QD color conversion U-display structure and manufacturing method

Abstract

Embodiments of the present disclosure generally relate to LED pixels and methods of fabricating LED pixels, including a device comprising: a backplane; at least three LEDs disposed on the backplane; a subpixel isolation (SI) structure arranged to define at least three subpixel wells, wherein a reflective material is disposed on the sidewalls and top surface of the SI structure, and at least three of the subpixels have a color conversion material disposed in the wells; an encapsulation layer disposed above the subpixel isolation structure and the subpixels; an optical filter layer disposed above the encapsulation layer; and a microlens disposed above the optical filter layer and above each of the subpixel wells.

Description

[Technical Field]

[0001] FIELD OF THE DISCLOSURE Embodiments of the present disclosure generally relate to LED pixels and methods of fabricating LED pixels. [Background technology]

[0002] Light-emitting diode (LED) panels use arrays of LEDs, where each LED provides an individually controllable pixel element. Such LED panels can be used in computers, touchscreen devices, personal digital assistants (PDAs), mobile phones, television monitors, etc.

[0003] LED panels using micron-scale LEDs (also called micro-LEDs) based on III-V semiconductor technology offer various advantages over OLEDs, such as higher energy efficiency, higher brightness, and longer lifetimes, as well as potentially easier manufacturing due to fewer material layers in the display stack. However, manufacturing micro-LED panels presents challenges. Micro-LEDs with different color emissions (e.g., red, green, and blue pixels) must be fabricated on different substrates using separate processes. Integrating multi-color micro-LED devices into a single panel requires a pick-and-place step to transfer the micro-LED devices from their original donor substrate to a destination substrate. This often involves modifying the LED structure or manufacturing process, such as introducing a sacrificial layer to facilitate demolding. Additionally, stringent requirements for placement accuracy (e.g., less than 1 μm) limit throughput, final yield, or both.

[0004] An alternative approach that avoids the pick-and-place step is to selectively deposit color conversion agents (e.g., quantum dots, nanostructures, photoluminescent materials, or organics) at specific pixel locations on the substrate where the monochromatic LEDs are fabricated. Monochromatic LEDs can generate relatively short wavelength light, e.g., violet or blue light, and color conversion agents can convert this short wavelength light to longer wavelength light, e.g., red or green light for red or green pixels. Selective deposition of color conversion agents can be performed using high-resolution shadow masks or controllable inkjet or aerosol jet printing. Summary of the Invention

[0005] In one embodiment, a device is provided that includes a backplane, LEDs disposed above the backplane, subpixel isolation (SI) structures disposed above the LEDs to define subpixel wells, each well containing a respective LED between adjacent SI structures, the subpixels having different color conversion materials disposed within the wells, and a microlens disposed above each of the subpixel wells, the microlens including an optical filter material.

[0006] In another embodiment, a device is provided that includes a backplane, LEDs disposed above the backplane, subpixel isolation (SI) structures disposed above the LEDs to define subpixel wells, each well including a respective LED between adjacent SI structures, the subpixels having different color conversion materials disposed within the wells, an encapsulation layer above the SI structures and the subpixels, an optical filter layer disposed above the encapsulation layer, a second passivation layer disposed on the optical filter layer, and a microlens disposed above the optical filter layer and above each of the subpixel wells.

[0007] In another embodiment, a device is provided that includes a backplane, LEDs disposed above the backplane, and subpixel isolation (SI) structures disposed above the LEDs to define subpixel wells, each well containing a respective LED between adjacent SI structures, the subpixels having different color conversion materials disposed in the wells, the device being fabricated by a process that includes disposing an optical filter layer above the wells and the SI structures, and performing a nanoimprint lithography process to form microlenses from the optical filter layer above the subpixels.

