Method for subpixel compensation with custom pixel isolation structures

Abstract

A multi-color display device and corresponding method for forming the display are provided. The method includes forming and bonding a backplane layer and a micro-LED layer having an array of micro-LED die, wherein the bonded layers comprise an array of LED pixels. Each of the LED pixels includes a group of subpixels with a first, second, and third colored subpixel, and a fourth replacement subpixel. The method also includes testing the array of LED pixels to identify defective LED pixels, and fabricating a plurality of wells for isolating one or more subpixels of each LED pixel. For each defective LED pixel in which one of the first, second, or third colored subpixels is defective, the defective subpixel is isolated with a fourth replacement subpixel within one of the plurality of wells to in turn boost a color of the defective subpixel.

Description

METHOD FOR SUBPIXEL COMPENSATION WITH CUSTOM PIXEL ISOLATION STRUCTURESBACKGROUNDField

[0001] Embodiments of the present disclosure generally relate to light-emitting- diode (LED) display devices and methods of forming such display devices.Description of the Related Art

[0002] LED display technology has made rapid increases in display resolution over the last decade. LED panels use an array of LEDs, with individual LEDs providing the individually controllable pixel elements. LED display devices are made from millions of micron-sized pixels are made possible by fabrication processes that produce intricately patterned material layers on substrate surfaces. Most LED televisions and monitors made today have a pixel density of around 80 ppi (i.e. , “4K” resolution), and displays with 160 ppi (i.e., “8K” resolution) are being offered by an increasing number of manufacturers. The display industry is starting to publicize a next-generation of high-resolution displays that have been called “micro-LED” displays (a.k.a., p-LED) that have pixel densities of up to 650 ppi.

[0003] However, a problem with making high-pixel-density structures is that more pixels mean more opportunities for pixel defects during fabrication operations. Pixel defects include point defects in subpixels that fail to emit any light (i.e., “dead” subpixels) and subpixels that emit too much or too little light that create a color distortion in the overall pixel. Unfortunately, as the dimensions of the pixels get smaller in higher-pixel-density structures, it becomes increasingly difficult and expensive to isolate and replace point defects in the subpixels without disrupting adjacent subpixels and the control circuitry in one or more backplane layers that are in electronic communication with the subpixel.

[0004] Thus, there is a need for improved systems and methods that can be used to produce high-quality materials and structures for LED display devices.SUMMARY

[0005] In some embodiments, a method of forming a multi-color display device is provided. The method includes forming a backplane layer and a micro-LED layerhaving an array of micro-LED dies. The micro-LED layer may then be bonded to the backplane layer, wherein the bonded layers comprise an array of LED pixels. Each of the LED pixels in the array of LED pixels includes a group of subpixel with a first colored subpixel, a second colored subpixel, a third colored subpixel, and a fourth replacement subpixel. The method also includes testing the array of LED pixels to detect one or more defective subpixels and identify normal LED pixels determined to not include a defective subpixel and defective LED pixels determined to include at least one defective subpixel. After identifying one or more defective LED pixels, the method continues with fabricating a plurality of features on the micro-LED layer to form a plurality of wells on the micro-LED layer. Each of the plurality of wells is defined by one or more features of the plurality features with each well isolating one or more subpixels of each LED pixel from adjacent subpixels in the array of LED pixels.

[0006] For LED pixel identified as being normal, the plurality of wells are configured such that the first, second, third, and fourth subpixels are each isolated within one of the plurality of wells. For each defective LED pixel in which one of the first, second, or third colored subpixels is determined to be a defective subpixel, the plurality of wells for the defective LED pixel are configured such that the defective subpixel is isolated with a fourth replacement subpixel within one of the plurality of wells, and the remaining colored subpixels of the defective LED pixel are each isolated within one of the plurality of wells. With the plurality of wells formed, the method further includes forming a first color conversion layer within each of the plurality of wells isolating at least the first colored subpixel of each LED pixel, forming a second color conversion layer within each of the plurality of wells isolating at least the second colored subpixel of each LED pixel, and forming a third color conversion layer within each of the plurality of wells isolating at least the third colored subpixel of each LED pixel.

[0007] In some embodiments, a method of forming custom pixel isolation structures for a multi-color display device is provided. The method includes providing an array of LED pixels with each of the LD pixels in the array of LED pixels including a group of subpixel with a first colored subpixel, a second colored subpixel, a third colored subpixel, and a fourth replacement subpixel. The method also includes testing the array of LED pixels to detect one or more defective subpixels and identify normal LED pixels determined to not include a defective subpixel and defective LED pixels determined to include at least one defective subpixel. After identifying one ormore defective LED pixels, the method continues with fabricating a plurality of features on the micro-LED layer to form a plurality of wells on the micro-LED layer. Each of the plurality of wells is defined by one or more features of the plurality features with each well isolating one or more subpixels of each LED pixel from adjacent subpixels in the array of LED pixels.

[0008] For each normal LED pixel, the plurality of wells are configured such that each of the first, second, third, and fourth subpixels are isolated within one of the plurality of well. For each defective LED pixel in which one of the colored subpixels positioned adjacent to the fourth replacement subpixel is determined to be a defective subpixel, the plurality of wells for the defective LED pixel are configured such that the defective subpixel is isolated with the fourth replacement subpixel of the defective LED pixel within one of the plurality of wells, and the remaining subpixels of the defective LED pixel are each isolated within one of the plurality of wells. For each defective LED pixel in which a colored subpixel positioned diagonally from the fourth replacement subpixel is determined to be a defective subpixel, the plurality of wells are configured such that the defective subpixel is isolated with a fourth replacement subpixel of an adjacent LED pixel within one of the plurality of wells, and the remaining non-defective subpixels of the defective LED pixel are each isolated within one of the plurality of wells.

[0009] In some embodiments, a multi-color display device is provided. The multicolor display includes a backplane layer having backplane circuitry and a micro-LED layer bonded with and electrically integrated with the backplane circuitry. The bonded layers include an array of LED pixels in which each of the LED pixels include a group of subpixels having a first colored subpixel, a second colored subpixel, a third colored subpixel, and a fourth replacement subpixel. The color conversion array is coupled to the bonded layers. The color conversion array includes a plurality of features and a plurality of wells. Each of the plurality of wells is defined by one or more features of the plurality of features, and each of the plurality of wells isolate one or more subpixels of each LED pixel from adjacent subpixels in the array of LED pixels. In some embodiments, the array of LED pixels includes normal LED pixels in which each of the subpixels function normally, and one or more defective LED pixels in which one of the first, second, or third colored subpixels is determined to be a defective subpixel. The plurality of wells for each normal LED pixel are formed such that the first, second,third, and fourth subpixels of each normal LED pixel are each isolated within one of the plurality of wells. The plurality of wells for each of the one or more defective LED pixels are formed such that the defective subpixel is isolated with the fourth replacement subpixel of the defective LED pixel within one of the plurality of wells, and the remaining colored subpixels of the defective LED pixel are each isolated within one of the plurality of wells

[0010] In other embodiments, a method of forming a multi-color display device is provided. The method includes forming a backplane layer having circuitry and a micro-LED layer having an array of micro-LED dies, and bonding the micro-LED layer with the backplane layer in which the bonded layers comprise an array of LED pixels. Each of the LED pixels in the array of LED pixels includes a group of subpixel with a first colored subpixel, a second colored subpixel, a third colored subpixel, and a fourth replacement subpixel. The method also includes testing the array of LED pixels to detect one or more defective subpixels and identify normal LED pixels determined to not include a defective subpixel and defective LED pixels determined to include at least one defective subpixel. After identifying one or more defective LED pixels, the method continues with fabricating a plurality of features on a color conversion substrate to form a color conversion array corresponding to the array of LED pixels. The color conversion array includes a plurality of wells with each of the plurality of wells defined by one or more features of the plurality features, and each of the plurality of wells corresponding to and for isolating one or more subpixels of each LED pixel from adjacent subpixels in the array of LED pixels. For LED pixel identified as being normal, the plurality of wells are configured such that the first, second, third, and fourth subpixels are each isolated within one of the plurality of wells. For each defective LED pixel in which one of the first, second, or third colored subpixels is determined to be a defective subpixel, the plurality of wells for the defective LED pixel are configured such that the defective subpixel is isolated with a fourth replacement subpixel within one of the plurality of wells, and the remaining colored subpixels of the defective LED pixel are each isolated within one of the plurality of wells. With the plurality of wells formed, the method further includes forming a first color conversion layer within each of the plurality of wells isolating at least the first colored subpixel of each LED pixel, forming a second color conversion layer within each of the plurality of wells isolating at least the second colored subpixel of each LED pixel, forming a third colorconversion layer within each of the plurality of wells isolating at least the third colored subpixel of each LED pixel, and integrating the color conversion array with the bonded layers of the micro-LED layer and the backplane layer.BRIEF DESCRIPTION OF THE DRAWINGS

[0011] 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, and may admit to other equally effective embodiments.

