Studies of NH3 Thermal Nitridation of Ultrathin Si-Oxide Films on Si using Photoemission Spectroscopy with Synchrotron Radiation

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Abstract
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 1.3×10-4 Pa at substrate temperatures from room temperature to 800° C. Nitridation occurs above 800° C, 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+ ( Si n + 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.