Novel Integrated BEOL Compatible Inductances for Power Converter Applications

This paper presents the development, processing and investigation of micro-inductances on silicon having an inductance of about 150nH and a resistance of 0.66Ω. The core of the inductances, 1mm x 3.4mm x 0.6mm in size, is fabricated on silicon substrates using a novel fully back-end-of-line (BEOL) compatible fabrication technique based on the agglomeration of micro-sized magnetic powder by atomic layer deposition (ALD). In this way, a wide range of magnetic materials can be integrated on silicon substrates with a high degree of freedom regarding the dimensions of the core. That enables a lot of possibilities for innovative inductor designs for integrated power supplies. A typical boost converter with a GaN FET was designed to prove the functionality of micro-inductances based on such cores at a switching frequency of 20MHz. An input voltage of 15V is boosted to 25V on the output while a load current of 481mA is applied. In this case the converter reaches an efficiency of 87%.