Refractive index, relaxation times and the viscoelastic model in dry-grown SiO2 films on Si

Abstract

Inert thermal anneals were performed at various temperatures to determine annealing kinetics of dry thermally grown SiO2 films on Si. Two stages of relaxation are demonstrated. The film relaxes quickly to an intermediate level, and then progresses more slowly toward full relaxation. The relaxation times to attain the fully relaxed refractive index, 1.460, and full ≤3% swelling were found to fall below typical oxidation times at T≥1150 °C, in concurrence with the experimentally observed breakpoint in the refractive index versus growth temperature data. It is concluded that the linear viscoelastic model is sufficient to quantitatively explain the breakpoints in refractive index for both wet and dry thermally grown oxide.

Evidence of annealing effects on a high-density Si/SiO2 interfacial layer

“…5,18,19 While the bulk of the oxide is a stable amorphous SiO 2 layer, 18 the region near the Si͑001͒ interface may be a transition layer, possibly stabilized by high stresses which are known to exist within the oxides 20,21 and especially at the Si/SiO 2 interface. 14 Alternatively, the layer could be a region of higher density strained silicon, where the lattice is compressed slightly in the vertical.…”

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

“…We consider this interpretation to be convincing in the case of thick oxides. 16 In fact, it predicts 22 an abrupt change for the activation energy of the parabolic rate constant, B, around 1100°C, which has been indeed observed 8 Uematsu et al 7 consider an alternative mechanism also related with the oxide relaxation. According to them, the oxide stress would have a higher influence on v than on the diffusivity.…”

Spectroscopic immersion ellipsometry study of the mechanism of Si/SiO2 interface annealing

“…It is known that the refractive index of thin-film SiO 2 overlayers, n,, depends on thickness, L,, oxidation temperature, T., annealing temperature, T., and time, t., index of =he substrate It has been observed that the refractive index of the SiO 2 overlayer undergoes a relaxation during annealing (22)(23)(24)(25). …”

“…(2) using A=1.099 and X,=92.27 (10) which corresponds to bulk SiO 2 . The observed initial rapid relaxation of the effective refractive index (23) can be attributed to the evolution of the interface, and a detailed model for this will be discussed below.…”

“…(2-4). The relative volume fractions of the interfacial layer constituents f,-i, fsjx and fsio2 were calculated from the assumed geometry of the interface and given as: The characteristic relaxation time, t, is of the order of a few minutes at 1000 0 C and a few hours at 900 0 C (22)(23)(24)30). This strongly suggests that the viscous flow mechanism may be dominant at temperatures higher than -950 0 C, but becomes negligible at lower temperatures and for annealing times less then -1 hsur, i.e.…”