Post-Exposure Bake Temperature Considerations for High Activation Energy Resist Systems.

Malik, Sanjay; Eisele, Jeff; Whewell, Allyn; Ferreira, Lawrence; Holt, T.; Bowden, M. J.

doi:10.2494/photopolymer.13.513

Cited by 7 publications

(9 citation statements)

References 4 publications

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“…The glass transition temperature (T g ) of a chemically amplified resist (CAR) is an important property that relates to the post-exposure bake (PEB) temperature and influences acid diffusion, and thus also the resulting critical dimension (CD) and line-edge roughness (LER) of the resist line. Moreover, it influences the propensity to form defects (e.g., bridges or breaks) as well [ 9 ]. While it is apparent that some inherent characteristics of a polymer such as intramolecular and intermolecular interactions can influence the T g , it was already proven that the T g depends on film thickness and interfacial interactions [ 10 ].…”

Section: Introductionmentioning

confidence: 99%

Dielectric Response Spectroscopy as Means to Investigate Interfacial Effects for Ultra-Thin Film Polymer-Based High NA EUV Lithography

2020

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Extreme ultra-violet lithography (EUVL) is the leading-edge technology to produce advanced nanoelectronics. The further development of EUVL is heavily based on implementing the so-called high numerical aperture (NA) EUVL, which will enable even smaller pitches up to 8 nm half pitch (HP). In anticipation of this high NA technology, it is crucial to assess the readiness of the current resist materials for the high NA regime to comply with the demanding requirements of resolution, line-edge roughness, and sensitivity (RLS). The achievable tighter pitches require lower film thicknesses for both resist and underlying transfer layers. A concern that is tied to the thinning down is the potential change in resist properties and behavior due to the interaction with the underlayer. To increase the fundamental understanding of ultra-thin films for high NA EUVL, a method to investigate the interplay of reduced film thickness and different patterning-relevant underlayers is developed by looking at the glass transition temperature (Tg) of polymer-based resists. To minimize the ambiguity of the results due to resist additives (i.e., photoacid generator (PAG) and quencher), it was opted to move forward with polymer-only samples, the main component of the resist, at this stage of the investigation. By using dielectric response spectroscopy, the results obtained show that changing the protection group of the polymer, as well as altering the polymer film thickness impacts the dynamics of the polymer mobility, which can be assessed through the Tg of the system. Unexpectedly, changing the underlayer did not result in a clear change in the polymer mobility at the tested film thicknesses.

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Section: Introductionmentioning

confidence: 99%

Dielectric Response Spectroscopy as Means to Investigate Interfacial Effects for Ultra-Thin Film Polymer-Based High NA EUV Lithography

2020

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“…The rate of ester cleavage was characterized by constructing dissolution curves (Figure 3a), in which the remaining polymer film thickness after development was observed as a function of the initial acid concentration generated by a given UV exposure dose (see Supporting Information). The dose required to remove the entire polymer film (E 0 ) is a function of both heating time and temperature; 19 representative data are shown for both 60 s hot-plate and 500 μs laser heating at various temperatures. We constructed isotherms of E 0 versus heating time (Figure 3b) to compare the ester cleavage behavior as a function of temperature and reaction time.…”

Section: Resultsmentioning

confidence: 99%

Laser-Induced Sub-millisecond Heating Reveals Distinct Tertiary Ester Cleavage Reaction Pathways in a Photolithographic Resist Polymer

et al. 2014

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Acid-catalyzed, thermally activated ester cleavage reactions are critical for lithographic patterning processes used in the semiconductor industry. The rates of these high-temperature reactions within polymer thin films are difficult to characterize because of the thermal instability of many polymers and a lack of temperature-resolved measurement techniques. Here we introduce the use of transient laser irradiation to heat a methyladamantane-protected acrylate copolymer to 600 °C in less than a millisecond. These conditions mediate the removal of the protecting groups and enable accurate kinetic measurements. At sub-millisecond exposure to high temperatures (∼600 °C), the rate of the ester cleavage reaction exhibits the expected first-order dependence on acid concentration. In contrast, the reaction exhibits more complex kinetics when the polymer film is heated to lower temperatures (115 °C) on a conventional hot-plate. We identify distinct methyladamantane-derived deprotection products under the high- and low-temperature conditions that are consistent with the observed rate differences. The acid-catalyzed dimerization of 1-methyleneadamantane occurs at low temperature, which reduces the acid concentration available for the ester cleavage. This dimerization reaction is minimized during transient laser-induced heating because bimolecular reactions are disfavored under these conditions. We constructed a mathematical model based on these observations that accounts for the competition for the catalyst between the dimerization and ester cleavage processes. This laser-induced, sub-millisecond heating technique provides a means to probe and model temperature and time regimes of thermally activated reactions in polymer films, and these regimes exhibit distinct and advantageous reaction pathways that will inform future advances in high-performance photolithography.

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“…As both processes are expected to be thermally activated, differences in the activation energies may permit optimization of PEB conditions in a trade-off between temperature and time 4,5 . The minimum time required at a given PEB temperature is inversely related to the deprotection rate while the acid diffusion distance (resolution loss and LER) is proportional to the square root of the diffusivity.…”

Section: Introductionmentioning

confidence: 99%

“…PEB is conventionally achieved by heating the sample on a hot plate at 90-150°C for 30-120 seconds. Excessive PEB time and/or temperature leads to diffusion of photoacids with negative consequences for resolution and line edge roughness (LER) 4,5 .…”

Section: Introductionmentioning

confidence: 99%

Deprotection reaction kinetics in chemically amplified photoresists determined by sub-millisecond post exposure bake

2012

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Chemically amplified photoresists require a post exposure bake (PEB) to induce deprotection using a UV generated acid-catalyst. While reaction pathways for deprotection have been proposed, key challenges remain in modeling the reaction kinetics. In this work, we used a scanning line-focused laser beam as an alternate PEB method, to quantify the deprotection reaction kinetics of an ESCAP-type and a 193 nm model resist system at high temperatures in millisecond time frames. Results were compared with conventional PEB at 115°C for seconds time frames. Results show that the deprotection kinetics follow simple first-order reaction models only under laser PEB conditions, with more complex kinetics observed under hot plate PEB. FT-IR and NMR spectroscopies were used to characterize the reaction byproducts. Results suggest potential differences in deprotection mechanisms between the two PEB temperature and time regimes. The deprotection behavior obtained using this l-PEB technique enables a deeper understanding of the reaction kinetics of photoresists, critical for current DUV and future EUV technologies.

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Post-Exposure Bake Temperature Considerations for High Activation Energy Resist Systems.

Cited by 7 publications

References 4 publications

Dielectric Response Spectroscopy as Means to Investigate Interfacial Effects for Ultra-Thin Film Polymer-Based High NA EUV Lithography

Dielectric Response Spectroscopy as Means to Investigate Interfacial Effects for Ultra-Thin Film Polymer-Based High NA EUV Lithography

Laser-Induced Sub-millisecond Heating Reveals Distinct Tertiary Ester Cleavage Reaction Pathways in a Photolithographic Resist Polymer

Deprotection reaction kinetics in chemically amplified photoresists determined by sub-millisecond post exposure bake

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