A Theoretical Study on Post-It-Like Debonding Process for BCB Cap Transfer Packaging Based on FEM Simulation

This paper presents ANSYS finite-element method analysis of wafer-level Benzocyclobutene cap transfer packaging process utilizing simple and easy detachment of the carrier wafer. The detachment has been implemented through hydrophobic monolayer coating of Si carrier wafer surface before BCB cap patterning. Razor blade insertion between the Si carrier and device wafer is used to separate the BCB cap from the carrier wafer. The debonding is regarded as interfacial fracture between Si and BCB, and thus the monolayered interface is modeled with ANSYS cohesive zone model. BCB cap's deformation and resultant stress during the debonding are principal interests of the modeling as it determines whether the transfer succeeds or fails. For this purpose, typical load-displacement curves of crack analysis are studied to comprehend the debonding behavior of the BCB cap in the course of Si carrier detachment. It is found that the BCB cap size is a critical parameter for the debonding process as interfacial toughness is proportional to the BCB cap dimension. And thicker BCB cap is more efficient to the debonding in terms of necessary opening displacement and developed maximum stress. In addition, cap material property such as Young's modulus has significant effect on the debonding behavior.