A molecular beam apparatus has been constructed to investigate the oxidation dynamics of Si(100) surface with O_3, which is a promising oxidizing species to reduce the thermal budget during SiO_2 film formation for gate oxide in semiconductor devices. With the surface exposed to the modulated molecular beam, time-resolved measurements of product molecules desorbing from the surface give us a clear understanding of the reaction dynamics. As the first step of our study, the active oxidation of Si(100) surface with O_2 was investigated employing molecular beam relaxation spectrometry to check the performance of the apparatus. The Fourier analysis of product waveforms indicated that the reaction can be described by the sequential two-step first-order reaction process. The activation energy of each step agreed with the values in literatures.
