How to form a display

Abstract

1. A method of forming a display, comprising: bonding a backplane comprising a plurality of backplane electrical contacts to a monolithic light-emitting diode structure comprising a corresponding plurality of electrical contacts, wherein the bonding comprises forming a reversible bond between at least one of the plurality of backplane electrical contacts and the corresponding electrical contact of the monolithic light-emitting diode structure; and removing material from the monolithic light-emitting diode structure to provide a plurality of physically isolated light-emitting diode dies, thereby enabling removal and / or replacement of the at least one physically isolated light-emitting diode die by reversing the reversible bond between at least one of the plurality of backplane electrical contacts and the corresponding electrical contact of the monolithic light-emitting diode structure.

Description

[Technical Field]

[0001] The present invention relates to the formation of displays. Specifically, but not exclusively, the present invention relates to monolithically based micro light emitting diode (LED) displays and methods of forming monolithically based micro LED displays with pixel replacement capabilities. [Background technology]

[0002] Light-emitting diode (LED) devices are known to provide highly effective and controllable light sources for display applications. Advantageously, packaging LED devices into micro LED arrays with small pixels at an ultra-fine pitch enables the fabrication of high-resolution displays. However, the presence of defective LED devices in such arrays can be problematic. Typically, to provide an acceptable display, the number of defective pixels (e.g., defective LED devices in a micro LED array) is preferably less than 2 defective pixels per 2 million pixels (i.e., a 99.9999% yield).

[0003] Such high yields can be difficult to achieve using known processes. To mitigate the impact of the presence of defective pixels in LED devices, it is known to implement redundancy schemes in which LED arrays are provided with backup devices to supply light to pixels in which any device failure exists. However, such redundancy schemes use additional space, thereby affecting the provision of densely packed small LED devices (dies) and therefore pixels in micro LED displays.

[0004] While monolithic growth of device arrays advantageously enables the provision of micro LED arrays with ultra-fine pitches, repair of any defective LED devices is difficult because the defective devices form part of the integrated structure. Accordingly, achieving monolithically formed ultra-fine micro LED arrays with sufficiently good pixel yields is challenging. Summary of the Invention [Means for solving the problem]

[0005] To mitigate the effects of at least some of the problems described above, a method of forming a display is provided that includes: bonding a backplane comprising a plurality of backplane electrical contacts to a monolithic light-emitting diode structure comprising a corresponding plurality of electrical contacts, wherein the bonding includes forming a reversible bond between at least one of the plurality of backplane electrical contacts and the corresponding electrical contact of the monolithic light-emitting diode structure; and removing material from the monolithic light-emitting diode structure to provide a plurality of physically isolated light-emitting diode dies, thereby enabling removal and / or replacement of the at least one physically isolated light-emitting diode die by reversing the reversible bond between at least one of the plurality of backplane electrical contacts and the corresponding electrical contact of the monolithic light-emitting diode structure.

[0006] Also provided is a display comprising a backplane comprising a plurality of backplane electrical contacts bonded to a plurality of physically isolated light emitting diode dies having electrical contacts, wherein at least one of the plurality of backplane electrical contacts is bonded to a corresponding electrical contact of the plurality of physically isolated light emitting diode dies using a reversible bond, thereby bonding the at least one backplane electrical contact to a corresponding electrical contact of the plurality of physically isolated light emitting diode dies. Reversing the reversible bond between the corresponding electrical contacts allows for removal and / or replacement of at least one physically isolated light emitting diode die, and multiple physically isolated light emitting diode dies are formed from the monolithic light emitting diode structure.

[0007] Advantageously, forming a display by bonding a backplane to a monolithic light emitting diode structure and removing material to form a reversible bond between at least one of the backplane electrical contacts and a corresponding electrical contact on the monolithic light emitting diode structure means that individual LED dies can be identified and replaced, thereby ensuring a sufficiently high yield of functional devices in the display without requiring space used for redundancy. Beneficially, high resolution displays can be provided with an array of light emitting pixels with the ability to replace individual light emitting diode device dies as needed.

