Structure-Property Relationships of Amorphous Hydrogenated Silicon-Carbon Films Produced by Atomic Hydrogen-Induced CVD from a Single-Source Precursor

Abstract

Amorphous hydrogenated silicon–carbon (a-Si:C:H) films were produced by atomic hydrogen–induced (AH) CVD using hexamethyldisilane (HMDS) as a single-source precursor. Radio frequency (rf) hydrogen plasma was the source of atomic hydrogen. The effect of substrate temperature (Ts) on the chemical structure, composition, surface morphology, mechanical properties (dynamic hardness, total stress), and optical properties (refractive index, optical bandgap) of a-Si:C:H film has been examined. Fourier transform infrared (FTIR) spectroscopy and Auger electron spectroscopy (AES) data revealed a drastic drop in hydrogen content in the film, and a rise of the atomic concentration ratio Si/C with increasing Ts, thus accounting for the elimination of organic moieties from the film and the formation of a Si–carbidic structure. In the light of scanning electron microscopy (SEM) and atomic force microscopy (AFM) examinations, the films were found to be morphologically homogeneous materials with a maximum size of surface roughness not exceeding 2 nm at Ts = 300 °C. Both hardness and stress (tensile in nature) are strongly affected by the film composition, their values increasing with rising atomic ratio Si/C. The investigated optical properties of a-Si:C:H film, i.e., refractive index (n) and optical bandgap (E0), can be controlled by the atomic ratio Si/C for a wide range of values: n = 1.58–2.02 and E0 = 2.3–3.2 eV.