Spatial distributions of gas composition in rf glow discharge plasmas measured using a quartz sensor

A quartz sensor can detect changes in gas composition caused by plasma because the quartz sensor output depends on the total pressure, viscosity, and molecular weight of the gas. This simple mode of quartz sensor measurement was used to obtain spatial distributions of the gas composition changes in the plasmas between a chamber inner wall and a plasma electrode. These spatial distributions reflect gas phase reactions in the plasmas. For that reason, they are helpful to elucidate the reaction mechanisms occurring in the plasmas. Applying such quartz sensor measurements for hydrogen and argon–hydrogen plasmas, we found that the spatial distributions of the gas composition change, as measured using a quartz sensor, depend on source gases. The positions at which the quartz sensor output show the maximum gas composition change for hydrogen and argon–hydrogen plasmas were at the chamber inner wall and near the edge of the plasma electrodes that are the closest positions to the plasma glow. These results show that the gas composition change detected using the quartz sensor resulted from degassing from the chamber inner wall and the plasma electrodes.