Air-Gap Through-Silicon Vias

This letter reports for the first time the fabrication and characterization of through-silicon vias (TSVs) using air-gap insulators to enable high-performance 3-D integration. To address the challenge in fabricating extremely high-aspect-ratio air gaps, a CMOS-compatible sacrificial technology based on pyrolysis of poly (propylene carbonate) has been developed, upon which air-gap TSVs have been successfully achieved. The measured capacitance density and leakage current density of air-gap TSVs are 1.22 nF/cm² and 10 nA/cm², respectively, about one order and two orders lower in magnitude than TSVs using SiO₂ insulators.