Gas-phase surface processing prior to 3.2 nm gate oxidation

The pre-gate oxidation processing of Si surfaces involving an SCI clcan followed by a sequence of gas-phase low pressure exposures to AHF/methanol, UV/Cl₂, and UV/Q₂is investigated. A comparison with a wet clean shows inferior performance of the dry chemistries in terms of Ca removal and surface roughness (Rms= 0.07 nm and 0.31 respectively). In spite of these apparent deficiencies the 3.2 nm thick gate oxides grown on dry cleaned surfaces arc displaying electrical characteristics, particularly charge-to-breakdown, comparable to oxides grown on the wet cleaned surfaces. The possible reasons for this effect arc considered.