Thermal characterization of TSV based 3D stacked ICs

This paper studies the thermal impact and characterization of Through Silicon Vias (TSVs) in stacked three dimensional (3D) integrated circuits (ICs) through finite-element based numerical analysis. Realistic 3D stacked ICs are built using a commercial finite-element based modeling and analysis tool, COMSOL. Thermal profiles along with thermal impact of TSVs are studied for two layer and three layer stacked IC structures under practical power inputs. Experimental results show that there is a significant temperature gradient across the stacked dies for both two layer and three layer structures. The cross-layer temperature is seen to grow rapidly from two layer structures to three layer structures with the same power and TSV densities. As a result, stacking of active layers will not be scalable as the maximum temperature can quickly reach the 105 degree Centigrade limit for CMOS technology. Elevated temperatures can make thermal-sensitive reliability issues a major challenge for 3D stacked ICs. Advanced cooling, low power design, better thermal management and new architecture techniques are hence required to keep the temperature in a safe range for stacking more layers onto the chip.