In most literature the reverse voltage used in the Pulsed-DC sputtering is mentioned as a method for build-up charge dissipation and thus preventing arcing on the poisoned target surface. The phenomena is relatively straightforward, however, I cannot find any review with calculations showing the impact of the reverse voltage and reverse time duration on the number (at least theoretical) of electron current to the target surface or denisity of positive charge undergoing recombination. Can you recommend any publications related to this subject?
Since you have a surface charge problem, the best solution is to avoid it all together. I assume that you are sputter depositing an insulating film onto an insulating substrate. This is what usually leads to this problem. Your sample simply cannot dissipate the charge build-up from being in an ionized plasma.
The best way to avoid this is to change the geometry of your sputter gun/substrate. Typically, the substrate is located 'facing' the sputter source. This provides the highest deposition rate. This geometry is referred to as 'on-axis'. Instead, you need to turn your substrate 90 degrees such that the edge of the substrate, not the top surface, is facing the sputter plasma source. Furthermore, you will want to move the entire substrate laterally to the edge of the sputter plasma. This geometry is known as 'off-axis'. Instead of depositing material from the ionized plasma, you will now deposit material from diffusional drift to the side of the plasma. The deposition rate is much slower, but charging will no longer be an issue. This method was first used in the early 1990's to deposit metal oxides onto single crystal oxide substrates - i.e. for things like the growth of YBaCuO superconductors.
Good luck.
interesting question.. waiting for an answer..
probably everyboby is taking care of avoiding it, without having done the work of quantifying it, since avoided it was running.
Probably not so easy to quantify, what is the charge carrying capacity of a target?
(the variability of leakages may some difficult to assess, hardware, contaminants, pressure (moisture)?)
Target charges until no ions can reach it, if secondary electrons are not created the DC plasma turns off.. how do the secondary electrons work? (for Hipims it is a new subject)
https://www.researchgate.net/publication/258100501_christmas_plasma
there is not any quantitative information, but a litle illustration of possible effects of charge building on a cathode.
It is a rod a steel where a MVP plasma is burning (burning? glowing). Doing some PECVD with Methane creates a bad conductiv DLC coating on it (some 10s of nanometers). Then the next time the plasma is on one can see those non-conductiv regions where these local 'plasmons'? (more intensiv glowing points on the yet DLC surface) distributes.. they move because of ?? to the anode and disappear. The charging seems to come from the left where the rod is less coated ,but I believe this is a fake. The thinner coated parts just builds up charges slower since they are more conductiv. With time the non conducting coating is sputtered off. Ans all disappears.
Looks like a illuminated Christmas Tree..
Data christmas plasma
If any new information is available, please tell us.
If you a research institute for it? I would suggest Stuttgart (near to your HQ), need a post-doc? would be happy.. Well, Freiburg is nice too.
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