Role of Fluorine in Reactive Ion Etching of Silicon Dioxide

Thermal desorption from 15 keV, fluorine positive ion (F+)-implanted SiO2 has been studied using thermal desorption and X-ray photoelectron spectroscopies. Primary fluorine-related outgassing species SiF3 +, gaseous O2, and a great amount of water evolution representing the SiO2 network modification were observed. From comparatively well-investigated desorption spectra from NF3/Ar reactive-ion-etching (RIE)-exposed and CF4/Ar RIE-exposed SiO2, similar outgassing species and the desorption temperatures were observed. The desorption states for SiF3 + were not single as previously reported in the study of desorption states related to the thermal reaction with fluorocarbon polymer, but several desorption pathways existed. The observed similarity for SiF3 + is considered to be related to the induced microstructural changes, which possibly determine the final desorption path in RIE.