Abstract
It has been found that 
can be converted directly to silicon nitride or oxynitride at the surface of 
films by heating oxidized silicon wafers in anhydrous ammonia gas. At temperatures above 900°C, nitrided 
films have graded composites with respect to their nitrogen fraction. This analysis was performed by AES, infrared transmittance spectroscopy, and etch‐rate profiles. Nitrided surface regions on 
films, in which the nitride fraction ranged from 10% to 50%, showed remarkable masking effects against subsequent oxidation at high temperatures.