Chamber undercoat preparation method for low temperature ALD films
Methods and apparatus disclosed herein relate to the formation and use of undercoats on the interior surfaces of reaction chambers used to deposit films on substrates. The undercoats are deposited through atomic layer deposition methods. For example, the undercoat may be formed by flowing a first reactant into the reaction chamber, flowing a second reactant into the reaction chamber while the first reactant is adsorbed on interior surfaces of the reaction chamber, and exposing the reaction chamber to plasma to form the undercoat. The disclosed undercoats help prevent metal contamination, provide improved resistance to flaking, and are relatively thin. Because of the superior resistance to flaking, the disclosed undercoats allow more substrates to be processed between subsequent cleaning operations, thereby increasing throughput.
1. A method of forming an undercoat on interior surfaces of a reaction chamber for processing substrates, comprising:
(a) introducing a flow of a first reactant in vapor phase into the reaction chamber and allowing the first reactant to adsorb onto the interior surfaces of the reaction chamber;
(b) introducing a flow of a second reactant in vapor phase into the reaction chamber while the first reactant is adsorbed on the interior surfaces of the reaction chamber;
(c) exposing the reaction chamber to plasma when the flow of at least one of the first and second reactants has ceased, in order to drive a reaction between the first and second reactants on the interior surfaces of the reaction chamber to form the undercoat, wherein the undercoat conformally coats the interior surfaces of the reaction chamber;
(d) receiving a substrate in the reaction chamber;
(e) introducing a flow of a third reactant in vapor phase into the reaction chamber and allowing the third reactant to adsorb onto the surface of the substrate;
(f) introducing a flow of a fourth reactant in vapor phase into the reaction chamber while the third reactant is adsorbed on the surface of the substrate; and
(g) exposing the reaction chamber to plasma when the flow of at least one of the third and fourth reactants has ceased, in order to drive a reaction between the third and fourth reactants to form a second film on the surface of the substrate,
wherein operations (a)-(c) occur when there is no substrate present in the reaction chamber,
wherein operations (a)-(c) are repeated until the undercoat is at least about 0.1 μm thick, and
wherein the first reactant and second reactant are the same as the third reactant and fourth reactant, respectively.
2. The method of claim 1 , wherein the temperature in the reaction chamber does not vary by more than about 2° C. during operations (a)-(c).
3. The method of claim 2 , wherein the undercoat is an oxide, nitride, a carbide, or a carbonitride.
4. The method of claim 3 , wherein the second reactant comprises O 2 and N 2 O.
5. The method of claim 2 , wherein the undercoat is a noble metal, a lanthanide oxide, a group 4 metal oxide, or a group 5 metal oxide.
6. The method of claim 1 , wherein the undercoat conformally coats a substrate carrier.
7. The method of claim 6 , wherein the undercoat is no more than about 0.2 μm thick.
8. The method of claim 1 , wherein the undercoat is no more than about 0.5 μm thick.
9. The method of claim 1 , wherein the second and fourth reactants each comprise O 2 and N 2 O.
10. The method of claim 1 , wherein reaction chamber pressure, reaction chamber temperature, dosing durations, plasma exposure durations, and RF power values remain substantially constant between operations (a)-(c) and operations (e)-(g).
11. The method of claim 1 , wherein the temperature in the reaction chamber does not vary by more than about 2° C. during operations (a)-(g).
12. The method of claim 11 , wherein operation (e) begins within about 5 minutes after a last iteration of operation (c).
13. The method of claim 1 , wherein the reaction chamber is not purged between a last iteration of operation (c) and a first iteration of operation (e).
14. The method of claim 1 , wherein operations (d)-(g) are repeated with a plurality of substrates, and wherein film deposited on the interior surfaces of the reaction chamber during operations (a)-(g) does not begin to flake or peel off until a total of at least about 7.5 μm of the second film has been deposited on the substrates.
15. The method of claim 1 , wherein operations (d)-(g) are repeated with a plurality of substrates, and wherein film deposited in operations (a)-(g) does not begin to flake or peel off until at least about 300 substrates have been processed through the reaction chamber using operations (d)-(g).
16. The method of claim 1 , wherein a first iteration of operations (a)-(c) are performed at a first level of RF flux and a second iteration of operations (a)-(c) are performed at a second level of RF flux, where the first and second levels of RF flux are different.