Design,Modeling,and Simulation Of Novel Interconnects Based On Carbon Nanomaterials

As the feature size of the integrated circuit is continually scaling down,the problems of conventional Cu interconnects(e.g.,resistance increase and reliability degradation)are becoming more and more severe.Therefore,it is necessary to search and develop novel interconnect technology for next-generation ICs.Carbon nanomaterials,owing to their many unique physical properties,have attracted significant research interest in the past decades.The interconnects based on carbon nanomaterials are viewed as an potential solution to alleviate the challenges faced by conventional Cu interconnects.It is anticipated that carbon-based interconnects can satisfy the requirements including low time delay,high ampacity,and less thermal effects In this thesis,structural design and performance optimization of carbon-based interconnects have been carried out.The circuit models of vertical graphene nanoribbon(VGNR)interconnects,Cu-graphene heterogeneous interconnects,and Cu-carbon nanotube(Cu-CNT)composite interconnects have been established.The comparable analysis of signal transmission,thermal propeity,and noise issue is provided between conventional Cu interconnect and novel carbon-based interconnects.This thesis can be divided into three parts:In the first part,to guarantee signal integrity,the concept of differential CNT interconnects is presented and studied.The equivalent circuit model of the differential CNT interconnects is developed and simplified.By virtue of the circuit model,the signal transmission through the differential CNT interconnects is investigated.Moreover,two types of driver-load schemes,i.e.,voltage-model signal(VMS)and current-mode signal(CMS),are considered.For both two types of driver-load schemes,the influences of process-induced variations on the signal transmission through the differential CNT interconnects are evaluated.In the second part,the concept of VGNR is proposed.Based on the developed circuit model,the electrical and thermal properties of the VGNR interconnects are studied.Furthermore,considering the doping techniques,the comparable analysis of signal transmission between doped horizontal graphene nanoribbon(HGNR)and doped VGNR interconnects are conducted.It is demonstrated that the implementation of VGNR interconnects can significantly improve the electrical performance,and alleviate the thermal dissipation problems induced by HGNR and CNT interconnects.In the third part,considering the high ampacity of carbon nanomaterials and relative mature fabrication technology of conventional Cu interconnect,the concept of Cu-carbon nanomaterials composite interconnects are proposed.The equivalent circuit models of Cu-graphene heterogeneous interconnects and Cu-CNT composite interconnect are presented,respectively.In Cu-graphene heterogeneous interconnects,graphene is utilized as a barrier preventing Cu atoms diffusion into surrounding dielectric.Based on the equivalent single-conductor transmission line(ESC-TL)model,the circuit parameters including scattering resistance,quantum capacitance,and kinetic inductance,are extracted.The signal transmission and electro-thermal properties of the Cu-graphene heterogeneous interconnects are captured and analyzed.Further,the CNTs are doped into the Cu conductor to enhance the current carrying capacity.Therefore,the Cu-CNT composite interconnects can have both large electrical conductivity and high ampacity.The signal transmission and stability of Cu-CNT composite interconnects are investigated.Moreover,the crosstalk issue of two and three coupled Cu-CNT composite interconnects are studied.In summary,this thesis is trying to search alternative interconnect technology to cope with the challenges faced by conventional Cu interconnects.By utilizing the carbon nanomaterials,it can be anticipated that the performance and reliability of interconnects can be improved significantly.The circuit modeling and performance analysis of these carbon-based interconnects are conducted.