[0008] In another embodiment, a device is provided that includes a backplane, LEDs disposed above the backplane, subpixel isolation (SI) structures disposed above the LEDs to define subpixel wells, each well including a respective LED between adjacent SI structures, the subpixels having different color conversion materials disposed in the wells, an encapsulation layer above the SI structures and the subpixels, an optical filter layer disposed above the encapsulation layer, and a second passivation layer disposed on the optical filter layer, the device being fabricated by a process that includes disposing resist on the second passivation layer, patterning the resist to form portions above the subpixels, and performing one of a grayscale process, a thermal reflow process, or a nanoimprint lithography process to form microlenses from the portions of the resist above the subpixels.

[0009] In yet another embodiment, a method is provided, the method including: depositing a reflective material at an angle above a backplane, the backplane having LEDs disposed thereover, subpixel isolation (SI) structures disposed above the LEDs to define subpixel wells, each well containing a respective LED between adjacent SI structures, the reflective material being deposited on one sidewall and a top surface of the SI structures; rotating the backplane by at least 90 degrees; and depositing the reflective material at an angle.

[0010] In order that the above-mentioned features of the present disclosure may be understood in detail, a more particular description of the present disclosure briefly summarized above can be made by reference to embodiments, some of which are illustrated in the accompanying drawings. It should be noted, however, that the accompanying drawings illustrate only exemplary embodiments and therefore should not be considered as limiting the scope of the present disclosure, as other embodiments may be recognized that are equally effective. [Brief explanation of the drawings]

[0011] [Figure 1A] 1 is a schematic cross-sectional view of a pixel having a first microlens arrangement according to an embodiment. [Figure 1B] 10 is a schematic cross-sectional view of a pixel having a second microlens arrangement according to an embodiment. [Figure 2] FIG. 10 is a flow diagram of a method for forming a reflective material on a sub-pixel separating structure, according to an embodiment. [Figures 3A-3E] 2 is a schematic cross-sectional view of a backplane during a method 200 according to an embodiment. [Figure 4] FIG. 4 is a flow diagram of a method 400 for forming sub-pixels, according to an embodiment. [Figures 5A-5C] 4 is a schematic cross-sectional view of a backplane during a method 400 according to an embodiment. [Figure 6] FIG. 4 is a flow diagram of a method 400 for forming sub-pixels, according to an embodiment. [Figure 7A-7C] 6 is a schematic cross-sectional view of a backplane during a method 600 according to an embodiment. [Figure 8A] 1 is a cross-sectional view of a backplane during formation of a first microlens arrangement, according to an embodiment. [Figure 8B] 1 is a cross-sectional view of a backplane during formation of a first microlens arrangement, according to an embodiment. [Figure 8C] FIG. 10 is a cross-sectional view of a backplane during formation of a second microlens arrangement, according to an embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0012] To facilitate understanding, wherever possible, like reference numerals will be used to refer to like elements common to the figures. It is contemplated that elements and features of one embodiment may be beneficially incorporated in other embodiments without further description.

[0013] Embodiments of the present disclosure generally relate to LED pixels and methods of fabricating LED pixels, including a device comprising: a backplane; at least three LEDs disposed on the backplane; a subpixel isolation (SI) structure arranged to define at least three subpixel wells, wherein a reflective material is disposed on the sidewalls and top surface of the SI structure, and at least three of the subpixels have a color conversion material disposed in the wells; an encapsulation layer disposed above the subpixel isolation structure and the subpixels; an optical filter layer disposed above the encapsulation layer; and a microlens disposed above the optical filter layer and above each of the subpixel wells.

[0014] FIG. 1A is a schematic cross-sectional view of a pixel 100 having a first microlens arrangement 101A. FIG. 1B is a schematic cross-sectional view of a pixel 100 having a second microlens arrangement 101B. The pixel 100 includes at least three LEDs 104 disposed on a backplane 102. An isolation material 106 can be disposed between the LEDs 104. The LEDs 104 are integrated with the backplane circuitry, so that each LED 104 can be individually addressed. For example, the circuitry of the backplane 102 can include a TFT active matrix array including a thin-film transistor and storage capacitor (not shown) for each LED, column and row address lines, and column and row drivers to drive the LEDs 104. Alternatively, the LEDs 104 can be driven by a passive matrix within the backplane circuitry. The backplane 102 can be fabricated using a conventional CMOS process. Each LED is configured to emit UV light within a first wavelength range. The UV light can be white light. The LEDs 104 can be micro LEDs.

