Si precursors for deposition of SiN at low temperatures
Methods and precursors for depositing silicon nitride films by atomic layer deposition (ALD) are provided. In some embodiments the silicon precursors comprise an iodine ligand. The silicon nitride films may have a relatively uniform etch rate for both vertical and the horizontal portions when deposited onto three-dimensional structures such as FinFETS or other types of multiple gate FETs. In some embodiments, various silicon nitride films of the present disclosure have an etch rate of less than half the thermal oxide removal rate with diluted HF (0.5%).
1. A plasma enhanced atomic layer deposition method of depositing a silicon nitride thin film on a substrate in a reaction space, the method comprising a plurality of deposition cycles, each deposition cycle comprising:
(a) introducing a vapor-phase silicon reactant comprising iodine and hydrogen into the reaction space so that a silicon precursor is adsorbed on a surface of the substrate;
(b) exposing the substrate to purge gas and/or vacuum to remove excess silicon reactant and reaction byproducts;
(c) exposing the substrate to reactive species generated by a plasma from a nitrogen precursor; and
(d) exposing the substrate to purge gas and/or vacuum to remove excess reactive species and reaction byproducts;
wherein a thin film comprising silicon nitride of a desired thickness is formed; and
wherein the etch rate of the silicon nitride thin film in 0.5% aqueous HF is less than half the etch rate of thermal silicon oxide in 0.5% aqueous HF.
2. The method of claim 1 , wherein the silicon reactant comprises a precursor having a formula:
H 2n+2−y−z−w Si n I y A z R w
wherein, n=1-10, y=from 1 up to 2n+2−z−w, z=from 0 up to 2n+2−y−w, w=from 0 up to 2n+2−y−z, A is a halogen other than I, and R is an organic ligand and can be independently selected from the group consisting of alkoxides, alkylsilyls, alkyl, substituted alkyl, alkylamines and unsaturated hydrocarbon;
H 2n−2−y−z−w Si n I y A z R w
wherein, the silicon-containing precursor is a cyclic compound, n=3-10, y=from 1 up to 2n−z−w, z=from 0 up to 2n−y−w, w=from 0 up to 2n−y−z, A is a halogen other than I, and R is an organic ligand and can be independently selected from the group consisting of alkoxides, alkylsilyls, alkyl, substituted alkyl, alkylamines and unsaturated hydrocarbon;
H 2n+2−y−z−w Si n I y A z R II
wherein, X is bonded to Si, n=1-10, y=from 0 up to 2n+2−z−w, z=from 0 up to 2n+2−y−w, w=from 1 up to 2n+2−y−z, A is a halogen other than I, and R II is an organic ligand containing I or Br and can be independently selected from the group consisting of I or Br substituted alkoxides, alkylsilyls, alkyls, alkylamines and unsaturated hydrocarbons;
H 2n−2−y−z−w Si n I y A z R II
wherein, the silicon-containing precursor comprises a cyclic compound, n=3-10, y=from 0 up to 2n+2−z−w, z=from 0 up to 2n+2−y−w, w=from 1 up to 2n+2−y−z, A is a halogen other than I, R II is an organic ligand containing I or Br and can be independently selected from the group consisting of I or Br substituted alkoxides, alkylsilyls, alkyls, alkylamines and unsaturated hydrocarbons;
H 2n+2−y−z−w Si n (EH) n−1 I y A z R w
wherein, n=2-10, y=from 1 up to 2n+2−z−w, z=from 0 up to 2n+2−y−w, w=from 0 up to 2n+2−y−z, E is N or S, A is a halogen other than I, R is an organic ligand and can be independently selected from the group consisting of alkoxides, alkylsilyls, alkyl, substituted alkyl, alkylamines and unsaturated hydrocarbon;
H 2n+2−y−z−w Si n (NH) n−1 I y A z R w
wherein, n=2-10, y=from 1 up to 2n+2−z−w, z=from 0 up to 2n+2−y−w, w=from 0 up to 2n+2−y−z, A is a halogen other than I, R is an organic ligand and can be independently selected from the group consisting of alkoxides, alkylsilyls, alkyl, substituted alkyl, alkylamines and unsaturated hydrocarbon;
(H 3−y−z−w I y A z R w Si) 3 —N
wherein, y=from 1 up to 3−z−w, z=from 0 up to 3−y−w, w=from 0 up to 3−y−z, A is a halogen other than I, and R is an organic ligand and can be independently selected from the group consisting of alkoxides, alkylsilyls, alkyl, substituted alkyl, alkylamines and unsaturated hydrocarbon;
H 2n+2−y−z Si n I y A z
wherein, n=1-10, y=from 1 up to 2n+2−z, z=from 0 up to 2n+2−y, and A is a halogen other than I;
H 2n−2−y−z Si n I y A z
wherein the precursor is a cyclic compound, n=3-10, y=from 1 up to 2n−z, z=0 up to 2n−y, and A is a halogen other than I; and
H 2n+2−y Si n I y
wherein, n=1-5 and y=1 up to 2n+2−y.
