Diamond-Incorporated Flip-Chip Integration for Thermal Management of GaN and Ultra-Wide Bandgap RF Power Amplifiers

Abstract

GaN radio frequency (RF) power amplifiers offer many benefits including high power density, reduced device footprint, high operating voltage, and excellent gain and power-added efficiency. Accordingly, these parts are enabling next-generation technologies such as fifth-generation (5G) base transceiver stations and defense/aerospace applications such as high-performance radar and communication systems. However, these benefits can be overshadowed by device overheating that compromises the performance and reliability. In response to this, researchers have focused on GaN-on-diamond integration during the past decade. However, manufacturability, scalability, and long-term reliability remain as critical challenges toward the commercialization of the novel device platform. In this work, a diamond-incorporated flip-chip integration scheme is proposed that takes advantage of existing semiconductor device processing and growth techniques. Using an experimentally validated GaN-on-SiC multifinger device model, the theoretical limit of the cooling effectiveness of the device-level thermal management solution has been evaluated. Simulation results show that by employing a ~ 2-μm diamond passivation overlayer, gold thermal bumps, and a commercial polycrystalline carrier wafer, the power amplifier's dissipated heat can be effectively routed toward the package, which leads to a junction-to-package thermal resistance lower than GaN-on-diamond high electron mobility transistors (HEMTs). Furthermore, simulation results show that this approach is even more promising for lowering the device thermal resistance of emerging ultra-wide bandgap devices based on β-Ga <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> and AlGaN, below that for today's state-of-the-art GaN-on-diamond HEMTs.