Charging phenomenon of insulators in negative-ion implantation

The energy distribution of secondary electrons emitted from an insulator during negative-ion implantation was measured. According to secondary-electron-energy analysis, the charging voltage of insulator was estimated from the measured energy distribution. The experimental results in negative-carbon-ion implantation showed that the charging voltages of a quartz glass plate and a photoresist film on silicon substrate are several negative volts in the energy range from 5 to 35 keV and decrease gradually with increasing ion energy. The low negative charging voltage of insulator and the most probable energy of the secondary-electron energy distribution during negative-ion implantation are discussed using a charging model based on an electric double layer.