High energy atomic layer etching
Methods and apparatus for performing high energy atomic layer etching are provided herein. Methods include providing a substrate having a material to be etched, exposing a surface of the material to a modification gas to modify the surface and form a modified surface, and exposing the modified surface to an energetic particle to preferentially remove the modified surface relative to an underlying unmodified surface where the energetic particle has an ion energy sufficient to overcome an average surface binding energy of the underlying unmodified surface. The energy of the energetic particle used is very high; in some cases, the power applied to a bias used when exposing the modified surface to the energetic particle is at least 150 eV.
1. A method of processing a substrate, the method comprising:
providing a substrate comprising a material to be etched;
exposing a surface of the material to be etched to a modification gas to modify the surface and form a modified surface in a self-limiting manner; and
exposing the modified surface to an energetic particle by applying a bias voltage of at least between about 500 V and about 1500 V to preferentially remove the modified surface relative to an underlying unmodified surface.
2. The method of claim 1 , wherein ion energy of energetic particle is sufficient to break bonds of the underlying unmodified surface.
3. The method of claim 1 , wherein the energetic particle is delivered in temporally separated doses having a duty cycle between about 1% and about 10%.
4. The method of claim 1 , wherein the energetic particle removes an amount of the modified surface, and the amount of the removed modified surface is given by an equation
θ
(
t
)
=
1
-
exp
(
-
Y
·
F
·
t
d
)
wherein Y is ion yield of the energetic particle, F is flux of energetic particle, t is duration of the exposing of the modified surface to the energetic particle, and d is surface density of material to be etched.
5. The method of claim 1 , wherein the energetic particle does not significantly sputter underlying unmodified material.
6. The method of claim 4 , wherein the modified surface is exposed to the energetic particle for a duration is sufficient to remove the modified surface in a self-limited manner.
7. A method of processing a substrate, the method comprising:
providing a substrate comprising a material to be etched;
exposing a surface of the material to be etched to a modification gas to modify the surface and form a modified surface; and
exposing the modified surface to an attenuated dose of energetic particles,
wherein a dose without attenuation has an energy greater than a surface binding energy for the material to be etched when delivered continuously to the modified surface.
8. The method of claim 7 , wherein the dose is attenuated by varying ion flux of the energetic particles.
9. The method of claim 7 , wherein the dose is attenuated by varying duration of the modified surface being exposed to the energetic particles.
10. The method of claim 7 , wherein the attenuated dose comprises two or more temporally separated pulses of the energetic particles to the modified surface to remove the at least some of the modified surface.
11. The method of claim 7 , wherein the dose is attenuated by varying acceleration of ions in the energetic particles to the modified surface.
12. The method of claim 7 , wherein the dose is attenuated by varying bias voltage applied to a substrate support holding the substrate for directionally delivering the energetic particles to the modified surface.
13. A method of processing a substrate, the method comprising:
exposing the substrate to a modification gas to modify a surface of the substrate to form a modified surface;
exposing the modified surface of the substrate to a removal gas; and
providing a plurality of temporally separated pulses of energy generated from an activation source during the exposing the modified surface to the removal gas to remove at least some of the modified surface from the substrate,
wherein voltage applied to bias the substrate is pulsed using a duty cycle between about 1% and about 20%.
14. The method of claim 13 , further comprising repeating exposing the substrate to the modification gas and exposing the modified surface to the removal gas in two or more cycles, wherein the plurality of temporally separated pulses of energy is provided during the exposing the modified surface to the removal gas in each cycle.
15. The method of claim 14 , wherein the plurality of temporally separated pulses of energy comprises at least 100 temporally separated pulses of energy per cycle.
16. The method of claim 13 , wherein the temporally separated pulses of energy is sufficient to remove the modified surface and insufficient to physically sputter the modified surface.
17. The method of claim 13 , wherein the energy provided is defined by a bias window of a minimum voltage applied to the substrate during the exposing of the modified surface to the removal gas sufficient to remove the modified surface, and a maximum voltage applied to the substrate during the exposing of the modified surface to the removal gas insufficient to sputter the modified surface.
18. The method of claim 13 , wherein the activation source comprises two or more sources.
19. The method of claim 13 , wherein the activation source is selected from the group consisting of radio frequency plasma, bias applied to the substrate, ultraviolet radiation, photons, and combinations thereof.
20. The method of claim 13 , wherein the activation source comprises voltage applied to bias the substrate.
21. The method of claim 20 , wherein the voltage is at least between about 500 V and about 1500 V.
22. The method of claim 13 , wherein the activation source comprises radio frequency plasma.