True 3D Packaging Solution for Stacked Vertical Power Devices

This paper presents recent advances and breakthroughs of an alternative 3D packaging solution for vertical power devices. Direct bonding technology and trench isolation used for power device islanding are the cornerstone of this scheme of integration. Involving direct copper bonding layers, the technology is used during the mid-process to enable the wafer level bonding of vertical power devices to a joint metallic substrate while optimizing the devices intrinsic performances. Wafer level islanding and interconnect is used to simplify and guarantee the true 3D assembly at module level. This 3D assembly is based on the interconnect of matrices of low side and high side vertical power devices on top of each other. Our technology optimizes component surface height as well as alignments constraints. As a result, the true 3D integration of the active parts for power converters is optimized to the highest possible level, leading to strongly reduced EMI levels and increased switching speed capabilities. Key challenges, both on design, fabrication and implementation are presented, and the first prototypes based on four switching cells of vertical 500V power diodes and MOSFETs are introduced.