Effect of nitrogen flow ratio on the microstructure evolution and nanoindented mechanical property of the Ta–Si–N thin films

Abstract

The relations among the process, microstructure, and nanomechanical properties of cosputtered Ta–Si–N thin films have been investigated. The microstructure evolution and varied hardness and elastic modulus property of Ta–Si–N were influenced by nitrogen flow ratios [FN₂% = FN₂/(Far + FN₂) × 100%] during cosputtering together with phase formation and the composition of films. The microstructure of Ta–Si–N formed at a low 2–10 FN₂% was an amorphous-like phase with nanocrystalline grains embedded in an amorphous matrix, while polycrystalline Ta–Si–N was obtained at a high 20–30 FN₂%. The cubic TaN phase or (Ta_1–x,Si_x)N solid solution is much easier to form polycrystallites than noncubic Ta₅Si₃, Ta₂Si, and Ta₂N phases from grazing incidence x-ray diffractometry results. Amorphous-like Ta–Si–N films had much higher nanohardness, stiffness, elastic recovery percentage, and a closer boundary compared to polycrystalline films. A maximum nanohardness of 15.2 GPa was obtained at 3 FN₂%. An increased hardness of polycrystalline films at 20–30 FN₂% is attributed to the higher amount of the hard TaN phase.