Plasma atomic layer deposition
Plasma atomic layer deposition (ALD) is optimized through modulation of the gas residence time during an excited species phase, wherein activated reactant is supplied such as from a plasma. Reduced residence time increases the quality of the deposited layer, such as reducing wet etch rates, increasing index of refraction and/or reducing impurities in the layer. For example, dielectric layers, particularly silicon nitride films, formed from such optimized plasma ALD processes have low levels of impurities remaining from the silicon precursor.
1. A method of depositing a layer of dielectric silicon nitride by plasma atomic layer deposition, the method comprising:
providing a substrate in a reaction space;
in a first phase, contacting the substrate with a silicon precursor to adsorb an adsorbed species of the silicon precursor on the substrate; and
in a second phase, contacting the substrate with excited nitrogen species to react with the adsorbed species, wherein the residence time of the excited species in the reaction space during the second phase is less than about 1.0 s, and
wherein the first phase and second phase are repeated to form more than a monolayer of dielectric SiN.
2. The method of claim 1 , wherein the excited nitrogen species is supplied to or formed in the reaction space for greater than about 0.1 s.
3. The method of claim 1 , further comprising purging the reaction space between the first phase and the second phase.
4. The method of claim 1 , wherein in the second phase the excited nitrogen species remove ligands from the adsorbed species.
5. The method of claim 4 , wherein in the second phase the excited nitrogen species replace the ligands with nitrogen to leave a layer of dielectric SiN.
6. The method of claim 1 , wherein the silicon precursor is organic, and the layer of dielectric SiN contains less than 2 atomic % carbon.
7. The method of claim 1 , wherein the silicon precursor is a halide and the layer of dielectric SiN contains less than about 2 atomic % of a halogen from the silicon precursor.
8. The method of claim 1 , wherein the silicon precursor comprises a silicon amine.
9. The method of claim 8 , wherein the silicon precursor comprises BTBAS.
10. The method of claim 1 , wherein in the second phase the excited nitrogen species are supplied from a remote plasma unit.
11. The method of claim 1 , wherein the second phase comprises generating a plasma from nitrogen gas alone, and supplying the excited nitrogen species from the plasma.
12. The method of claim 1 , wherein the second phase comprises generating a plasma from nitrogen gas and hydrogen gas, and supplying the excited nitrogen species from the plasma.
13. The method of claim 1 , wherein the layer of dielectric silicon nitride has an index of refraction greater than about 1.9.
14. The method of claim 1 , wherein the layer of dielectric silicon nitride has an etch rate of less than about 1.5 nm/min in a buffered, 7:1 dilute HF solution.
15. A method of depositing a SiN layer on a substrate in a reaction space, the method comprising:
contacting the substrate with a silicon precursor; and
subsequently contacting the substrate with excited nitrogen species, wherein the residence time of the excited nitrogen species in the reaction space is less than about 1.0 s, and
repeating contacting the substrate with the silicon precursor and the excited nitrogen species to form more than a monolayer consisting essentially of dielectric SiN.
16. The method of claim 15 , wherein the excited nitrogen species is supplied to or formed in the reaction space for greater than about 0.1 s.
17. The method of claim 15 , wherein in the second phase the excited nitrogen species are supplied from a remote plasma unit.
18. The method of claim 15 , wherein the silicon precursor comprises a silicon amine.
19. The method of claim 15 , wherein the deposited SiN layer has an index of refraction greater than about 1.9.
20. The method of claim 15 , wherein the deposited SiN layer has an etch rate of less than about 1.5 nm/min in a buffered, 7:1 dilute HF solution.