Particle-in-cell modeling of dual-frequency capacitively coupled plasma excited using dual-plateau tailored voltage waveform

Low-pressure capacitively coupled plasmas (CCP) have been used extensively in the semiconductor industry, especially for dielectric etch due to their ability to generate energetic ions for anisotropic etching. Dual-frequency CCP has been introduced as an approach to achieve individual control over ion flux and energy. With two sinusoidal RF voltages applied to the electrode, the ion energy distribution function (IEDF) usually demonstrates bimodal behavior. As the ion transit time is usually longer than the RF period, a wide intermediate energy spectrum is observed in the IEDF, which may negatively impact ion-surface interaction during the etch process. Alternative RF waveforms have been used to address this issue. The tailored non-sinusoidal waveform shows promising results due to the relatively constant sheath voltage. In this study, we conduct 1d3v particle-in-cell modeling of a dual-frequency CCP excited with a 27.12 MHz HF sinusoidal source power and a 271.2kHz LF dual-plateau tailored bias voltage. The voltage ratios of the first and second plateau, and the on-time of the second plateau of the tailored voltage waveform are varied. Their controllability on the IEDF and the different plasma dynamics are studied. Simulations have been done for electronegative O₂ plasmas.