Ultrafast UV-laser-induced oxidation of silicon: Control and characterization of the Si-SiO2 interface

Abstract

A new low-temperature method of rapidly forming (>100 Å/sec) high-quality patterned silicon dioxide (SiO2) layers up to a thickness of 1 μm on silicon substrates is presented. Ultraviolet pulsed laser excitation in an oxygen environment is utilized. Infrared absorption spectroscopy, capacitance-voltage measurements, and soft x-ray photoemission are employed to characterize the oxide films and the Si-SiO2 interface. No shift, but a significant broadening of the Si-O stretching mode compared with thermally grown oxides is found, indicating that the laser-grown oxide is stoichiometric but with a higher degree of disorder. Similar results are obtained from soft x-ray photoemission data: the bulk of the laser-grown SiO2 shows no sign of SiOx suboxides, while at the interface a layer of SiOx is found of comparable thickness as in thermally grown SiO2. From capacitance-voltage measurements we deduce a fixed oxide charge near the Si-SiO2 interface of 6×1010/cm2 for oxides that have been thermally annealed following the laser-induced growth making this material a candidate for applications in semiconductor devices.