Measured electrical performance of V-groove inductors for microprocessor power delivery

Thin-film V-groove inductors for microprocessor power delivery are discussed. A 10-MHz, 3.3-V to 1.1-V, 7-A dc-dc converter with V-groove inductors has been predicted to have an efficiency of 88% and power density of 60 W of output power per cm² of substrate area. The first prototype inductors with composite granular Co-ZrO₂ thin-films were fabricated with dimensions smaller than those required for a 7-A converter in order to fabricate them on standard 25-mm silicon wafers. For these prototype devices, we predicted that a 10-MHz, 3.3-V to 1.1-V, 2.1-A dc-dc converter would have 60% efficiency. Measurements on the prototypes indicate that a 2.1-A converter would have 55% efficiency with a power density of 28 W/cm². Measured losses were 23% higher than predicted. We have demonstrated that V-groove inductors can be fabricated with performance close to predicted results.