Electrical measurements of RF-generated plasmas using a driven electrostatic probe technique

An RF-compensated electrostatic probe has been used to investigate RF-generated plasmas. Measurements have been undertaken on N2, N2/CCl4, CCl4 and SF6 plasmas. Calculated values of electron density (Ne) and ion density (Ni) for electronegative gas plasmas indicate the presence of negative ions, since Ni ( approximately 1016 m-3) is significantly greater than Ne( approximately 1014 m-3). Electron temperatures (Te) also increase with the addition of CCl4 to N2 plasmas, which is consistent with the formation of negative ions by electron attachment reactions. Electrical measurements on SF6 plasmas have been compared with etch rates of polycrystalline silicon, silicon dioxide and photoresist. An increase in linewidth loss of polycrystalline silicon with increasing sheath potential is explained by increased spontaneous etching due to atomic fluorine.