INFLUENCES OF MAGNESIUM AND ZINC CONTAMINATIONS ON DIELECTRIC-BREAKDOWN STRENGTH OF MOS CAPACITORS

The dielectric breakdown strength of thermally grown silicon dioxide f ilms was studied for MOS capacitors fabricated on silicon wafers that were intentionally contaminated with magnesium and zinc. Most of magne sium was detected in the oxide film after oxidation. Zinc, some of whi ch evaporated from the surface of wafers, was detected only in the oxi de film. The mechanism of the dielectric degradation is dominated by f ormation of metal silicates, such as Mg2SiO4 (Foresterite) and Zn2SiO4 (Wilemite). The formation of metal silicates has no influence on the generation lifetime of minority carriers, however, it provides the fla t-band voltage shift less than 0.3 eV, and forces to increase the dens ity of deep surface states with the zinc contamination.