Study on SnO2/Al/SiO2/Si ISFET with a metal light shield

For conventional open-gate FET-based sensors, such as the ISFETs, the influence of light exposure is very sensitive. This drawback leading to change in the electrical characteristics. To reduce light-induced instability, the optimized ISFET structure with a metal light shield is investigated in this study. We used aluminum as a light shield and tin oxide as a pH sensitive layer to develop the ISFET devices with SnO2/Al/SiO2/Si and compared to SnO2/SiO2/Si ISFET sensors. The data show that ISFETs with an aluminum as a light shield can maintain a linear pH response of about 56–58 mV per unit pH in the pH range between 2 and 10, and have effectively decreased light sensitivity tested under 15 mW (room light about 0.3 mW) irradiation at wavelength of λ = 550 nm compared to the ISFETs without an aluminum light shield.