Fabrication and characterization of atomic-step-free silicon/oxide interface by controlling step arrangement

点击翻译按钮获取中文摘要

We investigated the step dynamics on Si surfaces, the characterization method of Si/SiO_2 interface roughness by scanning tunneling microscopy (STM), and roughening of Si/SiO_2 interface during oxidations, in order to realize atomically flat and step free Si/SiO_2 interfaces. First, using high temperature STM, we studied the step dynamics during faceting transformation on vicinal Si(113) surfaces. We clarified the driving forces for step motion which causes considerable morphological changes in mesoscopic scale. We could interpret the observed coarsening of a step network in faceting transformation based on the continuum step model. We performed numerical simulations of a step network, demonstrating that the continuum step model can reproduce quantitatively the evolution of complicated step configurations. Second, we developed the characterization method of Si/SiO_2 interface roughness in sub-nanometer scale, using ultrahigh vacuum STM. We achieved STM observation of the interface morphology with atomic resolution, removing the SiO_2 overlayer by irradiating a field emission electron beam extracted from a STM tip at elevated temperatures. Using this method, we evaluated the interface roughness for chemical oxides formed by a wet chemical process and thermal oxides from semiconductor industrial processes. We showed that the wet chemical process roughen the interface morphology and the interface roughness of the thermal oxides is determined by the processes prior to the oxidation. Overall results obtained through this research indicate that control of the atomic steps on Si substrates to form atomically flat substrates is crucial, for fabrication of atomically flat Si/SiO_2 interfaces.