New possibilities for soft matter applications: eliminating technically induced thermal stress during FIB processing

Abstract

Heating effects on focused ion beam processing have been identified as a strong convolution of intrinsic and technically induced contributions via experiments and simulations. The systematic parameter variation reveals that classic serpentine- or raster-like patterning strategies can imply an additional heating of more than one order of magnitude above the intrinsic temperature increase during single ion beam pulses. This rise in temperature can lead to severe chemical damage of materials with a low melting point, such as polymers or biological samples. Based on these findings, an alternative patterning sequence is introduced which is able to eliminate this technically induced heating whereas process times are not affected. It is shown that chemical damage of the (polypropylene) test polymers is strongly reduced and can be compared to the results after classic FIB processing with low ion beam currents (500 pA → 50 pA, 30 kV primary energy) or at cryogenic sample temperatures (−150 °C). The successful reduction of local thermal stress towards the intrinsic and unavoidable limit – related to single pulse effects – might open new possibilities for focused ion beam processing of soft matter.