Semiconductor structure having thermal backside core
View Patent ↗A semiconductor structure includes a semiconductor substrate having a recess disposed beneath a semiconductor device. The semiconductor structure also includes a thermally conductive core disposed in the recess, and a package substrate including a heat sink. The heat sink is in thermal contact with the thermally conductive core.
1. A semiconductor structure, comprising:
a semiconductor substrate comprising a first side and a second side;
a recess in the semiconductor substrate, the recess being disposed beneath a semiconductor device, wherein the semiconductor substrate having a first thickness between the semiconductor device and the recess that is less than a second thickness in all other locations between the first side and the second side; and
a thermally conductive core disposed in the recess, wherein a thermal resistance between the first side and the second side in the other locations between the first side and the second side is substantially less than a thermal resistance through the first thickness and a lower side of the thermally conductive core.
2. A semiconductor structure as claimed in claim 1 , further comprising a package substrate comprising a heat sink, wherein the heat sink is in thermal contact with the thermally conductive core.
3. A semiconductor structure as claimed in claim 1 , wherein the first thickness is substantially less than the second thickness.
4. A semiconductor structure as claimed in claim 1 , wherein the thermally conductive core is attached to an upper surface of the recess on one side, and to an upper surface of the heat sink on a second side.
5. A semiconductor structure as claimed in claim 1 , further comprising a backside ground plane disposed over a surface of the recess, wherein the thermally conductive core is attached directly to the backside ground plane.
6. A semiconductor structure as claimed in claim 5 , further comprising a die attach material disposed between a lower surface of the semiconductor substrate and an upper surface of the package substrate.
7. A semiconductor structure as claimed in claim 6 , wherein the die attach material is disposed between a lower surface of the thermally conductive core and the heat sink.
8. A semiconductor structure as claimed in claim 5 , further comprising a die attach material disposed on at least one side of the recess.
9. A semiconductor structure as claimed in claim 1 , wherein the thermally conductive core is attached directly to the heat sink.
10. A semiconductor structure as claimed in claim 9 , further comprising a die attach material disposed between a lower surface of the semiconductor substrate and an upper surface of the package substrate.
11. A semiconductor structure as claimed in claim 9 , further comprising a die attach material disposed on at least one side of the recess.
12. A semiconductor structure as claimed in claim 9 , further comprising a die attach material disposed between an upper surface of the thermally conductive core and an upper surface of the recess.
13. A semiconductor structure as claimed in claim 1 , wherein the semiconductor device comprises a power amplifier comprising the semiconductor die, the semiconductor die comprising one or more of gallium arsenide (GaAs), indium phosphide (InP), aluminum arsenide (AlAs), or alloys of GaAs, InP, AlAs.
14. A semiconductor structure as claimed in claim 13 , wherein at least one of the semiconductor die comprises an active semiconductor device.
15. A semiconductor structure as claimed in claim 14 , wherein the active device comprises one or more of a metal-semiconductor field effect transistor (MESFET), a high electron mobility transistor (HEMT), a pseudomorphic HEMT, a junction gate field effect transistor (JFET), and a heterojunction bipolar transistor (HBT).
16. A semiconductor structure as claimed in claim 1 , wherein the semiconductor substrate is electrically insulating.
17. A semiconductor structure as claimed in claim 1 , wherein the semiconductor substrate comprises a material having a comparatively large thermal resistivity.
18. A semiconductor structure as claimed in claim 1 , wherein the recess has a width in the range of approximately 100 μm to approximately 300 μm.
19. A semiconductor structure as claimed in claim 1 , wherein the recess has a width in the range of approximately 100 μm to approximately 1000 μm.
20. A semiconductor structure as claimed in claim 1 , wherein the recess has a width in the range of approximately 100 μm to approximately 300 μm.
21. A semiconductor structure as claimed in claim 1 , wherein the semiconductor substrate has a thickness, and the recess has a depth of approximately 30% to approximately 90% of the thickness of semiconductor substrate.
22. A semiconductor structure as claimed in claim 1 , wherein a portion of the semiconductor substrate in a region between the recess and an upper surface of the semiconductor substrate has a thickness of approximately 70% to approximately 10% of a thickness of the semiconductor substrate.
23. A semiconductor structure as claimed in claim 22 , wherein the thickness of the portion is approximately 20 μm to approximately 20 μm.
24. A semiconductor structure as claimed in claim 22 , wherein the thickness of the portion is approximately 30 μm to approximately 100 μm.