Structural properties and sensing characteristics of Y₂O₃ sensing membrane for pH-ISFET

The structural properties and sensing characteristics of Y₂O₃ sensing membrane were deposited on silicon substrates by reactive rf sputtering. The structural and morphological features of these films with annealing at various temperatures were studied by X-ray diffraction, atomic force microscopy, and X-ray photoelectron spectroscopy. It was found that Y₂O₃ sensing dielectrics annealed at 800 °C exhibit a high sensitivity of 56.09 mV/pH in the solutions from pH 2 to pH 12, a low hysteresis voltage of 13.6 mV in the pH 7 → 4 → 7 → 10 → 7, and a small drift rate of 1.24 mV/h in the pH 7 buffer solution. This annealing condition is suggested for the reduction of the interfacial SiO₂ and silicate formation, and the small surface roughness due to the well-crystallized Y₂O₃ structure.