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Candela® 8520 Surface Defect Inspection System

Unpatented Wafer Inspection Solution for Power Device Applications

The Candela® 8520 2nd generation integrated surface and photoluminescence inspection system is designed for advanced characterization of substrate and epitaxial defects for the power device market and related applications. Implementation of automated wafer inspection with statistical process control (SPC) methodology can significantly cut yield loss due to epi defects, minimize metal-organic chemical vapor deposition (MOCVD) reactor process excursions, and increase MOCVD reactor uptime. The Candela 8520 is the successor to the Candela CS920, which was the first of its kind to integrate macro/micro detection for surface and crystal defects in a unified inspection platform. It employs proprietary optical technology to simultaneously measure scatter intensity at varying angles of incidence, topographic variations, surface reflectance, phase shift and photoluminescence for automatic detection and classification of a broad range of defects of interest (DOI).
Automated defect inspection for LED materials, enabling enhanced quality control of substrates, fast time-to-root cause determination, and improved MOCVD process control

A single-tool solution that combines multiple optical inspection techniques in a single scan for maximum efficiency in automated defect detection and classification
High sensitivity to yield-impacting defects across multiple compound semiconductor substrates

The 8520 system’s multiple detection channels enable understanding of process related issues and identification of yield-impacting defects. The inspection method achieves full-surface coverage in minutes with high-resolution images and wafer maps with automatically classified defects.

Example defect images

Comparison to scatterometry systems

The Candela 8520 inspection system provides the option to save the raw data collected from multiple detectors. Defect signatures seen by different detectors can vary by defect type, which can help process engineers to accurately classify defects. The Candela 8520 system can detect and classify both macro and micro defects. Micro defect classification is done based on comparison of the optical signature from the normal- and oblique-incidence illumination. Macro defect classification uses optical signatures and defect attributes. MOCVD processes produce a variety of defects when epi is grown on different substrate materials (SiC, GaN, etc.). The Candela 8520 system is sensitive to common yield-impacting defects including micro-pits, cracks, hexagonal bumps, showerhead droplets, crescents, scratches and other topographic defects. Accurate classification is critical to driving key corrective actions for process control. The image gallery (Fig. 4) shows examples of different types of detected defects. The Candela 8520 system’s high sensitivity, throughput and versatility provide a cost-effective solution suitable for both process development and high volume manufacturing process control.