The effects of bias voltage waveforms on self-bias in radio frequency capacitively coupled plasmas using particle trajectory analysis

In radio frequency (RF) capacitively coupled plasma (CCP) systems, the blocking capacitor is essential because it literally blocks the direct current (DC) component from the RF power supply ensuring that only the alternating current (AC) is applied to the plasma. It prevents the accumulation of DC bias and also protects the RF power supply by blocking the DC components from plasma chamber. Using the blocking capacitor inevitably leads to the self-bias effect due to the difference in mobility between electrons and ions. The higher mobility of electrons than ions results in the imbalance of charge distribution in plasma sheath near the electrodes. This charge imbalance forms the negative DC voltage bias across the plasma sheath and controls the ion flux and the ion energy through the negative DC self-bias voltage. In this study, we discuss how the self-bias from different waveforms affects plasma characteristics in RF CCP systems using a two-dimensional particle-in-cell Monte Carlo collision (PIC-MCC) simulation. The RF sources are bipolar and unipolar dual frequency pulses. Also, we investigate the effect of split electrodes on the DC bias.