Methods and apparatus for engineering an interface between a diffusion barrier layer and a seed layer

• US 7,855,147 B1
• Filed: 05/24/2007
• Issued: 12/21/2010
• Est. Priority Date: 06/22/2006
• Status: Active Grant

• Current Assignee: Novellus Systems Incorporated (LAM Research Corporation)
• Original Assignee: Novellus Systems Incorporated (LAM Research Corporation)
• Inventors: Greer, Frank, Rairkar, Asit, Pradhan, Anshu A., Rozbicki, Robert, Dulkin, Alexander
• Primary Examiner(s): Graybill; David E
• Application Number:
  US11/807,178
• Time in Patent Office: 1,307 Days
• Field of Search: None
• US Class Current: 438/676
• CPC Class Codes: C23C 14/022 by means of bombardment with energetic particles or radiation
• CPC Class Codes: C23C 14/046 Coating cavities or hollow spaces, e.g. interior of tubes; Infiltration of porous substrates
• CPC Class Codes: H01L 21/02068 during, before or after processing of conductive layers, e.g. polysilicon or amorphous silicon layers
• CPC Class Codes: H01L 21/2855 by physical means, e.g. sputtering, evaporation H01L21/28518 - H01L21/28537 and H01L21/28568 take precedence
• CPC Class Codes: H01L 21/28562 Selective deposition
• CPC Class Codes: H01L 21/32131 by physical means only
• CPC Class Codes: H01L 21/76805 the opening being a via or contact hole penetrating the underlying conductor
• CPC Class Codes: H01L 21/76813 involving a partial via etch
• CPC Class Codes: H01L 21/76844 Bottomless liners
• CPC Class Codes: H01L 21/76846 Layer combinations
• CPC Class Codes: H01L 21/76862 Bombardment with particles, e.g. treatment in noble gas plasmas; UV irradiation
• CPC Class Codes: H01L 21/76865 Selective removal of parts of the layer H01L21/76844 takes precedence
• CPC Class Codes: H01L 21/76868 Forming or treating discontinuous thin films, e.g. repair, enhancement or reinforcement of discontinuous thin films
• CPC Class Codes: H01L 21/76873 for electroplating
• CPC Class Codes: H01L 23/53238 Additional layers associated with copper layers, e.g. adhesion, barrier, cladding layers
• CPC Class Codes: H01L 2924/00 Indexing scheme for arrangements or methods for connecting or disconnecting semiconductor or solid-state bodies as covered by H01L24/00
• CPC Class Codes: H01L 2924/0002 Not covered by any one of groups H01L24/00, H01L24/00 and H01L2224/00

Abstract

Copper seed layers are formed on diffusion barrier layers (e.g., on Ta, and TaN_x layers) without significant agglomeration of copper, with the use of an engineered barrier layer/seed layer interface. The engineered interface includes an adhesion layer, in which copper atoms are physically trapped and are prevented from migrating and agglomerating. The adhesion layer can include between about 20-80% atomic of copper. The copper atoms of the adhesion layer are exposed during deposition of a copper seed layer and serve as the nucleation sites for the deposited copper. Thin, continuous, and conformal seed layers can be deposited on top of the adhesion layer. The trapping of copper within the adhesion layer is achieved by intermixing diffusion barrier and seed layer materials using PVD and/or ALD.

Claims

1. A method of depositing a copper seed layer on a semiconductor substrate having a plurality of recessed features, the method comprising:

(a) providing a semiconductor substrate having a barrier layer residing at least on the bottom portions and on the sidewalls of the recessed features;

(b) forming an adhesion layer over at least a portion of the barrier layer, wherein the adhesion layer comprises exposed copper atoms, and wherein forming the adhesion layer comprises

(i) depositing a layer of copper at least over the barrier material residing in the bottom portions of the recessed features;

(ii) resputtering the deposited copper from the bottom portions of the recessed features onto the sidewalls of the recessed features, thereby depositing copper atoms onto the layer of barrier material on the sidewalls; and

(iii) resputtering the barrier material residing at the bottom portions of the recessed features onto the sidewalls of the recessed features, thereby intermixing the copper atoms with the barrier material on the sidewalls of the recessed features; and

(c) depositing the copper seed layer on at least a portion of the adhesion layer, wherein the adhesion layer has a different composition from the seed layer and the barrier layer.

2. The method of claim 1, wherein the copper seed layer comprises a material selected from the group consisting of Cu, CuAl, CuZn, CuMg, CuSn, CuMn, CuAg, and CuB.

3. The method of claim 1, wherein the barrier layer comprises tantalum and/or tantalum nitride.

4. The method of claim 1, wherein (b) comprises applying a flux of a tantalum-containing material and a flux of a copper-containing material onto a substrate surface.

5. The method of claim 4, wherein at least one of the fluxes comprises a resputter-generated flux.

6. The method of claim 4, wherein the substrate surface comprises a recessed feature sidewall.

7. The method of claim 4, wherein the flux of the tantalum-containing material and the flux of the copper-containing material have substantially opposite directions.

