Light emitting device
View Patent ↗The present disclosure relates to methods for performing wafer-level measurement and wafer-level binning of LED devices. The present disclosure also relates to methods for reducing thermal resistance of LED devices. The methods include growing epitaxial layers consisting of an n-doped layer, an active layer, and a p-doped layer on a wafer of a growth substrate. The method further includes forming p-contact and n-contact to the p-doped layer and the n-doped layer, respectively. The method further includes performing a wafer-level measurement of the LED by supplying power to the LED through the n-contact and the p-contact. The method further includes dicing the wafer to generate diced LED dies, bonding the diced LED dies to a chip substrate, and removing the growth substrate from the diced LED dies.
1. A method of fabricating a light emitting diode (LED) comprising:
growing epitaxial layers comprising an n-doped layer, an active layer, and a p-doped layer on a wafer of a growth substrate;
forming a p-contact to the p-doped layer;
performing a wafer-level measurement of the LED by supplying power to the LED through the n-doped layer and the p-doped layer;
dicing the wafer to yield a diced LED die;
bonding the diced LED die to a substrate, wherein the substrate comprises interconnects formed within the substrate; and
after the bonding, forming an n-contact to the n-doped layer.
2. The method of claim 1 , further comprising growing a reflective mirror layer on the p-contact.
3. The method of claim 1 , further comprising forming a dielectric layer on sidewalls of the diced LED die.
4. The method of claim 1 , wherein said forming the p-contact comprises:
growing a p-contact metal layer to electrically connect to the p-doped layer; and
patterning the p-contact metal layer.
5. The method of claim 1 , wherein said forming the n-contact comprises etching the epitaxial layers down to the n-doped layer and depositing a metal to electrically connect to the n-doped layer.
6. The method of claim 1 , wherein said performing the wafer-level measurement comprises measuring emitted light from the active layer with a detector disposed on a backside of the growth substrate.
7. The method of claim 1 , wherein said performing the wafer-level measurement comprises measuring emitted light from the active layer with a detector disposed on a topside of the growth substrate.
8. The method of claim 7 , wherein said performing the wafer-level measurement further comprises patterning the p-contact to a metal mesh and measuring the emitted light through the metal mesh.
9. The method of claim 7 , wherein the p-contact comprises a semi-transparent or transparent material and said performing the wafer-level measurement comprises measuring the emitted light through the p-contact.
10. The method of claim 1 , wherein said bonding the diced LED die comprises flipping the diced LED die and bonding the diced LED die to the substrate using a bonding metal layer.
11. The method of claim 1 , wherein the substrate comprises a silicon substrate with higher thermal conductivity than the growth substrate.
12. The method of claim 1 , wherein the substrate has supporting circuitries for the diced LED die.
13. The method of claim 1 , further comprising removing the growth substrate from the diced LED die.
14. The method of claim 13 , wherein said removing the growth substrate comprises etching the diced LED die to expose the n-doped layer.
15. The method of claim 14 , further comprising roughening the n-doped layer to increase light extraction from the diced LED die.
16. A method of binning light emitting diodes (LED) comprising:
providing a plurality of LED dies on a first wafer, each of the plurality of LED dies comprising a p-type layer and an n-type layer;
supplying test power to each of the plurality of LED dies through the p-type layer and the n-type layer;
measuring a light emitted for each of the plurality of LED dies for wafer-level binning of each of the plurality of LED dies;
slicing the first wafer to separate the plurality of LED dies;
bonding, in response to the wafer-level binning, a selected subset of the LED dies to a second wafer with better thermal dissipation properties than the first wafer;
removing remaining portions of the first wafer from each of the LED dies bonded to the second wafer, thereby exposing a surface of the n-type layer; and
forming an electrode contact on the exposed surface of the n-type layer.
17. The method of claim 16 , wherein measuring the light comprises disposing a detector on a topside of the first wafer.
18. The method of claim 16 , wherein measuring the light comprises disposing a detector on a backside of the first wafer.
19. A light emitting diode (LED) die comprising:
epitaxial layers of semiconductor materials comprising an n-doped layer, an active layer, and a p-doped layer;
a plurality of regions of a dielectric material disposed on top of the epitaxial layers and along sidewalls of the LED die;
a reflective mirror layer disposed underneath the p-doped layer;
a substrate, wherein the substrate comprises interconnects formed within the substrate to provide electrical connections to the LED die;
a bonding metal layer disposed between the reflective mirror layer and the substrate to bond the LED die to the substrate;
a p-contact layer disposed between the reflective mirror layer and the p-doped layer; and
an n-contact layer disposed over the n-doped layer, wherein the n-doped layer, the active layer, and the p-doped layer are all located between the n-contact layer and the p-contact layer.
20. The LED die of claim 19 , wherein the p-contact layer and the n-contact layer are disposed to provide electrical connections to the p-doped layer and the n-doped layer, respectively.