Structures and properties of the SiNC films on Si wafer at different deposition stages

The films were deposited on Si wafer by a microwave plasma chemical vapor deposition (MPCVD) system with CH4, N2, up to 8.3 vol.% H2 and additional Si chips as the sources. The films were examined at different deposition times to explore different growth stages of deposition. Examination indicated the deposition can be roughly divided up to three stages, depending on deposition time and based on their structure and property. In the early deposition stages, the films consist of two layers, i.e. Si-oxide and SiNC layers. The SiNC layer consists essentially of nano-crystals embedded in ternary SiNC amorphous matrix with crystal structure close to SiC. In contrast, in the later stage, the films are further covered by a layer of the binary SiN crystalline phases with crystal structures much closer to α-Si3N4 than β-Si3N4 and tetragonal Si3N4 type structures. The band gaps, as revealed by CL (cathodoluminescence) spectra, are ∼3.88 eV (320 nm) for SiN layer and ∼2.82 eV (440 nm) for SiNC layer. Depending on the deposition conditions, the growth competitions among SiC, Si-N and SiNC crystalline phases may result in different morphologies, compositions and properties of the films.