Research Of TSV Thermal Mechanical Stress And Its Effect On The Mobility

With the development of microelectronics technology, the integration of chips becomes higher and higher. At present, the three-dimensional integrated technology is considered as the first scheme to realize miniaturization, high density, multi-function. Relative to the two-dimensional integration, three-dimensional integration has many advantages, such as high integration, achieving a variety of chip integration, improving the speed, improving the performance and reducing the volume and the weight. It has attracted extensive attention of researchers. Through silicon via technology is the main method to realize three-dimensional integrated, and has become the focus of current research in the microelectronic industry. As a new technology, TSV needs further study in many aspects. This article is on the TSV thermal mechanical stress and its effect on the rate of migration, and achieved some results:(1) Model building of thermal mechanical stress of the TSV structure. We choose a common TSV structure, analyze the heat mechanical stress and build the analytical model of a single TSV stress. Then compare the analytical model and finite element simulation results to verify the accuracy of the model.(2) Analyzing the influence of the TSV radius, the thickness and material properties of oxidation layer and barrier layer on the thermal stress. With the decreasing of TSV radius, the thermal stress is reduced, and the stress in silicon substrates increases faster with the decreasing of the distance to the TSV boundary. The oxide layer can be used as a stress buffer layer, and can effectively absorb the thermal stress caused by the mismatch of coefficient of TSV conductive material and the silicon substrate. The absorption effect is more obvious with thicker oxide layer, And the young’s modulus of the oxide layer material is more small, the effect is better. The influence of barrier layer is is very small,because its thickness is thin, and its material is metal the attributes of witch is bitween copper and silicon.(3) Verifying of the multiple TSVs case. The linear superposition principle is applied to TSV thermal stress analysis, and is proved to be suitable for the stress analysis. The analytical model is also effective for the stress analysis for multiple TSV force.(4) Analyzing the effect of TSV thermal mechanical stress on the carrier mobility in the silicon substrate for single TSV case. For the 100 crystal orientation of silicon substrate, the electron mobility changes greatly, and the hole mobility change is small. For the 110 crystal orientation of silicon substrate, the electron mobility change is small, the hole mobility changes greatly. No matter what the crystal direction is, the holes and the electrons in the X axis and Y axis direction changes greater than the changein between the two axes.(5) Studieding the mobility shift of the multiple TSVs case. Based on the TSV stress analytical model and the principle of linear superposition, we discuss the mobility shift of the multiple TSVs case. Through the comparative study,we found that,whether it is two or four TSVs case, they all prove that the KOZ area is minimum with PI /4 angles.