8. The method of claim 4, wherein the flux of the tantalum-containing material and the flux of the copper-containing material are applied simultaneously.

9. The method of claim 4, wherein the flux of the tantalum-containing material and the flux of the copper-containing material are applied sequentially.

10. The method of claim 1, wherein the adhesion layer comprises copper atoms intermixed with the barrier layer material substantially over an entire sidewall surface of a recessed feature.

11. The method of claim 1, wherein the adhesion layer comprises copper in a concentration of between about 20% and 80% atomic.

12. The method of claim 1, wherein methods for depositing the barrier layer, forming the adhesion layer, and depositing the copper seed layer are independently selected from the group consisting of physical vapor deposition (PVD), atomic layer deposition (ALD), chemical vapor deposition (CVD) and pulsed deposition layer (PDL).

13. The method of claim 1, wherein (i) or (ii) is performed in a PVD chamber, in a plasma pre-clean chamber, in an iALD chamber, or in a plasma ALD chamber.

14. The method of claim 1, wherein (b) and (c) are performed in a copper seed layer PVD chamber.

15. The method of claim 1, wherein (i) comprises depositing a discontinuous layer of copper on the sidewalls of the recessed features.

16. The method of claim 1, wherein (i), (ii), and (iii) are repeated at least once.

17. The method of claim 1, wherein operations (i), (ii), and (iii) are performed in a copper seed PVD chamber.

18. The method of claim 1, further comprising depositing copper from a sputter target during at least one of operations (i), (ii) and (iii) on at least the sidewalls of the recessed features.

19. The method of claim 1, wherein the copper layer has a maximum thickness of less than about 50 Å

at the bottom portions of the recessed features being resputtered, wherein the thickness refers to the thickness of the layer deposited during operation (i).

20. The method of claim 1, wherein resputtering the diffusion barrier layer does not entirely remove the diffusion barrier material from the bottom of the recessed feature.

21. The method of claim 1, wherein

(i) and (ii) comprise depositing copper from the sputter target while simultaneously sputter etching the deposited copper, such that an etch rate to deposition rate ratio (E/D) at the bottom portions of the recessed features is greater than about 1.

22. A method, of depositing a copper seed layer on a semiconductor substrate having a plurality of recessed features, the method comprising:

(a) providing a semiconductor substrate having a barrier layer residing at least on the bottom portions of the recessed features;

(b) forming an adhesion layer over at least a portion of the barrier layer, wherein the adhesion layer comprises exposed copper atoms, wherein (b) comprises;

(i) resputtering the barrier material from the bottom portions of the recessed features to expose an underlying copper surface;

(ii) resputtering the exposed copper from the bottom portions of the recesses onto the sidewalls of the recesses, thereby depositing copper atoms onto a layer of barrier material on the sidewalls; and

(iii) depositing a layer of barrier material from a sputter target on at least the exposed copper surface, without covering all of the exposed copper atoms of the adhesion layer residing on the sidewalls and

(c) depositing the copper seed layer on at least a portion of the adhesion layer, wherein the adhesion layer comprises copper intermixed with the barrier layer material; and

wherein the adhesion layer has a different composition from the seed layer and the barrier layer.

23. The method of claim 22, wherein (b) further comprises:

(iv) resputtering the barrier material deposited in (iii) from the bottom portions of the recessed features to expose an underlying copper surface;

(v) resputtering the exposed copper from the bottom portions of the recesses onto the sidewalls of the recesses, thereby depositing copper atoms onto a layer of intermixed material on the sidewalls to achieve intermixing between copper atoms and barrier material atoms on the sidewalls of the recessed features.

24. The method of claim 23, further comprising repeating operations (iii), (iv), and (v) at least once to improve intermixing between copper atoms and barrier material atoms on the sidewalls of the recessed features.

25. The method of claim 24, wherein operation (iii) is performed 2-6 times.

26. The method of claim 23 further comprising:

(vi) depositing a layer of barrier material on at least the bottom portions of the recessed features after (iv).

27. The method of claim 22, wherein the layer of deposited barrier material has a thickness of less than about 50 Å

at the bottom of the recessed feature that is being resputtered.

28. The method of claim 22, wherein each resputtering operation (ii) removes less than about 200 Å

of copper layer thickness from the bottom portion of the recessed feature.

29. A method, of depositing a copper seed layer on a semiconductor substrate having a plurality of recessed features, the method comprising:

(a) providing a semiconductor substrate having a barrier layer deposited thereon;

(b) forming an adhesion layer over at least a portion of the barrier layer, wherein the adhesion layer comprises exposed copper atoms, wherein forming the adhesion layer further comprises forming an anchor recess in an underlying metal line; and

(c) depositing the copper seed layer on at least a portion of the adhesion layer, wherein the adhesion layer comprises copper intermixed with the barrier layer material; and

wherein the adhesion layer has a different composition from the seed layer and the barrier layer.

