Study of the thermal oxidation reaction dynamics on strain-controlled Si surfaces

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To control in an atomic scale the gate insulator film of advanced strained-Si MOSFET devices, the thermal oxidation reaction dynamics on strain-controlled Si surfaces was investigated by UPS and RHEED combined with AES, and an oxidation reaction model mediated by the point defect generation (emitted Si atom + vacancy) due to the strain at SiO_2/Si interfaces was developed in this research.(1) The second oxide layer hardly grows after the two-dimensional oxide island growth with SiO desorption above 〜630℃, while it can growth gradually following the Langmuir-type adsorption below 〜630℃, suggesting that the second oxide layer growth kinetics is strongly affected by the point defect generation associated with the first oxide layer growth.(2) The Si atom emission kinetics caused by the strain due to the volume expansion of oxidation is quantitatively clarified by measuring the 2×1/1×2 domain ratio as a function of the oxide coverage during Langmuir-type adsorption on a Si(001)2×1 surface.(3) The rate of second oxide layer growth after Langmuir-type adsorption has a good linear correlation with the rate of oxide decomposition during void nucleation, indicating that the rate-limiting reaction of the second oxide layer growth is strongly concerned with that of void nucleation.(4) The oxide coverage dependence of the band bending measured by UPS showed a similar tendency to that of the amount of emitted Si atom observed by RHEED-AES. The findings of (3) and (4) can be comprehensively interpreted in terms of the point defect generation.(5) On the Si(001)c(4×4)-C surface carbonized by ethylene, the sticking probability of O_2 and the surface migration of adsorbed oxygen are considerably influenced by the strain, indicating an important role of the strain of a substrate surface in the oxidation reaction.