E-beam inspection provides a complementary approach to brightfield inspection for detection of otherwise difficult to detect physical defects. Advantages of E-beam inspection include superior resolution, the ability to classify defects using patch images and automatic filtering of prior level defects.A key limitation, however, is throughput. Therefore brightfield inspection should always be used for defection of physical defects when effective. For challenging defects, E-beam inspection data may be used as a gold standard for development of the best optical inspection conditions. For very challenging defects, it may be necessary to rely on E-beam inspection. An efficient inspection should be developed. Three examples are presented of challenging defects to illustrate the usefulness of E-beam inspection for physical defect detection.
Over the past few years numerous advancements in EUV Lithography have proven its feasibility of insertion into High Volume Manufacturing (HVM). 1, 2 A lot of progress is made in the area of pellicle development but a commercially solution with related infrastructure is currently unavailable. 3, 4 Due to current mask structure and unavailability of a pellicle, a comprehensive strategy to qualify (native defects) and monitor (adder defects) defectivity on mask and wafer is required for implementing EUV Lithography in High Volume Manufacturing.In this work, we assess mutltiple strategies for mask and wafer defect inspection including a two-fold solution to leverage resolution of e-beam inspection along with throughput of optical inspection are evaluated. Defect capture rates for inspections based on full-die, critical areas based on priority and hotspots based on design and prior inspection data are evaluated. Each strategy has merits and de-merits, particularly related to throughput, effective die coverage and computational overhead. A production ready EUV Exposure tool was utilized to perform exposures at the IBM EUV Center of Excellence in Albany, NY for EUV Lithography Development along with a fully automated line of EUV Mask Infrastructure tools. We will present strategies considered in this study and discuss respective results. The results from the study indicate very low transfer rate of defect detection events from optical mask inspection. They also suggest a hybrid strategy of utilizing both optical and e-beam inspection can provide a comprehensive defect detection which can be employed in High Volume Manufacturing.
We report an optical inspection guided e-beam inspection method for inline monitoring and/or process change validation. We illustrate its advantage through the case of detection of buried voids/unlanding vias, which are identified as yield-limiting defects to cause electrical connectivity failures. We inspected a back end of line (BEOL) wafer after the copper electro plating and chemical mechanical planarization (CMP) process with bright field inspection (BFI) and employed EBI to inspect full wafer with guidance of BFI klarf file. The dark voltage contrast defects were detected and confirmed as buried voids by transmission electron microscopy (TEM).
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