[0008] Preferably, at least one of the backplane electrical contacts is reversibly bonded to a corresponding electrical contact of the monolithic light emitting diode structure using metal-metal and / or eutectic bonding. Advantageously, such bonding facilitates removal and replacement of the LED devices while providing electrical conductivity to form a functional device and a reflective surface to aid in light extraction from the individual LED devices.

[0009] Preferably, the method includes removing at least one physically isolated light emitting diode die and replacing the at least one physically isolated light emitting diode die with one or more different light emitting diode dies. Advantageously, the display is adapted to provide light emission from the individual light emitting devices in an array having a preferred configuration of light emitting properties.

[0010] Preferably, the method comprises removing the at least one physically isolated light emitting diode die by increasing the temperature of the display to enable removal of the at least one physically isolated light emitting diode die at a reversible junction between the backplane electrical contacts and corresponding electrical contacts associated with the monolithic light emitting diode structure, preferably wherein increasing the temperature of the display comprises increasing the temperature at the reversible junction above a eutectic temperature of the reversible junction, preferably wherein the reversible junction comprises at least one of an AuSn eutectic junction, a CuSn eutectic junction, and an InSn eutectic junction. Advantageously, a controllable method is presented that simultaneously enables electrical conductivity, reversible junction, and relatively high reflectivity for enhanced light extraction.

[0011] Preferably, removing the at least one physically isolated light emitting diode die includes overcoming the electrostatic force of a reversible junction, and preferably the electrostatic force of the reversible junction is at least one of an Au-Au metallic junction and a Cu-Cu metallic junction. Advantageously, a metal-metal junction can be provided that simultaneously enables electrical conductivity, reversible junction, and relatively high reflectivity for enhanced light extraction.

[0012] Preferably, the method includes testing at least one of the plurality of physically isolated light emitting diode dies, identifying one or more defective light emitting diode dies, removing the defective light emitting diode dies, and replacing the one or more removed light emitting diode dies. Advantageously, a display having a high yield of working devices is provided based on the monolithically grown LED device, thereby providing a high resolution display.

[0013] Preferably, the method includes forming a conformal metal layer on at least a portion of the physically isolated light emitting diode dies, thereby forming a conformal metal layer between the physically isolated light emitting diode dies. Advantageously, light extraction from the individual LED dies is improved, improving contrast between the pixels associated with the LED dies.

[0014] Preferably, the method includes forming a transparent conductive layer over a plurality of isolated light emitting diode dies, thereby providing a common electrode. Advantageously, multiple devices in the array are contacted simultaneously, thereby efficiently processing a large number of devices.

[0015] Preferably, the method includes facilitating removal of the physically isolated light emitting diode die by forming one or more magnetic metallic regions associated with at least one of the physically isolated light emitting diode die. Advantageously, the use of magnetic material enhances removal of the individual die, thereby overcoming any residual forces and aiding in the removal of the individual LED devices.

[0016] Preferably, at least one of the reversible junctions is at least partially surrounded laterally by a dielectric layer separating the backplane and the monolithic light-emitting diode structure, preferably the dielectric layer comprising at least one of SiO2, Si3N4, Su-8, SrF2, PDMS, and PMMA. Advantageously, the dielectric layer allows for uniform processing without interfering with removal of the individual LED dies.

[0017] Preferably, the contacts of the monolithic light emitting structure comprise a highly reflective metal, preferably one of nickel (Ni) and silver (Ag). Advantageously, such a metal assists in light extraction while simultaneously providing electrical conductivity.

[0018] Preferably, removing material from the monolithic light emitting diode structure includes forming a discontinuity in at least one layer of the monolithic light emitting diode structure, preferably the at least one layer of the monolithic light emitting diode structure is an n-type layer, more preferably the n-type layer is an n-doped gallium nitride layer. Advantageously, forming the discontinuity enables removal and replacement of individual, physically isolated die.

