Comparison between Bosch and STiGer Processes for Deep Silicon Etching

Micro-optical gyroscopes (MOGs) place a range of components of the fiber-optic gyroscope (FOG) onto a silicon substrate, enabling miniaturization, low cost, and batch processing. MOGs require high-precision waveguide trenches fabricated on silicon instead of the ultra-long interference ring of conventional F OGs. In our study, the Bosch process, pseudo-Bosch process, and cryogenic etching process were investigated to fabricate silicon deep trenches with vertical and smooth sidewalls. Different process parameters and mask layer materials were explored for their effect on etching. The effect of charges in the Al mask layer was found to cause undercut below the mask, which can be suppressed by selecting proper mask materials such as SiO2. Finally, ultra-long spiral trenches with a depth of 18.1 μm, a verticality of 89.23°, and an average roughness of trench sidewalls less than 3 nm were obtained using a cryogenic process at −100 °C.

Section: Icp Etching Of Mog Spiral Trenchesmentioning

confidence: 99%

Inductively Coupled Plasma Dry Etching of Silicon Deep Trenches with Extremely Vertical Smooth Sidewalls Used in Micro-Optical Gyroscopes

Zhang

Sun³

et al. 2023

“…Multiple through-holes with a diameter of 1.5 mm are obtained by deep reactive-ion etching (DRIE) in the 600-μm thick silicon wafer, as presented in Figure 3e. The silicon through-holes are etched by the Bosch process during DRIE, where the deposit phase and the etch phase repeat alternately [32]. The etching rate is about 11 μm/min.…”

Section: First Anodic Bondingmentioning

confidence: 99%

Wafer-Level Filling of MEMS Vapor Cells Based on Chemical Reaction and Evaporation

Guo

Meng²,

Dan

et al. 2022

Micro-electro-mechanical system (MEMS) vapor cells are key components for sensors such as chip-scale atomic clocks (CSACs) and magnetometers (CSAMs). Many approaches have been proposed to fabricate MEMS vapor cells. In this article, we propose a new method to fabricate wafer-level filling of MEMS vapor cells based on chemical reaction and evaporation. The Cs metals are firstly obtained through the chemical reaction between cesium chloride and barium azide in a reservoir baseplate. Then, the Cs metals are evaporated to the preform through the microchannel plate and condensed on the inner glass surface of the preform. Lastly, the MEMS vapor cells are filled with buffer gas, sealed by anodic bonding, and mechanically diced into three dimensions: 5 mm × 5 mm × 1.2 mm, 4 mm × 4 mm × 1.2 mm, and 3 mm × 3 mm × 1.2 mm. The full width at half maximum (FWHM) linewidth of the coherent population trapping (CPT) signal of the MEMS vapor cells is found to be 4.33 kHz. The intrinsic linewidth is about 1638 Hz. Based on the CPT signal, the frequency stability is 4.41 × 10−12@1000 s. The results demonstrate that the presented method of the wafer-level filling of MEMS vapor cells fulfills the requirements of sensors such as CSACs.

“…On one side, several papers address typical problems of pattern transfer, such as the mask effect on the lateral undercut [ 3 ] and etch lag [ 4 ]. Different techniques, such as Bosch and STiGer, are compared [ 5 ] and reviewed [ 1 ] in order to provide a wider overview of their new capabilities. New plasma sources such as ICP systems using burst waves are explored to increase the silicon etching rate [ 6 ].…”

mentioning

confidence: 99%

Editorial for the Special Issue on Recent Advances in Reactive Ion Etching and Applications of High-Aspect-Ratio Microfabrication

Romano,

Jefimovs

2023