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 (∼2 × 10⁵ 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.