Researchers in Finland are extending focused ion beam milling techniques to give orders of magnitude improvements in writing speed, opening the door to rapid prototyping of high aspect ratio silicon nanostructures.
Focused ion beam (FIB) milling is a well established top-down fabrication approach. While being extremely accurate and flexible, the method suffers from a very low speed, making it virtually impossible to fabricate large arrays of structures.
In our approach, we create silicon nanostructures by combining FIB with cryogenic deep reactive ion etching (DRIE), which shortens the process time by several orders of magnitude. The trick is to use the FIB to create a thin masking layer measuring only 30 nm.
Another benefit is that the introduction of a separate etching step gives better control over the side-wall quality compared with direct milling. Holes and pillars with aspect ratios of up to 15 can be fabricated routinely using the combined procedure.
In our resolution determination experiments with a Helios Nanolab 600 dual-beam system (FEI Company) and a Plasmalab System 100 reactor (Oxford Instruments), we achieved the maximum resolution of 20 lines/µm, so structures with a size of 50 nm can be created.
Application areas include plasmonics and metamaterials as well as nanomechanical networks and quantum structures.
The researchers presented their work in Nanotechnology.
About the author
The work was performed in the Helsinki University of Technology, Department of Micro and Nanosciences, Micronova. Nikolai Chekurov is a PhD student in electrophysics under the supervision of Prof. Ilkka Tittonen. Their research is focused on nanofabrication and nanoscale electrical processes.
Kestutis Grigoras received his PhD in 1992 from Vilnius University, Lithuania. Since 2006 he has been a senior scientist at the Microfabrication group, which is part of the Department of Micro and Nanosciences, Helsinki University of Technology, Finland. His current fields of interest cover atomic layer deposition (ALD), application of carbon nanotubes for microelectronics, formation of porous silicon and its application in microfluidics. He is a co-author of almost 40 articles in refereed international journals.
Antti Peltonen holds an MSc degree in a field of microelectronics engineering. His position from 2008 is as a process engineer at TKK-Micronova. His current interests are in micro- and nanofabrication.
Sami Franssila studied physics and chemistry at the University of Helsinki and holds a PhD in electrical engineering from Helsinki University of Technology (1995). He has worked at VTT, IMEC and since 1998 at Helsinki University of Technology. His research has dealt with various fabrication technologies for CMOS, MEMS and microfluidic devices. He has published 70 peer reviewed articles and authored a textbook Introduction to Microfabrication 2004.
Ilkka Tittonen studied technical physics at Helsinki University of Technology and received a PhD in 1992. Since 2000 he has been nominated as a professor of physics at Helsinki University of Technology. His research areas include nanotechnology, microsystems and optics.
