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 method of depositing a silicon nitride thin film on a substrate in a reaction space comprising:
(a) introducing a vapor-phase silicon reactant comprising iodine into the reaction space so that the silicon precursor is adsorbed to a surface of the substrate;
(b) removing excess silicon reactant and reaction byproducts;
(c) contacting the adsorbed silicon precursor with a reactive species generated by a plasma from a nitrogen precursor;
(d) removing excess reactive species and reaction byproducts;
wherein steps (a) through (d) are repeated until a silicon nitride film of a desired thickness is formed; and
wherein the adsorbed silicon precursor is not contacted with a reactive species generated by a plasma from Ar.
2 . The method of claim 1 , wherein the silicon reactant comprises a precursor having one of the following formulas:
H 2n+2−y−z−w Si n I y A z R w
wherein, n is from 1 to 10, y is from 1 to 2n+2−z−w, z is from 0 up to 2n+2−y−w, w is 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; and
H 2n−y−z−w Si n I y A z R w
wherein, n is from 3 to 10, y is from 1 up to 2n−z−w, z is from 0 up to 2n−y−w, w is 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.
3 . The method of claim 1 , wherein the reactive species comprises hydrogen, hydrogen atoms, hydrogen plasma, hydrogen radicals, N*, NH* or NH 2 * radicals.
4 . The method of claim 1 , wherein the reaction space is part of a showerhead reactor and comprises a showerhead and a susceptor.
5 . The method of claim 4 , wherein there is a gap of about 0.5 cm to about 5 cm between the showerhead and susceptor.
6 . The method of claim 4 , wherein there is a gap of about 0.8 cm to about 3.0 cm between the showerhead and susceptor.
7 . The method of claim 1 , wherein the reactive species are generated directly above the substrate.
8 . 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.
9 . The method of claim 8 , wherein the silicon reactant is H 2 SiI 2 .
10 . The method of claim 1 , wherein the method is performed at a temperature between about 200° C. and about 400° C.
11 . 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 any mixtures thereof.
12 . The method of claim 1 , wherein the silicon nitride thin film exhibits a step coverage and pattern loading effect of at least about 80%
13 . The method of claim 1 , wherein the silicon nitride thin film is formed on a three-dimensional structure.
14 . The method of claim 13 , wherein the structure comprises a sidewall and top regions and the sidewall wet etch rate (WER) of the silicon nitride film relative to the top region WER is about 1 in 0.5% dHF.
15 . The method of claim 1 , wherein an etch rate of the silicon nitride thin film is less than about 4 nm/min in 0.5% aqueous HF.
16 . The method of claim 1 , wherein nitrogen is used as a carrier gas.
17 . The method of claim 1 , wherein nitrogen is flowed continuously to the reaction space throughout steps (a)-(d).
18 . The method of claim 1 , wherein the silicon nitride thin film is deposited during the formation a FinFET.
19 . A method of depositing a silicon nitride thin film on a substrate comprising:
(a) exposing the substrate to a vapor-phase silicon precursor comprising iodine so that the silicon precursor is adsorbed to a surface of the substrate;
(b) exposing the substrate to a purge gas and/or a vacuum to remove excess silicon precursor and reaction byproducts from the substrate surface;
(c) contacting the adsorbed silicon precursor with species generated by a nitrogen containing plasma; and
(d) exposing the substrate to a purge gas and/or a vacuum to remove the species of a nitrogen containing plasma and reaction byproducts from the substrate surface and from the proximity of the substrate surface;
wherein steps (a) through (d) are repeated until a silicon nitride film of a desired thickness is formed;
and wherein the species generated in step (c) do not comprise species of Ar.
20 . The method of claim 19 , wherein the species are generated directly above the substrate.