Cross-sectional Nanoindentation: Applicability for testing Polyimide adhesion in semiconductor components

This work investigates the applicability of the cross-sectional nanoindentation (CSN) method for the adhesion of thick ductile materials such as polyimide layers. $\mathrm{ASiO}_{\mathrm{x}}/\mathrm{A1}/\mathrm{Si}_{\mathrm{x}}\mathrm{N}_{\mathrm{y}}$/polyimide stack deposited on a Si substrate was investigated, where the interface between the substrate and the $\mathrm{SiO}_{\mathrm{x}}$ was intentionally weakened to provoke long and stable crack propagation which alleviates the analysis. This cracking was investigated in an SEM and the opened interface confirmed using EDX analysis. The critical energy release rate ($\mathrm{G}_{\mathrm{c}}$) was determined via an analytical method and numerically by using finite element analysis (FEA) to compare the effectiveness of the respective methods. FEA further allowed to determine the influence of plasticity in the Al and polyimide layers and the relaxation of the Si-wedge, that is created during the CSN experiment, due to the polyimide layer. To separate the effect of wedge-relaxation and plasticity a mixed evaluation of using analytical methods with values obtained from FEA simulations was also performed. The experimental results show that the analytical method underestimates energy release rate compared to the FEA method, while a mixed approach overestimates the adhesion.