Measured energy distributions of ions driven by an asymmetrically pulsed bias during magnetron sputtering

A retarding field analyzer is used to obtain a measure of the energy of the ions extracted from a direct current discharge driven by a low-frequency (100–100 kHz) asymmetrically pulsed bias. Measurements are made to illustrate the effects of the pulse’s shape (frequency and duty) on the distribution in the energies of the ions extracted from the plasma. Ion energy distributions are computed by a quasistatic treatment of the ion’s response to the measured wave form of the pulsed electrode. Comparisons are made between the measured and calculated ion energy distributions to demonstrate the effectiveness of the technique used to calculate the ion energy distribution. Expressions are then produced for the time scales in which the quasistatic treatment of the sheath remains a valid approximation to predict the energy distribution of the ions.