Plasma control using dual cathode frequency mixing and controlling the level of polymer formation
Methods for processing a substrate in a processing chamber using dual RF frequencies are provided herein. In some embodiments, a method of processing a substrate includes forming a plasma of a polymer forming chemistry to etch a feature into a substrate disposed on a substrate support in a process chamber while depositing a polymer on at least portions of the feature being etched. A low frequency and a high frequency RF signal are applied to an electrode disposed in the substrate support. The method further includes controlling the level of polymer formation on the substrate, wherein controlling the level of polymer formation comprises adjusting a power ratio of the high frequency to the low frequency RF signal.
1. A method of processing a substrate, comprising:
forming a plasma of a polymer forming chemistry to etch a feature into a substrate disposed on a substrate support in a process chamber while depositing a polymer on at least portions of the feature being etched;
applying a low frequency and a high frequency RF signal to an electrode disposed in the substrate support; and
controlling the level of polymer formation on the substrate to a desired level while etching the feature with the plasma, wherein controlling the level of polymer formation comprises adjusting a power ratio of the high frequency to the low frequency RF signal.
2. The method of claim 1 , further comprising:
monitoring a level of polymer formation during at least a portion of the etch process; and
wherein controlling the level of polymer formation further comprises controlling the level of polymer formation in response to the monitoring.
3. The method of claim 1 , further comprising:
predetermining a level of polymer formation for a particular process; and
adjusting a power ratio of the high frequency to the low frequency RF signal in response to the predetermined polymer formation level.
4. The method of claim 1 , wherein the high frequency RF signal has a frequency between about 13 to about 14 MHz and the low frequency RF signal has a frequency between about 1.8 to about 2.2 MHz.
5. The method of claim 1 , wherein the polymer forming chemistry comprises a fluorocarbon gas.
6. The method of claim 5 , wherein the polymer forming chemistry comprises a fluorocarbon gas mixed with oxygen (O 2 ).
7. The method of claim 1 , wherein the feature is etched into a silicon oxide (SiO 2 ) layer disposed on the substrate and having a patterned mask layer formed thereover.
8. The method of claim 1 , further comprising:
monitoring a sidewall profile of the feature being etched; and
controlling the ratio of the high and low frequency RF signals to control the sidewall profile in response to the monitored sidewall profile.
9. The method of claim 1 , further comprising:
predetermining one or more acceptable sidewall profiles for a particular process recipe; and
controlling the ratio of the high and low frequency RF signals to control the sidewall profile in response to the predetermined one or more sidewall profiles.
10. The method of claim 1 , further comprising:
providing a first power ratio of the high frequency to the low frequency RF signal during a first portion of a process to etch the feature into the substrate with the plasma; and
providing a second power ratio of the high frequency to the low frequency RF signal during a second portion of the process to etch the feature into the substrate with the plasma, the second power ratio different than the first.
11. The method of claim 10 , wherein the first portion of the process is a power ramp up period.
12. The method of claim 1 , further comprising:
providing a third RF signal to the plasma.
13. The method of claim 12 , wherein the third RF signal has a frequency that is greater than or equal to about 60 MHz.
14. The method of claim 12 , wherein the third RF signal is coupled to an overhead electrode disposed opposite the substrate support.
15. The method of claim 12 , further comprising:
providing a magnetic field within the chamber to control a density of the plasma.
16. The method of claim 1 , further comprising:
providing a magnetic field within the chamber to control a density of the plasma.
17. The method of claim 1 , wherein a layer being etched on the substrate comprises amorphous carbon, and wherein the polymer forming chemistry comprises at least one of C x H y (where x, y=0-4) or N x H y (where x, y=0-3).
18. A method of processing a substrate, comprising:
forming a plasma in a process chamber by coupling RF power at a first frequency to a polymer forming process gas disposed in the process chamber;
applying RF power to an electrode disposed in the process chamber at a second frequency and a third frequency; and
controlling a level of polymer formation on a substrate being etched in the process chamber to a desired level while etching the substrate with the plasma, wherein controlling the level of polymer formation comprises adjusting a power ratio of the second frequency to the third frequency.
19. The method of claim 18 , wherein the second frequency is between about 13 to about 14 MHz and the third frequency is between about 1.8 to about 2.2 MHz.
20. The method of claim 19 , wherein the first frequency is greater than or equal to about 60 MHz.