Analytical investigation of the feasibility of sacrificial microchannel sealing for Chip-Scale Atomic Magnetometers

An alkali metal vapor cell is a crucial component of the highly sensitive Chip Scale Atomic Magnetometers (CSAMs) that are increasingly deployed in a variety of electronic devices. Herein, we propose a novel microfabrication technique utilizing an array of microchannels at a bonded interface, to enable gas feedthrough for evacuation of unwanted gases from a vapor cell and subsequent introduction of an inert gas, followed by permanent sealing of the microchannels by reflow of a glass frit. The characteristics of glass frit reflow are analyzed to investigate the feasibility of using microchannels formed either on a silicon substrate, or embedded in a glass frit layer, with four different cross-sectional shapes considered. Prior to modeling the microchannels for simulation, the minimum cross-sectional size of a microchannel that fulfills gas feedthrough requirements was calculated and a value of 10 μm was determined based on a flow conductance model. The sealing of the microchannels was simulated using the finite element method (FEM) and the results revealed that flow resistance is a crucial design factor. Thus, embedded microchannel designs were more suitable for the proposed sealing technique than microchannel designs fabricated in silicon.