Thermo-Insulated Microstructures Based on Thick Porous Silicon Membranes

A new Si micromachined substrate heater element based on a thick (~20 mm) Porous Silicon (PS) membrane, as thermal insulating material, has been realized. The PS membrane exhibits very good thermo-insulating properties, which are comparable with those of the most commonly used very thin (0.2 mm) silicon nitride (Si3N4) membrane. Moreover, once the PS material is stabilized, the standard IC fabrication processes do not affect the PS membrane performances. Deposition of thick sensing layers, using the screen printing technique, has been realized. This result makes the new low power consumption Si micromachined substrate heater element suitable both for thin as well as for thick film gas sensor technologies.