Is the thin film quality, porosity, roughness, etc., different when sputtered via RF or DC? Assuming that all other parameters such as power, pressure, Ar flowrate, deposited film thickness, are the same.
Hello. DC is used for metallic targets and RF for non-metallic targets. Cheers.
Hello Erie, I have spare RF guns that I fit with metallic targets and I'm wondering if an RF-sputtered metallic thin film would have different thin film qualities as opposed to one sputtered via DC.
generally, RF or DC sputtering can due to difference of structural in layers (Sensors and Actuators A 113 (2004) 355–359) because the process of each one is different.
Often, the DC method is for metallic target and RF is for nonmetallic.
This problem is much more prevalent in oxide sputtering compared to the deposition of metallic films, but a major influence on the film morphology will be the bombardment of the film by high energy (charged) species. Negative ions that form at the target surface will be accelerated along the cathode sheath and therefore pick up kinetic energy equal to their charge multiplied by the cathode potential (q x U). The cathode potential with regard to the plasma will be in the order of 100 V, therefore the kinetic energy of these particles will be quite high in comparison to neutral particles. The applied potential will vary significantly between RF and DC sputter deposition.
Please note that in magnetron sputtering, the exact position of the substrate in relation to the target also might have a major influence on film properties, as the bombardment differs between a position opposite the erosion groove or the center of the target. Have a look of the publications by Klaus Ellmer (HZB Berlin) for more details on the influence of high energetic particles in sputter deposition.
This is quite a complex topic and in my opinion can not be answered in a general matter, as it is dependent not only on target and substrate material, but also gas composition, pressure and deposition geometry. If you have the choice between both methods, I would advise to try both and choose the one which yields the results that suits your needs better.
However, in my limited experience with metal sputtering, if you just want to produce a conductive thin film, the choice between RF and DC sputtering should not be a critical one.
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