Research And Application Of Silicon-based Radio Frequency Spiral Inductor Model

In recent years,the innovation of wireless communication technology is advancing with each passing day,the scale of mobile communication market continues to grow,and the ultra-large scale integrated circuits with CMOS silicon process as the mainstream have been widely used.Silicon based spiral inductors are commonly used in RF ICs and their performance is critical to the whole IC.The more advanced the process technology,the smaller the circuit size,but the area of the inductor does not decrease with the progress of the process technology.So the more advanced the process,the higher cost of the inductor manufacturing.What’s more,the advanced process does not provide a continuously adjustable parametric model of the inductor.It is critical to establish an accurate inductor model for efficient circuit simulation.In this paper,we worked on the simulation design,equivalent circuit model,parameter extraction,and inductor preparation of silicon-based RF spiral inductors.First,three commonly used EM software,CST,ADS（Momentum）and EMX,are introduced and compared.The simulation design of planar spiral inductors,multilayer spiral inductors and three-dimensional integrated inductors is carried out based on CST Microwave Studio.The effects of coil turns and internal diameter on the performance of planar spiral inductors,the effects of double-layer spiral spacing and substrate conductivity on the performance of multilayer spiral inductors,and the effects of heterolateral TSV spacing and TSV insulation layer thickness on the performance of three-dimensional integrated inductors are investigated respectively.Secondly,a compact singleπmodel is adopted,which is based on the traditional singleπmodel of inductor with the addition of R-L parallel network to characterize the skinning effect and proximity effect and R_sub-C_sub network to describe the substrate coupling effect.The frequency band is divided by specifying the normalized amplitude of the inductor to reasonably simplify the equivalent circuit,and the parasitic parameters at low,medium and high frequencies are extracted by using the proposed linear function analysis method.The validation results show that the extracted equivalent circuit model is well fitted in the range of 0～40 GHz.Third,the preparation of silicon-based spiral inductor is completed in the laboratory based on a three-layer metal,high-resistivity silicon substrate process.The effect of the variation of coil inner diameter and metal wire width on the inductance performance is analyzed by two sets of controlled experimental results.Then an inductor with N=6.5,W=50μm is used as an example to verify the compact singleπmodel.The problems encountered during inductor preparation are presented,analyzed and discussed,and solutions are proposed to improve the yields of inductor.