Sample Characterization with High Current Plasma FIB-SEM

insights from industryMartin SlámaProduct Manager for FIB-SEM TESCAN 

In this interview, we speak to Martin Slama at TESCAN, who describes sample preparation using high current plasma FIB SEM.

Can you describe what high current plasma FIB-SEM is?

The high current plasma FIB-SEM is the FIB-SEM that uses the plasma source to generate ions.

So, when compared to the more standard Gallium FIB-SEM - which uses a liquid metal ion source from which the ions are extracted - the plasma, in this case, is generated in a source - the gun - and the ions then are extracted from the gun.

The main benefit is then that this FIB-SEM allows us to use these high currents. Compared to the standard FIB-SEMs, which are usually the Gallium version, the plasma in the high current FIB-SEM allows us to work with higher currents than the standard Gallium FIB-SEMs.

Can you describe the FIB-SEM technique and what steps are taken to achieve a high quality final surface?

For specific FIB-SEM techniques, the FIB-SEM is used to modify the sample surface. It uses ions that are much heavier than electrons, allowing for the extraction of the ions from the sample surface. We can also use this specific approach to add or remove the material, so this is how the sample is modified. The key parameter is the quality of the surface you are polishing.

This means that there is no dependence based on the technique or the type of analysis you are performing. In the end, you always want to have a high-quality final surface. It does not matter if it is DM sample preparation, cross-section, or another type of sample you are preparing. For this, the user typically begins with higher currents and then limits the current to get better final quality. That is the standard approach. This is used on the Gallium, as well as on plasma FIB-SEMs.

What advantages does Plasma FIB-SEM provide for sample characterization?

The key advantage of plasma, as compared to the plasma FIB-SEM, the Gallium, or another source, is that it facilitates the use of the higher current at the beginning, allowing for faster removal of material.

There is also reduced damage to the sample during the milling, so it is ideal for sample preparation of all kinds. One of the main benefits is that it allows large surface area analysis. That is because we are able to use higher currents, and higher currents allow you to move faster. Once this is achieved, larger areas can be analyzed, as everything is just a matter of time.

Indeed, Fib-Sem can be used to polish large surface areas. What are the benefits of this?

A cross-section by the plasma FIB-SEM takes approximately one hour to prepare, whilst preparing a cross-section using the Gallium can take tens of hours. Simply put, this allows the higher current to be used and more material to be removed faster.

The benefit of analyzing the large areas is the statistics. All the people who are either buying or considering working with the FIB-SEM simply want to get the information. That is the tool that provides vital information. Once the user is able to see more, they are getting more information: not just statistical data but also detailed information in context.

As the user, I then know I can characterize the detailed information - because of the high resolution of the SEM - but I can also see what is around the sample. For example, when I focus on the larger area as opposed to just one detail, I can see why some material was formed. This scope provides an overview, which is a significant benefit of the large surface area analysis.

What is TESCAN’s TRUE X-Sectioning TESCAN Rocking Stage, and how is it used?

As I have already mentioned, one way in which the user can benefit from the high current is that they can analyze a larger volume.

Another is how the final surface quality is higher when the current is reduced. Essentially, the value of the current depends on the material being polished. This means that it is the property of the material and the current has to be lowered in order to get the final quality that is required. Milling large volumes and lowering the current to the particular value that suits the material will prolong the whole analysis.

In order to speed up the process of this large area analysis, we have dedicated solutions that we have developed over time. As the pioneers of this technique - of the plasma FIBs on market - we have the requisite experience, which we have utilized to figure out how we can help researchers get their data fast and more effectively.

One of the ways in which researchers can get their data faster and more effectively is the TRUE X-Sectioning, a technique that helps improve the sample quality, in which the TESCAN rocking stage also assists in speeding up the process.

Essentially, both techniques help to speed up the process because we are able to use higher currents. This means that we can apply higher currents and some artifacts can be mitigated by those techniques. There are, therefore, current techniques in play that are helping to speed up the process of sample surface polishing.

What role does it play in Plasma FIB-SEM 3D FIB-SEM tomography analyses?

The 3D FIB-SEM tomography is the set of images that are acquired from a method such as cross-section. Once we are able to speed up the process of preparation to get the final quality of cross-sections faster, we can apply it to 3D characterization.

This technique - or the plasma, in combination with the techniques mentioned before - help us to speed up the process of 3D characterization and therefore explore the larger areas.

How do you expect this field to change in the near future?

With completely new materials, there is a requirement for the systems to be versatile, get a better quality of the sample, and get the data faster. This is the process that is continuously going on, and indeed, I think that we can expect that to continue in the future.

What future developments and advances will help Tescan stay ahead of these changes?

Unfortunately, there is not anything that I can currently disclose – but we are working on it. Instead, I will simply state that there is a development in that particular field, and we are hoping to introduce something new in the market soon.

About Martin

This information has been sourced, reviewed and adapted from materials provided by TESCAN Group.

For more information on this source, please visit Tescan Group.