[0019] Further aspects of the present invention will become apparent from the specification and appended claims.

[0020] A detailed description of embodiments of the present invention will now be described, by way of example only, with reference to the drawings in which: [Brief explanation of the drawings]

[0021] [Figure 1A] The epitaxial crystal structure is shown. [Figure 1B] 1B shows the epitaxial crystalline structure of FIG. 1A processed to form a mesa. [Figure 1C] The structure of Figure 1B is shown further processed. [Figure 1D] The structure of Figure 1C is shown further processed. [Figure 1E] The structure of Figure ID is shown further processed. [Figure 2] 1 shows the processed backplane. [Figure 3A] 1E bonded to the backplane of FIG. 2. [Figure 3B] 3A structure is shown further processed. [Figure 3C] The structure of Figure 3B is shown further processed. [Figure 3D] 3C is shown further processed to remove the LED die. [Figure 4A] 3D structure with a replacement LED die. [Figure 4B] 4A is shown further processed. [Figure 4C]The structure of Figure 4B is shown further processed. [Figure 4D] The structure of FIG. 4C is shown further processed. [Figure 5] The structure of Figure 3B is shown further processed. DETAILED DESCRIPTION OF THE INVENTION

[0022] As noted above, while monolithically grown LED devices advantageously enable the fabrication of ultra-fine pitch micro LED displays for high resolution display applications, there are challenges associated with defective LED die in the display array. The following process and structure, described with reference to Figures 1-5, enable a repair and replacement process for monolithic micro LED displays that achieves the necessary yield requirements while avoiding the need to transfer large numbers of pixels, for example, by mass transfer pick-and-place based methods. The method and structure enable providing a display array of pixels, for example, each pixel having a light-emitting surface area of ​​100 μm 2 Less than 16 μm, preferably 2 and the pixel pitch is less than 10 μm, preferably less than 4 μm, and more preferably less than 3 μm.

[0023] While the methods and structures described herein are advantageously used to replace defective dies, in further embodiments, the methods and structures are used to provide dies formed in an array of monolithically grown LED devices with LED dies in the array configured to emit light of different wavelengths. For example, while it is known to provide highly efficient LED devices based on nitride materials configured to emit light having dominant peak wavelengths that are blue or green, providing red light using such materials is more challenging. For example, gallium arsenide (GaAs)-based materials are a more established technology for red-emitting LED dies. Thus, in one embodiment, the methods described herein are used to replace LED dies in a monolithically grown array of nitride-based LED dies to provide light of different wavelengths. Advantageously, the number of dies that would be transferred to the monolithically grown array is much smaller than the total number of dies in the array, providing a more efficient and practical method for forming high-resolution, multicolor micro LED arrays.

[0024] FIG. 1A illustrates a cross-sectional view of an epitaxial crystalline structure 100A. The epitaxial crystalline structure 100A is a structure formed from sequentially grown or deposited crystalline layers to provide a light-emitting structure. The epitaxial crystalline structure 100A is provided using metal-organic chemical vapor deposition (MOCVD). In further embodiments, alternative and / or additional methods of growth and / or deposition, such as molecular beam epitaxy (MBE), are used to provide the epitaxial crystalline structure 100A. Advantageously, the epitaxial crystalline structure 100A is provided in a sequential growth process and has high crystalline quality and low defect density. In further embodiments, the epitaxial crystalline structure 100A is provided using multiple growth steps that allow for the selective provision of specific properties, such as emission of different wavelengths due to radiative recombination of carriers from different regions of the epitaxial crystalline structure 100A.

