Characterization of amorphous silicon carbide thin films recrystallization

The peculiar feature that nowadays accompanies our society, and consequently our lives, is definitely the technological progress in all kinds of sectors. The utilisation of innovative materials is an important step in evolution though the optimal exploitation of their properties in specific applications. Clearly, this is made possible by developments in the technological and production processes inherent in this major field of research. Among the modern semiconductor materials, silicon carbide (SiC) certainly plays an important role due to its unique chemical, physical and mechanical properties, making it ideal for various fields of application. However, the high cost of producing this material nowadays severely limits its use. Scientific research is moving towards finding solutions to solve, or at least minimise, this challenge; the idea developed in this work, is to deposit silicon carbide at lower temperatures (300°C, 500°C and 750°C) than conventional processes. In particular, a thin film of amorphous SiC is deposited by means of PECVD and PVD sputtering techniques, followed by a recrystallisation heat treatment (T>1100°C). In the PECVD-deposited samples are encountered adhesion bonding problems between the SiC and SiO2 layers, while using the XRD analysis it is possible to demonstrate a partial recrystallisation of the PVD-deposited ones in the SiC-3C crystalline phase. Experimental measurements such as ellipsometry, Raman spectroscopy and XPS are carried out, both after deposition and after the heat treatments have been carried out, to determine the properties and fully study the evolution of each individual specimen. Combining the analysis of Raman spectroscopy and XPS results reveals a particular organisation of the atoms within the amorphous layer of silicon carbide. In particular, there is a significant presence of C-C bonds, suggesting inhomogeneity within the film. The absence of a long-range crystalline structure could be described by the presence of two different phases: one containing carbon and one Si-rich silicon carbide. Moreover, in-situ measurements of curvature and reflectance are performed during lower temperature heat treatments (T<1100°C) to detect the possible occurrence of particular phenomena. This work takes its cue from the European SiComb project which aims at the realisation of an ultra-broadband frequency comb on a chip made of SiC, exploiting its unique optical properties such as the wide band gap.