Process and material for low-cost flip-chip solder interconnect structures

• US 6,746,896 B1
• Filed: 08/28/2000
• Issued: 06/08/2004
• Est. Priority Date: 08/28/1999
• Status: Expired due to Fees

• Current Assignee: Georgia Tech Research Corporation (University System of Georgia)
• Original Assignee: Georgia Tech Research Corporation (University System of Georgia)
• Inventors: Wong, Ching-Ping, Shi, Song-Hua
• Primary Examiner(s): NGUYEN, HA T
• Application Number:
  US09/648,777
• Time in Patent Office: 1,380 Days
• Field of Search: 438/108-110, 438/113, 438/118, 438/330
• US Class Current: 438/108
• CPC Class Codes: B23K 35/3613 Polymers, e.g. resins
• CPC Class Codes: H01L 21/563 Encapsulation of active face of flip-chip device, e.g. underfilling or underencapsulation of flip-chip, encapsulation preform on chip or mounting substrate
• CPC Class Codes: H01L 21/6835 using temporarily an auxiliary support
• CPC Class Codes: H01L 2221/6834 used to protect an active side of a device or wafer
• CPC Class Codes: H01L 2221/68354 used to support diced chips prior to mounting
• CPC Class Codes: H01L 2224/0401 Bonding areas specifically adapted for bump connectors, e.g. under bump metallisation [UBM]
• CPC Class Codes: H01L 2224/13111 Tin [Sn] as principal constituent
• CPC Class Codes: H01L 2224/16225 the item being non-metallic, e.g. insulating substrate with or without metallisation
• CPC Class Codes: H01L 2224/274 by blanket deposition of the material of the layer connector
• CPC Class Codes: H01L 2224/29111 Tin [Sn] as principal constituent
• CPC Class Codes: H01L 2224/2919 with a principal constituent of the material being a polymer, e.g. polyester, phenolic based polymer, epoxy
• CPC Class Codes: H01L 2224/73104 the bump connector being embedded into the layer connector
• CPC Class Codes: H01L 2224/73203 Bump and layer connectors
• CPC Class Codes: H01L 2224/73204 the bump connector being embedded into the layer connector
• CPC Class Codes: H01L 2224/81193 wherein the bump connectors are disposed on both the semiconductor or solid-state body and another item or body to be connected to the semiconductor or solid-state body
• CPC Class Codes: H01L 2224/8121 using a reflow oven
• CPC Class Codes: H01L 2224/81815 Reflow soldering
• CPC Class Codes: H01L 2224/83191 wherein the layer connectors are disposed only on the semiconductor or solid-state body
• CPC Class Codes: H01L 24/27 Manufacturing methods
• CPC Class Codes: H01L 24/29 of an individual layer connector
• CPC Class Codes: H01L 24/81 : using a bump 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 2924/01012 : Magnesium [Mg]
• CPC Class Codes: H01L 2924/01013 : Aluminum [Al]
• 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 2924/01073 : Tantalum [Ta]
• CPC Class Codes: H01L 2924/01075 : Rhenium [Re]
• CPC Class Codes: H01L 2924/01079 : Gold [Au]
• CPC Class Codes: H01L 2924/01082 : Lead [Pb]
• CPC Class Codes: H01L 2924/0132 : Binary Alloys
• 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 2924/04953 : TaN
• CPC Class Codes: H01L 2924/0665 : Epoxy resin
• CPC Class Codes: H01L 2924/1579 : with a principal constituent of the material being a polymer, e.g. polyester, phenolic based polymer, epoxy

Abstract

The present invention provides a novel process and its required fluxable materials for building low-cost flip-chip interconnect structures. The novel process involves two fluxable materials, fluxable wafer-level compressive-flow underfill material (WLCFU) and fluxable tacky film, and applies these two materials on a wafer level. The two materials can provide sufficient fluxing capability during solder reflow and significant improvement of the fatigue life of the formed solder interconnects after fully cured.

Claims

1. A wafer-level compressive-flow underfilling (WLCFU) process comprising the steps of:

applying a WLCFU material onto a surface of a bumped wafer in an amount sufficient to ensure that the thickness of the solidified WLCFU layer is less than the height of the wafer bumps;

solidifying the WLCFU material;

separating the WLCFU material coated wafer into individual chips;

covering the top of the bumps with a tacky film for promoting solder interconnects without intervening WLCFU material, wherein the tacky film and the WLCFU,material are not the same;

mounting the WLCFU material and tacky film coated individual chips to substrates; and

reflowing the solder bumps and curing the WLCFU material and tacky film simultaneously.

2. The wafer-level compressive-flow underfilling (WLCFU) process of claim 1, wherein said WLCFU material is a solvent-containing WLCFU material and said solidifying step includes the step of solidifying said WLCFU material by solvent removal.

3. The wafer-level compressive-flow underfilling (WLCFU) process of claim 1, wherein said WLCFU material is a solvent-free fluxing WLCFU material and said WLCFU solidifying step includes the step of solidifying said WLCFU material by cooling.

4. The wafer-level compressive-flow underfilling (WLCFU) process of claim 1, further comprising a post-curing step.

5. The wafer-level compressive-flow underfilling (WLCFU) process of claim 1, wherein said WLCFU material comprises:

a. an epoxy resin;

b. an organic curing hardener;

c. a latent curing catalyst;

d. a fluxing agent; and

e. a filler.

