Thermal and mechanical reliability of thermal through-silicon vias in three-dimensional integrated circuits

Abstract

This research aims to explore the influences of shapes, structures, and arrangements of thermal through-silicon vias (TTSVs) on the thermal and mechanical reliability of a three-dimensional integrated circuit (3D IC). For this purpose, a finite element model coupling the temperature and stress fields in a representative 3D IC with three layers of dies was established to allow numerical simulation of thermal and mechanical reliability caused by the above three factors. The research results show that firstly, rectangular TTSVs have better heat transfer performance than commonly used circular TTSVs of the same area. However, the former is more likely to cause problems pertaining to mechanical reliability in dies. Secondly, compared with the in-line mode of arrangement, the staggered arrangement mode can enable the more compact and uniform arrangement of TTSVs and improve the capacity for heat conduction between adjacent TTSVs, thus reducing the hotspot temperature: meanwhile, the thermal stress rises giving rise to a contradiction between the conventional means of enhancing the heat transfer performance of TTSVs and the resulting increase of thermal stress. Finally, by adding air gaps to TTSVs, the thermal stress around TTSVs can be reduced, while the heat transfer performance also decreases. If air gaps are replaced with carbon nanotubes (CNTs), such a problem can be alleviated. The analysis methods and research results can provide an important reference for the trade-off between thermal reliability and mechanical reliability in 3D ICs in engineering practice.