[0015] A passivation layer 108 is disposed above the LED 104, and in some embodiments, directly on the LED 104. A subpixel isolation (SI) structure 110 is disposed above the passivation layer 108, and in some embodiments (shown in FIG. 1B ), on the passivation layer 108. Adjacent subpixel isolation structures define respective wells 113 of at least three subpixels 112. The subpixels 112 include a red subpixel 112a having a red color conversion material disposed in the well 113 of the red subpixel 112a, a green subpixel 112b having a green color conversion material disposed in the well 113 of the green subpixel 112b, and a blue subpixel 112c having a blue color conversion material disposed in the well 113 of the blue subpixel 112c. When the LED 104a of the red subpixel 112a is turned on, the red color conversion material converts light emitted from the LED 104a to red light. When the LED 104c of the blue subpixel 112c is turned on, the blue color conversion material converts the light emitted from the LED 104c to blue light. In one embodiment, the pixel 100 includes a fourth subpixel 112d. As shown in FIG. 1A, the fourth subpixel 112d does not include a color conversion material, i.e., there is no color conversion layer. As shown in FIG. 1B, the fourth subpixel 112d includes a sacrificial material 115. In other embodiments, at least three subpixels 112 include the same color conversion material. The fourth subpixel 112d may be filled with a color conversion material later.

[0016] The subpixel separating structure 110 includes a photoresist material, such as an epoxy-based resist. The photoresist material is a negative photoresist. A reflective material 118 is disposed on the exposed surfaces 116 of the subpixel separating structure 110, i.e., the sidewalls and top surface. The reflective material 118 on the exposed surfaces 116 reflects the emitted light, confining the converted light to each subpixel and collimating the light toward the display. The reflective material 118 includes, but is not limited to, aluminum, silver, combinations thereof, and the like. In one embodiment, as shown in FIG. 1A , an antireflective material 120 is disposed between the subpixel separating structure 110 and the passivation layer 108. The antireflective material 120 may include chromium nitride (CrN).

[0017] An encapsulation layer 122 is disposed above the subpixel separation structure 110 and the subpixels 112. As shown in FIG. 1A , the first microlens arrangement 101A includes a light filter layer 124 disposed above the encapsulation layer 122. A second passivation layer 126 is disposed on the light filter layer 124, and a microlens 128 is disposed on the second passivation layer 126 and above each of the wells 113 of the subpixels 112. The light filter layer 124 may be selective to photons of a certain wavelength. In some embodiments, the light filter layer 124 is a UV blocking layer, a UV reflective layer, a blue light blocking layer, a blue light reflective layer, or a combination thereof. The light filter layer 124 may include a UV blocking material, a UV reflective material, a blue light blocking material, a blue light reflective material, or a combination thereof. The second passivation layer 126 may include silicon nitride. 1B, the second microlens arrangement 101B includes microlenses 128 disposed on the encapsulation layer 122 and above each of the wells 113 of the subpixels 112. A second passivation layer 126 is disposed on the microlenses 128. The microlenses 128 of the second microlens arrangement 101B include a resist material, such as a photoresist material, that blocks UV light.

