Naoto Tate

Initial stage of oxidation of hydrogen-terminated Si(100)-2×1 surface

The initial stage of SiO2/Si interface formation on an atomically flat hydrogen-terminated Si(100)-2×1 surface was studied by X-ray photoelectron spectroscopy. The following results were obtained: 1) the initial stage of interface formation does not depend on the initial surface morphology, 2) the interface layer becomes continuous at the oxide film thickness of 0.5 nm, and 3) at thicknesses greater than this the deviation from an atomically flat interface increases with the progress of oxidation, however, an abrupt compositional transition occurs.

Initial stage of oxidation of hydrogen-terminated silicon surfaces

Abstract Structural changes produced by the oxidation of hydrogen-terminated Si(111)-1 × 1 and Si(100)-2 × 1 surfaces at 300°C in dry oxygen under a pressure of 1 Torr were investigated by X-ray photoelectron spectroscopy (XPS) and multiple internal reflection infrared absorption spectroscopy (MIR-IRAS). Following results are obtained from the analysis and simulation of the experimental results: (1) the layer-by-layer oxidation reaction occurs locally at SiO 2 Si (111) interface, while that does not occur at SiO 2 Si (100) interface, however, (2) the oxidation on Si(100) surface proceeds more uniformly in atomic scale than that on Si(111) surface.

Roughness of Silicon Surface Heated in Hydrogen Ambient

Surface roughness of a silicon wafer heated at 800 to 1100°C under atmospheric pressure in hydrogen ambient is studied. Haze of the surface becomes intense as the heating temperature is decreased. However, haze of the surface does not appear when the native oxide film on the silicon surface is completely removed. Atomic force microscopy images show that the surface heated at 900°C has many small pits whose shapes depend on the crystal plane, that is, squares for the (100) plane and triangles for the (111) plane. The pits are formed due to the difference in the chemical reaction rates between hydrogen-silicon and hydrogen-silicon dioxide. Small areas of bare silicon surface caused by the incomplete removal of the native oxide film are etched by hydrogen gas at a faster rate than the native oxide islands. The behavior of surface roughness with pressure and heating time agrees well with that predicted by the pit formation model in this study.

Gas flow and heat transfer in a pancake chemical vapor deposition reactor

Abstract Gas flow and heat transfer in a pancake reactor for silicon epitaxial film growth are discussed based on a gas flow visualization technique, numerial calculations and a growth rate profile of silicon epitaxial film. In the gas flow visualization, motions of NH4Cl or SiO2 particles are observed using a high-sensitivity analogue camera. The observed gas flow motions are compared with those obtained by three-dimensional calculations of the transport equations of the mass, momentum and energy. At room temperature and the epitaxial growth temperature of 1423 K, a large recirculation in the reactor chamber exists. The gas flow direction near the susceptor at the epitaxial growth temperature is nearly the same as that at room temperature, that is, from the outside toward the center of the susceptor. The profile of the epitaxial film growth rate observed agrees qualitatively with that predicted by visualization and calculations. The gas flow motions near the susceptor in the pancake reactor are parallel to the susceptor, in agreement with that of a horizontal reactor.