Thermal Stress Comparison of Annular-Trench-Isolated (ATI) TSV with Cu and Solder Core

Abstract

In order to reduce the thermal stress in the Si substrate, we proposed a novel Through Silicon Via (TSV) structure as annular-trench-isolated (ATI) TSV. The origin of thermal stress is the mismatch in the Coefficient of Thermal Expansion (CTE) of different materials. Therefore, the core material affects the thermal behavior of ATI TSV. In this paper, we continued the study by investigating the thermal stress of ATI TSV with different core materials as Cu and Solder. A numerical model of ATI TSV was established based on the fabricated samples with different core material. The thermal stress with different metal core materials was simulated and analyzed by varying the temperature from 25 °C to 125 °C and -55 °C. The simulation results showed a similar stress distribution for ATI TSVs with two core materials. And the thermal stress variation profiles near the device area were also analyzed. Although the ATI TSV with Solder core showed lower stress in the core area, and higher stress in the Si ring layer, the stress outside Si ring is at the same level for ATI TSV with two core materials. The Si ring with high Young's modulus and low CTE value blocked the effect of the different core material of ATI TSV on thermal stress inside the Si ring and maintained the stress in Si substrate at the same level.