Hiroshi Koya

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 SC1 Process on Silicon Surface Microroughness and Oxide Breakdown Characteristics

Surface microroughness and its effects on dielectric breakdown characteristics have been investigated for silicon wafers treated in SC1-based solutions. Surface microroughness was quantified using atomic force microscopy (AFM) and phase shift interferometry (PSI). In contrast to previous reports that SC1 treatment caused undulation of the surface, our observation showed a nominal amount of deterioration. Even prolonged dipping in a solution with high etching rate did not roughen the surface, and the dielectric breakdown characteristics were not affected.

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.