Very Thin Silicon Nitride Films Grown by Direct Thermal Reaction with Nitrogen

Very thin uniform silicon nitride films less than 100Å have been obtained on silicon wafers by direct thermal reaction with nitrogen at temperatures ranging from 1200° to 1300°C. Small amounts of water or oxygen in reaction mixture caused vapor etching which gave rise to local crystallization. By eliminating both from the reaction ambient to less than 1 ppm, amorphous silicon nitride films can be deposited. These films have been found to have properties similar to those of CVD by investigations of Auger electron spectroscopy, infrared spectroscopy, and ellipsometry. Remarkable masking effects of the films against oxidation and phosphorus diffusion have been found.