Effects and modulation mechanism of crystal structure on residual stress of Cu films used for metallization

Abstract

Deformation cracking and delamination arising from residual stress are the main challenges for metallization in large-scale integrated circuits. Herein, an ultra-low residual stress Cu film is prepared on amorphous SiO2 by mixed power magnetron sputtering. Compared to conventional Cu films, the residual stress in the film decreases by 1,434 times. The nano multi-layer structure produces lower stress and deformation as well as better reliability. The multi-layer Ti underlayer also reduces the residual stress and promotes the low-defect growth of Cu. The lower surface roughness, smaller dislocation density, predominant grain orientations of <111> and <001>, and more substructures are beneficial to the reduction of residual stress. In addition, interlayer stress cancellation can be achieved by changing the number of <111> grains. The research on grain growth at the interface of nano multi-layer films reveals an effective means to fabricate films with low residual stress for metallization in integrated circuits.