Plasma Processing Apparatus Sheath Potential Stabilization

The patent applies preliminary action by ramping down the direct-current power supply before stopping the radio-frequency power supplies. This preparatory step gradually reduces the sheath potential, preventing drastic fluctuations that would otherwise cause particle adhesion to the wafer. The controller executes this sequence by first reducing DC power to a predetermined level, then stopping RF power supplies in a controlled manner.

The patent implements dynamics by transitioning from a static power supply state to a dynamic ramp-down process. The direct-current power supply is not stopped abruptly but is gradually reduced over time, allowing the sheath potential to adapt smoothly. This dynamic adjustment prevents sudden potential changes that would attract particles to the wafer surface.

The patent applies preliminary action by executing a controlled power-down sequence. Before stopping the radio-frequency power supplies, the system first ramps down the direct-current power supply to a predetermined level. This preparatory step ensures that when RF power is subsequently stopped, the sheath potential does not fluctuate drastically, thereby preventing particle adhesion while maintaining efficient process timing.

The patent implements periodic action through a structured multi-stage power supply cessation sequence. The controller systematically stops power supplies in a specific order and timing: first ramping down DC power, then stopping RF power supplies at predetermined intervals. This periodic, controlled approach balances process efficiency with particle adhesion prevention.