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

Severi, Joren; Simone, Danilo De; Gendt, Stefan De

doi:10.3390/polym12122971

Cited by 8 publications

(17 citation statements)

References 13 publications

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“…This layer was subsequently baked at the vendor recommended setting. On top of this underlayer, a state-of-the-art CAR was spin coated at the desired nominal FT (10,15,20,25, or 30 nm) and baked at vendor recommended settings (130°C 60 s). An FT check was performed using ellipsometry to confirm these nominal values.…”

Section: Euv Exposurementioning

confidence: 99%

“…In addition, when reducing the resist FT, the resist-underlayer interaction becomes more dominant, which may affect resist roughness as well. 10 These observations suggest that a threshold SNR should be defined above which the real uLWR value is given, and below which the uLWR value is not reliable anymore. This also implies that the resist patterning performance on two different underlayers is best compared when estimated at the same SNR rather than the same number of frames as is standard.…”

Section: Snr and Frame Variationmentioning

confidence: 99%

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Chemically amplified resist CDSEM metrology exploration for high NA EUV lithography

Severi

Lorusso

Simone

et al. 2022

J. Micro/Nanopattern. Mats. Metro.

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Background: The chemically amplified resist (CAR) has been the workhorse of lithography for the past few decades. During the evolution of projection lithography to extreme ultraviolet lithography (EUVL), a continuous reduction in feature size is observed. Also, a reduction in resist film thickness (FT) is required to prevent large aspect ratios that lead to pattern collapse. A further reduction in resist FT, into an ultrathin film regime (<30 nm resist FT), is expected when advancing to high NA EUVL. This brings along associated challenges with (1) resist critical dimension scanning electron microscope (CDSEM) metrology and (2) resist patterning performance.Aim: Assessment of metrology challenges and patterning limits of a CAR working in this ultrathin film regime. Deconvoluting the metrology and patterning effect on the determination of the unbiased line width roughness (uLWR).Approach: Patterning a CAR at different nominal resist FTs on two different underlayers to quantify the changes in CDSEM image quality and resist patterning performance with the resulting uLWR changes. Results:The CDSEM image signal-to-noise ratio (SNR) depends on resist FT and the underlayer. The uLWR increases with a reduction in resist FT but scales differently on the two underlayers.Conclusions: A relationship between CDSEM image SNR and uLWR is found. The SNR and uLWR scaling difference on the two underlayers, as well as the uLWR dependency on SNR was determined to be a metrology effect. The general uLWR increase for a reduced resist FT was determined to be a patterning effect.

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Section: Euv Exposurementioning

confidence: 99%

Section: Snr and Frame Variationmentioning

confidence: 99%

Chemically amplified resist CDSEM metrology exploration for high NA EUV lithography

Severi

Lorusso

Simone

et al. 2022

J. Micro/Nanopattern. Mats. Metro.

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“…Resist materials, including polymers and PAG, were provided by Fujifilm and used as received. Polymers were chosen to explore a range of protecting groups, surface terminations, and glass transition temperatures . Substrates consisted of 300 mm silicon wafers with native oxide (referred to throughout the text as SiO 2 wafers).…”

Section: Methodsmentioning

confidence: 99%

“…5,10,11 Current photoresists are typically polymer-based chemically amplified resists (CARs) 12 with a photoacid generator (PAG) to catalyze deprotection of the polymers after EUV exposure. 3,13 While CARs have already demonstrated promising results for 12 nm half-pitch patterns and potential for the 7 nm node, 14 they suffer from low etch resistance and risk of pattern collapse. 15,16 Thinner resist layers mitigate pattern collapse 17 but typically result in poor etch selectivity to underlying layers, especially when the resist is <50 nm thick.…”

Section: ■ Introductionmentioning

confidence: 99%

Enhancing Performance and Function of Polymethacrylate Extreme Ultraviolet Resists Using Area-Selective Deposition

et al. 2023

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Extreme ultraviolet (EUV) lithography is a critical enabler in nextgeneration technology, although the low etch resistance of conventional organic EUV resists results in low resolution pattern transfer, particularly for smaller features. In this work, we integrate area-selective deposition (ASD), a bottom-up nanopatterning technique, with EUV resists of industrially relevant thicknesses (<50 nm thick) to form resist hardening or tone inverting layers for improved resolution. We utilize TiO 2 ASD via atomic layer deposition on 25−35 nm thin photosensitive polymethacrylate-based EUV materials. By tuning the polymer structure and functionality, we enable different scenarios for selective deposition on top of the resist, infiltrated into the bulk resist, or selective to the resist. We find that a cyclohexyl protecting group causes TiO 2 inhibition, thus showing promise for tone inversion applications with oxide underlayers. In contrast, resist materials containing a tert-butyl protecting group are good candidates for resist hardening because they enable TiO 2 deposition on both EUV exposed and unexposed polymers. Furthermore, we report the integration of a dimethylamino-trimethylsilane inhibitor with the resists to inhibit TiO 2 surface nucleation and facilitate subsurface diffusion, thus further broadening potential applications. The results described here establish an important baseline for utilizing ASD on various organic resists to achieve tone inversion or resist hardening and hence improve EUV pattern resolution.

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“…Due to the necessary continuous downscaling of resist FT, the interfacial interaction between resist and underlayer becomes increasingly dominant. 4 These interactions can influence material behavior, which in turn makes the resist design and optimization that enables a good patterning performance challenging. Changes related to material behavior that have been reported include changes in dose-to-size, in resist nanopattern line profile and number of nanofailures, and in chemical homogeneity of the resist additives that can cause pattern degradation.…”

Section: Introductionmentioning

confidence: 99%

Resist reflow methodology development to investigate interfacial interactions

Severi

Chan

Simone

et al. 2022

J. Micro/Nanopattern. Mats. Metro.

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Background: To enable printing of smaller feature sizes, lithography has progressed into the extreme ultraviolet lithography (EUVL) regime. Alongside the wavelength scaling, a reduction in resist film thickness (FT) is observed to avoid large aspect ratios that would lead to pattern collapse. The further progression to high numerical aperture (NA) EUVL will require a further reduction in resist FT moving toward an ultra-thin film regime (<30-nm resist FT). This reduction in resist FT will make the interfacial interactions between resist and underlayer more dominant, potentially influencing material behavior and making resist design challenging.Aim: We assess a reflow process as a means to investigate interfacial effects and in this way deconvolute the correlation between resist line volume, interfacial effects, and the reflow temperature (T R ), defined as the temperature at which the resist line starts broadening, which is indicative of the glass transition temperature (T g ).Approach: We pattern a model EUV chemically amplified resist at different nominal resist FTs and different critical dimensions (CDs) and half-pitch (HP) combinations to quantify changes in the T R . Results:The T R increases with the inverse of the CD, as well as the inverse of the resist FT. Moreover, the T R also scales with the area ratio (the ratio of the area in contact with the ambient to the area in contact with the underlayer).Conclusions: A linear relationship between T R and its volume factor (CD × FT) normalized for the area ratio (area in contact with the ambient to the area in contact with the underlayer) is found, revealing a combined dependency on line volume and interfacial interactions. This opens the potential for the use of the reflow methodology in investigating interfacial interactions.

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

Cited by 8 publications

References 13 publications

Chemically amplified resist CDSEM metrology exploration for high NA EUV lithography

Chemically amplified resist CDSEM metrology exploration for high NA EUV lithography

Enhancing Performance and Function of Polymethacrylate Extreme Ultraviolet Resists Using Area-Selective Deposition

Resist reflow methodology development to investigate interfacial interactions

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