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Real-Time Drift Correction of a Focused Ion Beam Milling System

Freeman, Darren; Luther-Davies, Barry; Madden, Steve

Description

Focused Ion Beam (FIB) milling systems are attracting increasing attention outside of their traditional role as semiconductor inspection tools, and many researchers are now using FIB systems for nanofabrication. Although the commercial instruments will run for several hours, executing various automated procedures such as preparing TEM sections and milling nano-structures, they invariably suffer from some form of slow and systematic drift in the beam position over the specimen. Use of a FIB...[Show more]

dc.contributor.authorFreeman, Darren
dc.contributor.authorLuther-Davies, Barry
dc.contributor.authorMadden, Steve
dc.coverage.spatialBoston USA
dc.date.accessioned2015-12-07T22:46:59Z
dc.date.available2015-12-07T22:46:59Z
dc.date.createdMay 7-11 2006
dc.identifier.isbn097679859X
dc.identifier.urihttp://hdl.handle.net/1885/26006
dc.description.abstractFocused Ion Beam (FIB) milling systems are attracting increasing attention outside of their traditional role as semiconductor inspection tools, and many researchers are now using FIB systems for nanofabrication. Although the commercial instruments will run for several hours, executing various automated procedures such as preparing TEM sections and milling nano-structures, they invariably suffer from some form of slow and systematic drift in the beam position over the specimen. Use of a FIB outside of a temperature controlled environment makes this effect much more noticeable, so the traditional applications have either been short in duration (including manual inspection) or have used a carefully chosen milling procedure to deal with the problem. We are working towards the nano-fabrication of large periodic optical structures, known as photonic crystals. These structures must have extremely smooth and reproducible holes, on a lattice with nm position tolerance [1]. To achieve this we have developed our own custom pattern generation software. For example, we required a lattice of around 50,000 holes, 300 nm in diameter, to be milled over 100×100 μm2, taking more than three hours to complete. Unfortunately, systematic drift over this long milling time prevented the structures from being fabricated to within the required positional tolerance. Typically, the system could be expected to drift 200-1000 nm depending on the time of day, plus an additional 200 nm periodic component due to the air-conditioner cycling on and off. To overcome this challenge, we have developed a real-time drift correction system. By milling an array of reference marks and then imaging them periodically with the FIB, we are able to detect the apparent motion of the specimen under the beam to within a few nm, and update the beam shift to greatly reduce its impact. We demonstrate the measurement of drift in our FIB system and its effective compensation, leading to a striking improvement in the optical quality of our structures. See Fig. 1 for an example of recorded drift data, Fig. 2 for a drift-corrected lattice, and Fig. 3. for a close-up view of a reference mark and lattice. Aside from our use in nano-fabrication, FIB drift correction has also recently found an application in FIB tomography [2], the reconstruction of a sample volume by successive cross-sectioning and imaging. By improving the accuracy of sectioning, thinner slices can be used. Recognition of arbitrarily shaped reference marks also enables the milling to be indexed to existing structures, such as those produced in earlier lithography or milling steps. The technique also compensates for the unknown beam shift normally encountered when changing lens conditions, enabling the use of multiple beam currents without sacrificing positional accuracy.
dc.publisherNano Science and Technology Institute
dc.relation.ispartofseriesNano Sciences and Technology Institute Conference and Trade Show 2006
dc.sourceTechnical Proceedings Vol. 1 - 3 (CDROM)
dc.source.urihttp://www.nsti.org
dc.subjectKeywords: Computer software; Crystal lattices; Nanostructured materials; Real time systems; Semiconductor materials; Transmission electron microscopy; Focused Ion Beam (FIB); Periodic optical structures; Real-time drift correction; Systematic drifts; Ion beam litho
dc.titleReal-Time Drift Correction of a Focused Ion Beam Milling System
dc.typeConference paper
local.description.notesImported from ARIES
local.description.refereedYes
dc.date.issued2006
local.identifier.absfor029902 - Complex Physical Systems
local.identifier.ariespublicationu9912193xPUB41
local.type.statusPublished Version
local.contributor.affiliationFreeman, Darren, College of Physical and Mathematical Sciences, ANU
local.contributor.affiliationLuther-Davies, Barry, College of Physical and Mathematical Sciences, ANU
local.contributor.affiliationMadden, Steve, College of Physical and Mathematical Sciences, ANU
dc.date.updated2015-12-07T11:48:29Z
local.identifier.scopusID2-s2.0-33845202311
CollectionsANU Research Publications

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