Scanning X-ray microdiffraction with submicrometer white beam for strain/stress and orientation mapping in thin films

Area of Science:

• Materials Science
• Condensed Matter Physics
• Analytical Chemistry

Background:

• Polycrystalline thin films are crucial in microelectronics.
• Understanding their mechanical properties at the microscale is essential for device reliability.
• Previous methods lacked the resolution to map strain and orientation within individual grains.

Purpose of the Study:

• To detail the application of scanning X-ray microdiffraction (microSXRD) for analyzing polycrystalline thin films.
• To investigate the spatial variations in orientation and strain/stress within thin films.
• To correlate microscale findings with macroscopic material properties.

Main Methods:

• Utilized high-brilliance synchrotron sources and advanced X-ray focusing optics.
• Employed a fast, large-area two-dimensional detector for data acquisition.
• Applied white or combined white/monochromatic beams for microSXRD analysis.
• Tested thin aluminum and copper films subjected to electromigration and thermal cycling.

Main Results:

• Demonstrated submicrometer spatial resolution for orientation and strain/stress mapping.
• Observed significant variations in orientation and strain/stress both between and within individual grains.
• Characterized polycrystalline films as mechanically inhomogeneous at the granular level.
• Confirmed good agreement between microSXRD data and macroscopic texture/stress measurements when averaged.

Conclusions:

• microSXRD provides unprecedented insight into the mesoscopic mechanical behavior of polycrystalline thin films.
• The technique reveals the complex, inhomogeneous nature of these materials at the microscale.
• microSXRD is a powerful tool for understanding material degradation and failure mechanisms in thin films.