Conventionally, the resolution limit of a lithography system with wavelength l and numerical aperture NA is given by half-pitch = 0.25 wavelength/NA. With the use of EUV lithography, however, electron blur needs to be added [1]. The impact of this blur is to reduce the contrast [2]. Blur reduces the modulation amplitude by a factor… Read More
Author: Fred Chen
Stochastic Effects Blur the Resolution Limit of EUV Lithography
Can LELE Multipatterning Help Against EUV Stochastics?
Previously, I had indicated how detrimental stochastic effects at pitches below 50 nm should lead to reconsidering the practical resolution limit for EUV lithography [1]. This is no exaggeration, as stochastic effects have been observed for 24 nm half-pitch several years ago [2,3]. This then leads to the question of whether … Read More
Stochastic Pupil Fill in EUV Lithography
Pupil fill tradeoff again
EUV lithography continues to be plagued by its stochastic nature.
This stochastic nature is most clearly portrayed by the random fluctuation of the absorbed photon number at a given location. For example, consider an absorbed dose of 10 mJ/cm2 amounts to 6.8 photons of energy 92 eV absorbed in a square … Read More
Application-Specific Lithography: Patterning 5nm 5.5-Track Metal by DUV
At IEDM 2019, TSMC revealed two versions of 5nm standard cell layouts: a 5.5-track DUV-patterned version and a 6-track EUV-patterned version [1]. Although the metal pitches were not explicitly stated, later analyses of a 5nm product, namely, Apple’s A15 Bionic chip, revealed a cell height of 210 nm [2]. For the 6-track … Read More
Why NA is Not Relevant to Resolution in EUV Lithography
The latest significant development in EUV lithography technology is the arrival of High-NA systems. Theoretically, by increasing the numerical aperture, or NA, from 0.33 to 0.55, the absolute minimum half-pitch is reduced by 40%, from 10 nm to 6 nm. However, for EUV systems, we need to recognize that the EUV light (consisting … Read More
Huawei’s and SMIC’s Requirement for 5nm Production: Improving Multipatterning Productivity
There has been much interest in Huawei’s and SMIC’s plans for 5nm production in the near future. Since there is no use of EUV in China, immersion DUV lithography (with a 76 nm pitch resolution) is expected to be used along with pitch quartering to achieve pitches in the 20-30 nm range expected for the 5nm and 3nm nodes [1].… Read More
Measuring Local EUV Resist Blur with Machine Learning
Resist blur remains a topic that is relatively unexplored in lithography. Blur has the effect of reducing the difference between the maximum and minimum doses in the local region containing the feature. Blur is particularly important for EUV lithography since EUV lithography is prone to stochastic fluctuations and also driven… Read More
Pinning Down an EUV Resist’s Resolution vs. Throughput
The majority of EUV production is on 5nm and 3nm node, implemented by late 2022. Metal oxide resists have not been brought into volume production yet [1,2], meaning that only organic chemically amplified resists (CARs) have been used instead until now. These resists have a typical absorption coefficient of 5/um [3,4], which means
Application-Specific Lithography: Avoiding Stochastic Defects and Image Imbalance in 6-Track Cells
The discussion of any particular lithographic application often refers to imaging a single pitch, e.g., 30 nm pitch for a 5nm-family track metal scenario. However, it is always necessary to confirm the selected patterning techniques on the actual use case. The 7nm, 5nm, or 3nm 6-track cell has four minimum pitch tracks, flanked… Read More
Non-EUV Exposures in EUV Lithography Systems Provide the Floor for Stochastic Defects in EUV Lithography
EUV lithography is a complicated process with many factors affecting the production of the final image. The EUV light itself doesn’t directly generate the images, but acts through secondary electrons which are released as a result of ionization by incoming EUV photons. Consequently, we need to be aware of the fluctuations… Read More
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