Kevin A. Shaw

SCREAM I: A single mask, single-crystal silicon, reactive ion etching process for microelectromechanical structures

A single-crystal slhcon, high aspect ratlo, low-temperature process sequence for the fabrlcatlon of suspended rmcroelectromechamcal structures (MEMS) usmg a smgle hthography step and reactwe Ion etching (RIE) IS presented The process IS called SCRJZAM I (single-crystal reactwe etchmg and metalhzatmn) SCREAM I IS a bulk mlcromachmmg process that uses RIE of a s~hcon substrate to fabricate suspended movable smgle-crystal s&on (SCS) beam structures Beam elements wth aspect ratios of 10 to 1 and widths rangmg from 0 5 to 4 0 Frn have been fabricated All process steps are low temperature (<3OO “C), and only conventronal sd~con fabrlcation tools are used photohthography, RIE, MIE, plasma-enhanced chemxal-vapor deposrtlon (PECVD) and sputter deposlhon SCREAM I IS a self-ahgned process and uses a smgle lithography step to define beams and structures srmultaneously as well as all necessary contact pads, electrIcal mterconnects and lateral capaators SCREAM I has been specifically deslgned for integration with standard Integrated cmxnt (IC) processes, so MEM deuces can be fabricated adjacent to prefabricated analog and dIgItal carcuitry In this paper we present process parameters for the fabncatlon of discrete SCREAM I devices We also discuss mask design rules and show micrographs of fabncated deuces

Capacitance Based Tunable Micromechanical Resonators

We present actuators which tune the resonant frequency of micromechanical oscillators. Experimental results show resonant oscillations from 7.7% to 146% of the original resonant frequency. Numerical results substantiate these results. Two failure modes have been identified which limit

Capacitance based tunable resonators

We present four electrostatic actuators that tune the stiffness and hence the resonant frequency of a micromechanical oscillator. Using these actuators, resonant frequencies have been reduced to 7.7% and raised to 146% of the original values. These shifts correspond to approximately two orders of magnitude reduction in stiffness and a doubling in stiffness, respectively. Comparisons are drawn between these actuators based on functionality, area utilization efficiency, linearity and stability. Other issues discussed are asymmetries, nonlinearities and failure modes. With regard to the nonlinearities, near the limit of resonant frequency reduction, we show the ability to tune the system into a bistable state.

Single-crystal silicon gyroscope with decoupled drive and sense

We present preliminary results for a single-crystal silicon gyroscope with decoupled drive and sense oscillators. The gyroscope is fabricated using a plasma micromachining process on a six-inch MEMS production line at Kionix, Inc. The process yields high-aspect-ratio structures, large structure-to- substrate separation, and low-parasitic electrodes, unlike designs that rely on silicon-on-insulator substrates, polysilicon, or thick epitaxial layers. We describe the fabrication process and emphasize the design, operation, and testing of the sensor. Results to date have yielded resolutions of 0.15 deg/sec over a 100 Hz bandwidth, short term bias stabilities less than 100 deg/hr, and quadrature signals less than 25 deg/sec.