Method of removing photoresist and reducing native oxide in dual damascene copper process

• US 6,352,938 B2
• Filed: 12/09/1999
• Issued: 03/05/2002
• Est. Priority Date: 12/09/1999
• Status: Expired due to Term

• Current Assignee: United Microelectronics Corporation
• Original Assignee: United Microelectronics Corporation
• Inventors: Chuang, Hsi-Ta, Yang, Chan-Lon, Chen, Tong-Yu
• Primary Examiner(s): Smith, Matthew
• Assistant Examiner(s): Lytle, Craig P.
• Application Number:
  US09/457,561
• Publication Number:
  US 20010014529A1
• Time in Patent Office: 817 Days
• Field of Search: 438/689, 438/710, 438/725, 438/726, 438/730, 438/637, 438/687, 438/711, 438/618, 438/622, 427/534, 134/1.1
• US Class Current: 438/725
• CPC Class Codes: H01L 21/02063 the processing being the formation of vias or contact holes
• CPC Class Codes: H01L 21/31138 by dry-etching
• CPC Class Codes: H01L 21/76814 post-treatment or after-treatment, e.g. cleaning or removal of oxides on underlying conductors
• CPC Class Codes: H01L 21/76838 characterised by the formation and the after-treatment of the conductors etching for patterning the conductors H01L21/3213
• CPC Class Codes: H01L 21/76843 formed in openings in a dielectric
• CPC Class Codes: H01L 21/76865 Selective removal of parts of the layer H01L21/76844 takes precedence
• CPC Class Codes: H01L 21/76873 for electroplating
• CPC Class Codes: H01L 21/76879 by selective deposition of conductive material in the vias, e.g. selective C.V.D. on semiconductor material, plating plating on semiconductors in general H01L21/288

Abstract

A method of manufacturing metallic interconnects. A substrate has a copper line formed therein. An inter-metal dielectric layer is formed over the substrate and the copper line. A patterned photoresist layer is formed over the inter-metal dielectric layer. The inter-metal dielectric layer is etched to form a trench and a contact opening that exposes a portion of the copper line, wherein the contact opening is under the trench. At a low temperature and using a plasma derived from a gaseous mixture N₂H₂ (H₂:4%)/O₂, the photoresist layer is removed. Any copper oxide layer formed on the copper line in the process of removing photoresist material is reduced back to copper using gaseous N₂H₂ (H₂:4%). A barrier layer conformal to the trench and the contact opening profile is formed. Copper is deposited to form a conformal first copper layer over the trench and the contact opening. Using the first copper layer as a seeding layer, a copper or a copperless electroplating is carried out so that a second copper layer is grown anisotropically over the first copper layer.

Claims

1. A method of manufacturing metallic interconnects, comprising the steps of:

providing a substrate having a copper line therein;

forming a dielectric layer over the substrate and the copper line;

forming a patterned photoresist layer over the dielectric layer;

forming a dual damascene opening that exposes a portion of the copper line, wherein the dual damascene opening includes a contact opening and a trench with the contact opening located under the trench;

removing the photoresist layer using a low-temperature plasma of a gaseous mixture containing N₂H₂(H₂;

4%) and O₂ so that an amount of oxidation on a surface of the copper line is minimized;

reducing the copper oxide on the surface of copper line by introducing gaseous N₂H₂ (H₂;

4%) in a non-oxygen ambience;

forming a conformal barrier layer over the interior surface of the trench and the contact opening;

forming a first copper layer over the barrier layer inside the trench and the contact opening; and

growing a second copper layer over the first copper layer inside the trench and the contact opening, wherein the second copper layer includes a trench line and a contact, with the contact located under the trench line.

2. The method of claim 1, wherein flow rates of components of the gaseous mixture containing N₂H₂(H₂:

4%) and O₂ while removing photoresist material are 100 to 300 sccm for N₂H₂ (H₂;

4%) and 200 to 600 sccm for O₂.

3. The method of claim 1, wherein the step of removing the photoresist layer is carried out at a temperature of about 30 to 90°

C., a pressure of about 200 to 600 mT, a working power of about 800 to 1300 Watts (2.54 GHz) and a radio frequency (RF) rating of about 100 to 400 Watts (13.56 MHz).

