SENSORS BASED ON TECHNOLOGY 'NANO-ON-MICRO' FOR WIRELESS INSTRUMENTS PREVENTING ECOLOGICAL AND INDUSTRIAL CATASTROPHES

摘要

The problem of gas analyzers compatible with wireless networks can be solved by using sensors based on the "nano-on-micro" technology. The basis of this technology consists in nano-composite sensing metal oxide semiconductor or thermocatalytic materials deposited on a microhotplate fabricated using silicon or alumina microelectronic technology. As a result, the sensor combines the advantages of both technologies: on the one hand, high stability and sufficient selectivity of nano-composite materials, and, on the other hand, microprocessor compatibility, low-cost, mass-production possibilities, and low power consumption of microelectronic substrates. Two methods for the fabrication of microhotplates are the most promising: the silicon based technology of silicon oxide/silicon nitride membranes and the CeraMEMS technology of thin alumina films (TAF). The first technology enables the fabrication of microheaters with a power consumption around 20 mW for an operating temperature below 450℃. Advantages of CeraMEMS platforms are: (1) operation at temperature up to 600℃ and, potentially, up to 800℃; (2) robustness compared with silicon chip with thin membrane; (3) perfect Pt and sensing layer adhesion without any adhesive layers; (4) low cost of middle scale production (10~4-10~7 chips per year) compared with the silicon technology. The CeraMEMS platform can be used for the fabrication of semiconductor and thermocatalytic gas sensors, as a source of IR radiation for optical gas sensors and as bolometers. The sensor withstands ～7 × 10~6 on-off cycles. Heater resistance drift is below 3% per year at 550℃.