Delamination in BEOL: Analysis of interface failure by combined experimental & modeling approaches

It is demonstrated that the widely used equation to derive the adhesive strength from the external load in a 4 point bending test has a certain error by taking only the substrate´s elastic parameters into account. Next to this, failure location analysis gives insight on the measured variation of adhesive strength for the same interface. Subsequently, with numerical simulations, the adhesive strength can be separated in its different energy modes, allowing a better understanding and characterization of the experimental observations (e.g. higher cohesive energy for increasing low-k stiffness). Finally, the competing failure mechanisms within the BEOL are identified as necessary qualifiers for BEOL failure assessment, where currently adhesion strength is mainly used for ranking the performance of different BEOL interfaces.