Hydrogen gas detection using metal-oxide-semiconductor capacitor with Ni/SiO2/Si structure

In this study a MOS capacitive-type hydrogen gas sensor with the Ni/SiO₂/Si structure has been fabricated. The sensor response (R%) and Flat-Band-Voltage (V_FB) has been investigated at 140 °C and 100 KHz frequency. sensors were fabricated on (0.22 Ω cm) <;400> n-type Si and oxide layer has been characterized using Atomic force microscopy (AFM). Sensors are reported at different SiO₂ film thickness 28 nm and 53 nm. Using MOS C-V measurement under the Bias Thermal Stress (BTS) technique, the trapped charges were measured. Results indicate an increase in trapped charge which is due to an increase in the oxide film thickness. The response decreases with the increase of SiO₂ film thickness. Experimental results demonstrate that the sensor is highly sensitive to SiO₂ film thickness, which can be used for response, response/recovery time and Vfb studies of MOS capacitive gas sensors and low-cost hydrogen detectors with 4% hydrogen concentration responses.