Nickel tin bonding system with barrier layer for semiconductor wafers and devices
View Patent ↗A light emitting diode structure is disclosed that includes a light emitting active portion formed of epitaxial layers and carrier substrate supporting the active portion. A bonding metal system that predominates in nickel and tin joins the active portion to the carrier substrate. At least one titanium adhesion layer is between the active portion and the carrier substrate and a platinum barrier layer is between the nickel-tin bonding system and the titanium adhesion layer. The platinum layer has a thickness sufficient to substantially prevent tin in the nickel tin bonding system from migrating into or through the titanium adhesion layer.
1. A light emitting diode comprising:
a light emitting active portion formed of at least two Group III based epitaxial layers;
a bonding metal structure that predominates in nickel and tin on said active portion; and
a platinum barrier layer between said active portion and said bonding metal structure for substantially preventing tin in said bonding metal structure from migrating through said barrier layer,
wherein said bonding metal structure includes gold in an amount greater than 0.3 percent and less than 36 percent by weight of said bonding metal structure.
2. A light emitting diode according to claim 1 wherein said Group III based nitride epitaxial layers comprise gallium nitride.
3. A light emitting diode according to claim 1 wherein the thickness of said tin layer is between about five and 10 times the thickness of either of said nickel layers.
4. A light emitting diode according to claim 1 , comprising a titanium adhesion layer between said barrier layer and said active portion.
5. A light emitting diode according to claim 1 further comprising a carrier substrate that is configured to support the active portion, wherein the carrier substrate is selected from the group consisting of aluminum, copper, silicon and silicon carbide.
6. A light emitting diode according to claim 5 further comprising a second titanium layer between the carrier substrate and said bonding metal structure.
7. A light emitting diode according to claim 6 further comprising a second platinum layer between said second titanium layer and said bonding metal structure.
8. A light emitting diode according to claim 1 wherein said bonding metal structure is less than 6 microns thick.
9. A light emitting diode according to claim 1 wherein said bonding metal structure is less than 3 microns thick.
10. A light emitting diode comprising:
a carrier structure comprising a first platinum barrier layer and a nickel layer on said first platinum barrier layer;
a growth structure comprising a growth substrate, light emitting epitaxial layers on said growth substrate, and a metal bonding system on said epitaxial layers for joining to the carrier structure;
said metal bonding system predominating in nickel and tin joining said epitaxial layers to said carrier structure with a second platinum barrier layer between said epitaxial layers and said nickel layer; and
wherein the metal bonding system is configured so that when said metal bonding system on said growth structure and said nickel layer on said carrier structure are joined and heated, said respective platinum barrier layers substantially prevent tin from migrating through either of said first or second platinum barrier layers;
wherein said metal bonding system includes gold in an amount greater than 0.3 percent and less than 36 percent by weight of said bonding metal system.
11. A light emitting diode according to claim 10 wherein said growth substrate is selected from the group consisting of silicon carbide and sapphire, said epitaxial layers comprise Group III nitrides, and said carrier substrate is selected from the group consisting of silicon and silicon carbide.
12. A light emitting diode according to claim 11 wherein said epitaxial layers comprise gallium nitride and said carrier substrate comprises silicon.
13. A light emitting diode according to claim 10 further comprising:
a flash layer of gold on the nickel-tin portion of said metal bonding system; and
a flash layer of gold on said nickel layer on said carrier structure for joining said growth structure and said carrier structure at said respective gold flash layers.
14. A light emitting diode according to claim 10 wherein the thickness of said tin layer in said growth structure is between about five and 10 times the thickness of said nickel layer in said growth structure.
15. A light emitting diode according to claim 10 , wherein said metal bonding system comprises a titanium adhesion layer, and wherein said carrier structure comprises a second titanium adhesion layer.