CMOS-compatible nanoscale gas-sensor based on field effect
The integration of a solid state gas sensor of the metal oxide sensor type into CMOS technology still is a challenge because of the high temperatures during metal oxide annealing and sensor operation that do not comply with silicon device stability. In the presence of an external electric field sensor sensitivity can be controlled through a change of the Fermi energy level and consequently it is possible to reduce the operation temperature. Based in this effect, a novel field effect gas sensor was developed resembling a reversed insulated gate field effect transistor (IGFET) with the thickness of gas sensing layer in the range of the Debye length (L-D). Under these conditions the controlling electrical field reaches the sensitive surface and a modulation of the Fermi energy level occurs, producing an effective control of gas sensitivity and sensor response. In this paper several aspects are treated, like technological fabrication process, complete sensor characterization by means of an electrical model and sensor response measurements. Other effects as base-line drift effects and layer thickness implications also are studied.