Flip chip assembly

• US 6,348,738 B1
• Filed: 08/11/1999
• Issued: 02/19/2002
• Est. Priority Date: 09/23/1997
• Status: Expired due to Fees

• Current Assignee: GlobalFoundries, Inc.
• Original Assignee: International Business Machines Corporation
• Inventors: Ouellet, Luc, Ouellet, Charles, Dery, Jean, Questad, David L., Egitto, Frank D., Matienzo, Luis J., Tran, Son K., Rudik, William J.
• Primary Examiner(s): Williams, Alexander O.
• Application Number:
  US09/371,975
• Time in Patent Office: 923 Days
• Field of Search: 257/777-780, 257/737, 257/738, 257/734, 257/787, 257/784, 257/786
• US Class Current: 257/778
• 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 2224/16 of an individual bump connector
• CPC Class Codes: H01L 2224/29099 Material
• 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 2224/73203 Bump and layer connectors
• CPC Class Codes: H01L 2224/73204 the bump connector being embedded into the layer connector
• CPC Class Codes: H01L 2224/81191 wherein the bump connectors are disposed only on the semiconductor or solid-state body
• CPC Class Codes: H01L 2224/83102 using surface energy, e.g. capillary forces
• CPC Class Codes: H01L 2224/92125 the second connecting process involving a layer connector
• CPC Class Codes: H01L 24/28 Structure, shape, material or disposition of the layer connectors prior to the connecting process
• CPC Class Codes: H01L 24/45 of an individual wire connector
• 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 2924/00013 Fully indexed content
• 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 2924/01018 Argon [Ar]
• CPC Class Codes: H01L 2924/01033 Arsenic [As]
• CPC Class Codes: H01L 2924/01039 : Yttrium [Y]
• CPC Class Codes: H01L 2924/01078 : Platinum [Pt]
• CPC Class Codes: H01L 2924/01079 : Gold [Au]
• CPC Class Codes: H01L 2924/14 : Integrated circuits
• CPC Class Codes: H01L 2924/3512 : Cracking
• CPC Class Codes: Y10S 438/959 : Mechanical polishing of wafer

Abstract

A method for forming a flip-chip-on-board assembly. An integrated circuit (IC) chip having a polyimide passivation layer is joined to a chip carrier via a plurality of solder bumps which electrically connect a plurality of contact pads on the IC chip to corresponding contacts on the chip carrier. A space is formed between a surface of the passivation layer and a surface of the chip carrier. A plasma is applied, to chemically modify the surface of the chip carrier and the passivation layer of the IC chip substantially without roughening the surface of the passivation layer. The plasma is either an O₂ plasma or a microwave-generated Ar and N₂O plasma. An underfill encapsulant material is applied to fill the space. The plasma treatment may be performed after the step of joining. Then, the chip and chip carrier are treated with the plasma simultaneously. Alternatively, the IC chip and chip carrier may be treated with the plasma before they are joined to one another. The plasma treatment improves adhesion between the encapsulant and the IC chip, and between the encapsulant and the chip carrier.

Claims

1. A flip-chip-on-board assembly, comprising:

an integrated circuit (IC) chip having an insulation layer with a surface, which has been treated with a plasma to chemically modify the surface of the insulation layer substantially without roughening the surface of the insulation layer, the IC chip having a plurality of electrical contact pads;

a chip carrier having a surface and a plurality of electrical contacts on the surface of the chip carrier;

a plurality of solder bumps, each bump electrically connecting one of the plurality of contact pads of the IC chip to a respective one of the contacts of the chip carrier, such that a space is formed between the surface of the insulation layer and the surface of the chip carrier; and

an underfill encapsulant material filling the space.

2. The flip-chip-on-board assembly according to claim 1, wherein the chip carrier has been treated with the plasma to chemically modify the surface of the chip carrier.

3. The flip-chip-on-board assembly according to claim 1, wherein the insulation layer is formed from a material that includes a hydrocarbon component.

4. The flip-chip-on-board assembly according to claim 1, wherein the insulation layer consists of polyimide.

5. The flip-chip-on-board assembly according to claim 1, wherein the chip carrier includes a laminate covered by the surface of the chip carrier, and the surface of the chip carrier comprises an epoxy resin solder mask having inorganic filler particles.

6. The flip-chip-on-board assembly according to claim 1, wherein the insulation layer is sufficiently smooth so that no roughness is detectable by a s canning electron microscope.

7. The flip-chip-on-board assembly according to claim 1, wherein the plasma is one of the group consisting of O₂ plasma and a microwave-generated Ar and N₂O plasma.