Ultra-low temperature oxidation of silicon using UV light-exited ozone in wafer-transfer type chamber

UV light-exited ozone has been applied for rapid low-temperature oxidation of silicon in a wafer-transfer type chamber. Oxidation was made in almost 100% ozone atmosphere with KrF excimer laser (248 nm) which enables the effective supply of O (¹D) atoms to the processed surface. In this system, SiO₂ film with a thickness of more than 3.5 nm is achieved even as low as 200°C. Uniform 2.9 nm film formation over 5-inch wafer with a thickness fluctuation of 0.1 nm was also obtained when KrF laser irradiation area was enlarged by a cylindrical concave lens. Current-voltage measurement has been employed to characterize SiO₂ films and it is confirmed that the catastrophic breakdown field strength was 13 MV/cm. Processing pressure dependence of density of O(₁D) atoms which contributing to the oxidation was estimated. Experimental result that the thickness of SiO ₂ film increases by decreasing the processing pressure agrees with our estimated result at the pressure range between 340 Pa and 820 Pa.