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 three-dimensional structure 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 into the reaction space so that a silicon precursor is adsorbed on a surface of the substrate;
(b) removing excess silicon reactant from the substrate surface by moving the substrate;
(c) exposing the substrate surface to reactive species generated by a plasma from a nitrogen precursor; and
(d) removing excess reactive species from the substrate surface by moving the substrate;
wherein the deposition cycle is repeated to form the silicon nitride thin film; and
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.
2. The method of claim 1 , wherein the reactive species comprise hydrogen, hydrogen atoms, hydrogen plasma, hydrogen radicals, N* radicals, NH* radicals or NH2* radicals.
3. The method of claim 1 , wherein the reactive species are generated directly above the substrate.
4. The method of claim 1 , wherein a remote plasma generator is used for generating the reactive species.
5. The method of claim 1 , wherein the silicon reactant is H 2 SiI 2 .
6. The method of claim 1 , wherein the method is performed at a temperature between about 300° C. and about 400° C.
7. 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.
8. The method of claim 1 , wherein the nitrogen precursor is N 2 or a mixture of N 2 and H 2 .
9. The method of claim 1 , wherein the silicon nitride thin film exhibits a pattern loading effect of at least about 80%.
10. 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.
11. The method of claim 1 , wherein the silicon nitride thin film is deposited during the formation a FinFET.
12. The method of claim 1 , wherein a gas comprising nitrogen is provided to the reaction chamber continuously during steps (a)-(d).
13. A plasma enhanced atomic layer deposition method of depositing a silicon nitride thin film on a three-dimensional structure on a surface of a substrate in a reaction space, the method comprising a plurality of deposition cycles comprising:
(a) providing a pulse of vapor phase silicon reactant comprising silicon, iodine and hydrogen to the reaction space;
(b) removing excess vapor phase silicon reactant from the substrate surface by moving the substrate;
(c) flowing nitrogen gas to the reaction space;
(d) generating a plasma in the nitrogen gas in the reaction chamber; and
(e) removing excess plasma from the substrate surface by moving the substrate,
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.
14. The method of claim 13 , wherein the silicon reactant is H 2 SiI 2 .
15. The method of claim 13 , wherein the nitrogen precursor is N 2 or a mixture of N 2 and H 2 .
16. The method of claim 13 , wherein a gas comprising nitrogen is provided to the reaction chamber continuously during steps (a)-(e).
17. The method of claim 13 , wherein a ratio of an etch rate of the silicon nitride thin film in 0.5% aqueous HF on a vertical portion of the three-dimensional structure to an etch rate of the silicon nitride thin film in 0.5% aqueous HF on a horizontal portion of the three-dimensional structure is less than about 2.
18. The method of claim 13 , wherein the silicon nitride thin film has a uniform etch rate on vertical and horizontal portions.
19. The method of claim 13 , wherein the silicon nitride film has a pattern loading effect of at least about 80%.