Photoresist scum free process for via first dual damascene process

• US 6,861,376 B1
• Filed: 10/10/2002
• Issued: 03/01/2005
• Est. Priority Date: 10/10/2002
• Status: Expired due to Fees

• Current Assignee: Taiwan Semiconductor Manufacturing Company Limited
• Original Assignee: Taiwan Semiconductor Manufacturing Company Limited
• Inventors: Wu, Juei-Kuo, Shiu, Ruei-Je, Chen, Dian-Hau
• Primary Examiner(s): NGUYEN, HA T
• Application Number:
  US10/268,587
• Time in Patent Office: 873 Days
• Field of Search: 438637-640, 438/725, 438/687, 438/780, 438/781, 438/795
• US Class Current: 438/781
• CPC Class Codes: G03F 7/0035 Multiple processes, e.g. applying a further resist layer on an already in a previously step, processed pattern or textured surface
• CPC Class Codes: H01L 21/0274 Photolithographic processes
• CPC Class Codes: H01L 21/0277 Electrolithographic processes
• CPC Class Codes: H01L 21/76808 involving intermediate temporary filling with material

Abstract

An improved method of forming a dual damascene structure by a via first process is described. Via holes are formed in a damascene stack consisting of an etch stop layer, a dielectric layer, and a barrier layer. An i-line photoresist is coated on the substrate and fills the vias. An e-beam curing step is performed to render the photoresist components inactive towards adjacent layers. The photoresist is etched back to a level about 1600 Angstroms above the via bottom to form a plug. A second curing step may be performed and then a Deep UV resist is preferably coated and patterned to form a trench opening above the vias. There is no interaction between the Deep UV photoresist and the cured plug which thereby prevents scum or bridging defects from occurring. Fences during trench etch are avoided. Plug stabilization also prevents voids from forming during trench patterning.

Claims

1. A dual damascene method comprising:

(a) providing a substrate having one or more conductive regions and a stack of layers on said substrate;

(b) forming at least one via hole in said stack, said via hole is aligned above a conductive region;

(c) depositing a photoresist layer within said via hole;

(d) curing said photoresist layer with an electron beam;

(e) etching said photoresist layer to a level below the top of said via hole;

(f) forming a trench above said via hole;

(g) removing said photoresist layer from said via hole; and

(h) filling the trench and via hole simultaneously with metal.

2. The method of claim 1 wherein said conductive regions are comprised of copper, aluminum, or a Cu/Al alloy.

3. The method of claim 1 wherein said stack of layers is comprised of an upper etch stop layer, a middle dielectric layer, and a bottom barrier layer.

4. The method of claim 3 wherein said dielectric layer has a thickness between about 4000 and 9000 Angstroms.

5. The method of claim 3 wherein said etch stop layer is comprised of a carbide, nitride, oxide or oxynitride and has a thickness in the range of about 200 to 600 Angstroms.

6. The method of claim 1 wherein said dielectric layer is selected from a group of materials including SiLK, FLARE, SiO₂, polyimides, fluorosilicate glass, porous SiO₂ and organic doped SiO₂.

7. The method of claim 1 wherein the exposure dose for the e-beam curing step is from about 1000 to 20000 microCoulombs/cm² with an accelerating voltage of about 1 to 10 keV.

8. The method of claim 7 further comprised of heating the substrate between about 100°

C. and 150°

C. during the e-beam exposure.

9. The method of claim 1 further comprising a step of e-beam curing the photoresist layer in said via hole after said etching step and prior to forming said trench.

10. The method of claim 1 wherein said photoresist layer is etched to a level that is 1600±

500 Angstroms above the bottom of said via hole.

11. The method of claim 1 wherein said photoresist layer is comprised of an i-line photoresist.

12. The method of claim 1 wherein said photoresist layer is a positive tone composition.

13. The method of claim 1 wherein said photoresist layer is a negative tone composition.

14. The method of claim 1 wherein the trench pattern has a width between about 0.1 microns and 0.5 microns.

15. The method of claim 1 wherein the trench etch is stopped at a point wherein the bottom of the trench is from about 2000 to 5000 Angstroms above the bottom of said via hole.

16. A dual damascene method comprising:

(a) providing a substrate having one or more conductive regions and a stack of layers on said substrate;

(b) forming at least one via hole in said stack, said via hole is aligned above a conductive region;

(c) depositing a photoresist layer within said via hole;

(d) performing a UV curing step while heating said substrate;

(e) etching said photoresist layer to a level below the top of said via hole;

(f) forming a trench above said via hole;

(g) removing said photoresist layer from said via hole; and

(h) filling the trench and via hole simultaneously with metal.

17. The method of claim 16 wherein said conductive region is comprised of copper, aluminum, or a Cu/Al alloy.

18. The method of claim 16 wherein said stack of layers is comprised of an upper etch stop layer, a middle dielectric layer, and a bottom barrier layer.

19. The method of claim 18 wherein said dielectric layer has a thickness from between about 4000 and 9000 Angstroms.

20. The method of claim 18 wherein said etch stop layer is comprised of a carbide, nitride, oxide or oxynitride and has a thickness in the range of about 200 to 600 Angstroms.

21. The method of claim 16 wherein said dielectric layer is selected from a group of materials including SiLK, FLARE, SiO₂, polyimides, fluorosilicate glass, porous SiO₂ and organic doped SiO₂.

22. The method of claim 16 wherein the exposure for the UV curing step is comprised of one or more wavelengths from a range of about 200 nm to 600 nm.

23. The method of claim 22 wherein the substrate is heated between about 150°

C. and 250°

C. during the UV curing step.

24. The method of claim 16 further comprising a step of UV curing the photoresist in said via hole after said etching step and prior to forming said trench.

25. The method of claim 16 wherein said photoresist layer is etched to a level that is 1600±

500 Angstroms above the bottom of said via hole.

26. The method of claim 16 wherein said photoresist layer is comprised of an i-line photoresist.

27. The method of claim 16 wherein said photoresist layer is a negative tone composition.

28. The method of claim 16 wherein said photoresist layer is a positive tone composition.

29. The method of claim 16 wherein the trench pattern has a width in the range of about 0.1 microns to 0.5 microns.

30. The method of claim 16 wherein the trench etch is stopped at a point wherein the bottom of the trench is from about 2000 to 5000 Angstroms above the bottom of said via hole.