Diffusion of Point Defects in Silicon Crystals during Melt-Growth. I -Uphill Diffusion-

Abstract

We present experimental results which show that the critical growth rate at which the OSF (oxidation induced stacking fault)-ring of CZ (Czochralski)-silicon single crystal contracts and disappears into the center of the crystal does not depend on the crystal diameter. To explain this phenomenon, the uphill diffusion of point defects toward the crystal growth interface was introduced in addition to normal diffusion. The diffusion behavior of point defects at the growth end of the crystal is found to be sensitively dependent upon the growth rate of the crystal. When the growth rate is low, the effect of uphill diffusion is greater than that of normal diffusion. Then, the out diffusion of point defects is not dependent upon the crystal radius. When the growth rate is high, point defects must diffuse out of the crystal through the crystal surface via normal diffusion.