Low-Temperature Growth of Thin Silicon Nitride Film by Electron Cyclotron Resonance Plasma Irradiation

An amorphous silicon nitride thin film has been fabricated by electron cyclotron resonance plasma irradiation. The growth of the film is carried out by Ar/N₂ mixed plasma irradiation at a low temperature of 400°C. It is found that nitrogen partial pressure decisively affects film quality. A SiN film having a structure nearest to stoichiometric construction is obtained by precisely controlling the N² mixing ratio at 60%. This implies that the existence of Ar with a suitable partial pressure increases the nitrogen radical concentration in the Ar/N₂ mixed plasma. Under optimum conditions, the as-grown SiN film shows a leakage current more than two orders of magnitude lower than that of thermally grown SiO₂ having the same equivalent oxide thickness. A high-resolution transmission electron micrograph shows an atomically flat interface of the Si substrate and SiN film.