Low warpage wafer bonding through use of slotted substrates
View Patent ↗In a wafer bonding process, one or both of two wafer substrates are scored prior to bonding. By creating slots in the substrate, the wafer's characteristics during bonding are similar to that of a thinner wafer, thereby reducing potential warpage due to differences in CTE characteristics associated with each of the wafers. Preferably, the slots are created consistent with the singulation/dicing pattern, so that the slots will not be present in the singulated packages, thereby retaining the structural characteristics of the full-thickness substrates.
1. A structure comprising:
a first semiconductor wafer comprising a plurality of semiconductor devices, wherein the first semiconductor wafer comprises an insulating growth substrate, wherein the plurality of semiconductor devices each comprise a semiconductor structure disposed on the insulating growth substrate, and
a second wafer that is bonded to the first wafer via bonding surfaces on the first and second wafers,
wherein, to reduce warpage of the structure, the second wafer is scored with a plurality of slots on a surface that is opposite to the bonding surface.
2. The structure of claim 1 , wherein the semiconductor devices include light emitting devices.
3. The structure of claim 1 , wherein the slots are aligned with boundaries between the semiconductor devices.
4. The structure of claim 1 , wherein the second wafer has a thickness T, and the slots have a depth D that is between forty and eighty percent of the thickness T.
5. The structure of claim 1 , wherein the semiconductor devices have a device width, and the slots have a slot width that is between five and twenty percent of the device width.
6. The structure of claim 1 , wherein the second wafer comprises a plurality of through-holes that extend through an entire thickness of the second wafer.
7. The structure of claim 6 , wherein:
the through-holes are aligned with contact areas on the plurality of semiconductor devices; and
conductors are disposed in the through-holes.
8. The structure of claim 1 , wherein neighboring slots are disposed an integer number of semiconductor devices apart.
9. The device of claim 1 wherein:
the bonding surface on the first semiconductor wafer comprises a surface of the plurality of semiconductor devices.
10. A method comprising:
growing a semiconductor structure on a growth substrate, wherein the growth substrate is insulating;
creating a plurality of semiconductor devices on the growth substrate, the growth substrate and the plurality of semiconductor devices forming a first wafer, and
bonding the first wafer to a second wafer that includes a submount substrate via bonding surfaces of the first and second wafers,
to reduce warpage of the structure, the submount substrate is scored with a plurality of slots on a surface that is opposite to the bonding surface of the wafer.
11. The method of claim 10 , wherein the plurality of slots are aligned with boundaries between the semiconductor devices.
12. The method of claim 10 , wherein the semiconductor devices include light emitting devices.
13. The method of claim 10 , wherein the submount substrate has a thickness T, and the slots have a depth D that is between forty and eighty percent of the thickness T.
14. The method of claim 10 , wherein the semiconductor devices have a device width, and the slots have a slot width that is between five and twenty percent of the device width.
15. The method of claim 10 , wherein the growth substrate includes sapphire, and the submount substrate includes silicon.
16. The method of claim 10 , wherein the second wafer comprises a plurality of through-holes that extend through an entire thickness of the submount substrate.
17. The method of claim 16 , wherein:
the through-holes are aligned with contact areas on the plurality of semiconductor devices; and
conductors are disposed in the through-holes.
18. The method of claim 10 , wherein neighboring slots are disposed an integer number of semiconductor devices apart.
19. The method of claim 10 wherein the bonding surface of the first wafer comprises a surface of the plurality of semiconductor devices, the method further comprising after said bonding the first wafer to a second wafer, removing the growth substrate from the plurality of semiconductor devices.