| AVS 59th Annual International Symposium and Exhibition | |
| Electronic Materials and Processing | Tuesday Sessions |
| Session EM-TuA |
| Session: | Materials and Processes for Advanced Interconnects |
| Presenter: | A.P. Warren, University of Central Florida |
| Authors: | A.P. Warren, University of Central Florida M.F. Toney, Stanford Synchrotron Radiation Lightsource K. Barmak, Carnegie Mellon University I.I. Kravchenko, Oak Ridge National Laboratory K.R. Coffey, University of Central Florida |
| Correspondent: | Click to Email |
Nanometric films of pure Cu continue to attract attention due to their widespread use as interconnect material in the semiconductor community. Among the various engineering and scientific challenges posed by the continued use of Cu is its high surface mobility, which is well known to result in both elecromigration and stress induced void formation in interconnects. The use of barrier/adhesion layers greatly improves the reliability of Cu interconnects. Nonetheless, the diffusion of Cu along the Cu/barrier interface is not well understood. Addressing the thermal stability and morphological evolution of Cu/barrier interfaces with the intent of quantifying interfacial diffusivities is the ultimate goal of this research.
Synchrotron x-ray scattering was used to study the evolution of interface roughness with annealing for a series of Cu thin films. The films were encapsulated in SiO2 or Ta / SiO2 and prepared by sputter deposition. Specular x-ray reflectivity was used to determine the root mean square roughness for both the upper and the lower Cu / SiO2 (or Cu / Ta ) interfaces. The lateral roughness was studied by diffuse x-ray reflectivity. Annealing the films at 600°C resulted in a smoothing of only the upper interface for the Cu / SiO2 samples, while the lower Cu / SiO2 interfaces and both interfaces for the Ta encapsulated films did not evolve significantly. As a function of roughness wavelength, the upper Cu / SiO2 interfaces exhibited a roughness decay with annealing that was only 12.5% of that expected for classical capillarity driven smoothening of a free surface.
Continued work is focusing on further quantifying the interface kinetics for Cu/barrier systems. Using e-beam lithography methods, we have patterned a grating onto the surface of Cu thin films. Subsequent encapsulation and annealing will be carried out to study the effects of time and temperature on the patterned interface.