Permeated porous silicon for hydrocarbon sensor fabrication

To realise advanced solid-state microsensors for a reliable monitoring of v ery low concentrations of pollutant species such as NO,, SO2, CO, O-3 and a romatic hydrocarbons, the use of porous silicon (PS) layers permeated with mixed semiconducting oxides (Sn-V-O) has been proposed and explored. A low concentration C6H6 sensor made of a permeated macroporous silicon layer on a massive Si substrate has exhibited an excellent performance. To reduce th e power consumption down to the level reported for micromachined gas sensor (0.1 W), and to make the device feasible for operation in a fast-pulsed te mperature mode, a novel sensor architecture has been designed. The main fea ture of the device is represented by a permeated suspended macroporous Si m embrane (few tens of microns thick) on top of which a heater resistor and a temperature sensor are integrated. In this paper the PS formation and proc essing are presented. Results on the morphological characterization of perm eated macroporous silicon membrane are also illustrated. Finally, the elect rical response of the device exposed to gas mixtures of different compositi ons is shown. (C) 1999 Elsevier Science S.A. All rights reserved.