Series connection of two light emitting diodes through semiconductor manufacture process

• US 20050062049A1
• Filed: 06/29/2004
• Published: 03/24/2005
• Est. Priority Date: 09/23/2003
• Status: Active Grant

• Current Assignee: Epistar Corporation
• Original Assignee: United Epitaxy Company (Epistar Corporation)
• Inventors: Lin, Jin-Ywan, Tu, Chung-Cheng
• Granted Patent: US 6,998,642 B2
• Time in Patent Office: Days
• US Class Current: 257/79
• CPC Class Codes: H01L 27/153 in a repetitive configuration, e.g. LED bars

Abstract

A semiconductor structure with two light emitting diodes in series connection is disclosed. The semiconductor structure comprises two light emitting diodes (LEDs) having the same stack layers and abutting each other but spaced by an isolation trench. The stack layers from a bottom thereof include a thermal conductive substrate, an nonconductive protective layer, a metal adhering layer, a mirror protective layer, a p-type ohmic contact epi-layer, a upper cladding layer, an active layer, and a lower cladding layer. Two p-type ohmic contact metal electrodes for two LEDs are formed on an interface between the mirror protective layer and the ohmic contact epi-layer and buried in the mirror protective layer. The stack layers have first trenches formed therein which exposes the upper cladding layer and electrical connecting channels to connect p-type electrodes. The isolation trench is formed by patterning the exposed upper cladding layer until further exposing the nonconductive protective layer. Two n-type electrodes are formed on the lower cladding layer of two LEDs. A dielectric layer is deposited to fill the isolation trench and covered a sidewall of the first trench so that it can electrically isolate layers of the stack layers of the second LED while a metal connection trace formed thereon to connect the p-type ohmic contact electrode of the first LED and n-type of ohmic electrode of second LED.

Claims

1. A semiconductor structure of series connection of two light emitting diodes, comprising:

a first light emitting diode having stack layers from a bottom thereof including a thermal conductive substrate, an nonconductive protective layer, a metal adhering layer, a mirror protective layer, an ohmic contact epi-layer, a upper cladding layer, an active layer, and a lower cladding layer, further, a first ohmic contact metal electrode formed on an interface between said mirror protective layer and said ohmic contact epi-layer and buried in said mirror protective layer, a second ohmic contact metal electrode formed on said lower cladding layer;

a second light emitting diode having the same stack layers as said first light emitting diode;

still wherein both of said light emitting diodes, respectively, have a first trench formed therein which has a bottom exposed said ohmic contact epi-layer and said trench bottom contains an electrical conductive channel connecting said first ohmic contact metal electrode;

an isolation trench formed at a border of said first trench and with a bottom exposed said nonconductive protective layer to isolate said first light emitting diode and said second light emitting diode;

a dielectric layer formed to fill in said isolation trench and extend to a sidewall of said first trench, said sidewall being a boundary between said first and said second light emitting diode; and

a metal bonding layer formed on said dielectric layer and extended to connect said second ohmic contact metal electrode of said first light emitting diode and said second ohmic contact metal electrode of said second light emitting diode.

2. The semiconductor structure according to claim 1, wherein said mirror protective layer is selected one from the group consisting of ITO, In2O3, SnO, ZnO, MgO, Al₂O₃, SiO₂, SiNx, SOG (spin on glass), silicone, BCB (B-staged bisbenzocyclobutene), epoxy, polyimide, and the combination thereof.

3. The semiconductor structure according to claim 2, further comprising channels in said mirror protective layer to provide a connection between said metal adhering layer and said first ohmic contact metal electrode while said mirror protective layer is a non-conductive type.

4. The semiconductor structure according to claim 1, wherein said thermal conductive substrate is selected from the group consisting of Al, Au, Cu, Si, and SiC.

5. The semiconductor structure according to claim 1, wherein said metal adhering layer is selected one from the group consisting of In, Au, Ag, and Al and said bonding metal layer is selected one from the group consisting of Au and Al.

6. A method of forming series connection of two light emitting diodes, said method comprising the steps of:

providing a temporary substrate,

forming sequentially an n-type etch stop layer, an lower cladding layer, an active layer, an upper cladding layer, and a p-type ohmic contact epi-layer;

forming two p-type ohmic contact metal electrodes on said p-type ohmic contact epi-layer to define a first light emitting diode and a second light emitting diode;

forming a mirror protective layer on said p-type ohmic contact epi-layer and covering said two p-type ohmic contact metal electrodes;

providing a thermal Conductive substrate;

forming an isolation layer on said thermal conductive substrate;

forming a metal adhering layer on said isolation layer;

bonding said thermal conductive substrate to said mirror protective layer with said metal adhering layer as an adhering agent;

