ToF-SIMS imaging of Cl at Cu grain boundaries in interconnects for microelectronics

The resistivity of copper interconnect metallization can be influenced by low levels of contaminant (Cl, S, etc.) resulting from the electrochemical deposition process. ToF-SIMS imaging was used to investigate the distribution of contamination in Cu grains. ToF-SIMS images of full sheet Cu samples were compared with images of Cu lines in patterned test structures. An ION-TOF ToF-SIMS V instrument was used to acquire the images, and the results using Ga and Bi sources are compared. Cs sputtering was used to remove the surface oxide layer and to enhance the emission of Cl− ions. Enhanced Cl− emission is seen at the grain boundaries in full sheet samples and differences in Cl− emission are observed for Cu lines of different widths.