The effect of the driving frequency on the optimum hole diameter for efficient multi-hole electrode RF capacitively coupled plasma

In capacitively coupled plasma, the driving frequency is changed to modify the ion bombardment energy and electron density. The multi-hole electrode capacitively coupled plasma is discharged with various driving frequencies of 13.56 MHz, 27.12 MHz, and 40.68 MHz, in order to elucidate the frequency effects of the discharge. The change of the driving frequency modifies the plasma parameters and the length of the sheath. As a result, the optimum diameter of the holes on the multi-hole electrode for efficient capacitively coupled plasma discharge changes.

►The multi-hole electrode plasma is capacitively discharged at various frequencies. ► When the driving frequency increases the length of the sheath decreases. ► When the hole diameter is 2~3 times the sheath length, electron density is high. ► Smaller hole diameter is needed to discharge high density plasma at high frequency.