Effect of plasma power on growth process, chemical structure, and properties of PECVD films produced from hexamethyldisilane and ammonia

Silicon carbonitride films were grown by plasma enhanced chemical vapor deposition (PECVD) using hexamethyldisilane (HMDS) and ammonia initial gas mixture at deposition temperature of 300 degrees C. The elemental composition, growth rate, hardness, dielectric constant, and refractive index values of the SiCN:H thin films were analyzed as function of plasma power ranging from 10 to 80 W. In-situ analysis of gas phase performed by optical emission spectroscopy (OES) revealed the presence of H2, 2 , H, CH, and CN particles. Concentration trends of H and CH particles under plasma power variation were determined using an actinometry technique. Fourier-transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), energy-dispersive X-ray analysis (EDX) confirmed the effective incorporation of nitrogen at the level of 20 at.% through formation of Si-N, - N, N-H, - H, and C-N - N bonds. The ratios of Si/C and Si/N, and surrounding of Si, C, and N atoms analyzed by XPS did not change with rise of plasma power, while the hydrogen content in films, mainly involved in CHx x fragments, decreased. The films with hardness of 5.0-8.1 GPa, refractive index of 1.64-1.76, and dielectric constant of 4.1-5.1 were synthesized by varying the experimental conditions. The ellipsometric porosimetry (EP) shows the absence of a porous structure. Analysis of annealed Cu/SiCN:H/Si(100) structure by transmission electron microscopy (TEM) showed clear interfaces of SiCN:H with both the Cu layer and the Si(100) substrate. No noticeable diffusion of copper through dielectric layer was detected. The aging of films during storage under environmental conditions was studied. It was shown that the most stable film was obtained using 80 W plasma power, and had a composition of Si 0.3 C 0.5 N 0.2 :H.