An Interface Enhanced Spectroscopic Ellipsometry Technique: Application to Si ‐ SiO2

Abstract

In this research we demonstrate an ellipsometry technique that is sensitive to the interfacial region between a dielectric film and substrate. Essentially, a film with substrate is immersed in a liquid that index matches to the film, thereby optically removing the film from the measurement. In addition, the use of spectroscopic and multiple angles of incidence ellipsometry provide sufficient specification of the interface parameters, which, along with the enhanced sensitivity to the interface, enables the optical measurement of the interfacial properties. Theoretical and experimental verification is provided, along with application to the Si-SiO~ interface.

Si/SiO2 interface studies by spectroscopic immersion ellipsometry and atomic force microscopy

“…We have shown that the sensitivity is increased more than tenfold using the liquid ambient. 9 In our previous research, we investigated the evolution of the SiISiO 2 interface as a function of high temperature annealing (750-10000C) by SIE 10 and used the interface model shown in Fig. 2, which is also applicable to this study.…”

Contribution of interface roughness to the infrared spectra of thermally grown silicon dioxide films

“…Yakovlev et al reported on the near-interfacial properties using visible spectroscopic ellipsometry with the immersion method. 35,36 They assumed that the protrusions of silicon and the suboxide exist at the interface, and determined that the interfacial layer thickness and the volume fraction are 0.98ϩ0.34 nm and from 0.687 to 0.991, respectively, summed over oxide and suboxide. Translating their result to ours, a depolarization factor L of 0.6 using the relations aϭͱ2D/(4R) and Lϭa/(aϩ2), where the radius of protrusions, R, is 0.98 nm and the distance between protrusions D, is 4.4 nm, are obtained.…”

Measurement of N in nitrided oxides using spectroscopic immersion ellipsometry

“…The SIE data were modeled using previously developed procedures 18,19,22 and using the two film model which we already found successful for studying the evolution of the SiO 2 -Si 18 -22 interface and is shown in Fig. 3.…”

“…Using this model the SIE data on all the samples were reduced into the two model parameters L N and R and these are shown in Table I. The fitted values shown were obtained using an effective medium approximation at the 90% confidence level as previously discussed in detail, 18,19,22 and in all cases the error associated with the fits were less than Ϯ10% in thickness. A systematic increase in the N content, as is represented by L N , is seen, and a decrease of R with increasing N is also observed.…”

“…A fused silica immersion cell has been designed for the variable angle of incidence and spectroscopic measurements. 18,22 The most significant feature of the cell is that the two optically flat and annealed fused silica plates, serving as the entrance and exit windows, are connected rigidly to the polarizer and analyzer arms, but not to the cell. The windows were adjusted to be exactly orthogonal to the incident light at the straight-through position of the ellipsometer ͑ϭ90°͒, in order to avoid any deviation of the incident light beam when it passes through adjacent media with different indexes.…”