Influence of Deposition Parameters on the Properties of Titanium Nitride Films Formed by Ion Beam Assisted Evaporation

Abstract

An IBAD system comprising a resistance heated linear evaporation source and a r.f. ion source providing a ribbon-shaped N + /N 2 + -ion beam was employed for the deposition of TiN x -films onto Si(100)-substrates. The ion energy E ion and the flux density ratio J ion /J Ti ; of the nitrogen ions and the evaporated Ti could be varied independently. Their influence on the film properties was studied for J ion /J Ti -values from 0.13 to 0.73 at a fixed E ion of 540 eV, and for E ion values from 140 eV to 1040 eV at a fixed J ion /J Ti -ratio of 0.27. The flux density ratio strongly influences the chemical composition of the TiN x -layers with x varying from 0.5 to 1.4. X-ray lattice parameter measurements point to empty nitrogen sites in the cubic 6-TiN lattice for the understoichiometric range, and surplus nitrogen atoms incorporated as interstitials for x>1. The increase of the flux density ratio causes a transition from a columnar structure with tensile stress (zone 1 in the structure zone model) to a compressively stressed dense structure (zone T). Simultaneously, the crystallite orientation of the cubic 6-TiN-phase changes from a (111)-to a (100)-fibre texture. The ion energy variation at a constant flux density ratio causes again a transition from a columnar film structure (zone 1) to a T-zone structure, accompanied by a change from a (110)-ideal layer texture to a (110)-fiber texture. Film density and average grain size increase from zone 1 to zone T. The development of the microstructural film properties are discussed in terms of the energy input by the N + /N 2 + -bombardment, and of the total free energy of the films. The behaviour of the grain size and the film hardness is referred to the predictions form the Hall-Petch relation.