Fundamental study on laser interference induced polyimide film stripping process

Laser lift off (LLO) is one of the key technologies in the manufacturing of flexible electronics, which has the advantages of non-contact, high efficiency, and compatibility with organic and inorganic materials. At present, LLO technology mostly uses wide line beams (line scanning method) and rectangular laser spots (step repetition method) to scan and exfoliate specific areas, which often faces challenges such as insufficient processing accuracy, high thermal damage, and difficulty in adjusting process parameters. In this work, by using dual beam interference technology, a micrometer grating is formed of the 355 nm ns laser spot light field, which induces the formation of rough micro/nanostructures at the interface between quartz glass and polyimide (PI) film and reduces the adhesion force of PI film to rigid quartz glass substrate, thereby achieving efficient and controllable peeling. The experiments are carried out to thoroughly investigate the effects of process parameters such as laser energy density, incident angle, and pulse number on the peeling effect, and the morphological characteristics of the peeled film are observed and analyzed. The experimental results for a PI film with a thickness of 10 μm showed that the periodic structure at the interface of the peeled PI film is optimum under the conditions of an incident angle of 5°, 15 pulses and a laser energy of 65 mJ/cm 2 . On the basis of the experiments, the mechanism of laser interference induced lift-off (LIILO) technology was discussed in depth, and a model of delamination of PI film was developed. Furthermore, the changes in interfacial adhesion force are analyzed under different process parameters, and evolution process of interfacial morphology of periodic structures was summarized.