Research On Electrical Model And Transmission Characteristics Of Through-silicon Vias For 3D ICs

In the past fifty years,semiconductor technology has been continusly developed in the way of smaller size,lower consumption and higher performance driven by Moore's law.However,as feature size shrinks to deep submicron,the problems induced by interconnect,such as,power consumption,heat dissipation and delay are becoming increasingly prominent.Then,interconnect technology has become a bottleneck restricting the further continuation of Moore's law.Therefore,many methods are proposed to solve this problem.Among them three-dimensional integrated circuit(3D IC)is widely regarded as the most potential one.Through-silicon-via is the core technology of 3D IC that provides vertical interconnection between the stacked chips.In this dissertation,the electrical model and transmission performance of several novel TSV structures are studied in detail,and the main academic contribution is summarized as follows.In chapter 2,Closed-form expressions of the parasitic insulator capacitance and the substrate capacitance for tapered through-silicon vias(T-TSVs)are proposed.First,the expressions are deduced by solving Maxwell equations.The maximum percentage errors between the calculated and simulated results for the insulator capacitance and the substrate capacitance are 1.86% and 3.75%,respectively.Then,based on the expressions,the equivalent circuit model of a T-TSV signal-ground(S-G)pair is established.Furthermore,the electrical characteristics of the T-TSV are evaluated using the model.The results indicate that the T-TSV has longer latency and less crosstalk than the cylindrical TSVs.Finally,the crosstalk of two types of T-TSV arrays is analyzed and the applicability of the two expressions is discussed.Then,based on the expressions,the equivalent circuit model of a T-TSV signal–ground(S-G)pair is establishedIn chapter 3,a novel TSV,named partial coaxial TSV,is proposed to suppress the substrate noise induced by TSV.In this structure,the via is surrounded by a BCB layer,and a grounded metal ring is placed at one end outside the BCB layer.It can be seemed as partial shielded coaxial TSV and it is easier to process than coaxial TSV.The BCB layer can effectively reduce the leakage of the signal to the substrate,and the metal ring provides a low impedance path for the substrate noise.Frequency domain analysis results indicate that this structure has larger |S21| and less near-end crosstalk compared with the traditional TSV,TSV with p+ layer and TSV with p+ guard ring.Additionally,time domain analysis results show that the substrate peak noise voltage of this structure is obviously reduced compared with the two methods above.In chapter 4,the multi-walled carbon nanotube bundle(MWCNTB)filled shielded through-silicon via(S-TSV)is proposed and its equivalent circuit model is established.Then,the electrical characteristics including the S parameters,attenuation constant and time delay are investigated using the model.The results indicate that the MS-TSV(MWCNTB filled S-TSV)has a larger |S21|,smaller attenuation and shorter time delay compared with the copper filled S-TSV(CuS-TSV).In addition,the expression for the equivalent conductivity of MWCNTB(?MWCNTB)is simplified,and the sensitivity coefficient of ?MWCNTB is defined.The analysis shows that the outermost shell of MWCNT has the most significant impact on ?MWCNTB.Also,the minimum packing density of MWCNTB satisfying ?MWCNTB ? ?Cu has been deduced,and guidelines for the geometrical parameters of MS-TSV that satisfy ?MWCNTB ? ?Cu are obtained.Finally,the impact of quantum capacitance(Cq)of CNT on the transmission performance of S-TSVs is analyzed.The results show that the transmission performance of S-TSV filled with BCB insulation layer and MWCNT bundle above 20 GHz can be significantly improved by Cq.In addition,the performance of S-TSVs with silicon insulation layer can also be dramatically improved by Cq.Besides,the temperature effect of silicon can be balanced by Cq such that the heat stability of S-TSV with silicon insulation layer is improved.In chapter 5,the electrical model of MWCNT-based through-silicon vias(MWCNT-TSVs)is established considering the temperature effects of the mean free path,metal-oxide-semiconductor(MOS)capacitance,substrate conductance and number of conducting channels of multi-walled carbon nanotube(MWCNT).Then,Based on this model,the propagation constant,forward transmission coefficient S21 and crosstalk at different temperatures are calculated.By analyzing the phase constant,the zero dispersion transmission(ZDT)condition is obtained.According to this condition,the guidelines on how to select the substrate in different level integrations are proposed.Furthermore,a concise formula for the equivalent conductivity of MWCNT is proposed.Also,the expression of the minimum diameter of MWCNT-TSV whose attenuation is less than that of copper-filled TSV has been deduced.