Method for electroless plating a contact pad

• US 20010018266A1
• Filed: 05/09/2001
• Published: 08/30/2001
• Est. Priority Date: 02/24/1999
• Status: Active Grant

• Current Assignee: Li Li, Tongbi Jiang
• Original Assignee: Li Li, Tongbi Jiang
• Inventors: Jiang, Tongbi, Li, Li
• Granted Patent: US 6,630,400 B2
• Time in Patent Office: Days
• US Class Current: 438/678
• CPC Class Codes: H01L 21/02052 Wet cleaning only H01L21/02085 takes precedence
• CPC Class Codes: H01L 21/288 from a liquid, e.g. electrolytic deposition
• CPC Class Codes: H01L 21/76826 by contacting the layer with gases, liquids or plasmas
• CPC Class Codes: H01L 21/76828 thermal treatment
• CPC Class Codes: H01L 21/76834 formation of thin insulating films on the sidewalls or on top of conductors H01L21/76831 takes precedence
• 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 21/7685 the layer covering a conductive structure H01L21/76849 takes precedence
• CPC Class Codes: H01L 2224/0401 Bonding areas specifically adapted for bump connectors, e.g. under bump metallisation [UBM]
• CPC Class Codes: H01L 2224/131 with a principal constituent of the material being a metal or a metalloid, e.g. boron [B], silicon [Si], germanium [Ge], arsenic [As], antimony [Sb], tellurium [Te] and polonium [Po], and alloys thereof
• CPC Class Codes: H01L 24/03 Manufacturing methods
• CPC Class Codes: H01L 24/05 of an individual bonding area
• CPC Class Codes: H01L 2924/01005 Boron [B]
• CPC Class Codes: H01L 2924/01006 Carbon [C]
• CPC Class Codes: H01L 2924/01011 Sodium [Na]
• CPC Class Codes: H01L 2924/01013 Aluminum [Al]
• CPC Class Codes: H01L 2924/01014 Silicon [Si]
• CPC Class Codes: H01L 2924/01016 Sulfur [S]
• CPC Class Codes: H01L 2924/01029 Copper [Cu]
• CPC Class Codes: H01L 2924/01033 Arsenic [As]
• CPC Class Codes: H01L 2924/01075 Rhenium [Re]
• CPC Class Codes: H01L 2924/01078 : Platinum [Pt]
• CPC Class Codes: H01L 2924/01079 : Gold [Au]
• CPC Class Codes: H01L 2924/01322 : Eutectic Alloys, i.e. obtained by a liquid transforming into two solid phases
• CPC Class Codes: H01L 2924/014 : Solder alloys
• CPC Class Codes: H01L 2924/05042 : Si3N4
• CPC Class Codes: H01L 2924/14 : Integrated circuits
• CPC Class Codes: H01L 2924/19041 : being a capacitor
• CPC Class Codes: H01L 2924/19043 : being a resistor
• CPC Class Codes: Y10S 134/902 : Semiconductor wafer

Abstract

A method and apparatus is disclosed for sequential processing of integrated circuits, particularly for conductively passivating a contact pad with a material which resists formation of resistive oxides. In particular, a tank is divided into three compartments, each holding a different solution: a lower compartment and two upper compartments divided by a barrier, which extends across and partway down the tank. The solutions have different densities and therefore separate into different layers. In the illustrated embodiment, integrated circuits with patterned contact pads are passed through one of the upper compartments, in which oxide is removed from the contact pads. Continuing downward into the lower compartment and laterally beneath the barrier, a protective layer is selectively formed on the insulating layer surrounding the contact pads. As the integrated circuits are moved upwardly into the second upper compartment, a conducting monomer selectively forms on the contact pads prior to any exposure to air. The integrated circuits can then be transferred to an ozone chamber where polymerization results in a conductive passivation layer on the contact pad.

Claims

1. A method for plating a conductive layer in an integrated circuit formed on a substrate, comprising:

immersing the substrate in a cleaning fluid; and

transferring the substrate from the cleaning fluid to a separate plating fluid while keeping the substrate immersed in fluid.

2. The method of

claim 1

, wherein the cleaning fluid comprises a reducing agent.

3. The method of

claim 2

, wherein the reducing agent etches oxide from the conductive layer.

4. The method of

claim 3

, wherein the conductive layer comprises aluminum, and the reducing agent comprises a dilute base.

5. The method of

claim 3

, wherein the reducing agent comprises dilute aqueous phase NaOH.

6. The method of

claim 3

, wherein transferring the substrate comprises passing the substrate from the cleaning fluid directly to a second fluid.

7. The method of

claim 6

, wherein transferring the substrate further comprises passing the substrate from the second fluid directly to the plating fluid.

8. The method of

claim 6

, wherein the second fluid selectively forms a protective layer on an insulating material surrounding the conductive layer, and the plating fluid selectively forms a conducting material on the conductive layer.

9. The method of

claim 8

, wherein the second fluid is a solution including a siliconizing agent

10. The method of

claim 8

, wherein the protective layer has a hydrophobic exposed surface, and the plating fluid comprises a hydrophilic conducting material.

