Crystal-plasticity based thermo-mechanical modeling of Al-components in integrated circuits

Growing demands on performance and durability of integrated circuits (ICs) require an understanding of possible failure mechanisms. One main cause for damage of ICs arises from thermo-mechanical loads of the involved materials as a result of current pulses. The mismatch in thermal expansion leads to stresses which cause crack initiation and, consequently, short circuits and the loss of functionality of the assembly. This study presents a series of numerical simulations using a three dimensional model assembly considering aluminum conductors sputtered on a silicon substrate, surrounded by an interlayer dielectric and covered by an aluminum metallization plate with passivation layer. Different conductor path geometries are investigated. The model assembly is loaded by a cyclic heat flow. The thermo-mechanical problem is solved utilizing the Abaqus/Standard solver in combination with a user-defined material routine which takes into account the microstructure and the grain orientation of the aluminum, heat flow, thermal expansion and temperature dependent material behavior. The development of stresses and strains within the interlayer dielectric and within the different conductor path geometries is investigated and compared with experimental results. Observations like surface roughening and crack initiation can be predicted qualitatively correct.