Monte Carlo simulation of scanning electron microscope signals for lithographic metrology

Lowney, Jeremiah R.

doi:10.1002/sca.1996.4950180406

Cited by 49 publications

(35 citation statements)

References 8 publications

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“…21 The integrated cross sections for the newly implemented physics models are shown in Figure 1. A similar hybrid approach, where different theories are used to represent the various inelastic processes of the material, has also been employed in the MONSEL code 22 for secondary electron transport simulations. An alternative approach is the use of a model dielectric response function for the target material.…”

Section: Description Of Geant4-dna Physics Models For Goldmentioning

confidence: 99%

An implementation of discrete electron transport models for gold in the Geant4 simulation toolkit

Sakata

Incerti

Bordage

et al. 2016

Journal of Applied Physics

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Gold nanoparticle (GNP) boosted radiation therapy can enhance the biological effectiveness of radiation treatments by increasing the quantity of direct and indirect radiation-induced cellular damage. As the physical effects of GNP boosted radiotherapy occur across energy scales that descend down to 10 eV, Monte Carlo simulations require discrete physics models down to these very low energies in order to avoid underestimating the absorbed dose and secondary particle generation. Discrete physics models for electron transportation down to 10 eV have been implemented within the Geant4-DNA low energy extension of Geant4. Such models allow the investigation of GNP effects at the nanoscale. At low energies, the new models have better agreement with experimental data on the backscattering coefficient, and they show similar performance for transmission coefficient data as the Livermore and Penelope models already implemented in Geant4. These new models are applicable in simulations focussed towards estimating the relative biological effectiveness of radiation in GNP boosted radiotherapy applications with photon and electron radiation sources. Gold nanoparticle (GNP) boosted radiation therapy can enhance the biological effectiveness of radiation treatments by increasing the quantity of direct and indirect radiation-induced cellular damage. As the physical effects of GNP boosted radiotherapy occur across energy scales that descend down to 10 eV, Monte Carlo simulations require discrete physics models down to these very low energies in order to avoid underestimating the absorbed dose and secondary particle generation. Discrete physics models for electron transportation down to 10 eV have been implemented within the Geant4-DNA low energy extension of Geant4. Such models allow the investigation of GNP effects at the nanoscale. At low energies, the new models have better agreement with experimental data on the backscattering coefficient, and they show similar performance for transmission coefficient data as the Livermore and Penelope models already implemented in Geant4. These new models are applicable in simulations focussed towards estimating the relative biological effectiveness of radiation in GNP boosted radiotherapy applications with photon and electron radiation sources. Published by AIP Publishing. [http://dx

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Section: Description Of Geant4-dna Physics Models For Goldmentioning

confidence: 99%

An implementation of discrete electron transport models for gold in the Geant4 simulation toolkit

Sakata

Incerti

Bordage

et al. 2016

Journal of Applied Physics

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“…Several offline methods have been developed to establish a correlation between secondary and/or backscattered electron (SE, BSE) signal and actual feature shape 7,8 . Most of them are based on Monte-Carlo modeling of beam interaction with the sample.…”

Section: Description Of the Methodsmentioning

confidence: 99%

CD-SEM-based critical shape metrology of integrated circuits

Gorelikov¹,

Sullivan²

2004

Metrology, Inspection, and Process Control for Microlithography XVIII

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With critical dimensions (CD) of integrated circuits shrinking to tens of nanometers, accurate metrology of threedimensional feature shapes at different stages of the lithographic process becomes crucial to circuit performance. We propose Critical Shape Metrology (CSM), a CD-SEM-based technique that extracts accurate feature shape information from images obtained during routine in-line wafer inspection. Intensity profiles from CD-SEM images of known materials are compared in real time to profiles in an off-line generated Monte-Carlo SEM simulation library for the same materials with various model shapes. When the best match is found, metrics like bottom CD, top CD, sidewall angle, foot size and angle, and corner rounding can be obtained with high accuracy.The proposed technique takes advantage of the high resolution and throughput of low-voltage CD-SEMs, and does not require any additional tool calibration beyond the standard calibrations performed for conventional top-down CD metrology. While similar to optical scatterometry in concept, this technique allows for measurement of both isolated targets and dense arrays. Examples of performance on etched polysilicon and resist lines of different shapes are included and compared to SEM cross-sections and CD-AFM data.

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“…In our ongoing study of MBL SEM metrology, we have been using MONSEL, a Monte Carlo SEM simulation developed at NIST. [10][11][12] MONSEL was the first program to model low-energy secondary electron generation, an important phenomenon in CD-SEM image formation. In fact, this software was intended primarily for applications in linewidth metrology.…”

Section: Sem Simulator Updatementioning

confidence: 99%

Application of model-based library approach to Si 3 N 4 hardmask measurements

et al. 2008

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The model-based library (MBL) matching technique was applied in hardmask linewidth metrology with a criticaldimension scanning electron microscope (CD-SEM). The MBL matching measures the edge positions and shapes of samples by comparing simulated images to measured images. To achieve reliable, stable measurements, two important simulation parameters were determined empirically. One was the beam width, and the other was a material parameter, the residual energy loss rate. This parameter is especially important for measurement of hardmask patterns, which have relatively high SEM image contrast. These simulation parameters were estimated so as to fit to actual SEM images, and then pinned to the estimated values during MBL matching. Hardmask patterns made of Si 3 N 4 were measured by MBL matching with the estimated parameters. The accuracy of the measurements was evaluated by one-to-one comparison with atomic force microscope (AFM) results. The pattern profile deduced from only the top-down CD-SEM image with MBL matching agreed well with the AFM profile and a scanning transmission electron microscope (STEM) crosssectional image. The average measurement bias between the MBL matching and AFM results was 1.58 nm for the bottom CD and -0.64 nm for the top CD, with a standard deviation of about 1.3 nm.

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Monte Carlo simulation of scanning electron microscope signals for lithographic metrology

Cited by 49 publications

References 8 publications

An implementation of discrete electron transport models for gold in the Geant4 simulation toolkit

An implementation of discrete electron transport models for gold in the Geant4 simulation toolkit

CD-SEM-based critical shape metrology of integrated circuits

Application of model-based library approach to Si 3 N 4 hardmask measurements

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