[0012] FIG. 1A is a schematic top view of a micro-LED array integrated with a backplane, according to certain embodiments;

[0013] FIG. 1 B is a schematic top view of a portion of the micro-LED array depicted in FIG. 1A, according to certain embodiments;

[0014] FIG. 2 is a schematic top view of a portion of a LED pixel array, according to certain embodiments;

[0015] FIG. 3 is a split-open cross-sectional view of a LED pixel, according to certain embodiments;

[0016] FIG. 4 is a flow diagram of a method for forming a multi-color display device, according to certain embodiments;

[0017] FIGs. 5A and 5B are top views of exemplary LED pixel color arrays, according to certain embodiments; and

[0018] FIGs. 6A-6F are top views of exemplary subpixel isolation structures for a LED pixel, according to certain embodiments.

[0019] To facilitate understanding, identical reference numerals have been used, where possible, to designate identical elements that are common to the figures. It iscontemplated that elements and features of one embodiment may be beneficially incorporated in other embodiments without further recitation.DETAILED DESCRIPTION

[0020] The present technology includes embodiments for manufacturing high- pixel-density light-emitting-diode (LED) panels or devices. A LED panel uses an array of LEDs, with individual LEDs providing the individually controllable pixel elements. Such an LED panel can be used for a computer, touch panel device, personal digital assistant (PDA), cell phone, television monitor, ARA / R display, 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 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 fabrication of micro-LED panels. Micro-LEDs having different color emission (e.g., red, green and blue pixels) need to be fabricated on different substrates through separate processes.

[0021] The present technology includes exemplary semiconductor processing methods for fabricating display devices that addresses conventional challenges and custom subpixel isolation structures suitable for compensating for defective micro- LED dies are provided herein. Embodiments of the present disclosure include fabrication methods that that grow the materials for the micro-LED dies on one substrate (the LED substrate), form the control circuitry for controlling the light emissions from the LEDs on a second substrate (the backplane layer), and preparation of a color conversion layer on a third substrate. The backplane layer and the LED substrate are then bonded together to integrate the micro-LED dies with the backplane circuitry.

[0022] The color conversion layer may correspondingly be prepared including forming custom pixel isolation structures to define a subpixel well array and depositing color specific quantum dot layers in each of the subpixel wells. Assuming the micro- LED display is a three-color display, each LED pixel may be configured in a four subpixel matrix with three isolated color subpixels (e.g., one each for the blue, green and red color channels), and a fourth replacement subpixel that is blank (e.g., not filled with a quantum dot layer). The fourth replacement subpixel of each LED pixel mayfunction as a replacement subpixel if any of the other three color subpixels in the same LED pixel fail during fabrication. To deposit the quantum dot layers for the other three colored subpixels in each LED pixel, a single print pass may be performed to concurrently deposit a quantum dot layer of a specific color (e.g., red, green, or blue) in the corresponding subpixel well of each subpixel designated to emit the corresponding color being printed. As such, a minimum of three color print passes is performed on a color conversion layer being prepared for a three-color display. After formation of the quantum dot layers, the color conversion layer may then subsequently be bonded with the backplane to provide a display stack of the LED display device. In the display stack, each of the corresponding subpixels of a LED pixel includes a micro-LED die operable to generate short-wavelength light that pumps a corresponding quantum dot layer disposed in the corresponding subpixel well to emit longer-wavelength, visible light.

[0023] As discussed above, a problem with making high-pixel-density structures is that more LED pixels mean more opportunities for LED pixel defects during fabrication operations. Currently, after the CCL substrate is fabricated and bonded with the backplane, repair operations may be performed to repair defective LEDs. In some embodiments, defective LEDs include detection of defects such as detection of corresponding subpixels that fail to generate any light, subpixels that fail to generate light at a constant intensity, and subpixels that fail to generate light at a target intensity (e.g., subpixels that are too dim or too bright), among other kinds of defects. For each of the defective LED pixel detected, a repair of the defective LED pixel may be performed by forming a replacement quantum dot layer in the subpixel well of the fourth replacement subpixel in the defective LED pixel. The replacement quantum dot layer is operable to enable the fourth replacement subpixel to emit light at the same wavelength as the defective subpixel and may therefore reduce the number of faulty LED pixels in the high-pixel-density structure. However, the detection and repair of faulty LED pixels via the formation of replacement quantum dot layers is time consuming and expensive as forming the replacement quantum dot layer for each defective LED requires a separate quantum do layer print process, and each defective LED must also be individually repaired one at a time.

[0024] Embodiments of the present disclosure provides methods for forming high- pixel-density structures that avoids the need for individually forming replacementquantum dot layers to compensate for defect micro-LED dies in each defective LED pixel. The method includes testing the micro-LED dies after the LED substrate is bonded with backplane layer to map and determine defective micro-LED dies in the backplane layer prior to the formation of the pixel isolation structures. In some embodiments, the mapping of the defective micro-LED dies includes mapping the corresponding micro-LED dies integrated with the backplane layer with each of the LED pixels and corresponding color subpixels to be formed for the display device. As the positioning of each of the color subpixels in the four subpixel matrix is generally consistent between each LED pixel, mapping the micro-LED dies in turn provides information regarding the specific subpixel and color thereof in each LED pixel to be affected by the defective micro-LED dies detected.

[0025] In some embodiments, techniques of the present disclosure also include preparation of a color conversion layer with custom pixel isolation structures formed based on the micro-LED die mapping and defective micro-LED dies detected. In one aspect, the custom pixel isolation structures formed enable selective setting of quantum dot materials in one or more of the subpixel wells. The custom pixel isolation structures and the subpixel well array defined thereto may be configured to enable formation of a color boosting quantum dot layer in the fourth replacement subpixel of each defective LED pixel determined to contain a defective subpixel based on the micro-LED die mapping and the defective micro-LED dies detected. The custom pixel isolation structure allow the color boosting quantum dot layer in the fourth replacement subpixel to be printed concurrently with the quantum dot layer of the defective subpixel to boost the said quantum dot layer and / or otherwise compensate for the defective micro-LED die of the defective subpixel. Methods of the present enables formation of the color boosting quantum dot layer without the need for additional subsequent replacement quantum dot layer printing or deposition operations after the color conversion layer is bonded to the backplane layer.

[0026] In some embodiments, assuming the micro-LED display is a three-color display as in the above with each LED pixel comprising four subpixels arranged in a 2 x 2 matrix, the custom pixel isolation structures may be formed such that a quantum dot layer for boosting the color of the subpixel with the defective micro-LED is concurrently deposited in both the defective subpixel and the fourth replacement subpixel of the defective LED pixel during the initial three printing passes performedto form the quantum dot layers for the color conversion layer of the micro-LED display. In some embodiments, the custom pixel isolation structures for isolating and forming each of the subpixel wells in the color conversion layer may be formed such that the subpixel well for the fourth replacement subpixel may be in fluid communication with an adjacent subpixel well corresponding to one of the colored subpixels connected to a defective micro-LED die. In some embodiments, the fourth replacement subpixel may be a subpixel from the same LED pixel. In some embodiments, the fourth replacement subpixel may be a subpixel of an adjacent LED pixel. The resulting LED pixel includes the pixel isolation structures of the fourth replacement subpixel and the colored subpixel with the defective micro-LED die (defective colored subpixel) being isolated together by the pixel isolation structure in a single larger subpixel well. The single larger subpixel well enables the same quantum dot layer to be formed for the fourth replacement subpixel when the printing of the quantum dot layer for the defective colored subpixel is otherwise routinely performed during preparation of the color conversion layer.

