Improving the barrier ability of Ti in Cu through-silicon vias through vacuum annealing

Abstract

Suppressing leak current and blocking Cu diffusion into active Si from Cu through-silicon vias (TSVs) are important requirements for enhancing three-dimensional (3D) LSI performance and reliability. We have proposed and confirmed a cost effective means of enhancing the barrier property of sputtered Ti in high-aspect-ratio Cu-TSVs by simple vacuum annealing at 400 °C for 20 min. The self-formed amorphous TiSi2 at the interface between dielectric SiO2 (along the TSV side-wall) and barrier Ti layer is found to play a positive role in improving the leak current characteristics. As-formed TiSix was partially converted into TiO2 and SiO2 during the vacuum annealing above 200 °C, and nearly vanished after annealing at 400 °C. The immense importance of 400 °C vacuum-annealing is not only in terms of the improvement in the barrier characteristics of the Ti layer, but also it is being a prerequisite for preventing Cu popup in 3D-LSI. Both the X-ray photoelectron spectroscopy (XPS) and current–voltage (I–V) data clearly reveal that this simple vacuum annealing of Cu-TSVs at 400 °C has tremendous potential for implementation in cost-effective via-last 3D integration.