EXCIMER LASER CLEANING AND PROCESSING OF SI(100) SUBSTRATES IN ULTRAHIGH-VACUUM AND REACTIVE GASES

We have examined the effect of KrF excimer laser irradiation (248 nm, 20-25 ns) on Si(100) substrates under ultrahigh vacuum conditions and in controlled partial pressures of reactive gases. Surface compositions were determined before and after irradiation using in situ angle resolved x-ray photoelectron spectroscopy. We varied peak power, pulse energy, and halocarbon (CF4) or carbon monoxide (CO) pressures to investigate their effects on oxygen and carbon removal. Energy densities near 500 mJ/cm2 were sufficient to eliminate the carbon contamination; higher energies, which depended on the silicon preparation conditions, were required for oxygen removal. Samples were irradiated by pulses at 480-740 mJ/cm2 in molecular oxygen (O2) environment after cleaning to determine pulse energy and gas pressure requirements for oxide regrowth.