Analysis And Optimization Of Electrothermal Characteristics Of Through-silicon Vias In 3D Integrated Circuits

To continue the Moore's law,the three-dimensional integrated circuits(3D ICs)take full advantage of spatial dimension and solve the problems about data transmission bandwidth,chip power consumption and speed which seriously restrict the development of two-dimensional integrated circuits.In the process of 3D ICs,through-silicon-via(TSV)is the key technology of 3D IC that provides vertical interconnection between the stacked chips.TSV has the advantages of maximizing chip stack density in the z-axis direction,reducing interconnects length and chip area,increasing high frequency characteristics and reducing chip power consumption.However,it still face many challenges in its electrical and thermal performance.With the in-depth study of 3D ICs,using the finite element method to calculate the electrothermal characteristics of large-scale TSV arrays require a large amount of computation time.In order to solve the above problems,this thesis studies the calculation methods,layout optimization,and parameters influence of TSV arrays in 3D ICs,and obtains the following results:1.In this thesis,we present the blended electrical-thermal coupling model of TSV,the model both considering the effect of lateral thermal resistance and the vertical thermal resistance.Accurate analytical model for the electrical-thermal coupling are presented and verified by COMSOL.It is shown that the comparison between the results of the proposed analytical formulas and COMSOL shows that the proposed formulas have very high accuracy with a maximum error of 1%,and the computational time of our model is reduced by 95%.Based on the analytical model,thermal performance impacts of various TSV configurations are evaluated,the relationship among temperature,thickness of dielectric,radius of TSV,and conductor materials of TSV are also studied.2.In this thesis,we present a unified radial point interpolation method(RPIM)to handle TSV electrothermal coupling problems.The traditional meshless RPIM is improved based on the structural characteristics and physical properties of TSV,the temperature-dependences of material parameters and the self-heating effect are also considered.By selecting the appropriate shape function,we can get the discrete forms of electric and thermal field governing equations.To improve the calculation accuracy,the nodal placement is denser close to the copper core and insulator layer of the TSV,and coarser approaching the silicon substrate.Furthermore,the conjugated gradient(CG)technique is also included in the model to accelerate the algorithm.Based on the proposed method,the thesis is to study the transient electrothermal coupling response of the TSV array.The temperature accumulation effect of a single TSV has been studied under the periodic Gaussian pulses.Furthermore,we investigate the transient temperature response of TSV array,with the effect of thermal coupling being demonstrated clearly.The temperature responses of a two-layered TSV array are also studied.The model consists of TSVs,bumps,and RDLs.The accuracy of the proposed method is verified by the FEM solver COMSOL,and it is demonstrated that for the same accuracy with fine-FEM,the RPIM has a faster computing rate.3.In this thesis,we investigate the electromagnetic crosstalk and thermal crosstalk of array TSVs and propose a parallelogram interleaving stacking layout to optimize both electromagnetic crosstalk and thermal crosstalk.In addition,we present a honeycomb arrangement with shielding TSV array which around the signal TSV,and the coupling noise and temperature distribution are also studied.Based on the parallelogram interleaving stacking layout of TSV array,a structure optimize the multi-layer TSV array is proposed.The coupling noise of the multi-layer TSV array is optimized by the reverse crossing of the top and bottom signal TSV,and the shielding TSVs are also added to multi-layer TSV array further improve the crosstalk effect.4.In this thesis,we present an equivalent anisotropic thermal model to reduce the computational time resulting from complicated numerical integration.The equivalent thermal model is calculated based on equivalent inclusion method and the uniform distribution method,and the model not only considers the physical parameters and material properties of the TSV,microbump and RDL,but also considers the influence of the thermal coupling between TSVs.By introducing the equivalent model,the complex nature of the TSV structure can be overcome.The FEM solver COMSOL is used for comparison with the proposed model,revealing good agreement between the results of the simulation and the proposed models.The maximum deviation is less than 5%,indicating the accuracy of the proposed model,and the computational time of our model is reduced by 95.5%.Additionally,parametric studies and studies of the structure are performed in order to further verify the accuracy of the proposed method and understand the main factors affecting the thermal behavior of a stacked 3D chip.