Optical and physical properties of sputtered Si:Al:O:N films

Mechanical and optical properties and structural characteristics are described for Si:N films with Al and O additions (Si_xAl_1−xO_yN_1−y) deposited by reactive RF diode sputtering on Si and SiO₂ substrates. The thermal and intrinsic stress components, elastic stiffness, coefficient of thermal expansion (CTE), and refractive index were measured for films ranging in thickness from ∼2 μm to 50 μm. Some structural and microstructural data were obtained using x-ray diffraction, optical and scanning-electron microscopy, and surface profilometry. Alloying Si:N with Al to form Si:Al:N greatly reduced the compressive intrinsic and total stress found in pure Si:N films on Si. Addition of O to the Si:Al:N moderately increased the intrinsic stress, decreased the elastic stiffness, and produced a smoother, more glassy (amorphous) film.