3D circuit model for 3D IC reliability study

3D integrated circuit technology is an emerging technology for the near future, and has received tremendous attention in the semiconductor community. With the 3D integrated circuit, the temperature and thermo-mechanical stress in the various parts of the IC are highly dependent on the surrounding materials and their materials properties, including their thermal conductivities, thermal expansivities, Young modulus, poisson ratio etc. Also, the architectural of the 3D IC will also affect the current density, temperature and thermo-mechanical stress distributions in the IC. In view of the above-mentioned, the electrical-thermal-mechanical modeling of integrated circuit can no longer be done with a simple 2D model. The distributions of the current density, temperature and stress are important in determining the reliability of an IC. In this work, we demonstrate a method of converting 2D circuit layout into a 3D model. Simulations under real circuit operating condition are carried out using both Cadence (a circuit simulator) and ANSYS (finite element tool). Limiting our study to the electromigration failure, we compute the current density, temperature and stress distributions of the interconnect layers by considering the heat transfer and Joule heating, and the “weak spot” for electromigration is identified. Layout design can be modified based on the simulation results so as to enhance the 3D circuit interconnect reliability.