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Ludo Frevel Crystallography Scholarship Recipient

Andrew WarrenIntroducing one of our 2010 Recipients, Andrew Warren

Each year we invite one of our scholarship recipients to participate in the ICDD Spring Meetings. This year, we are happy to welcome Andrew Warren, University of Central Florida, Orlando, Florida. Andrew received the scholarship for his research entitled, “X-ray Scattering of Nanometric Films and Interfaces.”

Andrew will be giving a short presentation during the Technical Committee Meeting on Thursday, 22 March.

Synchrotron X-ray Scattering Investigation of Thin Film Interface Kinetics
Andrew P. Warren, Kevin R. Coffey, Advanced Materials Processing and Analysis Center, University of Central Florida, 4000 Central Florida Boulevard, Orlando FL 32816
Michael F. Toney, Stanford Synchrotron Radiation Lightsource, SLAC National Accelerator Laboratory, 2575 Sand Hill Rd., Menlo Park, CA 94025
Katayun Barmak, Department of Materials Science and Engineering, Carnegie Mellon University, 5000 Forbes Avenue, Pittsburgh, PA 15213
Ivan I. Kravchenko, Center for Nanophase Materials Sciences, Oak Ridge National Laboratory, Oak Ridge, TN 37831-6496

Nanometric films of pure Cu continue to attract attention due to their widespread use as the 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 electromigration and stress induced void formation which results in eventual device failure. The use of barrier 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.

Ongoing 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. Transmission electron microscopy will be used in addition to specular and diffuse X-ray reflectivity methods to quantify the decay of the corrugated interface.

You Can Help!

The ICDD solicits funds from private and industrial sectors to support this program. If you would like to make a donation, please speak with an ICDD staff member. One hundred percent of all donations to the scholarship fund are applied to student funding, as defined by the program’s charter. Volunteer scientists annually review all proposals and ICDD administers the fund at no cost to the fund. The Ludo Frevel Scholarship Program is a registered non-profit charity and all donations are tax-deductible.

Attention! Aspiring Crystallographers!

Applications for the year 2013 awards must be received by ICDD no later than 24 October 2012.
See complete application details at: www.icdd.com/resources/awards/frevel.htm