Light emitting diode optical emitter with transparent electrical connectors
View Patent ↗An optical emitter includes a Light-Emitting Diode (LED) on a package wafer, transparent insulators, and one or more transparent electrical connectors between the LED die and one or more contact pads on the packaging wafer. The transparent insulators are deposited on the package wafer with LED dies attached using a lithography or a screen printing method. The transparent electrical connectors are deposited using physical vapor deposition, chemical vapor deposition, spin coating, spray coating, or screen printing and may be patterned using a lithography process and etching.
1. A method of fabricating an optical emitter, comprising:
providing a package substrate that includes a die-attach area and a contact pad, the die-attach area being spaced apart from the contact pad;
attaching a light-emitting diode (LED) die to the die-attach area, the LED die containing a vertical LED;
forming a patterned transparent insulating layer over the package substrate and over the LED die and the contact pad, wherein at least a portion of the patterned transparent insulating layer separates the LED die and the contact pad, and wherein the transparent insulating layer includes a first opening exposing a portion of the LED die and a second opening exposing a portion of the contact pad; and
forming a transparent electrical conductor over the patterned transparent insulating layer such that the first opening and the second opening are each at least partially filled with the transparent electrical conductor, thereby electrically coupling the LED die with the contact pad.
2. The method of claim 1 , wherein the forming of the patterned transparent insulating layer comprises:
depositing a transparent insulating material over the package substrate and over the LED die and the contact pad; and
etching the transparent insulating material to form the first opening and the second opening.
3. The method of claim 1 , wherein the forming of the patterned transparent insulating layer is performed via a screen printing process.
4. The method of claim 1 , wherein the providing the package substrate comprises forming a first through-substrate via (TSV) and a second TSV, the first TSV being electrically coupled to the die-attach area, and the second TSV being electrically coupled to the contact pad.
5. The method of claim 1 , further comprising: roughening a surface of the patterned transparent insulating layer and a surface of the transparent electrical conductor.
6. A method of fabricating an optical emitter, comprising:
providing a package substrate that includes a die-attach area, a first contact pad, and a second contact pad, the die-attach area being spaced apart from the first and second contact pads;
attaching a light-emitting diode (LED) die to the die-attach area, the LED die containing a horizontal LED that includes an n-type doped layer, a p-type doped layer, and a light-emitting layer disposed between the n-type doped layer and the p-type doped layer;
forming a patterned transparent insulating layer over the package substrate, the LED die, and the first and second contact pads, wherein the patterned transparent insulating layer separates the LED die from the first and second contact pads, and wherein the transparent insulating layer includes first, second, third, and fourth openings, the first and second openings exposing the n-type doped layer and the p-type doped layer of the horizontal, respectively, the third and fourth openings exposing the first and second contact pads, respectively; and
forming a patterned transparent electrical conductor layer over the patterned transparent insulating layer such that the first and third openings are each at least partially filled with a first segment of the patterned transparent electrical conductor layer, thereby electrically coupling the n-type doped layer with the first contact pad, and the second and fourth openings are each at least partially filled with a second segment of the patterned transparent electrical conductor layer, thereby electrically coupling the p-type doped layer with the second contact pad, and wherein the first and second segments of the patterned transparent electrical conductor layer are formed to be electrically isolated from one another.
7. The method of claim 6 , wherein the forming of the patterned transparent insulating layer comprises:
depositing a transparent insulating material over the package substrate and over the LED die and the first and second contact pads; and
etching the transparent insulating material to form the first, second, third, and fourth openings.
8. The method of claim 6 , wherein the forming of the patterned transparent insulating layer or the forming of the patterned transparent electrical conductor layer comprises a screen printing process.
9. The method of claim 6 , wherein the providing the package substrate comprises forming a first through-substrate via (TSV) and a second TSV, the first TSV being electrically coupled to the first contact pad, and the second TSV being electrically coupled to the second contact pad.
10. The method of claim 6 , further comprising: roughening a surface of the patterned transparent insulating layer and a surface of the patterned transparent electrical conductor layer.
11. A method of fabricating a plurality of optical emitters, comprising:
providing a package wafer having a plurality of Light-Emitting Diode (LED) die attach areas and a plurality of contact pads, wherein each LED die attach area is associated with at least one contact pad;
attaching a plurality of LED dies to the package wafer at the plurality of LED die attach areas;
forming a transparent insulator between each of plurality of LED dies and the at least one contact pad associated with the LED die attach area; and,
forming a transparent electrical connector between each of plurality of LED dies and an associated contact pad.
12. The method of claim 11 , wherein the forming a transparent insulator comprises:
depositing a transparent insulator layer,
patterning the transparent insulator layer, and
etching the transparent insulator layer to create an opening over the LED die and the at least one contact pad.
13. The method of claim 11 , wherein the forming a transparent insulator comprises screen printing a patterned transparent insulator.
14. The method of claim 11 , wherein the forming a transparent electrical connector comprises:
depositing a transparent conductive layer,
patterning a photoresist over the transparent conductive layer, and
etching the transparent conductive layer through the pattern down to the transparent insulator layer.
15. The method of claim 14 , wherein the depositing a transparent conductive layer comprises depositing using physical vapor deposition, depositing using chemical vapor deposition, spin coating, or spray coating.
16. The method of claim 14 , wherein the etching is wet etching.
17. The method of claim 11 , wherein the forming a transparent electrical connector comprises screen printing a transparent electrical connector.
18. The method of claim 11 , wherein the at least one contact pad is two contact pads and further comprising forming another transparent electrical connector electrically connecting each of the plurality of LED dies and a second associated contact pad.
19. The method of claim 11 , further comprising dicing the package wafer into a plurality of optical emitters.
20. The method of claim 11 , further comprising roughing a top surface of the transparent insulator layer and the transparent electrical connector.