Pulsed plasma high aspect ratio dielectric process
Radial distribution of etch rate is controlled by controlling the respective duty cycles of pulsed VHF source power applied to the ceiling and pulsed HF or MF bias power on the workpiece. Net average electrical charging of the workpiece is controlled by providing an electronegative process gas and controlling the voltage of a positive DC pulse on the workpiece applied during pulse off times of the pulsed VHF source power.
1. A method of processing a workpiece supported on a workpiece support facing a ceiling in a reactor chamber, comprising:
introducing into the chamber a polymerizing etch gas, an electronegative gas and an oxidizer gas;
applying source power in the VHF range to the ceiling and applying bias power in the HF or MF range to the wafer support;
pulsing said source power and pulsing said bias power, while establishing a phase lag between source and bias power pulses;
applying a positive D.C. pulse to the workpiece support and/or a negative D.C. pulse to the ceiling during the pulse off time of the source power;
adjusting an average accumulation of electric charge on the workpiece by adjusting the voltage of the D.C. pulse;
adjusting the etch rate by adjusting the phase lag between the pulses of the source and bias power;
adjusting etch rate distribution between center-high and edge-high by adjusting the pulse duty cycles of the VHF source power and of the RF bias power relative to one another, said adjusting etch rate distribution comprising at least one of:
(a) rendering said etch rate distribution more center-high by increasing the pulse duty cycle of said source power relative to the pulse duty cycle of said bias power, and
(b) rendering said etch rate distribution more edge-high by increasing the pulse duty cycle of said bias power relative to the pulse duty cycle of said source power.
2. The method of claim 1 further comprising:
further adjusting said average accumulation of electric. charge on the workpiece by adjusting a flow rate of said electronegative gas.
3. The method of claim 1 further comprising maintaining generally the same pulse rate for both said source power and said bias power.
4. The method of claim 1 further comprising adjusting said phase lag toward 90° to increase etch rate or toward 180° to decrease the etch rate.
5. The method of claim 1 wherein said applying source power comprises applying first and second VHF frequencies to said ceiling, said first VHF frequency being less than said second VHF frequency, said method further comprising:
further adjusting etch distribution by adjusting the power levels of said first and second. VHF frequencies.
6. A method of processing a workpiece supported on a workpiece support facing a ceiling in a reactor chamber, comprising:
introducing into the chamber a polymerizing etch gas, an electronegative gas and an oxidizer gas;
applying source power in the VHF range to the ceiling and applying bias power in the HF or MF range to the wafer support;
pulsing said source power and pulsing said bias power, while establishing respective pulse duty cycles of source power pulses and bias power pulses;
applying a positive D.C. pulse to the workpiece support and/or a negative D.C. pulse to the ceiling during the pulse off time of the source power;
adjusting an average accumulation of electric charge on the workpiece by adjusting the voltage of the D.C. pulse;
adjusting the etch rate distribution between a center high distribution and an edge high distribution by adjusting the duty cycles of said source power and bias power relative to one another, said adjusting etch rate distribution comprising at least one of:
(a) rendering said etch rate distribution more center-high by increasing the pulse duty cycle of said source power relative to the pulse duty cycle of said bias power, and
(b) rendering said etch rate distribution more edge-high by increasing the pulse duty cycle of said bias power relative to the pulse duty cycle of said source power.
7. The method of claim 6 further comprising:
further adjusting said average accumulation of electric charge on the workpiece by adjusting a flow rate of said electronegative gas.
8. The method of claim 6 further comprising maintaining generally the same pulse rate for both said source power and said bias power.
9. The method of claim 6 wherein said applying source power comprises applying first and second VHF frequencies to said ceiling, said first VHF frequency being less than said second VFH frequency, said method further comprising:
further adjusting etch distribution by adjusting the power levels of said first and second VHF frequencies.