Detecting and classifying DRAM contact defects in real time

摘要

Inspection of DRAM contact layers using a multiperspec-tive system with real-time classification can provide specific defect information immediately after wafer inspection without the need for follow-up manual review. This study showed that defects were classified with high accuracy and purity (>80%), leading to rapid root-cause analysis and the subsequent elimination of killer defects. The tool's wafer-inspection sampling rate was found to be significantly higher than that of conventional inspection systems; in one instance, wafer hold time was cut from 1 hour 25 minutes to only 25 minutes. Such fast wafer disposition reduces cycle times and accelerates the yield-enhancement learning curve. By extending the inspection methodology to DRAM gate and word-line contact layers, PowerChip Semiconductor expects to reduce the overall inspection and response time from 12 hours to 30 minutes, thereby improving productivity greatly.