Thermal Reliability Tests of Air-Gap TSVs With Combined Air-SiO2Liners

Abstract

Using air gaps instead of conventional SiO2 liners as the isolators of through-silicon-vias (TSVs) has the potential for reducing thermal stresses and improving the thermomechanical reliability. This paper reports the thermal test results of newly developed air-gap TSVs with combined air-SiO2 insulators. Fabrication methods based on polymer sacrificial technology are reported. Thermal shock tests between −65 °C and +150 °C are performed, and the results show that the air-SiO2 liner TSVs are reliable over thermal shock with slight improvement in depletion capacitance and capacitance hysteresis. Chip curvatures caused by thermal expansion at high temperatures are measured, and it is found that the air gaps are able to mitigate plastic deformation of Cu plugs at high temperatures. These results indicate that the combined air-SiO2 insulators improve the electrical performance and the thermal stability of air-gap TSVs by isolating the organic residues originated from the sacrificial polymers, and the air-SiO2 liner TSVs have good structural integrity at high temperatures.