High Thermally Conductive, High-Speed Deposition of AlN by Bipolar High Power Impulse Magnetron Sputtering

In advanced 3D monolithic packaging practices, the gap filling between dielectric chips is typically performed by PECVD SiO2, which has a thermal conductivity of 1 W/m-K, hindering effective thermal management. Substituting SiO2 with polycrystalline AlN could result in more than a 100-fold enhancement in thermal conductivity while maintaining a relatively low leakage current. However, achieving this substitution requires a low-defect density, high-speed deposition of AlN at low temperatures (. High-power impulse magnetron sputtering (HIPIMS) plus a reverse positive kick is a form of high-energy physical vapor deposition involving bipolar pulsing. In this study, single-texture 1-micron AIN film with a thermal conductivity of 121 W/m K was successfully deposited with a growth rate of 25 nm/min using an advanced bipolar HIPIMS plus Kick pulse generator on a native oxide-free Si (111) substrate. The substantial plasma current (50 A at peak) and a slight reverse positive target bias (+25V) are applied to ensure that 90% of the Al and Ar atoms are ionized with the precise controlled energy, leading to the maximization of the material's capacity for heat dissipation as measured by frequency domain thermoreflectance (FDTR).