The effect of TSV design parameters on the manufacturability of TSV interposers

TSV interposer is expected to be the driving vehicle for 2.5-D IC integration. Although a number of studies have been reported on the thermo-mechanical reliability of TSVs, it remains difficult for one to justify whether a TSV design or an interposer design is manufacturable or not because we are still lack of experimental reliability data. This investigation has provided this important experimental data, and also a series of correlation studies by finite element simulations. A 2-D analytical solution was also examined to help understanding the physics of the problem. Regarding the experimental results, wafer cracking was observed for TSV arrays with large diameters and small pitch-to-diameter ratios after annealing at 300 °C. The critical strength to wafer cracking was determined to be 388 MPa from some finite element analyses. Through analytical considerations, the influence of TSV diameter on wafer cracking was found to rely on the contributions from the dielectric layer thickness and also the barrier layer thickness. An empirical model for the design of copper-filled TSV interposers was ultimately generated based on the modification of the 2-D solution.