Self-alignment process for micro light emitting diode using back-side exposure
Embodiments relate to a micro light-emitting-diode (μLED) fabricated using a self-aligned process. To fabricate the μLED, a metal layer is deposited on a p-type semiconductor. The p-type semiconductor is on an n-type semiconductor and the n-type semiconductor is on a top side of a substrate. The metal layer is patterned to define a p-metal. The p-type semiconductor is etched using the p-metal as an etch mask. Similarly, the n-type semiconductor is etched using the p-metal and the p-type semiconductor as an etch mask. A negative photoresist layer is deposited over the patterned p-metal and the p-type semiconductor. The negative photoresist is then exposed from the back side of the substrate, thus exposing the regions of the negative photoresist that are not masked by the p-metal. The negative photoresist is then developed to expose the p-metal.
1. A method of fabricating a light emitting diode (LED) device, comprising:
depositing a metal layer on a p-type semiconductor, the p-type semiconductor disposed on an n-type semiconductor, the n-type semiconductor disposed on a top side of a substrate;
patterning the metal layer to define a p-metal;
etching the p-type semiconductor, the etching of the p-type semiconductor aligned to the patterned p-metal;
depositing a negative photoresist layer, the negative photoresist layer over the patterned p-metal and the p-type semiconductor;
exposing the negative photoresist from a back side of the substrate at an opposite side of the top side of the substrate; and
developing the negative photoresist to expose the p-metal.
2. The method of claim 1 , wherein the exposure of portions of the negative photoresist is masked by the p-metal underneath the negative photoresist.
3. The method of claim 1 , further comprising:
depositing a bond metal over the developed negative photoresist, wherein the bond metal is in contact the exposed p-metal.
4. The method of claim 1 , wherein the developed negative photoresist is dielectric material.
5. The method of claim 1 , further comprising:
wet etching a side surface of the p-metal to form an undercut.
6. The method of claim 1 , wherein patterning the metal layer comprises:
depositing a layer of photoresist over the metal layer;
patterning the layer of photoresist; and
etching the metal layer based on the patterned layer of photoresist.
7. The method of claim 1 , wherein an active layer is disposed between the p-type semiconductor and the n-type semiconductor, and wherein the method further comprises:
etching the active layer and the n-type semiconductor, the etching of the active layer and the n-type semiconductor in alignment with the patterned p-metal.
8. The method of claim 7 , wherein the active layer and at least a portion of the n-type semiconductor are etched in alignment with the patterned p-metal.
9. The method of claim 1 , further comprising:
depositing a dielectric layer over the etched p-type semiconductor and the p-metal,
forming an opening of the dielectric layer on the p-metal,
wherein the negative photoresist is deposited over the dielectric layer, and
wherein the dielectric layer is etched in alignment with the developed negative photoresist.
10. The method of claim 9 , wherein the dielectric layer comprises an oxide or nitride.
11. The method of claim 9 , wherein the dielectric layer is disposed at least on a side of the etched p-type semiconductor.
12. A light-emitting-diode (LED) fabricated by a process comprising the steps of:
depositing a metal layer on a p-type semiconductor, the p-type semiconductor disposed on an n-type semiconductor, the n-type semiconductor disposed on a top side of a substrate;
patterning the metal layer to define a p-metal;
etching the p-type semiconductor, the etching of the p-type semiconductor in alignment with the patterned p-metal;
depositing a negative photoresist layer, the negative photoresist layer over the patterned p-metal and the p-type semiconductor;
exposing the negative photoresist from a back side of the substrate at an opposite side of the top side of the substrate; and
developing the negative photoresist to expose the p-metal.
13. The LED of claim 12 , wherein the exposure of portions of the negative photoresist is masked by the p-metal underneath the negative photoresist.
14. The LED of claim 12 , further fabricated by a process comprising the steps of:
depositing a bond metal over the developed negative photoresist, wherein the bond metal is in contact the exposed p-metal.
15. The LED of claim 12 , wherein the developed negative photoresist is dielectric material.
16. The LED of claim 12 , further fabricated by a process comprising the steps of:
wet etching a side surface of the p-metal to form an undercut.
17. The LED of claim 12 , wherein patterning the metal layer comprises:
depositing a layer of photoresist over the metal layer;
patterning the layer of photoresist; and
etching the metal layer based on the patterned layer of photoresist.
18. The LED of claim 12 , wherein a thickness of the metal layer is greater than a thickness of the negative photoresist.
19. The LED of claim 12 , wherein an active layer is disposed between the p-type semiconductor and the n-type semiconductor, and wherein the method further comprises:
etching the active layer and the n-type semiconductor, the etching of the active layer and the n-type semiconductor in alignment with the patterned p-metal.
20. A non-transitory computer readable storage medium configured to store instructions, the instructions, when executed by a fabrication tool, cause the fabrication tool to:
deposit a metal layer on a p-type semiconductor, the p-type semiconductor disposed on an n-type semiconductor, the n-type semiconductor disposed on a top side of a substrate;
pattern the metal layer to define a p-metal;
etch the p-type semiconductor, the etching of the p-type semiconductor in alignment with the patterned p-metal;
deposit a negative photoresist layer, the negative photoresist layer over the patterned p-metal and the p-type semiconductor;
expose the negative photoresist from a back side of the substrate at an opposite side of the top side of the substrate; and
develop the negative photoresist to expose the p-metal.