[0025] In FIG. 1A , a growth substrate 102 is shown having an n-type region 104 grown thereon. The growth substrate 102 is a silicon substrate. Alternatively, in further embodiments, different materials are used to provide the growth substrate 102. The n-type region 104 is formed from n-type doped gallium nitride (GaN). In further embodiments, the n-type region 104 is formed from additional and / or alternative layers, such as an additional buffer layer. An active region 106 is shown above the n-type region 104. The active region 106 is configured to emit light following recombination of carriers injected from the n-type and p-type regions. The active region 106 includes a multiple quantum well (MQW) structure. In further embodiments, the active region includes a single quantum well (SQW) structure. The active region 106 is configured to emit light having a controlled primary peak wavelength. In further embodiments, different portions of the active region 106 are configured to emit light having different dominant peak wavelengths.

[0026] Above the active region 106 is shown a p-type region 108. The p-type region 108 is formed from p-type doped GaN. In further embodiments, the p-type region 108 is formed from additional and / or alternative layers.

[0027] The epitaxial crystal structure 100A is based on a III-V material (a III-nitride material, e.g., a GaN-based material). While the structure is shown to be a nitride-based structure, in further embodiments, different materials are used to provide a monolithic array of light emitting devices. While an n-type region 104, an active region 106, and a p-type region 108 are shown, those skilled in the art will understand that in further embodiments, additional and / or alternative layers are used to provide the epitaxial crystal structure 100A. Once the epitaxial crystal structure 100A is provided, as shown in FIG. 1A, it is processed to form a plurality of monolithically grown LED devices. This is shown in FIG. 1B. FIG. 1B shows a cross-sectional view of a processed structure 100B based on the epitaxial crystal structure 100A of FIG. 1A, with a mesa 110 formed.

[0028] Each of the mesas 110 includes portions of the p-type region 108 and the active region 106. The mesas 110 are shown formed on the n-type region 104. The mesas 110 are formed by selectively patterning and etching the epitaxial crystalline structure 100A using known techniques. Those skilled in the art will understand that, alternatively and / or additionally, the mesas 110 may be formed from different and / or additional layers.

[0029] Once mesa 110 is formed as shown in FIG. 1B, the process moves to FIG. 1C, where conformal layer 112 is deposited on mesa 110. FIG. 1C shows a cross-sectional view of processed structure 100C, which is a processed version of structure 100B of FIG. 1B. Conformal layer 112 is shown formed on mesa 110. Conformal layer 112 is deposited using known deposition techniques and is formed to avoid irreversible bonding with other layers at a later stage. Conformal layer 112 is a dielectric layer formed from silicon dioxide (SiO). Alternatively and / or additionally, in further embodiments, the conformal layer is a dielectric layer formed from a different material, for example, silicon nitride (SiN), a photoresist such as Su-8, strontium fluoride (SrF), polydimethylsiloxane (PDMS), or poly(methyl methacrylate) (PMMA). In a further embodiment, the final structure is bonded to a suitable material that allows for reversible bonding at the contact points without bonding the portion of conformal layer 112 that contacts the backplane, or any other suitable material.

[0030] Conformal layer 112 is further processed to provide contacts to p-type regions 108. This is shown in FIG. 1D , which illustrates a cross-sectional view of processed epitaxial structure 100D, which is a processed version of structure 100C described with respect to FIG. 1C . Structure 100C of FIG. 1C is processed to selectively pattern and etch windows through conformal layer 112, thereby exposing at least a portion of each of mesas 110 where p-type contacts to p-type regions 108 will be formed. Once the windows are provided, p-type contacts 114 are formed in the windows of mesas 110.

