Integration of microdevices into system substrate

Abstract

In the microdevice integration process, a donor substrate is provided on which initial fabrication and pixelation steps are performed to define the microdevice, which includes a functional layer, such as a light-emitting layer, sandwiched between a top conductive layer and a bottom conductive layer. The microdevice is then transferred to a system substrate for finalization and electronic control integration. This transfer can be facilitated by various means, including providing continuous light-emitting functional layers, destructible anchors on the donor substrate, temporary intermediate substrates for implementing heat transfer technologies, or temporary intermediate substrates with destructible substrate bonding layers.

Description

[Technical Field]

[0001] This invention relates to optoelectronic microdevices, and more particularly to integrating optoelectronic microdevices into a system substrate with enhanced bonding and conductivity. [Previous Technology]

[0002] The object of the present invention is to overcome the disadvantages of the prior art by providing a system and method for transferring a microdevice from a donor substrate to a system substrate. [Summary of the Invention]

[0003] According to one embodiment of the present invention, a method for manufacturing a pixelated structure includes: providing a donor substrate; depositing a first conductive layer on the donor substrate; depositing a fully or partially continuous light-emitting functional layer on the first conductive layer; depositing a second conductive layer on the functional layer; patterning the second conductive layer to form a pixelated structure; providing bonding contacts for each pixelated structure; fixing the bonding contacts to a system substrate; and removing the donor substrate.

[0004] In one embodiment, the microdevice is made into an array using sequential pixelation.

[0005] In another embodiment, the device is separated and transferred to an intermediate substrate by filling the gaps between the microdevices.

[0006] In another embodiment, the microdevice is post-processed after being transferred to an intermediate substrate.

[0007] According to one embodiment, a bonding structure may be provided. The bonding structure may include a plurality of microdevices on a donor substrate, wherein each microdevice includes one or more conductive pads formed on the surface of the microdevice; and a temporary material covers at least a portion of each microdevice or the one or more conductive pads. In one case, the temporary material acts as an anchor, securing the plurality of microdevices within a housing structure in the donor substrate.

[0008] According to one embodiment, a method for integrating microdevices on a backplane may be provided, the method comprising: providing a microdevice substrate comprising one or more microdevices; connecting pads on the microdevices to corresponding pads on the backplane to bond a set of selective microdevices from the substrate to the backplane; and separating the microdevice substrate to leave the selected set of bonded microdevices on the backplane.

Implementation Method

[0094] Cross-Reference to Related Applications This application is a partial continuation-in-place of and claims priority to U.S. Application No. 15 / 820,683, filed November 22, 2017, which claims priority and interest in the following applications: U.S. Provisional Patent Application No. 62 / 426,353, filed November 25, 2016; U.S. Provisional Patent Application No. 62 / 473,671, filed March 20, 2017; U.S. Provisional Patent Application No. 62 / 482,899, filed April 7, 2017; and U.S. Provisional Patent Application No. 62 / 515,185, filed June 5, 2017; and Canadian Patent Application No. 2,984,214, filed October 30, 2017, each of which is incorporated herein by reference in its entirety.

[0095] This application also claims the benefit of U.S. Provisional Patent Application No. 62 / 734,679, filed September 21, 2018, and U.S. Provisional Patent Application No. 62 / 809,161, filed February 22, 2019, which are incorporated herein by reference in their entirety.

[0096] This application further claims the benefit of U.S. Provisional Patent Application No. 62 / 746,300, filed on October 16, 2018, which is incorporated herein by reference in its entirety.

[0097] Although the teachings of the present invention have been described in conjunction with various embodiments and examples, the teachings of the present invention are not intended to be limited to these embodiments. Rather, the teachings of the present invention cover various alternatives and equivalents, as will be understood by those skilled in the art.

[0098] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art.

[0099] As used in this specification and the claims, unless the context clearly indicates otherwise, the singular forms "a / an" and "the" include multiple referents.

[0100] In this specification, the terms "device," "vertical device," and "microdevice" are used interchangeably. However, those skilled in the art will understand that the embodiments described herein are independent of device size.

[0101] In this specification, the terms "donor substrate" and "temporary substrate" are used interchangeably.

[0102] In this specification, the terms "receptor substrate", "system substrate" and "backplate" are used interchangeably.

[0103] Examples of optoelectronic devices are sensors and light-emitting devices, such as light-emitting diodes (LEDs).

[0104] This invention relates to a microdevice array display device, wherein the microdevice array can be reliably bonded to a backplane. Microdevices can be fabricated on a microdevice substrate. The microdevice substrate may include microLEDs, inorganic LEDs, organic LEDs, sensors, solid-state devices, integrated circuits, microelectromechanical systems (MEMS), and / or other electronic components.

[0105] LEDs and LED arrays can be classified as vertical solid-state devices. Microdevices can be sensors, LEDs, or any other solid-state devices grown, deposited, or integrally fabricated on a substrate. The substrate can be an inherent substrate or a acceptor substrate to which a device layer or solid-state device is transferred.

[0106] The acceptor substrate can be any substrate and can be rigid or flexible. The acceptor substrate may include (but is not limited to) a printed circuit board, a thin-film transistor (TFT) backplane, an integrated circuit substrate, or, in the case of an optical microdevice such as an LED, a component of a display such as a driver circuit backplane. The microdevice patterning on the device donor and acceptor substrates can be used in combination with different transfer techniques, such as gripping and placing, that have different mechanisms (e.g., electrostatic transfer heads, elastomeric transfer heads) or direct transfer mechanisms (e.g., dual-function pads).

[0107] In this invention, contact pads in the recipient substrate refer to designated areas in the recipient substrate to which the microdevice is transferred. Contact pads may include bonding material that permanently holds the microdevice. Contact pads may be stacked in multiple layers to provide a mechanically more stable structure with improved bonding and conductivity.

[0108] The system substrate may be made of glass, silicon, plastic, or any other commonly used material. The system substrate may also have active electronic components, such as (but not limited to) transistors, resistors, capacitors, or any other electronic components commonly used in system substrates. In some cases, the system substrate may be a substrate with columns and rows of electrical signals. The system substrate may be a backplane with circuitry for routing the microLED device.

[0109] FIG1A illustrates an embodiment of a donor substrate 110 having a lateral functional structure, which includes a bottom planar or sheet-like conductive layer 112; a functional layer 114, such as a light-emitting quantum well; and a top pixelated conductive layer 116. The conductive layers 112 and 116 may be composed of doped semiconductor materials or other suitable types of conductive layers. The top conductive layer 116 may include several different layers. In one embodiment, as shown in FIG1B, a current distribution layer 118 is deposited on top of the conductive layer 116. The current distribution layer 118 can be patterned. In one embodiment, it can be patterned by lift-off. In another, it can be patterned by photolithography. In an embodiment, a dielectric layer can be deposited and patterned first, and then used as a hard mask to pattern the current distribution layer 118. After patterning the current distribution layer 118, the top conductive layer 116 can also be patterned to form a pixel structure. After patterning the current distribution layer 118 and / or the conductive layer 116, a final dielectric layer 120 may be deposited over and between the patterned conductive layer 116 and the current distribution layer 118, as shown in FIG1C. The dielectric layer 120 may also be patterned to create an opening 130 as shown in FIG1D to provide a path to the current distribution layer 118. An additional leveling layer 128 may also be provided to flatten the upper surface, as shown in FIG1E.

[0110] As shown in FIG1E, pads 132 are deposited on top of the current distribution layer 118 in each opening 130. The resulting structure with pads 132 is bonded to a system substrate 150 with pads 154, as shown in FIG1F. The pads 154 in the system substrate 150 can be separated by a dielectric layer 156. Other layers 152, such as circuitry, planarization layers, and conductive traces, may exist between the system substrate pads 154 and the system substrate 150. The system substrate pads 154 can be bonded to the pads 132 by fusion bonding, anodic bonding, thermoforming bonding, eutectic bonding, or adhesive bonding. One or more other layers may also be deposited between the system device and the side device.

[0111] As shown in FIG1G, the donor substrate 110 can be removed from the lateral functional device, such as the conductive layer 112. The conductive layer 112 can be thinned and / or partially or completely patterned. A reflective layer or black matrix 170 can be deposited and patterned to cover the area between pixels on the conductive layer 112. After this stage, other layers can be deposited and patterned according to the function of the device. For example, a color conversion layer can be deposited to adjust the color of the light generated by the lateral devices and pixels in the system substrate 150. One or more color filters can also be deposited before and / or after the color conversion layer. The dielectric layer in these devices, such as dielectric layer 120, can be an organic material such as polyamide or an inorganic material such as SiN, SiO2, Al2O3. This deposition can be performed using different processes, such as plasma-enhanced chemical vapor deposition (PECVD), atomic layer deposition (ALD), and other methods. Each layer can be a single deposition material or a combination of different materials deposited alone or together. The bonding material can be deposited only as a portion of the pads 132 of the donor substrate 110 or the pads 154 of the system substrate. For some of these layers, an annealing process may also be performed. For example, the current distribution layer 118 may be annealed depending on the material. In one example, the current distribution layer 118 may be annealed at 500°C for 10 minutes. Annealing may also be performed after different steps.

