OXIDATION BEHAVIOR OF (TI1-XALX)N FILMS PREPARED BY R.F. REACTIVE SPUTTERING

(Ti, Al)N films have drawn much attention as alternatives for TiN coat ings, which are oxidized easily in air above 500 degrees C. We have in vestigated the effect of Al content on the oxidation resistance of (Ti 1-xAlx)N films prepared by r.f. reactive sputtering. (Ti1-xAlx)N films (0 less than or equal to x less than or equal to 0.55) were deposited onto fused quartz substrates by r.f. reactive sputtering. Composite t argets with five kinds of Al-to-Ti area ratio were used. The sputterin g gas was Ar (purity, 5 N) and N-2 (5 N). The flow rate of Ar and N-2 gas was kept constant at 0.8 and 1.2 sccm, respectively, resulting in a sputtering pressure of 0.4 Pa. The r.f. power was 300 W for all expe riments. Substrates were not intentionally heated during deposition. T he deposited films (thickness, 300 nm) were annealed in air at 600 sim ilar to 900 degrees C and then subjected to X-ray diffractometer and A uger depth profiling. The as-deposited (Ti1-xAlx)N films had the same crystal structure as TiN (NaCl type). Al atoms seemed to substitute fo r Ti in lattice sites. The preferential orientation of the films chang ed with the Al content of the film, x. Oxide layers of the films grew during annealing and became thicker as the annealing temperature incre ased. The thickness of the oxide layer grown on the film surface decre ased with increasing Al content in the film. For high Al content films an Al-rich oxide layer was grown on the surface, which seemed to prev ent further oxidation. All of the films, however, were oxidized by 900 degrees C annealing, even if the Al content was increased up to 0.55. (C) 1997 Elsevier Science S.A.