[0027] Advantages of the present disclosure include the single larger subpixel well enabling a quantum dot layer corresponding to the quantum dot layer of the subpixel with the defective micro-LED die to concurrently be printed for the fourth replacement subpixel when the quantum dot layer of the subpixel with the defective micro-LED die is printed, avoiding the need for an additional quantum dot print process to be performed as currently required when depositing the replacement quantum dot layer to repair defective LED pixels. In another aspect, the quantum dot layer formed for the fourth replacement subpixel may “boost” the color of the defective subpixel in the defective LED. The color boost from the larger subpixel well therefore enables using the fourth replacement subpixel to compensate for defective colored subpixels due to defective micro-LED dies in each defective LED pixel, without the need for an additional fourth quantum dot print process in the fourth replacement subpixel well.

[0028] In another embodiment, the custom pixel isolation structures may be formed directly on the backplane layer around the micro-LED dies integrated therein to form the subpixel well array, and the color conversion layer / quantum dot layers subsequently deposited over the micro-LED dies in each of the subpixel wells formed on the backplane layer. In some embodiments, the custom pixel isolation structures may be used to form isolating subpixel wells around each of the micro-LED dies in thefour subpixel matrix of each LED pixel determined not to correspond to a defective micro-LED die when the final display stack is assembled. In some embodiments, as discussed above, the pixel isolation structures for the fourth replacement subpixel and the subpixel with the defective micro-LED die may be connected together to form the single larger isolated subpixel well around the micro-LED die for the fourth replacement subpixel and the defective micro-LED die. Forming the larger isolate subpixel well around both micro-LED dies enables the same quantum dot layer to be deposited over the defective micro-LED die to concurrently also be deposited over the micro-LED die for the fourth replacement subpixel.

[0029] In another embodiment, the custom pixel isolation structures for isolating each of the subpixel wells of an LED pixel may be formed such that the larger subpixel well encompasses the fourth replacement subpixel in the defective LED pixel and an adjacent colored subpixel of a second adjacent LED pixel in which the adjacent colored subpixel in the second adjacent LED pixel is designated to receive the same color quantum dot layer that is to be deposited for the defective colored subpixel in the defective LED pixel.

[0030] In other embodiments, after mapping of the defective micro-LED dies and determination of corresponding larger subpixel wells to be formed to boost the color of the subpixels to be formed from the defective micro-LED dies, the designation of the color of the subpixels in each of the LED pixels and the initial printing of the corresponding quantum dot layers may be tailored and adjusted to more evenly distribute the color of the larger subpixels being formed across the display.

[0031] FIG. 1A is a schematic top view of a micro-LED display 100, according to certain embodiments. The micro-LED display 100 includes a micro-LED array 110 integrated with a backplane layer 116 having a backplane circuitry 118, according to certain embodiments of the present disclosure. The backplane layer 116 may be a silicon substrate in which a CMOS circuitry is formed for the backplane circuitry 118. In some embodiments, the backplane layer 116 may be fabricated using conventional CMOS processes. In some embodiments, the CMOS circuitry of the backplane circuitry 118 may be characterized by fast response times to activate subpixels having a largest dimension of less than or about 10 pm.

[0032] FIG. 1 B is a schematic close up top view of a portion 1 B of the micro-LED display 100 in FIG. 1A, accordingly to certain embodiments. The micro-LED array 110 includes a plurality of individual micro-LED dies 112 (shown in FIG. 1 B), according to certain embodiments of the present disclosure. The micro-LED dies 112 are integrated with the backplane circuitry 118 so that each of the micro-LED die 112 can be individually and independently activated and controlled by the circuitry 118 to address and control the subpixels of each of the LED pixels in the final display. For example, the backplane circuitry 118 can include a thin film transistor (TFT) active matrix array with a thin-film transistor and a storage capacitor (not illustrated) for each micro-LED die, column address and row address lines 118a, column and row drivers 118b, etc., to drive the micro-LED dies 112. Alternatively, the micro-LED dies 112 can be driven by a passive matrix in the backplane circuitry 118.

[0033] All of the micro-LED dies 112 are fabricated with the same structure so as to generate the same wavelength range (this can be termed “monochrome” microLEDs). In some embodiments, the micro-LED dies 112 can generate light in the ultraviolet (UV), e.g., the near ultraviolet, range. For example, the micro-LED dies 112 can generate light in a range of 365 to 405 nm. As another example, the micro- LED dies 112 can generate light in the violet or blue range. The micro-LEDs can generate light having a spectral bandwidth of 20 to 60 nm.

[0034] Vertical isolation features 120 are formed between neighboring micro-LED dies 112. The isolation features 120 provide for optical isolation to reduce optical crosstalk between neighboring subpixels. The isolation features 120 can be a photoresist or metal, and can be deposited by conventional lithography processes. As shown in FIG. 1 B, the features 120 can form a rectangular array, with each micro-LED 112 in an individual well 122 defined by the isolation features 120. Other array geometries, e.g., hexagonal or offset rectangular arrays, are also possible. Possible processes for back-plane integration and isolation wall formation are discussed in more detail below.

[0035] FIG. 2 is a schematic top view of a portion 200 of an LED pixel array, according to certain embodiments. In the embodiment shown, the portion 200 of the LED pixel array includes four LED pixels 202 that each includes four subpixels 204A, 204B, 204C, 204D. Each of the LED pixels 202 comprises a square-shapedarrangement of four square-shaped subpixels 204A, 204B, 204C, 204D each. Each of the subpixels 204A, 204B, 204C, 204D in the LED pixel array is disposed over a corresponding micro-LED die, such as one of the micro-LED die 112 in the micro-LED array 110, for illuminating the subpixels of the LED pixel array. For each LED pixel, the subpixels 204A, 204B, 204C, 204D include three subpixels 204A, 204B, 204C that are operable to emit visible light at different average peak wavelengths, and a fourth subpixel 204D that can function as a replacement subpixel, if any of the other three subpixels 204A, 204B, 204C fail during fabrication of the high-pixel-density structure. In certain embodiments, the first, second, and third subpixels 204A, 204B, 204C may be operable to emit visible light in the red, green, and blue portions of the electromagnetic spectrum, respectively.

[0036] FIG. 3 shows a split-open cross-sectional view of a LED structure 300, according to certain embodiments of the present disclosure. In the embodiment shown, the LED structure 300 comprises an LED pixel corresponding to one of the LED pixel 202 shown in FIG. 2. As shown in FIG. 3, the LED pixel is cut between subpixels 204A, 204B, 204C, 204D and split open to reveal a cross-sectional linear arrangement of first, second, third, and fourth subpixels 302A, 302B, 302C, 302D. In some embodiments, the subpixels 302A, 302B, 302C, 302D in LED structure 300 may correspond with red, green, blue, and blank subpixels as discussed above in FIG. 2. As depicted, the LED structure 300 includes a color conversion layer 304 disposed on a micro-LED layer 306 and a backplane layer 308. In some embodiments, the micro- LED layer 306 coupled with the backplane layer 308 may correspond with the micro- LED display 100 depicted in FIGs. 1A and 1 B, including the plurality of micro-LED dies 112 disposed on the backplane layer 308. In some embodiments, the color conversion layer 304 may then be formed on the micro-LED layer 306, or formed on a separate transparent substrate and subsequently coupled to the micro-LED layer 306 after fabrication of the color conversion layer 304 is complete.

[0037] In certain embodiments, a connecting layer 314 extending across the micro- LED dies 112 in the micro-LED array 110 may be disposed between the micro-LED layer 306 and the color conversion layer 304. For example, the connecting layer 314 can extend across the entire micro-LED array 110 in the micro-LED layer 306. In some embodiments, each micro-LED die 112 includes a diode structure 313. In some embodiments, the connecting layer 314 may form a part of each diode structure 313.For example, the connecting layer 314 can be a doped semiconductor layer, e.g., the n-doped semiconductor layer, such as an n-doped gallium nitride (n-GaN) layer, in the diode structure 313.