[0112] FIG. 2A illustrates an exemplary embodiment of a donor substrate 210 with a lateral functional structure, which includes a first top planar or sheet-like conductive layer 212; a functional layer 214, such as a light-emitting layer; a second bottom pixelated conductive layer 216; a current distribution layer 218; and / or a bonding pad layer 232. FIG. 2B illustrates all or one of the patterned layers 216, 218, and 232 to form a pixel structure. The conductive layers 212 and 216 may be composed of multiple layers including highly doped semiconductor layers. Some layers 228, such as dielectrics, may be used between the patterned layers 216, 218, and 232 to flatten the upper surface of the lateral functional structure, as shown in FIG. 2C. Layers 228 may also have other functions, such as a black matrix. The resulting structure with pads 232 is bonded to a system substrate 250 with substrate pads 254, as shown in FIG. 2D. The pads 254 in the system substrate may also be separated by a dielectric layer 256. Other layers 252, such as circuitry, planarization layers, and conductive traces, may exist between the system substrate pads 254 and the system substrate 250. This bonding may be performed, for example, by fusion bonding, anodic bonding, thermoforming bonding, eutectic bonding, or adhesive bonding. Other layers may also be deposited between the system device and the side device.

[0113] The donor substrate 210 can be removed from the lateral functional device. The conductive layer 212 can be thinned and / or patterned. A reflective layer or black matrix 270 can be deposited and patterned to cover the area between pixels on the conductive layer 212. After this stage, other layers can be deposited and patterned according to the function of the device. For example, a color conversion layer can be deposited to adjust the color of the light generated by the lateral devices and pixels in the system substrate 250. One or more color filters can also be deposited before and / or after the color conversion layer. The dielectric layers in these devices, such as 228 and 256, can be organic materials such as polyamide or inorganic materials such as SiN, SiO2, Al2O3. This deposition can be performed using different processes, such as PECVD, ALD, and other methods. Each layer can be a single deposition material or a combination of different materials deposited alone or together. The material of the bonding pads 232 can be deposited as part of the pads 232 of the donor substrate 210 or the system substrate pads 254. For some of these layers, an annealing process may also be performed. For example, the current distribution layer 218 may be annealed depending on the material. In one example, the current distribution layer may be annealed at 500°C for 10 minutes. Annealing may also be performed after different steps.

[0114] In another embodiment shown in FIG. 3A, a mesa structure is formed on the donor substrate 310. A microdevice structure is formed by etching through different layers, such as a first bottom conductive layer 312, a functional layer 314, and a second top conductive layer 316. Top contacts 332 may be deposited before or after etching on top of the top conductive layer 316. In another case, multilayer contacts 332 may be used. In this case, a portion of the contact layer 332 may be deposited before etching, and a portion of the contact layer may be deposited after etching. For example, an initial contact layer may be deposited first to create ohmic contacts by annealing the conductive layer 316. In one example, the initial contact layer may be gold or nickel. Other layers 372, such as dielectric or metal insulator (MIS) structures, may also be used between the mesa structures to isolate and / or insulate each structure. After the microdevice is formed, a filler layer 374, such as polyamide, may be deposited, as shown in FIG. 3B. If the selected microdevice is transferred only to the cassette (temporary) substrate 376 during the subsequent steps, the filler layer 374 can be patterned. Alternatively, the filler layer 374 can be deposited after the device has been transferred to the temporary substrate. The filler layer 374 can act as a housing for the microdevice. Using the filler layer 374 prior to the transfer may make the peeling process more reliable.

[0115] The device is bonded to a temporary substrate (cassette) 376. For example, the bonding source may vary and may include one or more of the following: electrostatic bonding, electromagnetic bonding, adhesive bonding, van der Waals force bonding, or thermal bonding. For thermal bonding, a substrate bonding layer 378 with a melting temperature of T1 may be used. The bonding layer 378 may be conductive or may include a conductive layer and a bonding layer, which may be adhesive bonding, thermal bonding, or photo-assisted bonding. The conductive layer may be used to bias the device on the substrate 376 to identify defects and characterize device performance. This structure may be used in other embodiments presented herein. To address certain surface profile inhomogeneities, pressure may be applied during the bonding process. The temporary substrate 376 or the donor substrate 310 may be removed, leaving the device on either one. The process explained herein is based on leaving the device on the temporary substrate 376; however, similar steps may be used when the device is left on the donor substrate 310. Following this, additional processes can be performed on the microdevice, such as thinning the device, creating a contact bonding layer 380 on the bottom conductive layer 312, or removing the filler layer 374. The device can then be transferred to the system substrate 390, as shown in Figures 3D and 3E. This transfer can be performed using different techniques. In one case, thermal bonding is used for the transfer. In this case, the melting point of the contact bonding layer 380 on the system substrate contact pads 382 is T2, where T2 > T1. Here, a temperature higher than T2 will melt both the substrate bonding layer 378 and the contact bonding layer 380 on the pads 382.

[0116] In the subsequent steps, the temperature drops to between T1 and T2. At this time, the device is bonded to the system substrate 390 via the contact bonding layer 380, causing the contact bonding layer 380 to solidify, but the substrate bonding layer 378 to melt. Therefore, the temporary substrate 376 is moved to leave the microdevice on the system substrate 390, as shown in FIG3E. This process can be made selective by applying localized heating to the selected pads 382. Moreover, in addition to localized heating, a global temperature can be used, for example, by placing the substrates 376 and 390 in an oven and performing the process by increasing the overall atmosphere therein, thereby increasing the transfer speed. Here, the global temperature on the temporary substrate 376 or the system substrate 390 can be such that the temperature is close to the melting point of the contact bonding layer 380, for example, between 5°C and 10°C lower than the melting point, and the localized temperature can be used to melt the contact bonding layer 380 and the substrate bonding layer 378 corresponding to the selected device. In another case, the temperature can be raised to near the melting point of the substrate bonding layer 378 (higher than the melting point of the contact bonding layer 378), for example, between 5°C and 10°C lower than that melting point, and for the device in contact with the heated pad 382, ​​the selected area of ​​the substrate bonding layer 378 is melted by the temperature transfer from the pad 382 by the device.

[0117] Figure 3F shows an example of a thermal profile, where the melting temperature Tr melts the contact bonding layer 380 and the substrate bonding layer 378, and the curing temperature Ts cures the contact bonding layer 380 with the bonding pads 382 while the substrate bonding layer 378 remains melted. Melting can be localized or can at least soften the bonding layers enough to release the microdevice or activate the alloying process. Other forces can also be used, either in combination or individually, to hold the device to the bonding pads 382. In another case, the temperature profile can be generated by applying a current through the device. Because the contact resistance will be high before bonding, the power dissipated on the bonding pads 382 and the device will be high, thus melting the contact bonding layer 380 and the substrate bonding layer 378. As bonding forms, the resistance will decrease, and the power dissipation will also decrease, thereby lowering the local temperature. The voltage or current through the pads 382 can be used to indicate the bonding quality and when to stop the process. The donor substrate 310 and the temporary substrate 376 may be the same or different. After the device is transferred to the system substrate 390, different process steps can be performed. These additional processing steps may include planarization, electrode deposition, color conversion deposition and patterning, color filter deposition and patterning, etc.

[0118] In another embodiment, the temperature for releasing the microdevice from the cartridge substrate 376 increases as alloy formation begins. In this case, the temperature can be kept constant as the bonding alloy forms on the bonding pads 382 of the acceptor substrate 390 and the bonding layer solidifies, thereby keeping the microdevice in the proper position on the acceptor substrate 390. Simultaneously, the bonding layer 378 on the cartridge 376 connected to the selected microdevice remains melted (or sufficiently soft) to release the device. Here, a portion of the material required for alloy formation may be on the microdevice, and another portion may be deposited on the bonding pads 382.

[0119] In another embodiment, a filler layer 374 may be deposited on top of the cartridge substrate 376 to form a polymer filler / bonding layer 374 / 378. A microdevice from the donor substrate 310 may then be pushed into the polymer filler / bonding layer 374 / 378. The microdevice may then be selectively or generally separated from the donor substrate 310. The polymer filler / bonding layer 374 / 378 may be cured before or after separating the microdevice from the donor substrate 310. The polymer filler / bonding layer 374 / 378 may be patterned, particularly when multiple different devices are integrated into the cartridge substrate 376. In this case, the polymer filler / bonding layer 374 / 378 may be created for one type, with the microdevice embedded in the layer and separated from its donor 310. Then, another polymer filler / bonding layer 374 / 378 is deposited and patterned for the next type of microdevice. Next, a second microdevice can be embedded in the associated layers 374 / 378. In all cases, the polymer filler / bonding layers 374 / 378 may cover part or all of the device in the microdevice.

