SELECTIVE-AREA CHEMICAL-VAPOR-DEPOSITION OF ALUMINUM USING DIMETHYLETHYLAMINE ALANE

Dimethylethylamine alane (DMEAA) was used to deposit Al films selectiv ely on a variety of metal surfaces (Au, Ti, NiCr, W) in the presence o f SiO2, Si, and Si3N4. Selectivity ((gs)S(ns)) was quantified as (thet a(gs) - theta(ns))/(theta(gs) + theta(ns)) where theta(gs) and theta(n s) represent the coverage of the growth and non-growth surfaces, respe ctively. At 100-degrees-C, Al films were deposited on 3-mum-wide Au st rips in the presence of SiO2 With excellent selectivity ((Au)S(SiO2) > 0.99). Extended deposition times or increased substrate temperatures led to a reduction in selectivity. At 180-degrees-C selectivity droppe d to zero. Removing the carrier gas (H-2) and decreasing the DMEAA par tial pressure in the system had no significant effect. Encroachment, i n which Al at the edges of the Au regions grew laterally onto adjacent SiO2 strips, was observed and had a significant impact on the selecti vity of a deposition. Even after very short DMEAA exposure times, trac e amounts of Al were detected on silicon oxide surfaces using X-ray ph otoelectron spectroscopy. Pretreatment of the non-growth surface with hexamethyldisilazane, which converted surface OH groups on SiO2 to tri methylsilyl ethers, did not enhance selectivity.