Strategies for fabricating nanostructures with focused ion beam technology

Focused ion beam (FIB) has emerged as an important too] in research in the field of nanotechnology (1). With computer controlled ion beam steering, it is possible to mill complex nanostructures (2). It is also possible to control parameters Such as beam currant. spot overlap, dwell time and milling sequence. Patterns can be programmed and run on the systems as stream files (.str files). One of the problems that limits the accuracy and resolution of the patterns being milled is the re deposition. Depending on the milling parameters. Sputtered ions can travel a distance and redeposit in the structure being milled. In this investigation, the effect of the milling parameters oil the fabrication of nano patterns in silicon is evaluated. Another problem with milling patterns is that the beam is not switched off while traveling from one feature in the pattern to the next. This means that with high number of loops the Surface between the features is also milled. This makes it necessary to find an optimum between the dwell time which influences re deposition on one hand and the number of loops which can lead to unwanted milling oil the other. Results of the milled patterns are presented. Cross sections are investigated to evaluate extent of re deposition. Milling strategies for Optimum results are discussed.