FOWLP-Based Flexible Hybrid Electronics II: Heterogeneous Integration Technology of Micro-LEDs on 3D-IC for Smart Skin Display

This paper describes heterogeneous integration technologies of micro-LEDs on 3D-IC dielets for Smart Skin Display as a healthcare flexible hybrid electronics (FHE) device to be fabricated based on die-first fan-out wafer-level packaging (FOWLP). Die-level Through-Silicon Via (TSV) formation is demonstrated by spray-coating photolithography and seed-layer deposition with a standard magnetron sputtering system. In addition, SAP (Semi-Additive Plating process) bonding is also demonstrated at room temperature to interconnect the Cu-TSV and Au electrodes on 0.1-mm
³
cubed blue micro-LEDs. This process successfully stacks the micro-LEDs onto the 3D-IC dielet, enabling them to be driven through electroplated Cu pillars. The yield of SAP bonding is enhanced up to over 90% by optimizing the processes using room-temperature OER (ozone-ethylene-radical)-CVD SiO
2
and excessive electroplated Cu growth control techniques.