Atomic layer deposition and etching of transition metal dichalcogenide thin films
Vapor deposition methods for depositing transition metal dichalcogenide (TMDC) films, such as rhenium sulfide thin films, are provided. In some embodiments TMDC thin films are deposited using a deposition cycle in which a substrate in a reaction space is alternately and sequentially contacted with a vapor phase transition metal precursor, such as a transition metal halide, a reactant comprising a reducing agent, such as NH 3 and a chalcogenide precursor. In some embodiments rhenium sulfide thin films are deposited using a vapor phase rhenium halide precursor, a reducing agent and a sulfur precursor. The deposited TMDC films can be etched by chemical vapor etching using an oxidant such as O 2 as the etching reactant and an inert gas such as N 2 to remove excess etching reactant. The TMDC thin films may find use, for example, as 2D materials.
1. A method, comprising:
depositing, via two or more sequential deposition cycles, a thin film comprising a transition metal dichalcogenide on a substrate in a reaction chamber, wherein each of the two or more sequential deposition cycles comprises sequentially:
contacting the substrate with a vapor-phase first reactant comprising a transition metal precursor;
contacting the substrate with a vapor-phase second reactant consisting of a reducing agent and an insert carrier gas;
after contacting the substrate with the vapor-phase second reactant and prior to contacting the substrate with a vapor-phase third reactant consisting of a chalcogenide precursor and the inert carrier gas, removing excess vapor-phase second reactant from the reaction chamber; and
after removing the excess vapor-phase second reactant from the reaction chamber, contacting the substrate with the vapor-phase third reactant,
wherein the inert carrier gas is different than the reducing agent and the chalcogenide precursor.
2. The method of claim 1 , wherein the transition metal dichalcogenide comprises Mo, W, Re, Ta, Zr, Hf, Sn, Nb, Ni or V.
3. The method of claim 1 , wherein the transition metal dichalcogenide comprises ReS2, TaS2, ZrS2, HfS2, SnS2 ReTe2, TaTe2, ZrTe2, HfTe2, SnTe2 ReSe2, TaSe2, ZrSe2, HfSe2 or SnSe2.
4. The method of claim 1 , wherein the vapor-phase first reactant comprises one or more of Mo, W, Re, Ta, Zr, Hf, Sn, Nb, Ni and V.
5. The method of claim 1 , wherein the vapor-phase first reactant comprises a transition metal halide.
6. The method of claim 1 , wherein the chalcogenide precursor comprises sulfur.
7. The method of claim 1 , wherein the chalcogenide precursor comprises H2S, H2S2, H2Se, H2Se2, H2Te, H2Te2, (NH4) 2S, (CH3) 2Se, (CH3) 2Te, or elemental or atomic Se, Te or S.
8. The method of claim 1 , wherein the reducing agent consists of NH3, N2H4, nitrogen plasma, excited species of nitrogen, nitrogen radicals, atomic nitrogen, silane, borane, or hydrazine species.
9. The method of claim 1 , wherein the transition metal precursor is a rhenium halide.
10. The method of claim 1 , wherein the reducing agent consists of NH3.
11. The method of claim 1 , wherein the chalcogenide precursor has one or more H—S bonds.
12. The method of claim 1 , wherein the chalcogenide precursor consists of H2S.
13. The method of claim 1 , wherein the thin film comprises ReS2.
14. The method of claim 1 , wherein the thin film is deposited on a three-dimensional structure with step coverage of greater than 90%.
15. The method of claim 1 , wherein each of the two or more sequential deposition cycles further comprises:
prior to contacting the substrate with the vapor-phase second reactant and prior to contacting the substrate with the vapor-phase third reactant, removing excess vapor-phase first reactant from the reaction chamber.
16. The method of claim 1 , wherein each of the two or more sequential deposition cycles further comprises:
after contacting the substrate with the vapor-phase third reactant, removing excess vapor-phase third reactant from the reaction chamber.
17. A cyclic vapor deposition method, comprising:
depositing, via a plurality of deposition cycles, a thin film comprising ReS2 on a substrate in a reaction chamber, wherein each of the plurality of deposition cycles comprises sequentially:
contacting the substrate in the reaction chamber with a first vapor-phase reactant comprising a rhenium halide;
contacting the substrate with a second vapor-phase reactant consisting of a reducing agent and an inert carrier gas;
removing excess second vapor-phase reactant from the reaction chamber; and
contacting the substrate with a third vapor-phase reactant consisting of a chalcogenide precursor and the inert carrier gas,
wherein the inert carrier gas is different than the reducing agent and the chalcogenide precursor.
18. The method of claim 17 , wherein the first vapor-phase reactant consists of ReCl5, and the second vapor-phase reactant consists of NH3.
19. The method of claim 17 , wherein the plurality of deposition cycles additionally comprises removing excess first vapor-phase reactant from the reaction chamber after contacting the substrate with the first vapor-phase reactant and prior to contacting the substrate with the second vapor-phase reactant.
20. The method of claim 17 , wherein the plurality of deposition cycles additionally comprises removing excess vapor-phase third reactant from the reaction chamber after contacting the substrate with the vapor-phase third reactant.