[0031] The electrical p-type contact 114 is formed from a metal. In one embodiment, the metal has a relatively high reflectivity. Advantageously, the use of a relatively high reflectivity electrical p-type contact 114 aids in light extraction from the individual LED dies formed based on the mesa 110 of the monolithically grown structure 100. The electrical p-type contact 114 is formed to enable metallurgical bonding (e.g., gold-gold (Au-Au) bonding or copper-copper (Cu-Cu) bonding) and eutectic bonding (gold-tin (Au-Sn), copper-tin (Cu-Sn), indium-tin (InSn)) to the backplane. Alternatively and / or additionally, in further embodiments, the electrical p-type contact 114 may be formed from a metal. 4 is formed from any suitable reflective and conductive material that can be used to form a reversible bond. In one embodiment, electrical p-type contact 114 is formed from nickel and / or silver. Electrical p-type contact 114 is used to form a reversible bond with a further backplane device and is therefore formed from a material that facilitates such a reversible bond, as will be described in more detail below.

[0032] Once electrical p-type contact 114 is formed on mesa 110 as shown in Figure 1D, the process moves to the process shown in Figure 1E, which shows a cross-sectional view of epitaxial structure 100E of Figure 1D after further processing to planarize the structure.

[0033] Accordingly, FIG. 1E shows material 116 deposited in the gaps formed between mesas 110, with the surface of the material planarized. Such planarization is achieved by depositing material 116 and chemical-mechanical polishing to form a flat surface suitable for bonding to further devices. In further embodiments, alternative and / or additional methods are used to planarize the opposite surface of growth substrate 102. Material 116 is a metal. In further embodiments, alternative and / or additional materials 116, such as a dielectric material, are used. Once structure 100E is provided, structure 100E is bonded to a backplane structure, as described below with reference to FIGS. 2 and 3.

[0034] FIG. 2 shows a processed backplane 200 that has been processed for reversible bonding to a monolithically grown LED array as described above with respect to FIG.

[0035] 2 shows a CMOS backplane 202 having a dielectric layer 204 deposited thereon. The dielectric layer 204 is processed to pattern and selectively etch windows, and material is deposited in the windows using known techniques to form electrical backplane contacts 206. The formation of the windows exposes portions of the CMOS backplane 202 to which p-type contacts can be connected to control light emission from individual LED devices in an array of LED devices. While the backplane 202 is a CMOS backplane 202, in further embodiments, additional and / or alternative backplanes may be used and bonded to LED-based structures to form a functional display.

[0036] The backplane contact 206 is designed to form a reversible bond with the electrical p-type contact 114 of the structure 100E shown in FIG. 1E. Accordingly, the backplane contact 206 is formed to enable metallic bonds (e.g., gold-gold (Au-Au) or copper-copper (Cu-Cu) bonds) and eutectic bonds (gold-tin (Au-Sn), copper-tin (Cu-Sn), indium-tin (InSn)). Accordingly, the combination of the materials used to form the p-type contact 114 of the structure 100E shown in FIG. 1E and the electrical backplane contact 206 is selected to provide a material combination that provides a reversible bond.

[0037] Dielectric layer 204 is formed from silicon dioxide. Alternatively and / or additionally, dielectric layer 204 is formed from silicon nitride, Su-8, SrF2, PDMS, PMMA, or any other suitable material. Dielectric layer 204 is formed to contact conformal layer 112, and accordingly, the objective is to prevent oxide-oxide combination during bonding so that dielectric layer 204 does not form an irreversible bond with conformal layer 112. Accordingly, the combination of materials used to form conformal layer 112 and dielectric layer 204 is selected to provide a material combination that provides a reversible bond at the electrical contact but not at other portions of the interface between processed backplane 200 and monolithically grown epitaxial structure 100E.

[0038] Once the processed backplane 200 and structure 100E are provided, they are bonded together, as shown in Figure 3A.

