New developments in ligand-stabilized metal oxide nanoparticle photoresists for EUV lithography

Christopher Ober, Jing Jiang, Ben Zhang, Li Li, Emmanuel Giannelis, Jun Sung Chun, Mark Neisser, Reyes Sierra-Alvares

Research output: Chapter in Book/Report/Conference proceedingConference contribution

11 Scopus citations


The introduction of EUV lithography to manufacturing requires the development of both new EUV exposure tools and photoresists. The main challenges for photoresists are to achieve high resolution, and low roughness patterning at very high sensitivity given the limited intensity of current sources. A new class of photoresist formed from ligand-stabilized metal oxide nanoparticles shows extraordinary sensitivity for EUV lithography. These nanoparticles are processed in traditional organic solvents for both deposition and development as negative tone resist; positive tone images are possible if the aqueous base developer is used in addition to a post-exposure bake step. This paper presents new developments in the study of ligand-stabilized nanoparticle photoresists for EUV lithography. It is our current understanding that a key aspect of the solubility change of these photoresists during exposure involves ligand displacement by anions generated from photoactive compounds such as sulfonic acid photoacid generators. Both positive and negative tone patterning are possible and depend on thermal treatment history and choice of developer. On the basis of a non-chemically amplified ligand exchange mechanism, new resist structures were created. Both aromatic and aliphatic carboxylic acids with different functional groups have been studied in the formation of the nanoparticles and include dimethylacrylic acid, isobutyric acid, toluic acid. It has been shown that those nanoparticles with higher binding affinity ligands show better resolution and line edge roughness under EUV exposure. Some formulations demonstrate EUV sensitivity as high as 1.4 mJ/cm2, while other formulations demonstrate that improved LER values of 3-5nm. The overall resolution, sensitivity and roughness tradeoff has been evaluated and provides an understanding of structure - property relationships. In this paper, we also discuss major efforts on the further understanding of the patterning mechanism. By testing the dissolution rate and plotting it in Hansen interaction triangles, we can compare the differences between different formulations and choose a suitable developer for each formulation. We also used the dissolution rate study to confirm the important role of PAG and ligand exchange for pattern formation. In addition, aspects of the EHS properties of these new photoresists have been investigated and will be discussed.

Original languageEnglish (US)
Title of host publicationExtreme Ultraviolet (EUV) Lithography VI
EditorsObert R. Wood, Eric M. Panning
ISBN (Electronic)9781628415247
StatePublished - 2015
EventExtreme Ultraviolet (EUV) Lithography VI Conference - San Jose, United States
Duration: Feb 23 2015Feb 26 2015

Publication series

NameProceedings of SPIE - The International Society for Optical Engineering
ISSN (Print)0277-786X
ISSN (Electronic)1996-756X


ConferenceExtreme Ultraviolet (EUV) Lithography VI Conference
Country/TerritoryUnited States
CitySan Jose


  • EUV
  • ligands
  • metal oxide nanoparticles
  • non-chemically amplified resist

ASJC Scopus subject areas

  • Electronic, Optical and Magnetic Materials
  • Condensed Matter Physics
  • Computer Science Applications
  • Applied Mathematics
  • Electrical and Electronic Engineering


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