Investigation on optical and physico-chemical properties of LPCVD SiO_xN_ythin films

Abstract

In this work, the correlation between BEMA model and FTIR analysis was employed to investigate the chemical composition of silicon oxynitride (SiOxNy) films deposited by low pressure chemical vapour deposition (LPCVD) technique at temperature of 850 0 C from nitrous oxide N2O, ammonia NH3 and dichlorosilane SiH2C12. Different stoichiometries were obtained for different values of relative gas flow ratio NH3/N2O while keeping the SiH2Cl2 flow constant. The optical properties were studied using spectroscopic ellipsometry. Apart from films thickness, their refractive index as well as their SiO2 and Si3N4 volume fractions were deduced using the Bruggeman effective medium approximation (BEMA) model. It was found that the refractive index increases from 1.45 to 1.60 with increasing nitrogen incorporation. The Fourier Transform Infrared spectroscopy was carried out to study the evolution of chemical bonding of LPCVD SiOxNy films. In order to improve the qualitative analysis of their SiN and Si-O vibrational modes, a correlation between Fourier transform infrared and spectroscopic ellipsometry measurements was established. A shift of infrared peaks position with the increase of relative gas flow ratio is observed. Furthermore, the calculated areas of absorption bands were used to estimate the SiOxNy stoichiometry. This quantitative analysis was proved with an adequate method in the literature. We found a decrease of x values from 1.94 to 1.26 and an increase of y from 0.04 to 0.49, when the NH3/N2O gas flow ratio increases. This behavior was explained by the increase of nitrogen content as well as the decrease of oxygen content in the SiOxNy film.

An innovative GC-MS, NMR and ESR combined, gas-phase investigation during chemical vapor deposition of silicon oxynitrides films from tris(dimethylsilyl)amine

“…TDMSA is selected given the presence of the desired Si-N and Si-H bonds, while avoiding Si-O ones. Compared to conventional precursors used in CVD of Si3N4 and SiOxNy, such as silane (SiH4) 7,8 and dimethyldichlorosilane (SiCl2(CH3)2), 19,20 it presents lower handling risks and by-passes the production of ammonium chloride encountered during deposition using chlorosilanes. However, it is a complex molecule with a large number of bonds; the silicon atoms are involved in a tertiary amine, from which many plausible decomposition pathways and products are expected.…”

“…The chemical structure of all identified compounds is generated by Avogadro version 1. 20, an opensource molecular builder and visualization tool. 34…”

A Review: Preparation, Performance, and Applications of Silicon Oxynitride Film

“…It has the advantages of structural integrity, few pinhole defects, and high deposition rate, therefore it is suitable for large-area production [80]. Kaghouche et al [81] deposited a SiN x O y film on a single crystal silicon wafer using LPCVD at a high temperature of 850 °C with N 2 O, NH 3 and dichlorosilane (SiH 2 Cl 2 ) as precursor gases. In the synthesis, the control variable experiment is carried out by adjusting the flow ratio of NH 3 /N 2 O via keeping the flow rate of SiH 2 Cl 2 as constant.…”

An innovative kinetic model allowing insight in the moderate temperature chemical vapor deposition of silicon oxynitride films from tris(dimethylsilyl)amine

“…Existing thermal CVD routes that form SiOxNy thin films classically involve silane or chlorosilane precursors, often mixed with NH3 and N2O. These processes operate at deposition temperatures higher than 700°C [12][13][14], which drastically limits their application on heat sensitive substrates.…”