Radial distribution of thermally-induced defects in heavily boron-doped silicon wafers

This research dealt with the effects of point defects and boron concentration on thermally-induced defects in heavily boron-doped silicon substrate and epitaxial wafers. Our research confirmed that the OSF-ring diameter declined with decreasing resistivity. One of the important characteristics of thermally induced defects in heavily boron-doped wafers is that the distribution of defects is uniform, even in wafers with an OSF ring, in contrast to lightly doped wafers, which have a higher concentration of defects in certain areas. Since no dislocation is observed even outside the OSF ring in these heavily-doped wafers, we have hypothesized that either the low concentration or low mobility of excess interstitial silicon atoms in these wafers may play an important role in the uniform distribution of thermally-induced defects. Although some believe that the ring shrinkage alone accounts for the drop in thermally-induced defects concentration, it appears that other factors may be involved. We believe that boron has the largest influence in the phenomenon at resistivities less than 10m Omega cm, but that both boron and point defects are major factors at resisitivities of 17m Omega cm to 50m Omega cm.