Organometallic and coordinative photoresist materials for EUV lithography and related photolytic mechanisms

Lim, Gi Hyun; Lee, K. Y.; Choi, Sung-Eun; Yoon, Ho‐Geun

doi:10.1016/j.ccr.2023.215307

Cited by 27 publications

(14 citation statements)

References 52 publications

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“…Other disadvantages of organic-based materials are that their absorption cross sections at the EUV wavelength are small, − and their etch resistance in thin films is low . For these reasons, research has been initiated in hybrid organic/inorganic molecular materials, which combine strong absorption, high etch resistance, and small size (not limiting resolution). − …”

Section: Introductionmentioning

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: Introductionmentioning

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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“…The use of photoacids helps avoid the problem of photon shot noise, enabling effective utilization even at lower doses . However, CAR photoresists have limitations in achieving nanopatterning with EUV lithography. − Among others, (i) due to the large diameter of free gyration of polymer (around 2–10 nm) − and (ii) acid diffusion, sub-20 nm patterning with sharp contrast is difficult to achieve. (iii) During the postexposure baking (PEB) step before the developing process, acid diffusion mechanisms are accelerated and cause bridging or pinching failure patterns, thereby increasing LER .…”

Section: Introductionmentioning

confidence: 99%

Multinuclear Tin-Based Macrocyclic Organometallic Resist for EUV Photolithography

Lim,

Lee,

Koh

et al. 2024

ACS Mater. Au

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We report a new photoresist based on a multinuclear tinbased macrocyclic complex and its performance for extreme UV (EUV) photolithography. The new photoresist has a trinuclear macrocyclic structure containing three salicylhydroxamic acid ligands and six Sn−CH 3 bonds, which was confirmed by multinuclear nuclear magnetic resonance (NMR) and FT-IR spectroscopies and single-crystal X-ray diffraction study. The resist exhibited good humidity, air, and thermal stabilities, while showing good photochemical reactivity. Photochemical crosslinking of the resist was confirmed by X-ray photoelectron and solid-state NMR spectroscopic analyses. EUV photolithography with the 44 nmthick film on a silicon wafer revealed a line-edge-roughness (LER) of 1.1 nm in a 20 nm half-pitch pattern. The Z-factor, a metric that gauges the performance of photoresists by considering the tradeoff between resolution, LER, and sensitivity (RLS), was estimated to be 1.28 × 10 −8 mJ•nm 3 , indicating its great performance compared to the EUV photoresists reported in the literature.

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“…13 In addition to EUV absorption, it is desirable to devise effective reaction pathways and incorporate them into the chemical mechanisms of the resist under EUV radiation. 14,15 In this study, our team proposes a strategy to expedite solubility changes within the exposure area, aiming to enhance sensitivity characteristics. Previous research indicates that introducing vinyl functional groups into an underlayer induces solubility changes at lower exposure doses.…”

Section: Introductionmentioning

confidence: 99%

Approach for enhancing sensitivity of tin-oxo cluster resist for high NA extreme UV lithography

Ku,

Kim,

Kim

et al. 2024

Advances in Patterning Materials and Processes XLI

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High numerical aperture (NA) EUV lithography is considered as the most-promising candidate for next generation lithography protocol that will play a crucial role in meeting the demand on the enhanced semiconductor performance and productivity. While this technology enables the fabrication of sub-10 nm patterns, the increased NA has posed challenges, such as reduced depth of focus and narrower process margins. To overcome these hurdles, it is essential to apply thinner resist films while ensuring that the resulting small patterns maintain sufficient physical and chemical durability. Moreover, considering that thinner films absorb fewer photons, the resist molecular structure should be designed to compensate sensitivity burdens.Here, an approach has been proposed to enhance sensitivity by accelerating the solubility change of a well-known tinbased nanocluster resist. To accomplish this goal, it is important to increase not only the number of secondary electrons but also reaction sites and promote radical-based chemical reactions. We aimed at experimentally validating this concept by utilizing elements with high EUV absorbance and highly reactive functional groups with tin radicals. As a model resist, we chose a tin-oxo cage material consisting of a divalent cation containing 12 tin atoms and two counter anions. Our findings indicate that the introduction of unsaturated groups capable of building bridging bonds with radicals leads to fast solubility change at a lower exposure dose, thus enhancing sensitivity. This research offers a promising direction for the development of resists tailored for High NA EUV lithography.

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Organometallic and coordinative photoresist materials for EUV lithography and related photolytic mechanisms

Cited by 27 publications

References 52 publications

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

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

Multinuclear Tin-Based Macrocyclic Organometallic Resist for EUV Photolithography

Approach for enhancing sensitivity of tin-oxo cluster resist for high NA extreme UV lithography

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