Studying thickness loss in extreme ultraviolet resists due to electron beam exposure using experiment and modeling

J. Photopol. Sci. Technol.

Rebeyev

et al. 2016

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Optimizing the photochemistry of extreme ultraviolet (EUV) photoresists can lead to faster, more efficient resists needed for implementation of EUV lithography into high volume manufacturing. EUV photoresists must simultaneously meet three requirements: improved resolution, low line edge roughness (LER), and high sensitivity. Common EUV photoresists utilize photoacid generators (PAGs) to improve sensitivity, which is affected by many variables, such as developer choice, developer concentration, PAG quantum yield, etc. Isolating one of these parameters will aid in the optimization of sensitivity. Prior work using alternate methods shows it is possible for resists to generate 5-6 acids per absorbed photon. However, the energy of the weakest bond in a typical PAG molecule is on the order of a few electron volts, it should be possible to reach much higher quantum yields with EUV (92 eV) photons. The photochemistry in EUV lithography is believed to be dominated by the energetic electrons generated from ionization. Investigating the acid generation efficiency for a variety of PAGs and concentrations upon electron exposure may lead to the development of resists with higher quantum yield, improving current EUV photoresist platforms. In this study, the reactions between PAG molecules and electrons were measured by using a mass spectrometer to monitor the levels of small molecules produced by PAG decomposition that outgassed from the film.

Section: Methodsmentioning

confidence: 99%

Section: Experimental Designmentioning

confidence: 99%

Section: Concentration Effectsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Acid Generation Efficiency of EUV PAGs via Low Energy Electron Exposure

J. Photopol. Sci. Technol.

Rebeyev

et al. 2016

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“…The distances that electrons travel in a variety of materials has been widely studied [10][11][12]. However, since reaction cross-sections in solid films vs. electron energy, in this energy regime, are not well known, the important question is really, "how far do they go before they react?"…”

Section: Introductionmentioning

confidence: 99%

What We Don’t Know About EUV Exposure Mechanisms

Wisehart

J. Photopol. Sci. Technol.

et al. 2017

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The lithography community has studied EUV photoresists for nearly thirty years. Yet, some of the most basic details of the interaction of EUV photons with photoresists remain poorly understood. In a typical photochemical reaction using long-wavelength light ( = 157-1000 nm), photons create excited states in photoactive compounds, thereby creating known quantities of intermediates and photoproducts at measurable rates.The photochemical reactions occurring during EUV exposure are much more complex and, as yet, not fully explored. The 92 eV EUV photons ionize molecules in the resist, creating holes and free electrons, however, the numbers of these electrons created, their reaction mechanisms, lifetimes and reaction cross-sections are not well known. Here, we will discuss experimental results and provide insight into these poorly understood aspects of EUV exposure mechanisms.

Energy deposition and charging in EUV lithography: Monte Carlo studies

Wiseheart

Extreme Ultraviolet (EUV) Lithography VII

et al. 2016

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EUV photons expose photoresists by complex interactions including photoionization to create primary electrons (~80 eV), and subsequent ionization steps that create secondary electrons (10-60 eV). The mechanisms by which these electrons interact with resist components are key to optimizing the performance of EUV resists and EUV lithography as a whole. As these photoelectrons and secondary electrons are created, they deposit their energy within the resist, creating ionized atoms along the way. Because many photo-and secondary electrons can escape the resist through the surface, resists can become charged. Charging and energy deposition profiles within the resist may play a role in the sensitivity and line-edge roughness of EUV resists.In this paper, we present computational analysis of charging-influenced electron behavior in photoresists using LESiS (Low energy Electron Scattering in Solids), a software developed to understand and model electron-matter interactions. We discuss the implementation of charge and tracking and the model used to influence electron behavior. We also present the potential effects of charging on EUV and electron beam lithography by investigating secondary electron blur in charging and non-charging models.