The thermal stability of nitrogen-rich amorphous carbon nitride films (N/C greater than or equal to 1) is investigated from room temperature up to 600 degreesC. The films were deposited by three different methods, namely pulsed laser deposition (PLD), inductively coupled plasma chemical vapour deposition (ICP-CVD) with gaseous precursors, and ICP-CVD utilizing transport reactions. As-deposited and annealed films were characterized with respect to their thickness, composition and bonding structure by a variety of methods including wavelength dispersive X-ray analysis (WDX), Auger electron spectroscopy (AES), X-ray photoelectron spectroscopy (XPS), Raman spectroscopy and Fourier transform infrared spectroscopy (FTIR). Annealing at 200 degreesC leads to desorption of surface contaminants while in the range between 200 and 400 degreesC a significant densification is observed. Above 400 degreesC a drastic loss of film material, especially nitrogen-rich groups, sets on, leading to the total destruction of the films at 600-700 degreesC. These observations are compared with the annealing behaviour of films with lower nitrogen content.