[0120] Another method of increasing temperature may be by using microwaves or lamps. Therefore, a layer may be deposited on: bonding pads 382; a portion of pads 382; a microdevice; or a portion of the housing 376 that absorbs microwaves or light and locally heats the microdevice. Alternatively, the housing 376 and / or the acceptor substrate 390 may include heating elements that selectively and / or globally heat the microdevice.

[0121] Other methods may also be used to separate the microdevice from the temporary substrate 376, such as chemical, optical, or mechanical forces. In one example, a sacrificial layer may be used to cover the microdevice, which may be debonded to the temporary substrate 376 by chemical, optical, thermal, or mechanical forces. The debonding process may be selective or global. Global debonding transfer to the system substrate 390 is selective. If the debonding process between the device and the temporary substrate (cassette) 376 is selective, a transfer force may be applied selectively or globally to the system substrate 390.

[0122] The transfer process from the cartridge 376 to the acceptor substrate 390 can be based on different mechanisms. In one case, the cartridge 376 has a bonding material that releases the device in the presence of light, while the same light cures the bond between the device and the acceptor substrate.

[0123] In another embodiment, the temperature of the bonding layer 380 used to solidify the device to the recipient substrate 390 causes the device to be released from the cartridge 376.

[0124] In another case, a current or voltage cures the bonding layer 380 of the device to the donor substrate 310. The same current or voltage can release the device from the housing 376. Here, release can be a function of the piezoelectric effect generated by the current or temperature.

[0125] In another method, after the bonding of the curing device to the acceptor substrate 390, the bonded device is pulled out from the housing 376. Here, the force holding the device to the housing 376 is less than the force bonding the device to the acceptor substrate 390.

[0126] In another method, the cartridge 376 has a via that can be used to push a device out of the cartridge 376 and into the receiver substrate 390. This pushing can be performed in different ways, such as using an array of microrods or by pneumatic means. For a pneumatic structure, the selected device is disconnected. For microrods, the selected device is moved toward the receiver substrate 390 by passing the microrods through the associated vias of the selected device. The microrods can be at different temperatures to facilitate transfer. After the transfer of the selected device is complete, the microrods are retracted, and the same rods are aligned with the vias of another set of microdevices, or a new device is transferred using a set of vias aligned with a new selected microdevice.

[0127] In one embodiment, the cartridge 376 can be stretched to increase the device spacing within the cartridge 376 to improve throughput. For example, if the cartridge 376 is 1 × 1 cm², with a device spacing of 5 micrometers, and the pixel spacing of the receiver substrate 390 (e.g., a display) is 50 micrometers, then the cartridge 376 can fill 200 × 200 (40,000) pixels at a time. However, if the cartridge 376 is stretched to 2 × 2 cm², with a device spacing of 10 micrometers, then the cartridge 376 can fill 400 × 400 (160,000) pixels at a time. In another case, the cartridge 376 can be stretched such that at least two microdevices on the cartridge 376 become aligned with two corresponding locations in the receiver substrate. This stretching can be performed in one or more directions. The cartridge substrate 376 may comprise or be composed of a stretchable polymer. The microdevices are also fixed in another layer or in the same layer as the cartridge substrate 376.

[0128] The combination of methods described above can also be used to transfer the microdevice from the cassette 376 to the receptor substrate 390.

[0129] During the generation of the cell (temporary substrate) 376, the microdevice can be tested to identify various defects and device performance. In one embodiment, the device can be biased and tested before the top electrode is separated. If the device is an emitting device, a camera (or sensor) can be used to extract defects and device performance. If the device is a sensor, stimulation can be applied to the device to extract defects and performance. In another embodiment, the top electrode 332 can be patterned into groups for testing before being patterned into individual devices. In another instance, a temporary common electrode is deposited or coupled to the device between more than one device to extract device performance and / or extract defects.

[0130] The methods described above with respect to Figures 3A-3D—including, but not limited to, separation, forming of packing layers, different functions of packing layers, testing, and other structures—can be used in other structures that include the structures described below.

[0131] The method for transferring a microdevice from a cassette (temporary substrate) 376 to a receiver substrate 390, as discussed herein, can be applied to all cassette and receiver substrate configurations presented herein.

[0132] The device on the donor substrate 310 may be configured to have two contacts 332 and 380 on the same side opposite to the donor substrate 310. In this embodiment, the conductive layer on the cartridge 376 may be patterned to independently bias the two contacts 332 and 380 of the device. In one case, the device may be transferred directly from the cartridge substrate 376 to the recipient substrate 390. Here, the contacts 332 and 380 may not be directly bonded to the recipient substrate 390, i.e., the recipient substrate 390 does not need to have special pads. In this case, the conductive layer is deposited and patterned to connect the contacts 332 and 380 to appropriate connections in the recipient substrate 390. In another embodiment, the device may be transferred from the cartridge 376 to a temporary substrate before being transferred to the recipient substrate 390. Here, the contacts 332 and 380 may be directly bonded to the recipient substrate pad 382. The device may be tested in the cartridge 376 or in the temporary substrate.

[0133] In another embodiment shown in FIG4A, a mesa structure as described above is formed on a donor substrate, wherein a microdevice structure is formed by etching through different layers, such as a first bottom conductive layer 412; a functional layer 414, such as a light-emitting layer; and a second top conductive layer 416. Top contacts 432 may be deposited before or after etching on top of the top conductive layer 416.

[0134] The temporary substrate 476 includes a plurality of trenches 476-2 initially filled with a filler material, such as a soft material like a polymer or a solid material like SiO2 or SiN. The trenches 476-2 are located below the surface and / or substrate bonding layer 478. A device is transferred to the temporary substrate 476 on top of the trenches 476-2, and the device includes contact pads 432. Moreover, each microdevice may include additional passivation layers and / or MIS layers 472 surrounding each microdevice for isolation and / or protection. The space between devices may be filled with filler material 474. After post-processing of the device, another lower contact pad 480 may be deposited on the opposite surface of the device. The contact layer 412 may be thinned before depositing the lower contact pad 480. The filler material 474 may then be removed, and the trenches may be emptied by various suitable methods such as chemical etching or evaporation to induce or facilitate the release of the surface and / or selected sections of the bonding layer 478. A process similar to that described above can be used to transfer the device to the system (recipient) substrate 490. Alternatively, in another embodiment, a force applied from the pad 432, such as a push or pull, may disrupt the surface above the emptied slot 476-2 and / or the bonding layer 478, while maintaining the unselected mesa structure attached to the temporary substrate. This force can also release the device from the temporary substrate 476, as shown in Figures 4B and 4C. The depth of the slot 476-2 can be selected to manage some microdevice height difference. For example, if the height difference is H, the depth of the slot can be greater than H.

[0135] The device on substrate 310 can be configured to have two contacts 432 and 480 on the same side opposite to substrate 310. In this case, the conductive layer on cartridge 476 can be patterned to independently bias the two contacts of the device. In one case, the device can be transferred directly from cartridge substrate 476 to recipient substrate. Here, contacts 432 and 480 will not be directly bonded to the recipient substrate (the recipient substrate does not need to have special pads). In this case, the conductive layer is deposited and patterned to connect contacts 432 and 380 to appropriate connections in the recipient substrate. In another case, the device can be transferred from cartridge 476 to temporary substrate before being transferred to the recipient substrate. Here, contacts 432 and 480 can be directly bonded to the recipient substrate pads. The device can be tested in the cartridge or in the temporary substrate.

[0136] In another embodiment shown in FIG. 5A, a mesa structure as described above is formed on the donor substrate 510, wherein a microdevice structure is formed by etching through different layers, such as a first bottom conductive layer 512; a functional layer 514, such as a light-emitting layer; and a second top conductive layer 516. Top contact pads 532 may be deposited before or after etching on top of the top conductive layer 516. Furthermore, each microdevice may include additional passivation layers and / or MIS layers 572 surrounding each microdevice for isolation and / or protection. In this embodiment, the device may be provided with different anchors, whereby the anchors hold the device to the donor substrate 510 after the device is stripped. This stripping may be performed by laser. In an example, the laser scans only the device. In an embodiment, a mask may be used, which has an opening for the device only on the back side of the donor substrate 510 to block lasers from other areas. The mask may be separate from the donor substrate 510 or may be part of the donor substrate. In another case, another substrate may be attached to the device to hold it in place prior to the peeling process. In yet another case, a filler layer 574, such as a dielectric, may be used between the devices.

[0137] In the first illustrated embodiment, layer 592 provides for securing the device to the donor substrate 510. Layer 592 may be a separate layer or a portion of the microdevice layer that was not etched during the formation of the mesa structure. In another embodiment, layer 592 may be a continuation of one of layers 572. In this case, layer 592 may be a metal layer or a dielectric layer (SiN or SiO2 or other materials). In another embodiment, the anchor is formed as a separate structure including extension 594, void / gap 596, and / or bridge 598. Here, a sacrificial layer with the same shape as the void / gap 596 is deposited and patterned. The anchor layer is then deposited and patterned to form bridge 598 and / or extension 594. The sacrificial material may later be removed to create void / gap 596. Extension 594 may also be avoided. Similar to the previous anchor 592, another anchor may be composed of a different structural layer. In another embodiment, filler layer 574 acts as the anchor. In this case, the fill layer 574 can be etched or patterned, or left as is.

