Air-gap C4 fluidic I/O interconnects and methods of fabricating same

1. A chip for use in fabricating a three-dimensional integrated circuit, the chip comprising:

a wafer comprising a first surface and a second surface;

one or more hollow, fluidic vias extending through the wafer between the first surface and the second surface; and

one or more fluidic interconnects;

wherein each fluidic via is in fluid communication with a fluidic interconnect, and

wherein a fluidic interconnect comprises a first end proximate the first surface of the wafer, a second end, and a cap proximate the second end, the cap defining an air-filled space within the fluidic interconnect wherein the cap comprises solder.

2. The chip of claim 1 further comprising:

one or more metallic-filled, electrical vias extending through the wafer between the first surface and the second surface; and

one or more electrical interconnects;

wherein each electrical via is in electrical communication with an electrical interconnect proximate the first surface.

3. A method of fabricating the chip of claim 1 , the method comprising:

providing the wafer comprising one or more fluidic vias;

sputtering a seed layer on the first surface of the wafer;

patterning an electroplating mold into the seed layer, the electroplating mold comprising an aperture for each of the one or more fluidic vias; and

electroplating solder into the apertures of the electroplating mold.

4. The method of claim 2 further comprising removing the electroplating mold.

5. The method of claim 2 further comprising reflowing solder.

6. The method of claim 2 , wherein electroplating solder comprises depositing solder to a height greater than a height of the electroplating mold.

7. The method of claim 5 , wherein reflowing solder forms caps, the caps defining air-filled spaces within fluid interconnects.

8. A method of fabricating a three-dimensional integrated circuit from chips, the method comprising:

providing a first chip comprising the chip of claim 1 ;

providing a second chip comprising the chip of claim 1 , wherein the one or more fluidic vias of the second chip comprise a binding element proximate the second surface of the wafer of the second chip, the binding element comprising a solder wettable material;

aligning the first chip and second chip, such that the one or more fluidic interconnects of the first chip are positioned proximate corresponding binding elements of the second chip; and

wetting the binding elements to bind the first chip to the second chip;

wherein wetting removes at least a portion of the cap of each fluidic interconnect of the first chip, such that the fluidic interconnects of the first chip provide fluid communication between the one or more fluidic vias of the first chip and corresponding fluidic vias of the second chip.

9. The of the claim 8 , wherein the solder wettable material comprises copper.

10. The method of claim 8 , wherein at least one of the binding elements is ring-shaped.

11. A method of fabricating a three-dimensional integrated circuit, the method comprising:

fabricating a first chip comprising:

providing a wafer comprising one or more electrical vias and one or more fluidic vias;

sputtering a seed layer on a first surface of the wafer;

patterning an electroplating mold into the seed layer, the electroplating mold comprising an aperture for each of the one or more fluidic vias and an aperture for each of the one or more electrical vias; and

simultaneously electroplating solder into each aperture of the electroplating mold to form an air-filled, fluidic interconnect proximate each of the one or more fluidic vias and an electrical interconnect proximate each of the one or more electrical vias, the air-filled fluidic interconnects comprising caps defining an air-filled space within the fluidic interconnects.

12. The method of claim 11 further comprising:

fabricating a second chip; and

aligning the first chip with the second chip.

13. The method of claim 11 further comprising removing the electroplating mold.

14. The method of claim 11 further comprising reflowing solder.

15. The method of claim 11 , wherein simultaneously electroplating solder comprises depositing solder to a height greater than a height of the electroplating mold.

16. The method of claim 11 further comprising merging solder at a top of the apertures corresponding to the one or fluidic vias to form a cap.

17. The method of claim 12 , wherein the second chip comprises:

a second wafer comprising a first surface and a second surface;

one or more metallic-filled, electrical vias extending through the second wafer between the first surface and second surface;

one or more hollow, fluidic vias extending through the second wafer between the first surface and the second surface; and

a plurality of binding elements corresponding to and positioned adjacent each of the electrical and fluidic vias proximate the first surface of the second wafer.

18. The method of claim 17 further comprising:

aligning the first chip and the second chip such that the fluidic interconnects of the first chip and the electrical interconnects of the first chip are positioned proximate corresponding binding elements of the second chip; and

wetting the binding elements to bind the first chip to the second chip;

wherein wetting removes at least a portion of the cap of each fluidic interconnect of the first chip, such that the fluidic interconnects of the first chip provide fluid communication between the one or more fluidic vias of the first chip and corresponding fluidic vias of the second chip; and

wherein wetting causes the electrical interconnects of the first chip to provide electrical communication between the one or more electrical vias of the first chip and corresponding electrical vias of the second chip.

19. The method of the claim 18 , wherein the solder wettable material comprises copper.

20. The method of claim 18 , wherein at least one of the binding elements is ring-shaped.