Optimization of a Low-Power Chemoresistive Gas Sensor: Predictive Thermal Modelling and Mechanical Failure Analysis.

Andrea Gaiardo,Erica Iacob,David Novel,Elia Scattolo,Luisa Petti,Paolo Lugli,Alessio Bucciarelli,Alvise Bagolini,Francesco Ficorella,Michele Crivellari,Antonino Picciotto

doi:10.3390/s21030783

Abstract

The substrate plays a key role in chemoresistive gas sensors. It acts as mechanical support for the sensing material, hosts the heating element and, also, aids the sensing material in signal transduction. In recent years, a significant improvement in the substrate production process has been achieved, thanks to the advances in micro- and nanofabrication for micro-electro-mechanical system (MEMS) technologies. In addition, the use of innovative materials and smaller low-power consumption silicon microheaters led to the development of high-performance gas sensors. Various heater layouts were investigated to optimize the temperature distribution on the membrane, and a suspended membrane configuration was exploited to avoid heat loss by conduction through the silicon bulk. However, there is a lack of comprehensive studies focused on predictive models for the optimization of the thermal and mechanical properties of a microheater. In this work, three microheater layouts in three membrane sizes were developed using the microfabrication process. The performance of these devices was evaluated to predict their thermal and mechanical behaviors by using both experimental and theoretical approaches. Finally, a statistical method was employed to cross-correlate the thermal predictive model and the mechanical failure analysis, aiming at microheater design optimization for gas-sensing applications.

Highlights

MNF—The Micro Nano characterization and fabrication Facility, Bruno Kessler Foundation, Faculty of Science and Technology, Free University of Bolzano-Bozen, Piazza Università 5, MST—MicroSystem Technology Group, Bruno Kessler Foundation, Via Sommarive 18, 38123 Trento, Italy; These authors contributed to this work
The model proposed in this work aims at estimating the power consumption of a MH on a free-standing gas sensor membrane during the design phase, prior to the microfabrication process
They demonstrated that the constant of thermal conductivity at the backside is three orders of magnitude lower than the heat transfer coefficient (α(m)) at the front side

Summary

Introduction

MNF—The Micro Nano characterization and fabrication Facility, Bruno Kessler Foundation, Faculty of Science and Technology, Free University of Bolzano-Bozen, Piazza Università 5, MST—MicroSystem Technology Group, Bruno Kessler Foundation, Via Sommarive 18, 38123 Trento, Italy; These authors contributed to this work. Three microheater layouts in three membrane sizes were developed using the microfabrication process. The performance of these devices was evaluated to predict their thermal and mechanical behaviors by using both experimental and theoretical approaches. Instruments mainly used for the accurate detection of gaseous compounds are based on light-matter interactions (IR and chemiluminescent spectroscopes) or on mass spectrometry [3,4,5,6] These analyzers are reliable, having both a high selectivity for the type of analyzed gas and low detection limits, their widespread sustainable use is still limited by significant shortcomings, including the high cost and the large size and weight that render them cumbersome. Among the various solid-state gas sensors investigated, the most studied are the chemoresistive gas sensors because of published maps and institutional affiliations

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