[0138] Figure 5B shows a sample after the filler layer 574 has been removed and / or the filler layer has been etched to form an anchor. In another case, after peeling, the adhesive force of the bridging layer 598 is sufficient to hold the device in place and act as an anchor. For illustrative purposes only, the final device shown on the right side of Figure 5B is shown in a substrate 510. One or a combination of the devices may be used in the substrate.

[0139] As shown in Figure 5C, the anchor may cover at least a portion of the perimeter of the device or the entire perimeter of the device, or may be patterned to form arms 594 and 592. Either of these structures may be used in any anchoring structure.

[0140] Figure 5D illustrates an example of transferring the device to the recipient substrate 590. Here, the microdevice is bonded to pad 582 or placed in a predetermined area without any pads. Pressure or separation force can be used to release the anchor by breaking it. Alternatively, temperature can be used to release the anchor. The viscosity of the layer between the microdevice peel and the donor substrate 510 can be increased by controlling the temperature to act as an anchor. Figure 5E illustrates the device after it has been transferred to the recipient substrate 590 and shows possible release points 598-2 in the anchor. The anchor can also be directly or indirectly attached to the donor substrate 510 via other layers.

[0141] The device on the donor substrate 510 may be configured to have two contacts 532 and 480 on the same side opposite to the donor substrate 510. In one case, the device may be transferred directly from the donor substrate 510 to the recipient substrate 590. Here, the contacts 532 and 480 may be directly bonded to the recipient substrate pads 582. The device may be tested in the donor substrate 510 or in a cassette. In another embodiment, the device may be transferred from the donor substrate 510 to a cassette substrate before being transferred to the recipient substrate 590. Here, the contacts 532 will not be directly bonded to the recipient substrate 590, i.e., the recipient substrate 590 does not need to have special pads 582. In this case, a conductive layer is deposited and patterned to connect the contacts 532 to appropriate connections in the recipient substrate 590.

[0142] System substrates or acceptor substrates 390, 490, and 590 may include micro-LEDs, organic LEDs, sensors, solid-state devices, integrated circuits, MEMS (microelectromechanical systems), and / or other electronic components. Other embodiments relate to the patterning of pixel arrays and the placement of microdevices to optimize microdevice utilization during selective transfer processes. System substrates or acceptor substrates 390, 490, and 590 may be, but are not limited to, printed circuit boards (PCBs), thin-film transistor backplanes, integrated circuit substrates, or, in the case of optical microdevices such as LEDs, components of a display, such as a driver circuitry backplane. Patterned microdevice donor and acceptor substrates may be used in combination with different transfer techniques, including, but not limited to, pick and place using different mechanisms (e.g., electrostatic transfer heads, elastomeric transfer heads) or direct transfer mechanisms such as dual-function pads.

[0143] Figure 6A illustrates an alternative embodiment of the mesa structure of Figures 3A to 3F, wherein the mesa structure is initially etched through all layers without being etched. Here, a portion of the buffer layer 312 and / or contact layer 312 may be retained during the initial step. The mesa structure is formed on the donor substrate 310. The microdevice structure is formed by etching through different layers, such as the first bottom conductive layer 312, the functional layer 314, and the second top conductive layer 316. Top contacts 332 may be deposited before or after etching on top of the top conductive layer 316. The mesa structure may include other layers 372 that will be deposited and patterned before or after the formation of the mesa structure. These layers may be dielectrics, MIS, contacts, sacrificial layers, etc. After the mesa structure is formed, one or more filler layers 374, such as dielectric materials, are used between and around the microdevices to hold the microdevices together. The microdevices are bonded to a temporary substrate 376 by one or more substrate bonding layers 378. One or more bonding layers 378 can provide one or more different forces, such as electrostatic forces, chemical forces, physical forces, thermal forces, etc. After the device is removed from the donor substrate 310, as described above, additional portions of the bottom conductive layer 312 can be etched away or patterned to separate the device (FIG. 6C). Other layers, such as contact bonding layers 380, can be deposited and patterned. Here, the filler layer 374 can be etched to separate the microdevice, or the sacrificial layer can be removed to separate the device. In another embodiment, temperature can be applied to separate the device from the filler layer 374 and prepare it for transfer to the acceptor substrate 390. This separation can be performed selectively, as described above. In another embodiment, the filler layer 374 can be etched to form, for example, a truncated pyramid or frustoconical shape, at least partially surrounding each microdevice, a housing, base, or anchor 375, as shown in FIG. 6E. Another layer can be deposited over the base 375 and can be used to form anchors 598-2. After the additional layer 598-2 is formed, the filler base layer 375 can be left or removed from the anchoring device. Figure 6G shows a device with a sacrificial layer 372-2. The sacrificial layer 372-2 can be removed by etching or by thermal deformation or thermal removal.

[0144] In another embodiment, the anchor is the same as that of the housing 375 and is constructed of polymer layers, organic layers, or other layers after the microdevice is transferred to the cartridge 376. The housing 375 may have different shapes. In one case, the housing may be matched to the shape of the device. The housing sidewalls may be shorter than the height of the microdevice. The housing sidewalls may be attached to the microdevice before the transfer cycle to support the post-processing of different microdevices in the cartridge 376 and the packaging of the microdevice cartridge for transport and storage. The housing sidewalls may be separable, or the connection from the device to the microdevice may be weakened from the device by different methods such as heating, etching, or exposure before or during the transfer cycle.

[0145] The device on the donor substrate 310 may be configured to have two contacts 332 and 380 on the same side opposite to the donor substrate 310. In this case, the conductive layer on the cartridge 376 may be patterned to independently bias the two contacts 332 and 380 of the device. In one case, the device may be transferred directly from the cartridge substrate 376 to the recipient substrate 390. Here, the contacts 332 and 380 will not be directly bonded to the recipient substrate 390, i.e., the recipient substrate 390 does not need to have special pads. In this case, the conductive layer is deposited and patterned to connect the contacts 332 and 380 to appropriate connections in the recipient substrate 390. In another embodiment, the device may be transferred from the cartridge 376 to a temporary substrate before being transferred to the recipient substrate 390. Therefore, the contacts 332 and 380 may be directly bonded to the recipient substrate pads. The device may be tested in the cartridge 376 or in the temporary substrate.

[0146] Due to the mismatch between the substrate lattice and the microdevice layer, the layer growth contains several defects such as dislocations and voids. To reduce these defects, at least one first buffer layer 6114 and / or a second buffer layer 6118 having a separation layer 6116 between or near the donor substrate 6110 can first be deposited, and then an active layer 6112 can be deposited over the buffer layers 6114 and / or 6118. The thickness of the buffer layers 6114 and 6118 can be quite large, for example, the same as the thickness of the donor substrate 6110. The buffer layers 6114 / 6118 can also be separated during the separation (peeling) of the microdevice from the donor substrate 6110. Therefore, the buffer layer deposition should be repeated each time. Figure 6H shows the structure on the substrate 6110, wherein the separation layer 6116 is located between the first buffer layer 6114 and the actual device layer 6112. A second buffer layer 6118 may be present between the separation layer 6116 and the device layer 6112. The second buffer layer 6118 also prevents contaminants from the separation layer 6116 from penetrating into the device layer 6112. Both buffer layers 6114 and 6118 may comprise more than one layer. The separation layer 6116 may also comprise a stack of different materials. In one example, the separation layer 6116 responds to light wavelengths that other layers do not respond to. This light source can be used to separate the actual device 6112 from one or more buffer layers 6114 / 6118 and the donor substrate 6110. In another example, the separation layer 6116 responds to chemicals that do not affect other layers. This chemical can be used to remove the separation layer 6116 or alter its properties to separate the device from one or more buffer layers 6114 / 6118 and the substrate 6110. This method keeps the first buffer layer 6114 intact on the donor substrate 6110, and therefore, the first buffer layer can be reused for the next device deposition. Surface treatments such as cleaning or buffering may be performed before the next device deposition. In another instance, one or more buffer layers 6114 / 6118 may include zinc oxide.

[0147] Prior to the separation process (peeling), the microdevice can be separated by different etching processes, as shown in FIG6I. Etching may etch the second buffer layer 6118 (if present), and may etch part or all of the release layer 6116 and the device layer 6112. In another example, neither the second buffer layer 6118 nor the release layer 6116 is etched. After the etching step, the microdevice is temporarily (or permanently) bonded to another substrate 6150, and the release layer 6116 is removed or modified to separate the microdevice from the first buffer layer 6114 and the second buffer layer 6118. As shown in FIG6J, the first buffer layer 6114 may remain substantially intact on the donor substrate 6110.

