Si multicrystals grown by the Czochralski method with multi-seeds

Si multicrystals with several large grains have been grown by the Czochralski (CZ) method with multiple seeds using semiconductor-grade high-purity Si raw material in order to investigate the influence of defects such as dislocations and sub-grain-boundaries on the minority carrier lifetime. Two or three single-crystal Si seeds with [1 0 0], [1 1 0] and [1 1 0] orientations were used for the growth. It was found that the minority carrier lifetime in the Si multicrystals decreased considerably in the region of grains near the semicoherent interfaces with others, e.g., interfaces between [2 3 2] and [1 1 1] grains, [1 0 0] and [1 1 1] grains, and [1 1 0] and [1 1 1] grains. Numerous dislocations with densities as high as 10⁶/cm² in these grains moved to align and generate sub-grain boundaries by the shear stress caused by the semicoherence near the interfaces, which was determined to be responsible for the decrease in the minority carrier lifetime.