For coating the ceramic AlN substrate with Au using e-beam evaporator, what metal layer should be used at first as an adhesion-promoter? Is it Ti? In fact, I evaporated Ti/Au(20 nm/800 nm) on ceramic substrates, however, I experienced the metal peeling-off problem as shown in the attached file.
Could this problem be due to the fact that the substrate is not cleaned enough prior to loading it into the chamber? Is the pre-cleaning process very critical? How to clean the substrate before loading into the chamber?
The cleaning process is very Important, it may be the one reason. Apart from it your deposition parameters may also cause stress and may lead to pealing. You can also try Cr/Au instead of Ti/Au.
thanks, Rakesh. Could you let me know how to perform the cleaning process?
I think the Au layer is too thick. It is easier to peeled off while the Au is too thick. If you really need 800nm Au. Try to rotate the substrate while Au deposition.
I agree, cleaning should be the first thing. You can sonicate in acetone, then methanol and then isopropanol for a couple of minutes each time (as long as they don't react with the ceramic). Also you can try to put more Ti (it looks like you are depositing a lot of Au), a rule of thumb is 10:1 for Au:Ti. Also try a lower deposition rate (I think it will help too), maybe less than 1.0 A/s. A lower deposition rate will help for better vacuum and in general that is better, you can even evaporate in steps to allow the pressure keep low and don't let the material heat up too much. I particularly prefer Cr rather than Ti, it has better adhesion, but you need to consider that it is magnetic.
Good luck
Regarding the cleaning you can follow the process mentioned by Jorge and after Sonication you can continue cleaning with SPM -> RCA1->RCA2.
The substrate should be cleaned by etching the surface to prevent peeling-off.
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