Sidewall structure estimation from CD-SEM for lithographic process control

Bingham, Philip R.; Price, Jeffery R.; Tobin, Kenneth W.; Karnowski, Thomas P.; Bennett, Marylyn Hoy; Bogardus, E. Hal; Bishop, Michael

doi:10.1117/12.485229

Cited by 7 publications

(6 citation statements)

References 7 publications

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“…Precise measurement of sidewall angle has become increasingly important in the semiconductor industry for high precision measurement of the full width half maximum gate linewidth [5]; with decreasing gate line-width dimension. The most common source of sidewall angle variation is photoresist exposure due to focus variation.…”

Section: Resultsmentioning

confidence: 99%

“…However, the measurement accuracy for all of the above-mentioned technologies is decreasing with the ever decreasing nanostructure sizes. OM cannot measure the shape of objects with lateral sizes less than 1 μm; AFM cannot accurately measure shape but can measure the nanostructure height if the separation width is longer than the tip width; lateral and vertical dimensions from SEM pictures are hard to obtain if the width of the borderline produced by the secondary electron becomes a significant part of the dimension to be measured [5]. Scatterometry and Mueller ellipsometry can measure the shape of periodic nanostructures [6][7][8]; however, the accuracy of the shape dimensions decrease with decreasing nanostructure sizes and increasing complexity.…”

Section: Introductionmentioning

confidence: 99%

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Enhanced Measurement Accuracy for Nanostructures Using Hybrid Metrology

Hansen¹,

Johannsen²,

Jensen³

et al. 2022

Front. Phys.

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Light-matter interplay is widely used for analyzing the topology of surfaces on small scales for use in areas such as nanotechnology, nanoelectronics, photonics, and advanced materials. Conventional optical microscope imaging methods are limited in resolution to a value comparable to the wavelength, the so-called Abbe limit, and cannot be used to measure nano-sized structures. Scatterometry and Mueller ellipsometry are spectroscopic optical methods that can measure structures smaller than the wavelength. However, the relative uncertainties of the structure dimensions measured with scatterometry increase with decreasing structure size, and the industry is therefore replacing simple intensity based scatterometry with Mueller ellipsometry for the most demanding measurements. The accuracy of Mueller ellipsometry and scatterometry are closely related to the ability of the employed regression and regularization algorithms to extract the structural dimension. In this work, we demonstrate how the measurement accuracy on three-dimensional periodic structures may be increased by measuring the same periodic structure with multiple techniques and applying a χ2-regression method that finds the best solution based on the input from all the instruments. We furthermore report on a new and improved calibration method for Mueller ellipsometry and demonstrate how the Mueller matrix may be used to find the geometrical anisotropy of the structure.

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Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Enhanced Measurement Accuracy for Nanostructures Using Hybrid Metrology

Hansen¹,

Johannsen²,

Jensen³

et al. 2022

Front. Phys.

View full text Add to dashboard Cite

show abstract

“…In the past years, several different techniques have been proposed to obtain a direct measurement of this quantity, examples can be Atomic Force Microscopy (AFM) and Scanning Electron Microscopy (SEM); nevertheless, technological innovation soon demanded more accurate and reliable metrology tools. For this reason, researchers developed numerous variations of the aforementioned techniques, such as a tilt-scanning method for AFM [4], Critical Dimension AFM [5] and Critical Dimension SEM [6]. These measuring tool all have the great feature of being able to perform non-destructive measurement, nevertheless they all have different drawbacks (for instance the Rayleigh diffraction limit for the AFM) affecting their performances.…”

Section: Introductionmentioning

confidence: 99%

Amplitude and phase beam shaping for highest sensitivity in sidewall angle detection

Cisotto

Urbach

2016

J. Opt. Soc. Am. A

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In optical metrology, grating-like structures are used as tools to evaluate the performance of lithographic techniques. In particular, several shape parameters characterize those structures. One of them, termed side-wall angle, suffers from a considerable high error estimation. Using mathematical optimization, we investigated whether a properly shaped beam could increase the ability to detect tiny changes of this angle in the case of a cliff-like structure. This paper describes the theoretical formulation used to calculate the optimized beam and compares its performance with the case of a plane wave. The results indicate that the sensitivity increases by several folds by using the optimized solution. Still, such an optimization process needs to be extended to the more general vectorial case.

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“…Since CD-SEM tools that capture top-down images are currently being used for measurement of CD, we investigated the possibility of estimating sidewall shape using only features extracted from top-down images and a database of corresponding historical topdown and cross-section images. 1,2 In this paper, we propose an image retrieval system to estimate sidewall structure from top-down imagery. Features from a top-down query image are compared to a database of features from other top-down images, each with known corresponding sidewall shapes.…”

Section: Introductionmentioning

confidence: 99%

Semiconductor sidewall shape estimation

Bingham

2004

J. Electron. Imaging

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For process control, linewidth measurements are commonly performed on semiconductor wafers using top-down images from critical dimension measurement scanning electron microscopes (CD-SEMs). However, a measure of the line sidewall shape will be required as linewidths continue to shrink. Sidewall shape can be measured by physically cleaving the device and performing an SEM scan of the cross section, but this process is time consuming and results in destruction of product wafers. We develop a technique to estimate sidewall shape from top-down SEM images using pattern recognition based on historical cross section/top-down image pairs. Features are computed on subimages extracted from the top-down images. Several combinations of principal component analysis (PCA) and flavors of linear discriminant analysis (LDA) are employed to reduce the dimensionality of the feature vectors and maximize the spread between different sidewall shapes. Direct, weighted LDA (DW-LDA) results in a feature set that provides the best sidewall shape estimation. Experimental testing of the sidewall estimation system shows a root mean square error of approximately 1.8% of the linewidth, showing that this system is a viable method for estimating sidewall shape with little impact on the fabrication process (no new hardware and a minimal increase in process setup).

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Sidewall structure estimation from CD-SEM for lithographic process control

Cited by 7 publications

References 7 publications

Enhanced Measurement Accuracy for Nanostructures Using Hybrid Metrology

Enhanced Measurement Accuracy for Nanostructures Using Hybrid Metrology

Amplitude and phase beam shaping for highest sensitivity in sidewall angle detection

Semiconductor sidewall shape estimation

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