Size Independent pH Sensitivity for Ion Sensitive FinFETs Down to 10 nm Width

Abstract

We investigate pH sensitivity dependence on width and length of ion sensitive field effect transistors (ISFETs) fabricated using CMOS FinFET technology. In the literature, there is currently no consensus about the pH sensitivity dependence on the FET geometrical dimensions. We observe no significant dependence of pH sensitivity on (Fin)FET widths (1000 to 10 nm) and lengths (1100 to 145 nm). The results indicate that it is possible to aggressively scale FETs, and create a dense array of pH sensors without any loss in sensitivity. These experimental findings are in accordance with our 3D TCAD modeling of electrolyte and (Fin)FET, which also show neither a degradation nor a boost in pH sensitivity when nano-scaling the FETs. Moreover, apart from ISFETs with SiO2 surface (32.3 ± 4.4 mV/pH), we report higher sensitivity with Ta2O5 surface (51.2 ± 4.2 mV/pH), which is also a more robust material.