FORMATION BEHAVIOR OF INFRARED LIGHT-SCATTERING DEFECTS IN SILICON DURING CZOCHRALSKI CRYSTAL-GROWTH

The formation behavior of grown-in defects which are considered to be oxygen precipitates formed during CZ-Si crystal growth, was investigat ed by means of infrared light scattering tomography. The following res ults were obtained. (i) The density of the IR light scattering defects decreases with a reduction in the crystal pulling rate. (ii) The defe cts are not formed just after solidification, but they grow to a size detectable by LST during cooling to about 1100 degrees C. (iii) The de fect density decreases by slow cooling in the temperature range from t o 1500 to 1000 degrees C, while their size increases. The formation me chanism of the defects was qualitatively discussed from the point of v iew of the interaction between oxygen atoms and point defects by a con sideration of the free energy change and the critical radii of nuclei for oxygen precipitation. It was suggested that the formation of the d efects depends on the vacancy concentration. In the case of a constant vacancy concentration, their density and size are determined by the c ooling rate in the temperature range from 1150 to 1000 degrees C.