Plasma Etching of SiO2 with CF3I Gas in Plasma-Enhanced Chemical Vapor Deposition Chamber for In-Situ Cleaning

Abstract

Non-global-warming CF3I gas has been investigated as a removal etchant for SiO2 film. Thermally fabricated SiO2 films were etched by the plasma generated with a gas mixture of CF3I and O-2 (CF3I/O-2) in the plasma-enhanced chemical vapor deposition chamber. The etch rate of SiO2 films was studied along with the process parameters of plasma etching such as chamber pressure, etching gas flow ratio of CF3I to CF3I/O-2, plasma power, and chamber temperature. Increasing the chamber pressure from 400 to 1,000 mTorr decreased the etch rate of SiO2 film. The etch rate of this film showed a minimum value at a gas flow ratio of 0.71 in CF3I to CF3I/O-2 and then increased at a higher CF3I gas flow ratio. In addition, the elevated plasma power increased the etch rate. However, the chamber temperature has little effect on the etch rate of SiO2 films. When only CF3I gas without O-2 was supplied for etching, polymerized fluorocarbon was formed on the surface, indicating the role of oxygen in ashing the polymerized fluorocarbon during the etching process.