时间：2012年12月12日（星期三）下午3：00

地点：博逸楼（西六教）401会议室

报告人：邢星

个人简介：

Xing Xing received the B. S. degree in Physics from Nanjing University, China, in 2006, and the Ph.D. degree in Electrical and Computer Engineering from Northeastern University, Boston, MA, in 2011. Her Ph.D study mainly focused on the soft magnetic materials and devices on energy applications. Xing has authored 16 journal papers and a book chapter. She is currently a device engineer with the iCoupler® group at Analog Devices, Inc., Wilmington, MA. Her responsibility includes the development of the next generation of the on silicon integrated transformers.

题目：High Bandwidth Low Insertion Loss Solenoid Transformers Using FeCoB Multilayer

摘要：

High Bandwidth Low Insertion Loss Solenoid Transformers Using FeCoB Multilayer

Xing Xing

Analog Device, Inc., Wilmington, MA, USA

Portable electronic device development has been driving the on-chip power supply integration. The main barrier is the integration of magnetic components such as inductors and transformers. Air-core spiral transformers can be easily integrated, but they suffer from low inductance and require operating frequency as high as 200 MHz to 300 MHz. Therefore, high switching loss and electromagnetic (EM) emission can be of concern. High permeability magnetic core can be used to enhance the inductance and quality factor so that the operating frequency can be lowered down to 2 MHz to 30 MHz, which also reduces the switching loss and EM emission. However, magnetic core may also bring additional core loss, like eddy current loss and hysteretic loss. Magnetic multilayer is often used to reduce the eddy current core loss and the magnetic anisotropy has been proposed to be able to reduce the hysteretic core loss by generating a hard axis along the magnetic field switching direction in the core.

A solenoid inductor and four solenoid transformers using multi-layered FeCoB magnetic cores were designed, fabricated and characterized with different winding and core structures. All transformers have 10 turns for both the primary and secondary windings. The cores have a dimension of 2.4mm by 2mm. The turn width is 94um and separation is 20um. The inductor has similar dimensions but with 14 turns. With the 3µm FeCoB/Al2O3 multilayer film loading, a factor of 9.3 and 8.7 improvements in the inductance and quality factor, respectively, were observed in the measurement of the inductor. Material study show that the permeability of the magnetic thin films depends very much on the substrate surface roughness. Transformer II, with the primary and secondary windings on each end of the bar shape core, has the highest inductance of 53 nH as well as a quality factor of 2.7 at 20MHz. Transformer III, which had interleaved windings and patterned core, exhibited the highest coupling constant of 0.9 and the lowest minimum insertion loss of -7.9dB up to 50MHz, as well as the best comprehensive performance. Further work such as polyimide surface planarization before the magnetic deposition will be done and the improved permeability will provide a more promising transformer performance.