[0038] The color conversion layer 304 includes a plurality of features 311 defining a plurality of wells 312. In some embodiments, the plurality of features 311 are in the form of a grid structure, such as an interconnected grid forming an array of square shaped wells 312. Each of the wells 312 may be formed over a corresponding microLED die 112. In certain embodiments, the plurality of square shaped wells 312 may be configured to isolate one or more of the subpixels 302A, 302B, 302C, 302D from adjacent subpixels. In some embodiments, a laser induced direct etching process is used to form the plurality of wells 312 and plurality of features 311. Assuming the LED structure 300 is for a three-color display, each subpixel 302A, 302B, 302C may further include a quantum dot layer 310A, 310B, 310C as a color conversion agent disposed in each of a respective first, second, and third well 312A-C formed for each of the LED pixels such that the subpixels are operable to emit different peak intensity wavelengths of visible light (e.g., red, green, and blue light). A fourth subpixel 302D in a fourth well 312D may include a matrix material that is quantum-dot-layer-free unless it functions as a replacement subpixel for one of the other subpixels.

[0039] In some embodiments, during fabrication of multi-color displays, the plurality of features 311 for defining the plurality of wells 312 may be formed over the micro-LED layer 306 such that the quantum dot layers 310A, 310B, 310C are deposited directly on the micro-LED layer 306 when the quantum dot layers are printed in each of the plurality of wells 312. In other embodiments, the quantum dot layers 310A, 310B, 310C may be separately deposited in each of the plurality of wells of a color conversion array formed on a second substrate. In such embodiments, the color conversion array having the quantum dot layers 310A, 310B, 310C deposited and cured thereon may subsequently be coupled with the micro-LED layer to form a multi-color display.

[0040] In some embodiments, the first, second, and third subpixels 302A, 302B, 302C of each of the LED pixels in the multi-color display corresponds with the first, second, and third quantum dot layer 310A, 310B, 310C deposited within first, second, and third wells 312A-C, respectively. As shown, each of the subpixels 302A, 302B,302C, 302D includes a respective micro-LED die 112A-D formed in the micro-LED layer 306. The short-wavelength light emitted by the micro-LED dies 112 in the micro- LED layer 306 may energize the quantum dot layers 310A, 31 OB, 31 OC and cause them to emit light of longer wavelengths. Each of the quantum dot layers 310A, 31 OB, 31 OC is operable to absorb light from its respective micro-LED die 112 and emit light in a different part of the electromagnetic spectrum. In the embodiment shown, quantum dot layer 310A is operable to emit light in the red portion of the visible spectrum, quantum dot layer 31 OB is operable to emit light in the green portion of the visible spectrum, and quantum dot layer 31 OC is operable to emit light in the blue portion of the visible spectrum. The emission light generated by quantum dot layers 310A, 31 OB, 31 OC may pass through a blocking layer 309. In some embodiments, the blocking layer 309 may be a UV blocking layer that filters / absorbs ultraviolet light generated by the micro-LED dies 112 that is not absorbed by the quantum dot layers, while allowing the visible light from the quantum dot layers 310A, 31 OB, 31 OC to pass through towards the viewer. In some embodiments, the light passing through the blocking layer 309 may be focused by a microlens 316 to further improve the quality of an image displayed by the high-pixel-density structure.

[0041] In some embodiments, the first quantum dot layer 310A can be of a first color that can be deposited using any suitable process, such as selective or non- selective inkjet, selective or non-selective spin-coating, selective or non-selective spray coating. The first quantum dot layer 310A can be cured using any suitable process such as selective UV cure, such as by use of a laser, such as by use of a flood light source, such as from a bottom of each well, or such as or from the top of each well. In one aspect, the curing process for the first color conversion layer is performed in an inert environment, such as in a process chamber filled with an inert gas, such as argon, nitrogen, or combinations thereof.

[0042] In some embodiments, the first quantum dot layer 310A is filled into every first well 312A corresponding to each subpixel 302A of each LED pixel in a single quantum dot printing process. After the first quantum dot layer 310A is deposited for each LED pixel, the first quantum dot layer 310A may then be selectively cured. Selectively curing, in some embodiments, includes scanning a laser along a raster path and selectively turning on the laser spot at well array locations to be cured or fixed. The unfixed or uncured color conversion layer can be washed or removed usingsolvent such as isopropyl alcohol. In one embodiment, the thickness of the cured QD ranges from between about 1 pm to about 50 pm. In some embodiments, external laser sources are used and aligned with a base of the wells.

[0043] In other embodiments in which the color conversion layer 304 is formed directly on the micro-LED layer 306 such that when the first quantum dot layers 310A are deposited in first wells 312A, the first quantum dot layer 310 in each of the first wells 312A are each disposed over one of the micro-LED 112As of the micro-LED layer 306. In such embodiments, selective curing of the color conversion layers may be performed using illumination from the respective micro-LED die 112A disposed below each of the first wells 312A by selectively illuminating each of the micro-LED dies 112A for each LED pixel. For example, when curing the first quantum dot layer 310A deposited in first wells 312A, only the micro-LED dies 112A disposed below the first wells 312A of each LED pixel are activated. The curing processes described above can be repeated with other additional quantum dot layers of other colors after the additional quantum dot layers are deposited in respective wells 312 for all of the LED pixels in the LED pixel array.

[0044] Once all of the quantum dot layers 310A, 310B, 310C are deposited and cured, additional blocking layers 309, such as protective layers, passivation layers, and other layers can be deposited over the cured quantum dot layers. In one embodiment, which can be combined with other embodiments herein, the blocking layer 309 is formed from materials such as SiO2, Si3N4, optically transparent organic and inorganic thin films, and the like. In another embodiment, the blocking layer 309 comprises a UV blocking layer. Although not depicted, other processes are also contemplated such as planarization or leveling of layers or fillers.

[0045] FIG. 4 is a flow chart depicting a method 400 for fabricating a multi-color LED structure, such as the LED structure 300 depicted in FIG. 3, according to certain embodiments. Method 400 may or may not include one or more operations prior to the initiation of the method, including front-end processing, deposition, etching, polishing, cleaning, or any other operations that may be performed prior to the described operations. The method may include a number of optional operations, which may or may not be specifically associated with some embodiments of methods, according to the present disclosure.

[0046] Method 400 may begin in operation 402 in which the backplane layer 308 is prepared. In certain embodiments, preparing the backplane layer 308 may include preparing a backplane layer that includes at least a portion of the control circuitry for activating the subpixels in each of the LED pixels of the LED structure 300.

[0047] In operation 404, the micro-LED layer 306 is formed and bonded to the backplane layer 308. The plurality of micro-LED dies 112 in micro-LED layer 306 provides illumination to the subpixels in each of the LED pixels of the LED structure 300. As such, the micro-LED layer 306 also comprises an array of micro-LED dies 112 that corresponds with the array of subpixels of the LED structure 300. In some embodiments, the micro-LED layer 306 may be formed on the backplane layer 308. For example, in some embodiments, a micro-LED substrate may be bonded with the backplane layer 308 and micro-LED structures subsequently patterned on the micro- LED substrate to form the micro-LED layer 306 on the backplane layer 308. In other embodiments, the micro-LED layer 306 may be separately patterned on the LED substrate to form the micro-LED layer 306 before the backplane layer 308 and the micro-LED layer 306 are bonded together at operation 404.

[0048] In operation 406, the plurality of micro-LED dies 112 on the micro-LED layer 306 are tested to determine if any of the micro-LED dies 112 are defective from fabrication. As each of the micro-LED dies 112 in the micro-LED layer 306 corresponds to and illuminates a respective subpixel of the array of subpixels of the LED structure 300, the detection of defective micro-LED dies 112 in turn indicates the subpixels of the LED structure 300 that are defective and will not illuminate upon completion of the LED structure 300. The testing operation may include activating all of the micro-LED dies 112 and detecting which micro-LED dies 112 are defective. In some embodiments, these defects may include micro-LED dies that fail to generate any light, micro-LED dies that fail to generate light at a constant intensity, and micro- LED dies that fail to generate light at a target intensity (e.g., micro-LED dies that are too dim or too bright), among other kinds of defects. Detecting defective micro-LED dies 112 in operation 406 in turn allows for identifying and mapping the normal LED pixels determined to not include a defective subpixel, and defective LED pixels determined to include at least one defective subpixel.

