Water vapor passivation of a wall facing a plasma

• US 20070190266A1
• Filed: 02/10/2006
• Published: 08/16/2007
• Est. Priority Date: 02/10/2006
• Status: Active Grant

• Current Assignee: Applied Materials Incorporated
• Original Assignee: Applied Materials Incorporated
• Inventors: Fu, Xinyu
• Granted Patent: US 7,695,567 B2
• Time in Patent Office: Days
• US Class Current: 427/569
• CPC Class Codes: H01L 21/02063 the processing being the formation of vias or contact holes
• CPC Class Codes: H01L 21/76814 post-treatment or after-treatment, e.g. cleaning or removal of oxides on underlying conductors

Abstract

A chamber passivation method particularly useful for hydrogen plasma cleaning of low-k dielectrics prior to coating a barrier layer into a via hole with hydrogen radicals are provided from a remote plasma source. For each wafer, the chamber is passivated with water vapor (or other gas even more chemabsorbed on plasma facing walls) passed through the remote plasma source prior to the ignition of the hydrogen plasma. The water vapor is absorbed on walls, such as alumina and quartz parts of the remote plasma source, and forms a protective mono-layer that endures sufficiently long to protect the walls during the generation of the hydrogen plasma. Thereby, the plasma facing walls, particularly of a dielectric such as alumina, are protected from etching.

Claims

1. A passivation method for processing a substrate in a plasma processing chamber, comprising the steps of:

injecting a passivating gas in a non-excited state into the processing chamber, wherein the passivating gas is at least as greatly chemabsorbed on walls of the processing chamber as is water vapor; and

then processing the substrate in the processing chamber in a plasma of a processing gas.

2. The passivation method of claim 1, wherein the passivating gas is water vapor.

3. The passivation method of claim 1, wherein the passivating gas is chosen from the group consisting of CH₄, CO, and CO₂.

4. The passivation method of claim 2, wherein the plasma is a reducing plasma.

5. The passivation method of claim 2, wherein the processing gas contains hydrogen.

6. The passivation method of claim 2, wherein the processing gas is chosen from the group consisting of (1) hydrogen and (2) hydrogen and helium.

7. The passivation method of claim 6, wherein the processing chamber includes a remote plasma source having an output tube connected to an interior of the processing chamber and the water vapor and processing gas are injected into the remote plasma source, wherein the remote plasma source is not substantially activated during the injecting step but is activated during the processing step to excite the processing gas into the plasma.

8. The passivation method of claim 6, wherein said processing chamber further includes an ion filter disposed between the remote plasma source and the chamber through which the passivating gas and the processing gas flow.

9. The passivation method of claim 2, wherein the processing chamber includes a remote plasma sourcing having an output connected to the interior of the processing chamber, wherein the water vapor and processing gas are injected into the remote plasma source, and wherein the remote is not substantially activated during the injecting step but is activated during the processing step to excite the processing gas into the plasma.

10. The passivation method of claim 2, wherein the processing step cleans a dielectric layer.

11. The passivation method of claim 10, wherein the processing step removes residues from the dielectric layer.

12. The passivation method of claim 10, wherein the dielectric layer is porous and has a dielectric constant less than 3.9.

13. The passivation method of claim 2, further comprising pumping the processing chamber after the end of the injecting step and before the plasma is excited to remove water vapor from the chamber.

14. A plasma processing method, comprising the steps performed for each of a plurality of serially processed substrate of:

inserting a substrate into a plasma processing chamber including a pedestal for supporting the substrate, a gas showerhead opposed to the pedestal, and a remote plasma source having a supply tube connecting its output to a manifold in back of the showerhead;

passing water vapor through the remote plasma source without exciting the water vapor into an effective plasma;

then passing a reducing processing gas though the remote plasma source and exciting it into a plasma; and

then extinguishing the plasma and removing the substrate from the plasma processing chamber.

15. The method of claim 14, wherein the reducing processing gas comprises hydrogen and substantially no water vapor nor oxygen.

16. The method of claim 14, wherein the substrate includes a dielectric layer having a hole etched therethrough.

17. The method of claim 16, wherein the dielectric layer has a dielectric constant less than 3.9.

18. A passivation and processing method, comprising the steps of:

injecting unexcited water vapor into a vacuum processing chamber containing a substrate to be processed;

then pumping the vacuum processing chamber to remove a substantial amount of the water vapor therefrom; and

thereafter exciting a processing gas into a plasma for processing the substrate within the vacuum processing chamber.

19. The method of claim 18, wherein the substrate contains a dielectric layer having a dielectric constant less than 3.9 and the processing gas comprises hydrogen and substantially no water and no oxygen and hydrogen ions are filtered from the plasma upstream from the substrate.

20. The method of claim 18, wherein the water vapor and processing gas are flowed into a remote plasma source delivering its output to the plasma processing chamber, wherein the remote plasma source is not substantially activated during the injecting step and is activated during the exciting step.

21. A method of operating a hydrogen plasma source, comprising repeating a sequence of the steps of:

a first step of passing water vapor through a plasma generator while the generator is not activated; and

a second step of passing hydrogen gas through the plasma generator while the generator is activated.

22. The method of claim 21, wherein a duration of the first step is substantially less than a duration of the second step.