Influence of crystallite size and impurity density on the grain structure evolution of electroplated copper films during thermal and laser annealing

• Published in: Thin solid films Vol. 805; p. 140514
• Main Authors: Han, Silin, Li, Chongyang, Chen, Yuhang, Wu, Yunwen, Li, Ming, Hang, Tao
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 30.09.2024
• Subjects: Copper interconnects; Grain growth; Impurity diffusion; Laser annealing; Impurity diffusion; Copper interconnects; Laser annealing; Grain growth
• ISSN: 0040-6090
• DOI: 10.1016/j.tsf.2024.140514

•More impurities reduce conductivity in annealed small crystallite (<33 nm) films.•More impurities raise conductivity in annealed large crystallite (>68 nm) films.•Laser annealing stimulates impurity diffusion more than thermal annealing.•Laser-annealed films lose more effects from impurities than thermal-annealed films. In this paper, the changes in microstructure and conductivity of the films before and after thermal and laser annealing are observed, which corresponds to various combinations of crystallite sizes and impurity densities. The results show that the impurities promote grain boundary migration at larger initial crystallite sizes, which contradicts previous reports. This is because the rate of grain growth is determined by the driving force and resistance to grain growth, the former provided by the energy of grain boundaries and the impurities outside the nanograin boundaries, and the latter by the impurities enriched within the boundaries. Additionally, laser annealing is more effective than thermal annealing in stimulating impurity diffusion, resulting in a reduced influence of impurities on grain growth.