Dramatic Improvement in the Throughput of X-ray Topography

X-ray topography is a non-destructive imaging technique that reveals lattice defects within single-crystal materials by measuring diffraction contrast caused by crystal strain. Unlike many surface inspection methods, it directly visualizes crystallographic imperfections such as dislocations, making it especially valuable for evaluating wafers used in power electronics, optoelectronics, and other high-performance semiconductor devices.

Higher throughput is achieved through several complementary improvements. A divergent X-ray beam removes the need for extensive specimen alignment, while a high-frame-rate hybrid pixel detector collects diffraction data continuously during sample motion without dead time. A larger detector also reduces the required scanning distance, allowing complete wafer imaging in just a few minutes instead of nearly an hour for conventional approaches.

The virtual slit is a software-based method that extracts only the desired diffraction signal from the complete diffraction pattern collected by the detector. Because it is implemented computationally rather than mechanically, its size and shape can be adjusted automatically for different diffraction geometries. This enables alignment-free measurements while suppressing unwanted diffraction signals from nearby X-ray wavelengths.

Conventional X-ray topography requires careful adjustment of specimen position, orientation, and lattice curvature before imaging, often consuming tens of minutes per wafer. Alignment-free imaging uses divergent X-rays to accommodate variations in wafer orientation and curvature automatically, allowing wafers to be loaded and measured with minimal preparation. This significantly improves productivity and makes routine production inspection practical.

Basal plane dislocations are crystal defects that can evolve into stacking faults during operation of SiC power devices, reducing device performance and reliability. Measuring the density and distribution of these defects allows wafer manufacturers to evaluate material quality before device fabrication and improve manufacturing processes that minimize defect formation.

A calibration relationship can be established between diffraction image intensity and basal plane dislocation density determined by reference measurements. Once calibrated, the X-ray topography image alone can be used to estimate dislocation density across an entire wafer without chemical etching or destructive testing, providing rapid quantitative quality assessment suitable for manufacturing environments.

The hybrid pixel detector contributes through its large active area, high detection efficiency, rapid frame rate, and zero dead-time operation. These characteristics allow continuous data acquisition while the specimen moves, shorten scan distances, improve measurement speed, and capture high-quality diffraction information needed for accurate defect imaging across large semiconductor wafers.