Method of forming an interconnect on a semiconductor substrate

• US 8,647,922 B2
• Filed: 11/08/2007
• Issued: 02/11/2014
• Est. Priority Date: 11/08/2007
• Status: Expired due to Fees

• Current Assignee: Nanyang Technology University
• Original Assignee: Nanyang Technology University
• Inventors: Zhou, Jijie, Chen, Zhong
• Primary Examiner(s): Gumedzoe, Peniel M
• Application Number:
  US11/937,210
• Publication Number:
  US 20090239338A1
• Time in Patent Office: 2,287 Days
• Field of Search: 438/478, 438/108, 24442-452, 977/796, 977/932, 977/E29.001, 977/E51.04
• US Class Current: 438/108
• CPC Class Codes: B82Y 10/00 Nanotechnology for information processing, storage or transmission, e.g. quantum computing or single electron logic
• CPC Class Codes: B82Y 30/00 Nanotechnology for materials or surface science, e.g. nanocomposites
• CPC Class Codes: H01L 2224/0401 Bonding areas specifically adapted for bump connectors, e.g. under bump metallisation [UBM]
• CPC Class Codes: H01L 2224/05552 in top view
• CPC Class Codes: H01L 2224/05568 the whole external layer 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 23/53276 containing carbon, e.g. fullerenes superconducting fullerenes H10N60/853
• 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 24/13 of an individual bump connector
• CPC Class Codes: H01L 24/16 of an individual bump connector
• CPC Class Codes: H01L 2924/0001 Technical content checked by a classifier
• CPC Class Codes: H01L 2924/00015 the subject-matter covered by the group, the symbol of which is combined with the symbol of this group, being disclosed as prior art
• CPC Class Codes: H01L 2924/0002 Not covered by any one of groups H01L24/00, H01L24/00 and H01L2224/00
• 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 2924/01019 Potassium [K]
• CPC Class Codes: H01L 2924/01022 : Titanium [Ti]
• CPC Class Codes: H01L 2924/01023 : Vanadium [V]
• CPC Class Codes: H01L 2924/01024 : Chromium [Cr]
• CPC Class Codes: H01L 2924/01029 : Copper [Cu]
• CPC Class Codes: H01L 2924/0103 : Zinc [Zn]
• CPC Class Codes: H01L 2924/01033 : Arsenic [As]
• CPC Class Codes: H01L 2924/01042 : Molybdenum [Mo]
• CPC Class Codes: H01L 2924/01047 : Silver [Ag]
• CPC Class Codes: H01L 2924/01049 : Indium [In]
• CPC Class Codes: H01L 2924/01074 : Tungsten [W]
• 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 2924/01322 : 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 2924/14 : Integrated circuits

Abstract

The present invention relates to a method of forming a wire bond-free conductive interconnect area on a semiconductor substrate. A semiconductor substrate with an electrically conductive protrusion, defining a bond pad, is provided as well as a plurality of carbon nanotubes. The plurality of carbon nanotubes is immobilized on the bond pad by allowing at least one random portion along the length of the carbon nanotubes to attach to the surface of the bond pad. Thus an aggregate of loops of carbon nanotubes is formed on the surface of the bond pad. Thereby a conductive interconnect area is formed on the electrically conductive protrusion without heat treatment.

Claims

1. A method of forming a wire bond-free conductive interconnect area on a semiconductor substrate, the method comprising:

providing a semiconductor substrate, said semiconductor substrate comprising an electrically conductive protrusion defining a bond pad;

providing a plurality of electrically conductive nanofilaments; and

immobilizing the plurality of electrically conductive nanofilaments on the electrically conductive protrusion by allowing at least one random portion of the electrically conductive nanofilaments along the length thereof to attach to the surface of the electrically conductive protrusion, and

deflecting a plurality of the electrically conductive nanofilaments attached to the surface of the electrically conductive protrusion forming an aggregate of loops of electrically conductive nanofilaments on the surface of the electrically conductive protrusion, thereby forming a conductive interconnect area on the electrically conductive protrusion without heat treatment; and

wherein the plurality of electrically conductive nanofilaments is dispersed in a liquid and is immobilized and deflected on the electrically conductive protrusion according to one of