6. The wafer-level compressive-flow underfilling (WLCFU) process of claim 5, wherein said epoxy resin is selected from the group consisting of:

a cycloaliphatic epoxy resin, a bisphenol A epoxy resin, a bisphenol F epoxy resin, an epoxy novolac resin, a biphenyl epoxy resin, a naphthalene epoxy resin, a dicyclopentadiene-phenol epoxy resin, a reactive epoxy diluent, and any mixture thereof.

7. The wafer-level compressive-flow underfilling (WLCFU) process of claim 5, wherein said organic curing hardener is selected from the group consisting of:

a phenolic resins, an aromatic amine, a carboxylic acid anhydride, an imidazole, and an imidazole derivative.

8. The wafer-level compressive-flow underfilling (WLCFU) process of claim 5, wherein said curing catalyst is selected from the group consisting of:

a tertiary amine, a tertiary phosphine, an imidazole, an imidazole derivative, an imidazolium salt, a metal chelate, an onium salt, a quaternary phosphonium compound, 1,8-diazacyclo[5.4.0]undex-7-ene, and any mixture thereof.

9. The wafer-level compressive-flow underfilling (WLCFU) process of claim 5, wherein said fluxing agent comprises a compound containing a hydroxyl (—

CH) group.

10. The wafer-level compressive-flow underfilling (WLCFU) process of claim 5, wherein said fluxing agent comprises a compound containing a carboxylic (—

COOH) group.

11. The wafer-level compressive-flow underfilling (WLCFU) process of claim 5, wherein said filler is selected from the group consisting of:

a spherical fused silica filler, a silicon nitride filler, a silver flake filler, and a gold flake filler with diameters ranging from 0.1 μ

m to 50 μ

m.

12. The wafer-level compressive-flow underfilling (WLCFU) process of claim 5, wherein said WLCFU material further comprises a solvent.

13. The wafer-level compressive-flow underfilling (WLCFU) process of claim 12, wherein said solvent is an organic chemical having a boiling point between 25°

C. to 200°

C. which does not react with any other components in the WLCFU composition/formulation.

14. The wafer-level compressive-flow underfilling (WLCFU) process of claim 12, wherein said solvent is 4-methyl-2-pentanone.

15. The wafer-level compressive-flow underfilling (WLCFU) process of claim 5, wherein said WLCFU material further comprises an adhesion promoter.

16. The wafer-level compressive-flow underfilling (WLCFU) process of claim 15, wherein said adhesion promoter is selected from the group consisting of:

a silane coupling agent, a titanate, and a zirconate.

17. The wafer-level compressive-flow underfilling (WLCFU) process of claim 5, wherein said WLCFU material further comprises a surfactant.

18. The wafer-level compressive-flow underfilling (WLCFU) process of claim 17, wherein said surfactant is a non-ionic surfactant.

19. The wafer-level compressive-flow underfilling (WLCFU) process of claim 1, wherein said tacky film comprises:

a. an epoxy resin;

b. an organic curing hardener;

c. a latent curing catalyst; and

d. a fluxing agent.

20. The wafer-level compressive-flow underfilling (WLCFU) process of claim 19, wherein said tacky film is selected from the group consisting of:

a cycloaliphatic epoxy resin, a bisphenol A epoxy resin, a bisphenol F epoxy resin, an epoxy novolac resin, a biphenyl epoxy resin, a naphthalene epoxy resin, a dicyclopentadiene-phenol epoxy resin, a reactive epoxy diluent, and any mixture thereof.

21. The wafer-level compressive-flow underfilling (WLCFU) process of claim 19, wherein said organic curing hardener is selected from the group consisting of a phenolic resin, an aromatic amine, a carboxylic acid anhydride, an imidazole, and an imidazole derivative.

22. The wafer-level compressive-flow underfilling (WLCFU) process of claim 19, wherein said latent curing catalyst is selected from the group consisting of:

a tertiary amine, a tertiary phosphine, an imidazole, an imidazole derivative, an imidazolium salt, a metal chelate, an onium salts, a quaternary phosphonium compounds, 1,8-diazacyclo[5.4.0]undex-7-ene, and any mixture thereof.

23. The wafer-level compressive-flow underfilling (WLCFU) process of claim 19, wherein said fluxing agent comprises a compound containing a hydroxyl (—

OH) group.

24. The wafer-level compressive-flow underfilling (WLCFU) process of claim 19, wherein said fluxing agent comprises a compound containing a carboxylic (—

COOH) group.

25. The wafer-level compressive-flow underfilling (WLCFU) process of claim 19, wherein said tacky film further comprises an adhesion promoter.

26. The wafer-level compressive-flow underfilling (WLCFU) process of claim 25, wherein said adhesion promoter is selected from the group consisting of:

a silane coupling agent, a titanates, and a zirconate.

27. The wafer-level compressive-flow underfilling (WLCFU) process of claim 19, wherein said tacky film further comprises a surfactant.

28. The wafer-level compressive-flow underfilling (WLCFU) process of claim 27, wherein said surfactant is a non-ionic surfactant.