Air-gap/SiO2 liner TSVs with improved electrical performance

This paper reports fabrication and characterization of TSVs that use combined air-gap/SiO2 as the insulators. Fabrication technologies based on reactive ion etching (RIE) of benzocyclobutene (BCB) sacrificial layers have been developed to fabricate uniform and high aspect-ratio air-gaps, and air-gaps with thickness of 2 µm and aspect-ratio of 25∶1 have been successfully fabricated. The measured capacitance-voltage (C-V) and current-voltage (I–V) curves at room temperature and high temperatures show that the TSVs with air-gap/SiO2 liners have low capacitance and leakage current. Compared with the TSVs using a sole air-gap insulator, the additional SiO2 liners protects the TSV from being influenced by the residues of sacrificial materials, and the electrical performance and thermal stability are improved.