Analysis of copper plasticity impact in TSV-middle and backside TSV-last fabrication processes

Copper plasticity effects in TSV middle and backside TSV last integration flows are analyzed using an advanced 3D TCAD simulator with model parameters calibrated to match experimental data. In this work, a low thermal budget TSV last integration flow is considered. In contrast to the TSV middle flow, the TSV last flow studied here exhibits insignificant TSV pumping, M1 metal thinning or M1 metal resistance increase. The difference in residual stress profiles in BEOL structure for TSV middle and TSV last processes indicates that the process sequence must be optimized in order to minimize the reliability risks. The mobility change in active silicon for the TSV last process is lower as compared to that for the TSV middle process at room temperature due to the lower temperature excursions during the TSV last integration. This study demonstrates that the TSV integration flow must be designed and selected carefully to meet specific performance and reliability requirements.