I am depositing TiAlN coatings on Si wafer in order to study the coating structure. Unfortunately I am unable to achieve very clear pictures for this coating. Can anyone suggest a suitable method for the investigation of such coatings on Si wafer?
I would suggest the folllowing techniques.
XPS gives you lot of information and is very useful.
SEM - FIB where you can prepare the sample for the TEM studies.
From the TEM studies, you can study the interface between the Si/SiO2/TiAlN coatings much clearly and understand the orientation relationships or the growth.
From the SEM, you can get a faint qualitative results about the composition. But the morphology should be visible clearly.
What does it mean "unable to achieve very clear pictures"?
SEM problem?
Specimen preparation problem?
Picture could be helpful.
Well, I recoment to combine the SE (secondary electron)
and BSE (backscattered electrons) image to know better chemical and morphological contrast. Do also EDX including mapping.
As regards of the imaging problem, it might be charging effect. What is the resistance of your coating? You may deposit thin Pt or Au layer to avoid charging. Otherwise, trz different HV.
I have deposited Au and had also tried various HV value but unfortunately no positive results.
I did many FE-SEM investigations on TiAlN coatings in past years.
I would suggest you to use low kV imaging. From my experience 3-5 kV was the best choice for TiAlN coatings on metal support and 1-2 kV on Si or Al2O3 support, 25-50 pA in both case. I could easily see even thin layered structures in case of TiAlN/CrAlN, their thickness and periods via mixing InLens (voltage contrast) and SE signals. I didn’t use any coatings. But in case of Si support I would suggest 2 nm of Cr layer for easier imaging.
Regarding Z-contrasted images – it is very hard to do clear images on such a coating (if they are thin) with standard retractable or bottom mounted BSD detector at HV. But it’s possible to do it with Inlens or TLD type of detectors which can operate in BSD mode at lower HV.
Thanks for posting pictures. Now I fully agree with Gregor Kapun: you need to work with lower voltages and in in-lens mode (I believe your SEM is capable of it). Try to run specimens without any additional coating (like Au). You can see what you can get from beautiful picture Gregor Kapun posted.
Support Vladimir Dusevich comment. Here are some more examples of TiAlN coating imaging at low kV. All samples were unsputtered. You can read the used parameters out of image datazone. Mira has InBeam SE detector as an option. If you have it you can combine it with SE to get optimum image in TiAlN case. You can do similar images using just SE detector at 1 or 2 kV in that case you will see more surface info but you will just lost voltage contrast in case of fine detailed layered structures inside coating if present.
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