Modeling of EUV photoresists with a resist point spread function

Cain, Jason P.; Naulleau, Patrick; Spanos, Costas J.

doi:10.1117/12.600439

Cited by 12 publications

(17 citation statements)

References 9 publications

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“…Fortunately, an approximate and efficient resist model based on the resist PSF was proposed and has been shown to have good agreement with the experiments' results [9]. This approximate resist model is tailored to the EUV ILT due to its computational efficiency and the analytic form.…”

Section: B Modeling Of the Photoresist Effectmentioning

confidence: 84%

“…An accurate EUV photoresist model is often represented by a complex system of differential equations, making it fairly computationally intensive [2,9]. Fortunately, an approximate and efficient resist model based on the resist PSF was proposed and has been shown to have good agreement with the experiments' results [9].…”

Section: B Modeling Of the Photoresist Effectmentioning

confidence: 97%

“…In addition, similar to DUV lithography, the image fidelity of EUV lithography is affected by the optical proximity effect (OPE) due to diffraction and interference. Finally, as the light is projected onto the wafer, the photoresist effect must be considered in the image fidelity evaluation [2,7,9]. All of the effects mentioned above can introduce image distortion in the EUV lithography systems and will be considered in this paper.…”

Section: Introductionmentioning

confidence: 99%

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Gradient-based inverse extreme ultraviolet lithography

Ma¹,

Wang²,

Chen³

et al. 2015

Appl. Opt.

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Extreme ultraviolet (EUV) lithography is the most promising successor of current deep ultraviolet (DUV) lithography. The very short wavelength, reflective optics, and nontelecentric structure of EUV lithography systems bring in different imaging phenomena into the lithographic image synthesis problem. This paper develops a gradient-based inverse algorithm for EUV lithography systems to effectively improve the image fidelity by comprehensively compensating the optical proximity effect, flare, photoresist, and mask shadowing effects. A block-based method is applied to iteratively optimize the main features and subresolution assist features (SRAFs) of mask patterns, while simultaneously preserving the mask manufacturability. The mask shadowing effect may be compensated by a retargeting method based on a calibrated shadowing model. Illustrative simulations at 22 and 16 nm technology nodes are presented to validate the effectiveness of the proposed methods.

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Section: B Modeling Of the Photoresist Effectmentioning

confidence: 84%

Section: B Modeling Of the Photoresist Effectmentioning

confidence: 97%

Section: Introductionmentioning

confidence: 99%

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Gradient-based inverse extreme ultraviolet lithography

Ma¹,

Wang²,

Chen³

et al. 2015

Appl. Opt.

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“…So, EUVL should be useful for the mass production of ULSI devices with a half pitch (hp) of 45 nm or less. Previous studies [4][5][6] showed that the shapes of resist patterns printed by EUVL were deformed when the pattern size was less than 60 nm. This might be because the performance of the resist and/or projection optics is not high enough.…”

Section: Introductionmentioning

confidence: 98%

Fidelity of rectangular patterns printed with 0.3-NA MET optics

et al. 2007

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Arrays of rectangular patterns of various sizes were printed with the EUV micro-exposure tool (MET) at the Lawrence Berkeley National Laboratory (LBNL) using the chemically-amplified resist MET-1K; and their fidelity to the mask patterns was evaluated. The experimental results showed that the shortening of resist patterns in the lengthwise direction was greater for smaller patterns. For example, the line-end shortening of half-pitch (hp) 45-nm patterns was about 20-25 nm on one side, while that of hp-90-nm patterns was less than 10 nm. However, simulated aerial images exhibited little shortening, even for hp-45-nm patterns. On the other hand, considerable shortening appeared in hp-45-nm patterns after post-exposure-baking (PEB) process. When the acid diffusion length in the PEB process was assumed to be 20 nm, the calculated shapes of resist patterns agreed well with the experimental results for various sizes. Printing experiments showed that lowering the PEB temperature improved fidelity, probably due to the shorter acid diffusion length. Thus, we concluded that acid diffusion is the main cause of shortening in rectangular patterns printed with the MET. For better pattern fidelity, the acid diffusion length must be reduced in accordance with the reduction in pattern size.

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“…The modeling of resist properties using a resist point spread function (PSF) was evaluated by measuring the contrast transfer function. 12 The model explains the resolution limit and corner rounding of patterns. Furthermore, it is important that models of flare and resist blur be capable of predicting the CD variation for FVC with proper mask resizing.…”

Section: Introductionmentioning

confidence: 99%

Flare evaluation for 32-nm half pitch using SFET

Aoyama¹,

Tanaka²,

Kamo³

et al. 2008

SPIE Proceedings

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Flare degrades critical-dimension (CD) control in EUVL, a promising technology for the 32-nm half-pitch node. To deal with flare, high-quality projection optics in the exposure tool and flare variation compensation (FVC) technology with proper mask resizing are needed. Selete has installed a small-field exposure tool (SFET) with the goal of assessing resist performance. Due to the high-quality optics, the SFET allowed us to determine the required flare specification to be 6.1% or 6.6%, as calculated from the residual part of the low-or middle-frequency region, respectively. The flare level was confirmed through experimental results and from calculations using the power spectral density (PSD) obtained from the mirror roughness by the disappearing-resist method. The lithographic performance was evaluated using 32-nm-halfpitch patterns in a new resist. The resist characteristics can be explained by modeling blur as a Gaussian function with a σ of 8.8 nm and using a very accurate CD variation (< ~6 nm) obtained by taking into account the influences of mask CD error and flare on evaluation patterns. Since FVC is needed to obtain flare characteristics that do not degrade the CD, we used the double-exposure method to eliminate the influence of errors, including nonuniform dose distribution and CD mask error. Regardless of whether there was an open area or not, there was no difference in CD as a function of distance up to a distance of 20 µm. In addition, CD degradation was observed at distances not far (< 5 µm) from the open area. In a 60-nm neighborhood of the open area, an 8-nm variation in CD appeared up to the distance at which the CD leveled off. When the influences of resist blur and flare on patterns was taken into account in the calculation, it was found that aerial simulations based on a rigorous 3D model of a mask structure matched the experimental results. These results yield the appropriate mask resizing and the range in which flare has an influence, which is needed for FVC. This research was supported in part by NEDO.

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Modeling of EUV photoresists with a resist point spread function

Cited by 12 publications

References 9 publications

Gradient-based inverse extreme ultraviolet lithography

Gradient-based inverse extreme ultraviolet lithography

Fidelity of rectangular patterns printed with 0.3-NA MET optics

Flare evaluation for 32-nm half pitch using SFET

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