Dear all,
I have a question about the operation of an RF Ion source with 3 Molybdenum grids used as sputter source In DIBS (dual ion beam sputtering) system. During the deposition of metals and especially Platinum, the Ion beam current decrease. To compensate this, the software of the DIBS system has to increases the generator power until saturation at 1000W. After saturation, the current continue to decrease along the process. Moreover, this effect is irreversible. Indeed, for a second process the source is already saturated from the beginning. I think that this problem come from the into the sputter source.
I tried to:
- Increase the flow of Ar --> it help but not as required.
- Decrease the process ion beam current --> power saturation occurs after more time.
Many thanks in advance for your assistance
Typically RF sources are not recommended for metal processes. The plasma is formed by the RF coil around a quartz chamber, and when that quartz chamber gets coated with metal, it blocks the RF signal from reaching the plasma. Increasing the power allows it to penetrate the metal, but you've already reached the limit of your power supply.
This effect is technically reversible; you just need to pull out the quartz chamber and remove the metal from it. This can be done by etching (liquid or ion), or with mechanical means. For cleaning our in-house sources, we use a sand blaster with fine grit media and only turn the pressure up high enough to remove the coating. If you're too aggressive, you can shatter the quartz chamber, and then it must be replaced. (if you want advice on this, contact me: rice at ionsources.com and I can try to help)
Are you sputtering oxides in addition to your metals? Are you using oxygen as a process gas? If not, you might consider switching to a DC-type source, which has a metal chamber that doesn't mind being coated in metals. Oxygen and oxides will reduce the filament lifetime, and you'll end up trying to remove glass from metal instead of the other way around. However, if you're sputtering both metals and oxides, I think the RF is the right type of source for that.
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