Dose-dependent milling efficiencies of helium and nitrogen beams in PMMA

• Published in: Microelectronic engineering Vol. 249; p. 111621
• Main Authors: Ellrott, Günter, Ogawa, Shinichi, Uno, Munenori, Morita, Yukinori, Manoharan, Muruganathan, Koleśnik-Gray, Maria, Krstić, Vojislav, Mizuta, Hiroshi
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier B.V 15.09.2021; Elsevier BV
• Subjects: 3D lithography; Atomic force microscopy; Blistering; Blisters; FIB; Gas source ion beam; Helium; Helium ion beam milling; Helium ions; Ion beams; Ions; Microscopy; Nitrogen; Nitrogen ion beam milling; Nitrogen ions; PMMA blisters; Polymethyl methacrylate; Silicon dioxide; Trenches; Helium ion beam milling; Nitrogen ion beam milling; PMMA blisters; Gas source ion beam; FIB; 3D lithography
• ISSN: 0167-9317; 1873-5568
• DOI: 10.1016/j.mee.2021.111621

Focused ion beams with varied exposure dose were used to mill rectangular trenches into PMMA on SiO2. The dose response was investigated by atomic force microscopy measurements. TRIM calculations were used to simulate the ion distributions and damages expected inside the target. The depth of the trenches measured by AFM showed an unexpected decrease for intermediate dosages of high energetic helium ions in contrast to low energetic helium and nitrogen ions. This has been attributed to the formation of metastable blisters in the PMMA layer. [Display omitted] •Ion Beams mill into surfaces to allow nanostructuring.•Milling efficiencies depend on the acceleration energy.•Low energy helium and nitrogen ions show increased milling over dose.•Unexpected low milling efficiency at intermediate doses of high energy helium ions.•Blister formation in PMMA possible mechanism for milling efficiency reduction.