Metrology & Inspection Equipment
Defect Inspection
Brightfield, darkfield, and e-beam inspection for finding killer defects
Optical Inspection
Optical Inspection
Defect inspection finds particles, pattern defects, and process anomalies that could kill dies:
- Brightfield inspection: Illuminates the wafer and compares the image of each die to its neighbors (die-to-die comparison). Differences = potential defects. High throughput but limited by optical resolution (~30 nm sensitivity).
- Darkfield inspection: Detects light scattered by defects against a dark background. Higher sensitivity to small particles than brightfield. Used for unpatterned and patterned wafer inspection.
- E-beam inspection: Scans with a focused electron beam for ultimate resolution (<10 nm). Can detect electrical defects (voltage contrast) invisible to optical tools. Very slow — used for development and focused areas, not full-wafer production inspection.
After inspection finds defect locations, a Review SEM takes high-resolution images of individual defects for classification — determining what type of defect it is and its root cause.
Key Concept: ML for Defect Classification
Automatically classifying defects from SEM review images is a major ML application in fabs. CNNs can classify defects into dozens of categories (particle, scratch, bridging, missing pattern, etc.) faster and more consistently than human operators.
Knowledge Check
Knowledge Check
1 / 1What is the advantage of e-beam inspection over optical inspection?