Method for improving mechanical properties of low dielectric constant materials

• US 7,622,400 B1
• Filed: 05/18/2004
• Issued: 11/24/2009
• Est. Priority Date: 05/18/2004
• Status: Active Grant

• Current Assignee: Novellus Systems Incorporated (LAM Research Corporation)
• Original Assignee: Novellus Systems Incorporated (LAM Research Corporation)
• Inventors: Srinivasan, Easwar, Wu, Qingguo, Fox, Keith, Mordo, David
• Primary Examiner(s): Smith; Matthew
• Assistant Examiner(s): Jefferson; Quovaunda
• Application Number:
  US10/849,568
• Time in Patent Office: 2,016 Days
• Field of Search: 438/774, 438/584, 438/783, 438/541, 438/FOR.448, 438/788, 438/761, 438/778, 438/784, 257/E21.226, 257E21275-E21277, 257/E21.149, 257/E21.3, 257/E21.576
• US Class Current: 438/784
• CPC Class Codes: H01L 21/02126 the material containing Si, O, and at least one of H, N, C, F, or other non-metal elements, e.g. SiOC, SiOC:H or SiONC
• CPC Class Codes: H01L 21/02216 the compound being a molecule comprising at least one silicon-oxygen bond and the compound having hydrogen or an organic group attached to the silicon or oxygen, e.g. a siloxane
• CPC Class Codes: H01L 21/02274 in the presence of a plasma [PECVD]
• CPC Class Codes: H01L 21/0234 treatment by exposure to a plasma
• CPC Class Codes: H01L 21/3105 After-treatment
• CPC Class Codes: H01L 21/31629 Deposition of halogen doped silicon oxide, e.g. fluorine doped silicon oxide
• CPC Class Codes: H01L 21/31633 Deposition of carbon doped silicon oxide, e.g. SiOC
• CPC Class Codes: H01L 21/76801 characterised by the formation and the after-treatment of the dielectrics, e.g. smoothing
• CPC Class Codes: H01L 21/76826 by contacting the layer with gases, liquids or plasmas

Abstract

Methods of forming a dielectric layer having a low dielectric constant and high mechanical strength are provided. The methods involve depositing a sub-layer of the dielectric material on a substrate, followed by treating the sub-layer with a plasma. The process of depositing and plasma treating the sub-layers is repeated until a desired thickness has been reached.

Claims

1. A method of forming a dielectric layer having a low dielectric constant and high mechanical strength, the method comprising:

(a) depositing a first sub-layer of the dielectric material on a substrate;

(b) treating the sub-layer with a plasma in a manner that improves the mechanical strength of the dielectric layer;

(c) depositing an additional sub-layer of the dielectric material on the previous sub-layer which was plasma treated; and

(d) plasma treating the additional sub-layer in a manner that improves the mechanical strength of the dielectric layer;

wherein each of (a) through (d) uses a plasma and is performed in a single reaction chamber and wherein the plasma used for operations (a)-(d) is ignited at the beginning of the process defined by operations (a)-(d) and maintained during the entire process.

2. The method of claim 1, further comprising repeating (c) and (d) one or more times until the dielectric layer attains a desired thickness.

3. The method of claim 1, wherein the as-deposited dielectric layer has a modulus of at least about 0.5-60 GPa.

4. The method of claim 1, wherein the as-deposited dielectric layer has a modulus of at least about 2-18 GPa.

5. The method of claim 1, wherein the plasma-treated dielectric layer has a modulus of at least about 3 GPa.

6. The method of claim 1, wherein the plasma-treated dielectric layer has a modulus of at least about 3 to 30 GPa.

7. The method of claim 1, wherein the as-deposited dielectric layer has a cracking threshold of at least about 1 micrometer.

8. The method of claim 1, wherein the plasma treated dielectric layer has a cracking threshold of at least about 1.5 micrometers.

9. The method of claim 1, wherein the as-deposited dielectric layer has a dielectric constant of at most about 4.

10. The method of claim 1, wherein the plasma treated dielectric layer has a dielectric constant of at most about 2.2-3.

11. The method of claim 1, wherein the dielectric layer has a hardness of at least about 2.5 GPa and a dielectric constant of at most about 3.

12. The method of claim 1, wherein the dielectric layer comprises a carbon doped silicon oxide.

13. The method of claim 1, wherein the dielectric layer comprises a fluorine doped silicon oxide.

14. The method of claim 1, wherein the thickness of the first sub-layer is between 10-10000 Angstrom.

15. The method of claim 1, wherein the thickness of the first sublayer is between 20 and 500 angstroms.

16. The method of claim 1, wherein each sub-layer thickness is between 10-10000 Angstroms.

17. The method of claim 1, wherein the thickness of each sublayer is between 20 and 500 angstroms.

18. The method of claim 1, wherein the wafer is held in one place during successive deposition and plasma treatment phases.

19. The method of claim 1, wherein transitioning between (a) and (b) comprises halting the flow of a dielectric precursor gas, but otherwise maintaining substantially the same plasma conditions and wherein the only difference between the gas flow in (a) and (b) is the presence or absence of the dielectric precursor gas.

20. The method of claim 1, wherein depositing each sublayer comprises a process selected from the group consisting of chemical vapor deposition (CVD), atomic layer deposition (ALD), high density plasma chemical vapor deposition (HDP CVD), and plasma assisted chemical vapor deposition (PECVD).

21. The method of claim 1, wherein at least one of (b) or (d) comprises using a plasma of one or more of the following gases:

H₂, He, Ar, O2, CO₂, N₂, and a fluorine containing gas.

22. The method of claim 1, wherein treating the sub-layer with a plasma is performed at a pressure of between about 0.1 and 20 Torr.

23. The method of claim 22, wherein treating the sub-layer with a plasma comprises generating the plasma at a frequency between about 200 kHz and 14 MHz.

24. The method of claim 22, wherein treating the sub-layer with a plasma comprises generating the plasma with more than 1 frequency wherein at least one of the frequencies is the range of about 200 kHz to 14 MHz.

25. The method of claim 1, wherein treating the sub-layer with a plasma comprises applying a plasma generating power of between about 1 and 5000 Watts.

26. The method of claim 1, wherein treating the sub-layer with a plasma comprises delivering one or more of H₂, He, Ar, O2, CO₂, N₂, and a fluorine containing gas at a flow rate of between about 10 and 40000 sccm each.

27. The method of claim 1, wherein transitioning between (b) and (c) comprises increasing a flow of a dielectric precursor gas while maintaining a plasma.

28. The method of claim 1 wherein at least one of the plasmas used in operations (a)-(d) is a fluorine-containing plasma.