GaN FinFET 3DHI Microsystems

B. Lu
Finwave Semiconductor, Inc.,
United States

Keywords: GaN, 3DHI, 5G, 6G, advanced packaging, antenna-in-package


Wireless communications and power management applications offer significant opportunities for high-volume U.S. semiconductor manufacturing, sustainable technological superiority, improving energy efficiency and workforce development. 5G/6G, satellite communications and power microsystems serve both strategic defense and high volume commercial markets. They indirectly improve “digital” semiconductors by meeting rapidly escalating communications, power delivery and thermal management challenges that constrain performance. They have different requirements from “digital” semiconductors. They do not benefit from scaling to advanced CMOS nodes or require ultra high count of densely packed I/O. Instead, they require three-dimensional heterogeneous integration (3DHI) of large arrays of separately manufactured and optimized gallium nitride (GaN), silicon and passive components, Wireless and power applications require leap-ahead innovations in holistic co-design, the manufacturing ecosystem and metrology to meet their extremely challenging performance (operating speed and power density), energy efficiency and cost targets, in these areas: 1) Semiconductors Devices. Finwave Semiconductor’s GaN-based fin-field-effect transistors (FinFETs), overcome the limitations of conventional planar transistor structures. Thanks to the 3-dimensional gate electrostatic control, the GaN FinFET structure offers significant improvement in linearity, short channel effects and memory effects. This new technology has a great potential to enable high efficiency 5G/6G wireless communications and advanced power management architectures. Fabricating GaN FinFETs using mature 8” and 12” silicon wafer fabs significantly reduces cost and brings “Moore’s law” scaling to GaN with ultra-scaled devices for continuous performance improvement. 2) Multiple levels of 3DHI to minimize the path lengths, parasitics and power loss between separately manufactured components which is essential to achieve the wireless and power applications’ performance targets. The first-level of 3DHI heterogeneously integrates a large arrays of ultra-thin GaN FinFET die onto 300mm silicon wafers containing digital and mixed-signal silicon circuits. Multiple layers of copper interconnects reduce electrical and thermal resistance and bridge the gap between the fine-pitch, thin wafer fab’s interconnects and downstream coarse-pitch, thick panel interconnects. The resulting 3DHI “die” can be tested prior to subsequent integration. The second-level 3DHI uses panel-level processes to heterogeneously integrate large arrays of diverse known good 3DHI die on large-area glass substrates with passive components, through glass vias and multiple thick copper interconnect to further reduce electrical and thermal resistance. Application examples include large arrays of GaN power amplifiers with RFSOI beamformers with patch antennas on glass substrates for 5G/6G and satcom applications or large arrays of GaN power transistors, SOI gate drivers and capacitors on glass substrates for power applications. Some applications, such as power, may include a third level of 3DHI which integrates known good GaN-on-SOI-on-glass components into a System-in-Package (SiP) using advanced packaging. 3) Metrology: New metrology technology is required to cost-efficiently verify the devices’ target physical and electrical properties at optimal points in the GaN FinFET wafer fab and multiple levels of 3DHI manufacturing flow. The wireless and power 3DHI microsystems’ operating frequencies and power densities are significantly higher and their manufacturing flows are significantly different than today’s state-of-the-art which offers many opportunities for the U.S. semiconductor industry.