ELECTRICAL BEHAVIOR OF ELECTRON-BEAM-EVAPORATED YTTRIUM-OXIDE THIN-FILMS ON SILICON

The electrical properties of electron-beam-deposited Y2O3 film interfaced with Si(100) have been investigated. The thickness-dependent effective dielectric constant of the Y2O3 film increases to 18-27 and bulk trapped charge density decreases to (10-4) x 10(11) cm-2 after oxygen annealing at approximately 800 K temperatures. These changes are attributed to annealing out of defects and improvement in the stoichiometry of the Y2O3 film by oxygen intake. In as-deposited Y2O3 (400 angstrom) films, the leakage current density is about 7 x 10(-8) A cm-2 at 0.1 MV cm-1. Moderate initial annealing causes it to increase as a result of localized field regions caused by structural changes at macroscopic defects in the polycrystalline Y2O3 film. A decrease later to 4 x 10(-9) A cm-2 on high temperature annealing is caused by reduction in defects and growth of amorphous SiO2 film at the interface. The current transport across the Y2O3 film is by a Poole-Frankel emission process. High dielectric constant, low trap density and well-behaved capacitance-voltage characteristics exhibiting metal-oxide-semiconductor (MOS) action suggest possible applications of Y2O3 films as high density MOS capacitors and gate dielectric in very-large-scale integration technology.