Akira Hamamatsu

Verification and extension of the MBL technique for photo resist pattern shape measurement

In order to achieve pattern shape measurement with CD-SEM, the Model Based Library (MBL) technique is in the process of development. In this study, several libraries which consisted by double trapezoid model placed in optimum layout, were used to measure the various layout patterns. In order to verify the accuracy of the MBL photoresist pattern shape measurement, CDAFM measurements were carried out as a reference metrology. Both results were compared to each other, and we confirmed that there is a linear correlation between them. After that, to expand the application field of the MBL technique, it was applied to end-of-line (EOL) shape measurement to show the capability. Finally, we confirmed the possibility that the MBL could be applied to more local area shape measurement like hot-spot analysis.

Improved secondary electron extraction efficiency model for accurate measurement of narrow-space patterns using model-based library matching

In order to accurately measure narrow-space patterns, we propose an improved secondary-electron extraction efficiency model for the model-based library method. In the conventional model, the same extraction efficiency is applied to all electrons, regardless of from where the electrons are emitted. This is a simplified model that assumes a uniform extraction electric-field strength. In the improved model, the extraction efficiency is calculated as a function of the pattern shape and the emission position of the electrons. The function is based on simulation results for the electric-field strength of critical-dimension scanning electron microscopy (SEM) optics. We verify the effectiveness of the improved extraction model by applying this model to measurements of actual patterns with space widths in the (20 to 30) nm range. The measurement bias of the sidewall angle (SWA) is evaluated through comparison to cross-sectional SEM measurements. We demonstrate that the average SWA bias is improved from 0.8 deg for the conventional model to 0.04 deg for the improved model.