Characterization of Ti/W, Ti/Cr, and Ti/Pt thin flims-Part II: Nano-scratching and tribological properties

The present paper, Part ІІ in a two-part series, describes the scratching behaviors and tribological properties of Ti/W, Ti/Cr, and Ti/Pt thin films annealed at 400, 500, and 600 °C that were evaluated by a nano-scratch measurement technique. The results of the nano-scratch tests indicate that the Ti/W film annealed at 400 °C exhibited high scratch resistance, good adhesion to the substrate, and a low friction coefficient. On the other hand, cracking and delamination phenomena appeared in the Ti/W films annealed at 500 and 600 °C. The Ti/Cr films annealed at 500 and 600 °C were better able to withstand the indenter tip than the Ti/Cr film annealed at 400 °C, but their tribological performance in terms of friction coefficient was worse than that of the Ti/Cr film annealed at 400 °C. The delamination phenomenon did not appear in any of the Ti/Cr films. The Ti/Pt film annealed at 500 °C exhibited the highest elastic recoverability and scratch resistance among the Ti/Pt films. The friction coefficient of the Ti/Pt film annealed at 600 °C was higher than that of the Ti/Pt films annealed at 400 and 500 °C; this was caused by the hillocks formed on the Pt surface as confirmed in Part І. The delamination and cracking phenomena were not observed at all in the Ti/Pt films. Based on the experimental results of Part І and ІІ, the Ti/W film annealed at 400 °C among the thin films investigated in this study is the most appropriate for metallization under physical contact conditions in MEMS devices.