Alignment Focus Optimization and Image Contrast

Sugaya, Ayako

doi:10.1143/jjap.44.5970

Cited by 3 publications

(2 citation statements)

References 7 publications

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“…Recent exposure apparatus includes a two-dimensional digital imaging sensor utilizing wideband white light, which has little sensitivity to variations in the resist thickness. [25][26][27][28][29][30] The experimental and theoretical confirmation of the FWM metrology concept in the latest ArF exposure apparatus are topics for future research.…”

Section: Embedment To Feedback System Of Exposure Apparatusmentioning

confidence: 99%

Accuracy of focus wedge mark measurement using fitting function for partially coherent illumination

Yashiki¹,

Suwa²,

Takeuchi³

2015

Jpn. J. Appl. Phys.

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The theory of best focus determination in focus wedge mark (FWM) metrology is extended from coherent illumination to partially coherent illumination. Through a theoretical analysis, we propose a focus curve fitting function suitable for the FWM, which is expressed by the sinc function. The experimental results for best focus estimations using two types of fitting functions, which are a conventional quadratic polynomial and the proposed sinc function, are reported for various defocus regions to be fitted. When the first inflection points of the sinc function are included in the fitting defocus region, we can achieve stable best focus estimation within 3 nm in our i-line exposure experiments.

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Section: Embedment To Feedback System Of Exposure Apparatusmentioning

confidence: 99%

Accuracy of focus wedge mark measurement using fitting function for partially coherent illumination

Yashiki¹,

Suwa²,

Takeuchi³

2015

Jpn. J. Appl. Phys.

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“…The measurement is usually performed with an exposure apparatus equipped with a laser spot sensor employing a monochromatic wavelength, 14) but recently we have employed a two-dimensional digital imaging sensor utilizing wideband white light, which has little sensitivity to variations in the resist thickness. [25][26][27][28][29][30] Both of these sensors detect the tip of the FWM on the resist and determine the length using several algorithms. The thinnest point of the resist is at the tip, and this three-dimensional structure can sometimes lead to an undesirable optical interference phenomenon in the laser spot measurement and increase the uncertainty in the FWM length measurement.…”

Section: Measurement Accuracymentioning

confidence: 99%

Theoretical analysis of focus wedge mark for best-focus determination in photolithography

Suwa¹,

Yashiki²,

Hirukawa³

2014

Jpn. J. Appl. Phys.

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The focus wedge mark (FWM), a periodic array of wedge shaped marks, is a tool used to determine the best-focus position in photolithography. Here, we develop a one-dimensional physical model for the FWM and analyze the focus dependence of the wedge length under coherent imaging conditions. The amplification factor of the FWM, which describes the superiority of the FWM compared to measurements based on line and space marks, is determined by the geometrical magnification of the wedge. We show that around the exposure dose energy typically used in lithography the amplification factor is much higher than the geometrical magnification. Numerical lithography simulations confirm that the focus sensitivity of the FWM is much higher than that of a line and space pattern.

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Focus calibration method based on the illumination beam scanning angle modulation in a grating alignment system

Zhang

Sun

et al. 2021

Opt. Express

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A focus calibration method is developed to determine the focus position of a grating alignment system. An illumination beam scanning module is utilized to generate a circular motion for the beam, which forms an angular modulation interference image on the reference mark. A theoretical model is presented to determine the focus by determining the alignment grating z-position, at which the alignment offset is independent of the incident beam tilt. The standard uncertainty of the focus calibration results is estimated to be better than 150 nm. This technique may improve the measurement performance for lithography systems and precision machine applications.

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Alignment Focus Optimization and Image Contrast

Cited by 3 publications

References 7 publications

Accuracy of focus wedge mark measurement using fitting function for partially coherent illumination

Accuracy of focus wedge mark measurement using fitting function for partially coherent illumination

Theoretical analysis of focus wedge mark for best-focus determination in photolithography

Focus calibration method based on the illumination beam scanning angle modulation in a grating alignment system

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