Extreme-ultraviolet secondary electron blur at the 22-nm half pitch node

Gronheid, Roel; Younkin, Todd R.; Leeson, Michael J.; Fonseca, Carlos; Hooge, Joshua; Nafus, Kathleen; Biafore, John J.; Smith, Mark D.

doi:10.1117/1.3607429

Cited by 8 publications

(2 citation statements)

References 12 publications

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“… 59 Most photoelectrons do not escape from the thin film sample, as their mean free paths are small, at most a few nanometers. 60 − 64 In the present work, we focus on the chemical conversion and on the possible reaction mechanisms. The TinOAc molecule consists of a dicationic core structure, with two hydrogen bonded acetate counteranions.…”

Section: Discussionmentioning

confidence: 99%

XUV Absorption Spectroscopy and Photoconversion of a Tin-Oxo Cage Photoresist

Sadegh,

Evrard,

Kraus

et al. 2024

J. Phys. Chem. C

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Extreme ultraviolet lithography has recently been introduced in high-volume production of integrated circuits for manufacturing the smallest features in high-end computer chips. Hybrid organic/inorganic materials are considered as the next generation of photoresists for this technology, but detailed knowledge about the response of such materials to the ionizing radiation used (13.5 nm, 92 eV) is still scarce. In the present work, we use broadband high-harmonic radiation in the energy range 22−70 eV for absorption spectroscopy and photobleaching (that is, the decrease of absorbance) of thin films of an n-butyltin oxocage, a representative of the class of metal-based EUV photoresist. The shape of the absorption spectrum in the range 22−92 eV matches well with the spectrum predicted using tabulated atomic cross sections. The photobleaching results are consistent with loss of the butyl side groups due to the breaking of Sn−C bonds following photoionization. Bleaching is strongest in the low-energy range (<40 eV), where the absorption is largely due to the carbon atoms in the organic groups. At higher energies (42−70 eV), absorption is dominated by the tin atoms, and since these remain in the film after photoconversion, the absorption change in this region is smaller. It is estimated that after prolonged irradiation (up to ∼3 J cm −2 in the range 22−40 eV) about 70% of the hydrocarbon groups are removed from the film. The rate of bleaching is high at the beginning of exposure, but it rapidly decreases with increasing conversion. We rationalize this using density functional theory calculations: the first Sn−C bonds are efficiently cleaved (quantum yield Φ ≈ 0.9), because the highest occupied molecular orbitals (HOMOs) (from which an electron is removed after photoionization) are located on Sn−C sigma bonds. In the photoproducts, the HOMO is localized on tin atoms that have lost their hydrocarbon group (formally reduced to the Sn(II) oxidation state), and holes formed on those tin atoms lead to less efficient cleavage reactions. Our results reveal the primary reaction steps following excitation with ionizing radiation of tin-oxo cages. Our methodology represents a systematic approach of studying and quantitatively assessing the performance of new photoresists and as such enables the development of future EUV photoresists.

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Section: Discussionmentioning

confidence: 99%

XUV Absorption Spectroscopy and Photoconversion of a Tin-Oxo Cage Photoresist

Sadegh,

Evrard,

Kraus

et al. 2024

J. Phys. Chem. C

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“…Although several attempts have been made on analyzing them, the contribution of each factor is not always clear yet. [6][7][8][9][10][11][12][13][14] Conventionally, lithographic processes have been understood as interactions between patterned electromagnetic fields and resist materials as an inelastic body, and both of which are dealt with as continuous properties. This assumption is no more appropriate as pattern sizes approach to the average distances between photon-absorption events (as in EUV) or between chemical species interacting with the photons such as photoacid generator (PAG) in chemically amplified resist (CAR).…”

Section: Introductionmentioning

confidence: 99%

Cascade and cluster of correlated reactions as causes of stochastic defects in extreme ultraviolet lithography

Fukuda

2020

J. Micro/Nanolith. MEMS MOEMS

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Background: Stochastic defects are becoming major concern in the future extreme ultraviolet (EUV) lithography as their probability P d exponentially increases with decreasing feature size and is highly sensitive to variations in process/mask conditions. Photon shot-noise and discrete/ probabilistic nature of materials have been blamed as their causes. Aim: We introduce models for relating P d to photon and resist statistics under various exposures and material conditions and analyze their impact in future EUV lithography. Approach: Three-dimensional reaction distribution is calculated by a fully coupled Monte Carlo simulation including discrete photon, photoelectron scattering, and resist stochastics. Then probability models predict P d from statistical data extracted from Monte Carlo results. Results: Stochastic defect generation is enhanced by cascade and/or cluster of correlated reactions among nearby polymers/molecules due to secondary electrons (SE)/acid diffusion and SEs generated along scattered photoelectron trajectories. P d decreases with increasing reaction density, suppressing effective image blur, and introducing quenchers, where reaction density is limited by SE, photoacid generator, and reaction site. Defect probability increases with decreasing target size for the same k1-factor, while strongly dependent on image slope and defocus. Conclusions: Our analyses suggest that applying EUV lithography to smaller target requires careful material choice, extremely precise process control, and further EUV power enhancement.

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Extreme Ultraviolet-Printability and Mechanistic Studies of Engineered Hydrogen Silsesquioxane Photoresist Systems

Rathore

Pollentier

Cipriani

et al. 2021

ACS Appl. Polym. Mater.

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Hydrogen Silsesquioxane (HSQ) photoresist has shown extremely high-resolution performance for Electron-Beam Lithography (EBL) and Interference Lithography (IL) and can be a potential photoresist candidate for Extreme Ultraviolet Lithography (EUVL). To optimize this system for sub-10 nm patterning, it is important to understand the EUV and electron-induced chemistry underpinning the functionality of this resist material. Here we present a EUVprintability study on HSQ photoresist at a resolution of 16 and 22 nm combined with a mechanistic study on EUV and electron-induced desorption of HSQ film. Firstly, patterning results showed that the simple HSQ cages require a high EUV-dose and an aggressive developer to print dense features. EUV-and electron-induced desorption experiments revealed that hydrogen and silane are the dominant species fragmented from HSQ, indicating dehydrogenation and redistribution pathways as the crosslinking mechanism. Quantum chemical calculations suggested that the Neutral Dissociation (ND) is the dominant mechanism in HSQ cross-linking at low energies, i.e., below its ionization threshold, whereas Dissociative Ionization (DI) contributes significantly at higher energies. A distinct structure is observed at about 8 eV and a clear peak at about 11 eV indicating a significant contribution through Dissociative electron attachment (DEA) at these energies. Based on these results, an engineered HSQ system is designed by adding silanol or carbinol (R-CH3OH)-groups to the partially crosslinked HSQ-cages to increase its Tetramethylammonium hydroxide (TMAH)-developer and EUV-sensitivity. Finally, 2.38% v/v TMAH is used to develop a 16 nm printed dense line-space (L/S) with a line-edge-roughness (LER) of 6.4 nm but requiring an EUV-dose of over 100 mJ/cm 2 .

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Extreme-ultraviolet secondary electron blur at the 22-nm half pitch node

Cited by 8 publications

References 12 publications

XUV Absorption Spectroscopy and Photoconversion of a Tin-Oxo Cage Photoresist

XUV Absorption Spectroscopy and Photoconversion of a Tin-Oxo Cage Photoresist

Cascade and cluster of correlated reactions as causes of stochastic defects in extreme ultraviolet lithography

Extreme Ultraviolet-Printability and Mechanistic Studies of Engineered Hydrogen Silsesquioxane Photoresist Systems

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