Method to achieve continuous hydrogen saturation in sparingly used electroless nickel plating process

• US 6,616,967 B1
• Filed: 04/15/2002
• Issued: 09/09/2003
• Est. Priority Date: 04/15/2002
• Status: Active Grant

• Current Assignee: Texas Instruments, Inc.
• Original Assignee: Texas Instruments, Inc.
• Inventors: Test, Howard R.
• Primary Examiner(s): BARR, MICHAEL E
• Application Number:
  US10/122,064
• Time in Patent Office: 512 Days
• Field of Search: 427/98, 427/304, 427/305, 427/405, 427/437, 427/438, 427/443.1
• US Class Current: 427/97.1
• CPC Class Codes: C23C 18/1651 Two or more layers only obtained by electroless plating
• CPC Class Codes: C23C 18/1685 with supercritical condition, e.g. chemical fluid deposition
• CPC Class Codes: C23C 18/1831 Use of metal, e.g. activation, sensitisation with noble metals
• CPC Class Codes: C23C 18/32 Coating with nickel, cobalt or mixtures thereof with phosphorus or boron C23C18/50 takes precedence
• CPC Class Codes: C23C 18/54 Contact plating, i.e. electroless electrochemical plating
• CPC Class Codes: H01L 21/288 from a liquid, e.g. electrolytic deposition
• CPC Class Codes: H01L 2224/04042 Bonding areas specifically adapted for wire connectors, e.g. wirebond pads
• CPC Class Codes: H01L 2224/05083 Three-layer arrangements
• CPC Class Codes: H01L 2224/05147 Copper [Cu] as principal constituent
• CPC Class Codes: H01L 2224/05155 Nickel [Ni] as principal constituent
• CPC Class Codes: H01L 2224/05164 Palladium [Pd] as principal constituent
• CPC Class Codes: H01L 2224/05624 Aluminium [Al] as principal constituent
• CPC Class Codes: H01L 2224/05644 Gold [Au] as principal constituent
• CPC Class Codes: H01L 2224/05655 Nickel [Ni] as principal constituent
• CPC Class Codes: H01L 2224/45015 being circular
• CPC Class Codes: H01L 2224/45124 Aluminium (Al) as principal constituent
• CPC Class Codes: H01L 2224/45144 Gold (Au) as principal constituent
• CPC Class Codes: H01L 2224/45147 Copper (Cu) as principal constituent
• CPC Class Codes: H01L 2224/48463 the connecting portion on the bonding area of the semiconductor or solid-state body being a ball bond
• CPC Class Codes: H01L 2224/48624 Aluminium (Al) as principal constituent
• CPC Class Codes: H01L 2224/48644 : Gold (Au) as principal constituent
• CPC Class Codes: H01L 2224/48655 : Nickel (Ni) as principal constituent
• CPC Class Codes: H01L 2224/48724 : Aluminium (Al) as principal constituent
• CPC Class Codes: H01L 2224/48744 : Gold (Au) as principal constituent
• CPC Class Codes: H01L 2224/48755 : Nickel (Ni) as principal constituent
• CPC Class Codes: H01L 2224/48824 : Aluminium (Al) as principal constituent
• CPC Class Codes: H01L 2224/48844 : Gold (Au) as principal constituent
• CPC Class Codes: H01L 2224/48855 : Nickel (Ni) as principal constituent
• CPC Class Codes: H01L 2224/78 : Apparatus for connecting with wire connectors
• CPC Class Codes: H01L 2224/78301 : Capillary
• CPC Class Codes: H01L 2224/85045 : using a corona discharge, e.g. electronic flame off [EFO]
• CPC Class Codes: H01L 2224/85203 : Thermocompression bonding
• CPC Class Codes: H01L 2224/85205 : Ultrasonic bonding
• CPC Class Codes: H01L 24/03 : Manufacturing methods
• CPC Class Codes: H01L 24/05 : of an individual bonding area
• CPC Class Codes: H01L 24/45 : of an individual wire connector
• CPC Class Codes: H01L 24/48 : of an individual wire connector
• CPC Class Codes: H01L 24/85 : using a wire connector wire bonding in general B23K20/004
• 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 2924/00011 : Not relevant to the scope of the group, the symbol of which is combined with the symbol of this group
• CPC Class Codes: H01L 2924/00014 : the subject-matter covered by the group, the symbol of which is combined with the symbol of this group, being disclosed without further technical details
• CPC Class Codes: H01L 2924/00015 : the subject-matter covered by the group, the symbol of which is combined with the symbol of this group, being disclosed as prior art
• CPC Class Codes: H01L 2924/01004 : Beryllium [Be]
• CPC Class Codes: H01L 2924/01006 : Carbon [C]
• CPC Class Codes: H01L 2924/01013 : Aluminum [Al]
• CPC Class Codes: H01L 2924/01014 : Silicon [Si]
• CPC Class Codes: H01L 2924/01022 : Titanium [Ti]
• CPC Class Codes: H01L 2924/01024 : Chromium [Cr]
• CPC Class Codes: H01L 2924/01027 : Cobalt [Co]
• CPC Class Codes: H01L 2924/01028 : Nickel [Ni]
• CPC Class Codes: H01L 2924/01029 : Copper [Cu]
• CPC Class Codes: H01L 2924/01039 : Yttrium [Y]
• CPC Class Codes: H01L 2924/01042 : Molybdenum [Mo]
• CPC Class Codes: H01L 2924/01047 : Silver [Ag]
• CPC Class Codes: H01L 2924/01074 : Tungsten [W]
• 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 2924/04953 : TaN
• CPC Class Codes: H01L 2924/05042 : Si3N4
• CPC Class Codes: H01L 2924/10253 : Silicon [Si]
• CPC Class Codes: H01L 2924/14 : Integrated circuits
• CPC Class Codes: H01L 2924/20104 : Temperature range 100 C=<T<150 C, 373.15 K =< T < 423.15K
• CPC Class Codes: H01L 2924/20105 : Temperature range 150 C=<T<200 C, 423.15 K =< T < 473.15K
• CPC Class Codes: H01L 2924/20106 : Temperature range 200 C=<T<250 C, 473.15 K =<T < 523.15K
• CPC Class Codes: H01L 2924/20751 : larger or equal to 10 microns less than 20 microns
• CPC Class Codes: H01L 2924/20752 : larger or equal to 20 microns less than 30 microns
• CPC Class Codes: H01L 2924/20753 : larger or equal to 30 microns less than 40 microns
• CPC Class Codes: H01L 2924/3025 : Electromagnetic shielding

