Hidenobu Abe

Low‐Temperature Out‐Diffusion of Cu from Silicon Wafers

We investigated low temperature out-diffusion of Cu impurity from the bulk of p- and n-type silicon wafers after contamination followed by diffusion of Cu into silicon during annealing. We show that Cu impurity in the bulk after low-temperature out-diffusion can be measured at the surface by total x-ray fluorescence and graphite furnace atomic absorption spectroscopy 10 10 atom/cm 3 . In addition, a benefit of low-temperature annealing is the removal of Cu contamination from the bulk by surface cleaning. We also find that Cu contamination in the bulk of p-type Si wafers out-diffuses at room temperature after removing the surface oxide, but this does not happen in the case of n-type Si material.

Calculation of Diffusion Component of Leakage Current in pn Junctions Formed in Various Types of Silicon Wafers (Intrinsic Gettering, Epitaxial, Silicon on Insulator)

We derived a general analytical formula for the diffusion component of leakage current in pn junctions formed in various types of silicon wafers such as intrinsic gettering (IG), epitaxial (EPI), and silicon on insulator (SOI) wafers. From this analysis, it can be understood quantitatively that defect regions in IG wafers increase the diffusion current, although heavily doped regions in epitaxial wafers decrease the diffusion current, and in SOI wafers the diffusion current can be considerably reduced when there is a low recombination velocity at the Si/SiO2 interface.

Effect of oxidation ambient on the dielectric breakdown characteristics of thermal oxide films of silicon

This study investigated the dielectric breakdown characteristics of thermal oxide films grown by dry and wet oxidation. Oxide films grown by wet oxidation have lower B‐mode failure rates and higher B‐mode breakdown fields. On the other hand, the reliability of C mode of oxide films does not differ consistently between films grown by dry and wet oxidation. These results indicate that as‐grown defect causing B‐mode failure may shrink or be reduced during wet oxidation.

The Effect of Hydrogen Annealing on Oxygen Precipitation Behavior and Gate Oxide Integrity in Czochralski Si Wafers

We investigated the effect of hydrogen annealing in the temperature range from 850 to 1200°C on oxygen precipitation and gate oxide integrity in Czochralski Si wafers. The bulk microdefect density of dynamic random access memory thermal simulation wafers showed a strong dependence on the ramp-up rate conditions of hydrogen annealing. The gate oxide integrity improved after hydrogen annealing at temperatures above 1000°C. However, for better stability of the gate oxide integrity after the heat-treatment, higher temperature annealing is necessary. We observed that the effect of hydrogen annealing was limited to the near surface, because the gate oxide integrity of hydrogen-annealed wafers degraded to that for nonannealed wafers after repolishing.

Effect of Solidification Induced Defects in CZ- Silicon Upon Thin Gate Oxide Integrity

In this study, dielectric breakdown strength of silicon dioxide film of 5 to 25nm in thickness is revealed to be determined only by the amount of tiny solidification induced defects in magnetic field applied and conventional CZ silicon single crystals. Nucleus of oxygen induced stacking fault, heavy metal impurities on the surface and surface microroughness are less sensitive factors for it. The deteriorated integrity of the thin films is recovered only by the high temperature annealing at 1250°C under oxygen ambient.