In recent years, the number of manufacturing processes is increasing in pursuit of device pattern miniaturization. Complicated processes such as SAQP have been introduced, increasing the number of control parameters. Nevertheless, the demand for production yield enhancement is as high as ever. To detect CD changes, fixed-point measurement by using CD-SEM or scatterometry tools is typically performed, but these time-consuming measurement methods are not suitable for high-density, across-a-wafer measurement or for detecting CD anomalies that randomly occur. To address these issues, we have developed a technology that enables high-precision CD measurement of more than 100,000 points per wafer within a few minutes. It enables monitoring various CD defects in various processes such as holes and L/S patterns after photolithography, L/S patterns after SAQP/SADP, and fine hole diameters after etching. It can also measure CD imbalances after SAQP processes. In addition, it enables precisely obtaining intra-shot CD distribution based on the distribution over the entire surface of a wafer. We evaluated this technology using actual device wafers. CD imbalances of SAQP on DRAM process wafers were measured, within a few minutes across a wafer, at an accuracy of |X|+3σ<0.5 nm. CD changes at the outermost area of the wafer were captured by CD measurement of 27 nm hole patterns on a DRAM process wafer. Random CD defects were captured by CD measurement of 38 nm hole patterns on a DRAM process wafer. These defects affect device yield but were not detectable by using conventional inspection tools.
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