[0148] In another embodiment shown in Figures 6K to 6M, layers such as a first bottom conductive layer 312, a functional layer 314, and a second top conductive layer 316 may be formed on the donor substrate 6210 in the form of islands 6212. Figure 6K shows a top view of islands 6212 formed in a microdevice array. The size of the islands 6212 may be the same as or a multiple of the box size. The islands 6212 may be formed starting from or after buffer layers 6114 / 6118. Here, surface treatment may be performed on the surface or gaps 6262, 6263 may be formed to initiate thin film growth into islands (Figure 6L). To process the microdevices, the gaps may be filled by a filler layer 6220, as shown in Figure 6M. The filler 6220 may be composed of a polymer layer, a metal layer, or a dielectric layer. After processing the microdevices, the filler layer 6220 may be removed.

[0149] Figure 7 emphasizes the process of generating a microdevice cassette. During the first step 702, a microdevice is fabricated on a donor substrate, such as 310 or 510. During this step, the device is formed and post-processing is performed on the device. During the second step 704, the device is prepared for separation from the donor substrate 310 or 510. This step may involve securing the microdevice using anchors, such as 375, 476-1, 592, 594, 598, or 598-2, and fillers, such as 374, 472, and 574. During the third step 706, a cassette or temporary substrate, such as 376 or 476, is formed from the pre-processed microdevice from the first step 702 and the second step 704. In one case, during this step, the microdevice is directly or indirectly bonded to the cassette substrate 376 or 476 by a bonding layer, such as 378 or 478. Next, the microdevice is separated from the microdevice cartridge substrate 376 or 476. In another embodiment, the cartridge is formed on a microdevice donor substrate, such as 510. After the device is attached to the cartridge substrate 376, 476, or 510, other processing steps may be performed, such as removing layers, such as 312, 374, 472, 574; or adding electrical layers (e.g., contacts 380 or 480) or optical layers (lenses, reflectors, etc.). During the fourth step 708, the cartridge 376 or 476 is moved to a recipient substrate, such as 390, 490, or 590, to transfer the device to the recipient substrate 390, 490, or 590. Some of these steps may be rearranged or combined. While the microdevice is still on the cartridge substrate, such as 376 or 476, or after the microdevice has been transferred to a recipient substrate, such as 390, 490, or 590, a test step 707A may be performed on the microdevice to determine if the microdevice is defective. In step 707B, defective microdevices can be removed or repaired in situ. For example, a predetermined number of microdevices can be tested, and if the number of defects exceeds a predetermined threshold, the entire group of microdevices can be removed, at least some of the defective microdevices can be removed, and / or at least some of the defective microdevices can be repaired.

[0150] Figure 8 illustrates the steps of transferring a device from cartridges 376, 476, or 510 to receiver substrates 390, 490, or 590. Here, during the first step 802, cartridges 376, 476, or 510 are loaded (or picked up), or in another embodiment, a spare device arm is pre-loaded with cartridges 376, 476, or 510. During the second step 804, cartridges 376, 476, or 510 are aligned with a portion (or all) of the receiver substrate. This alignment can be performed using dedicated alignment marks on cartridges 376, 476, or 510 and receiver substrates 390, 490, or 590, or using the microdevice and landing areas on receiver substrates 390, 490, or 590. During the third step, the microdevice is transferred to a selected landing area. During the fourth step 808, if the receptor substrate 390, 490, or 590 is fully filled, the cassette substrate 376, 476, or 510 is moved to the next step, such as another receptor substrate 390, 490, or 590, in step 810. If the current receptor substrate 390, 490, or 590 requires further filling, one or more additional cassettes 376, 476, or 510 are used for additional transfer steps. Before a new transfer cycle, if the cassettes 376, 476, or 510 do not have sufficient space, the cycle begins from the first step 802. If the cassettes 376, 476, or 510 have sufficient space in step 812, the cassettes 376, 476, or 510 are offset (or moved and aligned) to a new area of ​​the receptor substrate 390, 490, or 590 in step 814, and the new cycle continues to step 806. Some of these steps may be combined and / or rearranged.

[0151] Figure 9 illustrates the steps of transferring a device from a cassette, such as a temporary substrate 376, 476, or 510, to a recipient substrate, such as 390, 490, or 590. Here, during the first step 902, cassette 376 or 476 is loaded (or picked up), or in another embodiment, a spare device arm is pre-loaded with a cassette. During the second steps 902-2, a set of microdevices is selected from cassettes 376, 476, or 510 such that the number of defects therein is less than a threshold. During the third step 904, cassettes 376, 476, or 510 are aligned with a portion (or all) of the recipient substrate. This alignment can be performed using dedicated alignment marks on cassettes 376, 476, or 510 and / or recipient substrates 390, 490, or 590, or using landing areas on the microdevices and recipient substrates 390, 490, or 590. Then, during the third step 906, the microdevice can be transferred to the selected landing area. In step 906-1, if applicable, selected microdevices in the cassette can be connected to the receiver substrate. In step 906-2, if applicable, the connection between the microdevices and the receiver substrate can be tested, for example, by biasing the receiver substrates 390, 490, or 590. If individual microdevices are found to be defective or nonfunctional, an additional adjustment step 906-3 can be performed to correct or repair some or all of the nonfunctional microdevices.

[0152] If the receptor substrate is fully filled, the receptor substrate 390, 490, or 590 is moved to the next step. If the receptor substrate 390, 490, or 590 requires further filling, an additional transfer step is performed from one or more additional cartridges 376, 476, or 510. Before a new transfer cycle, if 376, 476, or 510 does not have sufficient space, the cycle begins from the first step 902. If cartridges 376, 476, or 510 have sufficient space, in step 902-2, cartridges 376, 476, or 510 are offset (or moved and aligned) to a new area of ​​the receptor substrate 390, 490, or 590.

[0153] Figure 10 illustrates exemplary processing steps for producing multiple types of microdevice cassettes 376, 476, 510, or 1108. During a first step 1002, at least two different microdevices are fabricated on different donor substrates, such as 310 or 510. During this step, the device is formed and post-processing is performed on it. During a second step 1004, the device is prepared for separation from the donor substrate, such as 310 or 510. This step may involve securing the microdevice using anchors, such as 375, 476-1, 592, 594, 598, and 598-2, and fillers, such as 374, 472, and 574. During a third step 1006, a first device is moved to cassette 376, 476, 510, or 1108. During a fourth step 1008, at least a second microdevice is moved to cassette 376, 476, 510, or 1108. In one scenario, during this step, the microdevice is directly or indirectly bonded to the cartridge substrate 376, 476, 510, or 1108 via a bonding layer, such as 378 or 478. The microdevice is then separated from the microdevice cartridge substrate 310 or 510. For direct transfer, different types of microdevices may have different heights. For example, a second type of microdevice transferred to cartridges 376, 476, 510, or 1108 may be slightly higher than a first type of microdevice (or, for the second type of microdevice, its position on cartridges 376, 476, 510, or 1108 may be slightly higher). Here, after cartridges 376, 476, 510, or 1108 are fully filled, the height of the microdevice can be adjusted to make the surface of cartridges 376, 476, 510, or 1108 flat. This can be done by adding material to shorter microdevices or removing material from taller devices. In another scenario, the landing area on the acceptor substrate 390, 490, or 590 may have a different height associated with the differences in cassettes 376, 476, 510, or 1108. Another method of filling cassettes 376, 476, 510, or 1108 is based on pick-and-place. The pick-and-place process can be used to move the microdevice to cassettes 376, 476, 510, or 1108. Here, for microdevices in a cluster of cassettes 376, 476, 510, or 1108, the force element on the pick-and-place head may be uniform, or a single force element may be used for each microdevice. Furthermore, microdevices may be moved to cassettes 376, 476, 510, or 1108 in other ways. In another embodiment, the additional device is moved away from the cassette substrate 376, 476, 510 or 1108 of the first or second (or third or other) microdevice, and other types of microdevices are transferred to an empty area on the cassette 376, 476, 510 or 1108.After the device is secured to the cartridge substrates 376, 476, 510, or 1108, further processing steps may be performed, such as adding filler layers 374, 474, or 574; removing some layers; or adding electrical layers (e.g., contacts 380, 480, or 580) or optical layers (lenses, reflectors). The device may be tested before or after it is used to fill the receiver substrates 390, 490, or 590. This testing may be electrical testing, optical testing, or a combination of both. This testing can identify defects and / or performance issues of the device on the cartridge. During the final step 1010, the cartridges 376, 476, 510, or 1108 are moved to the receiver substrates 390, 490, or 590 to transfer the device to the receiver substrates 390, 490, or 590. Some of these steps may be rearranged or combined.

[0154] The transfer process described herein (e.g., Figures 7, 8, 9, and 10) may include a stretching step for increasing the spacing of microdevices on cartridges 376, 476, 510, or 1108. This step may be performed prior to alignment or as part of an alignment step. This step may increase the number of microdevices aligned with landing areas (or pads) on recipient substrates 390, 490, or 590. Furthermore, this step may match the spacing between arrays of microdevices comprising at least two microdevices on cartridges 376, 476, 510, or 1108 to match the spacing of landing areas (or pads 382) on recipient substrates 390, 490, or 590.

