Process for removing organic materials during formation of a metal interconnect

• US 7,122,484 B2
• Filed: 04/28/2004
• Issued: 10/17/2006
• Est. Priority Date: 04/28/2004
• Status: Expired due to Fees

• Current Assignee: Taiwan Semiconductor Manufacturing Company Limited
• Original Assignee: Taiwan Semiconductor Manufacturing Company Limited
• Inventors: Chan, Bor-Wen, Huang, Jun-Lung, Shih, Hsin-Ching, Hsu, Peng-Fu, Tao, Hun-Jan, Huang, Yi-Chen, Perng, Baw-Ching, Hsu, Lawrance
• Primary Examiner(s): Lebentritt, Michael
• Assistant Examiner(s): Ahmadi, Mohsen
• Application Number:
  US10/833,558
• Publication Number:
  US 20050245082A1
• Time in Patent Office: 902 Days
• Field of Search: 438/689, 438/754, 438/745, 438/134, 438/687, 438/765, 438789-790, 438/778
• US Class Current: 438/765
• CPC Class Codes: C11D 2111/22 Electronic devices, e.g. PCBs or semiconductors
• CPC Class Codes: C11D 3/3947 Liquid compositions
• CPC Class Codes: C11D 7/50 Solvents
• CPC Class Codes: G03F 7/423 containing mineral acids or salts thereof, containing mineral oxidizing substances, e.g. peroxy compounds
• CPC Class Codes: H01L 21/02063 the processing being the formation of vias or contact holes
• CPC Class Codes: H01L 21/02101 only involving supercritical fluids
• CPC Class Codes: H01L 21/31133 by chemical means
• CPC Class Codes: H01L 21/31144 using masks
• CPC Class Codes: H01L 21/76808 involving intermediate temporary filling with material
• CPC Class Codes: H01L 21/76814 post-treatment or after-treatment, e.g. cleaning or removal of oxides on underlying conductors

Abstract

A method for removing organic material from an opening in a low k dielectric layer and above a metal layer on a substrate is disclosed. An ozone water solution comprised of one or more additives such as hydroxylamine or an ammonium salt is applied as a spray or by immersion. A chelating agent may be added to protect the metal layer from oxidation. A diketone may be added to the ozone water solution or applied in a gas or liquid phase in a subsequent step to remove any metal oxide that forms during the ozone treatment. A supercritical fluid mixture that includes CO₂ and ozone can be used to remove organic residues that are not easily stripped by one of the aforementioned liquid solutions. The removal method prevents changes in the dielectric constant and refractive index of the low k dielectric layer and cleanly removes residues which improve device performance.

Claims

1. A fully wet method of removing an organic layer or organic residue from a substrate, comprising:

(a) providing a substrate with a low k dielectric layer having an organic layer or organic residue formed thereon; and

(b) contacting the low k dielectric layer on said substrate with a liquid solution that includes ozone and water, said ozone and said water together constituting at least 95% by volume of the total volume of said liquid solution;

wherein the liquid solution further includes one or more additives that are each selected from a group consisting of NH₄OH, hydroxylamine, NH₄F, NH₄Cl, NH₄Br, and NH₄I; and

wherein the liquid solution further includes one or more additives that are each selected from a group consisting at H₂SO₄, HCl, and HF.

2. The method of claim 1 wherein the amount of the additives in the liquid solution is less than about 5% by volume of the total volume of the liquid solution.

3. The method of claim 1 further including:

rinsing said substrate with DI water after said contacting;

drying said substrate; and

then contacting said substrate a second time with a liquid solution that includes ozone, water, and one or more additives which are each one of H₂SO₄, HCl, and HF.

4. The method of claim 1 wherein the temperature of said liquid solution is between about 5°

C. to 100°

C.

5. The method of claim 1 wherein said contacting the low k dielectric layer involves applying the liquid solution by a spray method or by immersion.

6. The method of claim 1 wherein said liquid solution further includes one or more chelating agents.

7. The method of claim 6 wherein each said chelating agent is one of ethylenediaminediacetic acid (EDDA) and ethylenediaminetetracetic acid (EDTA).

