Early detection of pattern defects on PDI wafers

As critical design rules continuously shrink to 10nm and beyond, and double patterning or multiple patterning become prevailing practice, detection of missing pattern prior to Chemical Mechanical Planarization (CMP) or the final etch level in Back End of Line (BEoL) process has always been a significant challenge. Early detection of single line and multi-line opens with a Post Develop Inspection (PDI) could help process integration significantly reduce the yield learning cycle and provide the opportunities of wafer rework in High Volume Manufacturing (HVM). Cost and time to market are incentives to develop this application. Bright Field Inspection (BFI), which was used prevailingly for pattern defect detection, has clearly shown limitations on gap defect detection. However, e-beam inspection, successfully demonstrated for PDI after carefully optimizing SEM conditions, can achieve both high defect capture rate and minimize photo resist shrinkage. A strong correlation between line bridge/protrusion defects and single/multi line openings has been demonstrated on both modulated and normal condition die.