Janna Rodriguez

Damping mechanisms in light and heavy-doped dual-ring and double-ended tuning fork resonators (DETF)

We present models and measurements of lightly-doped and heavily-doped dual ring/dual-bar and double-ended tuning fork (DETF) resonators. Both models and measurements indicate that the Q of these resonators is only slightly impacted by the doping level, despite being dominated by thermoelastic dissipation (TED), which has a strong dependence on doping-dependent material properties. We compare experimental measurements of Q over a range of temperatures with models for TED, anchor damping and squeeze film damping. We found that the Q of light and heavily-doped resonators can be accounted for by a combination of TED and anchor or squeeze film damping. These results indicate that it is possible to fully account for the damping mechanisms in MEMS resonators if temperature-dependent measurements of Q are compared with models of the important mechanisms including the temperature-dependent materials properties.

Wide-range temperature dependence studies for devices limited by thermoelastic dissipation and anchor damping

The aim of this study is to measure the quality factor (Q) for double-ended tuning fork (DETF) devices dominated by Thermoelastic Dissipation (TED) and width-extensional (WE) devices dominated by Anchor Damping over a wide temperature range. Testing of these two device families over this wide range led to two related findings. First, our results indicate that it is possible to completely account for the dissipation in these devices through the use of quantitative models and measurements over a wide temperature range. A second finding, presented for the first time, is that anchor damping can be clearly seen in WE mode devices, and this damping term shows a clear temperature dependence.

Robust Method of Fabricating Epitaxially Encapsulated MEMS Devices with Large Gaps

This paper presents a novel wafer-level thin-film encapsulation process that allows both narrow and wide trenches, which are necessary for traditional structures such as comb-drives. Fully functional devices with trench widths up to 50

Topology optimization for reduction of thermo-elastic dissipation in MEMS resonators

\mu \text{m}

Encapsulated inertial systems

are fabricated by employing a vapor phase XeF2 isotropic silicon etch to create large cavities and an epitaxial deposition seal to encapsulate the devices in an ultra-clean, high vacuum environment with no native oxide and humidity. In this paper, we demonstrate the robustness of the proposed fabrication process, as well as the inherent benefits of the high-temperature epitaxial encapsulation process: high quality factor, extreme stability, exceptional aging, and fatigue performance. [2017-0098]

Manipulation of heat flux paths in thermo-elastically damped resonators for Q optimization

This paper presents a topology optimization approach for reducing thermo-elastic dissipation (TED) in MEMS resonators. This algorithm is applied to a clamped-clamped resonant beam to maximize the quality factor (Q). Optimal designs have a Q ten times higher than a solid beam and are 75% higher than previously optimized devices. Furthermore, new designs have intuitive topologies. Beams are fabricated in <111> silicon wafers and experimental measurements of Q agree well with simulation.

Exploring Entrepreneurial Characteristics and Experiences of Engineering Alumni

There is significant interest in integration of multiple MEMS functionalities into a single compact device. Our group has developed a wafer-scale encapsulation process that provides an ultraclean, stable environment for operation of MEMS timing references, which has been commercialized by SiTime, Inc. In this paper, we discuss some of the issues associated with incorporation of inertial sensors into this encapsulation process, including design constraints, stiction, pressure, and other issues.