A) by dielectrophoresis; and

B) by (i) depositing the plurality of electrically conductive nanofilaments dispersed in the liquid on the electrically conductive protrusion and (ii) allowing a portion of the liquid to be removed, thereby allowing the surface tension of the liquid to force the plurality of electrically conductive nanofilaments to contact the surface of the conductive protrusion; and

wherein the electrically conductive nanofilaments are selected to be of a flexibility that allows the surface tension of the liquid to deflect the electrically conductive nanofilaments dispersed therein upon contact with the surface of the liquid.

2. The method of claim 1, wherein immobilizing the plurality of electrically conductive nanofilaments on the electrically conductive protrusion is carried out at about nominal room temperature.

3. The method of claim 1, wherein the liquid comprises at least one of water, an alcohol and a polar ionic liquid.

4. The method of claim 1, wherein allowing a portion of the liquid to be removed is carried out by allowing a portion of the liquid to evaporate.

5. The method of claim 1, wherein the electrically conductive nanofilaments are selected from the group consisting of metal nanowires, semiconductor nanowires, nanofilaments of a metal compound, nanofilaments of a polymer, boron nitride nanotubes and carbon nanotubes.

6. The method of claim 5, wherein the carbon nanotubes are non-functionalized.

7. The method of claim 1, wherein the electrically conductive protrusion has a circumferential edge, and wherein the plurality of electrically conductive nanofilaments is immobilized at least essentially adjacent to said edge, thereby forming a central bare area on the electrically conductive protrusion in that said central bare area is at least essentially void of electrically conductive nanofilaments.

8. A method of interconnecting two semiconductor substrates in a wire bond-free manner, the method comprising:

providing a first semiconductor substrate, said first semiconductor substrate comprising a first electrically conductive protrusion defining a first bond pad;

providing a second semiconductor substrate, said second semiconductor substrate comprising a second electrically conductive protrusion defining a second bond pad;

providing a first plurality of electrically conductive nanofilaments;

immobilizing the first plurality of electrically conductive nanofilaments on the first electrically conductive protrusion by allowing at least one random portion of said electrically conductive nanofilaments along the length thereof to attach to the surface of the first electrically conductive protrusion, and

deflecting a plurality of the electrically conductive nanofilaments attached to the surface of the first electrically conductive protrusion forming a first aggregate of loops of electrically conductive nanofilaments on the surface of the first electrically conductive protrusion, thereby forming a first conductive interconnect area on the first electrically conductive protrusion without heat treatment;

providing a second plurality of electrically conductive nanofilaments;

immobilizing the second plurality of electrically conductive nanofilaments on the second electrically conductive protrusion by allowing at least one random portion of said electrically conductive nanofilaments along the length thereof to attach to the surface of the second electrically conductive protrusion, and

deflecting a plurality of the electrically conductive nanofilaments attached to the surface of the second electrically conductive protrusion forming a second aggregate of loops of electrically conductive nanofilaments on the surface of the second electrically conductive protrusion,

thereby forming a second conductive interconnect area on the second electrically conductive protrusion without heat treatment; and

contacting the first electrically conductive protrusion, on which the first plurality of electrically conductive nanofilaments is immobilized, with the second electrically conductive protrusion, on which the second plurality of electrically conductive nanofilaments is immobilized, thereby allowing non-covalent interaction between the first and the second aggregate of loops of electrically conductive nanofilaments to join the first and the second electrically conductive protrusion together; and

wherein the first and/or second plurality of electrically conductive nanofilaments is dispersed in a liquid and is immobilized and deflected on the electrically conductive protrusion according to one of

A) by dielectrophoresis; and

B) by (i) depositing the plurality of electrically conductive nanofilaments dispersed in the liquid on the electrically conductive protrusion and (ii) allowing a portion of the liquid to be removed, thereby allowing the surface tension of the liquid to force the plurality of electrically conductive nanofilaments to contact the surface of the conductive protrusion; and

wherein the electrically conductive nanofilaments are selected to be of a flexibility that allows the surface tension of the liquid to deflect the electrically conductive nanofilaments dispersed therein upon contact with the surface of the liquid.

