Texture and stress analysis of 120 nm copper interconnects

A scanning transmission electron microscope diffraction technique was used to determine the local orientation of copper grains in 120 nm copper interconnect (CI) lines. These grains exhibit a <1 1 0> normal orientation while the <1¯12> and the <11¯1> type orientations are present along the length and width of the CI line, respectively. Stresses, as high as 625 MPa, are present at the copper/diffusion barrier triple junctions that in conjunction with large stress gradients may induce stress-induced void formation upon thermal cycling.