[0018] FIG. 2 is a flow diagram of a method 200 of forming a reflective material 118 on a subpixel separating structure 110. FIGS. 3A-3E are schematic cross-sectional views of a backplane 102 during method 200. In operation 201, as shown in FIGS. 3A and 3B, a resist layer 301 is patterned to form a subpixel separating structure 110. The resist layer can be patterned by a photoresist patterning process. The subpixel separating structures 110 can have a width 303 of about 1 μm to about 4 μm, e.g., 2 μm to 3 μm. The subpixel separating structures 110 can have a pitch 304 of about 2 μm to about 6 μm, e.g., about 4 μm. The subpixel separating structures 110 can have a thickness 305 of about 2 μm to about 12 μm, e.g., 5 μm to 10 μm. In some embodiments, an antireflective material 120 is disposed between the subpixel separating structure 110 and the passivation layer 108, as shown in FIG. 3E. Once the resist layer 301 is patterned, remaining portions of the antireflective material 120 disposed between the subpixel separating structures 110 are removed. The antireflective material 120 helps define the subpixel separating structures 110 during photoresist patterning. In operation 202, as shown in FIG. 3C, a reflective material 118 is deposited at an angle α. The deposition process includes PVD. The angle α can be between 10 degrees and 35 degrees. The reflective material 118 is deposited on one sidewall and the top surface of the exposed surface 116 of the subpixel separating structures 110. In operation 203, the backplane 102 is rotated at least 90 degrees, and the reflective material 118 is deposited at the angle α. For a four-sided subpixel separating structure 110, the backplane 102 is rotated 90 degrees, and the reflective material 118 is deposited three more times. Operation 203 is repeated twice so that reflective material 118 is deposited on the four sidewalls and top surface of subpixel separating structure 110, as shown in Figures 3D and 3E. For circular wells 113, backplane 102 is rotated 360 degrees and reflective material 118 is deposited.

[0019] FIG. 4 is a flow diagram of method 400 for forming subpixels 112. FIGS. 5A-5C are schematic cross-sectional views of backplane 102 during method 400 for forming subpixels 112. In operation 401, as shown in FIG. 5A, a first color conversion material is deposited into each of the wells 113 of subpixels 112. Operation 401 occurs after method 200. In one embodiment, the first color conversion material is a red color conversion material for red subpixel 112a. In operation 402, as shown in FIG. 5B, the first color conversion material of the first subpixel is cured and the first color conversion material in the wells of the remaining subpixels is removed. The first subpixel may correspond to red subpixel 112a. In operation 403, operations 401 and 402 are repeated for the second color conversion material of the second subpixel and the third color conversion material of the third subpixel, as shown in FIG. 5C. The first, second, and third conversion materials are hardened by laser hardening and removed by washing. In one embodiment, the second color conversion material is a green color conversion material for green subpixel 112b, and the third color conversion material is a blue color conversion material for blue subpixel 112c. Operations 401 and 402 may be repeated for fourth subpixel 112d.

[0020] FIG. 6 is a flow diagram of a method 600 for forming subpixels 112. FIGS. 7A-7C are schematic cross-sectional views of the backplane 102 during the method 600 for forming subpixels 112. In operation 601, a sacrificial material 115 is deposited in each of the wells 113 of the subpixels 112. Operation 601 occurs after method 200. In operation 602, the sacrificial material 115 in the wells of the first subpixel is removed, as shown in FIGS. 7A and 7B. The sacrificial material 115 is a positive photoresist. The sacrificial material 115 may be deposited by spin coating. When the sacrificial material 115 is developed, the sacrificial material 115 is removed, and the wells of the first subpixel may be exposed to light through the openings in the mask 702. In operation 603, a first color conversion material is deposited and cured in the wells of the first subpixel, as shown in FIG. 7C. In one embodiment, the first color conversion material is a red color conversion material, and the first subpixel is red subpixel 112a. In operation 604, operations 602 and 603 are repeated for the second and third subpixels, as shown in FIG. 5C. The first, second, and third conversion materials are cured by laser curing. In one embodiment, the second color conversion material is a green color conversion material for green subpixel 112b, and the third color conversion material is a blue color conversion material for blue subpixel 112c. Operations 602 and 603 may be repeated for the fourth subpixel 112d.

