Patent ID: 11942307
Assignee: TOKYO ELECTRON LIMITED
Field: Electrical machinery, apparatus, energy (Electrical engineering)
Classification: CPC H | IPC H

Claim 14:
15. A method for plasma processing comprising:
sustaining a plasma in a plasma processing chamber, the plasma processing chamber comprising a first radio frequency (RF) electrode and a second RF electrode, wherein sustaining the plasma comprises:
coupling an RF signal source to the first RF electrode; and
applying a bias signal between the first RF electrode and the second RF electrode, the bias signal having a bipolar DC (B-DC) waveform being a difference of a first unipolar DC (U-DC) waveform and a second unipolar DC waveform, the polarity of the first U-DC waveform being same as the polarity of the second U-DC waveform, and wherein applying the bias signal comprises:
coupling applying a first U-DC signal to the first RF electrode, the first U-DC signal having the first U-DC waveform comprising a first plurality of U-DC pulses, wherein each of the first plurality of U-DC pulses comprises:
a first U-DC pulse width during which the pulse has a first bias polarity relative to a reference potential; and
a first U-DC pulse separation time during which the pulse has a neutral bias polarity substantially equal to the reference potential;

applying a second U-DC signal to the second RF electrode, the second U-DC signal having the second U-DC waveform comprising a second plurality of U-DC pulses, wherein each of the second plurality of U-DC pulses comprises:
a second U-DC pulse width during which the pulse has the first bias polarity relative to the reference potential and;
a second U-DC pulse separation time during which the pulse has a neutral bias polarity substantially equal to the reference potential; and

synchronizing the first U-DC signal with the second U-DC signal, wherein the synchronizing is delaying the U-DC pulses of the first U-DC signal by a constant U-DC delay time from the U-DC pulses of the second U-DC signal.