Chemical sensing: millimeter size resonant microcantilever performance

• Published in: Journal of micromechanics and microengineering Vol. 14; no. 9; pp. S23 - S30
• Main Authors: Fadel, L, Lochon, F, Dufour, I, Français, O
• Format: Journal Article Conference Proceeding
• Language: English
• Published: Bristol IOP Publishing 01.09.2004; Institute of Physics
• Subjects: Applied sciences; Electronics; Engineering Sciences; Exact sciences and technology; Instruments, apparatus, components and techniques common to several branches of physics and astronomy; Mechanical engineering. Machine design; Mechanical instruments, equipment and techniques; Micro and nanotechnologies; Microelectronic fabrication (materials and surfaces technology); Microelectronics; Micromechanical devices and systems; Physics; Precision engineering, watch making; Semiconductor electronics. Microelectronics. Optoelectronics. Solid state devices; Electromagnetism; Circuit design; Measurement sensor; Chemical sensor; Experimental study; Spray coating; Vibrometer; Cantilever beam; Silicon on insulator technology; Piezoelectric device; Piezoresistive device; Resonance frequency; Gas sensors; Microelectromechanical device; Gas detector
• ISSN: 0960-1317; 1361-6439
• DOI: 10.1088/0960-1317/14/9/004

Based on the use of a resonant cantilever, a mass sensitive gas sensor for the detection of volatile organic compounds (VOC) has been developed. Analyte gases are absorbed by a sensitive layer deposited on the cantilever: the resulting mass change of the system implies the cantilever resonant frequency decreases. In this paper, the process technology, based on the use of SOI wafer, is described. To integrate the measurement, piezoelectric and electromagnetic excitations are investigated and for the detection of microcantilever vibrations, piezoresistive measurement is performed. Then, the polymer choice and the spray coating system are detailed. Using various geometrical microcantilevers, the frequency dependence on mass change is measured and allows us to estimate the mass sensitivity (0.06 Hz ng-1). In gas detection the first experiments exhibit the sensor response, then by calculating the partition coefficient (K = 977), the minimum detectable concentration of ethanol is deduced and permits us to estimate the gas sensor resolution (14 ppm). Finally a comparison between millimeter size and micrometer size cantilevers shows the importance of noise in the design of an integrated sensor.