[0021] To form the first microlens arrangement 101A of the pixel 100, an encapsulation layer 122 is disposed above the subpixel separation structure 110 and the subpixels 112. An optical filter layer 124 is disposed above the encapsulation layer 122. A second passivation layer 126 is disposed on the optical filter layer 124. The optical filter layer 124 may be selective to photons of certain wavelengths. In some embodiments, the optical filter layer 124 is a UV blocking layer, a UV reflective layer, a blue light blocking layer, a blue light reflective layer, or a combination thereof. The optical filter layer 124 may include a UV blocking material, a UV reflective material, a blue light blocking material, a blue light reflective material, or a combination thereof. FIGS. 8A and 8B are cross-sectional views of the backplane 102 during the formation of the first microlens arrangement 101A. A resist 802 is disposed on the second passivation layer 126. In one embodiment, as shown in Figure 8A, resist 802 is patterned such that resist 802 remains over each of the wells 113 of subpixels 112. The resist 802 is grayscale patterned or subjected to a thermal reflow process to form microlenses 128 as shown in Figure 1A. In another embodiment, as shown in Figure 8B, resist 802 is imprinted with a stamp (e.g., by nanoimprint lithography) to form microlenses 128 as shown in Figure 1A.

[0022] 8C is a cross-sectional view of the backplane 102 during the formation of the second microlens arrangement 101B. To form the second microlens arrangement 101B of the pixel 100, an encapsulation layer 122 is disposed over the subpixel separation structure 110 and the subpixels 112. A resist 804 is disposed on the encapsulation layer 122. The resist 804 is imprinted using a stamp to form the microlenses 128 as shown in FIG. 1B. The resist 804 includes an optical filter material. In some embodiments, the optical filter material includes a UV-blocking material, a UV-reflecting material, a blue-light-blocking material, a blue-light-reflecting material, or a combination thereof. A second passivation layer 126 is disposed over the microlenses 128.

[0023] While the foregoing is directed to embodiments of the present disclosure, other and further embodiments of the present disclosure may be devised without departing from the basic scope thereof, which scope is determined by the following claims.

Claims

1. A device, a backplane; an LED disposed above the backplane; subpixel isolation (SI) structures disposed over the LEDs to define subpixel wells, each well containing a respective LED between adjacent SI structures, the subpixels having different color conversion materials disposed within the wells; a microlens disposed over each of the wells of the subpixels, the microlens comprising an optical filter material; and 1. A device comprising:

2. The device of claim 1 , wherein the light filter layer is a UV blocking layer, a UV reflective layer, a blue light blocking layer, or a blue light reflective layer.

3. The device of claim 1 , wherein an anti-reflective material is disposed between the SI structure and the backplane.

4. The device of claim 1 , wherein an encapsulation layer is disposed below the microlenses and above the SI structure and the subpixels.

5. The device of claim 1 , wherein a second passivation layer is disposed on the microlens.

6. The device of claim 1 , wherein a reflective material is disposed on the sidewalls and top surface of the SI structure.

7. The device of claim 1 further comprising four sub-pixels, wherein the well of each of the fourth sub-pixels comprises a sacrificial material or a color conversion material.

8. A device, a backplane; an LED disposed above the backplane; subpixel isolation (SI) structures disposed over the LEDs to define subpixel wells, each well containing a respective LED between adjacent SI structures, the subpixels having different color conversion materials disposed within the wells; an encapsulation layer above the SI structure and the subpixels; an optical filter layer disposed above the encapsulation layer; a second passivation layer disposed on the optical filter layer; a microlens disposed above the optical filter layer and above each of the wells of the subpixels; 1. A device comprising:

9. The device of claim 8 , wherein the light filter layer is a UV blocking layer, a UV reflective layer, a blue light blocking layer, or a blue light reflective layer.

10. The device of claim 8 , wherein an anti-reflective material is disposed between the SI structure and the backplane.

11. The device of claim 8 , wherein at least three of the subpixels have different color conversion materials.

12. 10. The device of claim 8, further comprising four sub-pixels, wherein the well of each of the fourth sub-pixels comprises a sacrificial material or a color conversion material.