[0049] After the defective micro-LED dies 112 in the micro-LED layer 306 for each of the LED pixels are identified, method 400 may continue in operation 408 with fabricating custom subpixel isolation structures on the micro-LED layer 306. In some embodiments, fabricating the custom subpixel isolation structures includes forming the plurality of features 311 on the micro-LED layer 306 to define the plurality of wells 312. Each of the plurality of wells 312 formed may be configured to isolate one or more subpixels 302 in each LED pixel of the LED structure 300 from each adjacent subpixel. Assuming the multi-color LED structure 300 is for a three-color display, the LED structure 300 includes three designated colored subpixels 302A, 302B, 302C (e.g., one each for the blue, green and red color channels), and a fourth replacement subpixel 302D that is blank (e.g., not filled with a quantum dot layer).

[0050] In some embodiments, which may be combined with other embodiments discussed herein, some of the plurality of features 311 formed may isolate each of the four subpixels 302A, 302B, 302C, 302D of a LED pixel from adjacent subpixels such that each subpixel 302 is isolated within one of the plurality of wells 312 formed by the plurality of features 311. As described in further detail below, in other embodiments, which may be combined with other embodiments discussed herein, some of the plurality of features 311 formed may isolate more than one subpixel 302 of a LED pixel together (e.g., two of the four subpixels in a LED pixel) such that more than one subpixel 302 is isolated within one of the plurality of wells 312. In such embodiments, the well 302 isolates the more than one subpixels together, as well as separates the more than one subpixels from remaining adjacent subpixels of the LED structure 300.

[0051] The plurality of features 311 may be formed from a subpixel isolation material layer disposed on the micro-LED layer 306 and subsequently etched to form the plurality of wells 312. In some embodiments, the subpixel isolation material layer may be etched with a lithography process to form the custom subpixel isolation structures. In some embodiments, the subpixel isolation material layer may be etched with a maskless lithography process. In some embodiments, the material layer can be a transparent material, such as glass or a polymer. In other embodiments, the material layer can be any solid-state material, such as a PET, silicon dioxide (SiO2), fused silica, amorphous silica, ceramics or combinations thereof.

[0052] The plurality of features 311 for forming the custom subpixel isolation structures may include a core column of pixel isolation material etched from the subpixel isolation material layer. The plurality of features 311 may also be coated by one or more additional layers of material, such as a layer of reflective material such as aluminum or copper. In other embodiments, the coating over the etched pixel isolation material may be a refractive material, a light shielding material, or other opaque material. Without being bound by theory, it is believed that coating the pixel isolation material with a refractive material isolates light intrusion through the plurality of features and isolates each well formed. In certain embodiments, the material in the core column may include a metal or a dielectric material, among other types of materials. In further embodiments, the metal material may include one or more of silicon, tungsten, copper, and aluminum, among other metals. In yet further embodiments, the dielectric material may include one or more of silicon oxide, silicon nitride, silicon carbide, a photoresist material, or a dielectric organic-polymer material, among other dielectric materials. The coating over the plurality of features 311 can be formed with a deposition process to achieve a conformal result, including without limitation, a chemical vapor deposition (CVD) process, atomic layer deposition (ALD) process, physical vapor deposition (PVD) process, and plasma enhanced vapor deposition processes.

[0053] The custom subpixel isolation structures fabricated in operation 408 depends on both the defective micro-LED dies detected in operation 406, and the designation of three colored subpixels 302A, 302B, 302C and the fourth replacement subpixel 302D of each LED pixel in the LED structure 300.

[0054] FIGs. 5A and 5B are top views of exemplary LED pixel color arrays indicating an example designation of colors of each of the three colored subpixels in each LED pixel, according to certain embodiments. In FIG. 5A, a uniform LED pixel array 500 is shown having a plurality of LED pixels 502 each having a first subpixel 504A, a second subpixel 504B, a third subpixel 504C, and a fourth subpixel 504D. The first, second, and third subpixels 504A, 504B, 504C in each LED pixel 502 corresponds to the colored subpixels, and the fourth subpixel 504D corresponds to the fourth replacement subpixel. As shown in FIG. 5A, in some embodiments, the first subpixel 504A in each LED pixel 502 is designated to be a red colored subpixel, the second subpixel 504B is designated to be a green colored subpixel, and the thirdsubpixel 504C is designated to be a blue colored subpixel. The designation of colored subpixels in each LED pixel, as well as the specific colors of each of the colored subpixels, pertains to the specific colored quantum dot layers to be printed for each subpixel during fabrication. For a three-color display in which three different colored quantm dot layers is utilized for each LED pixel, a quantum dot layer corresponding to a first color is printed for each pixel on the subpixel designated to emit said first color in a single printing pass. Accordingly, a minimum of three quantum dot layer printing passes is therefore needed for printing corresponding quantum dot layers for three colors in the three colored subpixels of each and every pixel.

[0055] In some embodiments, the designation of the colored subpixels and / or the colors of the first, second, and third subpixels 504A, 504B, 504C in each LED pixel 502 may be the same for all LED pixels 502 in the display, as shown in FIG. 5A. In some embodiments, the designation of the colored subpixels or the colors of the first, second, and third subpixels 504A, 504B, 504C in each LED pixel 502 may not be the same for all LED pixels 502 in the display.

[0056] For example, as shown in FIG. 5B, a modified LED pixel array 550 is shown having a plurality of LED pixels 552 in first LED pixel rows 554, alternating with a plurality of LED pixels 556 in second LED pixel rows 558. In some embodiments, each of the LED pixels 552, 556 have a first colored subpixel 560 and a second colored subpixel 562 in an upper left and upper right quadrant of the LED pixels 552, 556. In some embodiments, the first colored subpixel 560 and the second colored subpixel 562 correspond to a red color subpixel and a green color subpixel, respectively. LED pixels 552 also include a third colored subpixel 564 in a lower left quadrant of LED pixel 552, and a fourth replacement subpixel 566 in a lower right quadrant of LED pixel 552. In contrast, LED pixels 556 include a third colored subpixel 568 in a lower right quadrant of LED pixel 556, and a fourth replacement subpixel 570 in a lower left quadrant of LED pixel 556. In some embodiments, the third colored subpixels 564, 568 correspond to blue color subpixel. The modified LED pixel array 550 therefore includes the relative positioning of the green colored subpixel and the replacement subpixel in each of the LED pixels alternating between first LED pixel rows 554 and second LED pixel rows 558.

[0057] In one aspect, the subpixel isolation structures formed by the plurality of features isolate each subpixel of each LED pixel in the LED pixel array from each adjacent subpixel. The isolation structures prevent light in one color emitted from one subpixel from interfering with the light of another color emitted from an adjacent subpixel. The isolation structures decrease the crosstalk created by light emitted from adjacent subpixels, which reduces discoloration and image distortion in the high-pixel- density display.

[0058] However, as indicated above, sometimes one or more micro-LED dies 112 fabricated in the micro-LED layer 306 may be defective resulting in faulty LED pixels having a defective subpixel. Such faulty LED pixels can cause color distortions and affect the quality of the images displayed. In some embodiments, faulty LED pixels may be repaired by subsequently forming a replacement quantum dot layer in the fourth replacement subpixel corresponding to the specific defective subpixel. Unfortunately and as mentioned above, as the dimensions of the pixels get smaller in higher-pixel-density displays, it becomes increasingly difficult to isolate and replace point defects in the subpixels. Furthermore, such subsequent replacement of point defects in subpixels can be expensive and time consuming due to the each subpixel needing to replaced one at a time with the printing of a specific quantum dot layer.

