Mask error factor: critical dimension variation across different tools, features, and exposure conditions

Jekauc, Igor; Roberts, W.; Hampe, Christine

doi:10.1117/12.435784

Cited by 3 publications

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“…Typical experimental methods may carry an error as much as 10 to 20 nm. Also, as the lithographic dimension gets smaller, mask error factor (MEF) becomes larger and starts to limit CD control [5][6][7][8][9][10][11]. In this paper, we present a systematic study, which will introduce a very accurate measurement method (to 1 to 2 nm) for the resist diffusion length and a theoretical framework for the evaluation of the effect of such diffusion to the image contrast and MEF under various illumination and mask conditions for photolithography at 65 nm and 45 nm nodes.…”

Section: Introductionmentioning

confidence: 99%

Effect of the effective resist diffusion length to the photolithography at 65- and 45-nm nodes: a study with simple and accurate analytical equations

Wu¹,

Halle²,

Zhao³

2004

SPIE Proceedings

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As the current photolithography moves toward the 65 and 45 nm nodes, resist blur, which is now around 50 to 90 nm full width at half maximum (FWHM), starts to limit the printability of narrow pitches by lowering image contrast, increasing mask error factor (MEF), and changing critical dimension (CD) through pitch behavior. Since such resist blur is known to originate from acid and base diffusion, which is an important process for chemical amplification, the reduction of such blur may affect the resist performance. Therefore, knowing how much diffusion can be tolerated at any given lithographic condition is critical to the success of photolithography at the 65 and 45 nm nodes.In this paper, we present a systematic study of the effect of the resist diffusion with a series of simple and accurate analytic equations and experimental data for the 193 nm lithography. We also extend our predictions to the 193 nm immersion lithography. We first show a simple way to accurately measure the effective resist diffusion length through the regular wafer exposure method for many typical resists. We then show a method to accurately quantify the contrast reduction due to such resist diffusion for both alternating phase shifting masks (Alt-PSM) and attenuated phase shifting masks (Att-PSM). We conclude that the contrast reduction is very significant with typical 193 nm resists, which have diffusion lengths of around 30 to 40 nm. In the study, we found that the mask error factor (MEF), though dependent on the illumination condition, is a strong function of the resist diffusion length at any given illumination condition. For example, in the alt-PSM case, the MEF is almost entirely determined by the resist diffusion. In the att-PSM case, however, the MEF is only partially dependent on the resist diffusion length, about 50%. In fact, a short diffusion length of less than 20 nm will be required to extend its litho-worthiness to the 45 nm node with contrast levels comparable to the current ones. Plots of the contrast and MEF through pitch for both alt-PSM and att-PSM for various diffusion lengths under typical lithographic conditions will be presented. Experimental verification of the above analytical equations will be presented.

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Section: Introductionmentioning

confidence: 99%

Effect of the effective resist diffusion length to the photolithography at 65- and 45-nm nodes: a study with simple and accurate analytical equations

Wu¹,

Halle²,

Zhao³

2004

SPIE Proceedings

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Full-field exposure control implications of the mask error function

Zavecz¹

2006

SPIE Proceedings

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Precise measurement of process bias and its relation to MEEF

Zavecz¹

2007

SPIE Proceedings

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This paper was published in SPIE Vol 6520-139 and is made available as an electronic reprint or preprint with permission of SPIE. One print or electronic copy may be made for personal use only. Systematic or multiple reproduction, distribution to multiple locations via electronic or other means, duplication of any material in this paper for a fee or for commercial purposes or modification of the content of the paper are prohibited.

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Mask error factor: critical dimension variation across different tools, features, and exposure conditions

Cited by 3 publications

References 0 publications

Effect of the effective resist diffusion length to the photolithography at 65- and 45-nm nodes: a study with simple and accurate analytical equations

Effect of the effective resist diffusion length to the photolithography at 65- and 45-nm nodes: a study with simple and accurate analytical equations

Full-field exposure control implications of the mask error function

Precise measurement of process bias and its relation to MEEF

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