pH sensing characterization of programmable Sm₂O ₃/Si₃N₄/SiO₂/Si electrolyte- insulator-semiconductor sensor with rapid thermal annealing

A programmable silicon-oxide-nitride-oxide-silicon (SONOS)-like electrolyte-insulator-semiconductor (EIS) sensor with a Sm₂O ₃/Si₃N₄/SiO₂/Si structure is demonstrated for pH detection. This proposed programmable EIS sensor with insulator-nitride-oxide (INO) multiple sensing layers exhibits a high pH sensitivity (larger than the ideal Nernst response, ∼59 mV/pH) owing to the hydrogen ion attraction by electrons trapped within the embedded Si ₃N₄ layer after stressing. To increase the pH response, rapid thermal annealing is performed on the programmable EIS devices. The obtained results support our hypothesis that the pH response can be effectively increased after 700 °C annealing. A sensing model on the basis of the charge attraction and surface roughness is also presented. Compared with the conventional EIS device, the programmable EIS sensor functionalized with annealing and stressing can be used in future pH sensor applications owing to its high pH sensing response.