CD-SEM Contour Extraction for Complex Features Measurement

Scanning Electron Microscope (SEM) metrology is the key and useful method for the critical dimension (CD) after developing inspection (ADI) and after etching inspection (AEI) measurement of regular and periodic features, but it is challenged when it comes to multi-point measurement and pattern shift inspection of complex features. In this work, a SEM contour based measurement strategy for complex features is proposed. A robust and reliable multi-step contour extraction and alignment method is studied to extract ADI and AEI SEM image contours and contours are converted into layout format. The solution is verified on complex patterns measurement with high accuracy and precision. The method also demonstrates the capability of lithography to etching bias measurement and contour to target layer edge placement error (EPE) measurement, which is effective for asymmetric phenomenon inspection. With GDS environment, more contour and design information that is useful is extracted to analysis lithography and etching steps patterns performance and the transfer behavior of complex structures.