Methods and apparatus for backside integrated circuit high frequency signal radiation, reception and interconnects

1. An apparatus, comprising:

a semiconductor substrate having: a front side surface; including circuitry in a first level; and a backside surface opposite the front side surface;

a metal conductor stack formed in a second level that is overlying the first level, wherein the second level includes multiple sublevels thereof;

at least one cavity opening etched in the backside surface and extending into the semiconductor substrate, wherein at least the second level is overlying the cavity opening;

a structure, formed in a portion of the metal conductor stack, to radiate signals through the cavity opening in the backside surface, wherein the structure is formed in at least one of the sublevels of the second level that is overlying the first level; and

a reflective surface, overlying and adjacent the second level, and spaced from the structure by at least one of the sublevels of the second level, and configured to reflect the radiated signals towards the cavity opening in the backside surface.

2. The apparatus of claim 1 , wherein the reflective surface is an electrical reflector.

3. The apparatus of claim 2 , wherein the reflective surface is configured to reflect the radiated signals with a phase shift of 180 degrees.

4. The apparatus of claim 2 , wherein the reflective surface is spaced from the structure by a distance that is a fraction of the wavelength of the radiated signals between 1/100 and ½ of the wavelength.

5. The apparatus of claim 1 , wherein the reflective surface is a magnetic reflector.

6. The apparatus of claim 5 , wherein the reflective surface is configured to reflect the radiated signals with a phase shift of 0 degrees.

7. The apparatus of claim 1 wherein the radiated signals have a frequency between 0.1 THz and 30 THz.

8. The apparatus of claim 1 , wherein the cavity opening has sloped sidewalls.

9. The apparatus of claim 1 , wherein the cavity opening forms a waveguide for the radiated signals.

10. The apparatus of claim 1 , wherein the cavity opening has vertical sidewalls.

11. The apparatus of claim 1 , wherein the cavity opening has a conductive material coating.

12. The apparatus of claim 11 , wherein the conductive material coating does not extend onto the backside surface beyond the cavity opening.

13. The apparatus of claim 1 wherein the structure forms an antenna.

14. The apparatus of claim 1 , wherein the structure is a radiating structure.

15. The apparatus of claim 1 , wherein the structure is a coupling structure.

16. The apparatus of claim 1 , wherein the cavity opening has stepped sidewalls.

17. The apparatus of claim 1 , wherein at least the first and second levels are overlying the cavity opening.

18. A method, comprising:

forming a metal conductor stack in a first level that is overlying a front side surface of a semiconductor substrate, wherein the first level includes multiple sublevels thereof, and wherein the front side surface includes circuitry in a second level that is underlying the first level;

forming a backside cavity opening in a backside surface of the semiconductor substrate and extending into the semiconductor substrate, wherein at least the first level is overlying the cavity opening, and wherein the backside surface of the semiconductor substrate is opposite the front side surface of the semiconductor substrate;

in a portion of the metal conductor stack, forming a structure to radiate signals through the backside cavity opening, wherein the structure is formed in at least one of the sublevels of the first level that is overlying the second level; and

forming a reflective surface, overlying and adjacent the first level, and spaced from the structure by at least one of the sublevels of the first level, and configured to reflect the radiated signals towards the cavity opening in the backside surface.

19. The method of claim 18 , wherein the structure is a radiating structure.

20. The method of claim 18 , wherein the structure is a coupling structure.

21. The method of claim 18 , wherein the reflective surface is an electrical reflector.

22. The method of claim 21 , wherein the reflective surface is configured to reflect the radiated signals with a phase shift of 180 degrees.

23. The method of claim 21 , wherein the reflective surface is spaced from the structure by a distance that is a fraction of the wavelength of the radiated signals between 1/100 and ½ of the wavelength.

24. The method of claim 18 , wherein the reflective surface is a magnetic reflector.

25. The method of claim 24 , wherein the reflective surface is configured to reflect the radiated signals with a phase shift of 0 degrees.

26. The method of claim 18 wherein the radiated signals have a frequency between 0.1 THz and 30 THz.

27. The method of claim 18 , wherein the backside cavity opening has sloped sidewalls.

28. The method of claim 18 , wherein the backside cavity opening forms a waveguide for the radiated signals.

29. The method of claim 18 , wherein the backside cavity opening has vertical sidewalls.

30. The method of claim 18 , wherein the backside cavity opening has stepped sidewalls.

31. The method of claim 18 , wherein the backside cavity opening has a conductive material coating.

32. The method of claim 31 , wherein the conductive material coating does not extend onto the backside surface beyond the backside cavity opening.

33. The method of claim 18 wherein the structure forms an antenna.

34. The method of claim 18 , wherein at least the first and second levels are overlying the backside cavity opening.

35. The method of claim 18 , wherein forming the backside cavity opening further comprises:

backgrinding the semiconductor substrate to thin the semiconductor substrate to a predetermined thickness.

36. The method of claim 18 , wherein forming the backside cavity opening further comprises performing a wet etch to form an opening with sloped sidewalls.

37. The method of claim 18 , wherein forming the backside cavity opening further comprises performing an etch that is one selected from the group consisting essentially of a KOH wet etch, a TMAH etch, and a deep reactive ion etch.

38. A system, comprising:

a first integrated circuit including: a first antenna for radiating THz frequency signals, formed in a first metal conductor stack in a first level that is overlying a front side surface of a first semiconductor substrate, wherein the first level includes multiple sublevels thereof, and wherein the first antenna is formed in at least one of the sublevels of the first level; a first opening formed in a backside of the first semiconductor substrate and extending into the first semiconductor substrate at a location corresponding to the first antenna, wherein the first level is overlying the first opening; and a first reflective surface, overlying and adjacent the first level, and spaced from the first antenna by at least one of the sublevels of the first level, and configured to reflect the radiated THz frequency signals towards the first opening in the backside of the first semiconductor substrate; and

a second integrated circuit including: a second antenna for receiving the THz frequency signals, formed in a second metal conductor stack in a second level that is overlying a front side surface of a second semiconductor substrate, wherein the second level includes multiple sublevels thereof, and wherein the second antenna is formed in at least one of the sublevels of the second level; and a second opening formed in a backside of the second semiconductor substrate and extending into the second semiconductor substrate at a location corresponding to the second antenna, wherein the second level is overlying the second opening;

the first and second openings facing one another and being aligned to one another to facilitate transmission of the THz frequency signals from the first integrated circuit to the second integrated circuit.