A Fabrication Process with High Thermal Isolation and Vacuum Sealed Lead Transfer for Gas Reactors and Sampling Microsystems

This paper describes a six-mask fabrication process for vacuum-sealed microsystems including pressure and flow sensors, reaction chambers and reservoirs, and channels ranging from 100 nm to 10 μm in hydraulic diameter. All structures are countersunk into a glass substrate, resulting in a planar upper surface that eliminates stress concentrations and also facilitates further lithographic processing. The material choices and structural arrangements are designed to provide high thermal isolation (~2x10 K/W). Lead transfer between the three available levels of interconnect are accomplished with minimal parasitic capacitance (<1 fF), and low resistance (~1 Ω). A variety of test structures have been successfully fabricated.