BEoL Cracking Risks due to Manufacturing Introduced Residual Stresses

Progressive miniaturization and functional integration in the field of BEoL structures of modern CMOS components call for the use of new materials (porous or nanoparticles filled) in connection with completely new manufacturing technologies. Residual stresses generated in thin layers during several manufacturing processes can lead to delamination and cracking before and because of the stress under CPI (during lead-free reflow soldering and further chip handling, in particular). Challenges for the improvement of thermos-mechanical reliability exist from two sides: the higher thermo-mechanical loads as well as the partly lower damage and fracture resistance of those new materials and interfaces. Therefore, the question of the residual stresses and their influence on the risk of damage and fracture become an important factor. This fact also has an impact on the application of fracture mechanics analysis using simulative numerical methods as a reliable method for process and design optimization [1]. In this paper, the part of residual stresses of different layers for the formation and propagation of cracks in BEoL structures have been investigated by experiment (FIB based residual stress estimation) and simulation (XFEM delivering crack initiation and propagation).