Investigation of Long-Term Stability of Hybrid Systems-in-Foil (HySiF) for Biomedical Applications

Towards a biocompatible HySiF, in this work a customized Chip-Film Patch system is presented, in which an ultra-thin silicon chip is embedded in spin-coated polyimide. In addition, packaged with ceramic encapsulation layers, using atomic layer deposition (ALD) method thus achieving a prolonged long-term performance of the sensors. We have thoroughly investigated ALD coated polyimide foils with varying sequential metal oxide layers. More specifically, Al ₂ O ₃ -TiO ₂ thin-film layers are deposited on polyimide foils in the range from 20 nm -to 80 nm thickness. ALD thin-film is investigated with means of scanning electron microscopy and atomic force microscopy. Intrinsic stress of Al ₂ O ₃ -TiO ₂ thin-films on polyimide foils has been investigated and the water vapor transmission rate (WVTR) of the compound layers have been determined to assess hermeticity of the ALD layers. The long-term electrical leakage performance of the CFP substrates is evaluated, in physiological environment under cyclic mechanical load. The results provide a basis for processing flexible Hybrid Systems-in-foil for long-term utilization.