SACRIFICIAL SEED LAYER PROCESS FOR FORMING C4 SOLDER BUMPS

• US 20030155408A1
• Filed: 02/19/2002
• Published: 08/21/2003
• Est. Priority Date: 02/19/2002
• Status: Active Grant

• Current Assignee: Globalfoundries US Incorporated (GlobalFoundries, Inc.)
• Original Assignee: International Business Machines Corporation
• Inventors: Knarr, Randolph F., Srivastava, Kamalesh K., Fanti, Lisa A., Roggeman, Erik J.
• Granted Patent: US 6,622,907 B2
• Time in Patent Office: Days
• US Class Current: 228/215
• CPC Class Codes: B23K 35/001 Interlayers, transition pieces for metallurgical bonding of workpieces
• CPC Class Codes: B23K 35/007 at least one of the workpieces being of copper or another noble metal
• CPC Class Codes: H01L 21/2885 using an external electrical current, i.e. electro-deposition
• CPC Class Codes: H01L 2224/03912 the bump being used as a mask for patterning the bonding area
• CPC Class Codes: H01L 2224/03914 the bonding area, e.g. under bump metallisation [UBM], being used as a mask for patterning other parts
• CPC Class Codes: H01L 2224/0401 Bonding areas specifically adapted for bump connectors, e.g. under bump metallisation [UBM]
• CPC Class Codes: H01L 2224/05599 Material
• CPC Class Codes: H01L 2224/11472 Profile of the lift-off mask
• CPC Class Codes: H01L 2224/13023 the whole bump connector protruding from the surface
• CPC Class Codes: H01L 2224/13099 Material
• 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 24/11 Manufacturing methods for bumps on insulating substrates H01L21/4853
• 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 2924/01006 Carbon [C]
• CPC Class Codes: H01L 2924/01013 Aluminum [Al]
• CPC Class Codes: H01L 2924/01014 Silicon [Si]
• CPC Class Codes: H01L 2924/01015 Phosphorus [P]
• CPC Class Codes: H01L 2924/01019 Potassium [K]
• 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 2924/01033 : Arsenic [As]
• CPC Class Codes: H01L 2924/01047 : Silver [Ag]
• CPC Class Codes: H01L 2924/0105 : Tin [Sn]
• CPC Class Codes: H01L 2924/01059 : Praseodymium [Pr]
• CPC Class Codes: H01L 2924/01074 : Tungsten [W]
• CPC Class Codes: H01L 2924/01077 : Iridium [Ir]
• CPC Class Codes: H01L 2924/01078 : Platinum [Pt]
• CPC Class Codes: H01L 2924/01079 : Gold [Au]
• CPC Class Codes: H01L 2924/01082 : Lead [Pb]
• CPC Class Codes: H01L 2924/01322 : Eutectic Alloys, i.e. obtained by a liquid transforming into two solid phases
• CPC Class Codes: H01L 2924/01327 : Intermediate phases, i.e. intermetallics compounds
• CPC Class Codes: H01L 2924/014 : Solder alloys

Abstract

Start with a semiconductor substrate with contacts exposed through an insulating layer. Form a base over the contacts, with the base composed of at least one metal layer. Then form a conductive metal layer over the base. Form a mask over the top surface of the conductive metal layer with C4 solder bump openings therethrough with the shape of C4 solder bump images down to the surface of the conductive metal layer above the contacts. Etch away the exposed portions of the conductive metal layer below the C4 solder bump openings to form through holes in the conductive metal layer exposing C4 solder bump plating sites on the top surface of the base below the C4 solder bump openings with the conductive metal layer remaining intact on the periphery of the through holes at the C4 solder bump plating sites. As an option, form a barrier layer over the plating sites next. Form C4 solder bumps on the plating sites on the base/barrier layer within the C4 solder bump openings, with the C4 solder bumps being in contact with the conductive metal layer on the periphery of the through holes. Remove the mask. Etch away the remainder of the conductive metal layer, and etch away the base aside from the C4 solder bumps forming BLM pads. Then reflow the C4 solder bumps to form C4 solder balls.