9. The method of claim 8, wherein the non-covalent interaction is at least one of a Casimir interaction, a hydrophobic interaction, hydrogen bonding, a solvation force and a Van-der-Waals interaction.

10. The method of claim 8, wherein contacting the first electrically conductive protrusion with the second electrically conductive protrusion is carried out by (i) aligning the first semiconductor substrate and the second semiconductor substrate such that the first electrically conductive protrusion on the first semiconductor substrate and the second electrically conductive protrusion on the second semiconductor substrate face each other, and (ii) applying mechanical force, thereby pressing the first semiconductor substrate against the second semiconductor substrate.

11. The method of claim 8, wherein immobilizing the first plurality of electrically conductive nanofilaments on the first electrically conductive protrusion is carried out at about nominal room temperature.

12. The method of claim 8, wherein immobilizing the second plurality of electrically conductive nanofilaments on the second electrically conductive protrusion is carried out at about nominal room temperature.

13. The method of claim 8, wherein the electrically conductive nanofilaments of the first plurality of electrically conductive nanofilaments are selected from the group consisting of metal nanowires, semiconductor nanowires, nanofilaments of a metal compound, nanofilaments of a polymer, boron nitride nanotubes and carbon nanotubes.

14. The method of claim 8, wherein the electrically conductive nanofilaments of the second plurality of electrically conductive nanofilaments are selected from the group consisting of metal nanowires, semiconductor nanowires, nanofilaments of a metal compound, nanofilaments of a polymer, boron nitride nanotubes and carbon nanotubes.

15. The method of claim 8, wherein the method is a method of forming a flip chip.

16. A method of interconnecting two semiconductor substrates in a wire bond-free manner, the method comprising:

providing a first semiconductor substrate, said first semiconductor substrate comprising an electrically conductive protrusion defining a first bond pad;

providing a first plurality of electrically conductive nanofilaments;

immobilizing the first plurality of electrically conductive nanofilaments on the first electrically conductive protrusion by at least one random portion of the electrically conductive nanofilaments along the length thereof to attach to the surface of the first electrically conductive protrusion;

deflecting a plurality of the electrically conductive nanofilaments attached to the surface of the first electrically conductive protrusion forming an aggregate of loops of electrically conductive nanofilaments on the surface of the first electrically conductive protrusion, thereby forming a first conductive interconnect area on the first electrically conductive protrusion without heat treatment;

providing a second semiconductor substrate, said second semiconductor substrate comprising a second electrically conductive protrusion defining a second bond pad, wherein on the second electrically conductive protrusion there is immobilized a second plurality of electrically conductive nanofilaments, wherein each electrically conductive nanofilament of the second plurality of electrically conductive nanofilaments has a free end; and

contacting the first electrically conductive protrusion, on which the first plurality of electrically conductive nanofilaments is immobilized, with the second electrically conductive protrusion, on which the second plurality of electrically conductive nanofilaments is immobilized, thereby allowing the free ends of the second plurality of electrically conductive nanofilaments on the second electrically conductive protrusion to enter the loops of the aggregate of the first plurality of electrically conductive nanofilaments on the first electrically conductive protrusion; and

wherein the first and/or second plurality of electrically conductive nanofilaments is dispersed in a liquid and is immobilized and/or deflected on the electrically conductive protrusion according to one of

A) by dielectrophoresis; and

B) by (i) depositing the plurality of electrically conductive nanofilaments dispersed in the liquid on the electrically conductive protrusion and (ii) allowing a portion of the liquid to be removed, thereby allowing the surface tension of the liquid to force the plurality of electrically conductive nanofilaments to contact the surface of the conductive protrusion; and

wherein the electrically conductive nanofilaments are selected to be of a flexibility that allows the surface tension of the liquid to deflect the electrically conductive nanofilaments dispersed therein upon contact with the surface of the liquid.