[0059] Advantages of the present disclosure therefore utilize customized isolation structures to address such point subpixel defects and reduce the number of faulty LED pixels in the high-pixel-density structure. Specifically, in operation 408, custom subpixel isolation structures are formed for LED pixels disposed over micro-LED dies 112 determined to be defective in operation 406. In some embodiments, depending on whether the LED pixel is faulty or not, each of the plurality of wells 312 formed by the plurality of features for the custom subpixel isolation structures may isolate either each subpixel from each adjacent subpixel, or more than one subpixel together (e.g., two subpixels together) from each adjacent subpixel.

[0060] FIGs. 6A-6E are top views of exemplary subpixel isolation structures for a LED pixel for forming the custom subpixel isolation structures in operation 408, according to certain embodiments. FIG. 6A shows custom subpixel isolation structures formed for LED pixels 552, 556 in the LED pixel array 550 depicted in FIG 5B, according to certain embodiments.

[0061] In some embodiments, which can be combined with other embodiments described herein, for each of the LED pixels 552, 556 determined to not be faulty, the custom subpixel isolation structure having a plurality of wells 606 for such LED pixels are configured such that the subpixels of each of the LED pixels 552, 556 are each isolated within one of the plurality of wells 606 by a plurality of features 608, as shown in FIG. 6A.

[0062] In some embodiments, which can be combined with other embodiments described herein, for each of the LED pixels 552, 556 determined to be faulty such that one of the colored subpixels in the LED pixel is determined to correspond with a defective micro-LED die detected in operation 406, the plurality of features 608 are configured such that non-defective colored subpixels in each of the LED pixels 552, 556 are each isolated within one of the plurality of wells 606. The defective colored subpixel is isolated together with a replacement subpixel adjacent to (e.g., sharing a side with) the defective colored subpixel in one of the plurality of well 606.

[0063] Depending on the position of the defective colored subpixel in the LED pixel and the designation of colored subpixels in the LED pixel array, the defective colored subpixel may be isolated with a replacement subpixel of the same LED pixel or a replacement subpixel in an adjacent LED pixel. As shown in FIGs. 6B and 6C, if the defective colored subpixel is one of the second and third colored subpixels 562, 564 positioned adjacent to the fourth replacement subpixel 566 in the same LED pixel 552, that is, the defective colored subpixel shares a side with the fourth replacement subpixel 566, the plurality of features 608 formed for the custom subpixel isolation structures is configured to isolate the defective colored subpixel with the fourth replacement subpixel 566 in one of the plurality of wells, such as a larger well 610 sized to encompass both the defective subpixel and the fourth replacement subpixel together. FIG. 6B shows the larger well 610 formed if the second colored subpixel 562 in LED pixel 552 was defective, thereby encompassing the second colored subpixel 562 and the fourth replacement subpixel 562 together. So as to prevent cross talk, the first colored subpixel 560 and third colored subpixel 564 in LED pixel 552 are also each isolated in one of the plurality of wells 606. FIG. 6C shows the larger well 610 formed if the third colored subpixel 564 in LED pixel 552 was defective, thereby enclosing the third colored subpixel 564 and the fourth replacement subpixel 662 together.

[0064] Similar to LED pixel 552, FIGs. 6D and 6E show the plurality of features 608 configured for the custom subpixel isolation structure if the defective subpixel was one of the first and third colored subpixels 560, 568 of LED pixel 556. FIG. 6D shows the larger well 610 formed from the features 608 if the defective subpixel was the first colored subpixel 560 positioned adjacent to the fourth replacement subpixel 570. In such an embodiment, so as to prevent cross talk, the second colored subpixel 562 and third colored subpixel 568 in LED pixel 556 are also each isolated in one of the plurality of wells 606. FIG. 6E shows the larger well 610 formed if the third colored subpixel 568 adjacent to the fourth replacement subpixel 570 in LED pixel 556 was defective. The well 610 formed similar would enclose the third colored subpixel 568 and the fourth replacement subpixel 570 together.

[0065] In another embodiment, if the defective colored subpixel is not adjacent to a replacement subpixel in the same, such as the defective colored subpixel is a colored subpixel positioned diagonal from the respective fourth replacement subpixel, then the larger well 610 is formed so as to isolate the defective colored subpixel with a fourth replacement subpixel in an adjacent LED pixel in an adjacent row of LED pixels. In such embodiments, the forming of such larger wells 610 may require the designation of the replacement subpixel in LED pixels of the LED pixel to vary between LED pixels, such as the modified LED pixel array 550 depicted in FIG. 5B.

[0066] FIG. 6F shows custom subpixel isolation structures formed if the first colored subpixel 560 of LED pixel 552 in the modified LED pixel array 550 is determined to be defective. As shown in FIG. 5B, for LED pixels 552 in first LED pixel rows 554 disposed below LED pixels 556 of second LED pixel rows 558, the first colored subpixels 560 of LED pixels 552 is positioned below the fourth replacement subpixel of LED pixels 556. Accordingly, to assist in boosting the defective first colored subpixel 560 in LED pixel 552, fabricating the custom subpixel isolation structures includes forming the larger well 610 in such instances to isolate the defective first colored subpixel 560 in LED pixel 552 with the respective adjacent fourth replacement subpixel 570 of LED pixel 556 in the corresponding adjacent second LED pixel row 558.

[0067] The forming of the custom subpixel isolation structures in operation 408 may assist in addressing the defective micro-LED dies 112 by boosting the designatedcolor of the defective subpixel using a replacement subpixel adjacent to the defective subpixel. In one embodiment, by isolating the defective subpixel and the replacement subpixel together in one of the plurality of wells 312, the custom isolate structure enables a quantum dot layer designated to be deposited for the defective subpixel to concurrently also be deposited for the adjacent replacement subpixel when the quantum dot layer printing is performed for the defective subpixel as a matter of course. For example, by isolating the defective subpixel with the replacement subpixel in a single well, the quantum dot layer designated to be printed in the defective subpixel as a matter course would also flow into and over the micro-LED die 112 of the replacement subpixel. When in use, the replacement subpixel in the LED pixel may then subsequently replace or provide a boost in the specific color normally to be wholly provided by the defective subpixel.

[0068] Using the replacement subpixel in this manner provides the same benefit as performing the subpixel point defect repair and replacement processes discussed above where each subpixel is normally isolated from every other subpixel, and quantum dot layers are subsequently deposited in replacement subpixels to compensate for defective subpixels when faulty LED pixels are identified. Accordingly, advantages of the custom subpixel isolation structure formed for the defective subpixels enable an adjacent replacement subpixel to be utilized to boost the color of the defective subpixel without the need for an additional quantum dot layer to separately be printed for the replacement subpixel, as is normally required and as mentioned above.

[0069] After the custom subpixel isolation structures are formed on the micro-LED layer 306, method 400 continues in operation 410 with the formation of quantum dot layers in each of the wells 312 formed by the custom subpixel isolation structure. In certain embodiments, the formation of the quantum dot layers may include sequential operations to form a quantum dot layer 310 operable to emit light characterized by a particular peak intensity wavelength in one of the colored subpixels of each LED pixel of the array of LED pixels. In some embodiments, the sequential operations may include forming a red quantum dot layer 310A in one of the colored subpixels of each LED pixel designated to emit a red channel, then forming a green quantum dot layer 310B in another one of the colored subpixels of each LED pixel designated to emit a green channel, and then forming a blue quantum dot layer 310C in still another oneof the colored subpixels in each LED pixel designated to emit a blue channel. In further embodiments, the forming of a quantum dot layer in one of the colored subpixels may concurrently form the same quantum dot layer in a replacement subpixel for replacement subpixels isolated by the custom subpixel isolation structures with the same colored subpixel together in one of the plurality of wells 312.

[0070] Following the formation of the blue quantum dot layer 310C, each LED pixel in the array of LED pixels includes red, green, and blue subpixels. For LED pixels having subpixels determined to be defective, such LED pixels include a boosted color with two adjacent subpixels (one corresponding to the defective micro-LED die determined in operation 406 and the other corresponding to the replacement subpixel isolated therewith) the color of the defective subpixel.

