Water immersion optical lithography for 45-nm node

Smith, Bruce W.; Kang, Houyang; Bourov, Anatoly; Cropanese, Frank; Fan, Yongfa

doi:10.1117/12.485489

Cited by 17 publications

(11 citation statements)

References 4 publications

(3 reference statements)

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“…Finely tuned model based optical proximity correction (i.e., MBOPC) targeted toward process window expansion [7] relies on the accurate representation of compensating structures on the mask. Even the emerging efforts on 193 nm immersion lithography [8,9] require very high incident angles at the mask plane to realize the full benefits of the immersion approach. Such high incident angles at the mask are expected to introduce many new complexities into photomask content engineering and understanding [10].…”

Section: Introductionmentioning

confidence: 99%

Critical evaluation of photomask needs for competing 65-nm node RET options

Progler

Xiao

2003

SPIE Proceedings

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A comprehensive set of numerical, mask pattern operators is developed and applied for the purpose of understanding photomask fabrication tolerances supporting aggressive, optical lithography resolution enhancement. Using these numerical operators, the content and fidelity of the photomask is systematically degraded and wafer level results predicted using experimentally calibrated simulation. The concept of a mask sensitivity matrix is introduced and used as a bridge to full Monte Carlo analysis of photomask fabrication errors. A statistical approach to analyze mask defect tolerances for resolution enhancement options is presented within the same numerical framework. Such methodical and detailed analysis of mask construction parameters is a vital step toward understanding the complex interaction between mask quality and printed image and hence the delivery of 65 nm node lithography capability.

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Section: Introductionmentioning

confidence: 99%

Critical evaluation of photomask needs for competing 65-nm node RET options

Progler

Xiao

2003

SPIE Proceedings

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“…In the past few years, the difficulties in tackling these barriers have turned attentions to another alternative: immersion imaging at 193 nm. 1 Enhancement of optical resolution in immersion media with respect to air is described by Rayleigh's criteria, NA k sin n k R λ θ λ 1 1 = = . It states that the minimum resolvable pitch is inversely proportional to numerical aperture of the objective lens.…”

Section: Introductionmentioning

confidence: 99%

Study of air-bubble-induced light scattering effect on image quality in 193-nm immersion lithography

Fan

Lafferty

Bourov³

et al. 2004

SPIE Proceedings

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As an emerging technique, immersion lithography offers the capability of reducing critical dimensions by increasing numerical aperture (NA) due to the higher refractive indices of immersion liquids than that of air. Among the candidates for immersion liquids, water appears to be an excellent choice due to its high transparency at a wavelength of 193 nm, as well as its immediate availability and low processing cost. However, in the process of forming a water fluid layer between the resist and lens surfaces, air bubbles are often created due to the high surface tension of water. The presence of air bubbles in the immersion layer will degrade the image quality because of the inhomogeneity induced light scattering in the optical path. Therefore, it is essential to understand the air bubble induced light scattering effect on image quality. Analysis by geometrical optics indicates that the total reflection of light causes the enhancement of scattering in the region where the scattering angle is less than the critical scattering angle, which is 92 degrees at 193 nm. Based on Mie theory, numerical evaluation of scattering due to air bubbles, polystyrene spheres and PMMA spheres was conducted for TE, TM or unpolarized incident light. Comparison of the scattering patterns shows that the polystyrene spheres and air bubbles resemble each other with respect to scattering properties. Hence polystyrene spheres are used to mimic air bubbles in studies of lithographic imaging of "bubbles" in immersion water. In direct interference lithography, it is found that polystyrene spheres (2 µm in diameter) 0.3 mm away from the resist surface would not image, while for interferometric lithography at 0.5NA, this distance is estimated to be 1.3 mm. Surprisingly, polystyrene spheres in diameter of 0.5 µm (which is 5 times larger than the interferometric line-width) will not image. It is proposed that "bubbles" are repelled from contact with the resist film by surface tension. The scatter of exposure light can be characterized as "flare". This work shows that microbubbles are not a technical barrier to immersion lithography.

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“…In the past few years, the difficulties in tackling these barriers have turned attentions to another alternative: immersion imaging at 193 nm. 1 Enhancement of optical resolution in immersion media with respect to air is described by Rayleigh . It states that the minimum resolvable pitch is inversely proportional to numerical aperture of the objective lens.…”

Section: Introductionmentioning

confidence: 99%

Air bubble-induced light-scattering effect on image quality in 193 nm immersion lithography

et al. 2005

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As an emerging technique, water immersion lithography, offers the capability of reducing critical dimensions by increasing the numerical aperture that is due to the higher refractive indices of immersion liquids than that of air. However, in the process of forming a water fluid layer between the resist and the lens surfaces, air bubbles are often created because of the high surface tension of water. The presence of air bubbles in the immersion layer will degrade the image quality because of the inhomogeneity-induced light scattering in the optical path. Analysis by geometrical optics indicates that the total reflection of light causes the enhancement of scattering in the region in which the scattering angle is less than the critical scattering angle, which is 92 deg at 193 nm. Based on Mie theory, numerical evaluation of scattering that is due to air bubbles, polystyrene spheres, and poly(methyl methacrylate) spheres was conducted for TE, TM, or unpolarized incident light. Comparison of the scattering patterns shows that the polystyrene spheres and air bubbles resemble each other with respect to scattering properties. In this paper, polystyrene spheres are used to mimic air bubbles in studies of lithographic imaging of bubbles in immersion water. In an interferometric lithography system, the distance beyond which bubbles will not print can be estimated by direct counting of defect sites.

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Water immersion optical lithography for 45-nm node

Cited by 17 publications

References 4 publications

Critical evaluation of photomask needs for competing 65-nm node RET options

Critical evaluation of photomask needs for competing 65-nm node RET options

Study of air-bubble-induced light scattering effect on image quality in 193-nm immersion lithography

Air bubble-induced light-scattering effect on image quality in 193 nm immersion lithography

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