Reduction of grown-in defects by vacancy-assisted oxygen precipitation in high density dynamic random access memory

The silicon ingot growing scheme has been investigated to reduce the grown-in defect. It is found that a fast cooling rate suppresses the further growth of crystal-originated particles (COPs) after supersaturating vacancies by increased pulling speed. This reaction makes the COP-rich region with the high density and smaller size extend to wafer edge. Initially higher COPs decrease by subsequent annealing in oxygen ambient through the vacancy-interstitial annihilation mechanism. Since vacancies assist oxygen precipitation, bulk microdefect is easily formed and the intrinsic gettering during the denudation process becomes more efficient. Based on this principle, the ingot growing scheme with a 1.8 mm/min-pulling speed and 9.8degreesC/min cooling rate in the range of 1000 to similar to1200degreesC is suggested, and its superiority is verified through the improvement of the tail component of retention time by 40% in high density dynamic random access memory. (C) 2003 American Institute of Physics.