STM observation of hydrogen-terminated Si(111) surface in air and theoretical analyses of its reaction with O_3 and H_2O

摘要

Recently, the integration of LSI becomes very high, and the device elements become minute. SiO_2 thin film is used as a gate insulator in ultra fine silcion-based transistors, and the quality control of SiO_2 layers becomes increasingly important in the silicon devices. The Si/SiO_2 interface must be smooth on the atomic level in these devices. It is reported that an ammonium flouoride solution colud etch away surface roughness on Si(111) and produce atomically flat surfaces over a large area. [1] However, it is not yet clarifies well how atomic structure of the surface is arranged in air and hydrogen-terminated Si surface is oxidized at the initial stage. So, we have tried to elucidate the surface structure in the air and initial oxidation by combining scanning tunneling microscope (STM) observation with quantum-chemical calculations.