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Effects of Electron Beam on Photo Resist Shrinkage and Critical Dimension in SEM Measurement

Scanning electron microscope (SEM) measurement is the dominant method to obtain critical dimension (CD) in lithography. In SEM measurement, electron beam exposed on photo resist (PR) will affect PR physical-chemically and cause PR shrinkage inevitably. This phenomenon is well-known in lithography and also studied by many researchers. In this paper, we reviewed previous research results and investigated the PR shrinkage effects on CD measurement of 193nm immersion photo resist in 14nm node. With patterns sizing down, it is important to choose an appropriate voltage, current and frame to avoid large amount shrinkage in the measurement. A 30nm size CD shrinks more than 10% until getting saturation. Different patterns and CD sizes possess different through pitch shrinkage performance, which means PR shrinkage will also impact OPC model setup.