The influence of thermal annealing on microstructure and resistivity of Pt films with different thickness

The thermal stability of platinum film dominates the performance when the film electrodes operate under extreme conditions, such as high temperature. In this study, Pt films with thicknesses of 50, 200, and 400 nm were deposited by magnetron sputtering and annealed in different conditions to investigate the microstructure and resistivity changes. The results show that thicker films exhibit superior dewetting resistance. For Pt films with 50 nm thickness, bumps and pits appear at the surface after vacuum annealing at 773 K, while the bumps grow and the pits transform into voids at 973 K. These defects further expand and separate the films into island-like structures at 1173 K. Voids appear at the surface of Pt-200 after vacuum annealing at 1173 K and atmospheric annealing at 1073 K, which appear at the surface of Pt-400 after vacuum and atmospheric annealing at 1173 K, and island-like structures are observed at 1273 K. Pt films exhibit superior thermal stability in atmospheric environment. All films develop numerous isolated island-like structures at surfaces after vacuum annealing at 1273 K, while only Pt-50 exhibits a surface with a serpentine structure after atmospheric annealing at 1273 K. Below 873 K, the film resistivity decreases with the temperature increasing, primarily driven by recrystallization-mediated elimination of lattice defects such as grain boundaries, dislocations, and vacancies. Above 873 K, the film resistivity increases with the temperature increasing, because dewetting damages the film's structural integrity. These findings provide key design guidelines for Pt-based components operating in harsh working environment to explore the method to improve the high temperature stability of Pt films, and optimize the magnetron sputtering process and guide the application in temperature sensitive devices.