Atomic Structure and Optical Properties of Plasma Enhanced Chemical Vapor Deposited SiCOH Low-k Dielectric Film-=SUP=-*-=/SUP=-

The SiCOH low-k dielectric film was grown on Si substrate using plasma enhanced chemical vapor deposition method. Atomic structure and optical properties of the film were studied with the use of X-ray photoelectron spectroscopy (XPS), Fourier transform infrared (FTIR) absorption spectroscopy, Raman spectroscopy and ellipsometry. Analysis of XPS data showed that the low-k dielectric film consists of Si-O4 bonds (83%) and Si-SiO3 bonds (17%). In FTIR spectra some red-shift of Si-O-Si valence (stretching) vibration mode frequency was observed in the low-k dielectric film compared with the frequency of this mode in thermally grown SiO2 film. The peaks related to absorbance by C-H bonds were observed in FTIR spectrum. According to Raman spectroscopy data, the film contained local Si-Si bonds and also C-C bonds in the s-p3 and s-p2 hybridized forms. Scanning laser ellipsometry data show that the film is quite homogeneous, homogeneity of thickness is ~ 2.5%, and homogeneity of refractive index is ~ 2%. According to analysis of spectral ellipsometry data, the film is porous (porosity is about 24%) and contains clusters of amorphous carbon (~ 7%).

Anomalous Properties of the Dislocation-Free Interface between Si(111) Substrate and 3C-SiC(111) Epitaxial Layer

Thin films of single-crystal silicon carbide of cubic polytype with a thickness of 40–100 nm, which were grown from the silicon substrate material by the method of coordinated substitution of atoms by a chemical reaction of silicon with carbon monoxide CO gas, have been studied by spectral ellipsometry in the photon energy range of 0.5–9.3 eV. It has been found that a thin intermediate layer with the dielectric constant corresponding to a semimetal is formed at the 3C-SiC(111)/Si(111) interface. The properties of this interface corresponding to the minimum energy have been calculated using quantum chemistry methods. It has turned out that silicon atoms from the substrate are attracted to the interface located on the side of the silicon carbide (SiC) film. The symmetry group of the entire system corresponds to P3m1. The calculations have shown that Si atoms in silicon carbide at the interface, which are the most distant from the Si atoms of the substrate and do not form a chemical bond with them (there are only 12% of them), provide a sharp peak in the density of electronic states near the Fermi energy. As a result, the interface acquires semimetal properties that fully correspond to the ellipsometry data.

Simple and Low-Cost Rotating Analyzer Ellipsometer (RAE) for Wavelength Dependent Optical Constant Characterization of Novel Materials

Simple and low-cost homemade Rotating Analyzer Ellipsometer (RAE) configuration has been developed. Ellipsometer measures the changes of the reflected light polarization of the sample, yielding to the ratio of amplitude (ψ) and phase difference (Δ) between p- and s-polarization. Based on the ψ and Δ values, the dielectric constant of the sample can be extracted. However, the available manufacturer-made ellipsometer is quite expensive and is not a good choice for the student to learn the optical concept since the complexity of its structure could hide the simple optical concept during the measurement. In this work, we have built RAE that constituted of relatively simple components and low-cost as well as simple configuration. Here, we also show the principle of measurement and the ellipsometry data analysis using the optical model related to the system under study Drude-Lorentz model. The calibration of our SE has been done by measuring standard materials in the energy range of 1.5 to 3.3 eV and it was compared to the reference measurement using standard ellipsometer. The result is surprisingly accurate within the error of 5%. This research can be used for studying the several important optical concepts as well as for investigating nanostructured materials.