A Comparative Study of the Physical Properties of SiN Thin Films Deposited by LPCVD, PECVD, and Reactive Sputtering for Photonic Device Integration

This paper presents a comparative study of the physical properties of silicon nitride (SiNx) thin films deposited using Low-Pressure Chemical Vapor Deposition (LPCVD), Plasma-Enhanced Chemical Vapor Deposition (PECVD), and Reactive Sputtering Deposition (RSD). LPCVD films exhibit minimal surface roughness and excellent uniformity across 4-inch wafers but suffer from high tensile stress (~1 GPa), leading to cracking beyond 400 nm in thickness. In contrast, PECVD and RSD enable crack-free deposition up to 800 nm, and potentially beyond. albeit with higher surface roughness and reduced uniformity. The choice of deposition technique must therefore balance uniformity, surface roughness, optical properties and mechanical stress, depending on the target photonic application.