Atomic layer etching processes
Atomic layer etching (ALE) processes are disclosed. In some embodiments, the methods comprise at least one etch cycle in which the substrate is alternately and sequentially exposed to a first vapor phase non-metal halide reactant and a second vapor phase halide reactant. In some embodiments both the first and second reactants are chloride reactants. In some embodiments the first reactant is fluorinating gas and the second reactant is a chlorinating gas. In some embodiments a thermal ALE cycle is used in which the substrate is not contacted with a plasma reactant.
1. A method of etching a film on a substrate by chemical atomic layer etching in a reaction chamber, the method comprising one or more etching cycles, each cycle comprising:
exposing the substrate to a first vapor-phase non-metal halide reactant; and
subsequently exposing the substrate to a second vapor-phase reactant comprising a non-metal oxyhalide, wherein the substrate is not contacted with a plasma reactant during the etching cycle and wherein up to a monolayer of material is removed from the film in each etching cycle.
2. The method of claim 1 , wherein the first vapor-phase non-metal halide reactant comprises from 2 to 6 halides and the second vapor-phase reactant comprises from 2 to 6 halides.
3. The method of claim 2 , wherein the first vapor-phase non-metal halide reactant comprises the same halides as the second vapor-phase reactant.
4. The method of claim 1 , wherein the first vapor-phase non-metal halide reactant and the second vapor phase reactant both comprise the same number of halides.
5. The method of claim 1 , wherein the first vapor-phase non-metal halide reactant comprises more halides than the second vapor-phase reactant.
6. The method of claim 1 , wherein the second vapor-phase reactant comprises more halides than the first vapor-phase non-metal halide reactant.
7. The method of claim 1 , wherein the first vapor-phase non-metal halide reactant comprises a semi-metal halide, an organic oxyhalide, or a carbon based halide.
8. The method of claim 1 , wherein the etch cycle additionally comprises exposing the substrate to one or more additional reactants.
9. The method of claim 1 , wherein the etch cycle is repeated two or more times in a row.
10. The method of claim 1 , wherein the first vapor-phase non-metal halide reactant has the formula NX a , where X is chlorine, bromine, fluorine, or iodine; N is nitrogen, phosphorus, sulfur, selenium, silicon, tellurium, antimony, boron, germanium, or carbon; and a is greater than 1 and less than 7.
11. The method of claim 1 , wherein the first vapor-phase non-metal halide reactant comprises SCl 2 , SeCl 4 , SeF 4 , SeF 6 , SeCl 2 , S 2 Cl 2 , Se 2 Cl 2 , SiCl 4 , SbCl 3 , SbCl 5 , BCl 3 , or GeCl 4 .
12. The method of claim 1 , wherein the non-metal oxyhalide comprises SeO 2 Cl 2 , SO 2 Cl 2 , or SeOCl 2 .
13. The method of claim 1 , wherein the first vapor-phase non-metal halide comprises NCl 2 F, NF 2 Cl, NOF or NO 2 F.
14. The method of claim 1 , wherein the first vapor-phase non-metal halide comprises CCl 4 or CBr 4 or has the general formulae CX a Y 4-a , and C n X a Y (2n+2−a) , where in X is any halide and ‘a’ can be greater than 1, Y is a non-metal, and n can be greater than or equal to 1.
15. The method of claim 1 , further comprising removing excess first reactant from the reaction chamber after contacting the substrate with the first reactant and prior to contacting the substrate with the second reactant.
16. A method of etching a film on a substrate in a reaction chamber by chemical atomic layer etching, the method comprising one or more etching cycles, each cycle comprising a first phase comprising exposing the substrate to a first vapor-phase non-metal halide reactant, wherein the substrate is not contacted with a plasma reactant during the etching cycle, and wherein each etching cycle removes material from the film, wherein the first vapor-phase non-metal halide reactant has the formula NX a , where X is chlorine, bromine, fluorine, or iodine; N is nitrogen, phosphorous, sulfur, selenium, silicon, tellurium, antimony, boron, germanium or carbon; and a is a stoichiometric indicator.
17. A method of etching a film on a substrate in a reaction chamber by chemical atomic layer etching, the method comprising one or more etching cycles, each cycle comprising a first phase comprising exposing the substrate to a first vapor-phase non-metal halide reactant, wherein the substrate is not contacted with a plasma reactant during the etching cycle, and wherein each etching cycle removes material from the film, wherein the etch cycle additionally comprises a second phase in which the substrate is exposed to an oxygen reactant, including H 2 O 2 , HCOOH, H 2 O, O 2 and O 3 .
18. A method of etching a film on a substrate in a reaction chamber by chemical atomic layer etching, the method comprising one or more etching cycles, each cycle comprising a first phase comprising exposing the substrate to a first vapor-phase non-metal halide reactant, wherein the substrate is not contacted with a plasma reactant during the etching cycle, and wherein each etching cycle removes material from the film, wherein the etch cycle additionally comprises a second phase in which the substrate is exposed to a ligand exchanger.
19. The method of claim 18 , wherein the ligand exchanger comprises Hacac, TMA, or Sn(acac) 2 .