Integrated plasma-promoted chemical vapor deposition route to aluminum interconnect and plug technologies for emerging computer chip metallization

Abstract

A low temperature plasma-promoted chemical vapor deposition (CVD) process was developed for the formation of reliable aluminum interconnect and plug metallization schemes for applications in and beyond 0.25 μm integrated chip device technology. The process employs aluminum source precursors that are based on amine adducts of alane, such as dimethylethylamine alane, where the lack of a direct aluminum–carbon bond provides a clean chemical pathway by which to eliminate the precursor’s hydrocarbon groups at relatively low temperatures and yield pure aluminum films. The formation of dense and thick aluminum films at low temperature and that have a smooth surface morphology is achieved by combining a radio-frequency hydrogen plasma at low power densities (below 0.1 W/cm2) with a low frequency (<400 kHz) substrate bias. The use of a low power density plasma is designed to activate a uniform nucleation of aluminum grains, thus eliminating the inherent problem of surface roughness that plagues thermal CVD processing, while avoiding undesirable precursor gas phase decomposition and film contamination. Additionally, the application of a substrate bias enhances the impingement rate of precursor species on the substrate, and lead to an increase in the re-emission probability of such species inside via and trench structures, leading to conformal step coverage and complete fill. The aluminum interconnect and plug structures produced were specular to thicknesses above 1 μm, exhibited contamination levels below the 1 at. % detection limit of x-ray photoelectron spectroscopy and Auger electron spectroscopy, and displayed postanneal resistivity of 3.38 μΩ cm. Conformal fill of 0.25 μm structures was achieved at growth rates in excess of 1000 Å/min.