Low Thermal Budget Growth of Near‐Isotropic Diamond Grains for Heat Spreading in Semiconductor Devices

Abstract The ever‐increasing power density is a major trend for electronics applications from dense computing to 5G/6G networks. Joule heating and resulting high temperature in the device channel due to the increased power density results in performance degradation and premature failure. Diamond integration near the hot spot can spread the heat by increasing the heat transfer coefficient. Diamond is mostly grown at high temperatures (700–1000 °C), which limits its integration with many semiconductor technologies. Here, a high‐quality 400 °C‐diamond by modifying the gas chemistry at different nucleation stages, with a sharp sp³ Raman peak (FWHM≈6.5 cm⁻¹) and high phase purity (97.1%), similar to 700 °C‐diamond (>98%) is demonstrated. An average grain size of 650 nm with a thickness of 790 nm corresponding to an anisotropy ratio of 1.21 at 400 °C close to the best‐reported of 1.12 at 700 °C is achieved. This near‐isotropic diamond exhibits a relatively high thermal conductivity of ≈300 W m⁻¹ K⁻¹ and a thermal boundary resistance as small as only 5 m²K G⁻¹ W⁻¹ (on SiO₂ and Si₃N₄). Achieving such a high‐quality diamond at 400 °C demonstrates the possibility to grow the diamond on a wide range of semiconductors including Si, InP, Ga₂O₃, SiC, and GaN where SiO₂ or its variations, and Si₃N₄ are commonly used dielectrics.