Improvement of Thermal Cycling Resistance of Al_xSi_1-xN Coatings on Cu Substrates by Optimizing Al/Si Ratio

The effect of the elemental composition of Al_xSi_1-xN coatings deposited on Cu substrates by magnetron sputtering on their structure, mechanical properties and thermal cycling performance is studied. The coatings with Al-Si-N solid solution, two-phase (Al_xSi_1-xN nanocrystallites embedded in the Si_xN_y tissue phase) and amorphous structure were obtained by varying Al/Si ratio. It is shown that polycrystalline coatings with a low Si content (Al_0.88Si_0.12N) are characterized by the highest thermal cycling resistance. While the coatings with a high and intermediate Si content (Al_0.11Si_0.89N and Al_0.74Si_0.26N) were subjected to cracking and spallation after the first cycle of annealing at a temperature of 1000 °C, delamination of the Al_0.88Si_0.12N coating was observed after 25 annealing cycles. The Al_0.88Si_0.12N coating also exhibited the best barrier performance against copper diffusion from the substrate. The effect of thermal stresses on the diffusion barrier performance of the coatings against copper diffusion is discussed.