I am trying to deposit Nb3Sn from a stoichiometric target using DC magnetron sputtering technique. The target diameter is 2 inch. I was applying 50 W DC power for 2 hours but the power increased to 150 W after 1.5 hours. Could you please explain the reason behind it and suggest to solve the issue?
Probably the power supply is not stable. Try some other target and try to sputter, and if the same thing happens, then the power supply is not stable.
I have used other targets (Nb, Al, Cu, Ni) with the same power supply. It worked fine.
Hi! Is there any noticeable discoloration on the target? It may be oxidising slightly. Usually the voltage of the sputtering is seen to change change in such a case (you see this also have noticed this Al and Ni.) There is also the potential that there is poor thermal contact between target and backing, which results is a worsening deposition rate, but this would return to its original level after a shut down. If the target is oxidising, then it may eventually need light polishing, or blasting at higher power to clean it up.
I removed the target today and found this black feature. The target doesn’t have crack. Do you have any idea about the black line?
Hi! From the look of the photo, it appears as if the target is ultimately sputtering just within the black area, so the plasma is becoming very localised almost continuous arcing. The black area has the appearance of re-deposited target material. (The more smooth area within is symptomatic of a higher sputtering rate than the "dimpled" surface of the rest of the target.)
Is there something on the counter electrode that is making the (anode -cathode) gap in this area smaller, a heavy deposit for example. You also get this localisation if the chamber pressure is a little to high.
Also, as the target gets eroded and hot, the resistance will change. Can make power a fixed value and the system will vary the potential and current.
Hello, maybe you can check the homogeneity of the magnetic field. Sometimes the magnets could overheat and loose locally their strength.
Md. Nizam Sayeed,
Verify the thickness of your target - the image looks to me like you have sputtered through the target. When I did that as a graduate student, it heated the adhesive material to the point that it melted, and the target fell off mid deposition. When I pulled everything out, the target looked much like what you show there.
Best of luck,
George Peterson
If you set your (DC ?) power supply in constant power mode, then power should always remain stable (sputter current will change if because of target surface oxidation the voltage is changing). Please first verify this. Also, does your magnetron have a rotating magnet array? It looks like rotatopn has stopped and erosion is only locally.
Also you might check the homogeneity of the target composition. Perhaps it was disturbed during overheating and possible local segregation of the low-melting component due to poor contact between the target and the water-cooled plate.
Just replace this target with a normal, new target of the same type, namely Nb3Sn stoichiometric target. Buy a new one and run the same experiment. What was the result?
If local dark point was observed on target, there are some problems such as one is related with homegenity of target, 2nd one could be related with undesired thermal variation on target, that could be cooling problem and 3rd one is non-uniform plasma during sputtering process that can be related with purity of argon and power of sputtering. Other main point, DC power supply is not working properly, if it was kept at constant power, it must stay at that power whether oxidation on target or not.
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