13. A device, a backplane; an LED disposed above the backplane; subpixel isolation (SI) structures disposed above the LEDs to define subpixel wells, each well containing a respective LED between adjacent SI structures, the subpixels having different color conversion materials disposed within the wells; and Equipped with the device comprising: disposing an optical filter layer over the well and the SI structure; and performing a nanoimprint lithography process to form microlenses from the optical filter layer above the subpixels; 1. A device manufactured by a process including:

14. The device of claim 13 , wherein an encapsulation layer is disposed below the microlenses and above the SI structure and the subpixels.

15. The device of claim 13 , wherein a second passivation layer is disposed on the microlens.

16. The device of claim 13 , wherein a reflective material is disposed on the sidewalls and top surface of the SI structure.

17. 14. The device of claim 13, further comprising four sub-pixels, wherein the well of each of the fourth sub-pixels comprises a sacrificial material or a color conversion material.

18. A device, a backplane; an LED disposed above the backplane; subpixel isolation (SI) structures disposed over the LEDs to define subpixel wells, each well containing a respective LED between adjacent SI structures, the subpixels having different color conversion materials disposed within the wells; an encapsulation layer above the SI structure and the subpixels; an optical filter layer disposed above the encapsulation layer; a second passivation layer disposed on the optical filter layer; and Equipped with the device comprising: placing a resist on the second passivation layer; patterning the resist to form upper portions of the subpixels; and performing one of a grayscale process, a thermal reflow process, or a nanoimprint lithography process to form microlenses from the portions of the resist above the subpixels.

1. A device manufactured by a process including:

19. 20. The device of claim 18, wherein a reflective material is disposed on the sidewalls and top surface of the SI structure.

20. 20. The device of claim 19, further comprising four sub-pixels, wherein the well of each of the fourth sub-pixels comprises a sacrificial material or a color conversion material.

21. 1. A method comprising: depositing a reflective material at an angle above a backplane, the backplane having LEDs disposed thereover, subpixel isolation (SI) structures disposed above the LEDs to define subpixel wells, each well containing a respective LED between adjacent SI structures, the reflective material being deposited on one sidewall and a top surface of the SI structures; rotating the backplane by at least 90 degrees; depositing the reflective material at the angle; A method comprising:

22. depositing a first color conversion material into a first well of the first subpixel, a second well of the second subpixel, and a third well of the third subpixel; curing the first color conversion material in the first well; removing the first color conversion material in the second well and the third well; depositing a second color conversion material into the second well of the second sub-pixel and the third well of the third sub-pixel; curing the second color conversion material in the second well; removing the second color conversion material in the third well; depositing a third color conversion material in the third well of the third subpixel; curing the third color conversion material in the third well; and 22. The method of claim 21 further comprising:

23. depositing a sacrificial material into a first well of the first subpixel, a second well of the second subpixel, and a third well of the third subpixel; exposing the sacrificial material in the first well to light through an opening in a mask; removing the exposed sacrificial material in the first well; depositing a first color conversion material into the first well; exposing the sacrificial material in the second well to light through the opening in the mask; depositing a second color conversion material in the second well; exposing the sacrificial material in the third well to light through the opening in the mask; depositing a third color conversion material in the third well; 22. The method of claim 21 further comprising:

24. 22. The method of claim 21 , further comprising: repeating rotating the backplane 90 degrees and depositing the reflective material twice so that the reflective material is deposited on four sidewalls and the top surface of the SI structure.

25. disposing an encapsulation layer over the SI structure and the subpixels; disposing an optical filter layer above the encapsulation layer; disposing a second passivation layer over the optical filter layer; placing a resist on the second passivation layer; patterning the resist to form upper portions of the subpixels; performing one of a grayscale process, a thermal reflow process, or a nanoimprint lithography process to form microlenses from the portions of the resist above the subpixels; 22. The method of claim 21 further comprising:

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