Ilion+™: A Breakthrough in SEM Preparation of Large Planar Cross Sections Drew Erwin, Gatan, Inc.

Can you prepare large area SEM cross sections quickly from your samples? This specialized and difficult application is now possible with Gatan's NEW Ilion⁺™, a significant advance in the preparation of large planar cross sections for microscopic imaging and microanalysis. The Ilion⁺ is a dedicated, ion beam based system for the preparation of large area planar cross sections from challenging SEM samples. The Ilion⁺ uses a proprietary milling system that exposes significantly greater areas than traditional FIB milling while encompassing a wider range of delicate samples not compatible with mechanical polishing and other techniques. The system is easy to install and operate allowing users to begin making samples quickly.

Model 693 Ilion+

SEM cross-sectional image of C4 bump prepared at 6 keV, in 3 hours using Gatan Ilion⁺.



Background

The revolution in nano-engineered materials is spawning new combinations of elements and compounds. Many of the new material combinations are either exotic phase mixtures (composites) or layered thin film structures (devices) that exploit the desired properties of the component nano-materials in ways that result in extraordinary products. To understand the spatial relationship and nano-structural arrangement of the component materials, researchers must view them at the molecular or atomic level using SPM, TEM, and SEM.

Increasingly, the combinations of exotic materials used in multi-phase and multi-layered thin films are not well suited to mechanical polishing or FIB milling. Soft materials tend to smear or become delaminated from the neighboring structure while hard or brittle materials fracture or shed particles into neighboring regions. The result is an unacceptable alteration of the true arrangement of the features. The same is true with composites where discrete grains or phases may be distorted by the shearing forces of polishing, effectively destroying critical spatial information and introducing chemical anomalies that affect subsequent EDX or surface analysis results.

Description of Technique

Masked broad ion beam milling, also known as “slope cutting,” is a surface preparation technique that utilizes a large (~1mm) ion beam to strip away an extensive, finely polished area for microscopy and microanalysis. A solid sputter resistant shield blocks half the ion beam, effectively masking the lower half of the beam and creating a lateral sputtering plane that strips away a thin layer of the sample surface. The resulting planarized surface is topographically flat and free of artifacts.

The Ilion⁺ masked ion beam milling technique has emerged as a powerful cross section sample preparation method for materials that do not lend themselves to mechanical polishing or focused ion beam milling.

Applications  • Semiconductor • Polymers • Geological • Solar • Paper   • Paint
SEM image of CMOS seven metal device. Sample prepared using Gatan Ilion+. Higher magnification image of the outlined area also shown.

SEM image of copper vias prepared using Gatan Ilion+™.

Features and Benefits

Samples are attached piggy-back to the unique Ilion⁺ sample blades in a positive positioning alignment jig which aids in achieving the correct sample to blade offset and parallelism. A keyed indexing system facilitates easy handling and repeatable insertion into the sample holder and allows re-milling after viewing samples in the SEM. Sample blades are re-useable and can be re-attached to new samples several times.

Once samples are set in place, the airlock is evacuated and the sample blade is transferred into the chamber. Since the inner chamber is always under vacuum, exchange cycle times are less than 20 seconds. A viewing window permits real-time observation of the sample milling progress. With the addition of high performance optics and a CCD camera, actual surface features can be monitored as an aid in determining the end-point of the milling sequence.*

*High performance optics (Zoom Microscope) and CCD camera available on the Ilion⁺ Advantage.

Pre-aligned sample loading into Whisperlok® integrated airlock stage.

Features	Benefits
Unique Sample Blade	• Re-useable • Sample is aligned to blade in external jig • Easy transfer to/from storage and SEM • Capability to re-mill the same area • Pre-aligned positioning in sample chamber
Sector Milling	• Minimizes topographical effects (curtaining) • Reduces heat damage
Turbo Vacuum System	• Minimizes hydrocarbon contamination • Removes volatile chemicals
Twin Ion Guns	• Enhances milling rates without damage • Redundant capacity (works with one gun) • Choice of argon or xenon ionizing gas
Variable Voltage	• Reduced energy for delicate samples • Facilitates optimal sputtering conditions
Variable Gun Tilt	• Allows change in plane or depth of cut • Promotes re-milling to an exact feature • Enhanced contrast between adjacent grains
Whisperlok® Air Lock	• Rapid and reliable sample exchange • Easy re-introduction of samples for re-milling
Zoom Microscope (Available on Ilion+ Advantage)	• Real time visual progress monitoring • Color LCD monitor
LN Cooling (Available on Ilion+ Advantage)	• Minimizes heat damage • Solidifies high melting point materials

Ilion⁺™ Advantage

The Ilion⁺ Advantage is for high-throughput, site specific, or special sample requirements where real time observation and/or sample cooling is required.

Cold Stage

Cryogenic cooling of the sample reduces the chance of ion beam induced heat damage in delicate samples. It can also solidify liquid samples, thereby stabilizing them in a vacuum and allowing sputtering without vaporization. Samples that were previously impossible to polish or FIB at room temperature can now be prepared for SEM cross section imaging and analysis.

SEM image of Gypsum. Sample prepared using Gatan Ilion+ at ambient temperature showing cracking and shrinkage at the grain boundaries.	SEM image of Gypsum. Sample prepared using Gatan Ilion+ and the cold stage showing intact grain boundaries.

Images courtesy of Dr. Juergen Schieber, Indiana University.

Optical Microscope

Complex thin film device samples often require repeated milling to expose features in the desired perspective for inspection or measurement. Using the optical microscope and CCD camera, the user can monitor the milling process in real time, changing conditions such as gun tilt to optimize the results.

Optical image of solder bump. Sample prepared using Gatan Ilion+.	SEM image of solder bump. Sample prepared using Gatan Ilion+.

For a PDF of the Ilion⁺ brochure, please click here or visit the Ilion web page.

For ordering information, please contact your local Gatan Sales office.