in-plant tension, stiffness, mass per unit area and rotary inertia. A radiation-load method is used to treat viscoelastic loading. The resulting dispersion relations accurately predict sensor response -- changes of wave velocity, frequency and attenuation -- to various...

Thermal Applications of Microbridges

Carlos Mastrangelo
Richard S. Muller
1990
The thermal applications of electrically-heated polycrystalline-silicon microbridges are explored. An electrothermal model based on the balance of heat dissipation and heat losses is developed which determines the microbridge electrical characteristics. The...

Low Temperature Silicon-Silicon Bonding with Oxides

Leslie A. Field
Richard S. Muller
1988

This report describes a novel low-temperature silicon-silicon bonding process using boron glass. Using this method, silicon wafers can be sealed together at 450C. The process is extremely sensitive to phosphorus. The integration of the boron-glass bonding process with MOS processing is discussed.

Fluid-Actuated Micromachined Rotors and Gears

Leslie A. Field
Richard M. White
1991

Fluid-actuated micromechanical structure were designed and fabricated from polysilicon and silicon nitride using surface micromachining techniques. These structures included trains of micromechanical involute-toothed spur gears. The gear diameters ranged from 60 to 1600 um. To increase fluid drive force, rotors were coated with tensile films to induce residual sttresses to delibrately warp them and thereby increase the efficiency of fluid powering by giving them a higher profile. For stuffer strucutres such as gears that must remain planar in order to mesh, vane were added to increase the...

Integrated Microphone with CMOS Circuits on a Single Chip

Eun Sok Kim
Richard S. Muller
1990
A miniature diaphragm microphone having sensitivity to acoustic signals at the level of conversational speech has successfully been integrated with CMOS circuits on a single chip. The microphone is built on 1.4 um thick LPCVD silicon nitride...

Electrostatic Comb Drive for Resonant Sensor and Actuator Applications

William C.-K. Tang
Roger T. Howe
1990

Interdigitated finger (comb) structures are demonstarted to be effective for electrostatically exciting the resonance of polycrystalline-silicon (polysilicon) microstrucutres parallel to the plane of the substrate. Linear plates suspended by a pair of folded-cantilever truss as well as torsional plates suspended by spiral and serpentine springs are fabricated from a 2 um-thick phosphorus-doped low-pressure chemical-vapor deposited (LPCVD) polysilicon film. Three experimental methods are used to characterize quasi-static and resonant motions: microscopic illumination, observation with a...

Assembly Techniques for Microelectromechanical Systems

Michael B. Cohn
Roger T. Howe
1998
Batch microassembly techniques for MEMS and related systems are described. As an alternative to monolithic integration, these processes address the need for low-cost MEMS packaging, MEMS / CMOS integration, and large, sparse arrays of microfabricated devices. Two approaches are pursued. The first, self-assembly,...

Micromachined Hot-Filament Vacuum Devices

Kirt R. Williams
Richard S. Muller
1997
We describe investigations on micromachined hot-filament vacuum devices, which are electronic devices made by micromachining an ohmically heated tungsten filamentthat acts as a source of blackbody-like radiation or of free electrons. The freestanding filaments, which are typically 200-500μm long, 5-20μm wide, and 0.7-2.3μm thick, are suspended over a cavity...

Micromachined Vibratory Rate Gyroscopes

William A. Clark
Roger T. Howe
1997
A vibratory rate gyroscope has been developed and implemented using a micromachined mechanical element and integrated circuitry on the same silicon substrate. The mechanical element is a proof mass suspended by springs which is driven into lateral ...

Electromechanical Characterization of Microresonators for Circuit Applications

Clark T.-C. Nguyen
Roger T. Howe
1991
The design of circuits incorporating microresonators which utilize electrostatic drive and sense is accompanied by a need for a convenient method to experimentally extract the circuit elements modelling the microresonators. Previously, techniques which electrically detect microresonator motional current ...