Influence of e-beam aperture angle on CD-SEM measurements for high-aspect ratio structure

The influence of e-beam aperture angle on CD-SEM measurements for a high aspect ratio (HAR) structure was investigated. The Monte-Carlo simulator JMONSEL was used to evaluate the measurement sensitivity to the variation in the bottom CD. The aperture angle of the primary electron greatly influences the measurement accuracy of the bottom CD in the HAR structure. Then, we utilized a technique for energy-angular selective detection to the Monte-Carlo simulation results and found that the measurement sensitivity for the large aperture angle was improved. In addition, the experimental results were qualitatively consistent with the results of the Monte-Carlo simulation. These results indicate that the detection is effective for the bottom CD measurement of a HAR structure.