THE EFFECT OF OXYGEN ON SECONDARY DEFECT FORMATION IN MEV SELF-IMPLANTED SILICON

The effects of ion fluence and oxygen concentration on secondary defec t formation in MeV self-implanted silicon has been studied for Czochra lski (Ct) and float zone (FZ) wafers by means of transmission electron microscopy (TEM) and optical microscopy with bevel polishing/chemical etching. We found that the density, distribution and number of extend ed defects is strongly dependent upon the oxygen concentration. The di slocation density was found to be up to one order of magnitude lower i n FZ wafers. At high ion fluences (similar to 10(15) cm(-2)), secondar y defects form in a well-defined band near the ion projected range, R- p. At lower ion fluences, dislocations extend from the defect band to increasingly large depths, For ion fluences approaching the threshold for secondary defect formation (similar to 10(14) cm(-2)), defects are observed from the surface to depths of similar or equal to 10 mu m, i .e., five times R-p.