Electron Penetration Depths in EUV Photoresists

Torok, Justin; Srivats, Bharath; Memon, Shahid Hussain; Herbol, Henry C.; Schad, Jonathon; Das, Sanjana; Ocola, Leonidas E.; Denbeaux, Greg; Brainard, Robert L.

doi:10.2494/photopolymer.27.611

Cited by 18 publications

(28 citation statements)

References 3 publications

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“…3) happen to outgas benzene as a possible side product during acid generation events. Benzene is volatile enough to diffuse through and out of a 60 nm films [3,4,6,7]. This makes these PAGs ideal candidates to measure electron induced acid generation efficiency by monitoring benzene outgassing and for comparing the results to EUV film quantum yields.…”

Section: Methodsmentioning

confidence: 99%

“…It is well known that when a photoresist is exposed to EUV photons that molecules will outgas [1,[4][5][6][7]. For select PAGs, some of these outgassing molecules correlate to an acid generation event (Fig.…”

Section: Experimental Designmentioning

confidence: 99%

“…To observe the acid generation efficiency as a function of PAG concentration for various PAG molecules, the following experiment was performed in our Electron Resist Interaction Chamber (ERIC), which is a vacuum chamber equipped with a Kimball Physics EFG-7 electron gun and an Extrel MAX300 quadrupole mass spectrometer [3][4][5][6][7]. In ERIC, a photoresist is exposed with a normal incident electron beam at 80 eV [6,7].…”

Section: Experimental Designmentioning

confidence: 99%

“…The PAG is a photon-or electron-sensitive molecule that is capable of producing an acid which catalyzes numerous chemical transformations in the surrounding resist [1][2][3][4][5][6][7]. Further improvement of chemically amplified photoresists for use with EUV is crucial to meet the lithographic requirements of the microelectronics industry, or an innovative nonchemically amplified resist must be developed to satisfy this need.…”

Section: Introductionmentioning

confidence: 99%

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Acid Generation Efficiency of EUV PAGs via Low Energy Electron Exposure

Grzeskowiak

Narasimhan

Rebeyev

et al. 2016

J. Photopol. Sci. Technol.

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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.

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Section: Methodsmentioning

confidence: 99%

Section: Experimental Designmentioning

confidence: 99%

Section: Experimental Designmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Acid Generation Efficiency of EUV PAGs via Low Energy Electron Exposure

Grzeskowiak

Narasimhan

Rebeyev

et al. 2016

J. Photopol. Sci. Technol.

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“…Detector Upon EUV absorption photoelectrons as well as secondary electrons are generated in the resist film ( Figure 1A). [2,3]. Depending on the energy of these electrons, they may have a longer inelastic mean free path ( fig.…”

Section: Introductionmentioning

confidence: 97%

Low-energy electron (0-100eV) interaction with resists using LEEM

et al. 2015

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Extreme Ultra Violet (EUV) lithography is a next generation lithographic technique using 13.5 nm wavelength light (91.7eV photon energy) to define sub-20 nm features. This high energy radiation generates lower energy electrons (LEEs) after being absorbed. The mean free path of LEEs increases rapidly below ca. 30 eV allowing them to migrate several nanometers from their point of origin. As LEEs can still have sufficient energy to react with the surrounding resist, this may give rise to pattern blurring, posing a challenge for sub 10 nm features. Here, we introduce Low Energy Electron Microscopy (LEEM) as an extremely useful technique to investigate the interactions of LEEs with EUV resists. Using LEEM we can expose the resist with precise electron energies and doses. We also report the initial results of LEE exposures on poly(methyl methacrylate) PMMA. We have studied the LEE-PMMA interaction depth as a function of electron energy; a distinct exposure threshold is found at ~15 eV, below which the resist responds only very weakly to electron exposure. Figure 1 (A) Line edge blur caused by secondary electrons generated upon 91.7 eV photon absorption. The inelastic mean free path of the electrons increases rapidly at lower energies as shown in (B). This can influence the blur as well as the electron penetration depth during EUV exposure.

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