Experimental and modeling study of controllable laser lift-off via low-fluence multiscanning of polyimide-substrate interface

• New interface phenomenon induced by multiple low-fluence backside irradiations. • A non-destructive and controllable peeling technique for flexible electronics. • Confirm the transition of the interface bonding state affected by gas products. • Achieve the accurate prediction of the amount of gas products at the interface. • Establish the direct relationship between the interfacial gas and peeling effect. Fabricating large-area thin-film flexible electronics rely on the peeling process from rigid prefabricated carriers. The well-established laser lift-off (LLO) employs a shaped excimer laser to scan the interfacial polyimide (PI) for peeling. However, using the traditional LLO (high-fluence single scanning), nondestructive peeling of ultra-thin fragile devices remains challenging. Here, an enhanced LLO strategy based on multiple low-fluence irradiations with an excimer laser (m-LLO) is studied to perform noninvasive and controllable peeling. We first construct a model predicting the core parameter of the peeling effect, the amount of gas accumulated at the interface generated by multiple backside irradiations. The specific influence of gas on the peeling effect is obtained through the accurate assessment of the interface bonding state by profile analysis, micro-observations, and strain sensing. We establish a deterministic peeling method by providing the peeling index that can precisely evaluate the interface bonding state under different process parameters, showing advantages over traditional LLO. The characterizations of chemical modifications after peeling further confirmed a different process mechanism of m-LLO. These results would be helpful to develop a non-destructive and controllable LLO process for the mass production of the next generation of flexible electronics.