The impact of annealing temperature and time on the electrical performance of Ti/Pt thin films

Abstract In this study, we focus on the influence of annealing time t PDA (i.e. 30 min and 630 min) on the room-temperature resistivity of electron-beam-evaporated titanium/platinum thin films when exposed to thermal loads up to temperatures T PDA of 700 °C. The titanium has a fixed thickness of 5 nm and serves as an adhesion layer. The thickness d f ,Pt of the platinum top layer is varied between 21 and 97 nm. Up to annealing temperatures of 450 °C, the film resistivity of the bi-layer system is linearly correlated with the reciprocal platinum film thickness independent of t PDA , as expected from the size effect. At t PDA  = 30 min, the change in intrinsic film stress dominates the electrical behavior in this annealing regime, predominantly at large d f ,Pt values. Compared to t PDA  = 630 min, however, the increase in resistivity especially at low platinum film thickness is substantially larger demonstrating that titanium starts to diffuse at these long annealing times even at moderate temperatures. At T PDA  = 600 °C, the diffusion of titanium into the top layer leads to an enhanced increase in film resistivity ρ f , especially at low platinum thicknesses and low annealing times, as the mean penetration depth of diffused titanium is under these conditions in order of d f ,Pt . Above T PDA  = 600 °C, ρ f is slightly increased at t PDA  = 30 min. At t PDA  = 630 min, however, the film resistivity is decreased at d f ,Pt d f ,Pt resulting predominantly in Ti x O y formation on the top film surface and hence, having low impact on ρ f .