Development of Low-Drift pH Electrodes Based on Neutral Carrier in PVC Overlayered Metallizations

The majority of work on pH ISFET's has been done with devices whose gate has been overlayered with solid-state insulators formed by either vacuum deposition or chemical vapor deposition (silicon dioxide and nitride, oxides of aluminum, iridium, or tantalum). Historically, these layers have. shown problems of drift, redox sensitivity, degradation of response, and shortened lifetime. The recent introduction of improved pH neutral carriers has provided another possible approach. When these carriers are incorporated into a PVC matrix, and used in symmetrical solution contact configuration, they form electrodes which are highly selective, maintain sensitivity, show low drift, and provide long lifetime. This work describes the results for a-suitable metallization/membrane configuration which maintains these desirable characteristics, the degree to which the resultant system has been miniaturized, and its prospects for usage as part of an ISFET device.