Localized annealing of metal-silicon carbide ohmic contacts and devices so formed
View Patent ↗A method of forming an ohmic contact for a semiconductor device can be provided by thinning a substrate to provide a reduced thickness substrate and providing a metal on the reduced thickness substrate. Laser annealing can be performed at a location of the metal and the reduced thickness substrate at an energy level to form a metal-substrate material to provide the ohmic contact thereat.
1. A method of forming an ohmic contact for a semiconductor device, comprising:
thinning a substrate to provide a reduced thickness substrate;
providing a metal on the reduced thickness substrate; and
laser annealing a location of the metal and the reduced thickness substrate at an energy level to form a metal-substrate material to provide the ohmic contact thereat to form the ohmic contact having a specific contact resistivity of less than about 10 e −03 ohm-cm 2 .
2. A method according to claim 1 wherein the metal-substrate material comprises a metal-Silicon Carbide (SiC) material.
3. A method according to claim 1 wherein the location comprises a first interface location of the metal and the reduced thickness substrate, wherein laser annealing comprises:
laser annealing according to a pattern to avoid laser annealing a second location of the metal and the reduced thickness substrate to avoid forming the metal-substrate material at the second location.
4. A method according to claim 3 , further comprising:
removing the metal from the second location so that the ohmic contact remains on the reduced thickness substrate.
5. A method according to claim 1 , wherein the location comprises a first interface location of the metal and the reduced thickness substrate, wherein laser annealing comprises:
impinging laser light through an opening in a mask onto the metal at the first interface location and blocking the laser light with the mask opposite a second interface location of the metal and the reduced thickness substrate to avoid laser annealing the second interface location.
6. A method according to claim 5 , further comprising:
removing the metal from the second interface location so that the ohmic contact remains on the reduced thickness substrate.
7. A method according to claim 1 wherein providing a metal on the reduced thickness substrate comprises forming a pattern from the metal on the reduced thickness substrate to provide a metal pattern including portions of the metal pattern where the metal is absent, wherein laser annealing comprises:
laser annealing the metal pattern and the reduced thickness substrate to forming the metal-substrate material.
8. A method according to claim 1 further comprising:
forming a photoresist on the reduced thickness substrate according to a pattern to expose first portions of the reduced thickness substrate and to cover second portions of the reduced thickness substrate;
wherein providing a metal on the reduced thickness substrate comprises forming a blanket metal on the first portions and on the photoresist;
wherein laser annealing comprises impinging laser light on locations of the blanket metal and the reduced thickness substrate corresponding to the first portions to form a metal-substrate material thereat and avoiding impinging laser light on the blanket metal corresponding to the second portions to avoid forming the metal-substrate material thereat.
9. A method according to claim 8 further comprising:
removing the blanket metal from the photoresist so that metal-substrate material remains;
forming an overlay on the metal-substrate material; and
removing the photoresist from the second portions.
10. A method according to claim 8 further comprising:
forming an overlay on the metal-substrate material and on the photoresist; and
removing the photoresist from the second portions.
11. A method according to claim 8 further comprising:
lifting-off the photoresist and the blanket metal thereon leaving the metal-substrate material; and
forming an overlay on the metal-substrate material.
12. A method according to claim 1 further comprising:
dicing the reduced thickness substrate to provide a separate semiconductor device having the ohmic contact thereon.
13. A method according to claim 1 wherein laser annealing comprises laser annealing at the energy level above a bandgap of the reduced thickness substrate.
14. A method according to claim 1 wherein laser annealing comprises laser annealing at the energy level above a bandgap of the reduced thickness substrate to form the ohmic contact having a specific contact resistivity of less than about 10 e −04 ohm-cm 2 .
15. A method according to claim 1 wherein the semiconductor device includes a side wall comprising an oblique portion and a vertical portion.
16. A method according to claim 15 wherein the oblique portion defines about a 30 degree angle relative to the vertical portion.
