Phase composition of thin silicon carbonitride films obtained by plazma endanced chemical vapour deposition using organosilicon compounds

Abstract

High-temperature silicon carbonitride films are synthesized by plasma decomposition of gas mixtures of 1,1,1,3,3,3-hexamethyldisilazane (HMDS) (the synonym used by IUPAC bis(trimethylsilyl) amine) with ammonia or helium in the temperature range of 673–1273 K. It is shown that silicon carbonitride films, obtained in high temperature processes of the plasma decomposition of organosilicon compounds, are nanocomposite. In their amorphous matrix the crystals belonging to the phases of the α-Si3−nCnN4 family and impurity graphite are embedded. To clarify the previously obtained data by means of the X-ray diffractometry using synchrotron radiation, they are compared with the published results of modeling the structure of these phases. It is shown that nanocrystals belonging to the phases of α-Si3N4, α-Si2CN4, α-SiC2N4, and α-C3N4 are present in the films. An increase in the ammonia concentration in the initial gas mixture causes a decrease in the film hardness from 24 GPa to 16 GPa due to the increased content of α-Si3N4 and α-Si2CN4 nanocrystals having a lower hardness compared to α-C3N4 and α-SiC2N4.