Design of miniaturized nitrite sensors based on silicon structure with back-side contacts

• Published in: Sensors and actuators. B, Chemical Chemical, 2002-03, Vol.83 (1-3), p.109-114
• Main Authors: Wyglądacz, K., Malinowska, E., Jaźwiński, J., Brzózka, Z.
• Format: Article
• Language: English
• Subjects: Back-side contact chip; Ion-selective membrane; Ion-selective sensors
• ISSN: 0925-4005; 1873-3077
• DOI: 10.1016/S0925-4005(01)01052-8

The reported back-side contact sensors were fabricated using a standard IC technology. The sensor chips were passivated with a silicon nitride layer deposited by LPCVD, which ensure the stability of measurements. The silver/silver chloride layers were deposited using electrochemical technique. It was found that these sensors exhibited fast and reversible response toward a chloride with near theoretical slopes over the 10−4 to 10−1M chloride concentration range. The response time was shorter than 10s. The statistical evaluation revealed that the proposed technology ensures preparation of sensor chips in a very reproducible way. Such sensors were modified by casting a polymeric nitrite-selective membrane that consisted of: Co(III)tetraphenylporphyrin (Co[TPP]NO2) as the ionophore, tridodecylmethylammonium chloride (TDMACl) as cationic lipophilic additives and plasticized polyurethane matrix. Two groups of nitrite sensors, with and without an intermediate electrolyte (pHEMA) layer were tested. Results showed that both groups of sensors exhibited similar selectivity toward anions (ClO4−>SCN−>NO2−>I−>NO3−>Br−>Cl−). However, smaller fluctuations of the measured EMF were observed for sensors possessing an internal electrolyte.