High-density interconnection of temperature sensitive electronic devices

• US 6,716,669 B2
• Filed: 10/31/2002
• Issued: 04/06/2004
• Est. Priority Date: 08/02/2002
• Status: Active Grant

• Current Assignee: Gula Consulting Limited Liability Company (Intellectual Ventures LLC)
• Original Assignee: BAE Systems Information and Electronic Systems Integration Incorporated (BAE Systems Plc)
• Inventors: Erikson, Kenneth R., Marciniec, John W.
• Primary Examiner(s): Nhu, David
• Application Number:
  US10/284,999
• Publication Number:
  US 20040023433A1
• Time in Patent Office: 523 Days
• Field of Search: 438/26, 438/55, 438/64, 438/106, 438/107, 438/108, 438/612, 438/613, 438/618
• US Class Current: 438/106
• CPC Class Codes: B81B 7/0006 Interconnects
• CPC Class Codes: H01L 21/4853 Connection or disconnection of other leads to or from a metallisation, e.g. pins, wires, bumps
• CPC Class Codes: H01L 2224/05001 Internal layers
• CPC Class Codes: H01L 2224/05026 the internal layer being disposed in a recess of the surface
• CPC Class Codes: H01L 2224/0508 being stacked
• CPC Class Codes: H01L 2224/05155 Nickel [Ni] as principal constituent
• CPC Class Codes: H01L 2224/05171 Chromium [Cr] as principal constituent
• CPC Class Codes: H01L 2224/05571 the external layer being disposed in a recess of the surface
• CPC Class Codes: H01L 2224/05644 Gold [Au] as principal constituent
• CPC Class Codes: H01L 2224/05655 Nickel [Ni] as principal constituent
• CPC Class Codes: H01L 2224/1147 using a lift-off mask
• CPC Class Codes: H01L 2224/13099 Material
• CPC Class Codes: H01L 2224/13111 Tin [Sn] as principal constituent
• 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 2224/81801 Soldering or alloying
• 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 24/12 Structure, shape, material or disposition of the bump connectors prior to the connecting process
• CPC Class Codes: H01L 24/16 of an individual bump 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 2924/01015 : Phosphorus [P]
• CPC Class Codes: H01L 2924/01024 : Chromium [Cr]
• CPC Class Codes: H01L 2924/0103 : Zinc [Zn]
• CPC Class Codes: H01L 2924/01033 : Arsenic [As]
• CPC Class Codes: H01L 2924/01039 : Yttrium [Y]
• CPC Class Codes: H01L 2924/01049 : Indium [In]
• CPC Class Codes: H01L 2924/0105 : Tin [Sn]
• CPC Class Codes: H01L 2924/01057 : Lanthanum [La]
• 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

Techniques for interconnecting high-density, structures that include temperature sensitive materials such as piezoelectric ultrasonic transducer arrays, optical detector arrays, MEMS and the like to other structures (e.g., integrated circuits or mechanical assemblies) are disclosed.

Claims

1. A method for interconnecting a first structure to a second structure, the first structure including a photosensitive polymer layer, a mask layer, electrical contacts accessible via holes in the mask layer, and a temperature sensitive material that has an upper temperature limit, the method comprising:

etching the photosensitive polymer layer thereby opening a set of holes in the photosensitive polymer layer, each of these opened holes positioned over an electrical contact and wider than the corresponding hole in the mask layer;

depositing an electrically conductive material layer on at least the electrical contact and walls of each hole in the photosensitive polymer layer, the electrically conductive material having a melting point that is less than the temperature limit of the temperature sensitive material;

removing the photosensitive polymer layer and excess portions of the electrically conductive material thereby leaving remaining portions of the electrically conductive material, each remaining portion electrically and mechanically connected to an electrical contact; and

heating remaining electrically conductive material above its melting point thereby forming electrically conducting volumes over the electrical contacts, each electrically conducting volume formed from the remaining portions of the electrically conductive material connected to the corresponding electrical contact.

2. The method of claim 1 wherein each electrical contact has an under-bump metallurgy (UBM) layer deposited thereon, and the electrically conductive material layer is deposited on the UBM layer and walls of each hole in the photosensitive polymer layer.

3. The method of claim 1 wherein each of the remaining portions of the electrically conductive material is electrically and mechanically connected to a UBM layer associated with each electrical contact.

4. The method of claim 1 further comprising:

aligning the electrically conducting volumes of the first structure with electrical contacts of the second structure; and

forcibly pressing the aligned conducting volumes and electrical contacts together thereby forming a conjoined structure.

