ChemFET arrays for chemical sensing microsystems

Chemically sensitive field-effect transistors (ChemFETs), among the smallest chemical sensors available to-date, are attractive for use in integrated systems. Favorable attributes of the ChemFET array include inherent compatibility with microfabricated electronics, small size of only 400 μm by 500 μm, low noise, and simple support circuitry. ChemFET structure is similar to other insulated gate field-effect transistors except that the usual metal or polysilicon gate conductor is replaced with a semiconducting polymer or other chemically sensitive material. In this work, an array of eight ChemFETs utilizing different partially selective gate materials on each unit was constructed utilizing mainly standard microfabrication techniques. Although support electronics are currently housed off-chip, a prototype array format designed to allow for flip-chip bonding of an ASIC service chip was also fabricated Selectivity of an individual sensor can be improved but, in practical terms, the ensemble response of an array of devices is needed to reliably identify a chemical vapor. In the case of ChemFETs, the detection transduction mechanism is a chemical modulation of the workfunction (WF) of the gate material by the analyte gas.