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A new microstructured silicon substrate for ultrathin gas-sensitive films

: Schütze, A.; Weber, U.; Zacheja, J.; Kohl, D.; Mokwa, W.; Rospert, M.; Werno, J.


Sensors and Actuators. A 37/38 (1993), pp.751-755
ISSN: 0924-4247
Eurosensors <6, 1992, San Sebastian>
Conference Paper
Fraunhofer IMS ()
Dünnschichtwiderstand; electromagnetic interference; Elektrodenanordnung; elektromagnetische Störung; gas sensor; gassensor; microsystem; Mikrosystemtechnik; nitrogen oxide; silicium; silicon; Stickstoffoxid; Substrat; substrate; thin film resistors; thin films

Microstructured substrates featuring interdigitated electrodes with a high length-to-width ratio allow the evaluation of thin films with very high sheet resistivity even in environments with large electromagnetic interference. However, thin phthalocyanine (Pc) films vacuum evaporated on substrates with conventional interdigitated (ID) electrodes deposited on top of a planar surface, develop cracks at the edges of the contact stripes. For samples with a film thickness of 200 monolayers (ML) corresponding to 80 nm this causes a resistance two orders of magnitude higher than expected for the chosen length-to-width ratio. A new microstructured Si substrate with in-plane interdigitated (IPID) electrodes is designed to achieve minimum height differences on the surface. This substrate features interdigitated electrodes with a length-to-width ratio of 52 000:1 and, additionally, an integrated heating element and temperature-sensitive resistor.