Selective Area Chemical Vapor Deposition of Aluminum Using Dimethylethylamine Alane

Dimethylethylamine alane (DMEAA) was used to deposit Al films selectively on a variety of metal surfaces (Au, Ti, NiCr, W) in the presence of SiO₂, Si, and Si₃N₄. Selectivity (^gsS_ns) was quantified as (θ_gs-θ_ns)/(θ_gS + θ_ns) where θ_gs and θ_ns represent the coverage of the growth and non-growth surfaces, respectively. At 100 °C, Al films were deposited on 3-μm-wide Au strips in the presence of SiO₂ with excellent selectivity (^AuS_SiO2 > 0.99). Extended deposition times or increased substrate temperatures led to a reduction in selectivity. At 180 °C selectivity dropped to zero. Removing the carrier gas (H₂) and decreasing the DMEAA partial pressure in the system had no significant effect. Encroachment, in which Al at the edges of the Au regions grew laterally onto adjacent SiO₂ strips, was observed and had a significant impact on the selectivity of a deposition. Even after very short DMEAA exposure times, trace amounts of Al were detected on silicon oxide surfaces using X-ray photoelectron spectroscopy. Pretreatment of the non-growth surface with hexamethyldisilazane, which converted surface OH groups on SiO₂ to trimethylsilyl ethers, did not enhance selectivity.