Reduction of ultra-violet-radiation induced damage and its time-resolved measurement using pulse-time-modulated plasma

Plasma-radiation-induced SiO₂-damage in inductively coupled He, Ar, and O₂ plasmas was investigated by measurements of electrical hole currents generated by the plasmas in SiO₂ film using on-wafer monitoring, of electron densities in the plasmas, and of vacuum-ultraviolet (VUV) radiation intensity from the plasmas. The VUV intensities and the hole currents were reduced by pulse-time-modulated (TM) plasma, in spite of the electron densities still remained. This indicates that the TM plasma can reduce the electrical damages that are created by the hole current in the SiO₂ of a MOS structure. In TM plasma, the VUV intensity dramatically decayed after the plasma-off time. On the other hand, the electron density gradually decreased with more than three times longer decay constant than the VUV intensity in the He TM plasma. These results show that lowering of electron temperature in the plasma during discharge-off period reduced the VUV intensity. In addition, it was found that the hole-current-decay curve consists of two components, which is also discussed. In charge-coupled-device (CCD) image sensors, an increase in a dark current of the CCD was suppressed by using the TM plasma.