US Patent 11227745 Plasma sheath control for RF plasma reactors

Some embodiments include a plasma sheath control system that includes an RF power supply producing an A sinusoidal waveform with a frequency greater than 20 kHz and a peak voltage greater than 1 kV and a plasma chamber electrically coupled with the RF power supply, the plasma chamber having a plurality of ions that are accelerated into a surface disposed with energies greater than about 1 kV, and the plasma chamber produces a plasma sheath within the plasma chamber from the sinusoidal waveform. The plasma sheath control system includes a blocking diode electrically connected between the RF power supply and the plasma chamber and a capacitive discharge circuit electrically coupled with the RF power supply, the plasma chamber, and the blocking diode; the capacitive discharge circuit discharges capacitive charges within the plasma chamber with a peak voltage greater than 1 kV and a discharge time that less than 250 nanoseconds.