DEVELOPMENT OF CHARACTERIZATION METHODS FRO SILICON CRYSTALS WITH THE USE OF HYDROGEN INCORPORATION

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The purpose of the present research is to evaluate electrically-active defects and measure the quantity of oxygen in heavily boron-dropped pィイD1+ィエD1 CZ silicon wafers. An efficient method for defect characterization, DLTS, was not carried out for pィイD1+ィエD1 wafers because of difficulties of fabrication of Schottky diodes. It was also difficult to detect oxygen by FT-IR because of large free carrier absorption. So, we tried to make diodes by decreasing carrier concentration due to the hydrogen passivation of boron. At the same time, it was considered possible to detect oxygen by FT-IR due to the decrease of free carrier absorption. The efficient method to introduce hydrogen was the exposure of samples to hydrogen plasma at 300℃. Diodes were successfully fabricated by evaporating Sm on top of hydrogenated surfaces. Then, the carrier concentration decreased from 〜5x10ィイD118ィエD1 cmィイD1-3ィエD1 to 〜10ィイD117ィエD1 cmィイD1-3ィエD1 in the near-surface region. As an alternative method, silicon wafers were boiled in water to introduce hydrogen more conveniently. The near-surface carrier concentration of 〜10ィイD117ィエD1 cmィイD1-3ィエD1 was obtained by consecutive eight processes of boiling and removal of oxide layer. The fabrication of diodes on hydrogenated surfaces of pィイD1+ィエD1 wafers made it possible to estimate defects by DLTS. On the other hand, the hydrogen atoms might deactivate defects in addition to boron acceptors. It is necessary to investigate the interaction between hydrogen atoms and defects. The study showed that hydrogen atoms not only deactivate some defects but also activate some inactive defects. Thus, some results were obtained for electrical characterization, but detection of oxygen in pィイD1+ィエD1 wafers by FT-IR was unattainable. For such purpose, more decrease of the carrier concentration than 〜10ィイD117ィエD1 cmィイD1-3ィエD1 is needed. We must pursue the introduction technique of the larger quantity of hydrogen into pィイD1+ィエD1 wafers.