Scratch behavior and FEM modelling of Cu/Si(100) thin films deposited by modulated pulsed power magnetron sputtering

A series of copper thin films on Si(100) substrate were deposited using the modulated pulsed power magnetron sputtering under a sputtering pressure from 0.11 to 0.70 Pa. The scratch behavior of Cu/Si(100) thin films was characterized by the critical loads (Lc1-4) with the aid of finite element method (FEM) simulation. Increasing the sputtering pressure, surface morphology became rougher and the cross-sectional pattern transformed from compact fine granular to coarse and crack visible columnar structure. The Cu thin films scratched were continuous and comparative intact at 0.11 Pa which occurred to be with the highest critical loads, then gradually went to vast delamination initiated at 0.30 Pa with the Lc decreasing accordingly. The maximum principal stress (sigma(1)) calculated by FEM was employed to evaluate the transition of critical loads Lc1-Lc4 using the typical stress concentration zones A, B and C which were the zones under, around and at the sides of the scratch tip, respectively. For the Cu/Si(100) thin films with strong adhesion, the Lcl and Lc2 were evaluated through the migration of sigma(1) peak from the zone B to C, while the Lc3 and Lc4 were associated with stress accumulation at the zone C and A. The scratch behavior of Cu/Si(100) thin films was quantitatively expressed with the aid of FEM simulation.