Effect of RF Plasma on Gridded Gate Pt/SiO2/Si MOS Sensor for Detection of Hydrogen

The effect of RF oxygen plasma treatment on SiO
₂
surfaces has been investigated and compared with nonplasma treated sensors. Eight samples of thermally grown ~120Å SiO
₂
film are treated with a different RF O
₂
plasma power and time. All sensors have been tested for different concentrations of H
₂
at 25°C. It is observed that the sensitivity of sensors increases for high duration (8 min) of plasma exposure at 40-W RF plasma power. The sensors treated at 50-W RF plasma for 8- and 12-min duration exhibited the decrease in sensitivity. Surface morphology of plasma treated SiO
₂
film surfaces has been studied by automic force microscopy (AFM) to have the estimation of porosity, grain size, and surface roughness. The high sensitivity can be attributed to the fact that O
₂
plasma treatment increases the porosity, grain size, and surface roughness of the SiO
₂
film. Fixed oxide charge density has also been evaluated as a function of hydrogen concentration for varying exposure time and RF power.