Residual stress assessment of interconnects by slot milling with FIB and geometric phase analysis

Based on the combined milling-imaging capabilities of focused ion-beam equipment, a novel approach of measuring residual stress of interconnects by slot milling and geometric phase analysis is presented. This method is performed through measuring the displacement field perpendicular to the slot due to the stress release by geometric phase analysis, and then solving the residual stress along the interconnect line by finite element method. Grating fabrication, slot milling and micrographs capturing are implemented in focused ion-beam equipment. The displacement at the edge of the slot and the residual stress of a copper interconnect line were found to be in the range 2645 nm and 265467 MPa, respectively. This work provides an effective way to determine the residual stress of film lines.