Aki Tosaka

Reaction analysis of initial oxidation of silicon by UV-light-excited ozone and the application to rapid and uniform SiO2 film growth

UV-light-excited O3 prepared by irradiation of nearly 100% pure O3 with a KrF excimer laser (λ=248nm, irradiated area=30×10mm2) was utilized for low-temperature Si oxidation. The initial oxidation rate was determined, and the activation energy was shown to be almost zero (0.049eV). To clarify the optimum oxidation conditions, the dependence of the SiO2 film growth rate on the total photon number and the photon density was investigated. The evolution of O3 density after UV-light irradiation was experimentally measured, and the O(D1) density change is discussed. O(D1) density changes are successfully explained by using a second-order reaction model, indicating that a pulse supply of oxygen atoms is essential in the initial oxidation process. The uniform oxidation of 8in. Si wafer has been carried out using a wafer-transfer type chamber by irradiating the wafer with KrF excimer laser light expanded linearly to the wafer width by a concave lens.

Strain induced intermixing of Ge atoms in Si epitaxial layer on Ge(111)

The relationship between strain and effective mass of the √3 × √3-Ag structure surface metallic state, when formed on strained Si(111) layers on Ge(111), has been investigated by angle resolved photoelectron spectroscopy at various film thicknesses. Si layer lattice spacing expands and effective mass decreases at film thickness greater than 2 bilayers. This result is inconsistent with a previous study showing increasing effective mass with tensile strain for the √3 × √3-Ag structure. Ge-3d core level photoelectron spectra confirm that this disparity is caused by the intermixing of Ge atoms in the Si layer. The relationship between effective mass and strain is useful for gauging intermixing, and the effective mass of surface metallic states is useful for gauging nanoscale strain.

Development of Wide Ion Beam Profile Measurement Method for a Period-by-Period Extreme Ultraviolet Multilayer Milling System

To develop an ion milling system for multilayer mirrors in the extreme ultraviolet (EUV) wavelength region, the current density profile of a 100-mm-ion beam has been measured by plural methods. The profile has been measured indirectly via milling thickness by an optical surface profiler (WYKO TOPO-2D) and an X-ray diffractometer. Direct current detection by a commercial Faraday cup and a newly developed array electrode sensor was also performed. These methods were compared and evaluated in terms of their experimental results. It was demonstrated that our array electrode sensor is useful for observing a wide ion beam profile with reasonable accuracy.