Focused ion beam technology, capabilities and ... - FEI Company

Capabilities of the focused ion beam system
Apart from the superb FIB imaging capabilities obtained by regular scanning of the (low current)
ion beam, the system can also translate a pattern of doses onto the sample and induce active and
controlled surface milling.
Milling
As is shown by the basic interaction
of the ion beam with the sample,
milling is a continuous process that
always occurs during beam exposure.
The milling process as such is an
atomic collision process. The milling
rate (µm3 /s) is (linear) proportional to
the beam current and high amounts
of material are removed with high
beam currents. In addition, precise
control is possible by the use of
smaller spot sizes and hence smaller
currents. A typical rectangular area of
10 x 5 x 3 µm can take around 10
minutes for complete removal. As the
ion beam position is well controlled,
milling can be used to create a simple
structure such as a square or round
hole in the material, but also a more
complex pattern as shown below.
3.1 µm
Figure 13: Image of a direct write ion beam
nano-pattern in gold. Time to result is 8
minutes. Milling of complex patterns and
arbitrary shapes defined in bitmaps are a
basic function of the system.
Milling is the most powerful capability
of the focused ion beam and
directly related to the choice of ion,
its energy range and the momentum
of the particle (its weight). Milling
allows the freedom to manipulate the
sample, open it up in the third
dimension and create a cross-section,
or to create any possible shape as
“carved in stone”. Not only the lateral
position, but also the local depth
can be controlled. In this way milling
is different from etching with a mask
on the sample.
Removal of atoms from the surface
can be enhanced by the addition of
local chemistry in the form of a gas
delivery system. This local supply of
gas can, for example, change the oxidation
of released particles and may
Figure 14: Example of a cross-section imaged
and made by the FIB. The cross-section
shows an insulation defect on a semi-conductor
device.
substantially speed up the milling
process. In general it will also reduce
the local re-deposition of atoms
released from the surface. Examples
of gases that are used to enhance
milling are I2 and XeF2. Figure 15: Silicon surface showing both
milling and deposition capabilities as examples
of the creation of local structures. A, B,
C and D are micro-depositions, whereas E, F
and G are structures milled into the sample.
Figure 16: In-situ foil extraction using micromanipulators
in the chamber. The next stage
is that the TEM lamella shown on the tip is
deposited on a TEM grid, or “micro-welded”
onto a support ring that fits in the TEM.
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