Morphology and microstructure control of sputter-deposited copper films by addition of Cr

Pure Cu and Cu with 1 at.% and 2.6 at.% Cr films were sputtered on (100) single crystal Si wafers in the presence of native suboxide (SiOx). Samples were vacuum-annealed to investigate effects of Cr on the microstructural characteristics of Cu films. Cr refines the columnar structure and decreases the surface roughness of Cu films. Upon annealing, most films undergo the process of crystallite growth and coalescence. Cross-sectional images show that Cr stabilizes the columnar structure and inhibits the agglomeration of annealed Cu(Cr) films at high temperatures. The fine grains of Cu(Cr) films suggest that the extensive Cu crystallite/grain growth at 400 deg. C is effectively impeded by the presence of Cr. The noticeable grain growth occurs around 450 deg. C with Cr precipitates in Cu(Cr) films. After annealing, the final resistivity of the annealed Cu(Cr) film is approached to that of the Cu film. Adding Cr to films has obtained significant changes in morphology and microstructure of Cu films before and after annealing.