12 April 2013 Role of 3D photo-resist simulation for advanced technology nodes
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3D Resist Models are gaining significant interest for advanced technology node development. Correct prediction of resist profiles, resist top-loss and top-rounding are acquiring higher importance in ORC hotspot verification due to impact on etch resistance and post etch results. We would like to highlight the specific calibration procedure to calibrate a rigorous 3D model. Special focus is on the importance of high quality metrology data for both a successful calibration and for allowing a reduction of the number of data points used for calibration [1]. In a productive application the calibration could be performed using a subset of 20 features measured through dose and focus and model validation was done with 500 features through dose and focus. This data reduction minimized the actual calibration effort of the 3D resist model and enabled calibration run times of less than one hour. The successful validation with the complete data set showed that the data reduction did not cause over- fitting of the model. The model is applied and verified at hotspots showing defects such as bottom bridging or top loss that would not be visible in a 2D resist model. The model performance is also evaluated with a conventional CD error metric where CD at Bottom of simulation and measurement are compared. We could achieve excellent results for both metrics using SEM CD, SEM images, AFM measurements and wafer cross sections. Additional modeling criterion is resist model portability. A prerequisite is the separability of resist model and optical model, i.e. the resist model shall characterize the resist only and should not lump characteristics from the optical model. This is a requirement to port the resist model to different optical setups such as another illumination source without the need of re-calibration. Resist model portability is shown by validation and application of the model to a second process with significantly different optical settings. The resist model can predict hot spots and CDs for the second litho process with the same quality as for the process it was calibrated to.
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Aravind Narayana Samy, Aravind Narayana Samy, Rolf Seltmann, Rolf Seltmann, Frank Kahlenberg, Frank Kahlenberg, Jessy Schramm, Jessy Schramm, Bernd Küchler, Bernd Küchler, Ulrich Klostermann, Ulrich Klostermann, "Role of 3D photo-resist simulation for advanced technology nodes", Proc. SPIE 8683, Optical Microlithography XXVI, 86831E (12 April 2013); doi: 10.1117/12.2011427; https://doi.org/10.1117/12.2011427

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