Study Of Thermal Mechanical Reliability Of TSV Based On Dynamic Cu Protrusion Test

The three-dimensional packaging technology based on the through silicon via(TSV)interconnection is considered as the first choice to surpass Moore's law and realize device's miniaturization,high density and multi-function.It has become one of the development directions of the future integrated circuit.TSV is a typical heterogeneous unit with complex materials and internal structure.Under the thermal load,the thermal mismatch between the internal materials and the non-uniform constraint of complex structure lead to serious thermal mechanical reliability problems in TSV,among which Cu protrusion is the most common failure mode.Cu protrusion will affect the operation of devices around TSV,even break the Back-end-of-line(BEOL)layer above TSV,damage the insulation layer and interconnection line.The research of Cu protrusion has always been the focus and difficulty of thermal mechanical reliability research in TSV.The Cu protrusion under temperature load is a dynamic process.The maximum deformation and possible mismatch risk of Cu protrusion mostly occur at the peak of thermal shock load.It is difficult to evaluate the Cu protrusion structure after thermal load.However,the current stress-strain analysis in TSV is lack of experimental characterization of dynamic process due to the lack of testing equipment,and most of the analysis methods are mainly based on simulation,supplemented by single point static measurement.The analysis error of single point static measurement is large,which can not reflect the practical process of Cu protrusion,and affects the accuracy of thermal mechanical reliability analysis of TSV.Therefore,this thesis designs,manufactures and builds a reliability detection system for TSV,which has the functions of controllable heating,accurate temperature measurement and real-time morphology measurement.Under this system,the copper protrusion phenomenon in TSV is studied dynamically,and the deformation mechanism behind the copper extrusion is analyzed.Finally,the finite element model corrected by experiments is used to optimize the thermal load in TSV manufacturing process,in order to improve the TSV's thermal mechanical reliability.Specifically,firstly,the material,structure and position of each component on the base plate are designed by finite element analysis,and the designed base plate is manufactured by MEMS technology,and assembled into a thermal analysis platform that can control and measure temperature accurately.The platform will be used for the heating and temperature measurement of TSV samples in the reliability testing system.Then,the size and distribution of the holes in the TSV samples are designed,and the flawless and smooth surface TSV samples are manufactured by microfabrication technology.Finally,a TSV reliability test platform is built to measure the change of copper b?mp in TSV with temperature load.The results show that the increase of TSV diameter and depth will increase the copper protrusion,but the copper protrusion is more sensitive to the change of depth.When the current density increases(1m A/cm~2,3m A/cm~2,6m A/cm~2),but the copper protrusion of TSV decreases in turn.In addition,this thesis analyzes the deformation mechanism of TSV at elevated temperature.At low temperature(room temperature?130?),recovery and elastic deformation mainly occurs in TSV;at medi?m temperature(130?230?),the thermal stress exceeds the yield strength of copper,irreversible plastic deformation and recrystallization occurs in TSV Cu;at high temperature(230?330?),plastic deformation and creep occur in TSV Cu under high temperature and shear stress,and creep includes grain boundary sliding and grain boundary diffusion creep.Finally,the stress exponent of Norton-Bailey in TSV model is corrected by the experimental results,and the heating rate,cooling rate and heating mode of temperature load in thermal process are optimized by corrected model.This provides a useful reference for practical fabrication process.