4. The method of claim 1, wherein the step of reducing the copper oxide back to copper is carried out with gaseous N₂H₂ is introduced at a rate of about 100 to 300 sccm, a temperature to about 30 to 90°

C., a pressure of about 200 to 600 mT, a working power of about 800 to 1300 Watts (2.54 GHz) and a radio frequency (RF) rating of about 100 to 400 Watts (13.56 MHz).

5. The method of claim 1, wherein the step of forming the second copper layer includes copper electroplating using the first copper layer as a seed layer.

6. The method of claim 1, wherein the step of forming the second copper layer includes a copperless electroplating using the first copper layer as a seed layer.

7. The method of claim 1, wherein after the step of reducing the copper oxide back to copper using gaseous N₂H₂ (H₂:

4%) but before forming the barrier layer, further includes cleaning with a solvent.

8. A dual damascene process, comprising the steps of:

providing a substrate having a metal line therein;

forming an inter-metal dielectric layer over the metal line and the substrate;

forming a patterned photoresist layer over the inter-metal dielectric layer;

forming a dual damascene opening that exposes a portion of the metal line in the inter-metal dielectric layer, wherein the dual damascene opening includes a contact opening and a trench with the contact opening located under the trench;

removing the photoresist layer using a low-temperature plasma of a gaseous mixture containing N₂H₂(H₂;

4%) and O₂ so that an amount of oxidation on a surface of the copper line is minimized;

reducing the copper oxide on the surface of copper line by introducing gaseous N₂H₂ (H₂;

4%) in a non-oxygen ambience;

forming a conformal barrier layer over an interior surface of the trench and the contact opening;

forming a conformal seeding layer over the barrier layer inside the trench and the contact opening; and

growing a metallic layer over the seeding layer inside the trench and the contact opening, wherein the metallic layer includes a trench line and a contact, with the contact located under the trench line.

9. The process of claim 8, wherein flow rates of the components of the gaseous mixture containing N₂H₂(H₂:

4%) and O₂ while removing photoresist material are 100 to 300 sccm for N₂H₂ (H₂;

4%) and 200 to 600 sccm for O₂.

10. The process of claim 8, wherein the step of removing the photoresist layer is carried out at a temperature of about 30 to 90°

C., a pressure of about 200 to 600 mT, a working power of about 800 to 1300 Watts (2.54 GHz) and a radio frequency (RF) rating of about 100 to 400 Watts (13.56 MHz).

11. The process of claim 8, wherein the step of reducing the copper oxide back to copper is carried our with gaseous N₂H₂ is introduced at a rate of about 100 to 300 sccm, a temperature to about 30 to 90°

C., a pressure of about 200 to 600 mT, a working power of about 800 to 1300 Watts (2.54 GHz) and a radio frequency (RF) rating of about 100 to 400 Watts (13.56 MHz).

12. The process of claim 8, wherein the seeding layer includes a copper layer.

13. The process of claim 8, wherein the metallic layer includes a copper layer.

14. The process of claim 8, wherein the step of forming the metallic layer includes copper electroplating using the seeding layer as a base.

15. The process of claim 8, wherein the step of forming the metallic layer includes copperless electroplating using the seeding layer as a base.

16. The process of claim 8, wherein the metal line includes a copper line.

17. A method of removing copper oxide formed over the copper line during removing a photoresist layer, comprising the steps of:

providing a substrate having a copper line therein;

forming a dielectric layer over the copper line and the substrate;

forming a patterned photoresist layer over the dielectric layer;

forming a dual damascene opening that exposes a portion of the copper line in the dielectric layer, wherein the dual damascene opening includes a contact opening and a trench, with the contact opening located under the trench;

removing the photoresist layer using a low-temperature plasma of a gaseous mixture containing N₂H₂(H₂;

4%) and O₂ so that an amount of copper oxide grown on a surface of the copper line is minimized; and

after removing the photoresist layer, reducing the copper oxide on the surface of copper line by introducing gaseous N₂H₂ (H₂;

4%) in a non-oxygen ambiance.

