100
D. W. Eastman et al.
Fig. 1 Images of an FIB cut sample (a) after a first cut in the milling procedure and (b) cut to the
final sample geometry
maintain beam focus, which can lead to taper or curtaining and result in uneven
material removal [64]. It is possible to shift the focus of the beam, but that requires
more time and effort to reposition the beam multiple times to make one cut.
Another drawback of using the FIB for sample fabrication is the difficulty
in machining nonconductive samples. Due to the use of charged particles in
both FIB and SEM imaging, it can be difficult to image samples that are not
conductive. Charging makes it difficult to perform precise machining and utilize
image processing for automated processes. Another aspect that makes working with
the FIB difficult, especially with sensitive samples, is that imaging a sample with
the FIB can cause ion irradiation damage at the sample surface and can continue to
ablate material if the current is too high while imaging. For this reason, most FIB
systems are combined with an SEM for imaging to prevent this damage. However,
this becomes a challenge when trying to automate machining using a fiducial
marker, because the fiducial mark needs to be in the plane of the machining path.
The electron column views the fiducial mark at an angle, and image recognition is
more difficult in projection. When imaging with the FIB, capturing a single quick
image rather than imaging continuously is preferred, if the imaging conditions can
be maintained throughout the machining process without damaging the sample.
3.2 Wire EDM Machining
A machining technique that is more commonly used for macroscale component
fabrication, but can also be applied at the microscale, is wire electrical discharge
machining (EDM). During EDM, the sample and wire are first submerged in a
D. W. Eastman et al.
Fig. 1 Images of an FIB cut sample (a) after a first cut in the milling procedure and (b) cut to the
final sample geometry
maintain beam focus, which can lead to taper or curtaining and result in uneven
material removal [64]. It is possible to shift the focus of the beam, but that requires
more time and effort to reposition the beam multiple times to make one cut.
Another drawback of using the FIB for sample fabrication is the difficulty
in machining nonconductive samples. Due to the use of charged particles in
both FIB and SEM imaging, it can be difficult to image samples that are not
conductive. Charging makes it difficult to perform precise machining and utilize
image processing for automated processes. Another aspect that makes working with
the FIB difficult, especially with sensitive samples, is that imaging a sample with
the FIB can cause ion irradiation damage at the sample surface and can continue to
ablate material if the current is too high while imaging. For this reason, most FIB
systems are combined with an SEM for imaging to prevent this damage. However,
this becomes a challenge when trying to automate machining using a fiducial
marker, because the fiducial mark needs to be in the plane of the machining path.
The electron column views the fiducial mark at an angle, and image recognition is
more difficult in projection. When imaging with the FIB, capturing a single quick
image rather than imaging continuously is preferred, if the imaging conditions can
be maintained throughout the machining process without damaging the sample.
3.2 Wire EDM Machining
A machining technique that is more commonly used for macroscale component
fabrication, but can also be applied at the microscale, is wire electrical discharge
machining (EDM). During EDM, the sample and wire are first submerged in a