Remote plasma pre-clean with low hydrogen pressure

• US 20070117397A1
• Filed: 01/17/2006
• Published: 05/24/2007
• Est. Priority Date: 11/22/2005
• Status: Active Grant

• Current Assignee: Applied Materials Incorporated
• Original Assignee: Applied Materials Incorporated
• Inventors: Fu, Xinyu, Forster, John, Bhatnagar, Ajay, Yu, Jick, Gopalraja, Praburam
• Granted Patent: US 7,704,887 B2
• Time in Patent Office: Days
• US Class Current: 438/710
• CPC Class Codes: G03F 7/427 using plasma means only
• CPC Class Codes: H01J 37/32357 Generation remote from the workpiece, e.g. down-stream
• CPC Class Codes: H01J 37/32422 Arrangement for selecting ions or species in the plasma
• CPC Class Codes: H01J 37/3266 Magnetic control means
• CPC Class Codes: H01L 21/02063 the processing being the formation of vias or contact holes
• CPC Class Codes: H01L 21/02068 during, before or after processing of conductive layers, e.g. polysilicon or amorphous silicon layers
• CPC Class Codes: H01L 21/67028 for cleaning followed by drying, rinsing, stripping, blasting or the like
• CPC Class Codes: H01L 21/67069 for drying etching
• CPC Class Codes: H01L 21/76814 post-treatment or after-treatment, e.g. cleaning or removal of oxides on underlying conductors

Abstract

A plasma cleaning method particularly useful for removing photoresist and oxide residue from a porous low-k dielectric with a high carbon content prior to sputter deposition. A remote plasma source produces a plasma primarily of hydrogen radicals. The hydrogen pressure may be kept relatively low, for example, at 30 milliTorr. Optionally, helium may be added to the processing gas with the hydrogen partial pressure held below 150 milliTorr. Superior results are obtained with 70% helium in 400 milliTorr of hydrogen and helium. Preferably, an ion filter, such as a magnetic filter, removes hydrogen and other ions from the output of the remote plasma source and a supply tube from the remote plasma source includes a removable dielectric liner in combination with dielectric showerhead and manifold liner.

Claims

1. A method of plasma processing a substrate containing a dielectric layer, comprising the steps of:

disposing the substrate in a vacuum chamber to which is attached a remote plasma source;

passing a reducing processing gas through the remote plasma source and thence into the chamber, the gas mixture comprising hydrogen and substantially no oxygen or water, and

maintaining a pressure within the chamber such that a hydrogen partial pressure in the chamber is less than 150 milliTorr and greater than 10 milliTorr.

2. The method of claim 1, wherein the hydrogen partial pressure is no more than 120 milliTorr and greater than 20 milliTorr.

3. The method of claim 1, wherein the processing gas consists essentially of hydrogen.

4. The method of claim 1, wherein the processing gas consists essentially of hydrogen and helium.

5. The method of claim 1, further comprising filtering out ions delivered from the remote plasma source to the vacuum chamber.

6. The method of claim 1, wherein the dielectric layer comprises at least 20 at % carbon and has a porosity of at least 10%.

7. The method of claim 1, wherein the dielectric layer has a dielectric constant of no more than 2.5.

8. The method of claim 1, further comprising filtering ions from an output of the remote plasma source.

9. A method of plasma processing a substrate, comprising the steps of:

disposing the substrate in a vacuum chamber to which is attached a remote plasma source; and

passing a reducing processing gas through the remote plasma source and thence into the vacuum chamber, the processing gas comprising hydrogen and a noble gas and substantially no oxygen or water.

10. The method of claim 9, wherein the noble gas is helium.

11. The method of claim 10, wherein the process gas consists essentially of hydrogen and helium.

12. The method of claim 11, further comprising maintaining a total pressure in the vacuum chamber of between 200 and 600 milliTorr.

13. The method of claim 12, further comprising maintaining a partial pressure of hydrogen in the vacuum chamber of between 40 and 200 milliTorr.

14. The method of claim 12, wherein said total pressure is maintained at between 300 and 500 milliTorr.

15. The method of claim 14, wherein the partial pressure of hydrogen is maintained at between 80 and 150 milliTorr.

16. A plasma cleaning chamber, comprising:

a vacuum chamber including a pedestal for support a substrate to be cleaned;

a dielectric showerhead opposed to the pedestal;

a remote plasma source;

a delivery tube connecting an output of the remote plasma source to the showerhead and including a removable dielectric liner;

an ion filter disposed on the delivery tube; and

a source of hydrogen gas for the remote plasma source.

17. The chamber of claim 16, wherein the ion filter comprising a magnet assembly producing a magnetic field transverse to an axis of the delivery tube sufficient to deflect hydrogen ions toward a wall of the delivery tube.

18. The chamber of claim 16, further comprising a source of helium gas for the remote plasma source.

19. The chamber of claim 16, wherein the dielectric liner comprises alumina and the showerhead comprises quartz.

20. The chamber of claim 16, further comprising a second dielectric liner lining a manifold of the showerhead.