Effects of Silicon-Rich Silicon Nitride on Morphology of LOCOS

The effects of the silicon-rich silicon nitride film on the morphology of LOCOS were investigated. Silicon nitride films were prepared by CVD with volume ratios of NH3 to SiH4 of 1.5, 9, 90, and 450. The silicon-rich silicon nitride film is also effective as a mask against field oxidation. The silicon-rich silicon nitride film is tolerant to tensile stress during field oxidation, and it reduces the length of the bird’s beak. These effects of the silicon-rich silicon nitride film on the morphology of LOCOS are due to its higher viscosity than the stoichiometric silicon nitride film.