Integration of tungsten layers for the mass fabrication of WO3-based pH-sensitive potentiometric microsensors

(W/WO3–Ag/AgCl) and (Pt/IrO2–Ag/AgCl) potentiometric microdevices were developed for pH measurement in liquid phase using a (Pt–Pt–Ag/AgCl) electrochemical microcells (ElecCell) silicon-based technological platform. A special emphasis was placed on the mass fabrication of the W/WO3 microelectrode using sputtering deposition and oxygen plasma processes. Compared to the Pt/IrO2-based one, the W/WO3-based microelectrodes showed lower performances regarding the pH measurement. Nevertheless, since W/WO3 microelectrodes yielded quasi-Nernstian sensitivity (around 55 mV/pH) in the [2], [3], [4], [5], [6], [7], [8], [9], [10], [11] and [12] pH range, tungsten oxide WO3 can be considered as a good candidate for the mass fabrication of pH microsensors using silicon technologies, even if important temporal drift (at least 6 mV/h) and high hysteresis (around 50 mV) were also evidenced.