Electrical behaviour of electron-beam-evaporated yttrium oxide thin films on silicon

Abstract

The electrical properties of electron-beam-deposited Y 2O 3 film interfaced with Si(100) have been investigated. The thickness-dependent effective dielectric constant of the Y 2O 3 film increases to 18–27 and bulk trapped charge density decreases to (10−4) × 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 Y 2O 3 film by oxygen intake. In as-deposited Y 2O 3 (400 Å) films, the leakage current density is about 7 × 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 Y 2O 3 film. A decrease later to 4 × 10 -9 A cm -2 on high temperature annealing is caused by reduction in defects and growth of amorphous SiO 2 film at the interface. The current transport across the Y 2O 3 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 Y 2O 3 films as high density MOS capacitors and gate dielectric in very-large-scale integration technology.