Evaluation of a new metrology technique to support the needs of accuracy, precision, speed, and sophistication in near-future lithography

Ke, Chih-Ming; Hu, Jimmy; Wang, Willie; Huang, Jacky; Chung, H. L.; Liang, C. R.; Shih, Victor; Liu, H. H.; Lee, H. J.; Lin, John C.; Fan, Yang-Tung; Bhattacharyya, Kaustuve; Schaar, Maurits van der; Wright, Noelle; Yuan, Kiwi; Wang, Vivien; Wang, Cathy; Lin, Spencer; Shahrjerdy, Mir; Fuchs, Andreas; Mast, K.D. van der

doi:10.1117/12.814860

Cited by 15 publications

(3 citation statements)

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“…Unfortunately this assumption is unrealistic and leads to inaccuracy [4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20][21]. There are different types of metrology target asymmetries that contaminate the signal and mix with the overlay-induced asymmetry.…”

Section: Overlay Metrology In the Accuracy Agementioning

confidence: 99%

Accuracy in optical overlay metrology

et al. 2016

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In this paper we discuss the mechanism by which process variations determine the overlay accuracy of optical metrology. We start by focusing on scatterometry, and showing that the underlying physics of this mechanism involves interference effects between cavity modes that travel between the upper and lower gratings in the scatterometry target. A direct result is the behavior of accuracy as a function of wavelength, and the existence of relatively well defined spectral regimes in which the overlay accuracy and process robustness degrades (`resonant regimes'). These resonances are separated by wavelength regions in which the overlay accuracy is better and independent of wavelength (we term these `flat regions'). The combination of flat and resonant regions forms a spectral signature which is unique to each overlay alignment and carries certain universal features with respect to different types of process variations. We term this signature the `landscape', and discuss its universality. Next, we show how to characterize overlay performance with a finite set of metrics that are available on the fly, and that are derived from the angular behavior of the signal and the way it flags resonances. These metrics are used to guarantee the selection of accurate recipes and targets for the metrology tool, and for process control with the overlay tool. We end with comments on the similarity of imaging overlay to scatterometry overlay, and on the way that pupil overlay scatterometry and field overlay scatterometry differ from an accuracy perspective.

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Section: Overlay Metrology In the Accuracy Agementioning

confidence: 99%

Accuracy in optical overlay metrology

et al. 2016

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“…Lens aberrations and illumination imperfections, as well as wafer process variations, can introduce an offset called tool-induced shift (TIS) in IBO [7,8] . DBO metrology has become a promising method, as it has been shown to have significantly reduced total measurement uncertainty (TMU) compared to the industry standard IBO due to its unmeasurable TIS [9][10][11] . It has been reported that DBO offers better precision than IBO [12] .…”

Section: Introductionmentioning

confidence: 99%

Improving accuracy and sensitivity of diffraction-based overlay metrology

Yang¹,

Lin²,

Wei³

et al. 2023

中国光学快报

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Overlay (OVL) for patterns placed at two different layers during microchip production is a key parameter that controls the manufacturing process. The tolerance of OVL metrology for the latest microchip needs to be at nanometer scale. This paper discusses the influence on the accuracy and sensitivity of diffraction-based overlay (DBO) after developing inspection and after etching inspection by the asymmetrical deformation of the OVL mark induced by chemical mechanical polishing or etching. We show that the accuracy and sensitivity of DBO metrology can be significantly improved by matching the measuring light wavelength to the thickness between layers and by collecting high-order diffraction signals, promising a solution for future OVL metrology equipment.

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“…Amongst various techniques, scatterometry is a promising candidate for meeting all the requirements. It can rapidly acquire average properties of periodic features over a relatively large area, and with proper set-ups by connecting to a scanner and a track, sub-nanometer variations can be identified and achieved 2,3 . Evaluations of the ability of scatterometry to measuring CD, SWA, and overlay have been made [4][5][6][7] .…”

Section: Introductionmentioning

confidence: 99%

Electron-beam proximity effect model calibration for fabricating scatterometry calibration samples

et al. 2012

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Scatterometry has been proven to be effective in critical dimension (CD) and sidewall angle (SWA) measurements with good precision and accuracy. In order to study the effectiveness of scatterometry measurement of line edge roughness (LER), calibration samples with known LER have to be fabricated precisely. The relationship between ITRS LER specifications and the feature dimension design of the LER calibration samples is discussed. Electron-beam-direct-write lithography (EBDWL) has been widely used in nanoscale fabrication and is a natural selection for fabricating the designed calibration samples. With the increasingly demanding requirement of lithography resolution in ITRS, the corresponding LER feature of calibration samples becomes more and more challenging to fabricate, even for EBDWL. Proximity effects in EBDWL due to electron scattering can cause significant distortion of fabricated patterns from designed layouts. Model-based proximity effect correction (MBPEC) is an enhancement method for EBDWL to precisely define fine resist features. The effectiveness of MBPEC depends on the availability of accurate electron-beam proximity effect models, which are usually described by point spread functions (PSFs). In this work, a PSF in a doubleGaussian function form at a 50 kV accelerating voltage, an effective beam size, and a development threshold energy level of the resist are calibrated with EBDWL exposure tests. Preliminary MBPEC results indicate its effectiveness in calibration sample fabrication.Keywords: scatterometry, programmed LER structures, electron beam direct write lithography, proximity effect, proximity effect correction, model calibration INTRODUCTIONAs the minimum half pitch of integrated circuits is approaching 32 nm and below, urgent needs for near-ideal metrology technology are being called. Typical requirements for metrology include richness of measurement information, measurement speed, non-destructiveness of measurement processes, and capability of measuring process fluctuation 1 . Amongst various techniques, scatterometry is a promising candidate for meeting all the requirements. It can rapidly acquire average properties of periodic features over a relatively large area, and with proper set-ups by connecting to a scanner and a track, sub-nanometer variations can be identified and achieved 2, 3 . Evaluations of the ability of scatterometry to measuring CD, SWA, and overlay have been made 4-7 . Feature sizes down to 20 nm have been evaluated and correlated to critical dimension scanning electron microscopy (CD-SEM) with good results 1, 8 .Line edge roughness (LER) and line width roughness (LWR) are among the factors influencing device performances because they can affect dopant concentration profile and are responsible for gate leakage 9, 10 . Scatterometry has shown good sensitivity to roughness of 7.5 to 10 nm 10, 11 . The performance of scatterometery has been compared to alternative tools such as CD-SEM, atomic force microscopy, dual beam focused ion beam, and high-voltage SEM. It appears th...

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Evaluation of a new metrology technique to support the needs of accuracy, precision, speed, and sophistication in near-future lithography

Cited by 15 publications

References 0 publications

Accuracy in optical overlay metrology

Accuracy in optical overlay metrology

Improving accuracy and sensitivity of diffraction-based overlay metrology

Electron-beam proximity effect model calibration for fabricating scatterometry calibration samples

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