Investigation of grain growth and impurity diffusion in highly conductive copper interconnect films obtained by pulsed laser scanning annealing

Abstract

The resistivity of the interconnection is a crucial restriction to its performance. In this paper, pulsed laser scanning annealing (PLSA) is proposed as a novel annealing method to reduce the resistance of copper interconnects. The impacts of pulsed laser irradiation on copper interconnect resistance are studied in terms of grain growth and impurity diffusion by experiments and simulations. The temperature gradient generated by laser induces the in-plane and in-depth columnar grain growth, with maximum grain sizes of 17.4 μm and 21.6 μm, respectively. The impurity diffusion is stimulated when the single pulse energy exceeds a threshold at the same laser power density, verified by experiments and calculations. The amount of total escaped impurities and Cl is 83.2 % and 89.2 % higher in PLSA than in thermal annealing, respectively. As a result, copper films with conductivity up to 98.6 % international annealed copper standard were obtained, which makes PLSA a potential application for future advanced interconnects.