Scatterometry is a well-established,fast and precise optical metrology method used for the characterization of sub-lambda periodic features.The Fourier scatterometry method,by analyzing the Fourier plane,makes it poss...Scatterometry is a well-established,fast and precise optical metrology method used for the characterization of sub-lambda periodic features.The Fourier scatterometry method,by analyzing the Fourier plane,makes it possible to collect the angle-resolved diffraction spectrum without any mechanical scanning.To improve the depth sensitivity of this method,we combine it with white light interferometry.We show the exemplary application of the method on a silicon line grating.To characterize the sub-lambda features of the grating structures,we apply a model-based reconstruction approach by comparing simulated and measured spectra.All simulations are based on the rigorous coupled-wave analysis method.展开更多
Optical scatterometry is one of the most important metrology techniques for process monitoring in high-volume semiconductor manufacturing.By comparing measured signatures to modelled ones,scatterometry indirectly retr...Optical scatterometry is one of the most important metrology techniques for process monitoring in high-volume semiconductor manufacturing.By comparing measured signatures to modelled ones,scatterometry indirectly retrieves the dimensions of nanostructures and,hence,solves an inverse problem.However,the increasing design complexity of modern semiconductor devices makes modelling of the structures ever more difficult and requires a multitude of parameters.Such large parameter spaces typically cause ambiguities in the reconstruction process,thereby complicating the solution of the inherently ill-posed inverse problem further.An effective means of regularisation consists of systematically maximising the information content provided by the optical sensor.With this in mind,we combined the classical techniques of white-light interferometry,Mueller polarimetry,and Fourier scatterometry into one apparatus,allowing for the acquisition of fully angle-and wavelength-resolved Mueller matrices.The large amount of uncorrelated measurement data improve the robustness of the reconstruction in the case of complex multi-parameter problems by increasing the overall sensitivity and reducing cross-correlations.In this study,we discuss the sensor concept and introduce the measurement strategy,calibration routine,and numerical post-processing steps.We verify the practical feasibility of our method by reconstructing the profile parameters of a sub-wavelength silicon line grating.All necessary simulations are based on the rigorous coupledwave analysis method.Additional measurements performed using a scanning electron microscope and an atomic force microscope confirm the accuracy of the reconstruction results,and hence,the real-world applicability of the proposed sensor concept.展开更多
基金We are thankful for the technical support given by Thomas Schoder.This work was supported by the German DFG-funded priority program(SPP1327)on‘Optically generated sub-100 nm structures for technical and bio-medical applications’within the subproject‘Development of a functional sub-100 nm 3D two-photon polymerization technique and optical characterization methods’and the DFG project‘Inverse-source and inverse-diffraction problems in photonics(OS111/32-1).’。
文摘Scatterometry is a well-established,fast and precise optical metrology method used for the characterization of sub-lambda periodic features.The Fourier scatterometry method,by analyzing the Fourier plane,makes it possible to collect the angle-resolved diffraction spectrum without any mechanical scanning.To improve the depth sensitivity of this method,we combine it with white light interferometry.We show the exemplary application of the method on a silicon line grating.To characterize the sub-lambda features of the grating structures,we apply a model-based reconstruction approach by comparing simulated and measured spectra.All simulations are based on the rigorous coupled-wave analysis method.
基金supported by the Deutsche Forschungsgemeinschaft(DFG,German Research Foundation)under grant number Os 111/50-1.
文摘Optical scatterometry is one of the most important metrology techniques for process monitoring in high-volume semiconductor manufacturing.By comparing measured signatures to modelled ones,scatterometry indirectly retrieves the dimensions of nanostructures and,hence,solves an inverse problem.However,the increasing design complexity of modern semiconductor devices makes modelling of the structures ever more difficult and requires a multitude of parameters.Such large parameter spaces typically cause ambiguities in the reconstruction process,thereby complicating the solution of the inherently ill-posed inverse problem further.An effective means of regularisation consists of systematically maximising the information content provided by the optical sensor.With this in mind,we combined the classical techniques of white-light interferometry,Mueller polarimetry,and Fourier scatterometry into one apparatus,allowing for the acquisition of fully angle-and wavelength-resolved Mueller matrices.The large amount of uncorrelated measurement data improve the robustness of the reconstruction in the case of complex multi-parameter problems by increasing the overall sensitivity and reducing cross-correlations.In this study,we discuss the sensor concept and introduce the measurement strategy,calibration routine,and numerical post-processing steps.We verify the practical feasibility of our method by reconstructing the profile parameters of a sub-wavelength silicon line grating.All necessary simulations are based on the rigorous coupledwave analysis method.Additional measurements performed using a scanning electron microscope and an atomic force microscope confirm the accuracy of the reconstruction results,and hence,the real-world applicability of the proposed sensor concept.
