Analysis Of Electrical Transmission Characteristics Of Coaxial Through Silicon Vias Based On Carbon Nanotube

With the continuous increase of the signal frequency of integrated circuit,the resistivity of metal copper increases sharply,and the traditional through silicon via has serious electrical transmission problems.At this time,simply changing the structure of TSV,such as using coaxial TSV structure,will still be limited by copper.Compared with copper,carbon nanotubes have larger current carrying capacity,higher thermal conductivity,stronger mechanical strength and superior conductivity along the axial direction.Meanwhile,they have good inhibition effect on skin effect and electromigration,which is expected to replace copper as a new generation of interconnection materials.Therefore,in this paper,the electrical transmission characteristics of coaxial TSV based on carbon nanotubes are studied.Firstly,considering MOS effect,skin effect and substrate eddy current loss effect,the equivalent circuit model of coaxial TSV is established based on the most basic electrical formula,and the accuracy of the model is verified by the electromagnetic simulation results of actual structure.The simulation results show that the error of insertion loss S21 and return loss S11 is less than 5%.Secondly,combing with the physical mechanism of carbon nanotubes and theory of quantum electronics,the equivalent circuit models of single-walled carbon nanotubes and doublewalled carbon nanotubes are established.At the same time,the equivalent model of single carbon nanotube is extended to carbon nanotube bundles.The equivalent circuit models of coaxial TSV filled with single-walled carbon nanotube bundles and coaxial TSV filled with double-walled carbon nanotube bundles are established,and the electric transmission characteristics of the two are simulated and analyzed.At 100 GHz,the insertion loss S21 and return loss S11 of coaxial TSV filled with copper are respectively-0.53 dB and-10.89 dB,the coaxial TSV filled with single-walled carbon nanotubes are respectively-0.25 dB and-14.25 dB,and the TSV filled with double-walled carbon nanotubes are respectively-0.35 dB and-11.75 dB.Then,the electrical transmission characteristics of coaxial TSV filled with single type of carbon nanotube bundle are optimized from two aspects of the diameter of inner conducting carbon nanotube and outer conducting carbon nanotube.Finally,in order to optimize the electrical transmission characteristics of coaxial TSV structure filled with carbon nanotube bundles,a new coaxial TSV structure filled with mixed carbon nanotube bundles is proposed,and its RLGC equivalent circuit model is established to analyze the electrical transmission characteristics.The simulation results show that from0.1GHz to 100 GHz,the electrical transmission performance of the proposed coaxial TSV is much better than that of the coaxial TSV filled with a single type of carbon nanotube bundle.Next,the electrical transmission characteristics of the new coaxial TSV structure filled with mixed carbon nanotube bundles are optimized from three aspects: the scale factor,the diameter of inner conducting carbon nanotube and the diameter of outer conducting carbon nanotube.