Optical Characterization of Non-Stoichiometric Silicon Nitride Films Exhibiting Combined Defects

Abstract

The study was devoted to optical characterization of non-stoichiometric silicon nitride films prepared by reactive magnetron sputtering in argon-nitrogen atmosphere onto cold (unheated) substrates. It was found that these films exhibit the combination of three defects: optical inhomogeneity (refractive index profile across the films), uniaxial anisotropy with the optical axis perpendicular to the boundaries and random roughness of the upper boundaries. The influence of the uniaxial anisotropy was included into the corresponding formulae of the optical quantities using the matrix formalism and the approximation of the inhomogeneous layer by a multilayer system consisting of large number thin homogeneous layers. The random roughness was described using the scalar diffraction theory. The processing of the experimental data was performed using the multi-sample modification of the least-squares method, in which experimental data of several samples differing in thickness were processed simultaneously. The dielectric response of the silicon nitride films was modeled using the modification of the universal dispersion model, which takes into account absorption processes corresponding to valence-to-conduction band electron transitions, excitonic effects and Urbach tail. The spectroscopic reflectometric and ellipsometric measurements were supplemented by measuring the uniformity of the samples using imaging spectroscopic reflectometry.

Optics of Inhomogeneous Thin Films with Defects: Application to Optical Characterization

“…In paper [66] the optical characterization of inhomogeneous thin films of SiN x and SiO x C y H z containing transition layers at their lower boundaries is performed. In paper [67] inhomogeneous thin films of SiN x with random roughness of the upper boundaries and unwanted uniaxial anisotropy are characterized. In paper [68] the complete optical characterization of SiO x C y H z thin films exhibiting transition layers at the lower boundaries and wedge-shaped thickness nonuniformity is carried out.…”

Review—Silicon Nitride and Silicon Nitride-Rich Thin Film Technologies: State-of-the-Art Processing Technologies, Properties, and Applications

“…74 • An antireflection coating in solar cells and passivation layer/ mask to protect from local oxidation of Si surfaces in optical waveguides. 75 2. Electrochemical impedance spectroscopy (EIS) and transmission electron microscopy (TEM) analyses of glass/SiN x /NiCr/Au/SiNx stacks was carried out to analyze through-porosity in SiN x coatings.…”

“…As presented in Appendix D, the films deposited for antireflection coating applications are non-stoichiometric SiN x , and exhibit a mixture of three types of defects: (i) optical inhomogeneity (as determined by the refractive index profile across the films); (ii) uniaxial anisotropy with a perpendicular optical axis to the boundaries; and (iii) random roughness of the upper boundaries. 75 Tailored Surface Modification Methods of SiN x…”

“…Vohánka et al75 ECS Journal of Solid State Science and Technology, 2020 9 063006 x NPNs coated with stable organic molecules to enhance functionality without reducing permeability and size selectivity Li et al80 AqueousChemical modification through covalentbonding of hydrophilic, positively charged molecules on the interior nanopore surface DNA sequencing and single-molecule measurement of nanoparticles, biomolecules such as bacteria, protein, antibodies, nucleic acids Single-nanometer-scale SiN x pores the detection, identification, and characterization of analytes Yin et al81 …”

Optical quantities of a multilayer system with randomly rough boundaries and uniaxial anisotropic media calculated using the Rayleigh–Rice theory and Yeh matrix formalism

“…It should be noted that one can encounter with combinations of the defects mentioned above. For example, the combination of the defects consisting in boundary roughness, optical inhomogeneity and uniaxial anisotropy was found at the optical characterization of thin films consisting of non-stoichiometric silicon nitride in paper [53]. In this paper inhomogeneity of these films was approximated by a large number of thin anisotropic and homogeneous layers and the random roughness was described using the SDT.…”