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Open AccessArticle

Design and Fabrication of CMOS Microstructures to Locally Synthesize Carbon Nanotubes for Gas Sensing

1
Department of Microsystems, University of South-Eastern Norway, 3184 Borre, Norway
2
Department of Informatics, University of Oslo, 0373 Oslo, Norway
*
Author to whom correspondence should be addressed.
Sensors 2019, 19(19), 4340; https://doi.org/10.3390/s19194340
Received: 15 August 2019 / Revised: 3 October 2019 / Accepted: 6 October 2019 / Published: 8 October 2019
(This article belongs to the Special Issue Advanced Nanomaterials based Gas Sensors)
Carbon nanotubes (CNTs) can be grown locally on custom-designed CMOS microstructures to use them as a sensing material for manufacturing low-cost gas sensors, where CMOS readout circuits are directly integrated. Such a local CNT synthesis process using thermal chemical vapor deposition (CVD) requires temperatures near 900 °C, which is destructive for CMOS circuits. Therefore, it is necessary to ensure a high thermal gradient around the CNT growth structures to maintain CMOS-compatible temperature (below 300 °C) on the bulk part of the chip, where readout circuits are placed. This paper presents several promising designs of CNT growth microstructures and their thermomechanical analyses (by ANSYS Multiphysics software) to check the feasibility of local CNT synthesis in CMOS. Standard CMOS processes have several conductive interconnecting metal and polysilicon layers, both being suitable to serve as microheaters for local resistive heating to achieve the CNT growth temperature. Most of these microheaters need to be partially or fully suspended to produce the required thermal isolation for CMOS compatibility. Necessary CMOS post-processing steps to realize CNT growth structures are discussed. Layout designs of the microstructures, along with some of the microstructures fabricated in a standard AMS 350 nm CMOS process, are also presented in this paper. View Full-Text
Keywords: carbon nanotube; local CNT synthesis; CMOS–CNT integration; microstructures; microheater; CMOS-compatible temperature carbon nanotube; local CNT synthesis; CMOS–CNT integration; microstructures; microheater; CMOS-compatible temperature
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Roy, A.; Azadmehr, M.; Ta, B.Q.; Häfliger, P.; Aasmundtveit, K.E. Design and Fabrication of CMOS Microstructures to Locally Synthesize Carbon Nanotubes for Gas Sensing. Sensors 2019, 19, 4340.

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