WO2025072161A1

WO2025072161A1 - Formulating and patterning quantum dot color converters

Info

Publication number: WO2025072161A1
Application number: PCT/US2024/048156
Authority: WO
Inventors: Kulandaivelu SIVANANDAN; Sivapackia Ganapathiappan; Da He; Zhiyong Li
Original assignee: Applied Materials Inc
Current assignee: Applied Materials Inc
Priority date: 2023-09-26
Filing date: 2024-09-24
Publication date: 2025-04-03
Anticipated expiration: 2026-03-26
Also published as: TW202525102A

Abstract

Embodiments of the present disclosure generally relate to techniques for fabricating quantum dot color converters and micro-LED devices. Specifically, embodiments include devices having subpixels including color conversion materials, where the color conversion material may be composed of one or more quantum dots. The quantum dots and methods of fabricating quantum dot color converters can be used in a multitude of different light-emitting diode (LED) devices. In one embodiment, a method of fabricating a light-emitting diode (LED) device is provided. The method includes disposing a first quantum dot material over a plurality of subpixels and a first surface of a plurality of subpixel isolation structures, and exposing a first portion of the first quantum dot material to a light source to deactivate the first portion of the first quantum dot material. A second portion of the first quantum dot material is not deactivated.

Description

FORMULATING AND PATTERNING QUANTUM DOT COLOR CONVERTERS

BACKGROUND

Field

[0001] Embodiments of the present disclosure generally relate to techniques for fabricating quantum dots. Specifically, embodiments include techniques for fabricating quantum dot color converters and micro-LED devices.

Description of the Related Art

[0002] A light emitting diode (LED) panel uses an array of LEDs, with individual LEDs providing the individually controllable pixel elements. Such LED panels can be used for computers, touch panel devices, personal digital assistants (PDAs), cell phones, television monitors, and the like. An LED panel that uses micron-scale LEDs based on lll-V semiconductor technology (also called micro-LEDs) would have a variety of advantages as compared to organic light emitting diodes (OLEDs), e.g., higher energy efficiency, brightness, and lifetime, as well as fewer material layers in the display stack, which can simplify manufacturing. However, there are challenges to fabricating micro-LED panels that implement color conversion materials, for example, due to the instability of many color conversion materials.

[0003] Accordingly, improved techniques for fabricating color conversion materials are needed.

SUMMARY

[0004] In one embodiment, a method of fabricating a light-emitting diode (LED) device is provided. The method includes disposing a first quantum dot material over a plurality of subpixels and a first surface of a plurality of subpixel isolation structures, and exposing a first portion of the first quantum dot material to a light source to deactivate the first portion of the first quantum dot material. A second portion of the first quantum dot material is not deactivated. [0005] In one embodiment, a method of fabricating a micro light emitting diode (micro-LED) device is provided. The method includes disposing a first quantum dot material over a plurality of micro-LED in a plurality of subpixels and a first surface of a plurality of subpixel isolation structures, and exposing a first portion of the first quantum dot material to a light source to deactivate the first portion of the first quantum dot material. A second portion of the first quantum dot material is not deactivated over a first micro-LED included in a first subpixel.

[0006] In one embodiment, a micro light emitting diode (micro-LED) device is provided. The device includes a backplane, a plurality of micro-LEDs disposed above the backplane, and a plurality of subpixel isolation structures, the plurality of subpixel isolation structures and the plurality of micro-LEDs defining a plurality of subpixels. The plurality of subpixels includes a first subpixel with a red conversion material disposed in the first subpixel, a second subpixel with a green conversion material disposed in the second subpixel, and a third subpixel with a blue quantum dot material disposed in the third subpixel. A photo-bleached blue quantum dot material is disposed over a first surface of the subpixel isolation structures, the red conversion material, and the green conversion material.

BRIEF DESCRIPTION OF THE DRAWINGS

[0007] So that the manner in which the above recited features of the present disclosure can be understood in detail, a more particular description of the disclosure, briefly summarized above, may be had by reference to embodiments, some of which are illustrated in the appended drawings. It is to be noted, however, that the appended drawings illustrate only exemplary embodiments and are therefore not to be considered limiting of its scope, may admit to other equally effective embodiments.

[0008] Figure 1 is a schematic, cross-sectional view of a micro-LED pixel, according to some embodiments.

[0009] Figure 2 is a flow diagram of a method for forming a micro-LED pixel according to some embodiments. [0010] Figures 3A-3D are schematic, cross-sectional views of a micro-LED structure, according to some embodiments.

[0011] To facilitate understanding, identical reference numerals have been used, where possible, to designate identical elements that are common to the figures. It is contemplated that elements and features of one embodiment may be beneficially incorporated in other embodiments without further recitation.

DETAILED DESCRIPTION

[0012] Embodiments of the present disclosure generally relate to techniques for fabricating quantum dot color converters and micro-LED devices. Specifically, embodiments include a device having a backplane, one or more (e.g., three or more) micro-LEDs disposed on the backplane, and one or more subpixel isolation (SI) structures defining wells of the subpixels (e.g., three subpixels). The subpixels include a color conversion material disposed in the wells, where the color conversion material may be composed of one or more quantum dots. The quantum dots and methods of fabricating quantum dot color converters can be used in a multitude of different light-emitting diode (LED) devices.

[0013] Figure 1 is a schematic, cross-sectional view of a micro light emitting diode (micro-LED) pixel 100. The micro-LED pixel 100 includes a backplane 101. The backplane 101 includes a backplane surface 101a. Micro-LEDs 109 are disposed over the backplane 101 on the backplane surface 101a. The backplane 101 and micro-LEDs 109 include electrodes (not shown) that connect to power the micro-LEDs 109.

[0014] The micro-LED pixel 100 includes subpixel isolation (SI) structures 113 disposed on the backplane surface 101a between the micro-LEDs 109. The SI structures 113 have a UV reflectivity of greater than 90%. The optical density of the SI structures 113 provides for color isolation between each of the micro-LEDs 109. The SI structures 113 define a plurality of subpixels 112. The SI structures 113 and the micro-LEDs 109 define a plurality of wells 127 of the subpixels 112. The sidewalls and top surface of each of the SI structures 113 have a reflection material 118 disposed thereon. The reflection material 118 on the exposed surfaces provide for reflection of the emitted light to contain the converted light to the respective subpixel in order to collimate the light to the display. The reflection material 118 includes, but is not limited to, aluminum, silver, combinations thereof, or the like.

[0015] The wells 127 are filled with color conversion materials 115. The color conversion materials 115 may include quantum dot materials, phosphor materials, or combinations thereof. As shown in Figure 1 , the well 127 of a first subpixel 112a is filled with a material 130. In some embodiments, the material 130 is a quantum dot material (e.g., the quantum dot material 120). The quantum dot material 120 acts as a first color conversion material 115a. In some embodiments, the quantum dot material 120 is a blue quantum dot material. In other embodiments, the quantum dot material 120 is a green quantum dot material or a red quantum dot material. Alternatively, the well 127 of the first subpixel 112a is filled with a material 130 that is a sacrificial material. In some embodiments, the well 127 of the second subpixel 112b is color- conversion-material-less (e.g., the second subpixel 112b is not filled with a color conversion material 115). The well 127 of a third subpixel 112c is filled with a third color conversion material 115c. In some embodiments, the third color conversion material 115c is a green conversion material. The well 127 of a fourth subpixel 112d is filled with a fourth color conversion material 115d. In some embodiments, the fourth color conversion material 115d is a red conversion material. In some embodiments, when a micro-LED 109 of the first subpixel 112a is turned on, the blue quantum material will convert the light emitted from micro-LED 109 into blue light. In some embodiments, when a micro-LED 109 of the third subpixel 112c is turned on, the green conversion material will convert the light emitted from micro-LED 109 into green light. In some embodiments, the green color conversion material is green quantum dots. In some embodiments, when a micro-LED 109 of the fourth subpixel 112d is turned on, the red conversion material will convert the light emitted from micro-LED 109 into red light. In some embodiments, the red color conversion material is red quantum dots. [0016] In various embodiments, the quantum dot material 120 is formed from a quantum dot solution. In various embodiments, the solution behaves as a positive-tone resist. The solution includes between 5% and 30% concentration by weight of quantum dots. In some embodiments, the solution includes toluene. The solution further includes an ultraviolet-curable photoresist material, such as an epoxy-based photoresist, an acrylate-based photoresist, an azide-based photoresist, or a similar photoresist. In some embodiments, the ultraviolet-curable photoresist material includes 1 ,6- hexanediol diacrylate, Trimethylolpropane triacrylate, 1 ,9-nonanediol diacrylate etc. in combination with a small amount of initiator (between 0.5-5%) such as Irgacure 2959, Irgacure 379, TPO (diphenyl(2,4,6-trimethylbenzoyl)phosphine oxide), benzoyl peroxide or a similar material. In some embodiments, the epoxy-based photoresist includes SU-8 2005, SU-8 2000.5, and SU-8 3005. The azide-based photoresist includes a combination of polystyrene, polyhydroxystyrene, PMMA and/or poly(vinyl phenol) with an azide such as 3,3'-diazidodiphenylsulfone (I), 4-azidochalcone (II), 3-(p-azidostyryl)-5,5- dimethyl-2-cyclohexen-1-one (III), 3-(4-(p-azidophenyl)-1 ,3-butadienyl)-5,5- dimethyl-2-cyclohexen-1-one (IV), and 2-(p-azidostyryl)-4- benzylideneoxazolone (V) and/or a similar material. The quantum dot material 120 and the photo-bleached quantum dot material 121 may have a thickness of 0.5 pm to 10 pm. The quantum dot material 120 has an optical density ranging from 0.5 to 6, such as 0.5 to 3, such as 0.8 to 3. The optical density of the quantum dot material 120 generally increases with the thickness of quantum dot material 120 and the concentration of quantum dots in the solution.

[0017] As shown in Figure 1 , a photo-bleached quantum dot material 121 is disposed on a first surface 114 of the SI structures 113 and the reflection material 118. The photo-bleached quantum dot material 121 is also disposed on the third color conversion material 115c and fourth color conversion material 115d. The photo-bleached quantum dot material 121 is substantially transparent and, thus, does not interfere with the light emitted from the third subpixel 112c or the fourth subpixel 112d. The photo-bleached quantum dot material 121 is disposed on the material 130 disposed in the first subpixel 112a. For example, the photo-bleached quantum dot material 121 is disposed over a color conversion material 115 or a sacrificial material disposed in the first subpixel 112a. The photo-bleached quantum dot material 121 is disposed in the second subpixel 112b. The photo-bleached quantum dot material 121 is disposed over the micro-LED 109 disposed in the second subpixel 112b. In some embodiments, an encapsulation layer 122 is disposed over the SI structures 113 and the subpixels 112. The encapsulation layer 122 conforms to the shape of the micro-LED pixel 100 and is disposed over the photobleached quantum dot material 121.

[0018] Figure 2 is a flow diagram of a method 200 for forming a micro-LED pixel 100 according to embodiments (e.g., such as embodiments shown in Figures 3A-3D). Figures 3A-3D are schematic, cross-sectional views of a micro-LED structure 300 during the method 200. At operation 201 , as shown in Figure 3A, a micro-LED structure 300 is provided. The micro-LED structure 300 includes the backplane 101 , the plurality of micro-LEDs 109, and the plurality of SI structures 113. The micro-LEDs 109 are disposed above the backplane 101 on the backplane surface 101a. The SI structures 113 and the micro-LEDs 109 define the subpixels 112. In some embodiments, the well 127 of a first subpixel 112a is filled with a material 130. In some embodiments, the material 130 is a first color conversion material 115a. In some embodiments, the first color conversion material 115a is a blue quantum dot material. In other embodiments, the color conversion material 115 is a green quantum dot material or a red quantum dot material. Alternatively, the well 127 of the first subpixel 112a is filled with a material 130 that is a sacrificial material. In some embodiments, the well 127 of the second subpixel 112b is color-conversion- material-less (e.g., the second subpixel 112b is not filled with a color conversion material 115). In other embodiments, the second subpixel 112b includes the first color conversion material 115a. In some embodiments, the first color conversion material 115a is a blue quantum dot material. In other embodiments, the color conversion material 115 is a green quantum dot material or a red quantum dot material. In some embodiments, the third subpixel 112c is filled with the third color conversion material 115c and the fourth subpixel 112d is filled with the fourth color conversion material 115d prior to operation 201 . In other embodiments, the third subpixel 112c and the fourth subpixel 112d are empty similar to the second subpixel 112b.

[0019] At operation 203, as shown in Figure 3B, a quantum dot material 120 is disposed on the micro-LED structure 300. The quantum dot material 120 is disposed over the subpixels 112 and a first surface 114 of the SI structures 113. The disposing may include spin-coating, prebaking, and curing the quantum dot material 120. For example, the quantum dot material 120 is first spin-coated on the micro-LED structure 300. The spin-coating achieves a uniform thickness (e.g., 1-10 pm) of the quantum dot material 120. The spin-coating is performed in an inert environment. In some embodiments, the spin-coating is performed in a glovebox. In some embodiments, the spin-coating is performed under a vacuum pressure.

[0020] Next, in various embodiments, the quantum dot material 120 is prebaked. The pre-baking process is performed on a hotplate at 100° C for 3 minutes. Like the spin-coating, the pre-baking is performed in an inert environment. In some embodiments, the pre-baking is performed in a glovebox. In some embodiments, the pre-baking is performed under a vacuum pressure. The inert environment is needed to protect the emissive properties of the quantum dot material 120. In some embodiments, the quantum dot material 120 is formed with a photoresist that does not contain a solvent. In such embodiments no pre-baking process is performed.

[0021] Finally, the quantum dot material 120 is blanket cured using a broad band UV light. The micro-LED structure 300 is packed into an argon-filled bag after the pre-bake. The micro-LED structure 300 is exposed to a broad band UV light. As a result of the disposition, the quantum dot material 120 is disposed across the micro-LED structure 300. For example, a first portion 320 of the quantum dot material 120 is disposed in the first subpixel 112a, the third subpixel 112c, the fourth subpixel 112d, and disposed over the first surface 114 of the SI structures 113 and the reflective material 118. A second portion 321 of the quantum dot material 120 is disposed in the well 127 of the second subpixel 112b. [0022] At operation 205, as shown in Figures 3C-3D, the first portion 320 of the quantum dot material 120 is deactivated. In various embodiments, the first portion 320 of the quantum dot material 120 is exposed to a light source to deactivate the first portion 320 of the quantum dot material 120. The first portion 320 is deactivated via photo-bleaching. The second portion 321 of the quantum dot material 120 is not deactivated. In Figure 3C, photo-bleaching of the first portion 320 is performed by photolithography with a photomask 305. In Figure 3D, the photo-bleaching is performed by patterning with a laser 310. After operation 205, in certain embodiments, an encapsulation layer 122 is deposited over the quantum dot material 120 and the subpixels 112. As shown in Figure 1 , the encapsulation layer 122 conforms to the shape of the subpixels 112.

[0023] Figure 3C illustrates the patterning of the quantum dot material 120 using a photomask 305. The micro-LED structure 300 is positioned below the photomask 305. The micro-LED structure 300 is exposed to an ambient air environment including oxygen gas (e.g., O2). The micro-LED structure 300 is exposed to a UV light through the photomask 305. The quantum dot material 120 acts as a positive photoresist. The second portion 321 of the quantum dot material 120 is covered by the photomask 305 and is not affected by the UV light or ambient air. By contrast, the first portion 320 of the quantum dot material 120 that is exposed to the UV light is quenched. The first portion 320 that is quenched include the quantum dot material 120 disposed on the first surface 114 of the SI structures 113 and disposed in the second subpixel 112b and the third subpixel 112c. The second portion 321 of the quantum dot material 120 that is not quenched includes the quantum dot material 120 disposed in the first sub-pixel 112a.

[0024] The quenching of the first portion 320 photo-bleaches the first portion 320 to form the photo-bleached quantum dot material 121 , as shown in Figure 1. As described above, the first portion 320 is deactivated by the photobleaching. In some embodiments, the UV light and exposure to oxygen gas may oxidize the quantum dot material 120. As a result, the first portion 320 is inert and without emissive properties. Consequently, the first portion 320 cannot emit visible light and does not interfere with other color conversion materials 115 in the other subpixels 112.

[0025] Figure 3D shows the patterning of the quantum dot material 120 using a laser 310. The micro-LED structure 300 is positioned below the laser 310. The micro-LED structure 300 is exposed to an ambient air environment such that oxygen gas (e.g., O2) is present. The micro-LED structure 300 is selectively patterned by the laser 310. As described above, the quantum dot material 120 acts as a positive photoresist. The first portion 320 of the quantum dot material 120 is patterned by the laser 310. The second portion 321 of the quantum dot material 120 is not patterned by the laser 310. The second portion 321 is not affected by the ambient air. The first portion 320 of the quantum dot material 120 patterned by the laser is quenched. The first portion 320 quenched include the quantum dot material 120 disposed on the first surface 114 of the SI structures 113 and disposed in the second subpixel 112b and the third subpixel 112c. The second portion 321 of the quantum dot material 120 not quenched include the quantum dot material 120 disposed in the second subpixel 112b.

[0026] As described above, the quenching of the first portion 320 photobleaches the first portion 320. The first portion 320 becomes the photobleached quantum dot material 121 shown in Figure 1. The first portion 320 are deactivated by the photo-bleaching. In some embodiments, the laser 310 and exposure to oxygen gas may oxidize the quantum dot material 120. As described above, the first portion 320 does not have emissive properties and do not with other color conversion materials 115 in the other subpixels 112.

[0027] Figures 1 , and 3A-3D show the quantum dot material 120 being disposed and deactivated after the material 130, the third color conversion material 115c and the fourth color conversion material 115d are present in the micro-LED structure 300 as an example. However, in some embodiments, the quantum dot material 120 is disposed and deactivated before the third color conversion material 115c and/or the fourth color conversion material 115d are present in the micro-LED structure 300. In some embodiments, the third color conversion material 115c and/or the fourth color conversion material 115d include quantum dot materials and are disposed and deactivated in a manner similar to or the same as the quantum dot material 120. A first portion of the second quantum dot material is deactivated, and a second portion of the second quantum dot material is not deactivated. A first portion of the third quantum dot material is deactivated, and a second portion of the third quantum dot material is not deactivated. In other embodiments, the third color conversion material 115c and the fourth color conversion material 115d are disposed on the micro-LED structure 300 using different methods.

[0028] In summary, methods of fabricating micro-LED pixels with quantum dot color converters are provided. Benefits of the methods include being able to pattern quantum dots that are unstable in ambient conditions. The disclosed techniques reduce the time required to fabricate micro-LED devices and/or reduce fabrication costs. By contrast, traditional methods and chemistries of photoresists for blue quantum dots are difficult and require inert atmospheres. Additionally, the disclosed techniques can be performed in ambient environments.

[0029] While the foregoing is directed to embodiments of the present disclosure, other and further embodiments of the disclosure may be devised without departing from the basic scope thereof, and the scope thereof is determined by the claims that follow.

Claims

What is claimed is:

1 . A method of fabricating a light-emitting diode (LED) device, comprising: disposing a first quantum dot material over a plurality of subpixels and a first surface of a plurality of subpixel isolation structures; and exposing a first portion of the first quantum dot material to a light source to deactivate the first portion of the first quantum dot material, wherein a second portion of the first quantum dot material is not deactivated.

2. The method of claim 1 , wherein the first quantum dot material comprises at least one of blue quantum dots, green quantum dots, or red quantum dots.

3. The method of claim 1 , wherein disposing the first quantum dot material comprises: spin-coating the first quantum dot material; and curing the first quantum dot material using a broad band UV light.

4. The method of claim 1 , wherein exposing the first portion of the first quantum dot material to the light source is performed while the first quantum dot material is exposed to oxygen gas.

5. The method of claim 1 , wherein, prior to disposing the first quantum dot material, a first color conversion material is disposed in a first subpixel of the plurality of subpixels, and a second color conversion material is disposed in a second subpixel of the plurality of subpixels.

6. The method of claim 1 , wherein the light source is a laser, and exposing the first portion with the laser photo-bleaches the first portion of the first quantum dot material.

7. The method of claim 1 , wherein the light source comprises a UV light, and the UV light is exposed to the first portion of the first quantum dot material through a photomask.

8. The method of claim 1 , further comprising: disposing a second quantum dot material over the plurality of subpixels and the first surface of the subpixel isolation structures; exposing a first portion of the second quantum dot material to a light source to deactivate the first portion of the second quantum dot material, wherein a second portion of the second quantum dot material is not deactivated; disposing a third quantum dot material over the plurality of subpixels and the first surface of the subpixel isolation structures; and exposing a first portion of the third quantum dot material to a light source to deactivate the first portion of the third quantum dot material, wherein a second portion of the third quantum dot material is not deactivated.

9. A method of fabricating a micro light emitting diode (micro-LED) device, comprising: disposing a first quantum dot material over a plurality of micro-LED in a plurality of subpixels and a first surface of a plurality of subpixel isolation structures; and exposing a first portion of the first quantum dot material to a light source to deactivate the first portion of the first quantum dot material, wherein a second portion of the first quantum dot material is not deactivated over a first micro- LED included in a first subpixel.

10. The method of claim 9, wherein the first quantum dot material comprises blue quantum dots.

11 . The method of claim 9, wherein disposing the first quantum dot material comprises: spin-coating the first quantum dot material; and curing the first quantum dot material using a broad band UV light.

12. The method of claim 9, wherein exposing the first portion of the first quantum dot material to the light source is performed while the first quantum dot material is exposed to oxygen gas.

13. The method of claim 9, wherein a first color conversion material is disposed in a second subpixel and a second color conversion material is disposed in a third subpixel prior to disposing the first quantum dot material.

14. The method of claim 9, wherein the light source is a laser, and exposing the first portion with the laser photo-bleaches the first portion of the first quantum dot material.

15. The method of claim 9, wherein the light source is a UV light, and the UV light is exposed to the first portion of the first quantum dot material through a photomask.

16. The method of claim 9, further comprising: disposing a second quantum dot material over the subpixels and a first surface of the subpixel isolation structures; exposing a first portion of the second quantum dot material to a light source to deactivate the first portion of the second quantum dot material, wherein a second portion of the second quantum dot material is not deactivated; disposing a third quantum dot material over the subpixels and a first surface of the subpixel isolation structures; and exposing a first portion of the third quantum dot material to a light source to deactivate the first portion of the second quantum dot material, wherein a second portion of the third quantum dot material is not deactivated.

17. A micro light emitting diode (micro-LED) device, comprising: a backplane; a plurality of micro-LEDs disposed above the backplane; a plurality of subpixel isolation structures, the plurality of subpixel isolation structures and the plurality of micro-LEDs defining a plurality of subpixels; a first subpixel included in the plurality of subpixels, a red conversion material disposed in the first subpixel; a second subpixel included in the plurality of subpixels, a green conversion material disposed in the second subpixel; a third subpixel included in the plurality of subpixels, a blue quantum dot material disposed in the third subpixel; a fourth subpixel included in the plurality of subpixels, wherein a sacrificial material or a color conversion material is disposed in the fourth subpixel; and a photo-bleached blue quantum dot material disposed over a first surface of the subpixel isolation structures, the red conversion material, and the green conversion material.

18. The device of claim 17, wherein the blue quantum dot material has an optical density of 0.5 to 3.

19. The device of claim 17, wherein the red conversion material comprises a quantum dot material, and the green conversion material comprises a quantum dot material.

20. The device of claim 17, wherein the blue quantum dot material has between 5% and 30% concentration by weight of quantum dots.