This paper describes the analysis of integrated optical waveguides using Finite-Difference Time-Domain (FDTD) method, and proposes the design methodology for low loss waveguide components: corner bends and branches. In order to integrate optical waveguides with Si VLSI technologies on a chip, the compact bends or branches are necessary. Since the optical power radiation from a bend or a branch point depends on the waveguide shapes, an accurate analysis of guided wave behavior is required. For the purpose we adopted the FDTD method which can analyze optical waveguides with a large variation of refractive index and arbitrary shape. Proposed design concept is to have all waveguides transmit only the fundamental mode and to design whole waveguides based on the fundamental mode transfer characteristics. For this design concept, waveguide components are required to have not only low radiation loss but also a little mode shift from the fundamental mode. The bend using the double-reflection mirrors and the branch using a slit are proposed for suppressing the mode shift and improving radiation loss. By the FDTD analysis, the following results have been obtained. The radiation loss and mode shift of double reflection bend are 1% and 4%, and those of the slit branch are 2% and 5%, respectively, in 2 µm width waveguide.

Systems for removing particulates and gaseous contaminants using the UV/photoelectron method under atmospheric and low pressure conditions have been investigated and its availability has been demonstrated. From experimental results, more than 90 % of particulate contaminants are removed by this method under atomospheric and low pressure conditions. This method can be used to design superclean spaces for wafer stockers, and wafer delivering systems in the LSI fabrication process.

Hydrogen termination of HF-treated Si surfaces and the oxidation kinetics have been studied by x-ray photoelectron spectroscopy (XPS) and Fourier Transform Infrared Spectroscopy (FT-IR) Attenuated Total Reflection (ATR). The oxidation of hydrogen-terminated Si in air or in pure water proceeds parallel to the surface presumably from step edges, resulting in the layer-by-layer oxidation. The oxide gryowth rate on an Si(100) surface is faster than (110) and (111) when the wafer is stored in pure water. This is interpreted in terms of the steric hindrance against molecular oxygen penetration throughth the (110) and (111) surfaces where the atom void size is equal to or smaller than O2 molecule. The oxide growth rate in pure water for heavily doped n-type Si is significantly high compared to that of heavily doped p-type Si. This is explained by the conduction electron tunneling from Si to absorbed O2 molecule to form the O2- state. O2- ions easily decompose and induce the surface electric field, enhancing the oxidation rate. It is found that the oxidation of heavily doped n-type Si in pure water is effectively suppressed by adding a small amount (1003600 ppm) of HCl.