EQUILIBRIUM-CONSTANT OF SEGREGATION-INDUCED FE GETTERED BY HEAVY BORON DOPING IN SI

The equilibrium constant of segregation-induced Fe gettering by heavy boron (B) doping in Si is obtained by experimental determination of th e activation energy and the site density parameter of the gettering re action. The activation energy is determined to be 0.68+/-0.03 eV by an alyzing the temperature dependence of the equilibrium constant of the reaction. This result indicates that the Fe gettering is strongly rela ted to formation of the Fe-B complex whose binding energy is very clos e to the value determined for the activation energy. Furthermore, the gettering site density is found to be proportional to the doped B conc entration in the substrate crystal. It is understood from the activati on energy value that the Fe gettering ability of each reaction site fo r heavy B doping is less than that for thin polycrystalline Si film on the back surface of a substrate. The well known high overall getterin g capability of the heavily B-doped substrate is not simply due to the activation energy effect it is predominantly due to a large number of gettering sites in the overall region of the substrates and the close ness of the impurity Fe to the gettering sites. (C) 1998 American Inst itute of Physics.