Structural, Morphological, and Optical Characteristics of RF Sputtered Silicon Nitride: Role of Film Thickness and Post-Annealing Temperature

Silicon nitride (Si3N4) films are valued for their exceptional properties, making them a key focus in industrial and scientific research. Si3N4 films of thicknesses 200,400, 600 nm are deposited on Si substrate using radio-frequency (RF) sputtering and then annealed for one hour at temperatures of 1000 & 1200 degrees C in nitrogen atmosphere. The alterations in structural, morphological and optical characteristics are assessed. Raman Spectroscopy reveals nonlinear variation in Full width at half maximum (FWHM) of the Si3N4 peaks with annealing temperature and thickness reflecting changes in crystallinity of films. AFM analysis shows nonlinear roughness and particle size behavior with annealing temperature while linear trend with thickness. Field emission scanning electron microscopy (FESEM) reveals the uniformity of all films. Spectroscopic Ellipsometry (SE) reveals that refractive index shows a similar trend as FWHM with annealing temperatures and increases with an increase in film thickness. Films shows multiple optical energy gaps which may be attributed to the introduction of defects related states. Photoluminescence (PL) study confirms the presence of these defect related states in films. These findings underscore the tunability of Si3N4 film properties through precise control of annealing temperature and thickness, making them highly adaptable for wide applications including optoelectronics and protective coatings.