Size and Performance Tradeoffs in Micro-Inductors for High Frequency DC-DC Conversion

This paper presents the design and measurement of optimized inductors-on-silicon (micro-inductors) for use in high frequency dc-dc conversion applications. These ultra-compact low profile (< 70 mu m) inductors range in area from 0.5-2.5 mm(2). The design process utilizes optimization software that finds the optimal physical dimensions, to maximize inductor efficiency, given certain technology constraints. Optimized micro-inductors achieve measured inductance densities of 66 nH/mm(2) for a 2.5 mm(2) area, 110 nH/mm(2) for 1.3 mm(2) device and 82 nH/mm(2) for a 0.5 mm(2) footprint area. Measured saturation currents range from 0.15-0.5 A for the optimized devices.