[0039] Structure 300A in FIG. 3A shows a cross-sectional view of structure 100E of FIG. 1E bonded to processed structure 200 of FIG. 2. Structure 100E and processed structure 200 are bonded using a thermal compression bonding technique. In further embodiments, additional and / or alternative techniques are used to bond structures 100E, 200. Accordingly, electrical p-type contact 114 is aligned with backplane contact 206 of processed backplane 200. While combined structure 300A is shown in cross-section, those skilled in the art will understand that this process can be used for a two-dimensional array of LED devices monolithically grown on a growth substrate 102 and bonded to a planar surface of processed backplane 200. The electrical p-type contact 114 of the monolithically grown LED array is positioned to coincide with the backplane contact 206 of backplane 200, thereby forming a reversible bond between the p-type contact 114 of the monolithically grown LED array and the backplane contact 206 of backplane 200.

[0040] Once backplane 200 is bonded to structure 100E, growth substrate 102 of epitaxial crystalline structure 100A is removed to provide structure 300A of FIG. 3A. This is shown in FIG. 3B. FIG. 3B shows structure 300B, which is structure 300A of FIG. 3A that has been processed to remove growth substrate 102. Once growth substrate 102 is removed, n-type region 104 is exposed and can be selectively patterned and etched using known techniques. This is shown in FIG. 3C.

[0041] FIG. 3C shows a cross-sectional view of structure 300C, which is structure 300B of FIG. 3B that has been further processed to selectively etch through n-type region 104, conformal layer 112, and planarization material 116, exposing at least a portion of dielectric layer 204 associated with backplane 200 through etched channels 302. Advantageously, such etching physically isolates the LED dies (and thus the associated pixels) associated with individual mesas 110 formed as described above in connection with FIG. 1B. This physical isolation of the LED dies results in discontinuous n-type regions 104, as etched channels 302 surround and physically isolate the individual LED dies. Advantageously, a monolithically grown array of LED devices is formed, enabling the provision of a high-resolution pixel array, while still allowing for individual isolation of the LED dies.

[0042] The physical isolation of the individual LED dies, each associated with a pixel, means that the individual pixels (or LED dies) are bonded to the backplane 202 via a bond between the backplane contacts 206 of the backplane and the electrical p-type contacts 114 of the LED dies. There is no significant bond between the dielectric layer 204 and the conformal layer 112 or between the planarization material 116 and the dielectric layer 204. The bond between the backplane contacts 206 of the backplane 200 and the electrical p-type contacts 114 of the LED dies is a reversible bond. That is, the bond can be broken to remove a die and reformed to bond a replacement die in the same place. Such a reversible bond can be a metal-metal bond formed by thermocompression bonding or a eutectic bond. In further embodiments, alternative and / or additional reversible bonds are formed using other suitable materials to provide a reversible conductive bond between the backplane 200 and the LED dies.

[0043] Once the individual dies are isolated, they can be tested to identify any faulty dies. Once identified, the faulty dies can be removed by breaking the reversible bond between the particular backplane contact 206 of the backplane and the associated p-type contact 114 of the associated faulty die / pixel. Such dies, once identified, can be removed by breaking the reversible bond between the particular backplane contact 206 of the backplane and the associated p-type contact 114 of the associated faulty die / pixel. This can be removed by pressing the ion beam into the cavity. This is shown in Figure 3D.

[0044] FIG. 3D shows a cross-sectional view of structure 300C of FIG. 3C further processed to provide structure 300D, with the central LED of FIG. 3C removed (304). Such removal is facilitated by heating the area of ​​backplane 200 associated with backplane contact 206 and electrical p-type contact 114 above a temperature threshold to allow separation of the LED die from backplane 200. Such a temperature threshold that allows separation of the LED die from backplane 200 is the eutectic temperature of the eutectic bond. In further embodiments, the temperature threshold is based on a different measurement, such as the melting point of the metal or other suitable temperature. If the bonding force between backplane contact 206 of backplane 200 and electrical p-type contact 114 of the LED device is sufficiently low, the defective die is removed by a suction process. In further embodiments, additional and / or alternative techniques are used to remove the selected LED die. Additionally, in further embodiments, plasma processing is used to remove any residual material left on the surface from the removal process. Once the defective die is removed, a replacement die can be deposited. This is shown in Figure 4A.