removing said temporary substrate and said n-type etch stop layer;

patterning said lowering cladding layer, said active layer and said upper cladding layer to form a first and a second trench respectively, for said first light emitting diode and said second light emitting diode;

patterning bottoms of said first and said second trench to form two connection channels, respectively, connecting said two p-type ohmic contact metal electrodes;

patterning a bottom of said first trench to form an isolation trench till said isolation layer is exposed so that said first and said second light emitting diode are spaced by said isolation trench;

forming two n-type ohmic contact metal electrodes, respectively, on said lower cladding layer of said first and second light emitting diode;

forming a dielectric layer filling said isolation trench and on a sidewall of said first trench, said sidewall being a boundary between said first and said second light emitting diode; and

forming bonding metal pads on said two n-type ohmic contact metal electrodes and said two connection channels;

forming a conductive trace on said dielectric layer and extended to connect said p-type ohmic contact metal electrode of said first light emitting diode to said n-type second ohmic contact metal electrode of said second light emitting diode.

7. The method according to claim 6, wherein said step of forming a first and a second trench further comprises patterning more until said metal adhering layer is exposed.

8. The method according to claim 6 wherein said mirror protective layer is selected one from the group consisting of ITO, In₂O₃, SnO, ZnO, MgO, Al₂O₃, SiO₂, SiNx, SOG (spin on glass), silicone, BCB (B-staged bisbenzocyclobutene), epoxy, polyimide, and the combination thereof.

9. The method according to claim 6, further comprising forming channels in said mirror protective layer before the step of bonding said thermal conductive substrate to said mirror protective layer to provide a connection between said metal adhering layer and said p-type ohmic contact metal electrode while said mirror protective layer is a non-conductive type.

10. The method according to claim 6, wherein said thermal conductive substrate is selected from the group consisting of Al, Au, Cu, Si and SiC.

11. The method according to claim 6, wherein said metal adhering layer is selected one from the group consisting of In, Au, Ag, and Al and said bonding metal layer is selected one from the group consisting of Au and Al.

12. A method of forming series connection of two light emitting diodes, said method comprising the steps of:

providing a temporary substrate,

forming sequentially an n-type etch stop layer, an lower cladding layer, an active layer, an upper cladding layer, and a p-type ohmic contact epi-layer;

forming two p-type ohmic contact metal electrodes on said p-type ohmic contact epi-layer to define a first light emitting diode and a second light emitting diode;

forming a mirror protective layer on said p-type ohmic contact epi-layer and covering said two p-type ohmic contact metal electrodes;

providing a thermal conductive substrate;

forming an isolation layer on said thermal conductive substrate;

forming a metal adhering layer on said isolation layer;

bonding said thermal conductive substrate to said mirror protective layer with said metal adhering layer as an adhering agent;

removing said temporary substrate and said n-type etch stop layer;

patterning said lowering cladding layer, said active layer, said upper cladding layer, said p-type ohmic contact epi-layer, and said mirror protective layer to expose said metal adhering layer so as to form a first and a second trench respectively, for said first light emitting diode and said second light emitting diode;

patterning a bottom of said first trench to form an isolation trench till said isolation layer is exposed so that said first and said second light emitting diode are spaced by said isolation trench;

forming two n-type ohmic contact metal electrodes, respectively, on said lower cladding layer of said first and second light emitting diode;

forming a dielectric layer filling said isolation trench and on a sidewall of said first trench, said sidewall being a boundary between said first and said second light emitting diode; and

forming bonding metal pads on said two n-type ohmic contact metal electrodes and on said exposed metal adhering layer;

forming a conductive trace on said dielectric layer and extended to connect said p-type ohmic contact metal electrode of said first light emitting diode to said n-type ohmic contact metal electrode of said second light emitting diode.

13. The method according to claim 12 wherein said mirror protective layer is selected one from the group consisting of ITO, In₂O₃, SnO, ZnO, MgO, Al₂O₃, SiO₂, SiNx, SOG (spin on glass), silicone, BCB (B-staged bisbenzocyclobutene), epoxy, polyimide, and the combination thereof.

14. The method ,according to claim 13, further comprising forming channels in said mirror protective layer before the step of bonding said thermal conductive substrate to said mirror protective layer to provide a connection between said metal adhering layer and said p-type ohmic contact metal electrode while said mirror protective layer is a non-conductive type.

15. The method according to claim 12, wherein said thermal conductive substrate is selected from the group consisting of Al, Au, Cu, Si and SiC.

16. The method according to claim 12, wherein said metal adhering layer is selected one from the group consisting of In, Au, Ag, and Al and said bonding metal layer is selected one from the group consisting of Au and Al.