Basic Characteristics of Thin-Film Single-Layer Coreless Micro-Transformers for Digital Isolators

The development of new power semiconductor devices such as SiC with high withstand voltage, high speed, and high temperature immunity requires the control signal isolators used in them to have similar endurance characteristics. In order to meet this demand, in this research, we devised single-layer coreless micro-transformers manufactured on silicon substrates. Since these transformers have primary and secondary windings formed in the same layer, the withstand voltage can be easily increased by increasing the distance between the windings in the surface direction of the chip. In this paper, the theoretical equations of the inductance, parasitic resistance, and parasitic capacitance of the devised transformer are derived. Furthermore, comparisons between the calculation results of the S-parameters by these equations and the measured values are described.