Structural and mechanical properties of amorphous silicon carbonitride films prepared by vapor-transport chemical vapor deposition

Abstract

The deposition of amorphous silicon carbonitride (a-SiCN:H) films has been successfully achieved through an in-house developed vapor-transport chemical vapor deposition (VT-CVD) technique in a nitrogenated atmosphere. Polydimethylsilane (PDMS) was used as a single-source precursor for both silicon and carbon, while NH 3 was mixed with argon to ensure the in-situ nitrogenation of the films. The chemical bonding and the atomic composition of the a-SiCN:H films were systematically investigated, as a function of their N content, by means of Fourier transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS). AFM was used to obtain 2-D and 3-D views of the films. The mechanical properties [(hardness ( H) and Young's modulus ( E)] of the freshly prepared films were investigated by the nanoindentation technique. It is shown that by controlling the NH 3/Ar gas flow ratio in the reactor, a-SiCN:H films with various N contents [(0–27) at.% range] are achieved. On the microstructural level, the increase incorporation of N in the a-SiCN:H films is found not only to lead to C atom substitution by N atoms in the local Si–C–N environment but also to an enhanced incorporation of hydrogen bonded to both Si and N. Furthermore, the increase incorporation of N in the a-SiCN:H films resulted in an increase of the average R rms surface roughness from 4 to 12 nm. Moreover, the films became porous with pore size and density increase as a result of increasing N at.%. Ultimately, both H and E of the a-SiCN:H films were found to be sensitive to their N content, as they decrease (from ~ 17 GPa and 160 GPa to ~ 13 GPa and 136 GPa, respectively) when the N content is increased from 0 to 27 at.%. The formation of Si–N, Si–H, and N–H bonds at the detriment of the more stiff Si–C bonds is thought to account for the observed lowering of the mechanical properties of the a-SiCN:H films as their N content increased.