17. The method of claim 16, wherein the second plurality of electrically conductive nanofilaments defines an array.

18. The method of claim 16, wherein the electrically conductive nanofilaments of the first plurality of electrically conductive nanofilaments are selected from the group consisting of metal nanowires, semiconductor nanowires, nanofilaments of a metal compound, nanofilaments of a polymer, boron nitride nanotubes and carbon nanotubes.

19. The method of claim 16, wherein the electrically conductive nanofilaments of the second plurality of electrically conductive nanofilaments are selected from the group consisting of metal nanowires, semiconductor nanowires, nanofilaments of a metal compound, nanofilaments of a polymer, boron nitride nanotubes and carbon nanotubes.

20. The method of claim 19, wherein allowing the free ends of the second plurality of electrically conductive nanofilaments to enter the loops of the aggregate of the first plurality of electrically conductive nanofilaments comprises allowing non-covalent interaction between the electrically conductive nanofilaments of the first and the second plurality of electrically conductive nanofilaments, thereby joining the first and the second electrically conductive protrusion together.

21. The method of claim 19, wherein the free ends of the carbon nanotubes of the second plurality of carbon nanotubes have a nano hook and wherein contacting the first electrically conductive protrusion with the second electrically conductive protrusion includes allowing the hooks of the second plurality of electrically conductive nanofilaments on the second electrically conductive protrusion to catch the loops of the aggregate of the first plurality of electrically conductive nanofilaments on the first electrically conductive protrusion.

22. A method of forming a wire bond-free conductive interconnect area on a semiconductor substrate, the method comprising:

providing a semiconductor substrate, said semiconductor substrate comprising an electrically conductive protrusion defining a bond pad;

providing a plurality of electrically conductive nanofilaments; and

immobilizing the plurality of electrically conductive nanofilaments on the electrically conductive protrusion forming an aggregate of loops of electrically conductive nanofilaments on the surface of the electrically conductive protrusion according to the method steps of;

(i) depositing the plurality of electrically conductive nanofilaments on the electrically conductive protrusion;

(ii) dispersing said plurality of electrically conductive nonofilaments desposited on said electrically conductive protrusion in a liquid;

(iii) removing a portion of the liquid containing the plurality of electrically conductive nanofilaments, generating a surface tension between the nanofilaments and the remaining liquid;

(iv) deflecting and bending the electrically conductive nanofilaments dispersed in said liquid with said generated surface tension;

(v) forcing a plurality of said electrically conductive nanofilaments to contact the surface of the conductive protrusion with said generated surface tension;

(vi) attaching random portions of the plurality of electrically conductive nanofilaments to the surface of the electrically conductive protrusion through said forced contact, thereby forming a conductive interconnect area on the electrically conductive protrusion without heat treatment.

23. The method according to claim 22 further comprising the method steps of:

providing a plurality of electrically conductive nanofilaments in the form of electrically conductive nanotubes;

immobilizing the plurality of electrically conductive nanotubes on the electrically conductive protrusion on the surface of the electrically conductive protrusion according to the method steps of;

(i) depositing the plurality of electrically conductive nanotubes on the electrically conductive protrusion;

(ii) dispersing said plurality of electrically conductive nanotubes deposited on said electrically conductive protrusion in a liquid;

(iii) removing a portion of the liquid containing the plurality of conductive nanotubes, generating capillary forces on the nanotubes;

(iv) forcing a plurality of said electrically conductive nanofilaments to contact the surface of the conductive protrusion with said generated capillary forces.