Study On The Filling Mechanism And Technology Of Through Silicon Via

TSV(Through Silicon Via)is an overturning technique,which achieves the vertical electrical interconnection through the filling of copper,tungsten or polysilicon into the vias.This technique breaks through the bottleneck of the 2D integration technique and achieves the 3D integration,which becomes the important research subject and solution of the continuation and expending the Moore Law.This makes the manufacture of the miniature and high performance devices possible.Although several high-end products using TSV have emerged,there is still a long way to improve the performance and reliability of TSV.TSV faces many difficulties and there is still plenty of room to improve.In this dissertation,targeting on the via filling mechanism and application developing,blind via and through via filling mechanism,influence factors,via filling process optimization,microstructure and mechanical properties of Cu-TSV,and silicon interposer fabrication are studied.The major contributions of this dissertation are as follows:In order to investigate the properties of additives developed specifically for TSV filling,the electrochemical workstation is used.The texture coefficients of deposits are characterized using XRD technique.Effects of the kind of additive,current density,and seed layer on the texture coefficient are also studied.The diffusion-adsorption-desorption-incorporation theories and the arbitrary Lagrange-Eulerian(ALE)method are combined for the first time,and the blind and through via filling models suitable for sub-micro and micro dimension are built.The via filling evolution and mass transport are simulated with different doses of additives.The effects of TSV structure and dimension on the via filling model are simulated.At last,the vias are electroplated to verify the rationality of the models.The electron backscattering diffraction(EBSD)technique is used to investigate the microstructure of Cu-TSV,and the additive distribution in via during via filling process is analyzed and speculated according to the EBSD testing results.The micro-area XRD technique is used to characterize the micro-area texture of CuTSV.The additive distribution along the via depth direction is calculated and the V-shape via filling mechanism is elaborated according to the(111)texture coefficient changes in different area.The electrochemical test,simulation,and morphology investigation methods are used to verify that additives are desorbed in via bottom when the local current density is larger than the crucial current density,which explains the bottom-up filling model.The effects of several prominent factors(the forced convection,via dimension,electric field distribution,electrolyte temperature,thickness of the seed layer,pre-wetting,structure of scallop)on the TSV filling model are investigated through the simulation and via filling experiments.The TSV filling processes are optimized,and the vias with different aspect ratio in one chip are filled simultaneously.The multi-steps filling process is proposed.The accelerators are added in the pre-wetting electrolyte and make the accelerators diffuse into via in advance and adsorb on the via surface,and then the pre-wetting chip is electroplated in the electrolyte only with suppressor,which not only achieves the bottom-up filling model,but also enhances the via filling efficiency.The dry film photoresist process and through via filling process are combined to develop an innovative and effective process for manufacturing the silicon interposer(dry film development and insulation process),which simplifies the process,lows the costs,and enhances the reliability of electrical connection.Through the above research on TSV filling mechanism,blind and through via with submicro or micro dimension simulation,via filling optimization and influence factors,CuTSV microstructure,and the fabrication of silicon interposer method,the TSV filling mechanism is illustrated profoundly and the high-effective via filling process with large dimension and different aspect ratio are achieved.An innovative approach for fabrication the silicon interposer is developed.This dissertation provides a solid foundation for the future application of TSV.