THERMAL-DESORPTION SPECTROSCOPY AND MOLECULAR-BEAM TIME-OF-FLIGHT STUDIES OF SILICON-WAFER ULTRAVIOLET OZONE CLEANING/

Ultraviolet (UV)/ozone cleaning is a promising way of decontaminating silicon wafers for industrial very large scale integrated processing. We have investigated the cleaning process in high-vacuum conditions ut ilizing a pulsed supersonic valve and an excimer lamp. With this setup , we are able to supply atomic oxygen onto Si surfaces with and withou t the simultaneous UV light exposure. We have discovered that thermal desorption spectroscopy analysis of the surface adsorbed species shows marked differences in the wafers processed under different conditions in high vacuum. We have confirmed that UV irradiation is a very essen tial factor in the UV/ozone cleaning process. In addition, we have car ried out time-resolved studies of species coming off the wafer surface s during UV/ozone cleaning, and found that the main by-products are CO , CO2, and H2O. The hydrocarbon removal reaction is not oxygen-supply limited. (C) 1997 American Vacuum Society.