5. The method of claim 4 further comprising:

heating the conjoined structure to a temperature sufficient to reflow the aligned conducting volumes and electrical contacts to create electrically conducting columns between the first structure and the second structure.

6. The method of claim 5 wherein heating the conjoined structure is performed in a gaseous reducing atmosphere containing reactive atomic species.

7. The method of claim 1 wherein at least one of the first and second structures includes at least one of a piezoelectric device, an acoustical transducer, an ultrasonic transducer, an accelerometer, a geophone, an infrared detector, a micro-electromechanical system, a chemical detector, a gas detector, an organic molecule detector, a microprocessor, a field-programmable gate array, a plastic, and a glass.

8. The method of claim 1 further including the preliminary steps of:

applying the mask layer to a structure including the temperature sensitive material, wherein electrically conducting materials will not adhere to the mask layer;

applying an initial photosensitive polymer layer to the mask layer;

exposing the initial photosensitive polymer layer to light in a pattern, the pattern corresponding to locations of the electrical contacts;

developing and etching the initial photosensitive polymer layer thereby opening holes in the initial photosensitive polymer layer over the mask layer;

etching the mask layer thereby opening the holes in the mask layer; and

removing the initial photosensitive polymer layer.

9. The method of claim 1 wherein etching the photosensitive polymer layer thereby opening a set of holes in the photosensitive polymer layer includes the preliminary steps of:

applying the photosensitive polymer layer to the mask layer;

exposing the photosensitive polymer layer to light in a pattern, the pattern corresponding to locations the holes in the mask layer; and

developing and etching the photosensitive polymer layer thereby opening the set of holes in the photosensitive polymer layer.

10. The method of claim 1 wherein depositing the electrically conductive material layer on the electrical contact and walls of each hole in the photosensitive polymer layer is accomplished via deposition assisted by an inert gas jet.

11. The method of claim 1 wherein the remaining portions of the electrically conductive material that are electrically and mechanically connected to the electrical contacts each has a volume that is determined by thickness of the polymer layer and dimensions of the holes in the photosensitive polymer layer.

12. The method of claim 1 wherein the temperature sensitive material is associated with one of a piezoelectric material or an infrared detector.

13. The method of claim 12 wherein the piezoelectric device is an ultrasonic transducer.

14. The method of claim 13 wherein the ultrasonic transducer is a multi-element array.

15. The method of claim 1 wherein the electrically conductive material is an alloy.

16. The method of claim 1 wherein the second structure has electrically conducting volumes that were formed by a process that is substantially similar the process used in forming the electrically conducting volumes of structure 1, method further comprising:

aligning the electrically conducting volumes of the first structure with electrically conducting volumes of the second structure;

forcibly pressing the aligned electrically conducting volumes together thereby forming a conjoined structure; and

heating the conjoined structure to a temperature sufficient to reflow the aligned electrically conducting volumes to create electrically conducting columns between the first structure and the second structure.

17. The method of claim 1 wherein the remaining portions of the electrically conductive material form saucer-like shapes, wherein at least a portion of the saucer-like shape adheres to one of its corresponding electrical contact or a UBM layer on the corresponding electrical contact.

18. A method for interconnecting a first structure to a second structure, the first structure including a temperature sensitive material, a photosensitive polymer layer, a mask layer, and electrical contacts accessible via holes in the mask layer, where each electrical contact has an under-bump metallurgy (UBM) layer deposited thereon, the method comprising:

etching the photosensitive polymer layer thereby opening a set of holes in the photosensitive polymer layer, each of these opened holes over an electrical contact and wider than the corresponding hole in the mask layer;

depositing an electrically conductive material layer on at least the electrical contact UBM layer and walls of each hole in the photosensitive polymer layer, the electrically conductive material having a melting point that is less than a temperature limit of the temperature sensitive material;

removing the photosensitive polymer layer and excess portions of the electrically conductive material thereby leaving remaining portions of the electrically conductive material, each remaining portion forming a saucer-like shape, with at least a portion of the saucer-like shape electrically and mechanically connected to the corresponding electrical contact UBM layer; and

heating remaining electrically conductive material above its melting point thereby forming electrically conducting volumes over the electrical contacts, each electrically conducting volume formed from the remaining portions of the electrically conductive material connected to the corresponding electrical contact.

