Method and apparatus for UV exposure of low dielectric constant materials for porogen removal and improved mechanical properties

• US 7,265,061 B1
• Filed: 03/11/2004
• Issued: 09/04/2007
• Est. Priority Date: 05/09/2003
• Status: Expired due to Fees

• Current Assignee: Novellus Systems Incorporated (Lam Research Corporation)
• Original Assignee: Novellus Systems Incorporated (Lam Research Corporation)
• Inventors: Srinivasan, Easwar, Cho, Seon-Mee, Mordo, David, Lu, Brian G.
• Primary Examiner(s): Picardat; Kevin M.
• Application Number:
  US10/800,377
• Time in Patent Office: 1,272 Days
• Field of Search: 438/758, 438/764, 438/778, 438/780, 438/781, 438/783, 438/784, 438/787, 438/790, 438/791, 438/794, 438/788, 438/792
• US Class Current: 438/764
• CPC Class Codes: C23C 16/401 containing silicon
• CPC Class Codes: C23C 16/56 After-treatment
• CPC Class Codes: H01L 21/3105 After-treatment

Abstract

Methods and apparatus for preparing a porous low-k dielectric material on a substrate are provided. The methods optionally involve the use of ultraviolet radiation to react with and remove porogen from a porogen containing precursor film leaving a porous dielectric matrix and further exposing the dielectric matrix to ultraviolet radiation to increase the mechanical strength of the dielectric matrix. Some methods involve activating a gas to create reactive gas species that can clean a reaction chamber. One disclosed apparatus includes an array of multiple ultraviolet sources that can be controlled such that different wavelengths of light can be used to irradiate a sample at a time.

Claims

1. A method of preparing a porous low-k dielectric layer on a substrate, the method comprising:

(a) forming a precursor film on the substrate, the precursor film comprising a porogen and a structure former;

(b) removing the porogen from the precursor film to thereby create voids within the dielectric material and form the porous low-k dielectric layer; and

(c) exposing the dielectric material to ultraviolet radiation in a manner that increases the mechanical strength of the porous low-k dielectric layer;

wherein the ultraviolet radiation in (c) has an intensity of between about 2230 W/cm² and 3118 W/cm² and (c) occurs for a time period time period between about 1 and 200 seconds.

2. The method of claim 1, wherein the substrate is a semiconductor wafer.

3. The method of claim 2, wherein the porous low-k dielectric layer is formed on the semiconductor wafer using a single-wafer or batch process.

4. The method of claim 1, wherein the precursor film comprises a porogen and a silicon-containing structure former.

5. The method of claim 1, wherein the precursor film is formed by co-depositing the porogen with the structure former.

6. The method of claim 1, wherein the structure former is produced from at least one of a silane, an alkylsilane, an alkoxysilane, siloxane, carbon-doped variation thereof, or combination thereof.

7. The method of claim 1, wherein the structure former is produced from diethoxymethylsilane (DEMS), octamethylcyclotetrasiloxane (OMCTS), tetramethylcyclotetrasiloxane (TMCTS), dimethyldimethoxysilane (DMDMOS), carbon-doped oxides or a combination thereof.

8. The method of claim 1, wherein the porogen comprises a polyfunctional cyclic non-aromatic compound.

9. The method of claim 8, wherein the polyfunctional cyclic non-aromatic compound is an alpha-terpiene (ATRP) compound.

10. The method of claim 9, wherein the porogen comprises a mesoporous structure formed from a block copolymer.

11. The method of claim 1, wherein the precursor film is formed by a chemical vapor deposition process, plasma-enhanced CVD (PECVD) or a spin-on technique.

12. The method of claim 1, wherein (b) involves exposing the porogen within the precursor film to ultraviolet radiation.

13. The method of claim 12, wherein the ultraviolet radiation comprises a wavelength at or near an absorption peak of the porogen.

14. The method of claim 12, wherein the ultraviolet radiation comprises a wavelength distribution ranging from about 156 nm to about 800 nm.

15. The method of claim 12, wherein exposure to ultraviolet radiation occurs for a time period ranging between about 1 second and about 60 minutes.

16. The method of claim 12, wherein the substrate temperature during ultraviolet radiation exposure ranges between about minus 10 and about 600 degrees Celsius, preferably below 400 degrees Celsius.

17. The method of claim 1, wherein at least part of (b) and (e) occur simultaneously.

18. The method of claim 1, wherein (c) is performed under an ambient comprising at least one of argon, nitrogen, helium, hydrogen, oxygen, carbon dioxide, and a combination thereof.

19. The method of claim 1, wherein (c) is performed under vacuum.

20. The method of claim 1, wherein (c) involves using ultraviolet radiation comprising a wavelength distribution ranging from about 156 to about 800 nm.

21. The method of claim 1, wherein (c) involves using a substrate temperature ranging between about minus 10 and about 450 degrees Celsius.

22. The method of claim 1, wherein (c) is performed at pressures ranging between about 1 μ

Torr and about 760 Torr (atmospheric pressure).

23. The method of claim 1, wherein after (c), the porous low-k dielectric layer has a hardness value ranging between about 0.5 GPa and about 3 GPa.

24. The method of claim 1, wherein (a), (b) and (c) are repeated to form a film with desired properties.

25. The method of claim 1, further comprising providing a reactive gas that cleans porogen residue from an apparatus in which the porogen is removed from the precursor film.

26. The method of claim 25, wherein providing a reactive gas that cleans porogen residue from an apparatus comprises introducing a gas into the apparatus and exposing the gas to ultraviolet radiation having a wavelength that activates the gas.

27. The method of claim 26, wherein the gas is oxygen.

28. A method of preparing a porous low-k dielectric layer on a substrate, the method comprising:

(a) providing in a reaction chamber a substrate having a precursor film comprising a porogen and a structure former;

(b) exposing the porogen from the precursor film to ultraviolet radiation of a first wavelength distribution to thereby create voids within the dielectric material and form the porous low-k dielectric layer;

(c) exposing the dielectric material to ultraviolet radiation of a second wavelength distribution to increase the mechanical strength of the porous low-k dielectric layer; and

(d) activating a gas by exposure to ultraviolet radiation of a third wavelength distribution to produce a species that cleans porogen residue from surfaces within the reaction chamber.

29. The method of claim 28, wherein the ultraviolet radiation of a first wavelength distribution includes radiation at a wavelength at or near an absorption peak of the porogen.

30. The hod of claim 28, wherein the ultraviolet radiation of a second wavelength distribution includes radiation with a wavelengths ranging from about 156 to about 800 nm.

31. The method of claim 28, wherein first, second and third wavelength distributions are produced by first, second, and third ultraviolet sources, respectively.

32. The method of claim 28, wherein the gas in (d) oxygen.

33. The method of claim 28, wherein activating the oxygen in (d) produces at least one of ozone and active oxygen radicals.

34. The method of claim 28, wherein the ultraviolet radiation of a third wavelength distribution includes radiation with a wavelengths ranging from about 150 to about 250 mm.

35. The method of claim 28, wherein the ultraviolet radiation of a third wavelength distribution includes radiation with an intensity ranging between about 1 μ

W/cm² and about 3000 mW/cm².

36. The method of claim 28, wherein (d) occurs for a time period ranging between about 1 second and about 60 minutes.

37. The method of claim 28, wherein the gas in (d) comprises at least one of a fluorine-containing gas or an oxygen-containing gas.

38. The method of claim 28, further comprising evacuating the reaction chamber to remove volatilized porogen residue during (d).