Silicon nitride is barely oxidized in dry or even steam ambients at elevated (1100 degrees C) temperatures. We have observed and studied the chemically enhanced oxidation of silicon nitride films from a variety of sources, that occurs at temperatures below 1050 degrees C. The addition of several hundred pans per million of an additive like NF3 to the dry O-2 accomplishes this rapid oxidation independent of the Si3N4 films used whether plasma, low pressure, or high temperature chemical vapor deposition is used. The resultant oxidized films etch steadily in dilute HF (100:1) at the rate of tens of nanometers per minute. The oxidation rate observed is faster below 950 degrees C and above this "transition temperature" an incubation period is observed prior to the film conversion. This incubation period becomes longer the higher the temperature, so that at 1050 degrees C, it is of the order of 4 h. Analytic techniques such as X-ray photoelectron spectroscopy and Fourier transform infrared and electron energy loss spectroscopy were used to determine the composition of the convened film and to gain insight into the possible reactions occurring in this process. This process can be used as an alternative to the plasma or phosphoric acid etching of nitride masking films.