Influence of gridded gate structure on gas sensing behavior of hydrogen

Abstract

A gridded Pt/SiO2/Si MOS sensor for hydrogen detection has been fabricated on p-type ⟨100⟩ Si wafer having resistivity (1–6 Ω cm). The SiO2 and Platinum (Pt) gate thickness were kept about 10 nm and 35 nm. The performance of Pt gate MOS sensor was evaluated through C-V characteristics (capacitance vs voltage) upon exposure to H2 (250 ppm–4000ppm) at different frequencies (25 kHz and 50 kHz) in a closed chamber at air ambient atmosphere. The capacitance of the sensor decreases with increase in frequency as well as H2 gas concentration. The flat band voltage characteristics have been evaluated at different frequencies and concentrations. It decreases as the frequency and concentration of gas both increases. The maximum flat band voltage change was observed −0.6 V at 25 kHz. The sensor exhibits better sensitivity (∼88%) at low frequency (25 kHz). The high response of sensor is attributed to the side wall diffusion, increase in surface area caused by inner side wall and increase in porosity, increase in fixed surface state density, spill-over mechanism and change in interface state density on exposure of gas along with the formation of dipole layer.

PLL-Based Readout Circuit for SiC-MOS Capacitor Hydrogen Sensors in Industrial Environments

“…Cumulatively with this effect, charged states presented at the metal-oxide interface were also passivated, creating a dipole layer between Pd and SiO 2 . However, it was shown that the main contributor to hydrogen sensitivity was given by the further diffusion of H + deeper into the oxide and interaction with SiO 2 bulk traps [22,[38][39][40]. The trade-offs for this increase in susceptibility to H 2 were that the structure took a longer time to both stabilize its response and to release stored hydrogen atoms as the environment becomes inert.…”

A new 4H-SiC hydrogen sensor with oxide ramp termination

“…This is due to the relative simplicity of the fabrication process, together with their high sensitivity and signal amplification capability. Starting from the standard capacitor structure: catalytic metal gate-silicon dioxide-silicon carbide (MOSiC) [10], the technological processes were continually adjusted for better-quality structures, notable progress in sensing qualities being reported [11][12][13]. Despite their well-known drawbacks, the most used catalytic gate metal remains Pd [8] and Pt [14], while the most research effort is concentrated on the improving the oxide characteristics.…”