Measurement of the refractive index of thin SiO2 films using tunneling current oscillations and ellipsometry

Abstract

We use Fowler–Nordheim tunneling current oscillations to accurately determine the thicknesses of ultrathin SiO2 films, and with the thicknesses as input, we employ precision single wavelength ellipsometry to determine the real part of the refractive index for thin SiO2 films in the range of 4–6 nm. An average value for this refractive index was found to be 1.894±0.110. This value is shown to yield SiO2 thicknesses to an accuracy of ±0.1 nm. A SiO2 thickness-refractive index interpolation formula for the thin film regime is given.

Is adhesion superficial? Silicon wafers as a model system to study van der Waals interactions

“…The increase in refractive index to values up to n = 1.8, as predicted by several studies, [54][55][56] is highly unlikely for native oxide layers as polymer dewetting studies have shown via an indirect way: 24 Thin liquid polystyrene (PS) films prepared on Si wafers with native oxide layers (D SiO = 2.4 nm) were unstable and dewetted spinodally. Since this process is driven by the minimization of the free energy determined by the vdW potential 8,66 the refractive indexes of the oxide cannot be higher than the one of PS (≈ 1.59), as shown by Eq.…”

“…These findings were later on confirmed by other studies. 55,56 Experimental support for the double layer model, viz. the observation of an interfacial transition layer, is also given by previous studies.…”

Combined AFM and Brewster-angle analysis of gradually etched ultrathin SiO2 – Comparison with SRPES results

“…3 was used to calculate the refractive index n by taking into account the optical constants of the strained layer and of all respective interfacial regions. The value n = 1.55 obtained by this calculation is smaller than described by published curves on the n(d ox ) relationship in ultrathin thermal silicon oxides [17,18]. Upon etching, the measured parabolae, shown in Fig.…”

“…13, are fitted using n, d ox pairs. According to [17,18], an increase of the refractive index was determined towards the silicon interface. The slope, however, is smaller with a maximum value of n = 1.80 at etch step 4.…”

Near‐field nano‐ellipsometer for ultrathin film characterization

“…However, other researchers report elevated measurements of refractive index when simple models are applied to ultrathin films (e.g. Hebert et al ., 1996). In Fig.…”