11. The method of

claim 8

, wherein the conducting material comprises a passivation precursor.

12. The method of

claim 11

, further comprising polymerizing the passivation precursor.

13. The method of

claim 12

, wherein the plating fluid comprises pyrrole, and polymerizing the passivation precursor comprises exposing the precursor to an oxidizing agent.

14. The method of

claim 1

, wherein the conductive layer comprises a patterned contact pad exposed through a window in a surrounding insulating layer.

15. The method of

claim 14

, wherein the contact pad comprises a bond pad for connecting the integrated circuit to outside circuits.

16. A process for plating a contact pad in an integrated circuit formed on a substrate, comprising:

cleaning an oxide from the contact pad in a wet etch bath; and

transferring the substrate from the wet etch bath to a second liquid phase treatment, the second liquid phase treatment selectively depositing a layer of conducting material over the cleaned contact pad, wherein the second liquid phase treatment comprises a first liquid subphase directly contacting and separate from the wet etch bath and a second liquid subphase directly contacting and separate from the first liquid subphase.

17. The process of

claim 16

, wherein the first liquid subphase selectively forms a protective layer over an insulating material surrounding the contact pad.

18. The process of

claim 17

, wherein the conducting material comprises a conducting monomer in the second liquid subphase, the process further comprising polymerizing the layer of conducting material over the cleaned contact pad.

19. The process of

claim 18

, wherein the conducting monomer comprises pyrrole.

20. The process of

claim 16

, wherein the first liquid subphase comprises a siliconizing agent and the insulating material comprises silicon nitride.

21. The process of

claim 16

, wherein the first liquid subphase is more dense than and immiscible with the etch bath, and the second liquid subphase is less dense than and immiscible with the first liquid subphase.

22. The process of

claim 21

, wherein the etch bath is adjacent to the second liquid subphase and separated from the second liquid subphase by a water-tight barrier, the first liquid subphase extending beneath and contacting each of the etch bath and the second liquid subphase.

23. A method of forming a conductive passivation layer for a contact pad in an integrated circuit formed on a substrate, the contact pad comprising a conductive layer exposed through a window in a surrounding insulating layer, the method comprising:

providing a container having first, second and third liquid phases separated from one another, the first phase contacting the second phase and the second phase contacting the third phase;

immersing the substrate in the first phase wherein the conductive layer is cleaned;

transferring the substrate from the first phase directly to the second phase, wherein a protective layer is selectively formed on the insulating layer;

transferring the substrate from the second phase directly to the third phase, wherein a monomer layer is selectively formed on the cleaned conductive layer; and

polymerizing the monomer layer.

24. The method of

claim 23

, wherein the first phase comprises an oxide etch bath.

25. The method of

claim 24

, wherein the protective layer comprises a hydrophobic exposed surface.

26. The method of

claim 25

, wherein the third phase comprises pyrrole.

27. The method of

claim 26

, wherein polymerizing comprises transferring the substrate from the third phase to an ozone chamber.

28. The method of

claim 23

, wherein the first and second phases have different densities and are immiscible.

29. The method of

claim 23

, wherein the second and third phases have different densities and are immiscible.

30. A method for electroless plating a conductive polymer on a metal surface of a workpiece, comprising:

immersing the workpiece in a container holding a plurality of solutions, wherein each of said plurality of solutions is in contact with at least one other of said plurality of solutions, thereby allowing direct transfer of said workpiece between said plurality of solutions in said container;

exposing the metal surface to an oxide cleaning solution within the container;

preferentially forming a layer comprising a conducting monomer after exposing the metal surface to an oxide cleaning solution and prior to removing the workpiece from the container; and

polymerizing said conducting monomer layer.

31. The method of

claim 30

, wherein said metal surface includes an aluminum oxide layer prior to immersing the workpiece.

32. The method of

claim 31

, further comprising selectively forming a hydrophobic upper surface over a non-metal material surrounding the metal surface prior to preferentially form the layer comprising a conducting monomer.

33. A method of forming a conductive passivation layer for a contact pad in a circuit formed on a substrate, the contact pad comprising a conductive layer exposed through a window in a surrounding insulating layer, the method comprising:

providing a container having first, second and third liquid phases separated from one another;

immersing the substrate in the first phase wherein the conductive layer is cleaned;

transferring the substrate from the first phase directly to the second phase without exposing the substrate to any intermediate phase, wherein a protective layer is selectively formed on the insulating layer;

transferring the substrate from the second phase directly to the third phase without exposing the substrate to any intermediate phase, wherein a monomer layer is selectively formed on the cleaned conductive layer; and

polymerizing the monomer layer, wherein the first phase comprises an oxide etch bath and the protective layer comprises a hydrophobic exposed surface.

34. The method of

claim 33

, wherein the third phase comprises pyrrole.

35. The method of

claim 34

, wherein polymerizing comprises transferring the substrate from the third phase to an ozone chamber.