17. A method according to claim 15 wherein the oblique portion comprises a thickness of about 150 microns and the vertical portion comprises a thickness of about 25 microns.
18. A method according to claim 1 wherein the semiconductor device includes a beveled upper side wall portion and a vertical lower side wall portion.
19. A method according to claim 1 wherein the reduced thickness substrate comprises a thickness of less than about 250 microns.
20. A method according to claim 1 wherein the reduced thickness substrate comprises a thickness of less than about 175 microns.
21. A method of forming an ohmic contact for a semiconductor device, comprising:
providing a metal on a reduced thickness layer, the reduced thickness layer comprising a first material, wherein the reduced thickness layer has a thickness of less than about 250 microns; and
laser annealing a location of the metal and the reduced thickness layer at an energy level above a bandgap of the reduced thickness layer to form a metal-first material material to provide the ohmic contact thereat.
22. A method according to claim 21 wherein the metal-first material material comprises a metal-Silicon Carbide (SiC) material.
23. A method according to claim 21 wherein the location comprises a first interface location of the metal and the reduced thickness layer, wherein laser annealing comprises:
laser annealing according to a pattern to avoid laser annealing a second location of the metal and the reduced thickness layer to avoid forming the metal-first material material at the second location.
24. A method according to claim 23 , further comprising:
removing the metal from the second location so that the ohmic contact remains on the reduced thickness layer.
25. A method according to claim 21 , wherein the location comprises a first interface location of the metal and the reduced thickness layer, wherein laser annealing comprises:
impinging laser light through an opening in a mask onto the metal at the first interface location and blocking the laser light with the mask opposite a second interface location of the metal and the reduced thickness layer to avoid laser annealing the second interface location.
26. A method according to claim 25 , further comprising:
removing the metal from the second interface location so that the ohmic contact remains on the reduced thickness layer.
27. A method according to claim 21 wherein providing a metal on the reduced thickness layer comprises forming a pattern from the metal on the reduced thickness layer to provide a metal pattern including portions of the metal pattern where the metal is absent, wherein laser annealing comprises:
laser annealing the metal pattern and the reduced thickness layer to forming the metal-first material material.
28. A method according to claim 21 further comprising:
forming a photoresist on the reduced thickness layer according to a pattern to expose first portions of the reduced thickness layer and to cover second portions of the reduced thickness layer;
wherein providing a metal on the reduced thickness layer comprises forming a blanket metal on the first portions and on the photoresist;
wherein laser annealing comprises impinging laser light on locations of the blanket metal and the reduced thickness layer corresponding to the first portions to form a metal-first material material thereat and avoiding impinging laser light on the blanket metal corresponding to the second portions to avoid forming the metal-first material material thereat.
29. A method according to claim 28 further comprising:
removing the blanket metal from the photoresist so that metal-first material material remains;
forming an overlay on the metal-first material material; and
removing the photoresist from the second portions.
30. A method according to claim 28 further comprising:
forming an overlay on the metal-first material material and on the photoresist; and
removing the photoresist from the second portions.
31. A method according to claim 28 further comprising:
lifting-off the photoresist and the blanket metal thereon leaving the metal-first material material; and
forming an overlay on the metal-first material material.
32. A method according to claim 21 further comprising:
dicing the reduced thickness layer to provide a separate semiconductor device having the ohmic contact thereon.
33. A method according to claim 21 wherein laser annealing comprises laser annealing to form the ohmic contact having a specific contact resistivity of less than about 10 e −03 ohm-cm 2 .
34. A method according to claim 31 wherein laser annealing comprises laser annealing to form the ohmic contact having a specific contact resistivity of less than about 10 e −04 ohm-cm 2 .
35. A method according to claim 21 wherein the semiconductor device includes a side wall comprising an oblique portion and a vertical portion.
36. A method according to claim 21 wherein the semiconductor device comprises a light emitting device.