Extremely Flexible (1mm Bending Radius) Biocompatible Heterogeneous Fan-Out Wafer-Level Platform with the Lowest Reported Die-Shift (<6 µm) and Reliable Flexible Cu-Based Interconnects

Abstract

A flexible fan-out wafer-level packaging (FOWLP) process for heterogeneous integration of high performance dies in a flexible and biocompatible elastomeric package (FlexTrateTM) was used to assemble >600 dies with co-planarity and tilt <1µm, average die-shift of 3.28 µm with ? < 2.23 µm. We have also engineered a novel corrugated topography of a stress buffer layer for metal interconnects on FlexTrateTM to mitigate the buckling phenomenon of metal films deposited on elastomeric substrates. Corrugated interconnects were then tested for their mechanical bending reliability and have shown less than 0.4% change in resistance after bending at 1 mm radius for 1,000 cycles. Finally, we demonstrate integration of an array of 25 dielets interconnected in a daisy chain configuration at 40 µm interconnect pitch.