Thermal and Electrical Reliability Tests of Air-Gap Through-Silicon Vias

Through-silicon vias (TSVs) with air gaps as the isolators have been developed to reduce the TSV capacitance and to solve the reliability problems associated with thermomechanical stresses. This paper reports the reliability assessment of the air-gap TSVs by measuring the C-V, I-V, and resistance of the TSVs in terms of thermal and electrical stresses with a focus on thermal shock, temperature variations, and voltage ramps. Thermal shock tests are performed to evaluate the insulation capability and the thermomechanical stability of the air gaps. Temperature variations are implemented to investigate the influences of high temperatures on the electrical characteristics of the air-gap TSVs. Voltage ramp tests are carried out, and the time-dependent dielectric breakdown is obtained to evaluate the integrity of the air gaps and the intrinsic barrier capability. The preliminary results show that the air-gap TSVs have good thermal stability, excellent dielectric property, and satisfactory structure and barrier stability.