Atomic layer deposition of Y2O3 films using a novel liquid homoleptic yttrium precursor tris(sec-butylcyclopentadienyl)yttrium [Y(sBuCp)3] and water.

Abstract

Atomic layer deposition (ALD) of Y2O3 thin films was studied using a novel homoleptic yttrium ALD precursor: tris(sec-butylcyclopentadienyl)yttrium [Y(sBuCp)3]. Y(sBuCp)3 is a liquid at room temperature. The thermogravimetry curve for Y(sBuCp)3 is clean, with no indication of decomposition or residue formation. Thermogravimetry-differential thermal analysis measurements showed that Y(sBuCp)3 is stable for 18 weeks at 190 °C. Y(sBuCp)3 has a homoleptic structure. Thus, a reduction in manufacturing costs is expected compared to those associated with heteroleptic precursors because additional chemical synthesis steps are usually necessary to produce heteroleptic compounds. In addition, ALD of Y2O3 was demonstrated using Y(sBuCp)3 and water as a co-reactant. The deposition temperature was varied from 200 to 350 °C. The growth rate was 1.7 Å per cycle. In addition, neither carbon nor nitrogen contamination was detected in the Y2O3 films by X-ray photoelectron spectroscopy. Furthermore, smooth films were confirmed by X-ray secondary-electron microscopy. The root-mean-square roughness was measured to be 0.660 nm by atomic force microscopy. Metal-insulator-semiconductor (MIS) Pt/Y2O3/p-Si devices were fabricated to evaluate the electrical properties of the Y2O3 films. An electric breakdown field of -6.5 MV cm-1 and a leakage current density of ∼3.2 × 10-3 A cm-2 at 1 MV cm-1 were determined. The permittivity of Y2O3 was estimated to be 11.5 at 100 kHz. Therefore, compared with conventional solid precursors, Y(sBuCp)3 is suitable for use in ALD manufacturing processes.