As Enrique said, this frequency is an internationally allowed one to do experiments with out interfering with other RF devices (cellular phones, etc etc). You can achieve it with a comercial RF source that are usually preset at this frecuency. A brand can be for example Advanced Energy Products. If any commrcial provider is avaliable (they are expensive), you can use the radiofrequency generator that is used to broadcast. In any of those cases, you need an impedance coupling box, basically a variable capacitor array to eliminate the reflected power. My advice, if you can buy it or you are not expert in radiofrecuency devices, better check for a commercial source that includes a manual or even better, an automatic capacitance coupling box.
There are cases when higher frequency (60 MHz) is used for sputtering metals.
In addition to the comments from the other researchers on the international agreement to reserve this frequency for industrial and laboratory processes, the RF signal is used in sputtering, since it allows to widen the range of materials that are used as a target. Metals are generally deposited by DC sputtering. However, electrical insulating materials like oxides, nitrides, and others may accumulate static charge when used with a DC signal, reducing the yield of sputtering.
The use of an RF signal guarantees the target electrostatic discharge in each cycle and therefore allows to deposit any type of insulating or conductive material .
The problem added with the use of RF sources is the adaptation of the complex impedance that generally shows the sputtering cathodes. But this can be arranged by using a high power coaxial cable to connect the cathode and power supply and inserting an impedance matching circuit tpreventing power reflected from the cathode back to the power supply.
This technology was developed long ago to solve the problem of impedance matching of the antenna to the radio station. To understand more about this topic you need to read about the theory of transmission lines.
Generally you need to play with L and C, where C should be a variable capacitor to adjust to the fluctuations if the plasma
AS seen in all the previous e-mails you can use different frequencies.
However international standards have fixed 13.56 MHz for the rf power supply meant for thin film deposition equipment.
Yes one can calculate the usefulness of the frequency to be in MHz for thin film sputteirng.
You can refer the beautiful book "Glow discharge p[henomena" writtent by Brian Chapman. I found this book to be one of the best, and explains with clear examples and calculations.
prof. K. Sreenivas
Another aspect of this frequency is that is still low enough ensure momentum transfer of Ar ions to the sputter target which is necessary for sputter deposition or physical plasma etch. The higher frequency may effectively immobilize Ar ions in the plasma which may desirable only if you want electrons to do all the work (the process may be more like e-beam evaporation).
Agreeing with the answer given by Prof. Sreenivas that "However international standards have fixed 13.56 MHz for the rf power supply meant for thin film deposition equipment. Yes one can calculate the usefulness of the frequency to be in MHz for thin film sputtering.".
This is suitable for most of the materials.
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