Emissive Display Substrate for Surface Mount Micro-LED Fluidic Assembly

• US 20190319015A1
• Filed: 05/08/2019
• Published: 10/17/2019
• Est. Priority Date: 10/31/2014
• Status: Active Grant

• Current Assignee: Elux Inc.
• Original Assignee: Elux Inc.
• Inventors: Schuele, Paul J., Zhan, Changqing, Sasaki, Kenji, Ulmer, Kurt, Lee, Jong-Jan
• Granted Patent: US 10,643,981 B2
• Time in Patent Office: Days
• CPC Class Codes: H01L 25/0753 the devices being arranged next to each other
• CPC Class Codes: H01L 2933/0033 relating to semiconductor body packages
• CPC Class Codes: H01L 2933/0066 relating to arrangements for conducting electric current to or from the semiconductor body
• CPC Class Codes: H01L 33/38 with a particular shape
• CPC Class Codes: H01L 33/486 adapted for surface mounting
• CPC Class Codes: H01L 33/62 Arrangements for conducting electric current to or from the semiconductor body, e.g. lead-frames, wire-bonds or solder balls

Abstract

Planar surface mount (SM) micro light emitting diodes (μLEDs) are presented. The fabrication method provides a MOCVD LED structure with a stack including a first doped semiconductor in a first plane, a MQW layer overlying the first doped semiconductor in a second plane, and a second doped semiconductor overlying the MQW layer in a third plane. An electrical insulator is conformally deposited over the etched stack in a fourth plane, and etched to expose the second doped semiconductor, creating a first via. Etching exposes the first doped semiconductor, creating a second via. A first electrode is connected to the second doped semiconductor through the first via, and has a substrate interface surface in a fifth plane with an average planarity tolerance of less than 10 nanometers. A second electrode is connected to the first doped semiconductor through the second via, and has a substrate interface surface in the fifth plane.

Claims

1. An emissive display substrate comprising:

a support substrate with a planar top surface and a light emitting diode (LED) cross-point control matrix comprising an array of column and row conductive lines;

a first thin-film layer overlying the support substrate top surface, comprising a plurality of wells; and

,

wherein each well has a convex bottom surface, a first substrate electrode connected to a corresponding column line, and a second substrate electrode connected to a corresponding row line.

2. The emissive display substrate of claim 1 further comprising:

a second thin-film layer interposed between the support substrate top surface and the first thin-film layer;

a shim interposed between the support substrate top surface and the second thin-film layer, underlying each well bottom.

3. The emissive display substrate of claim 2 wherein the first thin-film layer wells each have a first diameter;

wherein the shim has a width less than the first diameter, and a top surface; and

,

wherein the well convex bottom surface is responsive to the difference in height between the shim top surface and the support substrate top surface.

4. The emissive display substrate of claim 2 wherein the shim is selected from the group consisting of electrically conductive and electrically insulative materials.

5. The emissive display substrate of claim 2 wherein the first substrate electrode is a center substrate electrode having a first electrical interface surface for electrical connection to a micro-LED, and the second substrate electrode is a perimeter substrate electrode having a second electrical interface surface, lower than the first electrical interface surface, as defined with respect to the support substrate top surface, for electrical connection to a micro-LED.

6. The emissive display substrate of claim 2 wherein the shim directly overlies the column line, forming a column interconnect shim;

wherein the second thin-film layer includes a via overlying the column interconnect shim; and

,

wherein the first substrate electrode is a center substrate electrode overlying the via and connected to the column interconnect shim.

7. The emissive display substrate of claim 5 further comprising:

surface mount micro-LEDs populating the wells, each micro-LED having a top surface with a center first electrode and a perimeter second electrode, having substrate interface surfaces connected, respectively, to the first substrate electrode and second substrate electrode.

8. The emissive display substrate of claim 7 wherein the micro-LED center first electrode and perimeter second electrode have co-planar substrate interface surfaces.

9. The emissive substrate of claim 8 wherein the surface mount micro-LEDs are selected from the group consisting of center emission, perimeter emission, and full area emission micro-LEDs.

10. The emissive display substrate of claim 7 wherein the micro-LED center first electrode and perimeter second electrode substrate interface surfaces are not co-planar.

11. A method for fabricating an emissive display substrate, the method comprising:

providing a support substrate with a planar top surface and a light emitting diode (LED) cross-point control matrix comprising an array of column and row conductive lines;

forming an array of convex well bottom structures overlying the support substrate top surface;

forming a first thin-film layer overlying the support substrate top surface and convex well bottom structures; and

,

forming wells in the first thin-film layer, exposing the convex well bottom structures.

12. The method of claim 11 wherein forming the array of convex well bottom structures includes, for each convex well bottom structure, forming a first substrate electrode electrically connected to a corresponding column line, and a second substrate electrode electrically connected to a corresponding row line.

13. The method of claim 12 wherein forming the array of convex well bottom structures includes:

prior to forming the first thin-film layer, forming an array of shims overlying the support substrate top surface; and

,

forming a second thin-film layer overlying the array of shims.

14. The method of claim 13 wherein forming the array of shims includes forming shims having a width and a top surface;

wherein forming the wells in the first thin-film layer includes forming wells having a diameter greater than the shim width; and

,

wherein the shape of the well convex bottom surface is responsive to the difference in height between the shim top surface and the support substrate top surface.

15. The method of claim 13 wherein forming the array of shims includes forming shims from a material selected from the group consisting of electrically conductive and electrically insulative materials.

16. The method of claim 12 wherein forming the array of convex well bottom structures includes:

forming a center first substrate electrode having a first electrical interface surface for electrical connection to a micro-LED; and

,

forming a perimeter second substrate electrode having a second electrical interface surface, lower than the first electrical interface surface, as defined with respect to the support substrate top surface, for electrical connection to a micro-LED.

17. The method of claim 16 wherein forming the array of shims includes forming each shim directly overlying the column line, forming a column interconnect shim;

wherein forming the second thin-film layer includes forming a via in the second thin-film layer overlying each column interconnect shim; and

,

wherein forming the center first substrate electrode includes forming the center first substrate electrode overlying the via and electrically connected to the column interconnect shim.

18. The method of claim 11 further comprising:

fluidically depositing surface mount micro-LEDs in the wells.

19. The method of claim 18 wherein depositing the surface mount micro-LEDs includes populating the wells with micro-LEDs having a top surface with a center first electrode and a perimeter second electrode, having substrate interface surfaces connected, respectively, to the first substrate electrode and second substrate electrode.

20. The method of claim 19 wherein depositing the surface mount micro-LEDs includes depositing micro-LEDs having center first electrode and perimeter second electrode co-planar substrate interface surfaces.

21. The method of claim 20 wherein depositing the surface mount micro-LEDs includes depositing micro-LEDs selected from the group consisting of center emission, perimeter emission, and full area emission micro-LEDs.

22. The method of claim 19 wherein depositing the surface mount micro-LEDs includes depositing micro-LEDs having non co-planar center first electrode and perimeter second electrode substrate interface surfaces.