Abstract: Optical inspection cannot resolve critical defects at advanced nodes and cannot detect subsurface defects. Especially at 7nm and below, many yield and reliability killer defects are the result of interactions between lithography, etch, and fill. These defects often will have part per billion (PPB) level fail rates. Conventional eBeam tools lack the throughput to measure PPB level fail rates. A solution is required with several orders of magnitude higher throughput than conventional e-Beam tools without sacrificing the ability to measure sub20nm feature sizes. PDF has developed the DirectScan technology to scan billions of patterns of interest per hour. This DirectScan technology is an eBeam inspection technology that is designed and optimized to scan random product layout patterns. Using sophisticated product layout analyses, scanning recipes are created to drive the tool time of DirectScan technology to focus upon measuring relevant, voltage contrast observable layout shapes. PDF has deployed this tool on nodes ranging from 28nm down to 4nm products for at layer full wafer inspection within 24 hours or proportional sampling within 2 and 4 hour queue time limits. The results have enabled quantifying PPB fail rates per layout pattern in product die, identifying wafer spatial systematics associated with pattern fails, and detecting leakage currents corresponding to reliability risks.
Keywords: Design For Inspection, Voltage Contrast, Direct Scan, New Product Introduction, Process Control