Radio-frequency bias effects on SiO2 films deposited by distributed electron cyclotron resonance plasma enhanced chemical vapor deposition

Abstract

The effects of radio-frequency (rf) bias on the chemical, physical and electrical properties of SiO2 films deposited by distributed electron cyclotron resonance plasma enhanced chemical vapor deposition have been investigated. The rf bias power densities used here are relatively low (≤0.3 W/cm2) compared to that used by other researchers, but their influences on deposition processes and on film properties are apparent: the deposition rate decreases with increasing rf bias; the in situ relaxation process of the oxide and the observed surface polish effects have been found to be caused by ion bombardment. The most important effects of the rf bias are on the electrical properties of the deposited films. In particular, a SiO2 film without net fixed charges may be deposited with a low rf bias. It is also shown that the increase in interface trap density with rf bias power is not caused by ion bombardment but to the electron injection from the Si substrate towards the Si/SiO2 interface.