Excimer laser cleaning of Si(100) surfaces at 193 and 248 nm studied by LEED, AES and XPS spectroscopies

AES, XPS and LEED were used to study the role of the laser energy density and total photon dose on the efficiency of KrF (lambda=248 nm) and ArF (lambda=193 nm) excimer laser induced cleaning of Si(100) surfaces. Samples having the native oxide layer were first investigated. It was found that significant oxide removal takes place only at energy density high enough to exceed the threshold for permanent surface damaging. Atomically clean, damage free Si(100) surfaces were obtained irradiating pre-etched samples, which had only a thin SiOx (x<2) layer and F, C and O containing adsorbed species. At 248 nm, when using 15 pulses, complete contaminant elimination was achieved in regions exposed to 0.8 J/cm(2) without provoking any morphological modification of the surface. At 193 nm clean surfaces were produced using average energy densities as low as 0.2 J/cm(2), if the number of laser shots was properly increased.