Transfer Process of Thermally Annealed Thin Films Using a Metal Sacrificial Layer and Etch Access Holes

Metal sacrificial-layer-assisted transfer is a promising strategy for transferring thermally annealed thin films onto flexible polymer substrates without exposing the receiver substrate to thermal damage. However, stable release of the annealed thin-film stack remains challenging because high-temperature annealing can alter the etching behavior of the sacrificial metal layer and the protective oxide layer. In this study, we propose a thin-film transfer process using a Ni metal sacrificial layer and etch access holes, in which an SU-8/Ti/SiO2 transferable stack was fabricated on a rigid sapphire donor substrate, annealed at 400–700°C, selectively released by Ni etching, and transferred onto a flexible PET receiver substrate. As the annealing temperature increased from 400 to 700°C, the SiO2 etch rate decreased from 6.8–6.96 to 2.61–3.83 nm/s, while the Ni release time increased from 72–77 to 82–95 min; nevertheless, the transferable stack was successfully transferred under all process conditions with image-based transfer yields of 58.81–82.76%, with the highest yield obtained for the 200 nm Ni sacrificial layer annealed at 550°C. These results demonstrate the process feasibility of the proposed metal sacrificial-layer and etch-access-hole-based transfer approach for transferring thermally annealed thin-film structures from rigid donor substrates to flexible receiver substrates.