[0071] In additional embodiments, the formation of a quantum dot layer operable to emit a particular color of visible light (e.g., red, green, or blue light) in a LED subpixel may include dispensing a photo-curable fluid over the LED structure, activating one of the subpixels in each LED pixel in the array of LED pixels to illuminate and cure the photo-curable fluid over that subpixel, and removing the uncured photo-curable fluid from the other subpixels that were not activated. These formation operations may be repeated for the subpixels emitting each color of light in the array of LED pixels. In certain embodiments, the formation operation self-aligns the quantum dot layers with the activated subpixels of the LED pixels throughout the array of LED pixels. No precision alignment operations are required to form the quantum dot layers in the proper group of subpixels. The self-alignment of the quantum dot layers is increasingly beneficial as the size of the subpixels decreases and the pixel density increases.

[0072] In some embodiments, one of the colored subpixels may be considered a red subpixel that is operable to emit visible light characterized by a peak intensity wavelength of greater than or about 580 nm, greater than or about 585 nm, greater than or about 590 nm, greater than or about 595 nm, greater than or about 500 nm, greater than or about 605 nm, greater than or about 510 nm, greater than or about 615 nm, greater than or about 620 nm, or more. In some embodiments, one of the colored subpixels may be considered a green subpixel that is operable to emit visible light characterized by a peak intensity wavelength that is operable to emit visible lightcharacterized by a peak intensity wavelength between 500 nm and 580 nm. In some embodiments, one of the colored subpixels may be considered a blue subpixel that is operable to emit visible light characterized by a peak intensity wavelength that is operable to emit visible light characterized by a peak intensity wavelength less than or about 500 nm, less than or about 490 nm, less than or about 480 nm, less than or about 470 nm, less than or about 460 nm, less than or about 450 nm, less than or about 440 nm, less than or about 430 nm, less than or about 420 nm, less than or about 410 nm, less than or about 400 nm, or less.

[0073] In certain embodiments, the photo-curable fluid may include one or more cross-linkable compounds, a photo-initiator, and a color conversion agent. In additional embodiments, the cross-linkable compounds may include monomers that form a polymer when cured. In more embodiments, the monomers may include acrylate monomers, methacrylate monomers, and acrylamide monomers. In yet more embodiments, the cross-linkable compounds may include a negative photoresist material such as Sll-8 photoresist. In further embodiments, the photo-initiator may include phosphine oxide compounds and keto compounds, among other kinds of photo-initiator compounds that generate radicals that initiate the curing of unsaturated compounds when excited by ultraviolet light. Commercially available photo-initiator compounds include Irgacure 184, Irgacure 819, Darocur 1173, Darocur 4265, Darocur TPO, Omnicat 250, and Omnicat 550, among other photo-initiators. In still further embodiments, the color conversion agent may include a quantum dot material that can absorb shorter wavelength (i.e., more energetic) light from the LED structure and emit longer wavelength light corresponding to the color of light emitted by the subpixel. In embodiments, these quantum-dot materials may include nanoparticles made of one or more kinds of inorganic semiconductor materials such as indium phosphide, zinc selenide, zinc sulfide, silicon, silicates, and graphene, and doped inorganic oxides, among other semiconductor materials.

[0074] In some embodiments, after the custom subpixel isolation structure is mapped and fabricated based on the detected defective micro-LED dies 112 in operation 408, knowledge of the position of various larger subpixels containing and formed to boost or compensate for defective subpixels may be utilized for subsequently redefining the colored subpixel designations of various LED pixels, and / or the color of the various subpixels prior to deposition the quantum dot layers inoperation 410. Redefining the colored subpixel designations for at least some of the LED pixels enables the color of the larger subpixels to in turn also be redefined. For example, the color of colored subpixel designations in each LED pixel may be redefined so as to more evenly redistribute the color of each of the larger pixels as defined by the custom subpixel isolation structures. In other embodiments, additional larger pixels may be formed in normal LED pixels to more evenly form and distribute larger pixels across the display based on the color of the larger pixels or the LED device yield. In further embodiments, after the mapping / testing of micro-LED dies 112 in operation 408 for identifying defective micro-LED dies 112 and / or low intensity micro-LED dies 112, the larger pixels may be defined according to the position of the low intensity micro-LED dies 112 as well.

[0075] Method 400 may further include forming the blocking layer 309 on the subpixels of the LED pixels at operation 412. In certain embodiments, the blocking layer 309 may be a UV blocking layer formed over the quantum dot layers 310 in the wells 312 of each subpixel having a quantum dot layer deposited. In further embodiments, the blocking layer 309 may be a dielectric layer that absorbs UV light generated by the micro-LED dies 112 in the subpixel while transmitting the visible light emitted by the quantum dot layers. In embodiments, the dielectric layer may be a silicon oxide layer deposited by chemical vapor deposition or physical vapor deposition. In additional embodiments, the blocking layer 309 may be made from organic polymers such as polyacrylates, polymethyl methacrylates, and copolymers of polyacrylates and polymethyl methacrylates. In yet further embodiments, the blocking layer 309 may be made from commercially available materials such as Tinuvin CarboProtect from BASF, and the Eversorb series from Everlight. In some embodiments, the blocking layer 309 may reduce the percentage of UV light in the total light emitted from the high-pixel-density structure to less than or about 5%, less than or about 2.5%, less than or about 1 %, less than or about 0.5%, less than or about 0.1 %, less than or about 0.05%, less than or about 0.01 %, or less. In additional embodiments, the blocking layer may transmit visible light from the quantum-dot layer at greater than or about 50%, greater than or about 75%, greater than or about 85%, greater than or about 90%, greater than or about 95%, greater than or about 99%, or more.

[0076] Method 400 may still additionally include forming a microlens 316 on one or more of the subpixels in the LED pixels of the array of LED pixels at operation 414. In some embodiments, the microlens 316 may be formed on two or more of the subpixels, three or more of the subpixels, and all of the subpixels in each of the LED pixels. In additional embodiments, the microlenses may be convex-shaped lenses, concave-shaped lenses, Fresnel-shaped lenses, among other lens shapes. In further embodiments, the microlenses may be made of inorganic or organic materials that can transmit the visible light emitted from the subpixels. In additional embodiments, the microlenses may be made of polymers such as polydimethylsiloxanes, polyacrylates, polymethyl methacrylates, polybutyl methacrylates, polystyrenes, and poly(benzyl methacrylates), among other polymers. In more embodiments, the microlenses may be made of inorganic materials such as silica, zinc oxide, and aluminum oxide, among other inorganic materials. In some embodiments, the microlenses bend and focus the light emitted by the high-pixel-density structure to increase image quality for specific applications such as VR headsets and AR glasses, among other applications.

[0077] In another embodiment, operations 408 and 410 may alternatively be performed on a separate color conversion substrate instead of the micro-LED layer 306. In such embodiments, the custom subpixel isolation structures may be formed on the color conversion substrate similar to the manner described above in operation 408 and based on the detected defective micro-LED dies 112 in operation 406, and the quantum dot layers 310 may then subsequently be deposited and cured to form a color conversion layer. The color conversion layer may then be bonded with the micro-LED layer 306 in which the process may then continue with operation 412.

[0078] Terms of positioning, such as adjacent to, above, and below have been used. However, it should be understood that such terms refer to relative positioning, not absolute positioning with respect to gravity. For example, laterally is a direction parallel to a substrate surface, whereas vertically is a direction normal to the substrate surface.

[0079] It will be appreciated to those skilled in the art that the preceding examples are exemplary and not limiting. For example, although the above description focuses on micro-LEDs, the techniques can be applied to other displays with other types oflight emitting diodes, particularly displays with other micro-scale light emitting diodes. Although the above description assumes that the order in which the color conversion layers are formed is blue, then green, then red, other orders are possible. For example, blue, then red, then green. In addition, other colors are possible, e.g., orange and yellow.

