Direct Write 3D-Printed Interconnects for Heterogenous Integration of Ultra Thin Chips

Direct ink writing or printing with high- resolution (well within few micrometres) is gaining attention as for hybrid or heterogeneous integration of electronics on flexible substrates. This technology offers interesting opportunity for realising reliable interconnects for ultra-thin chips (UTCs). This paper presents a single-step method for fabrication of reliable (low-resistivity and high robustness) conductive tracks using extrusion of high-viscosity conductive paste. To demonstrate the potential of the presented approach for bonding of UTCs, a Metal Oxide Semiconductor Field Effect Transistors (MOSFETs) chip was thinned down to 35 ± 0.6 μm. Then, the UTC was attached to a flexible printed circuit board (PCBs) and the metal interconnects are printed to connect the MOSFET devices on chips with extended pads on flexible PCBs. The systematic electrical characterization of MOSFET devices, before and after printing of interconnects, reveals an acceptable level of variation in device mobility (change from 780 to 630 cm2/Vs). The present study open avenues for realising heterogeneous integrated flexible systems for high performance applications.