Plane-wave X-ray topography and its application at SPring-8

Area of Science:

• Materials Science
• Solid State Physics
• Crystallography

Background:

• High-resolution characterization of silicon wafer quality is crucial for semiconductor device fabrication.
• Synchrotron-based X-ray topography offers non-destructive methods for defect analysis in crystalline materials.

Purpose of the Study:

• To characterize lattice defects in Float-Zone (FZ) and Czochralski (CZ) silicon wafers using plane-wave X-ray topography.
• To evaluate the performance of a long beamline at SPring-8 for high-resolution X-ray diffraction imaging.
• To investigate the influence of experimental parameters, such as sample-photoplate distance, on defect imaging.

Main Methods:

• Utilized plane-wave X-ray topography at the SPring-8 synchrotron facility (BL20B2).
• Employed 30 keV high-energy X-rays with a narrow angular divergence (approx. 0.01 arcsec) achieved using a single collimator crystal.
• Performed characterization in transmission geometry (Laue case) for both FZ-Si and CZ-Si wafers.

Main Results:

• Observed distinct oscillatory profiles in the rocking curves of FZ-Si crystals, indicative of high crystal perfection.
• Acquired detailed plane-wave topographic images of various lattice defects in CZ-Si, including dislocations, growth striations, and grown-in microdefects.
• Demonstrated the impact of sample-photoplate distance on the visibility and resolution of defect images.

Conclusions:

• Plane-wave X-ray topography at SPring-8 is effective for high-sensitivity defect analysis in silicon wafers.
• The experimental setup allows for clear visualization of microstructural features in both high-purity and commercially grown silicon.
• Further studies can optimize imaging parameters for advanced semiconductor materials characterization.