Focussed ion beam based fabrication of micro-electro-mechanical resonators

A simple and fast process to fabricate micro-electro-mechanical (MEM) resonators with deep sub-micron transduction gaps in thin SOI is presented. The proposed process is realized on both 350nm and 1.5μm thin silicon-on-insulator (SOI) substrates, evaluating the possibilities for MEMS devices on thin SOI for future co-integration with CMOS circuitry on a single chip. Through the combination of conventional UV-lithography and focused ion beam (FIB) milling the process needs only two lithography steps, achieving ∼100nm gaps, thus ensuring an effective transduction. Different FIB parameters and etching parameters and their effect on the process are reporte

Fabrication of silicon-on-insulator MEM resonators with deep sub-micron transduction gaps

The paper proposes and validates a low-cost technological process for the realization of mono-crystalline micro-electro-mechanical (MEM) resonators with deep sub-micron transduction gaps, on silicon-on-insulator (SOI) substrates. The MEM resonators are designed to work as bulk lateral resonators (BLR) in which the resonance of a suspended mass is excited and detected by lateral electrodes. For MEM BLRs, nano-scaled gaps (<200nm) are essential to reduce the motional resistance in the order of few kΩ as well as to avoid the use of large DC applied voltages. Only standard optical lithography with 1μm resolution and IC-compatible processing steps are employed to obtain 100-200nm wide gaps with very high aspect-ratios of more than [40:1], allowing the fabrication of high Q resonators for MHz to GHz operating frequency rang

Fabrication of MEMS Resonators in Thin SOI

A simple and fast process for micro-electromechanical (MEM) resonators with deep sub-micron transduction gaps in thin SOI is presented in this paper. Thin SOI wafers are important for advanced CMOS technology and thus are evaluated as resonator substrates for future co-integration with CMOS circuitry on a single chip. As the transduction capacitance scales with the resonator thickness, it is important to fabricate deep sub-micron trenches in order to achieve a good capacitive coupling. Through the combination of conventional UV-lithography and focused ion beam (FIB) milling the process needs only two lithography steps, enabling therefore a way for fast prototyping of MEM-resonators. Different FIB parameters and etching parameters are compared in this paper and their effect on the process are reported

Bulk Lateral MEM Resonator on Thin SOI With High Q-Factor

The fabrication, design, and characterization of high-quality factor microelectromechartical (MEM) resonators fabricated on thin-film silicon-on-insulators (SOIs) are addressed in this paper. In particular, we investigate laterally vibrating bulk-mode resonators based on connected parallel beams [parallel beam resonators (PBRs)]. The experimental characteristics of PBRs are compared to disk resonators and rectangular plate resonators. All the reported MEM resonators are fabricated on 1.25-mu m SOI substrates by a hard mask and deep reactive-ion etching process, resulting in transduction gaps smaller than 200 nm. Additionally, this fabrication process allows the growth of a thermal silicon dioxide layer on the resonators, which is used to compensate the resonance-frequency dependence on temperature. Quality factors Q, ranging from 20 000 at 32 MHz up to 100 000 at 24.6 MHz, are experimentally demonstrated. The motional resistances R-m are compared for different designs, and values as low as 55 k Omega at 18 V of bias voltage are obtained with the thin SOI substrate. The thermal sensitivity of the resonance frequency is investigated from 200 K to 360 K, showing values of -15 ppm/K for the PBRs, with a possible compensation of 2 ppm/K when using 20 nm of SiO2