Fast and blister-free irradiation conditions for cross-linking of PMMA induced by 2 MeV protons

Somrit Unai, Nitipon Puttaraksa, Nirut Pussadee, Kanda Singkarat, Michael W. Rhodes, Harry J. Whitlow, Somsorn Singkarat

Research output: Contribution to journalArticlepeer-review

6 Citations (Scopus)


For soft lithography, the conventional negative tone resists, such as SU-8, that are used to create the mold have a number of drawbacks. PMMA, which is normally used as a positive tone resist, can be used as a negative resist by using high-fluence irradiation conditions. In this report, we outline optimization of the irradiation conditions for PMMA thin films using 2 MeV H + ions to exploit their ability to work as a negative tone resist at ion fluences above 1.0 × 10 15 ions cm -2. The main aim was to induce cross-linking while maintaining the exposed regions free of blisters and maintaining short irradiation times. We found that by using a two-step process with a low-flux irradiation, followed by a high-flux irradiation, the exposure time could be shortened by ∼50%. We also found that ion fluences greater than 5.0 × 10 15 ions cm -2 minimized the distortion in stitched regions.

Original languageEnglish
Pages (from-to)18-21
Number of pages4
JournalMicroelectronic Engineering
Publication statusPublished - 2013 Feb
Externally publishedYes


  • Blisters
  • Contraction
  • Cross-linking
  • H ion irradiation
  • Negative resists
  • PMMA

ASJC Scopus subject areas

  • Electronic, Optical and Magnetic Materials
  • Atomic and Molecular Physics, and Optics
  • Condensed Matter Physics
  • Surfaces, Coatings and Films
  • Electrical and Electronic Engineering


Dive into the research topics of 'Fast and blister-free irradiation conditions for cross-linking of PMMA induced by 2 MeV protons'. Together they form a unique fingerprint.

Cite this