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Experimental and theoretical investigation of mechanical stresses in Through-Silicon-Vias (TSV)
(2007)
In the work an experimental and theoretical investigation of the influence on the wafer bending of Through-Silicon-Vias (TSV) and their processing is presented. In a first step the influence of the anisotropic material properties of silicon and the thicknesses of an oxide hard mask and a tungsten film were analyzed at room temperature and as a function of the temperature up to 500 °C. For this purpose, the wafer bow was determined experimentally. In a second step, the analysis was extended to structured wafers. Wafers with Through-Silicon-Vias were etched and coated subsequently with several films. The wafer bow at room temperature was monitored stepwise. The theoretical analysis of bow and stress was done by using the Finite-Element-Program ANSYS. Models for unstructured wafers with various films were developed and the results compared with the experimental bow. For structured wafers, a model of a single via was generated; local deformations, stresses and the stress distribution were determined. To attempt the simulation of fully structured wafers, an effective medium model was developed as first step approximation.