Electrical conduction and dielectric breakdown in aluminum oxide insulators on silicon

Abstract

Leakage currents and dielectric breakdown were studied in MIS capacitors of metal-aluminum oxide-silicon. The aluminum oxide was produced by thermally oxidizing AlN at 800-1160/spl deg/C under dry O/sub 2/ conditions. The AlN films were deposited by RF magnetron sputtering on p-type Si (100) substrates. Thermal oxidation produced Al/sub 2/O/sub 3/ with a thickness and structure that depended on the process time and temperature. The MIS capacitors exhibited the charge regimes of accumulation, depletion, and inversion on the Si semiconductor surface. The best electrical properties were obtained when all of the AlN was fully oxidized to Al/sub 2/O/sub 3/ with no residual AlN. The MIS flatband voltage was near 0 V, the net oxide trapped charge density, Q/sub 0x/, was less than 10/sup 11/ cm/sup -2/, and the interface trap density, D/sub it/, was less than 10/sup 11/ cm/sup -2/ eV/sup -1/, At an oxide electric field of 0.3 MV/cm, the leakage current density was less than 10/sup -7/ A cm/sup -2/, with a resistivity greater than 10/sup 12/ /spl Omega/-cm. The critical field for dielectric breakdown ranged from 4 to 5 MV/cm. The temperature dependence of the current versus electric field indicated that the conduction mechanism was Frenkel-Poole emission, which has the property that higher temperatures reduce the current. This may be important for the reliability of circuits operating under extreme conditions. The dielectric constant ranged from 3 to 9. The excellent electronic quality of aluminum oxide may be attractive for field effect transistor applications.