DEPOSITION OF (TI,AL)N THIN-FILMS BY ORGANOMETALLIC CHEMICAL-VAPOR-DEPOSITION - THERMODYNAMIC PREDICTIONS AND EXPERIMENTAL RESULTS

Ti1-xAlxN coatings were deposited by CVD using organometallic precurso rs: tetrakis dimethylamido titanium Ti(N(CH3)(2))(4), hexakis dimethyl amido dialuminum Al-2(N(CH3)(2))(6) and ammonia as reactant gas. A pre liminary thermodynamic study allowed us to establish the ternary diagr am Ti-Al-N at two temperatures (1173 K and 673 K). For the CVD thermod ynamic simulation, the metastable phase Ti1-xAlxN was first considered as the mixture of the stable compounds TiN fcc and AlN hcp. The calcu lations show that in our working range parameters there is codepositio n of TiN and AIN (and consequently, of the metastable phase). Experime nts were conducted at deposition temperature as low as 643 K. (Ti,Al)N thin films were characterized by SEM, TEM and EPMA. The deposition ra te is about 15 nm/min. We obtained an Al/Ti ratio varying from 5:95 to 50:50. The ammonia flow rate has a significant effect on (Ti,Al)N com position and also on carbon and oxygen incorporation. The metastable c ubic substitutional solid solution phase structure Ti1-xAlxN has been identified, with a lattice parameter a = 4.15 +/- 0.03 Angstrom and na nometer-sized grains. (C) 1997 Elsevier Science S.A.