Effects of silicon-rich silicon nitride on morphology of LOCOS

The effects of the silicon-rich silicon nitride film on the morphology of L OCOS were investigated. Silicon nitride films were prepared by CVD with vol ume 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 silic on-rich silicon nitride film is tolerant to tensile stress during field oxi dation, 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.