A Novel Silicon-Air-Silicon Through-Silicon-Via Structure Realized Using Double-Side Partially Overlapping Etching

This letter presents the design and fabrication of a through-silicon-via (TSV) structure using ultra-low-resistivity-silicon (ULRS) as the central conductor and air-gap as the insulation layer. Silicon-air-silicon (SAS) TSVs are successfully fabricated using a simple and low-cost fabrication process based on a novel double-side half-annular Si etching technique. A comparative study on different overlapping areas of the double-side Si etching is carried out to guarantee the proper formation of the air-gap insulation layer and to minimize the lateral undercutting effect occurred near the openings of the air-gaps. Thanks to the good isolation nature of the air and the successful formation of the air-gaps, we have achieved a capacitance density of 0.137 nF/cm2 and a leakage current density of 3.85 nA/cm2 for a single SAS TSV, indicating superior electrical properties in terms of ultra-low parasitic capacitance and excellent insulating performance, which shows an alluring prospect in future 3-D integration strategies and applications.