In this paper, we report magnetic neutral loop discharge (NLD) plasma etching of fused silica (FS) and borosilicate glass (BSG), demonstrating high aspect ratio deep etch ( 100~\mu \text{m} ) with vertical walls (<3° deviation from vertical). This paper for the first time presents the systematic study of FS and BSG deep etching in NLD plasma. Four different masking materials have been explored including metal, amorphous silicon, bonded silicon, and photoresist. Etch parameters were optimized to eliminate unwanted artifacts, such as micro-masking, trenching, and faceting, while retaining a high aspect ratio (up to 7:1 for FS and 8:1 for BSG). In addition, a method for sidewall roughness mitigation based on postfabrication annealing was developed, showing the sidewall roughness reduction from the average roughness ( R{a} ) 900 to 85 nm. Further advances in deep plasma etching processes may enable the use of FS and BSG in the fabrication of precision inertial MEMS, micro-fluidic, and micro-optical devices. [2015-0078]

We demonstrate, for the first time, sub-1 Hz frequency symmetry in micro-glassblown wineglass resonators with integrated electrode structures. A new fabrication process based on deep glass dry etching was developed to fabricate micro-wineglasses with self-aligned stem structures and integrated electrodes. The wineglass modes were identified by electrostatic excitation and mapping the velocity of motion along the perimeter using laser Doppler interferometry. A frequency split (Δ f) of 0.15 and 0.2 Hz was demonstrated for n=2 and n=3 wineglass modes, respectively. To verify the repeatability of the results, a total of five devices were tested, three out of five devices showed Δ f<5 Hz. Frequency split stayed below 1 Hz for dc bias voltages up to 100 V, confirming that the low frequency split is attributed to high structural symmetry and not to capacitive tuning. High structural symmetry (< 1 Hz) and atomically smooth surfaces (0.23 nm Sa) of the resonators may enable new classes of high performance 3-D MEMS devices, such as rate-integrating MEMS gyroscopes. © 1992-2012 IEEE.

In this paper, we report Q -factor over 1 million on both n=2 wineglass modes, and high-frequency symmetry (Δ f/f ) of 132 ppm on wafer-level microglassblown 3-D fused silica wineglass resonators at a compact size of 7-mm diameter and center frequency of 105 kHz. In addition, we demonstrate for the first time, out-of-plane capacitive transduction on microelectromechanical systems wineglass resonators. High Q -factor is enabled by a high aspect ratio, self-aligned glassblown stem structure, careful surface treatment of the perimeter area, and low internal loss fused silica material. Electrostatic transduction is enabled by detecting the spatial deformation of the 3-D wineglass structure using a new out-of-plane electrode architecture. Out-of-plane electrode architecture enables the use of sacrificial layers to define the capacitive gaps and 10 μm capacitive gaps have been demonstrated on a 7-mm shell, resulting in over 9 pF of active capacitance within the device. Microglassblowing may enable batch-fabrication of high-performance fused silica wineglass gyroscopes at a significantly lower cost than their precision-machined macroscale counterparts. [2014-0251]