Atomic layer etching processes

1. An etching method comprising:

forming a remote plasma of an inert precursor in a remote plasma region of a processing chamber, wherein the inert precursor is hydrogen or a noble gas;

forming a bias plasma of the inert precursor within a processing region of the processing chamber;

modifying a surface of an exposed material on a semiconductor substrate within the processing region of the processing chamber with plasma effluents of the inert precursor, wherein the remote plasma is maintained during the forming a bias plasma and the modifying a surface of an exposed material;

extinguishing the bias plasma while maintaining the remote plasma subsequent the modifying a surface of an exposed material;

adding an etchant precursor to the remote plasma region to produce etchant plasma effluents;

flowing the etchant plasma effluents to the processing region of the processing chamber; and

removing the modified surface of the exposed material from the semiconductor substrate.

2. The etching method of claim 1 , wherein the inert precursor comprises hydrogen or helium.

3. The etching method of claim 1 , wherein the remote plasma region comprises a region within the processing chamber separated from the processing region by a showerhead.

4. The etching method of claim 3 , wherein the remote plasma region is characterized by a smaller gap between electrodes within the processing chamber than the processing region.

5. The etching method of claim 1 , wherein the method is performed at a chamber operating pressure below about 500 mTorr.

6. The etching method of claim 1 , wherein the etchant precursor comprises a fluorine-containing precursor or a nitrogen-containing precursor.

7. The etching method of claim 1 , wherein the remote plasma comprises a capacitively-coupled plasma.

8. The etching method of claim 7 , wherein the remote plasma is formed at an electrical frequency of greater than or about 40 MHz.

9. The etching method of claim 8 , wherein the remote plasma is formed at an electrical frequency less than or about 80 MHz.

10. The etching method of claim 1 , further comprising:

halting a flow of the etchant precursor while maintaining the remote plasma;

forming a bias plasma in the processing region; and

modifying an additional amount of the exposed material.

11. The etching method of claim 10 , wherein flowing and halting the flow of the etchant precursor is performed for a plurality of cycles.

12. The etching method of claim 11 , wherein the remote plasma is maintained throughout the plurality of cycles.

13. An etching method comprising:

forming a first plasma within a remote plasma region of a processing chamber;

forming a second plasma within a processing region of the processing chamber;

modifying an exposed material on a semiconductor substrate within the processing region of the processing chamber with effluents of the second plasma;

extinguishing the second plasma while maintaining the first plasma;

providing an etchant precursor to the remote plasma region to form etchant plasma effluents;

etching the modified exposed material on the semiconductor substrate;

halting a flow of the etchant precursor while maintaining the first plasma;

reforming the second plasma in the processing region of the processing chamber; and

modifying an additional amount of the exposed material on the semiconductor substrate.

14. The etching method of claim 13 , wherein the etching is performed at a temperature of about 100° C.

15. The etching method of claim 13 , wherein the remote plasma region of the processing chamber is fluidly coupled with, and physically separated from, the processing region of the processing chamber.

16. The etching method of claim 15 , wherein the first plasma is a capacitively-coupled plasma operated at a power level of about 500 W or less.

17. The etching method of claim 15 , wherein the first plasma is a capacitively-coupled plasma operated at a frequency of about 40 MHz or more.

18. An etching method comprising:

striking a plasma of an inert precursor in a remote plasma region of a processing chamber, wherein the remote plasma region is characterized by a first gap between electrodes within the processing chamber, wherein the inert precursor is hydrogen or a noble gas;

striking a plasma of the inert precursor within a processing region of the processing chamber, wherein the processing region of the processing chamber is characterized by a second gap between electrodes within the processing chamber, wherein the second gap between electrodes is greater than the first gap between electrodes, and wherein the striking a plasma of the inert precursor within the processing region occurs while maintaining the plasma of the inert precursor in the remote plasma region;

modifying a surface of a semiconductor substrate within the processing region of the processing chamber with plasma effluents of the inert precursor, while continuing to maintain the plasma of the inert precursor in the remote plasma region;

extinguishing the plasma within the processing region of the processing chamber while maintaining the plasma in the remote plasma region subsequent the modifying the surface of the semiconductor substrate;

flowing an etchant precursor to the remote plasma region to produce etchant plasma effluents;

flowing the etchant plasma effluents to the processing region of the processing chamber; and

removing the modified surface of the semiconductor substrate.

19. The etching method of claim 18 , wherein the plasma formed in the remote plasma region is formed at a frequency of at least about 40 MHz.