• Chinese Journal of Lasers
  • Vol. 51, Issue 18, 1801002 (2024)
Huifang Zhao, Zuohu Zhou, and Lei Zhang*
Author Affiliations
  • Institute of Modern Optics, Nankai University, Tianjin 300350, China
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    DOI: 10.3788/CJL241047 Cite this Article Set citation alerts
    Huifang Zhao, Zuohu Zhou, Lei Zhang. Research Progress and Prospects of Extreme Ultraviolet Photoresists[J]. Chinese Journal of Lasers, 2024, 51(18): 1801002 Copy Citation Text show less

    Abstract

    Significance

    Photoresist is a photosensitive material that exhibits changes in solubility upon exposure to light or radiation. Moreover, photoresist plays a key role in micro pattern processing in the field of microelectronics, which is characterized by high technological content, complex production processes, and long research and development cycles. Photoresist is widely used in flat displays, printed circuit boards, integrated circuits, microelectromechanical systems, and other fields. In the integrated circuit industry, the continuous development of photoresist materials provides an important guarantee for the continuation of Moore’s Law, and the continuous advancement of chip nodes puts higher requirements on the resolution of photoresist materials. Extreme ultraviolet (EUV) lithography is currently the most advanced chip manufacturing technology, and it is becoming increasingly prominent. Hence, the accompanying EUV photoresist is also receiving increased attention.

    Progress

    For an extreme ultraviolet light source, the photon corresponding to the wavelength of 13.5 nm for the radiation light has an energy of 92 eV, which is much higher than the ionization potential of the component atoms of the photoresist material. This leads to a significant difference in the reaction mechanism of extreme ultraviolet photoresist, compared with the previous generation of photoresists. Moreover, the glass transition temperature, thermal decomposition temperature, film-forming properties, extinction coefficient, refractive index, particle content, metal impurity content, and other parameters of the material also impact the performance of EUV photoresists. These factors make the development of extreme ultraviolet photoresists extremely challenging. To better promote the development of such key materials for integrated circuits, this study summarizes and discusses the latest domestic and international research progress on extreme ultraviolet photoresists. First, the research background and challenges faced by extreme ultraviolet photoresists are introduced. Then, a classification introduction is made from the perspectives of non-metallic and metal-based extreme ultraviolet photoresist materials. Four typical non-metallic EUV photoresists are presented: chemical amplification (Fig. 1), non-chemical amplification (Fig. 3), molecular glass (Fig. 7), and hydrogen sesquioxan (Fig. 9). Three metal-based EUV photoresists are presented: small metal-organic molecules (Fig. 10), metal oxides (Fig. 12), and metal oxo clusters (Fig. 13). A comprehensive summary and outlook are provided for the current technological route of metal oxide cluster type EUV photoresists, which has received widespread attention from both academia and industry. Overall, traditional organic photoresists, as represented by chemically amplified photoresists, are widely used in deep ultraviolet (DUV) and previous lithography technologies, and they show potential in EUV lithography applications. However, their inherent weak EUV photon absorption gives them a natural disadvantage in terms of EUV sensitivity. Correspondingly, introducing metal elements with high EUV photon absorption cross-sections can significantly improve sensitivity and reduce the output power requirements of EUV lithography machines, which are already extremely technologically complex. In addition, metal based EUV photoresists can enhance the etching resistance under low film thickness and thin lines, which is conducive to pattern transfer in advanced manufacturing processes.

    Conclusions and Prospects

    Conclusions and Prospects With the continuous development of EUV lithography technology, higher requirements are being put forward for EUV photoresists. In this context, various non-metallic and metal-based EUV lithography materials are reviewed, focusing on the latest research progress domestically and abroad. The results of a comparison of the lithographic performances of typical non-metallic and metal-based EUV photoresists indicate that metal-based EUV photoresists, especially metal oxo clusters, may become the mainstream technology route for the next generation of high-performance EUV photoresists. Research in this field has made good progress in recent years. However, considering the rich diversity and huge amount of known metal oxo clusters, research into their applications in EUV lithography is relatively limited, and the mechanism of solubility changes caused by photolithography reactions is still unclear. Therefore, it is crucial to develop new metal oxo cluster lithography materials using molecular design strategies. To achieve this goal, it is necessary to understand the inherent relationship between photolithography performance and the structures of metal oxo clusters. Therefore, lithography function-oriented structural design and the precise fabrication of metal oxo clusters are expected to greatly promote the development of EUV photoresists. In this process, the effects of metal cluster nuclei, coordination bonds between metals and ligands, and peripheral ligand layers on the performance of EUV lithography should be considered comprehensively.

    Huifang Zhao, Zuohu Zhou, Lei Zhang. Research Progress and Prospects of Extreme Ultraviolet Photoresists[J]. Chinese Journal of Lasers, 2024, 51(18): 1801002
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