• Adashkevich, Vadzim
• Tavares, Luciana
• Rubahn, Horst-Günter
• Chiriaev, Serguei

Abstract

Nanofabrication with focused ion beams (FIB) is a widely used technology for tailoring of e.g. optical and plasmonic elements [1]. The technology is essentially based on material removal by ion sputtering (ion milling) or ion-beam assisted chemical etching [1]. In addition, FIBs can decompose polymermaterials,whichresultsinmaterialshrinkageintheirradiated areas [2].Inthiswork,wedemonstratethatthismechanismcan be usedfornanopatterningthin metalfilmsdepositedonPMMAresistspin-coatedontoasiliconsubstrate.Forthispurpose,thesamples were irradiated with He+ FIB in a Zeiss Nanofab HIM under different conditions. We investigated the effect of different landing energies as well as different metal and PMMA thicknesses, while keeping the dose below the critical value [3]. In addition, irradiation tests with Ne+ and Ga+ ion beams were also performed. The influence of landing energy, metal thickness, and metal composition was not pronounced. On the other hand, the PMMA thickness showed a significant effect on the depth of the exposed areas. We used SRIM simulations to interpret these results. In thick PMMA, the majority of the collision events occurred in the bulk PMMA, which would cause more shrinkage compared to the situation in thin PMMA layers, where the majority of the collision events took place in the underlying silicon substrate. The depression generated by exposure to Ga+ beam are rougher and around three times deeper compared to the irradiation to He+ and Ne+ ions. We presume that it is due to material removal by sputtering with the Ga+ beam.<br/>[1] G. Hlawacek and A. Gölzhäuser, Helium Ion Microscopy, Switzerland (2016).<br/>[2] L. Sawyer et al. Polymer Microscopy, Springer New York (2008).<br/>[3] F. Schrempel et al. Applied Surface Science 189, 102-112 (2002).<br/>

Topics

• impedance spectroscopy
• surface
• polymer
• simulation
• grinding
• milling
• focused ion beam
• Silicon
• etching
• microscopy