Influence of mechanical stress on adhesion properties of DC magnetron sputtered Ti/NiV/Ag layers on n+Si substrate

Due to insufficient adhesion of sputtered Ti/NiV/Ag metallization scheme on n+Si substrate when annealed below 550 °C, investigation was focused on the influence of process parameters on adhesion properties. Adhesion between metallic stack and Si substrate was found to be a strong function of annealing temperature. Additional investigations showed that the cause for poor adhesion was also rather high residual stress in metal thin layers, particularly stress in sputtered NiV layer. High residual stress was measured for NiV (1883 ± 252 MPa) and lower for Ti (334 ± 60 MPa) and Ag (310 ± 10 MPa) layer, respectively. The influence of sputtering parameters on the stress behavior was experimentally verified. By reducing the cathode DC power and Ar working pressure during NiV sputtering we were able to reduce the stress within the structure. A clear correlation was found between the residual stress magnitude and adhesion properties within the temperature range from room temperature to 550 °C. By residual stress reduction within a metallic stack, the necessary annealing temperature to obtain optimal adhesion was reduced from 550 to 500 °C.