Harnessing pre-stretching for modulating fracture competition in multistep ultrathin chip peeling

Abstract

In the backend process of chip manufacturing, due to the highly dense arrangement of chips after wafer dicing, stretching pretreatment for spacing expansion is essential prior to chip-peeling stage. This study quantitatively integrated substrate pre-stretching step with chip-peeling techniques (needle ejection and vacuum suction), performing a mechanical analysis to develop parameterised optimisation for a multistep process. A non-equal-length laminated Timoshenko beam was modelled for the chip–adhesive–substrate (CAS) structure, particularly considering the transmission relationship of pre-stretching and its impact on structural deformation thorough the multistep process. Closed-form solutions for the delamination modelling were derived analytically and validated through finite element analysis. A dimensionless index was proposed to compare chip-peeling safety under different procedure combinations, and comprehensively evaluate the fracture competition. Appropriate pre-stretching was found to mitigate chip failure by neutralising stress fields and alter adhesive fracture by modulating the energy aggregation modes during delamination, and the optimal value of pre-stretching was established. The crack propagation sensitivity to load response hysteresis was assessed, illustrating that the optimised process required careful management of technical efficiency to ensure production safety. The multistep chip-peeling optimisation was validated experimentally, providing effective suggestions for manufacturing technology.