Titanium-aluminum nitride film growth and related chemistry using dimethylamino-based precursors

Abstract

Direct liquid injection chemical vapor deposition of (Al,Ti)N films using NH3 and a solution of tetrakis(dimethylamino)titanium and the tris(dimethylamino)alane dimer in toluene is reported. The decomposition reactions of the dimethylamino-based precursors with and without the presence of NH3 are studied to explain the incorporation of Al, Ti, N and C into the (Al,Ti)N films. Addition of NH3 during pyrolysis decreases the decomposition temperature of both precursors by more than 90 K. (Al,Ti)N films containing Al, Ti, N, C and O were deposited on a SiO2 substrate between 425 and 625 K. Introducing 0.002 torr of NH3 increased the film growth rate nearly 20 times and reduced the carbon content in half at 550 K; carbon was reduced as low as 5 at.% at 425 K. The addition of 0.002 torr NH3 also reduced the Al/Ti ratio by more than 62% and resulted in nearly 45% more N incorporation at all film growth temperatures. A 10-fold increase in the aluminum precursor partial pressure resulted in a 60% increase in film aluminum concentration. The films were not resistant to oxidation; exposure to ambient resulted in 330% more oxygen in the film and the removal more than 40% of the carbon and nitrogen from the (Al,Ti)N film. Conformal (step coverage near unity) (Al,Ti)N films were produced in 0.18 μm SiO2 trenches with an aspect ratio of five at 425 K in the presence of NH3 and at 550 K without NH3.