Claims

1. A method of forming a solder structure on a substrate comprising:

starting with contacts exposed through an insulating layer and forming a base over the contacts, with the base having a top surface and being composed of at least one metal layer,

forming a conductive metal layer, with an upper surface, over the top surface of the base,

forming a mask over the top surface of the base, with the mask having C4 solder bump openings therethrough in the shape of C4 solder bump images down to the upper surface of the conductive metal layer above the contacts,

etching away the exposed portions of the conductive metal layer below the C4 solder bump openings forming through holes, with sidewalls, on the conductive metal layer down to the top surface of the base, thereby forming C4 solder bump plating sites on the top surface of the base, with the conductive metal layer remaining intact aside from the through holes,

depositing solder over the base to form C4 solder bumps filling the C4 solder bump plating sites within the C4 solder bump openings and through the sidewalls thereof to plate the solder in the solder bump openings,

then removing the mask,

then etching away the remainder of the conductive metal layer, and

then etching away the base aside from the C4 solder bumps thereby forming Ball Limiting Metallurgy (BLM) pads which are plated with the C4 solder bumps.

2. The method of claim 1 including forming the C4 solder bumps into C4 solder balls above the BLM pads.

3. The method of claim 1 including forming an intermediate metal layer above the one metal layer before forming the conductive metal layer.

4. The method of claim 1 including:

forming an intermediate metal layer above the one metal layer before forming the conductive metal layer, and

reflowing the C4 solder bumps to form C4 solder balls over the BLM pads.

5. The method of claim 1 including performing the step of filling the C4 solder bump openings with a barrier layer over the base, after etching away the exposed portions of the conductive metal layer below the C4 solder bump openings and before electroplating solder over the base to form C4 solder bumps.

6. The method of claim 1 including depositing the C4 solder bumps by providing an electroplating current through the conductive metal layer and through the sidewalls thereof to plate the solder in the solder bump openings with the C4 solder bumps being in contact with the conductive metal layer on the periphery of the through holes by providing an electroplating current passing through the conductive metal layer and through the sidewalls thereof to plate the solder in the solder bump openings.

7. The method of claim 1 including the conductive metal layer being formed by at least one of the metals selected from the group consisting of copper, gold, silver and platinum.

8. The method of claim 1 including forming an intermediate layer of metal above the one metal layer before forming the conductive metal layer.

9. A method of forming a solder ball on a substrate comprising:

starting with contacts exposed through an insulating layer and forming a base over the contacts, with the base having a top surface and being composed of at least one metal layer,

forming a conductive metal layer with an upper surface over the base,

forming a mask over the top surface of the conductive metal layer with C4 solder bump openings therethrough in the form of windows in the shape of C4 solder bump images down to the surface of the conductive metal layer above the contacts,

etching away the exposed portions of the conductive metal layer below the C4 solder bump openings, thereby forming through holes, with sidewalls, in the conductive metal layer exposing C4 solder bump plating sites on the top surface of the base below the C4 solder bump openings with the conductive metal layer remaining intact on the periphery of the through holes at the C4 solder bump plating sites,

plating solder onto the top surface of the base at the C4 solder bump plating sites filling the C4 solder bump openings by providing an electroplating current through the conductive metal layer and through the sidewalls thereof to plate the solder in the solder bump openings with the C4 solder bumps being in contact with the conductive metal layer on the periphery of the through holes by providing an electroplating current passing through the conductive metal layer and through the sidewalls thereof to plate the solder in the solder bump openings,

depositing solder over the base to form C4 solder bumps filling the C4 solder bump plating sites within the C4 solder bump openings and through the sidewalls thereof to plate the solder in the solder bump openings,

removing the mask, and

then etching away the base aside from the C4 solder bumps thereby forming Ball Limiting Metallurgy (BLM) pads which are plated with the C4 solder bumps.

10. The method of claim 9 including reflowing the C4 solder bumps to form a solder balls therefrom over the remaining base regions after the step of etching away the base aside from the C4 solder bumps leaving remaining base regions self-aligned with the C4 solder bumps.

