Theoretical Modeling and Experimental Studies of Ultra-Thin Chip Transfer in Laser-Induced Forward Transfer

In order to understand and optimize the complex transfer process of ultrathin chip in laser-induced forward transfer (LIFT), a substrate-dynamic release layer (DRL)-chip structure is proposed, and a finite-element and cohesive zone model (CZM) is developed to investigate the laser ejecting needle formation and ultrathin chip peeling evolution, which is used to help analyze the impact transfer behavior of ultrathin chip in LIFT. The model considers laser absorption, conduction, volumetric expansion, and crack propagation in the substrate-DRL-chip structure. The results of the model indicate that longer laser irradiation time could produce larger maximum vapor pressure and chip transfer velocity. In addition, there are three transfer conditions in LIFT: no transfer, successful transfer, and impact fracture, which are sensitive to laser fluence. In order to achieve successful ultrathin chip transfer, an LIFT window is established and provides guidance for the appropriate laser fluence in LIFT.