Ion current droop compensation
In some embodiments, a high voltage power supply is disclosed that provides a plurality of high voltage pulses without any voltage droop between two subsequent pulses. In some embodiments, a high voltage power supply is disclosed that provides a waveform of voltage versus time having a plurality of high voltage pulses having a voltage greater than 1 kV and with a substantially flat portion between pulse. In some embodiments, a high voltage power supply is disclosed that includes a snubber with a snubber resistor having a resistance of about 7.5 mΩ-1.25Ω; and a snubber capacitor having a capacitance of about 2 μF-35 μF.
1. A power supply system comprising:
an RF driver that produces an RF signal with an RF frequency;
a nanosecond pulser that produces high voltage pulses with a pulse repetition frequency that is less than the RF frequency, a pulse width, and a peak voltage greater than 2 kV, the nanosecond pulser comprising a snubber circuit including:
a snubber resistor having a resistance of about 7.5 mΩ-1.25Ω; and
a snubber capacitor having a capacitance of about 2 μF-35 μF; and
a filter circuit disposed between the RF driver and the plasma chamber.
2. The power supply according to claim 1 , wherein the nanosecond pulser produces square waves.
3. The power supply according to claim 1 , wherein the filter circuit includes a filter inductor having an inductance of about 0-2.5 μH.
4. The power supply according to claim 1 , wherein the power supply has a stray inductance less than about 800 nH.
5. The power supply according to claim 1 , wherein the pulse width has a duration of about 100-250 ns.
6. The power supply according to claim 1 , wherein the voltage between two consecutive pulses without the RF signal changing less than 1 V/ns.
7. The power supply according to claim 1 , wherein the average voltage between two consecutive pulses changes less than 1 V/ns.
8. The power supply according to claim 1 , wherein the power supply outputs a waveform having an RF signal in between each of a plurality of high voltage pulses.
9. A semiconductor processing system comprising:
a plasma chamber; and
the power supply according to claim 1 coupled with the plasma chamber to introduce the RF signal and the drive pulses into the plasma chamber.
10. The power supply according to claim 9 , wherein the plasma chamber has an inductance less than about 20 nH.
11. The power supply according to claim 9 , wherein the chamber includes a chuck having a capacitance less than about 10 nF.