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RESEARCH PRODUCT
Lithography exposure characteristics of poly(methyl methacrylate) (PMMA) for carbon, helium and hydrogen ions
Timo SajavaaraS. SingkaratHarry J. WhitlowMikko LaitinenNitipon PuttaraksaNitipon PuttaraksaRattanaporn Noraratsubject
Nuclear and High Energy PhysicsMaterials scienceta114Ion trackAnalytical chemistryIon beam lithographyFluencePoly(methyl methacrylate)Proton beam writingIonResistvisual_artvisual_art.visual_art_mediumInstrumentationLithographydescription
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 Θ 0 ⩽ Θ Θ × 0 , where Θ 0 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 Jyvaskyla to determine the exposure characteristics in terms of fluence for 2 MeV protons, 3 MeV 4 He 2 + and 6 MeV 12 C 3 + 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.
| year | journal | country | edition | language |
|---|---|---|---|---|
| 2012-02-01 | Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms |