U-display structure with qd color conversion and method of manufacturing the same

Abstract

Embodiments of the present disclosure generally relate to LED pixels and methods of manufacturing LED pixels. The element includes: a backplane; the at least three LEDs are arranged on the back plate; a sub-pixel isolation (SI) structure disposed to define a well of at least three sub-pixels, a reflective material disposed on sidewalls and a top surface of the SI structure, at least three of the sub-pixels having a color conversion material disposed in the well; the packaging layer is arranged above the sub-pixel isolation structure and the sub-pixels; the light filtering layer is arranged above the packaging layer; and a microlens disposed over the filter layer and over each of the sub-pixel wells.

Description

Technical Field

[0001] Embodiments of the present disclosure generally relate to LED pixels and methods of fabricating LED pixels. Background Art

[0002] Light emitting diode (LED) panels use LED arrays where individual LEDs provide individually controllable pixel elements. Such LED panels can be used in computers, touch panel elements, personal digital assistants (PDAs), cellular phones, televisions, and the like.

[0003] Compared to OLEDs, LED panels using micron-scale LEDs (also referred to as micro-LEDs) based on III-V semiconductor technology have various advantages such as higher energy efficiency, higher brightness, longer lifetimes, and fewer material layers in the display stack, which simplifies fabrication. However, fabricating micro-LED panels is challenging. Micro-LEDs with different color emissions (e.g., red, green, and blue pixels) need to be fabricated on different substrates through separate processes. Integrating micro-LED elements of different colors onto a single panel requires pick-and-place steps to transfer the micro-LED elements from their original supply substrates to the target substrate. This often involves modifying the LED structure or fabrication process, such as introducing a sacrificial layer to facilitate die release. Additionally, strict requirements for placement accuracy (e.g., less than 1 μm) limit throughput, final yield, or both.

[0004] One alternative to skip the pick-and-place steps is to selectively deposit color conversion agents (e.g., quantum dots, nanostructures, photoluminescent materials, or organic materials) at specific pixel locations on a substrate fabricated with monochromatic LEDs. The monochromatic LEDs can generate light with a relatively short wavelength, such as violet or blue light, and the color conversion agents can convert this short-wavelength light into light with a longer wavelength, such as red or green light for red or green pixels. Selective deposition of the color conversion agents can be performed using a high-resolution shadow mask or controlled inkjet or aerosol spraying. Summary of the Invention

[0005] In one embodiment, an element is provided. The element includes: a backplane; an LED disposed above the backplane; a subpixel isolation (SI) structure disposed above the LED to define wells of subpixels, each well including a corresponding LED between adjacent SI structures, the subpixels having different color conversion materials disposed in the wells; and microlenses disposed above each of the subpixel wells, the microlenses including filter materials.

[0006] In another embodiment, an element is provided. The element includes: a backplane; an LED disposed above the backplane; a sub-pixel isolation (SI) structure disposed above the LED to define wells of sub-pixels, each well including a corresponding LED between adjacent SI structures, the sub-pixels having different color conversion materials disposed in the wells; a packaging layer located above the SI structure and the sub-pixels; a filter layer disposed above the packaging layer; a second passivation layer disposed on the filter layer; and microlenses disposed above the filter layer and above each of the sub-pixel wells.

[0007] In another embodiment, an element is provided. The element includes: a backplane; an LED disposed above the backplane; a sub-pixel isolation (SI) structure disposed above the LED to define wells of sub-pixels, each well including a corresponding LED between adjacent SI structures, the sub-pixels having different color conversion materials disposed in the wells, wherein the element is fabricated by a process including: disposing a filter layer above the wells and the SI structure, and performing a nanoimprint lithography process to form microlenses from the filter layer above the sub-pixels.

[0008] In another embodiment, an element is provided. The element includes: a backplane; an LED disposed above the backplane; a sub-pixel isolation (SI) structure disposed above the LED to define wells of sub-pixels, each well including a corresponding LED between adjacent SI structures, the sub-pixels having different color conversion materials disposed in the wells; a packaging layer located above the SI structure and the sub-pixels; a filter layer disposed above the packaging layer; and a second passivation layer disposed on the filter layer, wherein the element is fabricated by a process including: disposing a resist on the second passivation layer, patterning the resist to form a plurality of portions above the sub-pixels, 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 sub-pixels.

[0009] According to another embodiment, a method is provided. The method includes: depositing a reflective material at an angle above a backplane having an LED disposed above it, and a sub-pixel isolation (SI) structure disposed above the LED to define wells of sub-pixels, each well including a corresponding LED between adjacent SI structures, depositing the reflective material on a sidewall and a top surface of the SI structure, and rotating the backplane by at least 90 degrees and depositing the reflective material at that angle. Description of the Drawings

[0010] To be able to understand the above features of the present case in detail, reference may be made to the embodiments to describe more specifically the present case briefly outlined above, and the drawings illustrate some of the embodiments. However, it should be noted that the drawings only illustrate exemplary embodiments and should not be considered to limit the scope of the present case, and other equivalent embodiments may be recognized.

[0011] Figure 1A It is a cross-sectional schematic view of a pixel having a first microlens arrangement according to an embodiment.

[0012] Figure 1B It is a cross-sectional schematic view of a pixel having a second microlens arrangement according to an embodiment.

[0013] Figure 2 It is a flowchart of a method for forming a reflective material on a sub-pixel isolation structure according to an embodiment.

[0014] Figures 3A to 3E It is a cross-sectional schematic view of a backplane during method 200 according to an embodiment.

[0015] Figure 4 It is a flowchart of method 400 for forming sub-pixels according to an embodiment.

[0016] Figures 5A to 5C It is a cross-sectional schematic view of a backplane during method 400 according to an embodiment.

[0017] Figure 6 It is a flowchart of method 400 for forming sub-pixels according to an embodiment.

[0018] Figures 7A to 7C It is a cross-sectional schematic view of a backplane during method 600 according to an embodiment.

[0019] Figure 8A and Figure 8B It is a cross-sectional view of a backplane during the formation of a first microlens arrangement according to an embodiment.

[0020] Figure 8C It is a cross-sectional view of a backplane during the formation of a second microlens arrangement according to an embodiment.

[0021] For ease of understanding, the same reference numerals have been used, where possible, to denote common identical elements in the figures. It is contemplated that elements and features of one embodiment may be beneficially present in other embodiments without further recitation. Detailed Description

[0022] Embodiments of the present case generally relate to LED pixels and methods of manufacturing LED pixels. The components include: a backplane; at least three LEDs disposed on the backplane; a sub-pixel isolation (SI) structure configured to define wells for at least three sub-pixels, a reflective material disposed on sidewalls and top surfaces of the SI structure, at least three of the sub-pixels having a color conversion material disposed in the wells; a packaging layer disposed over the sub-pixel isolation structure and the sub-pixels; a filter layer disposed over the packaging layer; and microlenses disposed over the filter layer and over each of the sub-pixel wells.

[0023] Figure 1A is a cross-sectional schematic view of a pixel 100 having a first microlens arrangement 101A. Figure 1B is a cross-sectional schematic 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 may be disposed between the LEDs 104. The LEDs 104 are integrated with a bottom circuit system such that each LED 104 can be individually addressed. For example, the circuit system of the backplane 102 may include a TFT active matrix array (each LED has a thin film transistor and a storage capacitor (not shown)), row address and column address lines, row and column drivers to drive the LEDs 104. Alternatively, the LEDs 104 may be driven by a passive matrix in the bottom circuit system. 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 may be white light. The LEDs 104 may be micro-LEDs.

[0024] A passivation layer 108 is disposed above the LEDs 104 and, in some embodiments, directly on the LEDs 104. A sub-pixel isolation (SI) structure 110 is disposed above the passivation layer 108 and, in some embodiments (such as Figure 1B shown), on the passivation layer 108. Adjacent sub-pixel isolation structures define respective wells 113 for at least three sub-pixels 112. The sub-pixels 112 include: a red sub-pixel 112a having a red conversion material disposed in the well 113 of the red sub-pixel 112a; a green sub-pixel 112b having a green conversion material disposed in the well 113 of the green sub-pixel 112b; and a blue sub-pixel 112c having a blue conversion material disposed in the well 113 of the blue sub-pixel 112c. When the LED 104a of the red sub-pixel 112a is turned on, the red conversion material converts the light emitted from the LED 104a into red light. When the LED 104c of the blue sub-pixel 112c is turned on, the blue conversion material converts the light emitted from the LED 104c into blue light. In one embodiment, the pixel 100 includes a fourth sub-pixel 112d. As Figure 1A shown, the fourth sub-pixel 112d does not include a color conversion material, that is, there is no color conversion layer. As Figure 1B shown, the fourth sub-pixel 112d includes a sacrificial material 115. In other embodiments, at least three sub-pixels 112 include the same color conversion material. The fourth sub-pixel 112d can then be filled with a color conversion material.

[0025] The sub-pixel isolation structure 110 includes a photoresist material, such as an epoxy-based resist. The photoresist material is a negative photoresist. The exposed surface 116 (i.e., the sidewalls and the top surface) of the sub-pixel isolation structure 110 has a reflective material 118 disposed thereon. The reflective material 118 on the exposed surface 116 provides reflection of the emitted light to contain the converted light into the corresponding sub-pixel, thereby collimating the light into the display. The reflective material 118 includes but is not limited to aluminum, silver, combinations thereof, or the like. In one embodiment, as Figure 1A shown, an anti-reflective material 120 is disposed between the sub-pixel isolation structure 110 and the passivation layer 108. The anti-reflective material 120 may include chromium nitride (CrN).

[0026] An encapsulation layer 122 is disposed over the sub-pixel isolation structure 110 and the sub-pixels 112. As Figure 1A shown, the first microlens arrangement 101A includes a filter layer 124 disposed over the encapsulation layer 122. A second passivation layer 126 is disposed on the filter layer 124, and microlenses 128 are disposed on the second passivation layer 126 and over each of the wells 113 of the sub-pixels 112. The filter layer 124 is selective for photons of certain wavelengths. In some embodiments, the 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 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. As Figure 1B shown, the second microlens arrangement 101B includes microlenses 128 disposed on the encapsulation layer 122 and over each of the wells 113 of the sub-pixels 112. The 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.

[0027] Figure 2 is a flowchart of a method 200 for forming the reflective material 118 on the sub-pixel isolation structure 110. Figures 3A to 3E is a cross-sectional schematic view of the backplane 102 during the method 200. In operation 201, as Figure 3A and Figure 3B shown, a resist layer 301 is patterned to form the sub-pixel isolation structure 110. The resist layer may be patterned by a photolithography process. The sub-pixel isolation structure 110 may have a width 303 of about 1 μm to about 4 μm, such as 2 μm to 3 μm. The sub-pixel isolation structure 110 may have a pitch 304 of about 2 μm to about 6 μm, such as about 4 μm. The sub-pixel isolation structure 110 may have a thickness 305 of about 2 μm to about 12 μm, such as 5 μm to 10 μm. In some embodiments, as Figure 3EAs shown, an anti-reflection material 120 is disposed between the sub-pixel isolation structure 110 and the passivation layer 108. When the photoresist layer 301 is patterned, the remaining portion of the anti-reflection material 120 disposed between the sub-pixel isolation structures 110 is removed. The anti-reflection material 120 helps to define the sub-pixel isolation structure 110 during photoresist patterning. In operation 202, as Figure 3C shown, the 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. On the exposed surface 116, the reflective material 118 is deposited on one sidewall and the top surface of the sub-pixel isolation structure 110. In operation 203, the backplane 102 is rotated by at least 90 degrees, and the reflective material 118 is deposited at an angle α. For the four side sub-pixel isolation structures 110, the backplane 102 is rotated by 90 degrees, and the reflective material 118 is deposited at least three additional times. Operation 203 is repeated twice such that the reflective material 118 is deposited on the four sidewalls and the top surface of the sub-pixel isolation structure 110, as Figure 3D and Figure 3E shown. For the circular well 113, the backplane 102 is rotated 360 degrees, and the reflective material 118 is deposited.

[0028] Figure 4 FIG. is a flowchart of a method 400 for forming the sub-pixel 112. Figures 5A to 5C FIG. is a cross-sectional schematic view of the backplane 102 during the method 400 for forming the sub-pixel 112. In operation 401, as Figure 5A shown, a first color conversion material is deposited in each of the wells 113 of the sub-pixel 112. Operation 401 is performed after method 200. In one embodiment, the first color conversion material is a red conversion material for the red sub-pixel 112a. In operation 402, as Figure 5B shown, the first color conversion material of the first sub-pixel is cured, and the first color conversion material in the wells of the remaining sub-pixels is removed. The first sub-pixel may correspond to the red sub-pixel 112a. In operation 403, as Figure 5C shown, operations 401 and 402 are repeated for the second color conversion material of the second sub-pixel and the third color conversion material of the third sub-pixel. The first, second, and third conversion materials are cured by laser curing and removed by cleaning. In one embodiment, the second color conversion material is a green conversion material for the green sub-pixel 112b, and the third color conversion material is a blue conversion material for the blue sub-pixel 112c. Operations 401 and 402 may be repeated for the fourth sub-pixel 112d.

