Lithography exposure characteristics of poly(methyl methacrylate) (PMMA) for carbon, helium and hydrogen ions

Nitipon Puttaraksa, Rattanaporn Norarat, Mikko Laitinen, Timo Sajavaara, Somsorn Singkarat, Harry J. Whitlow

Research output: Contribution to journalArticlepeer-review

14 Citations (Scopus)

Abstract

Poly(methyl methacrylate) is a common polymer used as a lithographic resist for all forms of particle (photon, ion and electron) beam writing. Faithful lithographic reproduction requires that the exposure dose, Θ, lies in the window Θ0≤Θ<Θ× 0, where Θ0 and Θ× 0 represent the clearing and cross-linking onset doses, respectively. In this work we have used the programmable proximity aperture ion beam lithography systems in Chiang Mai and Jyväskylä to determine the exposure characteristics in terms of fluence for 2 MeV protons, 3 MeV 4He 2+ and 6 MeV 12C3 + ions, respectively. After exposure the samples were developed in 7:3 by volume propan-2-ol:de-ionised water mixture. At low fluences, where the fluence is below the clearing fluence, the exposed regions were characterised by rough regions, particularly for He with holes around the ion tracks. As the fluence (dose) increases so that the dose exceeds the clearing dose, the PMMA is uniformly removed with sharp vertical walls. When Θ exceeds the cross-linking onset fluence, the bottom of the exposed regions show undissolved PMMA.

Original languageEnglish
Pages (from-to)162-164
Number of pages3
JournalNuclear Instruments and Methods in Physics Research, Section B: Beam Interactions with Materials and Atoms
Volume272
DOIs
Publication statusPublished - 2012 Feb 1
Externally publishedYes

Keywords

  • MeV ion beam lithography
  • PMMA
  • PPAL
  • Proton beam writing

ASJC Scopus subject areas

  • Nuclear and High Energy Physics
  • Instrumentation

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