Pellicle-induced aberrations and apodization in hyper-NA optical lithography

Bubke, Karsten; Alles, Benjamin; Cotte, Eric; Sczyrba, Martin; Pierrat, Christophe

doi:10.1117/12.681871

Cited by 11 publications

(8 citation statements)

References 9 publications

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“…After adjustment of the wafer and reticle height to take out Z4 the lowest order spherical aberration term (an action that automatically occurs in the scanner before exposure), mostly Z9 remains, with a value up to ∼3 mλ for 1.35 NA. 2,3 In the case of the thin pellicle, the above-mentioned phase effects are negligible.…”

Section: Simulationsmentioning

confidence: 95%

“…1 In literature, a number of studies can be found where this concern is quantified by simulations, and clear guidelines are provided on how to model the pellicle effects. 2,3 As far as experimental wafer data is concerned, there are only a few examples and, to our knowledge, none are at 1.35 NA. The paper by Luo et al 4 contains experimental and modeling data at 1.2 NA showing the pellicle effect of several nm for lines through pitch with varying CDs ranging from 55 to 65 nm.…”

Section: Introductionmentioning

confidence: 97%

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Pellicle contribution to optical proximity and critical dimension uniformity for 1.35 numerical aperture immersion ArF lithography

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Bekaert

Laenens

et al. 2011

J. Micro/Nanolith. MEMS MOEMS

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Pellicles are mounted on the masks used in ArF lithography for integrated circuit manufacturing to ensure defect-free printing. The pellicle, a thin transparent polymer film, protects the reticle from dust. But, as the light transmittance through the pellicle has an angular dependency, the pellicle also acts as an apodization filter. In the current work, we present both experimental and simulation results at 1.35 numerical aperture immersion ArF lithography showing the influence of two types of pellicles on proximity and intra-die critical dimension uniformity (CDU). To do so, we mounted and dismounted the different pellicle types on one and the same mask. The considered structures on wafer are compatible with the 32-nm logic node for poly and metal. For the standard ArF pellicle (thickness 830 nm), we experimentally observe a distinct effect of several nm due to the pellicle presence on both the proximity and the intra-die CDU. For the more advanced pellicle (thickness 280 nm), no signature of the pellicle on proximity or CDU could be found. By modeling the pellicle's optical properties as a Jones Pupil, we are able to simulate the pellicle effects with good accuracy. These results indicate that for the 32-nm node, it is recommended to take the pellicle properties into account in the optical proximity correction calculation when using a standard pellicle. In addition, simulations also indicate that a local dose correction can compensate to a large extent for the intra-die pellicle effect. When using the more advanced thin pellicle (280 nm), no such corrections are needed. C 2011 Society of Photo-Optical Instrumentation Engineers (SPIE).

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Section: Simulationsmentioning

confidence: 95%

Section: Introductionmentioning

confidence: 97%

Pellicle contribution to optical proximity and critical dimension uniformity for 1.35 numerical aperture immersion ArF lithography

Look

Bekaert

Laenens

et al. 2011

J. Micro/Nanolith. MEMS MOEMS

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“…method will induce a loss of high-spatial-frequency transmitted intensity, which is similar in form and in negative impact to a strong lens-apodization effect. 8,9 The fundamental problem with pellicle transmission as a function of angle is well understood, being simply a thinfilm optics interference effect. Figure 12 shows the issue for a typical thin organic 193-nm pellicle.…”

Section: Trapezoidal Filter Modelmentioning

confidence: 99%

Novel apodization and pellicle optical models for accurate optical proximity correction modeling at 45 and <inline-formula><math altimg="none" display="inline" overflow="scroll"><mrow><mn>32</mn><mspace width="0.3em" /><mi>nm</mi></mrow></math></inline-formula>

Zhang

Lucas

Adrichem³

et al. 2007

J. Micro/Nanolith. MEMS MOEMS

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An accurate optical model is the foundation of an accurate optical proximity correction ͑OPC͒ model, which has always been the key for successful implementation of model-based OPC. As critical dimension ͑CD͒ control requirements become severe at the 45-and 32-nm device generations, OPC model accuracy and hence optical model accuracy requirements become more stringent. In previous generations, certain optical effects could be safely ignored. For example, the transmission attenuation particularly at high spatial frequencies caused by lens apodization effects and organic pellicle films was ignored or not accurately modeled in conventional OPC simulators. These effects are now playing a more important role in OPC modeling as technology scales down. Our simulations indicate these effects can cause CD modeling errors of 5 nm or larger, at the 45-nm technology node and beyond. Therefore, they must be accurately modeled in OPC modeling. In our OPC modeling methodology, we propose two novel low-pass-filter models to capture the frequency-dependent transmission attenuation due to lens apodization and to pellicle films. These parameterized novel lowpass-filter models ensure that lens apodization and pellicle-film-induced transmission attenuation can be appropriately account for through regression during the experimental OPC model calibration stage in the case where no measured transmission data are available, thus enabling physics-centric OPC model building with considerably higher accuracy. We can then avoid overfitting the OPC model, which could cause instability in the OPC correction stage. The validity and efficiency of the proposed novel models are also verified using an industry-standard lithography simulator as well as an experimental OPC model calibration at the 45-nm technology node.

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“…No pellicle was used on these reticles to eliminate any pellicle BR effects. 9 The patterned reticles were sent to Hinds Instruments to measure the BR and fast axis angles at 193nm. 10,11 Five measurements were taken through the open area in each die and averaged.…”

Section: Reticle Set Upmentioning

confidence: 99%

Effects of reticle birefringence on 193nm lithography

et al. 2007

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Unpolarized light has traditionally been used for photolithography. However, polarized light can improve contrast and exposure latitudes at high numerical aperture (NA), especially for immersion lithography with an NA > 1.0. As polarized light passes through a reticle, any birefringence (BR) in the reticle material can cause a change in the orientation or degree of polarization, reducing the contrast in the final resist image. This paper shows the effects of reticle BR on dry and immersion imaging for 193nm lithography. The BR magnitude and orientation of the fast axis were mapped across several unpatterned mask blanks, covering a range of BR from 0 to 10 nm/cm. These reticles were printed with a series of open areas surrounded by test structures. The BR was measured again on the patterned reticles, and several locations were selected to cover a range of magnitudes at different orientations of the fast axis. Dry and immersion imaging were evaluated, looking at BR effects on dense lines and contact structures. Mask error enhancement factor (MEEF), line edge roughness (LER), and dose and focus latitudes were studied on line/space patterns. Dose and focus latitudes and 2-D effects were studied on contact patterns. Based upon these results, the effect of reticle BR on CD is minimal, even for BR values up to 10 nm/cm.

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Pellicle-induced aberrations and apodization in hyper-NA optical lithography

Cited by 11 publications

References 9 publications

Pellicle contribution to optical proximity and critical dimension uniformity for 1.35 numerical aperture immersion ArF lithography

Pellicle contribution to optical proximity and critical dimension uniformity for 1.35 numerical aperture immersion ArF lithography

Novel apodization and pellicle optical models for accurate optical proximity correction modeling at 45 and <inline-formula><math altimg="none" display="inline" overflow="scroll"><mrow><mn>32</mn><mspace width="0.3em" /><mi>nm</mi></mrow></math></inline-formula>

Effects of reticle birefringence on 193nm lithography

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