Abstract

An improved wire bonding process for copper-metallized integrated circuits is provided by a nickel layer that acts as a barrier against up-diffusing copper. In accordance with the present invention the nickel bath is placed and remains in hydrogen saturation by providing a piece of metal that remains in the nickel plating tank before and during the plating process.

Claims

1. A method for forming metallurgical connections between wires containing gold and bond pads positioned on integrated circuits having copper interconnecting metallization, comprising the steps of:

placing a nickel bath into a state of hydrogen saturation by plating a sufficient surface of dummy material and by maintaining the bath in hydrogen saturation by placing a plating specimen of sufficient size metal in the nickel bath before the following steps of;

activating the surface of said copper interconnecting surface, depositing seed metal,

plating a layer of nickel barrier metal that resists copper diffusion by electroless deposition in said nickel bath that is in continuous hydrogen saturation; and

plating a layer of bondable metal by electroless or immersion deposition.

2. The method of claim 1 wherein before plating a layer of bondable material, a palladium, platinum, cobalt or other suitable metal layer is plated over said nickel.

3. The method of claim 2 wherein said bondable material includes gold.

4. The method of claim 1 wherein before plating said nickel a seed material is deposited.

5. The method of claim 4 wherein said seed material is palladium.

6. The method of claim 1 wherein said size of said plating specimen represents a platable surface over 90 percent larger than the copper interconnecting surface.

7. The method of claim 1 wherein said platable area of said plating specimen is at least double the platable area of the copper interconnecting surface.

8. The method of claim 1 wherein said plating specimen is copper.

9. The method of claim 1 wherein said plating specimen is nickel.

10. The method of claim 1 wherein said plating specimen is a silicon wafer with a copper coating on at least one side.

11. The method of claim 1 wherein said plating specimen is provided by the steps of pre-cleaning the specimen of copper, nickel or a silicon wafer with a copper coating on at least one side, activating the surface of the specimen, conditioning, and placing in a nickel plating tank until production runs are terminated.

12. The method of claim 11 wherein said step of placing a nickel bath into a state of hydrogen saturation by plating a sufficient surface of dummy material is provided by starting with blanket copper wafers, pre-cleaning said wafers, activating, conditioning, and electroless nickel plating the blanket copper wafers for 30 minutes.