Abstract
Background: Hybrid inorganic-organic materials have emerged as promising candidates for EUV resists. However, knowledge on their stability when deposited as thin films is essential for their performance in EUV lithography. Aim: We investigate whether the molecular structure of Zn-based metal oxoclusters is preserved upon thin film deposition and study aging processes of the thin film under different atmospheres, since these chemical changes affect the solubility properties of the material. Approach: A hybrid cluster that combines the high EUV photon absorption cross-sections of zinc and fluorine with the reactivity of methacrylate organic ligands was synthesized. The structural modifications upon thin film formation and after aging in air, nitrogen, and vacuum were studied using a combination of spectroscopic techniques. Preliminary studies on the lithographic performance of this material were performed by EUV interference lithography. Results: The Zn-based compound undergoes structural rearrangements upon thin film deposition as compared to the bulk material. The thin films degrade in air over 24 h, yet they are found to be stable for the duration and conditions of the lithography process and show high sensitivity. Conclusions: The easy dissociation of the ligands might facilitate hydrolysis and rearrangements after spin-coating, which could affect the reproducibility of EUV lithography.
Highlights
IntroductionPhotoresists materials are crucial for the semiconductor industry since they mediate the transfer of information from an optically projected pattern to a substrate where the actual circuitry of processor chips and memory devices are built.[1,2] To keep following Moore’s law, which requires the fabrication of patterns with ever smaller critical dimensions, Extreme Ultraviolet (EUV) lithography, using radiation of 13.5 nm wavelength, is seen as the most suitable successor to the state-of-the-art ArF photolithography (193 nm).[3,4] this transition has led to critical challenges for the development of suitable EUV photoresists.[5,6,7,8,9] For adequate lithography performance, resists should simultaneously satisfy the industrial requirements of resolution (
The starting material comprises a core of four Zn atoms bridged by one O atom (μ4-O) and six TFA ligands that bridge two Zn atoms through the carboxylate group.[32,33]. Since this reaction proceeds in equilibrium due to competitive binding of the two types of carboxylate ligands, methacrylic acid (MAA) is added in excess to favor the shift of the equilibrium to the right side of the chemical equation and have a high abundance of MA ligands in the shell of the synthesized product Zn(MA)(TFA)
Deposition of the material as thin films changes the solubility properties compared to the bulk material, presumably due to the loss of extra nonbonded acids that are occluded in the original crystalline forms and/or rearrangements of the carboxylate ligands
Summary
Photoresists materials are crucial for the semiconductor industry since they mediate the transfer of information from an optically projected pattern to a substrate where the actual circuitry of processor chips and memory devices are built.[1,2] To keep following Moore’s law, which requires the fabrication of patterns with ever smaller critical dimensions, EUV lithography, using radiation of 13.5 nm wavelength, is seen as the most suitable successor to the state-of-the-art ArF photolithography (193 nm).[3,4] this transition has led to critical challenges for the development of suitable EUV photoresists.[5,6,7,8,9] For adequate lithography performance, resists should simultaneously satisfy the industrial requirements of resolution (
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