Kinetic analysis of silicon oxidations in the thin regime by incremental growth

Abstract

The scaling of dry thermal oxides into the thin (<400 Å) range continues to motivate studies of the rapid initial oxidation rate of silicon unaccounted for by a linear-parabolic model. In this paper, silicon oxidation kinetics in this unresolved regime are studied by the incremental reoxidation of thin thermally grown and deposited silicon oxide layers on silicon. It is found that the reoxidation rates of thermally grown oxides in the thin regime rapidly decrease with increasing oxide thickness. In contrast, the reoxidation rates of deposited oxides are faster, and nearly thickness independent. It is also found that the reoxidation rates of thin thermal oxides can be significantly increased by inert thermal annealing. Existing thin-regime oxidation models are evaluated in light of these experimental findings, and it is concluded that only models invoking stress suppression of early oxidation kinetics can reconcile all experimental observations. In further support of a stress argument, the time and temperature effects of inert annealing are shown to be quantitatively consistent with a Maxwellian model for stress relaxation. Kinetic parameters extracted from experimental data are utilized to isolate specific mechanisms for the suppression of oxidation rate during the initial stages of silicon oxidation.

Oxidation of silicon: Further tests for the interfacial silicon emission model

“…According to this explanation, it is more accurate to say that the oxidation becomes slower for thick oxides rather than enhanced for thin oxides. This interpretation agrees with concluding experiments by Ajuria et al, 12 although the proposed underlying physical mechanism is completely different. Concerning the sublinear dependence on the oxygen partial pressure, P O 2 , it can easily be related to the emission of Si interstitials.…”

“…As commented in the previous subsection, we also realized that the interfacial emission model could account for the experiments published by Ajuria et al 12 We must remark that the explanation for these kinds of annealing experiments has always been qualitative. 12,16 What is really new with the in- terfacial emission model is that these experiments can be modeled quantitatively with the parameters of the model already obtained from the fits to independent experiments ͓the X͑t͒ curves of isothermal oxidation͔.…”

“…These are the experiments showing an enhancement of the oxidation after annealing of thin oxides in inert atmosphere. 12 This effect is easily explained because, after annealing, the distribution of Si interstitials becomes smoother, its concentration at the interface diminishes, and consequently, k increases ͓Eq. ͑6͔͒.…”

“…12,16 What is really new with the in- terfacial emission model is that these experiments can be modeled quantitatively with the parameters of the model already obtained from the fits to independent experiments ͓the X͑t͒ curves of isothermal oxidation͔. This point will be addressed in Sec.…”

“…Within the DG model, their experiments were formally explained as due to an increase in the parabolic rate constant during annealing. Four years later, Ajuria et al 12 extended these kinds of experiments to the thin oxide regime. Typical results are shown in Fig.…”