Studies of NH3 thermal nitridation of ultrathin Si-oxide films on Si using photoemission spectroscopy with synchrotron radiation

The NH3 thermal nitridation process of ultrathin Si-oxide films on a Si(100) substrate has been investigated by in situ X-ray photoelectron spectroscopy using synchrotron radiation. Silicon oxide films with a thickness of about 0.7 nm are exposed to NH3 gas at 1.3x10-4 Pa at substrate temperatures from room temperature to 800degC. Nitridation occurs above 800degC, which is the desorption temperature of Si oxides. In the initial stage of nitridation, the Si substrate near the interface is nitrided and the nitridation components of Si1+-Si4+(Sin+ means the chemical bonding state bonded to n nitrogen atoms) are generated. The number of Si4+ component increases as the thickness of the nitrided film increases, and when the Si-nitride films are 1 nm thick, it contains no oxygen atoms. (author)