brightfield inspection

Brightfield inspection illuminates the wafer with reflected light and detects defects by analyzing changes in the reflected signal from the patterned surface. **Principle**: Light directed onto wafer surface at normal or near-normal incidence. Reflected light collected by imaging optics. Defects alter reflected intensity compared to neighboring die patterns. **Detection**: Die-to-die comparison identifies intensity differences that exceed threshold. Differences classified as potential defects. **Light source**: Broadband (lamp) or laser illumination. UV wavelengths (193nm, 266nm) provide higher resolution for smaller defect detection. **Sensitivity**: Detects pattern defects (bridging, breaks, missing features) and large particles effectively. Moderate sensitivity to small particles compared to darkfield. **Throughput**: High throughput for production monitoring. Full wafer scan in minutes. **Darkfield comparison**: Brightfield detects pattern variations better. Darkfield (uses scattered light) detects small particles better. Complementary techniques. **Pixel size**: Optical resolution and pixel size determine minimum detectable defect size. Smaller pixels = higher sensitivity but slower throughput. **Applications**: After-develop inspection (ADI), after-etch inspection (AEI), post-CMP inspection, incoming wafer inspection. **Multi-mode**: Modern inspection tools combine brightfield and darkfield channels for comprehensive defect detection. **Nuisance defects**: Non-critical signal variations can trigger false detections. Recipe optimization minimizes nuisance rate while maintaining sensitivity. **Vendors**: KLA 29xx and 39xx series dominate brightfield inspection market.