ULTRATHIN SILICON-NITRIDE FILMS PREPARED BY COMBINING RAPID THERMAL NITRIDATION WITH LOW-PRESSURE CHEMICAL VAPOR-DEPOSITION

Ultrathin silicon nitride films were prepared using rapid thermal nitridation prior to low-pressure chemical vapor deposition (RTN + LPCVD). The low-field leakage current of the 4.5-nm-thick film was found to be significantly reduced to a value of 10(-8) A/cm2 at 4 MV/cm. Additionally, the time needed for 50% of the films to show dielectric failures was extended by about 20 times, relative to conventional LPCVD silicon nitride films. These improvements in electrical characteristics may be attributed to the low interface oxygen concentration as determined by secondary-ion mass spectroscopy and x-ray photoelectron spectroscopy. The RTN + LPCVD films are very suitable for use in future dynamic-random-access memories.