Synchronous embedded radio frequency pulsing for plasma etching
Methods for etching a substrate are provided herein. In some embodiments, a method of etching a substrate may include generating a plasma by providing only a first RF signal having a first frequency and a first duty cycle; applying only a second RF signal to bias the plasma towards the substrate, wherein the second RF signal has the first frequency and a second duty cycle different than the first duty cycle; adjusting a phase variance between the first and second RF signals to control an ion energy distribution in the plasma; and etching the substrate with the plasma.
1. A method of etching a substrate, comprising:
generating a plasma by providing only a first RF signal having a first frequency and a first duty cycle;
applying only a second RF signal to bias the plasma towards the substrate, wherein the second RF signal has the first frequency and a second duty cycle different than the first duty cycle, and wherein an “on” portion of the second RF signal is entirely embedded with an “on” portion of the first RF signal and does not overlap an “off” portion of the first RF signal;
adjusting a phase variance between the first and second RF signals to control an ion energy distribution in the plasma, wherein adjusting the phase variance further includes controlling a phase lag of the second RF signal relative to the first RF signal to reduce ion bombardment damage on the substrate, and wherein the “on” portion of the second RF signal remains entirely embedded within the “on” portion of the first RF signal and does not overlap the “off” portion of the first RF signal after the phase lag of the second RF signal has been adjusted; and
etching the substrate with the plasma.
2. The method of claim 1 , where a pulse frequency of each of the first and second RF signals is about 10 Hz to about 100 kHz.
3. The method of claim 2 , wherein the pulse frequency of each of the first and second RF signals is the same.
4. The method of claim 1 , wherein the first and second duty cycles are about 1 to about 99 percent.
5. The method of claim 4 , wherein the first duty cycle is about 75 percent and the second duty cycle is about 50 percent.
6. The method of claim 5 , wherein a phase difference between the first and second RF signals ranges from about greater than about 0 degrees to less than about 90 degrees.
7. The method of claim 5 , wherein the first RF signal is provided at a first power of about 100 to about 3000 watts and the second RF signal is provided at a second power of about 100 to about 3000 watts.
8. The method of claim 1 , wherein the first frequency is about 400 kHz to about 27 MHz.
9. The method of claim 1 , wherein adjusting the phase variance further comprises:
controlling a phase lag of the second RF signal relative to the first RF signal to control the ion energy distribution in the plasma.
10. The method of claim 9 , wherein the phase lag is up to about 270 degrees.
11. The method of claim 1 , wherein the substrate is disposed in a processing volume of an inductively coupled plasma etching reactor having the first RF signal coupled to one or more inductive coils disposed above the processing volume and the second RF signal coupled to an electrode disposed in a substrate support of the reactor.
12. A method of etching a substrate disposed on a substrate support in the processing volume of an inductively coupled plasma etching reactor having one or more inductive coils disposed above the substrate support and external of the processing volume and an electrode disposed in the substrate support, comprising:
generating a plasma by providing only a first RF signal having a first frequency and a first duty cycle;
applying only a second RF signal to bias the plasma towards the substrate, wherein the second RF signal has the first frequency and a second duty cycle different than the first duty cycle, wherein an “on” portion of the second RF signal is entirely embedded within an “on” portion of the first RF signal and does not overlap an “off” portion of the first RF signal;
adjusting a phase variance between the first and second RF signals to control an ion energy distribution in the plasma, wherein adjusting the phase variance further includes controlling a phase lag of the second RF signal relative to the first RF signal to reduce ion bombardment damage on the substrate, and wherein th “on” portion of the second RF signal remains entirely embedded within the “on” portion of the first RF signal and does not overlap the “off” portion of the first RF signal after the phase lag of the second RF signal has been adjusted; and
etching the substrate with the plasma.
13. The method of claim 12 , where a pulse frequency of each of the first and second RF signals is about 10 Hz to about 100 kHz, and wherein the pulse frequency of each of the first and second RF signals is the same.
14. The method of claim 13 , wherein the first and second duty cycles are about 1 to about 99 percent.
15. The method of claim 14 , wherein the first duty cycle is about 75 percent and the second duty cycle is about 50 percent and wherein a phase difference between the first and second RF signals ranges from about greater than about 0 degrees to less than about 90 degrees.
16. The method of claim 14 , wherein the first RF signal is provided at a first power of about 100 to about 3000 watts and the second RF signal is provided at a second power of about 100 to about 3000 watts.
17. The method of claim 14 , wherein adjusting the phase variance further comprises:
controlling a phase lag of the second RF signal relative to the first RF signal to control the ion energy distribution in the plasma.
18. The method of claim 17 , wherein the phase lag ranges from about 0 to about 270 degrees.