[0080] 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 forming a multi-color display device, comprising: forming a backplane layer and a micro-LED layer, the micro-LED layer comprising an array of micro-LED dies; bonding the micro-LED layer to the backplane layer, wherein: the bonded layers comprise an array of LED pixels; each of the LED pixels comprising a group of subpixels; and each group of subpixels comprising a first colored subpixel, a second colored subpixel, a third colored subpixel, and a fourth replacement subpixel; testing the array of LED pixels to detect one or more defective subpixels and identify normal LED pixels determined to not include a defective subpixel, and defective LED pixels determined to include at least one defective subpixel; fabricating a plurality of features on the micro-LED layer to form a plurality of wells, each of the plurality of wells defined by one or more features of the plurality of features, and each well isolating one or more subpixels of each LED pixel from adjacent subpixels in the array of LED pixels, wherein: for each normal LED pixel, the plurality of wells are configured such that the first colored subpixels, second colored subpixels, third colored subpixel, and fourth replacement subpixel are each isolated within one of the plurality of wells, and for each defective LED pixel in which one of the first, second, or third colored subpixels is determined to be a defective subpixel, the plurality of wells for the defective LED pixel are configured such that the defective subpixel is isolated with a fourth replacement subpixel within one of the plurality of wells, and the remaining colored subpixels of the defective LED pixel are each isolated within one of the plurality of wells; forming a first color conversion layer within each of the plurality of wells isolating at least the first colored subpixel of each LED pixel; forming a second color conversion layer within each of the plurality of wells isolating at least the second colored subpixel of each LED pixel; and forming a third color conversion layer within each of the plurality of wells isolating at least the third colored subpixel of each LED pixel.

2. The method of claim 1 , wherein, for each defective LED pixel in which one of the first, second, or third colored subpixels in the defective LED pixel is determined to be a defective subpixel, and is positioned diagonally from the fourth replacement subpixel in the defective LED pixel and adjacent to a fourth replacement subpixel of an adjacent LED pixel, the defective subpixel is isolated with the fourth replacement subpixel of the adjacent LED pixel within one of the plurality of wells.

3. The method of claim 1 , wherein detecting one or more defective subpixels comprises testing the array of micro-LED dies to detect one or more defective microLED dies.

4. The method of claim 3, wherein testing the array of micro-LED dies comprises determining one or more micro-LED dies that fail to generate any light, fail to generate light at a constant intensity, or fail to generate light at a target intensity.

5. The method of claim 1 , further comprising curing the first color conversion layer prior to forming the second color conversion layer, and curing the second color conversion layer prior to forming and curing the third color conversion layer.

6. The method of claim 1 , further comprising curing the first, second, and third color conversion layers by selectively activating the array of micro-LED dies.

7. The method of claim 1 , wherein the array of LED pixels comprises alternating first and second rows of LED pixels in which a position of the fourth replacement subpixel and a colored subpixel adjacent with the fourth replacement subpixel in each LED Pixel in first rows of LED pixels are switched in each LED pixel in second rows of LED pixels.

8. The method of claim 1 , wherein each subpixel is configured to be illuminated by one of the array of micro-LED dies.

9. The method of claim 1 , wherein forming the first color conversion layer within wells isolating the first colored subpixel and the fourth replacement subpixel of defective LED pixels together comprises concurrently forming the first color conversion layer on the first colored subpixel and the fourth replacement subpixel.

10. The method of claim 1 , wherein forming the second color conversion layer within wells isolating the second colored subpixel and the fourth replacement subpixel of defective LED pixels together comprises concurrently forming the second color conversion layer on the second colored subpixel and the fourth replacement subpixel for some of the defective LED pixels.11 . The method of claim 1 , wherein forming the third color conversion layer within wells isolating the third colored subpixel and the fourth replacement subpixel of defective LED pixels together comprises concurrently forming the third color conversion layer on the third colored subpixel and the fourth replacement subpixel for some of the defective LED pixels.

12. The method of claim 1 , further comprising forming a blocking layer on the array of the LED pixels after forming the first, second, and third color conversion layers.

13. The method of claim 1 , wherein the fourth replacement subpixel isolated with the defective subpixel in the defective LED pixel is operable to compensate for the defective subpixel by emitting light at a same wavelength as a color conversion layer formed for the defective subpixel.

14. The method of claim 1 , further comprising forming a microlens on at least one of the subpixels in each of the LED pixels.

15. A method of forming custom pixel isolation structures for a multi-color display device, comprising: providing an array of LED pixels, each of the LED pixels comprising a group of subpixels, and each group of subpixels comprising a first colored subpixel, a second colored subpixel, a third colored subpixel, and a fourth replacement subpixel; testing the array of LED pixels to detect one or more defective subpixels and identify normal LED pixels determined to not include a defective subpixel, and defective LED pixels determined to include at least one defective subpixel; and fabricating a plurality of features on the array of LED pixels to form a plurality of wells, each of the plurality of wells defined by one or more features of the pluralityfeatures, and each well isolating one or more subpixels of each LED pixel from adjacent subpixels in the array of LED pixels, wherein: for each normal LED pixel, the plurality of wells are configured such that each of the subpixels are isolated within one of the plurality of wells, and for each defective LED pixel in which one of the colored subpixels positioned adjacent to the fourth replacement subpixel is determined to be a defective subpixel, the plurality of wells for the defective LED pixel are configured such that the defective subpixel is isolated with the fourth replacement subpixel of the defective LED pixel within one of the plurality of wells, and the remaining subpixels of the defective LED pixel are each isolated within one of the plurality of wells; and for each defective LED pixel in which a colored subpixel positioned diagonally from the fourth replacement subpixel is determined to be a defective subpixel, the plurality of wells are configured such that the defective subpixel is isolated with a fourth replacement subpixel of an adjacent LED pixel within one of the plurality of wells, and the remaining non-defective subpixels of the defective LED pixel are each isolated within one of the plurality of wells.

16. The method of claim 15, wherein the array of LED pixels comprises alternating first and second rows of LED pixels in which the positions of the fourth replacement subpixel and one of the first, second, or third colored pixels that is adjacent to the fourth replacement subpixel in each LED pixel in first rows of LED pixels are switched in each corresponding LED pixel in second rows of LED pixels.

17. The method of claim 15, further comprising forming a coating over the plurality of features, the coating comprising a refractive material, a light shielding material, or other opaque material.

18. The method of claim 15, wherein the wells of the plurality of wells for isolating the defective subpixel and the fourth replacement subpixel together are about twice as large as the wells of the plurality of wells for isolating each of the subpixels of each LED pixel from adjacent subpixels in the array of LED pixels.

19. A multi-color display device, comprising:a backplane layer having backplane circuitry; a micro-LED layer bonded with and electrically integrated with the backplane circuitry, wherein the bonded layers comprise an array of LED pixels, each of the LED pixels comprising a group of subpixels having a first colored subpixel, a second colored subpixel, a third colored subpixel, and a fourth replacement subpixel; and a color conversion array coupled to the bonded layers, the color conversion array comprising a plurality of features and a plurality of wells, wherein each of the plurality of wells is defined by one or more features of the plurality of features, and each of the plurality of wells corresponding to and for isolating one or more subpixels of each LED pixel from adjacent subpixels in the array of LED pixels; and wherein: the array of LED pixels comprises normal LED pixels in which each of the subpixels function normally, and one or more defective LED pixels in which one of the first, second, or third colored subpixels is determined to be a defective subpixel, the plurality of wells for each normal LED pixel are formed such that the first, second, third, and fourth subpixels of each normal LED pixel are each isolated within one of the plurality of wells, and the plurality of wells for each of the one or more defective LED pixels are formed such that the defective subpixel is isolated with the fourth replacement subpixel of the defective LED pixel within one of the plurality of wells, and the remaining colored subpixels of the defective LED pixel are each isolated within one of the plurality of wells.

20. The multi-color display device of claim 19, wherein, the subpixels of each of the group of subpixels are arranged in a 2 x 2 matrix, and for each defective LED pixel in which the defective subpixel is positioned diagonal from the fourth replacement subpixel of the defective LED pixel, and adjacent to a fourth replacement subpixel of an adjacent LED pixel, the plurality of wells are formed such that the defective subpixel is isolated with the fourth replacement subpixel of the adjacent LED pixel within one of the plurality of wells.

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