【作者】 刘锋；

【导师】 于军；

【作者基本信息】 华中科技大学 ， 微电子学与固体电子学， 2005， 博士

【摘要】 高性能射频(Radio Frequency, RF)集成微电感是移动通信应用中需求很高的无源器件。目前,低成本、高性能、高集成度RF微电感的缺乏阻碍了单片射频SOC(System on Chip)集成电路的实现。磁材料集成到微电感中不仅可增加电感感值,也可有效减少线圈磁漏,是实现高性能RF集成微电感很有前景的一种方法。本论文深入系统地研究了高频铁氧体薄膜磁性能及制备工艺,在此基础上,首次采用标准硅集成工艺实现了基于铁氧体RF集成磁膜微电感,实验结果表明铁氧体磁膜的引入可有效提高RF平面微电感的整体性能。论文首先对RF平面微电感的物理模型进行了研究,给出了平面电感Q值和L值的计算方法,从模型出发分析了电感结构和材料参数对电感L、Q值的影响。在此基础上,针对高电阻率铁氧体磁材料的特点,得到了磁膜微电感等效电路模型及适合于集成磁膜微电感L值与Q值的计算表达式,并使用等效模型详细地分析了铁氧体磁膜的引入对RF平面微电感性能的影响,为铁氧体应用到磁膜集成RF微电感打下理论基础。仿真结果表明高频磁导率和高频介电常数对电感高频性能同等重要,只有选取高磁导率、低介电常数的铁氧体材料才能提升RF微电感的整体性能。同时,使用部分元等效电路法(Partial Element Equivalent Circuits, PEEC)解决了射频频段微米尺度金属损耗的精确计算问题,为预测、设计和优化片上螺旋电感提供了一种有效的电磁仿真方案。接着,研究了使用溶胶-凝胶(Sol-gel)自燃法制备的NiCuZn、YIG、CoZrO铁氧体高频电磁性能,测试结果表明这些材料在高频下具有低的磁损耗和介电损耗,而NiCuZn、CoZrO铁氧体截止频率大于1GHz,适合于RF集成微电感的应用要求。在此基础上,使用sol-gel法结合快速热处理(Rapid Thermal Processing, RTP)工艺制备了软磁性能良好的NiCuZn、YIG铁氧体磁膜,通过对磁膜样品表面形貌、晶相结构及准静态、高频磁性能的测试,详细研究了组分、溶胶-凝胶法、RTP退火工艺对铁氧体薄膜性能的影响,获得了优化的工艺条件。实验结果表明:sol-gel技术有效降低了磁膜晶化温度,在溶胶摩尔浓度尽可能高的条件下,制备样品可得到相当于体材的静磁性能; sol-gel法结合RTP工艺可有效地实现磁性薄膜的低温集成工艺,为将磁性薄膜集成到RF微电感打下基础。论文对集成磁膜微电感制作涉及的关键工艺进行了研究与开发,其中有磁性薄膜的刻蚀工艺、聚酰亚胺薄膜的制备与刻蚀技术及电镀Cu工艺。在磁膜图形化工艺研究中,比较了多种刻蚀工艺,得到了适用于铁氧体磁膜的刻蚀工艺; 研究了聚酰亚胺更多还原

【Abstract】 High performance RF integrated micro-inductor is a highly desired passive component for wireless communication applications. To date, lack of miniature IC inductors with low lost and high performance hinders realization of single chip RF SoC. Magnetic materials integrated into micro-inductors can not only heighten the inductance but also reduce the magnetic loss of inductors. It is a promising way to realize the high performance integrated micro-inductors through the integration of magnetic materials into inductors. In this thesis, the magnetic performance and fabrication processes of ferrite thin-films for high frequency have been studied. Based on these studies, the RF planar micro-inductors with ferrite thin-films are first fabricated by using standard Si integrated technology. The experimental results show the integration of magnetic materials into inductors can enhance the whole performance of RF planar micro-inductors effectively. Firstly, a physical model of planar inductor is introduced. Based on this model, analytical formulas used for the calculation of Q factor and inductance is obtained, and the analysis of the impact factors, such as inductor size and material parameters, to the inductor L and Q value are further performed. Considering the high resistivity of ferrite, an equivalent circuit model of planar inductor with magnetic thin-films and the formulas for the calculation of L and Q value of the inductors are achieved. Based on the equivalent circuit model, the affection of ferrite magnetic thin-films on the performance of RF planar micro-inductors are investigated systematically, which is the theoretical foundation for realizing the integrated inductor with ferrite thin-films. The simulated results show that high-frequency dielectric constant is the same important as the high-frequency permeability of the magnetic materials that are applied for the RF integrated inductors. The ferrite materials with high permeability and low dielectric constant are suitable to the integrated inductors. Using partial element equivalent circuit method provides an accurate means used for the calculation of metal loss in RF frequency meantime. Secondly, the high-frequency properties of NiCuZn, YIG and CoZrO ferrite that fabricated by using a sol-gel auto-combustion process are investigated. The experimental results indicate the materials possess low magnetic loss and dielectric loss. The resonant frequency of NiCuZn and CoZrO ferrite is higher than 1 GHz, which is suitable to RF integrated inductors. Based on the studies, high quality NiCuZn and YIG ferrite thin films are fabricated by using sol-gel method and rapid thermal processing. The effects of the film composition and the fabricated processing parameters on the phase identification, the surface morphology and magnetic properties of the ferrite thin-films are investigated systematically. A set of optimal processing parameters is obtained. The experimental results show that sol-gel method can lower the crystallization temperature effectively and the magnetic properties of thin-films are almost identical with the bulk materials when the sol concentration for the fabrication of the thin-films is enough. Using sol-gel method in conjunction with RTP is useful to achieve the low-temperature integrated fabrication of magnetic thin-films, which is the fundament for the realization of the integrated inductor with ferrite thin-films. To realize the designed planar RF micro-inductor with ferrite thin-films, several key processes have been developed, among which are the etching of magnetic thin-films, polyimide layer preparation and dry etching, and copper electroplating. In the course of research, the etching process suitable for ferrite magnetic films is obtained through the comparison of several etching techniques. Meanwhile, we studied the formation and dry etching of polyimide films, which is used as dielectric layer between inductor coils and underpass lead. To fabricate thick copper coils, a selective copper electroplating on seed layer with resist as structural mold is established. The main process steps include seed layer sputtering, lithography of thick photoresist, copper electroplating and seed layer removal. These key processes are compatible with standard Si integrated process. Based on the structure design and technology process, the planar micro-inductor patterns based on magnetic films with the single metal layer or dual metal layers are designed separately. The fabricated processes course compatible with Si integrated process is developed for the planar micro-inductors with magnetic thin-films. The successful planar micro-inductors is fabricated. The process results show the integration of magnetic films into micro-inductors for IC is quite viable. Finally, the high frequency testing of the micro-inductor samples is performed. The effects of PAD style for measuring, the structure and material parameters of inductors on high-frequency performance of inductors are investigated systematically by using the obtained experimental data. Comparison with the simulated results shows the equivalent circuit model can satisfy design accuracy of planar inductor below 5 GHz. The comparison between the samples based on YIG, NiCuZn and CoZrO ferrite magnetic thin-films withthe referential inductors that don’t include magnetic thin-films is carried out. A typical inductor sample with CoZrO thin-film is presented. The inductance is raised by 25% and the quality factor is raised by 23%, compared with the inductor, which doesn’t include ferrite thin-film.更多还原