[0045] 4A shows a cross-sectional view of structure 400A, which is structure 300D of FIG. 3D , further processed to provide a replacement LED die 402. Replacement LED die 402 (including an n-type region, a p-type region, an active region, and a p-type contact 414) contacts backplane 202 via backplane contact 206 of backplane 200 and p-type contact 414 of replacement LED die 402, forming a eutectic bond between backplane contact 206 and p-type contact 414. LED die 402 has a conformal layer 404 thereon formed in a manner similar to conformal layer 112 of the monolithically grown structure described in connection with FIGS. 1-3 . While the bond is a eutectic bond, in further embodiments, alternative and / or additional bonding methods are used to secure LED die 402 of structure 400A.

[0046] 3D and 4A illustrate the replacement of a defective die. Additionally and / or alternatively, in further embodiments, an LED die may be removed in order to replace it with a different device. For example, to insert a red-emitting device (e.g., an AlInGaP-based red-emitting LED device) into such a monolithically grown array of light-emitting devices having high-quality blue- and / or green-emitting LED devices, where the method for forming the high-efficiency red-emitting LED is different from the method used to form the high-efficiency blue- and / or green-emitting LED devices. Advantageously, the number of replacement LED devices inserted to provide a multicolor-emitting array is significantly less than when forming an array of multicolor-emitting LED devices by pick-and-place techniques.

[0047] Once the replacement of the defective / unwanted die has been performed as shown in FIG. 4A, the process moves to FIG. 4B. In FIG. 4B, a cross-sectional view of structure 400A of FIG. 4A that has been processed to provide structure 400B of FIG. 4B is shown. Structure 400B includes a metallic conformal layer 406 deposited on structure 400A. This conformal layer 406 functions to reduce optical crosstalk between pixels associated with light-emitting device dies in a display array. Once metallic conformal layer 406 has been deposited in FIG. 4B, the process moves to FIG. 4C.

[0048] 4C, a cross-sectional view of structure 400C, which is structure 400D of FIG. 4B, is shown that has been further processed to anisotropically etch the metallic conformal layer 406. Such anisotropic etching results in metal remaining on the sidewalls of the light emitting die. Once this anisotropic etching is performed, filler material 408 is formed in the gaps between the LED devices. Such filler material 408 is deposited using known techniques and planarized using chemical mechanical polishing techniques. In a further embodiment, to planarize the n-type side of the devices in structure 400C, Once structure 400C is planarized, the process moves on to provide the structure shown in Figure 4D.

[0049] FIG. 4D shows a cross-sectional view of structure 400D, which is a structure relative to 400C of FIG. 4C that has been processed in turn to deposit a transparent conductive material layer 410. Such layer is formed from indium tin oxide (ITO). In a further embodiment, a different conductive transparent material is used instead and / or in addition. Transparent conductive material layer 410 allows for the formation of n-type contacts to the n-type regions 104 of multiple dies that are now isolated. In a further embodiment, alternative and / or additional layers are used, for example, metal tracks to assist current spreading.

[0050] Accordingly, a method is described for providing repair and / or replacement dies in an array of monolithically grown dies, in which a plurality of dies provide light sources at light-emitting surfaces associated with pixels driven by a CMOS backplane 202.

[0051] Those skilled in the art will appreciate that different and / or additional layers may be implemented throughout to provide advantageous functionality. For example, FIG. 5 illustrates how lift-off of selected dies may be enhanced. FIG. 5 illustrates structure 500, the structure of FIG. 3B, with additional magnetic material 502 formed in association with each die. Such magnetic material 502 (e.g., iron, nickel, cobalt) is deposited over a portion of each LED device associated with a pixel. In further embodiments, alternative and / or additional configurations are used to provide magnetic functionality associated with each die. After pixel isolation, magnetic material 502 is used to facilitate lift-off. Once repair and / or replacement of defective and / or unnecessary dies has been performed, magnetic material 502 is etched away to allow for further deposition of transparent conductive material 410, as described in connection with FIG. 4D.

