Integrated Ferrite Film Inductor for Power System-on-Chip (PowerSoC) Smart Phone Applications

Abstract

An array of ferrite and air-core inductors was fabricated on silicon wafer to characterize inductor performance. The 1 m and 2.5 m thick ferrite films for the fabrication of inductors were prepared by dc magnetron sputtering. The inductance of the ferrite inductor increased with the thickness of ferrite film from 45.5 nH for 1 m thick ferrite to 50 nH for 2.5 m thick ferrite. The maximum Q-factor was obtained to be 59 at 2.87 MHz from 2.5 m thick ferrite inductor, which is higher than 49.3 at 2.26 MHz for 1 m thick ferrite inductor and 23.2 at 1.56 MHz for air-core inductor. Superimposed dc current of 1 m and 2.5 m thick ferrite inductors was estimated to be 2.5 A and 2.15 A, respectively, corresponding to a 5% drop in L at 10 MHz. In addition, the power efficiency of the buck dc-dc converter based on the studied ferrite inductors was calculated to be 91.7% for 2.5 m thick ferrite inductor and 90.1% for 1 m thick ferrite inductor at load current of 0.647 A.Index Terms-Current capability, dc-dc converter, ferrite inductor, high Q-factor, Ni-Zn-Cu ferrite.

Soft ferrite cores characterization for integrated micro-inductors

“…A lot of research has been carried out to achieve inductor integration on-chip or in-package. Some demonstrators of air-core inductors, such as thin film magnetic inductors and ferrite based ones, have shown that each integration method has its own merits and difficulties [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15]. For on-chip integration, approaches to the fabrication of micro-inductors involving vacuum deposition and electrodeposition of magnetic cores have been demonstrated over the last thirty years.…”