Deposition of SiN
Methods and precursors for forming silicon nitride films are provided. In some embodiments, silicon nitride can be deposited by atomic layer deposition (ALD), such as plasma enhanced ALD. In some embodiments, deposited silicon nitride can be treated with a plasma treatment. The plasma treatment can be a nitrogen plasma treatment. In some embodiments the silicon precursors for depositing the silicon nitride 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%). In some embodiments, a method for depositing silicon nitride films comprises a multi-step plasma treatment.
1. A method of forming a SiN thin film on a surface of a substrate in a reaction space comprising:
contacting the substrate with a silicon precursor comprising SiI 2 H 2 to provide a first silicon species adsorbed on the surface of the substrate;
contacting the substrate comprising the first silicon species adsorbed on the surface with a first plasma comprising activated hydrogen species thereby forming SiN on the substrate; and
contacting the substrate comprising SiN with a second plasma formed from a gas comprising N 2 and a noble gas, wherein the second plasma is substantially free of hydrogen-containing species.
2. The method of claim 1 , wherein the second plasma comprises Ar or He species.
3. The method of claim 1 , wherein the activated hydrogen species comprises at least one of hydrogen atoms, hydrogen plasma, hydrogen radicals, N* radicals, NH* radicals and NH 2 * radicals.
4. The method of claim 1 , wherein the SiN thin film is formed on a three-dimensional structure comprising a sidewall and a top region and wherein a ratio of a wet etch rate (WER) of the SiN thin film on the sidewall to a wet etch rate (WER) of the SiN thin film on the top region is from 0.75 to 1.5 in 0.5% dHF.
5. The method of claim 1 , wherein the SiN thin film has a blanket wet etch rate in dHF relative to the wet etch rate of thermal silicon oxide of less than 0.5.
6. The method of claim 1 , wherein the SiN thin film has a blanket wet etch rate of less than 5 nm/min in 0.5% dHF.
7. The method of claim 1 , wherein the amount of etching of the SiN thin film is one to two times less than the amount of etching of a thermal SiO 2 film in a 0.5% dHF dip process.
8. The method of claim 1 , wherein the first plasma is generated using a first power and the second plasma is generated using a second power that is different from the first power.
9. The method of claim 8 , wherein the second power is greater than the first power.
10. The method of claim 9 , wherein the second power is up to 900% of the first power.
11. The method of claim 8 , wherein the first power is from 50 W to 600 W.
12. The method of claim 8 , wherein the second power is from 100 W to 1000 W.
13. The method of claim 1 , wherein the first plasma has a plasma energy of less than 2500 W*s.
14. The method of claim 1 , wherein the second plasma has a power density of 0.07 W/cm 3 to 70 W/cm 3 .
15. The method of claim 1 , further comprising exposing the substrate to a third plasma different from at least one of the first plasma and the second plasma.
16. The method of claim 1 , further comprising repeating contacting the substrate with the silicon precursor and contacting the substrate with the first plasma two or more times prior to contacting the substrate with the second plasma.
17. The method of claim 16 , wherein contacting the substrate with the silicon precursor and contacting the substrate with the first plasma is repeated at least 25 times prior to contacting the substrate with the second plasma.
18. The method of claim 16 , wherein a total duration during which the substrate is contacted with the first plasma is greater than or equal to a total duration during which the substrate is contacted with the second plasma.
19. The method of claim 1 , wherein no additional reactants are used for forming the SiN thin film.
20. The method of claim 1 , wherein at least one of the first and third plasmas is generated from a gas comprising both hydrogen gas and nitrogen gas.
21. The method of claim 1 , wherein the SiN thin film has a total impurity level excluding hydrogen of below 5 at-%.
22. The method of claim 1 , wherein the SiN thin film has a hydrogen level below about 10 at-%.
23. The method of claim 1 , wherein the SiN thin film has a step coverage and pattern loading effect of greater than 90% on a three-dimensional structure.