Electroless copper fill process

• US 7,456,102 B1
• Filed: 10/11/2005
• Issued: 11/25/2008
• Est. Priority Date: 10/11/2005
• Status: Expired due to Fees

• Current Assignee: Novellus Systems Incorporated (Lam Research Corporation)
• Original Assignee: Novellus Systems Incorporated (Lam Research Corporation)
• Inventors: Varadarajan, Seshasayee, Zhou, Jian
• Primary Examiner(s): Nhu; David
• Application Number:
  US11/248,860
• Time in Patent Office: 1,141 Days
• Field of Search: 438/687, 438/680, 438/681, 438/678, 438/688, 438/905, 438/700, 438/706, 438/745, 438/475
• US Class Current: 438/687
• CPC Class Codes: C23C 18/1608 from pretreatment step, i.e. selective pre-treatment
• CPC Class Codes: C23C 18/1651 Two or more layers only obtained by electroless plating
• CPC Class Codes: C23C 18/1653 Two or more layers with at least one layer obtained by electroless plating and one layer obtained by electroplating
• CPC Class Codes: C23C 18/1669 Agitation, e.g. air introduction
• CPC Class Codes: C23C 18/31 Coating with metals
• CPC Class Codes: C23C 18/40 using reducing agents
• CPC Class Codes: H01L 21/288 from a liquid, e.g. electrolytic deposition
• 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 21/76874 for electroless plating
• 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
• CPC Class Codes: H05K 2201/09563 Metal filled via
• CPC Class Codes: H05K 2203/1476 Same or similar kind of process performed in phases, e.g. coarse patterning followed by fine patterning
• CPC Class Codes: H05K 3/422 characterised by electroless plating method; pretreatment therefor

Abstract

Disclosed is a procedure for bottom-up fill of electroless copper film in sub-micron integrated circuit features. By repeatedly placing an integrated circuit wafer in an electroless bath, a transient period of time of accelerated growth in the feature is repeated to achieve many small layers of deposition, each of which is thicker near the base of the feature. The net result is filing of the feature from the bottom-up fill without formation of voids. The electroless bath employed to form the continuous electroless copper film may include a reducing agent, a complexing agent, a source of copper ions, a pH adjuster, and optionally one or more surfactants and/or stabilizers.

Claims

1. A method of filling features on a substrate surface, the method comprising

(a) providing a substrate having recessed features formed on a surface thereof;

(b) contacting at least the recessed features of the substrate surface with an electroless plating bath and allowing electroless deposition of a conductive material to proceed for a first period of time;

(c) removing the substrate from the electroless plating bath; and

(d) repeating the contacting and removing of (b) and (c) to at least partially fill the recessed features with the conductive material.

2. The method of claim 1, wherein the recessed features comprise Damascene trenches and vias on a partially fabricated integrated circuit.

3. The method of claim 1, wherein the substrate surface comprises an exposed diffusion barrier layer.

4. The method of claim 1, wherein the substrate surface comprises a conductive seed layer that provides discontinuous coverage within at least some of the recessed features.

5. The method of claim 1, wherein the electroless plating bath comprises a reducing agent, a surfactant, and a source of copper ions.

6. The method of claim 5, wherein the surfactant is a polyethylene glycol having a molecular weight of between about 200 to 1,000,000.

7. The method of claim 6, wherein the polyethylene glycol is present in the electroless plating bath at a concentration of between about 2 and 100 ppm.

8. The method of claim 5, wherein the reducing agent comprises an aldehyde moiety.

9. The method of claim 5, wherein the electroless plating bath further comprises a complexing agent for copper ions.

10. The method of claim 1, wherein the first period of time, during which the recessed features are contacted with the plating bath in (b) has a duration of between about one-half minute and 2 minutes.

11. The method of claim 1, wherein the electroless plating bath has a pH of between about 11 and 13.

12. The method of claim 11, wherein the pH adjuster is tetramethylammonium hydroxide.

13. The method of claim 1, wherein the electroless plating bath has a temperature of between about 50 and 70 degrees C. while contacting the recessed features of the substrate surface.

14. The method of claim 1, further comprising rising the substrate surface after removing the substrate from the electroless plating bath.

15. The method of claim 1, further comprising rotating the substrate in the electroless plating bath during at least a portion of the contacting.

16. The method of claim 1, wherein at least some of the recesses in said substrate surface have an aspect ratio of at least about 4:

1.

17. The process of claim 1, further comprising:

drying the substrate; and

electroplating the substrate.

18. A method of filling Damascene features in a partially fabricated integrated circuit, the method comprising:

(a) immersing the partially fabricated integrated circuit, or at least a portion thereof containing the Damascene features, in an electroless copper plating bath comprising a polymer suppressing molecule;

(b) removing the partially fabricated integrated circuit, or at least a portion thereof, from the bath after a period of time;

(c) re-immersing the partially fabricated integrated circuit, or at least a portion thereof containing the Damascene features, in the electroless copper plating bath comprising the polymer suppressing molecule; and

(d) again removing the partially fabricated integrated circuit, or at least a portion thereof, from the bath after a period of time.

19. The method of claim 18, wherein the polymer suppressing molecule is PEG.

20. The method of claim 19, wherein the polymer suppressing molecule is PEG of molecular weight of between about 200 to 1,000,000.

21. The method of claim 18, wherein the electroless plating process is allowed to continue until the electroless plated copper layer attains a thickness of between about 500-10000 Angstroms.

22. The process of claim 18, further comprising, after at least one of (b) and (d), rising the partially fabricated integrated circuit with water.

23. The process of claim 18, further comprising:

drying the partially fabricated integrated circuit; and

electroplating the partially fabricated integrated circuit.