Influence of Si content and sputtering condition on the microstructure and mechanical properties of r.f.-sputtered transition metal nitride films

摘要

The influence of Si content and sputtering conditions on the microstructure and mechanical properties (hardness and Young's modulus) of transition metal nitride films containing Si such as Zr-Si-N and Ti-Si-N were investigated using XRD, TEM and nanoindentor. While the substrate temperature was kept from ～343 K to ～673 K during deposition, some films were applied with d.c.-bias voltage. Without substrate heating and bias application, the hardness of the films increased by 5-10 GPa over the binary systems such as ZrN or TiN. The hardness reached a maximum of 33-37GPa with a small amount (3-5 at%) of Si; it then decreased to lower than those of binary systems when Si was more than 10 at%. The tendency to grow columnar grains was strongest at about 3-5 at% of Si, but it became equiaxial when Si was more than 5 at%. Nano-crystalline and/or amorphous like structures were formed when Si was higher than 10 at%. Films containing more than 10% of Si, which showed the lower hardness less than 20GPa, consist mainly of nano-crystal grains. The presence of ZrN nano-crystals embedded in Si_3N_4 was not observed in the present study. The increase of hardness with small additional amounts of Si in metal nitride films is probably attributed to the atomic strain caused by Si atoms at non-equilibrium sites. These results also indicated that the grain size might make minor contributions to the hardening.