Atomic Layer Deposition of Pd on an Oxidized Metal Substrate

Abstract

A method is presented for the atomic layer deposition (ALD) of palladium on air-exposed tantalum and silicon without the use of a plasma. Palladium can be deposited on these substrates at 80 °C using molecular hydrogen and palladium(II) hexafluoroacetylacetonate (PdII(hfac)2) as the precursor. In the case of palladium deposition on tantalum, the fluorine content is significantly reduced compared to previous results for thermal ALD. Use of a sufficiently long hydrogen pulse eliminates the noble metal substrate requirement typically needed for low deposition temperature ALD, and removes the requirement of plasma for deposition on oxidized metal surfaces. Rutherford backscattering spectrometry (RBS) measurements indicate a correlation between hydrogen pulse time and seed layer deposition rate, which is also substrate dependent. X-ray photoelectron spectroscopy (XPS) measurements indicate high-quality palladium film deposition on tantalum, suggesting the substrate temperature was low enough to prevent dissociation of the hfac ligand and adequate carbon and fluorine scavenging by the atomic hydrogen. The use of thermal ALD as opposed to a plasma process maintains the direction independence and high conformal nature of films produced by ALD, enabling deposition on highly varied topographies and three-dimensional porous structures.