3. The method of claim 1 , wherein the reactive species comprise hydrogen, hydrogen atoms, hydrogen plasma, hydrogen radicals, N* radicals, NH* radicals or NH 2 * radicals.
4. The method of claim 1 , wherein the reactive species are generated directly above the substrate.
5. The method of claim 1 , wherein the reactive species are generated away from the substrate.
6. The method of claim 5 , wherein a remote plasma generator is used for generating the reactive species.
7. The method of claim 1 , wherein the silicon reactant is selected from the group consisting of HSiI 3 , H 2 SiI 2 , H 3 SiI, H 2 Si 2 I 4 , H 4 Si 2 I 2 , and H 5 Si 2 I.
8. The method of claim 7 , wherein the silicon reactant is H 2 SiI 2 .
9. The method of claim 1 , wherein the method is performed at a temperature between about 300° C. and about 400° C.
10. The method of claim 1 , wherein the nitrogen precursor is selected from the group consisting of NH 3 , N 2 H 4 , an N 2 /H 2 mixture, N 2 , and mixtures thereof.
11. The method of claim 1 , wherein the silicon nitride thin film exhibits a step coverage and pattern loading effect of at least about 80%.
12. The method of claim 1 , wherein the etch rate of the silicon nitride thin film is less than about 1 nm/min in 0.5% aqueous HF.
13. The method of claim 1 , wherein the silicon nitride thin film is deposited during the formation a FinFET.
14. The method of claim 1 , wherein a gas comprising nitrogen is provided to the reaction chamber continuously during steps (a)-(d).
15. The method of claim 1 , wherein the nitrogen precursor is N 2 or a mixture of N 2 and H 2 .
16. A plasma enhanced atomic layer deposition method of depositing a silicon nitride thin film on a three dimensional structure on a substrate in a reaction space, the method comprising a plurality of deposition cycles comprising:
(a) providing a pulse of vapor phase SiI 2 H 2 to the reaction space;
(b) flowing a purge gas through the reaction space to remove excess vapor phase SiI 2 H 2 and reaction byproducts;
(c) flowing nitrogen gas to the reaction space;
(d) generating a plasma in the nitrogen gas in the reaction chamber; and
(e) flowing a purge gas through the reaction space to remove excess nitrogen plasma and reaction byproducts,
wherein the three dimensional structure has vertical and horizontal portions, wherein the silicon nitride thin film has a step coverage of more than about 80% on the three-dimensional structure;
and wherein the silicon nitride film has a uniform etch rate on the vertical and horizontal portions of the three dimensional structure.
17. The method of claim 16 , wherein the purge gas in step (b) comprises nitrogen.
18. The method of claim 16 , wherein the purge gas in step (e) comprises nitrogen.
19. The method of claim 16 , wherein wherein a gas comprising nitrogen is provided to the reaction chamber continuously during steps (a)-(e).
20. The method of claim 16 , wherein generating a plasma in step (d) comprises providing a plasma discharge for a first period of time, extinguishing the plasma discharge for a second period of time, and providing a plasma discharge for a third period of time.
21. The method of claim 16 , wherein an etch rate of the silicon nitride thin film is less than about 5 nm/min in 0.5% aqueous HF.
22. The method of claim 16 , wherein a ratio of an etch rate of the silicon nitride thin film in 0.5% aqueous HF if a vertical portion of the at least one three-dimensional feature to an etch rate of the silicon nitride thin film in 0.5% aqueous HF on a horizontal portion of the at least one three-dimensional feature is less than about 2.
23. The method of claim 16 , wherein the method is performed at a temperature between about 300° C. and about 400° C.
24. The method of claim 16 , wherein the silicon nitride thin film has a step coverage and pattern loading effect of at least about 80%.