Detection of gas trace of hydrofluoric acid using microcantilever

Microcantilevers have been used as a gas sensor in order to detect Hydrofluoric acid (HF) in the concentration range of 0.26–13 ppm. Silicon derived elements (Si3N4, SiOx) were chosen to serve as chemical sensitive layer. Cantilever deflection and frequency shift were analyzed and compared as a function of the flow rate and the concentration of the HF molecules. The stoichiometry and roughness of the sensitive layer were found to be of major importance. Results show that the most appropriate signal at the lowest concentration (<10 ppm) is the cantilever deflection that is particularly sensitive to the change in surface stress induced by the lateral attack of SiOx surface by HF. The frequency shift that is mainly governed by the loss in cantilever mass can be used at higher concentration.