CHARACTERISTICS AND EVALUATION METHODS OF CARRIER RECOMBINATION LIFETIMES IN HIGH-QUALITY SILICON WAFERS

摘要

Lifetime quality and the evaluation methods are discussed for (ⅰ) high-quality bulk Czochralski-grown crystals, (ⅱ) polished wafers, and (ⅲ) epitaxial layers in p/p~+ wafers, (ⅰ) To determine the bulk lifetime value accurately for high-quality Si, it is important to measure a bulk sample 1 - 2cm-thick by a photoconductive decay method based on JIS: H0604-1995 or ASTM: F28-75. This high-sensitivity measurement reveals a new phenomenon of oxygen-related recombination-enhanced lifetime shift, (ⅱ) For wafer analyses using an iodine-ethanol chemical passivation technique, the surface recombination velocities are determined precisely, (ⅲ) To evaluate epi-layer lifetime qualities of p/p~+ wafers, "Short-Wavelength Laser-Excited Photoluminescence (PL) Technique" is useful. Applying this technique to a heavy-metal gettering study, it is found that, even in p/p~+ wafers with excellent Fe gettering capability, optimization of the substrate oxygen precipitation and the stability of the gettering sites are important.