Fabrication and characterization of undoped polysilicon nanowire for pH sensor

Polysilicon has great benefit in application of pH sensor due to the unique properties and easiness to use top-down approach. In this paper, we present fabrication and characterization of undoped polysilicon nanowire (NW) for pH sensor application. The fabrication processes steps involve were photolithography, etching, deposition and oxidation. 3-aminopropyltriethoxysilane or APTES were used to enhance the sensitivity of polysilicon layer as well as able to provide surface modification by undergoing protonation and deprotonation process. Surface analysis using SEM were used for surface morphology analysis. Different types of pH solution provide different resistivity and conductivity towards polysilicon surface. In addition, voltage, current, conductance against pH level are characterized and compared. Alkaline solution has the higher current as compared to acidic. This was due to the polysilicon layer contains more holes which are easily being attracted by — SiO to the surface and hence, forming a strong channel from source to drain. Results obtain reveal a linearity of pH measurement with a corresponding sensitivity of 4.65 nS/pH.