Frequency Effects on RF Plasma Reactor Behavior

There are two potential explanations of why the ion bombardment is more intense at low frequencies. First, the sheath potential drop, on average, will be higher at the lower frequencies. The electrons are lighter than ions, so they 

Secondly, the plasma potential will vary with time, depending on the cycle of the applied potential.22 If the ion can transit the sheath before the applied electric field reverses, it can experience the maximum sheath potential. As the frequency is raised, the ion cannot cross the sheath before the field reverses, so it experiences the average sheath potential which is approximately one-third the maximum. Therefore, ion bombardment will be less intense at the highest frequencies. 

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