[0155] Figure 11 shows an example of a multi-type microdevice cassette 1108 similar to temporary substrates 376, 476, or 510. The cassette 1108 contains three different types of microdevices, such as those of different colors (red, green, and blue), 1102, 1104, and 1106. However, more device types may exist. The distances x1, x2, and x3 between the microdevices are related to the spacing of the landing areas in the receiver substrates 390, 490, or 590. Different spacings x4 and x2 may exist after several devices that may be related to the pixel spacing in the receiver substrates 390, 490, or 590. This spacing compensates for the mismatch between the pixel spacing and the microdevice spacing (landing area spacing). In this case, if pick-and-place is used to generate the cassette 1108, the force elements may be in the form of columns corresponding to each microdevice type, or the force elements may be separate elements for each microdevice.

[0156] Figure 12 shows an example of a multi-type microdevice box 1208 similar to temporary substrates 376, 476, or 510. Box 1208 contains three different types of microdevices, such as those of different colors (red, green, and blue), 1202, 1204, and 1206. Other areas 1206-2 may be empty, filled with spare microdevices, or contain a fourth type of microdevice. The distances x1, x2, and x3 between the microdevices are related to the spacing of the landing areas in the receiver substrates 390, 490, or 590. Different spacings x4 and x2 may exist after several device arrays that may be related to the pixel spacing in the receiver substrates 390, 490, or 590. This spacing compensates for the mismatch between the pixel spacing and the microdevice spacing (landing area spacing).

[0157] Figure 13 shows an example of a microdevice 1302 fabricated on a donor substrate 1304, similar to donor substrate 310 or 510, before being transferred to multi-type microdevice cassettes 376, 476, 510, 1108, 1208. Here, support layers 1306 and 1308 can be used for a single device or a group of devices. Here, the spacing can match the spacing in cassettes 376, 476, 510, 1108, 1208, or the spacing can be a multiple of the cassette spacing.

[0158] In all the above structures, the microdevice can be moved from the first box to the second box before filling the substrate with the microdevice. Additional processing steps can be performed after the transfer, or some of the processing steps can be divided between the first box structure and the second box structure.

[0159] Figure 14A illustrates an embodiment of a microdevice in a donor substrate 1480 similar to donor substrate 310 or 510. Due to manufacturing and material defects, the output power of the microdevice on the donor substrate 1480 may gradually decrease or increase, i.e., there is non-uniformity, as shown by the coloring from dark to light. Since devices can be transferred together to a block, such as block 1482, or can be transferred sequentially one or more at a time to recipient substrates 390, 490, or 590, adjacent devices in recipient substrates 390, 490, or 590 gradually degrade. However, a worse problem may occur where one block, such as 1482, or a series of adjacent blocks ends and another block, such as 1483, or another series of blocks begins, such as along the intersection line 1484, which may cause a sudden change in output performance, as shown in Figure 14B. This sudden change may cause visual artifacts in optoelectronic devices such as displays.

[0160] To address the issue of non-uniformity, one embodiment shown in FIG14C includes using blocks above and below individual blocks 1482 and 1483 in the display to skew or intersect these individual blocks, such that the edges or intersections of the blocks are not sharp lines, thereby eliminating intersections 1484, and thereby forming a skewed pattern on the display. Therefore, the average effect of abrupt changes is significantly reduced. The skew can be random and can have different contours.

[0161] Figure 14D illustrates another embodiment in which microdevices in adjacent blocks are flipped so that devices with similar performance are adjacent to each other. For example, the performance in the first block 1482 decreases from the first outer side A to the first inner side B, while the performance of the second adjacent block 1483 increases from the second inner side B adjacent to the first inner side B to the second outer side A. This makes the changes and transitions between blocks very smooth and eliminates long, sharp intersections 1484.

[0162] Figure 14E illustrates an exemplary combination of flipping devices, such as alternating high-performance and low-performance devices on the inside and skewing the edges to further improve average uniformity. In the illustrated embodiment, the device performance alternates between high and low in two directions, i.e., in adjacent horizontal blocks and adjacent vertical blocks.

[0163] In one case, the performance of the microdevices at the edge of the adjacent transferred blocks (arrays) is matched before being transferred to the recipient substrate 390, 490 or 590.

[0164] Figure 15A illustrates the use of two or more blocks 1580, 1582 to fill blocks in the receptor substrate 1590. In the illustrated embodiment, skew or flipping methods can be used to further improve average uniformity, as shown in Figure 15B. The higher (or lower) output power sides B and C from blocks 1580 and 1582, respectively, can be positioned adjacent to each other. In addition, the connections between blocks are skewed or staggered using the connections above and below the blocks. Moreover, random or defined patterns can be used to fill a cell or receptor substrate 1590 having more than one block.

[0165] Figure 16A shows a sample having more than one block 1680, 1682, and 1684. Blocks 1680, 1682, and 1684 may come from the same donor substrate 310 or 510 or from different donor substrates 310 or 510. Figure 16B shows an example of filling box 1690 with different blocks 1680, 1682, and 1684 to eliminate non-uniformity found in any block.

[0166] Figures 17A and 17B illustrate a structure with multiple cassettes 1790. As described above, the positions of the cassettes 1790 are selected in such a way that overlap between the same area of ​​the receptor substrates 390, 490, 590, or 1590 and the cassettes 1790 having the same microdevices is eliminated during different transfer cycles. In one instance, the cassettes 1790 may be independent, meaning that a separate arm or controller handles each cassette independently. In another embodiment, the alignment may be performed independently, but other operations may be performed simultaneously. In this embodiment, the receptor substrates 390, 490, 590, or 1590 may be movable for easy transfer after alignment. In another instance, the cassettes 1790 move together for easy transfer after alignment. In yet another instance, the cassettes 1790 and the receptor substrates 390, 490, 590, or 1590 may all be movable for easy transfer. In yet another case, the cassettes 1790 may be assembled in advance. In this case, a frame or substrate may hold the assembled cassettes 1790.

[0167] The distances X3 and Y3 between the boxes 1790 can be multiples of the widths X1 and X2 or the lengths Y1 and Y2 of the boxes 1790. This distance can be a function of the movement step size in different directions. For example, X3 = KX1 + HX2, where K is the leftward (direct or indirect) movement step size for filling the receptor substrates 390, 490, 590, or 1590, and H is the rightward (direct or indirect) movement step size for filling the receptor substrate. The same logic applies to the distance Y3 between the boxes 1790 and the lengths Y1 and Y2. As shown in Figure 17A, the boxes 1790 can be aligned in one or both directions. As shown in Figure 17B, in another example, the boxes 1790 are not aligned in at least one direction. Each box 1790 can have independent controls for applying pressure and temperature to the receptor substrates 390, 490, 590, or 1590. Other arrangements are also possible depending on the direction of movement between the receptor substrate 390, 490, 590 or 1590 and the cartridge 1790.

[0168] In another example, the cartridge 1790 may have different devices and thus fill different regions of the receptor substrates 390, 490, 590, or 1590 with different devices. In this case, the relative positions of the cartridge 1790 and the receptor substrates 390, 490, 590, or 1590 change after each transfer cycle to fill different regions with all the desired microdevices from the different cartridges 1790.

[0169] In another embodiment, a plurality of box arrays 1790 are prepared. Here, after a device is transferred from a first box array to a receptor substrate 390, 490, 590 or 1590, the receptor substrate 390, 490, 590 or 1590 moves to the next microdevice array to fill the remaining area in the receptor substrate 390, 490, 590 or 1590 or to receive different devices.

[0170] In another example, the box 1790 may be on a curved surface, and thus circumferential movement will provide contact points to transfer the microdevice into the recipient substrate 390, 490, 590 or 1590.

[0171] The vertical optoelectronic stack layer includes a substrate, an active layer, at least one buffer layer between the active layer and the substrate, and at least one separator layer between the buffer layer and the active layer, wherein the active layer can be physically removed from the substrate by changing the properties of the separator layer while the buffer layer remains on the substrate.

[0172] In one embodiment, the process of changing the properties of the one or more separation layers includes chemical etching or deforming the separation layers.

[0173] In another embodiment, the process of changing the properties of the one or more separation layers includes exposure to photoelectron waves, thereby deforming the separation layers.

[0174] In another embodiment, the process of changing the properties of the one or more separation layers includes changing the temperature, thereby deforming the separation layers.

[0175] In one embodiment, reusing the buffer layer to create a new photoelectron stack layer includes a surface treatment.

[0176] In one embodiment, the surface treatment uses chemical or physical etching or polishing.

[0177] In another embodiment, the surface treatment uses the deposition of an additional thin layer or buffer layer to reform the surface.

[0178] In one embodiment, the optoelectronic device is an LED.

[0179] In one embodiment, the separation layer is zinc oxide.