[0052] Advantageously, the methods described herein enable repair of monolithic microdisplays, allowing for the achievement of necessary yield requirements. Additionally, the methods enable the deposition of different colored light-emitting LED devices onto a monolithic display, for example, the deposition of a red LED die onto a blue / green monolithic display.

[0053] Although the above process is shown in a particular order, in further embodiments, alternative and / or additional steps are provided to enable removal and replacement of LED die in an array of monolithically grown LED devices.

[0054] Although the epitaxial structures described herein are described with reference to n-type growth on a growth substrate occurring before the formation of the active and p-type regions, followed by the formation of a p-type contact on a mesa for connection to a backplane, those skilled in the art will appreciate that in further embodiments, this technique may be applied to structures formed differently, for example, structures based on a reversed growth sequence, and / or structures with additional or alternative layers, and / or structures in which an n-type contact is formed on a mesa to form a reversible junction at a corresponding contact on the backplane.

Claims

1. planarizing a backplane having a plurality of backplane electrical contacts to provide a first planar surface; planarizing a monolithic light emitting diode structure having a plurality of electrical contacts corresponding to the plurality of backplane electrical contacts of the backplane to provide a second planar surface; bonding the first planar surface to the second planar surface, the bonding including forming a reversible bond between at least one of the plurality of backplane electrical contacts and a corresponding electrical contact of the monolithic light emitting diode structure; subsequently, selectively etching the monolithic light emitting diode structure to provide a plurality of physically isolated light emitting diode dies, thereby enabling removal and / or replacement of at least one physically isolated light emitting diode die by reversing the reversible bond between the at least one of the plurality of backplane electrical contacts and the corresponding electrical contact of the monolithic light emitting diode structure; A method of forming a display comprising:

2. 10. The method of claim 1, wherein the at least one of the backplane electrical contacts is reversibly bonded to the corresponding electrical contact of the monolithic light emitting diode structure using a metal-metal bond and / or a eutectic bond.

3. removing at least one physically isolated light emitting diode die; replacing the at least one physically isolated light emitting diode die with one or more different light emitting diode dies; 3. The method of claim 1 or 2, comprising:

4. 4. The method of claim 3, wherein removing at least one physically isolated light emitting diode die comprises increasing a temperature of the display to enable removal of the at least one physically isolated light emitting diode die in the reversible bond between the backplane electrical contacts and the corresponding electrical contacts associated with the monolithic light emitting diode structure.

5. testing at least one of the plurality of physically isolated light emitting diode dies; Identifying one or more defective light emitting diode dies; Removing defective light emitting diode dies; replacing one or more of the removed defective light emitting diode dies; and The method according to any one of claims 1 to 4, comprising:

6. forming a conformal metal layer over at least a portion of the physically isolated light emitting diode dies, thereby reducing optical crosstalk between the physically isolated light emitting diode dies; The method according to any one of claims 1 to 5, comprising:

7. forming a transparent conductive layer over the plurality of physically isolated light emitting diode dies; The method according to any one of claims 1 to 6, comprising:

8. forming one or more magnetic metallic regions associated with at least one of the physically isolated light emitting diode dies to facilitate removal of the physically isolated light emitting diode dies; The method according to any one of claims 1 to 7, comprising:

9. 9. The method of claim 1, wherein at least one of the reversible junctions is at least partially surrounded laterally by a dielectric layer, thereby separating the backplane and the monolithic light-emitting diode structure.

10. The method of any one of claims 1 to 9, wherein the plurality of electrical contacts of the monolithic light emitting diode structure comprise a highly reflective metal.

11. The method of any one of claims 1 to 10, wherein removing material from the monolithic light emitting diode structure comprises forming a discontinuity in at least one layer of the monolithic light emitting diode structure.

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