A comparative analysis of monolithic spiral inductors in silicon bipolar technology

In this paper, a low-cost silicon bipolar technology was exploited to investigate the performance trade-offs of monolithic inductors for both low-noise and power applications. Adding few fabrication steps to the standard process it was possible to evaluate the effect of buried layer removal on inductor performance. Several vertical structures including removed buried layer, metal and buried layer patterned ground shield were analyzed and compared to honeycomb oxide trenched buried layer, which was considered as reference. An improvement of the quality factor as large as 32%, with respect to the reference, was observed for the low-noise inductor with a buried layer patterned ground shield structure. Removing the buried layer was found to be the optimum solution for the power inductor, which exhibits a quality factor as high as 14 and a 33% improvement with respect to the reference.