In this paper, we demonstrate the efficient use of contours extracted from photomask SEM images to characterize features with respect to placement, pattern fidelity, and uniformity. Absorber defects can be automatically detected and categorized. To assess the probability of mask defect printing, we show how an extracted mask image contour can be used as input for a rigorous lithography 3D resist process simulation to quickly estimate the severity and potential printing behavior in resist of a defect through dose and focus. The presented simulation results are validated by wafer data. The results of this work could provide guidelines for the mask making process and mask inspection.
KEYWORDS: Calibration, Data modeling, Resolution enhancement technologies, Process modeling, Scanning electron microscopy, Data acquisition, Optical lithography, Metrology, Lithography, Computer simulations
Computational lithography applications for OPC/ RET utilize models that represent the lithographic process in simulations. The quality of OPC/ RET wafer results strongly depends on the quality of the model. Hence, achieving model quality and experimental match is the goal of the model calibration process where models are calibrated to experimental data. Ideally, the model would be calibrated and validated to a data set that completely covers the entire design space and all process conditions. A promising alternative to the traditionally applied SEM-CD-based model calibration is the calibration to pattern contours directly with benefits in design space coverage, reduced metrology effort and data preparation complexity. However, contour calibration also demands a new standard operating procedure for contour specific metrology, pattern design and calibration. Goal of this work is to develop and exercise a full contour-based calibration methodology. Firstly, we discuss preconditions for a successful calibration: good quality contour input data, predictive modeling of optics, mask topography and 3D resist and additional calibrator functionality to include aspects of alignment and pattern specific measurement confidence. Secondly, we assess pattern for their calibration-suitability using a metric for pattern information density. Experiments are performed to show the applicability of the metric and the potential to calibrate to a minimal set of patterns. A model calibrated to a well selected single 2.25 μm2 contour is predicting a large set of pattern contours, 3D resist characteristics and SEM-CD focus-exposure process windows.
As EUV lithography is getting ready for deployment in high volume manufacturing, lithography engineering focus moves to efficient computational lithography tools (mask correction, verification, source-, mask- and processoptimization) providing optimal RET solutions for EUV early design exploration. Key to computational lithography success is the prediction ability of the underlying lithography process simulation model. Topographic mask effects prediction is one of the major challenges with significant impact on both simulation quality of results and turn around time. In this paper, we apply a fast modeling approach to EUV light diffraction on topographic masks, which is based on fully rigorous topographic mask simulations. It is demonstrating performance benefits of several orders of magnitude while maintaining the accuracy requirements for productive cases. We explore its applicability to medium sized computational lithography tasks. The accurate mask solver results will be complemented with imaging and 3D resist simulations using the rigorous lithography simulator S-Litho by Synopsys.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
PERSONAL Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.