Fabricating and inspecting ultrathin silicon-on-insulator wafers

摘要

Soitec produces 200-mm SOI wafers in high-volume manufacturing that have achieved defectivity levels comparable to those of epitaxial wafers. Similar wafer quality has been attained in 300-mm manufacturing using roughly the same tool set and process configuration. New process strategies have improved layer uniformity so that products can meet IC supplier roadmap targets for the 90-nm node and below. The XUT product generation offers high uniformity (+-10 A) and is production-worthy at 200 and 300 mm. In SOI wafer fabrication, metrology is crucial to achieve low surface roughness and nanotopography levels, enabling wafer inspectability at low thresholds. Nanotopography monitoring has been demonstrated to be the appropriate technique for assessing nanouniformity levels of SOI layers. Thickness measurement accuracy on ultrathin SOI films is still in need of improvement. Meanwhile, defectivity control at low threshold levels for advanced SOI structures is very challenging. The use of UV lasers enhances defect detection and eliminates reflectivity concerns.