Omniprobe’s OmniGIS® is designed with enabling features to extend capability and results for typical gas processes within SEMs and FIBs in a manner not previously achievable, and in doing so, opens up new opportunities for in situ experiments within FIB and SEM instruments. Learn what new results are possible.

1. APPLICATION NOTE apps@omniprobe.com
Advanced Applications Enabled By OmniGIS® Gas Injection
OmniGIS® Features
Omniprobe’s OmniGIS® (Fig 1) is designed with enabling gas, liquid and solid precursors for the broadest selection of
features to extend capability and results for typical gas precursor materials. A closed-loop linear translation drive with
processes within SEMs and FIBs in a manner not previously encoder feedback allows smooth and rapid adjustments of the
achievable, and in doing so, opens up new opportunities for needle height, stored locations for optimum deposition rates
in situ experiments within FIB and SEM instruments. One and eliminates the vibrations that pneumatic insertion and
of the OmniGIS® key features includes three precursor retraction cause, thus allowing nanomanipulated tips to stay in
gases delivered with a single needle. This approach allows place near the sample surface.
mixing gases prior to their impinging the substrate (useful, for
example, for flowing water with Pt to improve resistivity1 and
ensures all gases occupy the same optimized port location
for operations using a single gas or applying alternate gases
in rapid succession). Another key feature is the capability to
pulse the delivery valve, so the user has the option of running t-butoxide
with the valve full open (100% duty cycle), or at a minimum water
duty cycle required to achieve the end result, thereby reducing
overspray.
Figure 2
The OmniGIS® software allows one to build recipes for sequential
alternating cycles of gases. In this pressure fluctuation timeline,
during the GIS-ALD testing on aluminum tert-butoxide, the periods
associated with the tert-butoxide and water cycles are evident.
The individual pulses observed (6 for tert-butoxide and 3 for H2O)
are determined by the duty cycle in the GIS recipe.
Atomic Layer Deposition
Several applications are uniquely enabled by the combined
hardware and software features of the OmniGIS®. One of these
is atomic layer deposition (ALD). The semiconductor industry
Figure 1 has held tremendous interest in ALD technology for CMOS
The OmniGIS® multiple gas injection system high-k gate dielectrics, as well as DRAM capacitors and non-Si
device gate dielectrics. ALD is becoming the method of choice
The OmniGIS® has two inert gas inlets that provide for inert for other industries also, driven in large part by the demands of
gases to be operated as source gases or as carrier gases to nanotechnology. The OmniGIS® software interface provides a
assist transport of the precursor to the delivery site. These mechanism for building recipes that can sequentially alternate
also act as purge gases that automatically clean the lines using multiple cycles of gases (Fig. 2). Sequential cycling of precursors
a unique algorithm, determined by the phase of the source. with precise flow control and carrier gas mixing is exactly what
The precursor temperatures can be adjusted from 0 to 40° C to is required to enable epitaxial-type depositions such as ALD
achieve a working vapor pressure that does not have deleterious in a FIB-SEM environment (GIS-ALD). To prove the concept,
effects on the chamber vacuum. Pressure feedback control ALD using the OmniGIS® was performed on carbon nanotubes
within the OmniGIS® itself ensures consistent and repeatable (CNTs)2. The work of Farmer and Gordon3 showed that ALD
operation. The precursor crucible design is compatible with coating of CNTs was not possible without first “initializing”
the surface by room temperature pretreatment with repeated
(continued)
AN-GIS-052411 © 2011 Omniprobe, Inc. All Rights Reserved

2. cycles of NO2 and NOx species to form a monolayer ring. Figure
3 shows the 10nm conformal aluminum oxide layer deposited by
ALD on the CNT bundles, proving both the initialization and the
ALD process were achieved.
Nanopatterning
The OmniGIS® provides a powerful platform for direct write
nanolithography applications within a FIB or SEM. The claimed
minimum feature size for beam induced CVD from standard
commercial dual beam systems is typically around 50nm. The
drivers determining the tool capability are the beam process
parameters (beam type (electrons or ions), spot size, accelerating Figure 3
voltage, current, beam source) and precursor gas delivery
process parameters (carrier, flow, pressure, dispense proximity, Bright particles representing the iron catalyst
source temperature). For optimal resolution, it is desirable to are visible in this high angle annular dark field
STEM image of a section of bundled CNTs
mimic the ALD process described earlier. This means sequentially
that was GIS-ALD processed using t-butoxide
adsorbing one monolayer of precursor onto the surface at a and water. The lower left portion of the image
time and exposing the layer to the beam, thus depositing one contains a branch of CNTs low in catalyst
monolayer at a time. Pulsing the gas approximates this effect density. The ALD coating on this branch is on
and achieves 2-4x higher resolution or smaller minimum feature the order of 10nm in thickness.
size than can be achieved with a continuous flow of precursor.
With improved operator control of the precursor gas delivery,
deposition of arrays of less than 20nm Pt features with
approximately 1:1 spacing in a 20μm x 20μm array were achieved.
Some of the arrays produced were large enough that the ion
deposition rate with a 30kV 1pA beam resulted in a 24 hour run-
time to complete the array; hence, most of the experimental work
was performed using ion beam deposition. When doing e-beam
deposition, it was found that pulsing the source gas resulted
in faster deposition and crisper edges. Figure 4 shows an
example of 30nm ion beam deposited structures using tungsten
hexacarbonyl as the source. Experiments determined that
pulsing of the source is critical to enable large arrays (25μm x
25μm) of 15-30nm features with 1:1 spacing. In general, the
pulse rate must be higher if a carrier gas is not used, and the Figure 4
best pulsing scheme will vary as a function of the array size and
30nm structures were created by ion beam
feature size/spacing combination. induced deposition of tungsten hexacarbonyl
using the OmniGIS® (courtesy of Neal Meyer
and Arliena Holm, Hewlett Packard Corvallis).
1) Richard M Langford, Dogan Ozkaya, J Sheridan and Richard Chater (2004). Effects
of Water Vapour on Electron and Ion Beam Deposited Platinum. Microscopy and
Microanalysis, 10 (Suppl. 02) , pp 1122-1123 doi:10.1017/S1431927604883417
2) Principe, E. L., C. Hartfield, et al. (2008). Atomic Layer Deposition and Vapor
Deposited SAMS in a CrossBeam FIB-SEM Platform: A Path To
Advanced Materials Synthesis. Microscopy Today, 17: 18-25
3) Farmer, D. B. and R. G. Gordon (2006). “Atomic Layer Deposition on Suspended Single-Walled
Carbon Nanotubes via Gas-Phase Non-covalent Functionalization.” NANO LETTERS 6(4): 699-703
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