It's probably due to stage drift as it sounds like your sample should be well grounded. If as Denis has implied you are doing a 3D volume slice and view, then I suspect that you are not letting the stage stabilize before beginning. Once you have the stage in final position wait about 1 hour before beginning. How long depends on the quality of the stage you have.

If this is not the case then I need a bit more info from you about what you are doing.

Which microscope do you use?

Usually FIB-SEM software (e.g. FEI Auto Slice & View) has some tools for shift correction. Did you try to use them?

Physically, there are at least a few factors:

• Charging (it shouldn't be a problem for your conductive sample);
• Instability of the microscope (thermal drift, vibrations, fields, etc.)
• Geometry of the sample (non-parallel, heterogeneous or contaminated top surface).

Check the stability of conditions (temperature in the room), try to decrease the ion current and use drift correction software tools.

Good luck!

It's probably due to stage drift as it sounds like your sample should be well grounded. If as Denis has implied you are doing a 3D volume slice and view, then I suspect that you are not letting the stage stabilize before beginning. Once you have the stage in final position wait about 1 hour before beginning. How long depends on the quality of the stage you have.

If this is not the case then I need a bit more info from you about what you are doing.

In addition to already said, carbon tape is always under suspicion when a drift occurs. Especially when a specimen is not of a simple brick-like shape.

Hello Denis and Steven,

Denis: I checked yesterday software and we don't have auto shift correction tool. Before loading the sample into the chamber I am doing cleaning using UV light (Zone cleaner). My samples are flat and smooth (Ra=100 nm).

As Steven said, After loading the sample, I kept for overnight under vacuum and then started FIB. However, still, the beam moved to about 17 um. I am totally confused about why this is happening. Today, I am trying like...waiting for 1 Hrs before starting beam to mill.

Vladimir: Yes by considering this fact I have removed carbon tape and used completely Ag paste (after applying Ag I have waited for 1 Hrs and later put under sample dryer and used Zone cleaner to clean contamination).

Hi Krishnanand,

17 um?! Definitely, something is wrong. During FIB-SEM, typical beam drift is less than up 1 um per hour. Could you describe your experiment and the microscope?

Hi Denis,

I am using QUANTA 3D FEG FEI machine. I have put my sample on aluminium sample holder using silver paste. I am using beam current of 50 pA for now. As I said earlier before loading I followed sample surface cleaning using UV source.

If I am missing something please suggest me I can try that as well.

Thanks

Does the drift continue in the one direction only, or is it a random walk, or does it eventually jump back to the start and begin again? What instrument do you have? It may be of poor quality or perhaps you have a dirty pole piece or charging particles in your FIB column.

I've also seen this before on a FEI Quanta more than 5 years old. It was due to insuficent cooling to the FIB powerboards. An extra couple of fans fixed it.

The drift is happening in curve way. It's not just simply one direction. After around 16-17 um it stop moving and does milling.

I will check probably pole piece...

Please do check attached image.

Sorry,

Wear track which I am analysing is also have oxide layers. Do you think it is do to that. In image which I shared you can see black area...that is exactly a oxide dominant area.

Lol yes that is why. The oxide is charging up. I thought your sample was just alloy. Gold coat the whole thing and try to minimise fib exposure to the gold on the oxide.

Try scanning with the sem while milling to try charge rebalancing. Or use a flood gun if you have one fitted which I expect you don't.

Okay I will try this

Hi Krishnanand ,

I can recommend not to use carbon tape. Conductive silver is the best solution to fix your samples on SEM stubs for FIB preparation.

A thin conductive coating (Au, etc.) will help prevent charging of your sample surface (charging due to oxides). But keep in mind that a thin coating will modify the sample surface. Just in case you planed a EDS measurement in order to chemically analyze the sample.

Charge neutralization might also help.

Another possibility that sometimes helps is to increase the milling current of the Gallium beam. Especially in Auto Slice n View mode, you will decrease the time needed to cut a new slice and therefore drifting of your sample during milling is reduced.

Dear Dr Bernd,

Thank you very much for suggesting me on my problem.

As Steven and Denis already suggested me these things earlier. Most of them I tried, and still I am facing the same problem. Currently, I am discussing with a company engineer to look at FIB powerboards cooling ( steven suggestion). Also, I am thinking to propose to get a flood gun for effective charge neutralisation.

Yes, I need to perform EDS measurement after each FIB. So, I am trying to avoid any coating (Au).

Also, I stopped using carbon tape. Now I am just using Ag paste to hold sample on the stub. It minimises the drifting length.

I will update once I have any improvemnet on this issue.

Thank you all for helping me to understand my issue well.

I have used FIB-SEM on a bone sample with minimum drifting issue. I coated my samples with gold sputter, painted the samples side surfaces with a conductive silver pain, and used carbon tape to attach the samples on the aluminum mountings. I would suggest checking the instruments setting (I used a Zeiss cross-beam), and try using a beam with lower current.

Hope that works for your case

Thank you mohammad for your suggestion. I will try this way as well.

Has it worked to sputter the sample? even if you want to perform EDS measurements the sputtering should not disturb too much.

Have you tried to perform a fast and coarse milling with a high current followed by a fine milling in a second step?

Nevertheless a beam shift of multiple micon is alarming.