[0180] Embodiments of the present invention include a continuous pixelated structure, the pixelated structure comprising a fully or partially continuous active layer, a pixelated contact layer and / or a current dispersing layer.

[0181] In this embodiment, a pad layer and / or bonding layer may be present on top of the pixelated contact layer and / or current distribution layer.

[0182] In the above embodiments, a dielectric opening may be present on the top of each pixelated contact layer and / or current distribution layer.

[0183] Another embodiment includes a donor substrate comprising a microdevice having bonding pads and a filler layer filling the space between the microdevices.

[0184] Another embodiment includes a temporary substrate comprising a bonding layer to which a microdevice from a donor substrate is bonded.

[0185] Another embodiment includes a heat transfer technology comprising the following steps:

[0186] 1) Align the microdevices on the temporary substrate with the bonding pads on the system substrate;

[0187] 2) Verify that the melting point of the bonding pads on the system substrate is higher than the melting point of the bonding layer in the temporary substrate;

[0188] 3) Generate a thermal profile that melts both the bonding pad and the bonding layer, and subsequently keeps the bonding layer molten and the bonding pad solidified; and

[0189] 4) Separate the temporary substrate from the system substrate.

[0190] In another embodiment of the transfer technique, the thermal profile is generated by a local or global heat source or both.

[0191] Another embodiment includes a microdevice structure in which, after the microdevice is released from the donor substrate by means of a peeling process, at least one anchor holds the device to the donor substrate.

[0192] Another embodiment includes a transfer technique for a microdevice structure, wherein the anchor releases the microdevice after or during bonding the microdevice to a pad in a recipient substrate by means of a push or pull force.

[0193] In another embodiment, the anchor according to the microdevice structure is composed of at least one layer extending from the side of the microdevice to the substrate.

[0194] In another embodiment, the anchor according to the microdevice structure is composed of at least one layer of the void or the top of the void.

[0195] In another embodiment, the anchors according to the microdevice structure are composed of a filling layer surrounding the device.

[0196] Another embodiment includes a structure based on a microdevice structure, wherein the viscosity of the layer between the peeled microdevice and the donor substrate is increased by controlling the temperature to act as an anchor.

[0197] Another embodiment includes a release process for anchors in a microdevice structure, wherein temperature adjustment is used to reduce the force between the anchors and the microdevice.

[0198] Another embodiment includes a process of transferring a microdevice to a receptor substrate, wherein the microdevice is formed in a cassette; aligning the cassette with a selected landing area in the receptor substrate; and transferring the microdevice in the cassette associated with the selected landing area to the receptor substrate.

[0199] Another embodiment includes a process of transferring a microdevice to a receptor substrate, wherein the microdevice is formed in a cassette; selecting a group of microdevices with defective microdevices less than a threshold; aligning the selected group of microdevices in the cassette with a selected landing area in the receptor substrate; and transferring the microdevice in the cassette associated with the selected landing area to the receptor substrate.

[0200] The embodiments include a cartridge having various types of microdevices transferred therein.

[0201] An embodiment includes a microdevice housing, wherein a sacrificial layer separates at least one side of the microdevice from a filler layer or a bonding layer.

[0202] In this embodiment, the sacrificial layer is removed to release the microdevice self-filling layer or bonding layer.

[0203] In the embodiment, the sacrificial layer releases the microdevice self-filling material under certain conditions such as high temperature.

[0204] Microdevices can be tested to extract information related to the microdevices, including but not limited to defects, uniformity, operational status, etc. In one embodiment, one or more microdevices are temporarily bonded to a cassette having one or more electrodes for testing the microdevices. In one embodiment, another electrode is deposited after the microdevices are positioned in the cassette. This electrode can be used to test the microdevices before or after patterning. In one embodiment, the cassette is placed in a predetermined location (which may be a holder). The cassette and / or acceptor substrate is moved for alignment. At least one selected device is transferred to the acceptor substrate. If more microdevices become available on / in the cassette, the cassette or acceptor substrate is moved to align with a new region or a new acceptor substrate in the same acceptor substrate, and at least another selected device is transferred to the new location. This process can continue until the cassette no longer has enough microdevices, at which point a new cassette can be placed in the predetermined location. In one example, the transfer of the selected devices is controlled based on information extracted from the cassette. In one example, defect information extracted from the cell can be used to limit the number of defective devices transferred to the acceptor substrate to below a threshold number by eliminating the transfer of a group of devices with a defect number exceeding a threshold, or by preventing the cumulative number of transferred defects from exceeding a threshold. In another example, the cells will be binned based on one or more extracted parameters, with each bin used for a different application. In yet another case, cells with similar performance based on one or more parameters will be used in a single acceptor substrate. The examples presented here can be combined to improve cell transfer performance.

[0205] In an embodiment, physical contact and pressure and / or temperature can be used to transfer the device from the cartridge to the recipient substrate. Here, pressure and / or temperature can generate bonding forces (clamping forces) to hold the microdevice to the recipient substrate, and / or temperature can reduce the contact forces between the microdevice and the cartridge. Thus, the transfer of the microdevice to the recipient substrate is achieved. In this case, the location of the microdevice assigned to the recipient substrate can have a higher profile compared to the rest of the recipient to enhance the transfer process. In an embodiment, the cartridge does not have the microdevice in areas that may come into contact with unused areas of the recipient substrate, such as locations assigned to other types of microdevices during the transfer process. These two examples can be combined. In an embodiment, the assigned location of the microdevice on the substrate may have been wetted with an adhesive or covered with a bonding alloy, or additional structures may have been placed at the assigned location. During stamping, separate cartridges, printing, or other processes can be used. In an embodiment, selected microdevices on the cartridge can be moved closer to the recipient substrate to enhance selective transfer. In another case, the recipient substrate applies a pull force to assist or initiate the transfer of the microdevice from the cartridge. Tension can be combined with other forces.

[0206] In one embodiment, the housing may support a microdevice within a cartridge. The housing may be fabricated around or separately from the microdevice on a donor substrate or cartridge substrate, and then the microdevice is moved inward and bonded to the cartridge. In one embodiment, at least one polymer (or another type of material) may be deposited on top of the cartridge substrate. The microdevice from the donor substrate is pushed into the polymer layer. The microdevice is selectively or generally separated from the donor substrate. The layer may be cured before or after the device is separated from the donor substrate. This layer may be patterned, especially when multiple different devices are integrated into the cartridge. In this case, the layer may be created for one type, with the microdevice embedded in the layer and separated from its donor. Then, another layer is deposited and patterned for the next type of microdevice. Then, the second microdevice is embedded in the associated layer. In all cases, this layer may cover part or all of the device in the microdevice. In another case, the housing is constructed of a polymer layer, an organic layer, or other layers after the microdevice is transferred to the cartridge. The housing may have different shapes. In one case, the housing may be matched to the shape of the device. The housing sidewalls can be shorter than the height of the microdevice. The housing sidewalls can be attached to the microdevice before the transfer cycle to support post-processing of different microdevices within the cartridge and for packaging the microdevices for transport and storage. The housing sidewalls can be detached, or the connection to the microdevice can be weakened from the device by various methods such as heating, etching, or exposure before or during the transfer cycle. Contact points can be present to hold the microdevice to the cartridge substrate. The contact points to the cartridge can be on the bottom or top side of the device. The contact points can be weakened or eliminated by various methods such as heating, chemical processes, or exposure before or during the transfer. This process can be performed on selected devices or globally on all microdevices on the cartridge. The contacts can also be conductive to enable testing of the microdevice by biasing the device at the contact and other electrodes connected to the microdevice. During the transfer cycle, the cartridge can be positioned below the recipient substrate to prevent the microdevice from falling off the housing if the contacts are globally removed or weakened.

[0207] In one embodiment, the microdevice cassette may include at least one anchor for holding the microdevice to the surface of the cassette. The cassette and / or the receiver substrate are moved such that some of the microdevices in the cassette are aligned with some of the positions on the receiver substrate. The anchor may break under pressure during the pushing of the cassette and the receiver substrate towards each other or during the pulling of the device by the receiver substrate. The microdevice may remain permanently on the receiver substrate. The anchor may be located on the side of the microdevice or on the top (or bottom) of the microdevice.

[0208] The top side is the side of the device facing the box, and the bottom side is the opposite side of the microdevice. The other sides are called sidewalls or side walls.

[0209] In one embodiment, the microdevice can be tested to extract information related to the microdevice, including but not limited to defects, uniformity, operational status, etc. A cassette can be placed in a predetermined location (which may be a holder). The cassette and / or receiver substrate can be moved for alignment. At least one selected microdevice can be transferred to the receiver substrate. If more microdevices are available on / in the cassette, the cassette or receiver substrate can be moved to align with a new region or a new receiver substrate within the same receiver substrate, and at least another selected device can be transferred to the new location. This process can continue until the cassette does not have enough microdevices, at which point a new cassette will be placed in a predetermined location. In one case, the transfer of selected devices can be controlled based on information extracted from the cassette. In one case, defect information extracted from the cassette can be used to limit the number of defective devices transferred to the receiver substrate to below a threshold number by eliminating the transfer of a group of microdevices whose number of defects exceeds a threshold or whose cumulative number of transferred defects exceeds a threshold. In another case, the cassette is compartmentalized based on one or more extracted parameters, and each compartment can be used for different applications. In another scenario, cells with similar performance based on one or more parameters can be used in a single acceptor substrate. The examples presented here can be combined to improve cell transfer performance.

