Quantitative investigation of the adhesion failure of Ti-based metal thin films on Si wafers

In this study, failure analysis was conducted to investigate the root cause of Ti/Ni/Ag film peeling from Si wafer surface. The adhesion strength of Ti/Ni/Ag film on Si was quantitatively measured by 4 Point Bending method (4PB), where a novel delamination initiation method was introduced to significantly reduce the energy barrier for the delamination initiation. The possible contamination elements at the Ti/Si interface were analyzed by TOF-SIMS analysis but no considerable difference was found. On the other hand, TEM and AFM analysis revealed that the adhesion failure of Ti/Ni/Ag film from Si substrate was possibly because of the low surface roughness resulted from the excessive polishing during wafer thinning process. The findings of this work would be interesting for the researchers doing failure analysis on metal film peeling/delamination on IC or MEMS devices. The methods of creating defects for initiation of delamination could be widely applied on 4 Point Bending testing of various types of metal films on Si wafers.