Electron spin resonance (ESR) studies have shown that NL10 thermal donors are formed in oxygen-rich silicon (Si) crystals after annealing. In initial NL10 formation stage, it has C2v symmetry with the principle g values g[100]=1.99982, g[01̄1]=1.99799, g[011]=1.99946. After annealing, however, we could detect ESR signals with g values close to those of NL10 in nitrogen-doped oxygen-rich Si crystals. The ESR signals corresponded to nitrogen-oxygen complex donors [D(N,O)s]. We studied the similarities between D(N,O)s and NL10 centers with C2v symmetry. We propose a model for NL10 thermal donors that NL10 with C2v symmetry is D(N,O). Our model clearly explains NL10 thermal donors characteristics.

Evidence for the effect of carbon on oxygen precipitation in Czochralski silicon crystal

Evidence for the effect of carbon on oxygen precipitation in Czochralski silicon crystal

Using hydrogen-enhanced thermal donor formation and hydrogen-enhanced oxygen precipitate nuclei formation, we confirmed the presence of hydrogen in as-grown Czochralski (CZ) silicon (Si) ingots. Hydrogen concentrations in as-grown ingots were very low at 2.5×1011 cm-3. We found that even such a small amount of hydrogen influences the quality of as-grown CZ Si crystals due to hydrogen-enhanced oxygen precipitate nuclei formation caused by in situ annealing during crystal growth. Reducing hydrogen contamination during crystal growth is important in obtaining high-quality CZ Si crystals.

Graphite hot components were improved in a Czochralski-type puller and carbon concentrations were reduced in silicon crystals to 3 • 1014 cm -3 at a solidified fraction of 5% and to 6 • 1014 cm -a at 80%. The improvements include a means to exhaust carbon monoxide gas generated from the graphite heat shield, silicon carbide coatings on the graphite heater, crucible, suscepter, and purge tube. It was found that the graphite heat shield is an important source of carbon, and that carbon monoxide evolution from the melt surface is an important purification mechanism in the Czochralski silicon growth process in addition to the segregation phenomenon of carbon.