Cu Microstructure Impact on Reliability

Cu was believed to be more resistant than Al with regard to stress-migration and electro-migration reliability. This claim is mainly based on slower diffusivity and higher mechanical strength of Cu than Al. However, Cu is highly anisotropic and easily forms twins. This leads to new reliability issues originated from microstructure and crystallographic texture. In addition, adoption of dual-damascene process for Cu interconnects further complicates the issue, because of geometrical confinement and its effects on the microstructure and the texture. Tutorial covers (1) the texture of sputtered and electroplated Cu, (2) the development of the texture and the microstructure during annealing at elevated temperature as well as during self-annealing at room temperature, (3) orientation-dependent stress distribution due to mechanical anisotropy, (4) the effects of geometrical constraint in the damascene structure, and (5) the effects of the above items on the interconnect reliability with various dielectric materials.

Junichi Koike

Junichi Koike is a professor in the Department of Materials Science, Tohoku University, Japan. He received M.S. in Metallurgy from Tokyo Institute of Technology in 1985 and Ph.D. in Materials Science from Northwestern University in 1989. He was a director's postdoc between 1989 and 1991 at the Center for Materials Science, Los Alamos National Laboratory, and an assistant professor at Oregon State University. He joined Tohoku University in 1994 and became a full professor in 2004. He has published more than 100 papers, and presented invited papers on the reliability of metallization at various conferences such as MRS, Stress Workshop and ADMETA. His research interests include microstructure, stress migration, interface reaction, interface adhesion of interconnect materials.