基于MEMS技术研制RF硅基微电感线圈

RF Micro-inductor of Si Substrate Based on MEMS Technology

在分析了硅基上金属线圈的串联电阻、金属层厚度等在低频和高频的情况下对Q的影响及原因的基础上,提出了一种在硅杯表面采用浓硼扩散区与镀金属膜形成的欧姆接触电极作为内引线的硅基电感的新制造方法。设计了硅基电感的版图尺寸和相关的工艺流程,用IntelliSuite软件模拟验证了工艺流程的可能性,再利用Ansys有限元软件中的电磁分析模块模拟了电流与磁感应强度的关系、衬底涡流分布等,为平面电感的理论与实验的进一步比较分析提供了参考依据。在研制过程中发现影响电感性能好坏的主要因素是衬底涡流效应,为此提出了在矩形硅杯膜上制作电感的方法,为了进一步减薄金属电感线圈衬底的厚度,在硅杯膜背面采用激光打孔得到了膜厚约为5μm的衬底,从而可以使衬底中的涡流大幅度减少、电感的Q值得到很大提高。此外,提出的新制造方法采用了绝缘性能比SiO2好的Al2O3薄膜作为电感线圈与衬底之间的绝缘层。结果表明,设计的平面螺旋电感具有制造工艺简单、与IC工艺相兼容的优点,有广泛的应用前景。

The factors on quality factor either in low or high frequency are analyzed in this paper,the kinds of inductor configurations,including suspend spiral inductors,solenoid inductors,vertical planar inductors are studied.A new kind of method of inductor fabrication is proposed,whose internal down-lead adopts ohm contact formed by the boron heavily doped region and the Au evaporated.The related fabrication process and the scale of mask for inductor on silicon,and validate the feasibility by the Intelli Suite soft are designed,then simulate the relations of carrent versus magnetic Flux Density by Ansys soft and the distribution of eddy are proposed.All of these simulations provide reference for further compare and analyse for theory and experiment of planar spiral inductor.During the process,the crucial factor of the performance of planar spiral indcuctor is found out,that is eddy effect on substrate.To fabricate the inductor on the silicon cup,then dig holes on the back of silicon cup by laser to further reduce substrate thickness.As a result,the substrate thickness reachs 5 μm,which can greatly reduce eddy effect and increase quality factor.Moreover,we adopt Al2O3 as the dielectric film between the coils and substrate,whose dielectric performance is better than SiO2.As conclusion shows that our planar spiral inductor has the advantages of simple technology and compatibility with IC technology,and that it has extensive future.