19. A method for interconnecting a first structure to a second structure, the first structure including a polymer layer, a temperature sensitive material that has a temperature limit, and electrical contacts accessible via holes, the method comprising:

depositing an electrically conductive material layer on at least the electrical contact and walls of each access hole, the electrically conductive material having a melting point that is less than the temperature limit of the temperature sensitive material;

removing the polymer layer and excess portions of the electrically conductive material thereby leaving remaining portions of the electrically conductive material, each remaining portion forming a saucer-like shape, with at least a portion of the saucer-like shape electrically and mechanically connected to its corresponding electrical contact; and

heating remaining electrically conductive material above its melting point thereby forming electrically conducting volumes over the electrical contacts, each electrically conducting volume formed from the remaining portions of the electrically conductive material connected to the corresponding electrical contact.

20. The method of claim 19 further comprising:

aligning the electrically conducting volumes of the first structure with electrical contacts of the second structure;

forcibly pressing the aligned electrically conducting volumes and electrical contacts together thereby forming a conjoined structure; and

heating the conjoined structure to a temperature sufficient to reflow the aligned electrically conducting volumes and electrical contacts to create electrically conducting columns between the first structure and the second structure.

21. A method for interconnecting a first structure to a second structure, the first structure having a number of layers including a temperature sensitive material layer that has a temperature limit, electrical contacts, a photosensitive polymer layer, a mask layer with access to the electrical contacts via holes in the mask layer, wherein each electrical contact has an under-bump metallurgy (UBM) layer deposited thereon, the method comprising:

etching the photosensitive polymer layer thereby opening a set of holes in the photosensitive polymer layer, each of these opened holes positioned over an electrical contact and having a width greater than the corresponding hole in the mask layer;

depositing an electrically conductive material layer on at least one of the electrical contact UBM regions and walls of each hole in the photosensitive polymer layer, the electrically conductive material having a melting point that is less than the temperature limit of the temperature sensitive material;

removing the photosensitive polymer layer and excess portions of the electrically conductive material thereby leaving remaining portions of the electrically conductive material, each remaining portion forming a saucer-like shape, with at least a portion of the saucer-like shape electrically and mechanically connected to the corresponding electrical contact UBM layer;

heating remaining electrically conductive material above its melting point thereby forming electrically conducting volumes over the electrical contacts, each electrically conducting volume formed from the remaining portions of the electrically conductive material connected to the corresponding electrical contact;

aligning at least one of the electrically conducting volumes of the first structure with a corresponding electrical contact of the second structure;

forcibly pressing the aligned structures together thereby forming a conjoined structure; and

heating the conjoined structure to a temperature sufficient to reflow the aligned electrically conducting volumes to create electrically conducting columns between the first structure and the second structure.

22. A method for interconnecting a first structure to a second structure, the first structure having at least one electrical contact and a temperature sensitive material that has a temperature limit, the first structure having been prepared by depositing a mask layer onto the temperature sensitive material, and depositing a first photosensitive polymer layer onto the mask layer, and exposing the first polymer layer to a pattern of light, and developing the first polymer layer to create at least one hole in the polymer layer such that the mask layer is exposed, and etching the mask layer to expose at least one electrical contact, and depositing an under-bump metallurgy on the electrical contact, and depositing one or more additional photosensitive polymer layers, and exposing the additional polymer layers to a pattern of light, and developing the additional polymer layers to create at least one hole in the polymer layer such that the under-bump metallurgy and a portion of the mask layer is exposed, and the second structure has active electronic circuits and at least one electrical contact, the method comprising:

depositing an electrically conductive material layer on at least one of the under-bump metallurgy contacts, the electrically conductive material having a melting point that is less than the temperature limit of the temperature sensitive material;

removing the polymer layer and excess portions of the electrically conductive material thereby leaving at least one remaining portion of the electrically conductive material, electrically and mechanically connected to its corresponding under-bump metallurgy;

heating remaining electrically conductive material above its melting point thereby forming electrically conducting volumes over the under-bump metallurgy, each electrically conducting volume formed from the remaining portions of the electrically conductive material and electrically and mechanically connected to the corresponding under-bump metallurgy;

forcibly contacting at least one electrically conducting volume of the first structure with at least one electrical contact of the second structure to form a conjoined assembly; and

heating the assembly above the melting point of the electrically conducting material in an atmosphere containing reactive atomic species such that an electrical and mechanical interconnection is achieved between the first and second structures.

23. The method of claim 22 wherein at least one of the electrical contacts of the second structure is an electrically conducting volume formed in a like-manner to the electrically conducting volumes of the first structure.