Bright-field photomasks are used to print small contact holes via ArF immersion multiple patterning lithography. There
are some technical difficulties when small floating dots are to be measured by SEM tools because of a false imaging
shadow. However, a new scan technology of Multi Vision Metrology SEM<sup>TM</sup> E3630 presents a solution for this issue. The combination of new scan technology and the other MVM-SEM® functions can provide further extended applications with more accurate measurement results.
The detection and management of mask defects which are transferred onto wafer becomes more important day by day.
As the photomask patterns becomes smaller and more complicated, using Inverse Lithography Technology (ILT) and
Source Mask Optimization (SMO) with Optical Proximity Correction (OPC).
To evaluate photomask quality, the current method uses aerial imaging by optical inspection tools. This technique at
1Xnm node has a resolution limit because small defects will be difficult to detect.
We already reported the MEEF influence of high-end photomask using wide FOV SEM contour data of "E3630
MVM-SEM<sub>®</sub>" and lithography simulator "TrueMask<sub>®</sub> DS" of D2S Inc. in the prior paper .
In this paper we evaluate the correlation between our evaluation method and optical inspection tools as ongoing
Also in order to reduce the defect classification work, we can compose the 3 Dimensional (3D) information of defects
and can judge whether repairs of defects would be required.
Moreover, we confirm the possibility of wafer plane CD measurement based on the combination between E3630
MVM-SEM<sub>®</sub> and 3D lithography simulation.
To evaluate photomask quality, the current method uses spatial imaging by optical inspection tools. This technique at 1Xnm node has a resolution limit because small defects will be difficult to extract. To simulate the mask error-enhancement factor (MEEF) influence for aggressive OPC in 1Xnm node, wide FOV contour data and tone information are derived from high precision SEM images. For this purpose we have developed a new contour data extraction algorithm with sub-nanometer accuracy resulting in a wide Field of View (FOV) SEM image: (for example, more than 10um x 10um square). We evaluated MEEF influence of high-end photomask pattern using the wide FOV contour data of "E3630 MVM-SEM<sup>TM</sup>" and lithography simulator "TrueMask<sup>TM</sup> DS" of D2S, Inc. As a result, we can detect the "invisible defect" as the MEEF influence using the wide FOV contour data and lithography simulator.