Yoshiro Aiba

Surface modification of silicon (111) by annealing at high temperature in hydrogen

A vicinal silicon (111) surface exhibits well defined single steps after being annealed at 1200 °C in hydrogen, which is in sharp contrast with step bunches featuring the surface annealed in argon. As a temporary explanation for its ability to unzip the step bunches, we suggest that hydrogen destroys the faulted triangles of a [112] step, eliminates this kind of step, and eventually leaves the single [112] steps alone behind on the surface.

Outdiffusion of impurity atoms from silicon crystals and its dependence upon the annealing atmosphere

The outdiffusion of boron, antimony, and phosphorus from the bare silicon wafer at 1200 °C, especially its dependence upon the annealing atmosphere, has been studied with spreading resistance and secondary ion mass spectroscopy (SIMS). It is found that the boron outdiffusion proceeds when the crystal is annealed in hydrogen, but is completely suppressed in argon even if the doping concentration is as high as 3×1018 cm−3 and the annealing time is as long as 2 h. The dramatic dependence upon the atmosphere has not been observed for the other impurities and is temporarily related with the desorption process of boron atoms from the surface.

Atomic steps on a silicon (001) surface tilted toward an arbitrary direction

In this letter, we show that the misorientation of a vicinal (001) surface annealed in hydrogen is accommodated by a pair of near‐Sa steps which are evolved in two perpendicular {110} independently and coordinately. We demonstrate that the deviation of surface orientation in a tiny area can be readily evaluated by inspecting the local variation of the near‐Sa step pair. We finally indicate that the atomic steps on a surface annealed in argon exhibit in contrast, no conformity with the misorientation towards an azimuth other than {110}.

Determination of silicon evaporation rate at 1200 °C in hydrogen

Separation by implanted oxygen silicon wafers have been investigated with cross‐sectional transmission electron microscopy after annealing at 1200 °C in argon as well as in hydrogen. It is observed that the buried oxide has experienced little change in the thickness, which is ascribed to the low hydrogen solubility in the crystal (about 3×1015 cm−3) and provides a natural mark to measure the thickness variation of the top silicon directly. The evaporation rate as determined in this method is less than 0.1 nm/min with an accuracy of ±0.1 nm/min, at least two orders of magnitude lower than reported in previous investigations.

Nondestructive Observation of Depths and Dimensions of Subsurface Microdefects in Czochralski-Grown and Epitaxial Silicon Wafers

Evaluation of the depths and dimensions of microdefects are nondestructively studied in the subsurface region of Czochralski-grown and epitaxial silicon wafers, using a new short wavelength laser scattering tomography which was proposed in our previous paper. It has been shown experimentally that the method is capable of observing the depths and dimensions of microdefects in the subsurface region and that of their densities of silicon wafers. From these results, depth profile of size distributions of detected subsurface defects have been obtained. For epitaxial wafers, distinct boundaries between their epitaxial layers and substrates are successfully detected.

A novel configuration of atomic steps observed on vicinal silicon (100) surface annealed in a hydrogen atmosphere

Abstract The vicinal silicon (100) surface with a misorientation of 0.05° towards [011] and [001] has been investigated with atomic force microscopy after annealing at 1200°C in argon and hydrogen. For the samples tilted towards [011], while the surfaces annealed in argon are featured with the alternate smooth and rough steps of monolayer height (S steps), which unambiguously correlate themselves with the so-called (Sa + Sb) structure, the hydrogen annealing, in contrast, generates a configuration of orthogonal S steps. Through an analysis of the surface tilted towards [001], we show that a miscut toward an arbitrary direction can be accommodated by two identical S steps developed independently along two perpendicular {011} axes if the crystal is annealed in hydrogen. On the contrary, a surface annealed in argon shows no conformability with the misorientation towards an axis other than {011}. It is believed that the formation of the orthogonal S steps is a chemically driven process resulting from the rela...