Influence of sputtering conditions on the structure and properties of Ti-Si-N thin films prepared by r.f.-reactive sputtering

The influence of Si content and sputtering conditions on the microstructure and mechanical properties (hardness and Young's modulus) of Ti-Si-N were investigated using XRD, XPS and nano-indentation. The composite targets consisting of a Ti plate and Si or Si₃N₄ chips were sputtered in a mixture of argon and nitrogen. Ti-Si-N films were prepared in an r.f. sputtering apparatus of the facing target-type. During the deposition, the substrate was heated from room temperature up to ∼573 K and a bias of d.c. up to -100 V was applied. Without substrate heating and bias, the hardness of the films increased from 30 GPa for a binary system, reaching a maximum of 37 GPa for a ternary system with a small amount (3-8 at.%) of Si. It then decreased to lower values than those of binary systems when Si was more than 10 at.%. The tendency to grow columnar grains was strongest at approximately 5 at.% of Si. The hardness of Ti-Si-N films increased and reached to a maximum value of 42 GPa around at a bias of -10 V, but the crystallite size of the film remained larger than 23 nm. The increase of hardness with small amounts of Si in TiSiN films was probably associated with the lattice distortion. On the other hand, the increment of hardness of films containing 20 at.% of Si by the negative bias application could be attributed to the formation of nano-composite structure.