30. The method of claim 29, wherein the depth of the anchor recess is between about 50 Å

and 500 Å

.

31. A method, of depositing a copper seed layer on a semiconductor substrate having a plurality of recessed features, the method comprising:

(a) providing a semiconductor substrate with a barrier material residing at least on the bottom portions of the recessed features;

(b) forming an adhesion layer over at least a portion of the barrier layer, wherein the adhesion layer comprises exposed copper atoms, and wherein (b) comprises;

(i) resputtering the barrier material from the bottom portions of the recessed features to expose an underlying copper surface; and

(ii) resputtering the exposed copper from the bottom portions of the recesses onto the sidewalls of the recesses, thereby depositing copper atoms onto a layer of barrier material residing on the sidewalls of the recessed features, wherein

during at least operation (ii) a second portion of barrier material is being simultaneously deposited and sputter etched at the bottom of the recess with an E/D ratio of greater than about 1, such that sputter etching comprises resputtering the barrier material onto the sidewalls of the recessed features, thereby intermixing the barrier material with copper atoms in the adhesion layer; and

(c) depositing the copper seed layer on at least a portion of the adhesion layer, wherein the adhesion layer has a different composition from the seed layer and the barrier layer.

32. A method, of depositing a copper seed layer on a semiconductor substrate having a plurality of recessed features, the method comprising:

(a) providing a semiconductor substrate having a barrier layer deposited thereon;

(b) forming an adhesion layer over at least a portion of the barrier layer, wherein the adhesion layer comprises exposed copper atoms, wherein forming the adhesion layer comprises forming a nanolaminate comprising barrier material sub-layers and copper sub-layers, wherein at least one sub-layer is deposited by ALD and

(c) depositing the copper seed layer on at least a portion of the adhesion layer, wherein the adhesion layer has a different composition from the seed layer and the barrier layer.

33. The method of claim 32, wherein forming the nanolaminate comprises depositing at least one of the sublayers by a method selected from the group consisting of PVD, ALD, CVD, and PDL.

34. The method of claim 32, wherein the thickness of the nanolaminate is less than about 20 Å

.

35. The method of claim 32, wherein the nanolaminate comprises at least one copper sub-layer deposited by ALD.

36. The method of claim 32, wherein the nanolaminate comprises at least one sub-layer of barrier material deposited by PVD.

37. The method of claim 32, wherein forming the nanolaminate comprises

depositing alternating copper-rich and barrier material-rich sub-layers, wherein a barrier-rich sub-layer is deposited onto the exposed barrier layer of the provided substrate;

and a copper-rich sub-layers is deposited as the top layer of the nanolaminate.

38. A method, of depositing a copper seed layer on a semiconductor substrate having a plurality of recessed features, the method comprising:

(a) depositing a barrier material by ALD at least on the bottom and sidewall portions of the recessed features;

(b) forming an adhesion layer over at least a portion of the barrier layer, wherein the adhesion layer comprises exposed copper atoms, and wherein (b) comprises resputtering the barrier material from the bottom portions of the recesses onto the sidewalls of the recesses, while simultaneously depositing copper in a copper PVD chamber, thereby intermixing copper atoms and barrier material on the sidewalls of the recessed features; and

(c) depositing the copper seed layer on at least a portion of the adhesion layer, wherein the adhesion layer has a different composition from the seed layer and the barrier layer.

39. The method of claim 38, wherein during the resputtering the barrier material from the bottom portions of the recesses onto the sidewalls of the recesses, while simultaneously depositing copper in a copper PVD chamber a net copper deposition rate is increased in a course of the resputtering process.

40. The method of claim 38, wherein a ratio of DC power at a PVD target to RF power at a substrate pedestal (DC/RF) is increased during a course of the resputtering process in (b).

41. A method of depositing a copper seed layer on a semiconductor substrate having a plurality of recessed features, the method comprising:

(a) providing a semiconductor substrate having a barrier material layer residing at least on the bottom portions and on the sidewalls of the recessed features;

(b) forming an adhesion layer over at least a portion of the barrier layer, wherein the adhesion layer comprises exposed copper atoms, and wherein forming the adhesion layer comprises;

(i) depositing copper from the sputter target while simultaneously sputter etching the deposited copper, such that an etch rate to deposition rate ratio (E/D) at the bottom portions of the recessed features is greater than about 1, and wherein the etched copper atoms are resputtered onto the sidewalls of the recessed features, thereby being deposited onto the layer of barrier material on the sidewalls;

(ii) resputtering the barrier material residing at the bottom portions of the recesses onto the sidewalls of the recessed features, thereby intermixing the copper atoms with the barrier material on the sidewalls of the recessed features; and

(c) depositing the copper seed layer on at least a portion of the adhesion layer, wherein the adhesion layer has a different composition from the seed layer and the barrier layer.