Direct Integration of Polycrystalline Diamond With 3C‐SiC for Enhanced Thermal Management in GaN HEMTs: Impact of Grain Structure and Interface Engineering
Chiharu Moriyama, Zhe Cheng, Zifeng Huang, Yutaka Ohno, Koji Inoue, Yasuyoshi Nagai, Naoteru Shigekawa, Jianbo Liang
Abstract
Abstract The direct integration of polycrystalline diamond (PCD) with semiconductors is crucial for enhancing heat dissipation in high‐power electronics. However, achieving low surface roughness (<1 nm) remains challenging. In this study, the direct bonding of PCD to 3C‐SiC for GaN high‐electron‐mobility transistors (HEMTs) on a 2‐inch PCD wafer is demonstrated using an advanced bonding technique. The PCD wafer (surface roughness: 2.48 nm) is bonded at room temperature, forming a 7 nm‐thick amorphous layer, which transformed into a 13 nm‐thick polycrystalline SiC layer after annealing at 1100 °C without cracks or separations. Thermal analysis revealed higher thermal conductivity of PCD's growth surface than single‐crystal diamond (SCD). However, the thermal resistance ( R TH ) of GaN HEMTs on PCD is 27% higher than on SCD, attributed to phonon scattering from smaller grain sizes on the nucleation surface. Removing the fine‐grained nucleation layer can enhance heat dissipation. This successful direct bonding of PCD with 3C‐SiC overcomes key integration challenges, enabling improved thermal transport and high‐power device reliability. To fully utilize PCD's thermal advantages, grain size optimization and interface engineering are essential to reduce phonon scattering, improve thermal transport efficiency, and maximize device performance for next‐generation high‐power electronics.