Highly Sensitive p+Si/Al Thermopile-Based Gas Flow Sensors by Using Front-Sided Bulk Micromachining Technology

This article presents the design, fabrication, and characterization of a front-sided microfabricated high-sensitive p
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Si/Al thermopile-based gas flow sensor with high-performance, low-cost, and high-yield volume production. Compared to most of the previously reported p
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Si/Al thermopile-based flow sensors, the proposed sensor has a higher sensitivity and faster response time by the realization of embedding the cold junction of the p
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Si beam into the bulk silicon and optimizing the thermal insulation of the suspended dielectric membrane from the silicon substrate. The 1-D model is established and used to optimize the design of the proposed sensor in terms of key design parameters, including the dielectric membrane thickness, the height of the isolation cavity, and so on. Accordingly, a front-sided bulk micromachining technique is employed to construct the proposed gas flow sensor. Without the need for a double-sided micromachining process, a tiny size of 0.5 mm × 0.7 mm is achieved. The tested results show that the fabricated sensor has an ultrahigh sensitivity of 540 mV/(SLM)/W and a quick response time of 1.5 ms.