Experimental Study on Favorable Properties of Compound RF Discharge Plasmas with a Tapered Shape Hollow Cathode Compared with a Plane Cathode

An experimental investigation on the characteristics of compound RF discharge plasmas with a tapered shape hollow-cathode (HC) compared with a plane cathode is presented for the development of processing plasma. Dense plasmas are shown to be generated in the wide range of working pressures, 3< p<90 Pa. It is clarified that the higher RF power yields the greater HC effect to increase the ratio of electron density with the HC to that without it. The HC effect is shown to work well for decreasing the self-bias potential compared with the plane cathode. It is clarified that the dense plasma with relatively low electron temperature produced by the compound RF discharge results from the synergetic effect of the lowered input RF power density and the effective increased discharge area due to the HC effect.