Micro-XRD investigation of fine-pitch Cu-TSV induced thermo-mechanical stress in high-density 3D-LSI

3D-LSI stack containing diametrically highly-scaled through-silicon-vias (TSVs) with diameter 2μm as well as conventional 20 μm-width Cu-TSVs were carefully studied for the thermo-mechanical stress induced by Cu-TSVs via micro-X-ray diffraction using synchrotron radiation at Spring-8. It was observed that the TSV diameter has huge impact on the magnitude of resultant thermo-mechanical stress. The 20 μm-width Cu-TSV has induced more than -1500 MPa of stress in the vicinal Si, while the 2 μm-width Cu-TSV induced less than -10 MPa of compressive stress in the surrounding Si. Therefore by decreasing the TSV diameter, one can virtually eliminate the thermo-mechanical stress induced by TSV.