18. The method of claim 17, wherein flow rates of components of the gaseous mixture containing N₂H₂(H₂:

4%) and O₂ while removing photoresist material are 100 to 300 sccm for N₂H₂ (H₂;

4%) and 200 to 600 sccm for O₂.

19. The method of claim 17, wherein the step of removing the photoresist layer is carried out at a temperature of about 30 to 90°

C., a pressure of about 200 to 600 mT, a working power of about 800 to 1300 Watts (2.54 GHz) and a radio frequency (RF) rating of about 100 to 400 Watts (13.56 MHz).

20. The method of claim 17, wherein the step of reducing the copper oxide on the copper line includes using gaseous N₂H₂ (H₂:

4%).

21. The method of claim 20, wherein the step of reducing copper oxide back to copper is carried out with gaseous N₂H₂ introduced at a rate of about 100 to 300 sccm, a temperature of about 30 to 90°

C., a pressure of about 200 to 600 mT, a working power of about 800 to 1300 Watts (2.54 GHz) and a radio frequency (RF) rating of about 100 to 400 Watts (13.56 MHz).

22. A copper damascene process, comprising the steps of:

providing a substrate having a copper line therein;

forming an inter-metal dielectric layer over the copper line and the substrate;

forming a patterned photoresist layer over the inter-metal dielectric layer;

forming a copper damascene opening in the inter-metal dielectric layer, wherein the copper damascene opening includes a contact opening and a trench, with the contact opening located under the trench;

removing the photoresist layer using a low-temperature plasma of a gaseous mixture containing N₂H₂(H₂;

4%) and O₂ so that an amount of oxidation on a surface of the copper line is minimized;

reducing the copper oxide on the surface of copper line by passing gaseous N₂H₂ (H₂;

4%) in a non-oxygen ambience;

forming a conformal barrier layer over the interior surface of the trench and the contact opening;

forming a conformal seeding layer over the barrier layer inside the trench and the contact opening; and

growing a copper layer over the seeding layer inside the trench and the contact opening, wherein the copper layer includes a trench line and a contact with the contact is located under the trench line.

23. The method of claim 22, wherein flow rates of components of the gaseous mixture containing N₂H₂(H₂:

4%) and O₂ while removing photoresist material are 100 to 300 sccm for N₂H₂ (H₂;

4%) and 200 to 600 sccm for O₂.

24. The method of claim 22, wherein the step of removing the photoresist layer is carried out at a temperature of about 30 to 90°

C., a pressure of about 200 to 600 mT, a working power of about 800 to 1300 Watts (2.54 GHz) and a radio frequency (RF) rating of about 100 to 400 Watts (13.56 MHz).

25. The method of claim 22, wherein the step of reducing copper oxide back to copper is carried out with gaseous N₂H₂ introduced at a rate of about 100 to 300 sccm, a temperature of about 30 to 90°

C., a pressure of about 200 to 600 mT, a working power of about 800 to 1300 Watts (2.54 GHz) and a radio frequency (RF) rating of about 100 to 400 Watts (13.56 MHz).

26. The method of claim 22, wherein the seeding layer includes a copper layer.

27. The method of claim 22, wherein the step of forming the copper layer includes copper electroplating using the seeding layer as a base.

28. The method of claim 22, wherein the step of forming the copper layer includes a copperless electroplating using the seeding layer as a base.

29. A method for preventing a copper line from being oxidized during a removal of a photoresist layer from a substrate having the copper line formed thereon, wherein the copper line is exposed by an opening formed in a material layer on the substrate, the method comprising the steps of:

performing a plasma treatment to removed the photoresist layer and suppressing the formation of copper oxide on a surface of the copper line, wherein the plasma treatment is produced by using a gaseous mixture containing N₂H₂(H₂;

4%) and O₂ as a source; and

after removing the photoresist layer, reducing the copper oxide on the surface of copper line by introducing gaseous N₂H₂ (H₂;

4%) in a non-oxygen ambiance.

30. The method of claim 29, wherein the step of reducing the copper oxide on the copper line includes using gaseous N₂H₂ (H₂:

4%).