Method of flip-chip assembly of two electronic components by UV annealing, and assembly obtained

Patent metadata

Field	Value
Publication number	US-9613924-B2
Application number	US-201414902426-A
Country	US
Kind code	B2
Filing date	Jul 1, 2014
Priority date	Jul 2, 2013
Publication date	Apr 4, 2017
Grant date	Apr 4, 2017

Abstract

The invention concerns a method of flip-chip assembly between first ( 1 ) and second ( 2 ) components each comprising connection pads ( 11, 21 ) on one of the faces of same, referred to as assembly faces, which involves transferring the components onto each other via the assembly faces of same in such a way as to create electrical interconnections between the pads of the first and second components. The invention involves transforming the copper oxide into copper by UV annealing, very locally, in the gap between the components, at least around the areas adjacent to the connection pads. The method according to the invention can be used for any component that is transparent to UV rays, including for substrates made from a plastic material such as substrates made from PEN or PET. The invention also concerns the assembly of two components obtained by the method.

First claim

The invention claimed is:

1. A process for flip-chip assembly of a first component and a second component, each component including connection pads on one of their faces, called their assembly faces, in which the components are added one to the other via their assembly faces so as to produce electrical interconnections between the pads of the first and those of the second component, the process including the following steps:
a/ producing the first component with its connection pads, the first component being made of a material that is transparent to ultraviolet (UV) radiation in zones, called emission zones, each of said emission zones being defined around a pad, the pads of the first component being made of a material that absorbs or reflects UV radiation;
b/ depositing copper oxide (CuO) on the first component at least on its connection pads and in the emission zones;
c/ producing the second component with its connection pads, the connection pads of the second component being made of a material that reflects UV radiation, each of said pads being suitable for reflectively focusing ultraviolet radiation arriving from an emission zone onto one of the pads of the first component, and, depending on the circumstances, onto each metal protuberance formed on a pad of the second component;
d/ forming interconnection metal protuberances on at least some of the pads of the second component;
e/ aligning the first and second components and adding them one to the other via their assembly faces; and
f/ applying UV radiation through the emission zones of the first component to the deposited copper oxide so as to carry out a UV anneal that converts the deposited copper oxide into copper and, depending on the circumstances, makes the interconnection protuberances melt.

2. The assembly process as claimed in claim 1 , in which the first component includes a substrate made of a material that is transparent to UV.

3. The assembly process as claimed in claim 2 , wherein the substrate made of transparent material is surmounted, on the same side as its assembly face, with an electrically insulating layer made of a material that absorbs or reflects UV radiation, said layer defining the emission zones.

4. The assembly process as claimed in claim 3 , wherein the constituent material of the layer defining the emission zones is chosen from a titanium oxide, such as TiO 2 , zinc oxide (ZnO), zirconium oxide (ZrO 2 ) and molecules of pyrene dissolved in acetone.

5. The assembly process as claimed in claim 2 , wherein the substrate made of transparent material is surmounted, on the same side as its assembly face, with a layer made of a material that absorbs or reflects UV radiation and electrically insulated from the emission zones and connection pads.

6. The assembly process as claimed in claim 5 , wherein the constituent material of the layer electrically insulated from the emission zones and connection pads is a metal such as gold (Au), titanium (Ti) or nickel (Ni).

7. The assembly process as claimed in claim 1 , wherein the first component is a substrate made of transparent material and in which the emission zones are defined by drops of a solvent that absorbs UV radiation added to copper oxide (CuO).

8. The assembly process as claimed in claim 7 , wherein the solvent is chosen from water, acetonitrile, pentane, n-hexane, cyclohexane and cyclopentane.

9. The assembly process as claimed in claim 1 , wherein step b/ is carried out by depositing CuO in the form of an ink in order to produce a film covering the assembly face of the first component.

10. The process as claimed in claim 9 , wherein, between steps e/ and f/, a step e1/ of thermally annealing the copper oxide (CuO) ink is carried out between 90 and 100° C. for a time of 10 min to 30 min so as to thermally activate the copper oxide.

11. The assembly process as claimed in claim 1 , wherein the UV radiation applied in step f/ consists in a photonic pulse of a duration comprised between 0.5 and 2 milliseconds (ms) having an energy comprised between 10 and 20 joules/cm 2 .

12. An assembly of a first component and a second component, each component including connection pads on one of their faces, called their assembly faces, in which:
the first component is made of a material that is transparent to ultraviolet radiation (UV) at least in zones, called emission zones, and includes connection pads made of a material that absorbs or reflects UV radiation, said pads each being bounded by emission zones; and
the second component includes connection pads made of a material that reflects UV radiation,
the assembly including:
interconnection zones made of copper (Cu) each filling the space at least between the emission zones of the first component and a pad of the second component; and
depending on the circumstances, metal protuberances each reflowed in an interconnection zone between a pad of the first component and a pad of the second component.

13. The assembly as claimed in claim 12 , the first component including a substrate made of a material that is transparent to UV.

14. The assembly as claimed in claim 13 , the substrate being made of polyethylene naphthalate (PEN), polyethylene terephthalate (PET) or of glass.

15. The assembly as claimed in claim 12 , the connection pads of the second component being made of a material that reflects UV radiation and having a recessed, Isosceles-triangle shape relative to the assembly face.

16. The assembly as claimed in claim 15 , the angle α at the base, angle formed between the two sides of the Isosceles triangle and the assembly face of the second component, being smaller than 40°.

17. The assembly as claimed in claim 12 , the connection pads of the second component being made of a material that reflects UV radiation and having a concave shape relative to the assembly face, the concave shape consisting of a parabolic or cylinder segment.

18. The assembly as claimed in claim 12 , the connection pads of the first component being made of a material that reflects UV radiation.

19. The assembly as claimed in claim 12 , the connection pads of the second component being produced in the form of a metal layer the metal of which is chosen from aluminum (Al), gold (Au), titanium (Ti), nickel (Ni) and platinum (Pt), or of a metal bilayer chosen from nickel surmounted with gold (Ni/Au) and nickel surmounted with platinum (Ni/Pt).

20. The assembly as claimed in claim 12 , the constituent material of the interconnection protuberances being chosen from indium (In), an aluminum-copper alloy (AlCu), tin (Sn) and a gold-tin alloy (AuSn).

21. The assembly as claimed in claim 12 , the second component being a chip, in particular a silicon chip, and the first component being a substrate made of transparent material surmounted, on the same side as its assembly face, with a layer that absorbs UV radiation, defining the emission zones.

Assignees

• Commissariat Energie Atomique

Inventors

• Aliane Abdelkader
• Revaux Amélie

Classifications

• H10W90/724

  between a chip and a stacked insulating package substrate, interposer or RDL · CPC title

• H10W74/15

  on active surfaces of flip-chip devices, e.g. underfills · CPC title

• H10W72/9415

  relative to the surface, e.g. recessed, protruding · CPC title

• H10W72/07335

  Applying EM radiation, e.g. induction heating or using a laser · CPC title

• H10W72/07323

  Active alignment, e.g. using optical alignment using marks or sensors · CPC title