Thermal atomic layer etching processes

1. A method of etching a film on a substrate in a reaction chamber, the method comprising one or more etching cycles, each etching cycle comprising:

exposing the substrate to at least two vapor-phase halide reactants;

subsequently exposing the substrate to a third, different vapor-phase reactant, such that volatile species comprising one or more atoms from the film are formed; and

removing volatile species from the reaction chamber, wherein the substrate is not contacted with a plasma reactant during the etching cycle.

2. The method of claim 1 , wherein the substrate is not contacted with HF during the etching cycle.

3. The method of claim 1 , wherein exposing the substrate to at least two vapor-phase halide reactants comprises flowing the two or more vapor-phase halide reactants continuously into the reaction space during the etching cycle.

4. The method of claim 1 , wherein exposing the substrate to at least two vapor-phase halide reactants comprises flowing the two or more vapor-phase halide reactants sequentially into the reaction chamber.

5. The method of claim 1 , wherein the film comprises W, Co, Cu, Al, Fe, Pt, Au, TiN, TiO 2 , TaN, SiN, AlO 2 , Al 2 O 3 , ZrO 2 , WO 3 , AlN, or HfO 2 .

6. The method of claim 1 , wherein the etching cycle is repeated two or more times.

7. The method of claim 1 , wherein the two or more vapor-phase halide reactants comprise a metal halide reactant, a non-metal halide reactant, or a semi-metal halide reactant.

8. The method of claim 1 , wherein at least one of the two or more vapor-phase halide reactants comprises one or more of V, Re, Mo, Nb, Te, W, Ta, Sn, and Sb.

9. The method of claim 7 , wherein the at least one of the two or more vapor phase halide reactant comprises VF 5 , NbF 5 , NbCl 5 , MoF 6 , MoCl 6 , MoF 5 , TeF 6 , SbF 5 , AsF 5 , or ReF 6 .

10. The method of claim 1 , wherein the third vapor-phase reactant comprises CS 2 , pyridine, tetrahydrofuran, DMSO, tetrahydrothiophene.

11. The method of claim 1 , wherein the third vapor-phase reactant comprises BCl 3 , BF 3 or AlCl 3 .

12. The method of claim 1 , wherein the third vapor-phase reactant comprises a nitrile, an isonitrile, a thiocyanate, an isothiocyanate, a diamine, a diketone, a dithione or an atrane compound.

13. The method of claim 1 , wherein the third vapor-phase reactant comprises a carboxylic acid or an alcohol.

14. The method of claim 1 , wherein the third vapor-phase reactant comprises a heterocyclic reactive compound comprising one or more of oxygen, boron, sulfur, or nitrogen.

15. The method of claim 1 , wherein the two or more halide reactants are selected from SeF 4 , SeF 6 , trichloromethanesulfinyl chloride, BF 2 acac, NbF 5 , SbF 5 , TeF 6 , POCl 3 , fumaryl chloride, MoOF 4 , ReOF 4 , ReOF 5 , fluoroantimony salts, CCl 4 , CHCl 3 , CCl 3 Br, CCl 2 Br 2 and CHCl 5 .

16. The method of claim 1 , wherein the wherein the two or more vapor-phase halide reactants comprise an oxyhalide or a sulfonic acid halide.

17. The method of claim 1 , wherein the two or more vapor-phase halide reactants comprise a sulfenyl halide, a sulfonyl halide, a selenenyl halide or a sulfinyl halide.

18. The method of claim 1 , wherein the two or more vapor-phase halide reactants comprise: nitrogen, sulfur and a halide; phosphorous, oxygen and a halide; or sulfur, carbon and a halide.

19. The method of claim 1 , wherein the substrate comprises two different films the etching cycle selectively etches one of the films relative to the other.

20. The method of claim 1 , wherein the temperature of the substrate during the etching cycle is 150° C. to 600° C.

21. The method of claim 1 , wherein the substrate is exposed to the two or more vapor-phase halide reactants for a period of time between 0.01 s and 100 s.

22. The method of claim 1 , wherein the pressure in the reaction chamber is between 10E-9 torr and 760 torr during the etching cycle.