Silicon carbonitride films as new materials obtained by plasma chemical vapor deposition from novel precursor

摘要

Silicon carbonitride films were synthesised by RP CVD process using the novel single-source precursor that is derivative of 1,1-dimethylhydrazine, (CH_3)_2HSiNHN(CH_3)_2. The films were characterised by X-ray photoelectron (XPS), infrared (FT1R) and ultraviolet (UV) spectroscopy. The microstructure of the films was examined by scanning electron microscopy (SEM) and diffraction of synchrotron radiation (DSR) methods. XPS and FT-IR spectroscopy studies showed that the Si-C and Si-N are the main bonds in the deposited films. Concerning the C-N bonds, the results are less obvious: they are either negligible or not present at all. The films were found to be predominately amorphous with a number of crystallites within the unstructured matrix. The crystals appearance, their dimensions and crystal form did not depend on substrate temperature. We hypothesised that crystallisation could happen in the gas phase during deposition or nanocrystals were formed by the strain induced after a certain thickness of the amorphous film. The crystals were assigned to the structure closed to a-Si_3N_4 phase. According to FTIR and XPS data it is clear that the chemical bonding and the atomic local order in the amorphous matrix are much more complicated than those of Si_3N_4-SiC mixtures. We concluded that tetrahedral configurations of silicon carbide and silicon nitride units with mixed C/N environment are hypothetically formed. The films are highly resistant to thermal degradation. It was also demonstrated that this new material has a band gap that was variable from 2.0 eV to 4.7 eV.