8. The method of claim 6 wherein the total amount of the one or more chelating agents added to the solution is less than about 1% by weight of the total liquid solution.

9. The method of claim 1 wherein said organic layer is one of a patterned photoresist layer, a plug layer, and an anti-reflective coating and said organic residue is form a previous process step.

10. A method of removing an organic layer during the formation of a copper interconnect on a substrate comprising:

(a) providing a substrate with a first copper layer having an exposed top surface and a stack comprised of an upper first photoresist layer, a middle low k dielectric layer and a lower etch stop layer formed on said substrate, said stack has a via formed therein that is aligned over said first copper layer;

(b) contacting said first photoresist layer with a liquid solution comprised of ozone, water, and one or more additives to remove the first photoresist layer from said substrate;

(c) forming a plug layer comprised of a hardened organic layer in said via and coating and patterning a second photoreist layer to form a trench above said via, said trench is transferred into said low k dielectric layer by a plasma etch process; and

(d) contacting said plug layer and said second photoresist layer with a liquid solution comprised of ozone, water and one or more additives to remove said plug layer and second photoresist from the substrate.

11. The method of claim 10 further comprised of depositing a diffusion barrier layer within said via and trench, depositing a second copper layer on said diffusion barrier layer to fill said via and trench;

and planarizing said second copper layer to be coplanar with said low k dielectric layer.

12. The method of claim 10 wherein said one or more additives are selected from a first group which is NH₄OH, hydroxylamine, NH₄F, NH₄Cl, NH₄Br, and NH₄I.

13. The method of claim 10 wherein said one or more additives are selected from a second group which is H₂SO₄, HC1, and HF.

14. The method of claim 10 wherein the amount of additives in the liquid solution in steps (b) and (d) is less than about 5% by volume of the liquid solution.

15. The method of claim 10 wherein the temperature of said liquid solution is from about 5°

C. to 100°

C.

16. The method of claim 10 wherein said contracting comprises applying the liquid solution by a spray method or by an immersion process.

17. The method of claim 10 wherein said liquid solution is further comprised of one or more chelating agents.

18. The method of claim 17 wherein said chelating agent is EDDA or EDTA.

19. The method of claim 17 wherein the amount of one or more chelating agents added to the solution is less than about 1% by weight of the total liquid solution.

30. The method of claim 10, wherein in the liquid solution of step (b), said ozone and said water together constitute at least 95% by volume of the total volume of the liquid solution.

31. The method of claim 10, wherein in the liquid solution of step (d), said ozone and said water together constitute at least 95% by volume of the total volume of the liquid solution.

20. A method of removing organic residue from a low k dielectric layer on a substrate during the fabrication of a metal interconnect comprising:

(a) providing a substrate with a stack that includes a lower etch stop layer and an upper low k dielectric layer formed thereon, said stack having an opening formed therein in which organic residue remains from one or more previous process steps and where said opening exposes a portion of a conductive layer in said substrate; and

(b) contacting the organic residue on said substrate with a liquid solution that includes ozone and water, said ozone and said water together constituting at least 95% by volume of the total volume of said liquid solution.

21. The method of claim 20 wherein said opening is a via, a trench, or a trench formed above a via.

22. The method of claim 20 wherein said liquid solution has a temperature in the range of about 5°

C. No 100°

C.

23. The method of claim 20 wherein said contacting with a liquid solution is performed in a single wafer tool or in a batch process tool.

24. The method of claim 20 wherein said liquid solution further includes a chelating agent.

25. The method of claim 20 wherein the liquid solution further includes a diketone to prevent oxidation of said conductive layer.

26. The method of claim 20 further including:

rinsing said substrate with DI water after step (b);

drying said substrate; and

then contacting the conductive layer with a diketone reagent.

27. The method of claim 26 wherein the chamber temperature is between about 20°

C. and 120°

C. and said diketone is applied for a period of less than about 180 seconds.

28. The method of claim 26 wherein said diketone is in a liquid phase and is applied at the rate of about 0.001 to 10 ml per minute.

29. The method of claim 26 wherein said diketone is in a gas phase and is applied with a flaw rate of from 1 to 10 sccm.