Effect of process parameters of UV-assisted gas-phase cleaning on the removal of PEG (polyethyleneglycol) from a Si substrate

Abstract

An experiment to remove PEG (polyethyleneglycol) by using UV-enhanced O-2 GPC (gas-phase cleaning) at low substrate temperatures below 200 degrees C was executed under various process conditions, such as substrate temperature, pressures and UV exposure. The possibility of using UV/O-2 GPC as a low-temperature in-situ cleaning tool for organic removal was confirmed by the removal of a PEG film with a thickness of about 200 nm within 150 seconds at a substrate temperature of 200 degrees C. In UV/O-2 GPC with substrate temperatures higher than the glass transition temperature, the substantial increase in the PEG removal rate can be explained by surface-wave formation. The optimal pressure condition can be understood by considering a partitioning of the UV energy between the gas phase and the organic film on the substrate. In the present work, the optimal pressure was determined to be 5 Torr by observing the spectra and the ratio (C-O+C=O)/(C-H) in the PEG film.