[0029] Figure 6 FIG. is a flowchart of a method 600 for forming the sub-pixel 112. Figures 7A to 7CIt is a cross-sectional schematic view of the backplane 102 during the method 600 for forming the sub-pixels 112. In operation 601, the sacrificial material 115 is deposited in each of the wells 113 of the sub-pixels 112. Operation 601 is performed after method 200. In operation 602, as Figure 7A and Figure 7B shown, the sacrificial material 115 in the well of the first sub-pixel is removed. The sacrificial material 115 is a positive photoresist. The sacrificial material 115 can be deposited by spin coating. When developing the sacrificial material 115, the sacrificial material 115 can be removed, so that the well of the first sub-pixel is exposed to the light passing through the opening of the mask 702. In operation 603, as Figure 7C shown, the first color conversion material is deposited in the well of the first sub-pixel and cured. In one embodiment, the first color conversion material is a red conversion material, and the first sub-pixel is the red sub-pixel 112a. In operation 604, as Figure 5C shown, operations 602 and 603 are repeated for the second and third sub-pixels. The first, second, and third conversion materials are cured by laser curing. In one embodiment, the second color conversion material is a green conversion material for the green sub-pixel 112b, and the third color conversion material is a blue conversion material for the blue sub-pixel 112c. Operations 602 and 603 can be repeated for the fourth sub-pixel 112d.

[0030] To form the first microlens arrangement 101A of the pixel 100, an encapsulation layer 122 is disposed above the sub-pixel isolation structure 110 and the sub-pixels 112. A filter layer 124 is disposed above the encapsulation layer 122. A second passivation layer 126 is disposed on the filter layer 124. The filter layer 124 is selective for photons of certain wavelengths. In some embodiments, the filter layer 124 is a UV blocking layer, a UV reflecting layer, a blue light blocking layer, a blue light reflecting layer, or a combination thereof. The filter layer 124 can include a UV blocking material, a UV reflecting material, a blue light blocking material, a blue light reflecting material, or a combination thereof. Figure 8A and Figure 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, the resist 802 is patterned such that the resist 802 remains above each of the wells 113 of the sub-pixels 112, as Figure 8A shown. The resist 802 is gray-scale patterned or undergoes a thermal reflow process to form the microlens 128, as Figure 1A shown. In another embodiment, as Figure 8B shown, the resist 802 is embossed (e.g., by nanoimprint lithography) to form the microlens 128, as Figure 1A shown.

[0031] Figure 8CIt 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 above the sub-pixel isolation structure 110 and the sub-pixel 112. A resist 804 is disposed on the encapsulation layer 122. The resist 804 is embossed to form microlenses 128, as Figure 1B shown. The resist 804 includes a light filtering material. In some embodiments, the light filtering 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 above the microlenses 128.

[0032] Although the above relates to embodiments of the present case, other and additional embodiments of the present case may be designed without departing from the basic scope, and the scope is determined by the claims below.

Claims

1. A component, the component comprising: A backplane; An LED, the LED being disposed above the backplane; A sub-pixel isolation (SI) structure, the sub-pixel isolation (SI) structure being disposed above the LED, defining wells of sub-pixels, each well including a corresponding LED between adjacent SI structures, the sub-pixels having different color conversion materials disposed in the wells; And A microlens, the microlens being disposed above each of the wells of the sub-pixels, the microlens including a light filtering material.

2. The component according to claim 1, wherein the filter layer is a UV blocking layer, a UV reflecting layer, a blue light blocking layer or a blue light reflecting layer.

3. The component according to claim 1, wherein an anti-reflection material is provided between the SI structure and the backplane.

4. The component according to claim 1, wherein a packaging layer is provided under the microlens and above the SI structure and the sub-pixel.

5. The component according to claim 1, wherein a second passivation layer is provided on the microlens.

6. The component according to claim 1, wherein a reflective material is provided on the sidewall and the top surface of the SI structure.

7. The component according to claim 1, the component further comprising four sub-pixels, wherein the corresponding well of the fourth sub-pixel comprises a sacrificial material or a color conversion material.

