Residual stress in thin film

Abstract

The objective of this report is to observe the trend of residual stress with respect to (i) Substrate Bias applied during pre-deposition substrate treatment and (ii) film thickness of (Ti,Al)(N,C) coating material on High-Speed Steel (HSS) substrate. The parameters varied from (i) 0-300W and (ii) 0.856-2.76 µm. Trend in residual stress was observed to decrease when the substrate is subjected to bias up to 200W after which the stress increases with increasing bias up to 300W. The initial drop in residual stress is speculated to be due to the decrease amount of impurities at the interface of the film and the substrate whereas the subsequent increase in the stress might be due to surface stress effect and/or more voids present in the film as a result of higher surface roughness of the substrate. Residual stress was observed to increase with increasing thickness of up to 2.68 µm after which a decrease was observed with increasing thickness of up to 2.78 µm. The trend observed is speculated to be due to surface stress effect and crystallite coalescence. Future research is recommended to investigate on the relationship of grain growth with respect to the varying parameters and its effects on residual stress to further support the discussion of this report.