11. The method of claim 9 including forming another metal layer above the adhesion metal layer before forming the conductive metal layer.

12. The method of claim 9 including:

forming an intermediate layer above the adhesion metal layer before forming the conductive metal layer,

reflowing the C4 solder bumps to form a solder balls over the BLM pads.

13. The method of claim 9 including depositing solder to form C4 solder bumps on the top surface of the base at the C4 solder bump plating sites filling the C4 solder bump openings by providing an electroplating current through the conductive metal layer and through the sidewalls thereof to plate the solder in the solder bump openings with the C4 solder bumps being in contact with the conductive metal layer on the periphery of the through holes by providing an electroplating current passing through the conductive metal layer and through the sidewalls thereof to plate the solder in the solder bump openings.

14. The method of claim 9 including the conductive metal layer being formed by at least one of the metals selected from the group consisting of copper (Cu), gold (Au), silver (Ag), and platinum (Pt).

15. A method of forming a solder ball on a substrate comprising:

starting with contacts exposed through an insulating layer and forming a base over the contacts, with the base having a top surface and being composed of at least one metal layer,

forming a conductive metal layer with a upper surface over the base,

forming a mask over the top surface of the conductive metal layer with C4 solder bump openings therethrough in the form of windows in the shape of C4 solder bump images down to the surface of the conductive metal layer above the contacts,

etching away the exposed portions of the conductive metal layer below the C4 solder bump openings, thereby forming through holes, with sidewalls, in the conductive metal layer exposing C4 solder bump plating sites on the top surface of the base below the C4 solder bump openings with the conductive metal layer remaining intact on the periphery of the through holes at the C4 solder bump plating sites,

depositing a barrier layer with a barrier surface over the top surface of the base,

plating solder onto the barrier surface at the C4 solder bump plating sites filling the C4 solder bump openings by providing an electroplating current through the conductive metal layer and through the sidewalls thereof to plate the solder in the solder bump openings with the C4 solder bumps being in contact with the conductive metal layer on the periphery of the through holes by providing an electroplating current passing through the conductive metal layer and through the sidewalls thereof to plate the solder in the solder bump openings,

depositing solder over the base to form C4 solder bumps filling the C4 solder bump plating sites within the C4 solder bump openings and through the sidewalls thereof to plate the solder in the solder bump openings,

removing the mask, and

then etching away the base aside from the C4 solder bumps thereby forming Ball Limiting Metallurgy (BLM) pads on which C4 solder bumps have been formed.

16. The method of claim 15 including the step of forming the C4 solder bumps into C4 solder balls above the BLM pads.

17. The method of claim 15 including:

the conductive metal layer being formed by at least one of the metals selected from the group consisting of copper (Cu), gold (Au), silver (Ag), and platinum (Pt),

the adhesion layer being composed of a material selected from the group consisting of tungsten and titanium/tungsten (TiW),

the intermediate layer being composed of CrCu, and

the barrier layer being composed of a material selected from the group consisting of nickel (Ni), nickel iron (NiFe) alloy, nickel phosphorus (NiP) alloy, cobalt (Co), and cobalt phosphorus (CoP) alloy.

18. The method of claim 15 including depositing solder to form C4 solder bumps on the barrier surface of the barrier layer filling the C4 solder bump openings by providing an electroplating current through the conductive metal layer and through the sidewalls thereof to plate the solder in the solder bump openings with the C4 solder bumps being in contact with the conductive metal layer on the periphery of the through holes by providing an electroplating current passing through the conductive metal layer and through the sidewalls thereof to plate the solder in the solder bump openings.

19. The method of claim 15 including the conductive metal layer being formed by at least one of the metals selected from the group consisting of copper (Cu), gold (Au), silver (Ag), and platinum (Pt).

20. The method of claim 15 including:

the conductive metal layer being formed by at least one of the metals selected from the group consisting of copper (Cu), gold (Au), silver (Ag), and platinum (Pt),

the adhesion layer being composed of a material selected from the group consisting of tungsten and titanium/tungsten (TiW), and

the intermediate layer being composed of CrCu.