8. A component, the component comprising: A backplane; An LED, the LED being disposed above the backplane; A sub-pixel isolation (SI) structure, the sub-pixel isolation (SI) structure being disposed above the LED, defining wells of sub-pixels, each well including a corresponding LED between adjacent SI structures, the sub-pixels having different color conversion materials disposed in the wells; An encapsulation layer, the encapsulation layer being located above the SI structure and the sub-pixels; A light filtering layer, the light filtering layer being disposed above the encapsulation layer; A second passivation layer, the second passivation layer being disposed on the light filtering layer; And A microlens, the microlens being disposed above the light filtering layer and above each of the wells of the sub-pixels.

9. The component according to claim 8, wherein the filter layer is a UV blocking layer, a UV reflecting layer, a blue light blocking layer or a blue light reflecting layer.

10. The component according to claim 8, wherein an anti-reflection material is provided between the SI structure and the backplane.

11. The component according to claim 8, wherein at least three of the sub-pixels have different color conversion materials.

12. The component according to claim 8, the component further comprising four sub-pixels, wherein the corresponding well of the fourth sub-pixel comprises a sacrificial material or a color conversion material.

13. An element, the element comprising: a backplane; an LED disposed above the backplane; a sub-pixel isolation (SI) structure disposed above the LED to define wells of sub-pixels, each well including a corresponding LED between adjacent SI structures, the sub-pixels having different color conversion materials disposed in the wells, wherein the element is made by a process comprising: Disposing a filter layer above the wells and the SI structure; and Performing a nanoimprint lithography process to form microlenses from the filter layer above the sub-pixels.

14. The element of claim 13, wherein a packaging layer is disposed below the microlenses and above the SI structure and the sub-pixels.

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

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

17. The element of claim 13, the element further comprising four sub-pixels, wherein the corresponding well of the fourth sub-pixel includes a sacrificial material or a color conversion material.

18. An element, the element comprising: a backplane; an LED disposed above the backplane; a sub-pixel isolation (SI) structure disposed above the LED to define wells of sub-pixels, each well including a corresponding LED between adjacent SI structures, the sub-pixels having different color conversion materials disposed in the wells; a packaging layer located above the SI structure and the sub-pixels; a filter layer disposed above the packaging layer; and a second passivation layer disposed on the filter layer, wherein the element is made by a process comprising: Disposing a resist on the second passivation layer; Pattern the resist to form a portion above the sub-pixels; And Perform one of a grayscale process, a thermal reflow process, or a nanoimprint lithography process to form a microlens from the portion of the resist above the sub-pixels.

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

20. The element of claim 19, the element further comprising four sub-pixels, wherein the corresponding well of the fourth sub-pixel includes a sacrificial material or a color conversion material.

21. A method, the method comprising: Deposit reflective material at an angle above a backplane, with LEDs disposed above the backplane and sub-pixel isolation (SI) structures disposed above the LEDs defining wells for the sub-pixels, each well including a corresponding LED between adjacent SI structures, and depositing the reflective material on a sidewall and a top surface of the SI structure; and Rotate the backplane by at least 90 degrees and deposit the reflective material at the angle.

22. The method of claim 21, the method further comprising: Deposit a first color conversion material in a first well of a first sub-pixel, a second well of a second sub-pixel, and a third well of a third sub-pixel; Cure the first color conversion material in the first well; Remove the first color conversion material in the second well and the third well; Deposit a second color conversion material in the second well of the second sub-pixel and the third well of the third sub-pixel; Cure the second color conversion material in the second well; Remove the second color conversion material in the third well; Deposit a third color conversion material in the third well of the third sub-pixel; and Cure the third color conversion material in the third well.

23. The method of claim 21, the method further comprising: Deposit a sacrificial material in a first well of a first sub-pixel, a second well of a second sub-pixel, and a third well of a third sub-pixel; Expose the sacrificial material in the first well to light passing through an opening in a mask; Remove the exposed sacrificial material in the first well; Deposit a first color conversion material in the first well; Expose the sacrificial material in the second well to light passing through the opening of the mask; Deposit a second color conversion material in the second well; Expose the sacrificial material in the third well to light passing through the opening of the mask; And Deposit a third color conversion material in the third well.

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

25. The method of claim 21, the method further comprising: Dispose a packaging layer above the SI structure and the sub-pixels; Dispose a filter layer above the packaging layer; Dispose a second passivation layer on the filter layer; Set a resist on the second passivation layer; Pattern the resist to form a portion above the sub-pixels; And Perform one of a grayscale process, a thermal reflow process, or a nanoimprint lithography process to form a microlens from the portion of the resist above the sub-pixels.

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