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 dens ity and total photon dose on the efficiency of KrF (lambda=248 nm) and ArF (lambda=193 nm) excimer laser induced cleaning of Si(100) surface s. Samples having the native oxide layer were first investigated. It w as found that significant oxide removal takes place only at energy den sity high enough to exceed the threshold for permanent surface damagin g. Atomically clean, damage free Si(100) surfaces were obtained irradi ating 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 su rface. At 193 nm clean surfaces were produced using average energy den sities as low as 0.2 J/cm(2), if the number of laser shots was properl y increased.