Electromigration resistance-related microstructural change with rapid thermal annealing of electroplated copper films

It has been found that the electromigration resistance of the electroplated Cu film is enhanced with increasing the annealing temperature in the temperature range from 200 to 500 °C. Nitrogen is more favorable than vacuum as RTA atmosphere since nitrogen atmosphere offers lower resistivity and smoother film surface. Also the dependence of the bamboo structure on the annealing temperature and the line width of the Cu interconnect is discussed. If the line width is a quarter micron, a bamboo structure will be obtained by the RTA treatment at temperatures higher than 500 °C. On the other hand, if it is less than 0.1 μm, RTA at any temperature above 200 °C will result in the bamboo structure.