Investigation of cross-field wavefront aberrations of KrF lithography exposure systems as a function of excimer laser bandwidth

Lalovic, Ivan; Kroyan, Armen; Farrar, Nigel R.; Taitano, Dennis; Zambon, Paolo; Smith, Adlai H.

doi:10.1117/12.435655

Cited by 4 publications

(3 citation statements)

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“…For this system, the results indicate approximately 250nm of focus shift per 1 pm of wavelength offset for 0.6NA and is consistent with previously published results. [4,5] The R 2 values range from 0.993 to 0.999, showing very good linearity across the 6pm wavelength range. The across-field focus variation is approximately 0.4µm in this result and is caused by a field leveling (software) offset, which is constant for these experiment conditions.…”

Section: Longitudinal Chromatic Aberrationmentioning

confidence: 94%

“…Although other aberrations have been shown to vary with wavelength, the simplified approach is consistent with high precision in-situ chromatic aberration measurements reported previously for exposure systems of similar type. [4,5] A refined model of the UV5 photoresist performance is developed matching closely the physical photoresist and developer recipe settings. The simulation results are analyzed to estimate the exposure latitude, MEEF as well as response of isolated and dense line structures.…”

Section: Lithography Modelingmentioning

confidence: 99%

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Illumination spectral width impacts on mask error enhancement factor and iso-dense bias in 0.6-NA KrF imaging

Lalovic¹,

Kroyan²,

Zambon³

et al. 2002

21st Annual BACUS Symposium on Photomask Technology

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In this study, process latitude, mask error enhancement factor and iso-dense bias have been experimentally measured as a function of the KrF excimer laser bandwidth. The experiment results are in agreement with photoresist simulations over a range of imaged nominal feature sizes from 120nm to 300nm at 0.6/0.75 NA/σ. The mask error enhancement factor (MEEF) is shown to vary by approximately 2.3% for 160nm and 3.3% for 150nm isolated lines per 0.1pm of excimer-laser bandwidth, characterized by the full width at half maximum (FWHM). The 180nm line iso-dense bias exhibits a shift of approximately 2nm per 0.1pm FWHM. Under the given process conditions, linear empirical relationships are derived for the dependency of MEEF and iso-dense offset on FWHM excimer-laser spectral width for a range of imaged CDs. Such considerations can be used to augment the existing predictive CD-control estimation and modelbased optical proximity correction.

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Section: Longitudinal Chromatic Aberrationmentioning

confidence: 94%

Section: Lithography Modelingmentioning

confidence: 99%

Illumination spectral width impacts on mask error enhancement factor and iso-dense bias in 0.6-NA KrF imaging

Lalovic¹,

Kroyan²,

Zambon³

et al. 2002

21st Annual BACUS Symposium on Photomask Technology

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“…The relatively high spectral purity of frequency-narrowed excimer lasers allows these chromatic optics to deliver useful imaging, but as NA increases so does the need for narrower bandwidth [2][3][4][5][6][7][8][9] . The experimental data show Γ=0.37pm, well within the 0.5pm specification of this laser.…”

Section: Laser Bandwidthmentioning

confidence: 99%

Laser bandwidth and other sources of focus blur in lithography

et al. 2006

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It is well known that the refractive optics used in today's exposure tools are highly chromatic, meaning that small wavelength shifts will cause large focus shifts. Even a line-narrowed excimer laser has a large enough range of wavelengths that we can no longer think of an infinitely thin image plane. The concept of "focus blur" can be generalized to encompass the effect of laser bandwidth chromatic aberrations, vertical stage vibrations (MSDz) and stage tilts which cause focus to change during the scan. This paper will introduce a new parameter called Mean Absolute Defocus (MAD) that can characterize the focus blur, and will be shown to correlate with the lithographic effects.Focus blur can be incorporated into simulation models, in a manner similar to the way that stage vibration is modeled. New simulation results will illustrate the impact of focus blur on modern lithographic processes. Process stability and machine-to-machine matching issues will be discussed.

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