Energy Distribution Functions of Ions Impacted on a Negatively Biased Substrate in an Electron Cyclotron Resonance Microwave Plasma

Impacted ion energy distribution functions (IIEDFs) in Ar electron cycltron resonance(ECR) microwave plasma have been measured on a substrate biased negatively using a conventional retarding grid analyzer. With an increasing ion-neutral elastic collision probability, the IIEDFs were found to spread toward the low-energy side, forming two peaks. At the high collision probability (> 80 %) realized at high biased-voltage and gas pressure, the lower-energy ions formed higher peaks than the higher-energy ones. This result was caused by the charge-exchange collision. The impacted ion temperature estimated from the semilog plot of the analyzer current-voltage characteristics was roughly constant (≃ 0.6 eV) for collision probability < 80%.