The Assessment of Interface Adhesion of Cu/Ta/Black Diamond™/Si Films Stack Structure by Nanoindentation and Nanoscratch Tests

The interface adhesion of the Cu/Ta/Black Diamond™ (SiOC:H, BD, low-k)/Si substrate films stack structure was investigated. During the nanoindentation tests, a series of indentations under varied maximum normal loads of 1–120 mN were carried out. Regular triangular marks were formed on the surface, and the material pileup around the marks was clearly observed. The delamination occurred first at the Cu/Ta interface with the critical normal load of about 3.14 mN. As the normal load increased to about 63.71 mN, the BD layer began to delaminate from the Si substrate, resulted from the propagation of the cracking within BD layer along the BD/Si interface. The failure behaviors of the stack structure during the nanoscratch tests were similar to that during the nanoindentation tests. At the scratch velocity of 500 μm/min, the critical normal loads for Cu/Ta and BD/Si interfaces delamination were around 15.55 and 27.44 mN, respectively. Furthermore, the critical normal loads were decreased with the increase of the scratch velocity. Due to the similarity between the nanoscratch test and the chemical mechanical polishing (CMP) process, these results implied that lower polishing speed was preferred to avoid the interface delamination during the CMP of Cu/low-k interconnect structure.