Nanoindentation based methodology to characterize the adhesion strength of dielectric bond interfaces

Abstract

This paper evaluates a nanoindentation-based method for measuring dielectric bond interface strength. We demonstrate its simplicity and its ability to perform extensive statistical analysis of Young's modulus and bond strength across bonded wafers or coupons. The method involves sequentially grinding and chemically etching one silicon wafer to expose the dielectric surface, followed by nanoindentation at various locations across the wafer. Force-displacement curves and delamination areas are further assessed by three analysis methods (critical spallation force, indentation force versus delamination area, energy-based approach), each of them having different strengths and limitations. Cohesive zone finite element models (CZMs) were developed to elucidate the failure mechanisms at play and assess the effects of plasticity on the bond strength. Finally, the critical energy release rate was successfully calculated from the indentation-based adhesion energy and other parameters including film thickness, Young's modulus, Yield stress and indenter probe geometry.