Copper bond pad process

• US 6,218,732 B1
• Filed: 07/15/1999
• Issued: 04/17/2001
• Est. Priority Date: 09/15/1998
• Status: Expired due to Term

• Current Assignee: Texas Instruments, Inc.
• Original Assignee: Texas Instruments, Inc.
• Inventors: Russell, Stephen W., Lu, Jiong-Ping
• Primary Examiner(s): Lee, Eddie C.
• Assistant Examiner(s): CLARK, JASMINE JHIHAN B
• Application Number:
  US09/354,510
• Time in Patent Office: 642 Days
• Field of Search: 257/748, 257/751, 257/758, 252/762, 252/784, 438/687
• US Class Current: 257/748
• CPC Class Codes: H01L 2224/04042 Bonding areas specifically adapted for wire connectors, e.g. wirebond pads
• 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 2224/48 of an individual wire connector
• CPC Class Codes: H01L 2224/85375 having an external coating, e.g. protective bond-through coating
• CPC Class Codes: H01L 24/02 Bonding areas on insulating substrates, e.g. chip carriers, H01L23/49816, H01L23/49838, H01L23/5389; Manufacturing methods related thereto
• 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 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 2924/01005 Boron [B]
• CPC Class Codes: H01L 2924/01006 Carbon [C]
• CPC Class Codes: H01L 2924/01007 Nitrogen [N]
• 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 2924/01029 Copper [Cu]
• CPC Class Codes: H01L 2924/01033 Arsenic [As]
• CPC Class Codes: H01L 2924/0105 Tin [Sn]
• CPC Class Codes: H01L 2924/01073 Tantalum [Ta]
• CPC Class Codes: H01L 2924/01074 : Tungsten [W]
• CPC Class Codes: H01L 2924/01079 : Gold [Au]
• CPC Class Codes: H01L 2924/01084 : Polonium [Po]
• CPC Class Codes: H01L 2924/01327 : Intermediate phases, i.e. intermetallics compounds
• CPC Class Codes: H01L 2924/014 : Solder alloys
• CPC Class Codes: H01L 2924/04941 : TiN
• CPC Class Codes: H01L 2924/04953 : TaN
• CPC Class Codes: H01L 2924/05042 : Si3N4
• CPC Class Codes: H01L 2924/14 : Integrated circuits

Abstract

An integrated circuit utilizing copper wiring has copper bond pads which are covered with a passivation layer to prevent unwanted reactions of the copper with metals which are bonded to it. The passivation layer can be an intermetallic of copper and titanium or a stacked layer of CuTix/TiN. Various nitrides can also be used, such as tungsten nitride, tantalum nitride, titanium silicon nitride, tungsten silicon nitride, and tantalum silicon nitride.

Claims

1. A bond pad structure for an integrated circuit, said bond pad structure comprising:

a first layer primarily comprising copper, having connections to underlying circuitry, said first layer being partially overlain by a protective overcoat layer;

a passivation layer, directly overlying only said first layer, which prevents said copper from reacting with materials which are bonded to said bond pad structure.

2. The integrated circuit of claim 1, wherein said passivation layer comprises titanium.

3. The integrated circuit of claim 1, wherein said passivation layer comprises titanium nitride.

4. The integrated circuit of claim 1, further comprising a wire bonded to said passivation layer.

5. A fabrication method, comprising the steps of:

(a.) forming an integrated circuit structure having a copper metallization layer;

(b.) forming a protective overcoat layer which partially overlies said copper metallization layer;

(c.) forming a passivation layer directly over only portions of said copper metallization layer exposed under said protective overcoat layer.

6. The method of claim 5, wherein said passivation layer comprises titanium.

7. The method of claim 5, further comprising bonding a wire to said passivation layer.

8. A fabrication method, comprising the steps of:

(a.) forming an integrated circuit structure having a copper metallization layer;

(b.) forming a protective overcoat layer which partially overlies said copper metallization layer;

(c.) forming a passivation layer over portions of said copper metallization layer exposed under said protective overcoat layer by

(1) depositing a layer of titanium over said copper metallization;

(2) annealing said layer of titanium to react with the copper metallization to form CuTi_x; and

(3) removing any unreacted portions of said titanium layer.

9. The fabrication method of claim 8, wherein said annealing step is conducted in a nitrogen-containing ambient and forms a layer of TiN over said CuTi_x.

10. The fabrication method of claim 8, further comprising the step of bonding a wire to said passivation layer.

11. The fabrication method of claim 8, further comprising the step of forming solder balls on said passivation layer.