Effects of deposition rate control process on the adhesion of evaporated aluminum films

Abstract

Effects of the deposition rate control process were investigated by measuring adhesion strengths of Al films using the scratch test method. The Al films tested were deposited on glass substrates. The results indicate that the adhesion strength depends strongly on the deposition rate and increased by a factor of three when the deposition rate was increased from 1 nm/s to 10 nm/s. When the deposition rate was accelerated at a constant acceleration rate of 0.01 to 0.05 nm/s2, the adhesion strength was constant regardless of the acceleration rate and the final deposition rate used. Effects of the two-stage evaporation process also were investigated. In the two-stage evaporation process, the initial deposition rate was set at a constant value of 1 nm/s. Subsequent deposition rates used were 3 nm/s, 6 nm/s, and 9 nm/s. The thickness ratio of the initially evaporated films to subsequently evaporated films was varied. The results indicate that the adhesion strength decreased with increasing thickness of the initial film. However, when the thickness of the initial film reached 50 run, the adhesion strength was no longer affected by the subsequent films. Microstructural analyses of the evaporation film indicate that the films with higher adhesion strength had larger particle size.