Removing Residual Hydrocarbon Contamination Using the Evactron® De-Contaminator

The Evactron® De-Contaminator System, supplied by XEI Scientific, is capable of removing residual hydrocarbon contamination and provides users of ion beam and electron instruments such as TEMs, SEMs, and FIBs the ability to maintain optimal imaging environments.

When these hydrocarbons interact with the beam, it precipitates onto the sample surface under analysis and may lead to “black squares” as shown in Figure 1 on the left side. These contaminations can be easily removed from the vacuum system with the help of the Evactron® system and ultimately result in superior images, as shown in Figure 1 on the right side.

Figure 1. Before and after Evactron® cleaning

These undesired contaminants come from many sources and comprise the remaining manufacturing materials, vacuum system components, or the samples themselves. Today’s more complex analyses at lower accelerating voltages and higher magnification further increase the contamination problems, and enhancements in vacuum cleanliness have become more essential than ever.

In-Situ Cleaning

The in-situ cleaning feature of the Evactron® system is much more efficient when compared to “cryo-trapping” with a Liquid Nitrogen Cold Finger. Rather than just sequestering the hydrocarbon molecules, the Evactron® De-Contaminator removes them in a matter of minutes. Till date, more than 1,100 Evactron® units have been deployed worldwide.

XEI Scientific also provides a low power (<20 W) system that can be safely used for EBSD detectors, WDS spectrometers, EDS detector windows, and current stage lubricant materials. This provides the most effective and the safest method for removing hydrocarbon contamination in TEMs, SEMs, FIBs, and other vacuum systems.

How The Evactron® De-Contaminator Works

Users can easily install the Evactron® system by using adaptors and by using common flanges for ports, as shown in Figure 2. The systems have been interfaced with almost all models of electron microscopes.

Figure 2. Evactron® Model C De-Contaminator mounted on an SEM Chamber.

As and when the Evactron® in-situ plasma cleaning process occurs in the 0.05 –0.6 Torr (7-80 Pa) range, a cleaning cycle can be easily integrated with a sample exchange and chamber venting operation.

The Evactron® De-Contaminator uses a Downstream Plasma Cleaning technique, as shown in Figure 3. The PRS (Plasma Radical Source) is illustrated on the left side of the chamber.

Figure 3. Schematic of how the Downstream Plasma Cleaning works.

The PRS uses a patented hollow cathode to produce RF plasma, which is accommodated in the PRS module.

Reactive gas-phase radicals are then generated in the PRS that pass via the chamber of the instrument and chemically react with the redundant hydrocarbon molecules and convert them into CO2, CO, and H2O.

These by-products are removed by the system vacuum parts. Sensitive system components are not directly subjected to the energetic ions or plasma. For the PRS module, the optimum location is on a chamber port against the vacuum source.

Conclusion

The Evactron® De-Contaminator supplied by XEI Scientific is a fast, safe, and reliable system. All Evactron® models include a separate controller and a PRS with power cord and cable bundle. The Evactron® Models 25, 40 and 45 feature CD with PC user interface and C command library. All controllers have worldwide power input (100-240VAC, 50-60Hz, <2.0A).

About XEI Scientific

XEI Scientific, Inc. was founded in 1991 by Ronald Vane to provide an effective way to gently clean scanning electron microscopes (SEMs), focused ion beams (FIBs) and other vacuum systems.

XEI manufactures and sells the Evactron® De-Contaminator, which removes hydrocarbon contamination from SEMs, FIBs and other vacuum systems. It has been described by one of our users as the only accessory you can buy for the SEM that will improve the performance of the instrument.

This information has been sourced, reviewed and adapted from materials provided by XEI Scientific.

For more information on this source, please visit XEI Scientific.

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