[0210] One embodiment includes a method of transferring a device to a recipient substrate. The method includes:

[0211] a) A preparation box having a substrate, wherein microdevices are positioned on at least one surface of the box substrate, and the substrate has more microdevices in a region outside the location of microdevices of the same size corresponding to a region in the receptor substrate.

[0212] b) By means of extracting at least one parameter from the device on the test box.

[0213] c) Pick up the cassette or transfer the cassette to a location with a microdevice facing the recipient substrate.

[0214] d) Use test data to select a set of microdevices on the box.

[0215] e) Align the selected set of microdevices on the cassette with the selected position on the receptor substrate. Transfer the set of microdevices from the cassette to the receptor substrate.

[0216] f) Processes d and e may continue until the box has no useful devices or the receptor substrate is completely filled.

[0217] One embodiment includes a cartridge having more than one type of microdevice positioned within the cartridge at the same spacing as in the receptor substrate.

[0218] One embodiment includes a box having a substrate on which microdevices are positioned (directly or indirectly) on the surface, and the microdevices are skewed in any column or row such that the edge of at least one column or row is not aligned with the edge of at least another column or row.

[0219] One embodiment is a method of transferring a device to a recipient substrate. The method includes transferring an array of microdevices into the substrate, wherein the edges of at least one column or row of transferred microdevices are not aligned with the edges of at least another column or row of transferred devices.

[0220] One embodiment includes a method of transferring a device to a recipient substrate. The method includes transferring an array of devices from a donor substrate to a recipient substrate, wherein in any region on the recipient substrate similar in size to the transferred array, there exists at least one column or row of microdevices having two different regions from the donor substrate corresponding to the transferred array.

[0221] One embodiment includes a process of transferring an array of microdevices into a receptor substrate, wherein the microdevices are skewed at the edges of the array to eliminate abrupt changes.

[0222] Another embodiment includes a process of transferring an array of microdevices into a receptor substrate, wherein the performance of the microdevices at adjacent edges of the two microdevice arrays is matched prior to the transfer.

[0223] Another embodiment includes a process of transferring a microdevice array into a recipient substrate, wherein the microdevice array is filled from at least two different regions of the microdevice donor substrate.

[0224] Another embodiment includes a process of transferring a microdevice array from a cassette to a recipient substrate, wherein a plurality of microdevice cassettes are placed in different positions corresponding to different regions of the recipient substrate, the cassettes are then aligned with the recipient substrate, and the microdevices are transferred from the cassettes to the recipient substrate. Different anchoring schemes for securing microdevices to a donor substrate are also provided.

[0225] The process of integrating microdevices into a system substrate involves creating and fabricating a donor substrate, transferring a pre-selected array of microdevices to a recipient substrate, and subsequently (or simultaneously) electrically or mechanically bonding the microdevices to the system substrate. During bonding between the two substrates, a curing agent is applied before or after alignment of the microdevices and the system substrate to assist in forming a strong bond. The curing agent includes one of the following: polyamide, SU8, PMMA, BCB film layers, epoxy resins, and UV-curable adhesives, and curing is performed by one of the following: electric current, light, heat, mechanical force, or chemical reaction. However, the current / voltage requirements for curing may be higher than the current / voltage requirements that the microdevices can withstand.

[0226] To avoid damaging the microdevice, there is a need for structures and methods to integrate the microdevice into a system substrate with enhanced bonding and conductivity. Furthermore, an alternative current / voltage path can be formed to avoid damaging the microdevice.

[0227] According to one embodiment, a bonding structure may be provided. The bonding structure may include a plurality of microdevices on a donor substrate, each microdevice including one or more conductive pads formed on the surface of the microdevice; and a temporary material covering at least a portion of each microdevice or the one or more conductive pads.

[0228] In one case, temporary material acts as an anchor, which holds the multiple microdevices inside the housing structure in the donor substrate.

[0229] In another case, all or part of the microdevice may be covered by a temporary conductive material, which can redirect current through the temporary conductive material rather than the microdevice, and thus avoid damage to the microdevice.

[0230] In one case, the microdevice may have a conductive pad on each side of the microdevice. In another case, the microdevice may have more than one conductive pad on one side.

[0231] Figure 18 illustrates a donor substrate 1802 holding a plurality of microdevices via donor force elements according to an embodiment of the present invention. The donor substrate 1802 may be a growth substrate (on which microdevices are fabricated or grown) to which it has been transferred or another temporary substrate. Reference is made to gallium nitride (GaN) based LEDs below; however, the structure described herein can be used for any type of LED with different material systems.

[0232] In general, GaN-based microLEDs are fabricated by stacking materials deposited on a sapphire substrate. Conventional GaN LED devices include a substrate such as sapphire, an n-type GaN layer formed on the substrate, or a buffer layer (e.g., GaN), an active layer / semiconductor layer, such as a multiple quantum well (MQW) layer and a p-type GaN layer.

[0233] As shown in FIG. 18, the plurality of microdevices on the donor substrate 1802 may have conductive pads 1814, 1816 on both the top and bottom of a stack of semiconductor layers 1806. The acceptor substrate 1808 has at least one acceptor force element 1818 for each selected microdevice selected for transfer to the acceptor substrate 1808. In one case, the acceptor force element is a current / voltage curable component. Here, a current / voltage 1810 is applied to the selected acceptor force element (e.g., 1818), thereby causing it to harden and hold the microdevice in place. In one example, the acceptor force element may comprise a monomer that forms a polymer under an applicable charge. In another example, the acceptor force element is a medium having a high-resistivity trace that generates heat under an applicable current / voltage, and the generated heat causes the medium to locally cure.

[0234] The donor substrate 1802 has at least one donor force element 1804. The donor force element 1804 is an element that loses its adhesive properties under current or voltage. Here, voltage / current 1812 is applied to the donor force element 1804, which is held in place for transfer. In one example, the donor force element is a polymer that decomposes (oxidizes) under charge application. In another example, the donor force element is a high-resistivity trace that burns under applicable current / voltage.

[0235] FIG19 illustrates a microdevice having one or more conductive pads on one side according to an embodiment of the present invention. Here, in one example, the microdevice may have two conductive / contact pads 1904, 1906 at the bottom of the semiconductor layer stack on the donor substrate 1902. The acceptor substrate 1908 has an acceptor force element 1918 corresponding to the contact pads for each microdevice selected for transfer to the acceptor substrate 1908. The acceptor force element is a current / voltage curable component. Here, a current / voltage 1910 is applied to the selected acceptor force element (e.g., 1918), thereby causing it to harden and hold the microdevice in place.

[0236] Voltage / current 1910, 1912 may be applied to a selected receiving force element (e.g., 1918) to cure it, thereby hardening it and holding the microdevice in place.

[0237] In one case, the microdevice may be used as part of a bias circuit. Here, a voltage / current 1914 may be applied via the donor substrate 1902, or a voltage / current 1910, 1912 may be applied to the acceptor substrate 1908, which passes through the microdevice and through either the donor substrate 1902 or the acceptor substrate 1908.

[0238] However, the current / voltage requirements of the solidified force-bearing element may be higher than the current / voltage requirements that the microdevice can withstand. To avoid damage to the microdevice, an alternative current / voltage path may be formed. In another case, part or all of the microdevice may be covered with a temporary conductive material, which can redirect current through the temporary conductive material rather than the microdevice and avoid damage to the microdevice.

[0239] Figures 20A-20I illustrate examples of microdevices partially / completely covered by temporary conductive material according to some embodiments of the present invention.

[0240] Part or all of the microdevice may be covered by a temporary conductive material, which redirects current through the temporary conductive material rather than the microdevice, thus preventing damage to the microdevice. In one case, the temporary material may be a temporary conductive material. This conductive material may be connected as a sheet or trace to the same or different conductive material on the donor substrate.

[0241] In one embodiment, the microdevice may be located inside the housing structure. A sacrificial layer may be present between the housing wall and the microdevice. In another embodiment, a bonding material may also be present between the donor substrate and the microdevice and conductive pads (a material similar to the housing wall) or a combination thereof.

[0242] In one embodiment, the temporary layer may also act as an anchor to hold the device in place. In another embodiment, anchors may be present to hold the microdevice to the donor substrate. The anchors may be made of the same or different material as the housing. In one case, the housing may extend almost to the edge of the microdevice. In another case, the housing wall is shorter than the microdevice. The housing may also be taller than the microdevice.

[0243] In another case, the temporary conductive material may be replaced by a non-conductive material.

[0244] In cases where both conductive and non-conductive temporary materials are used, the temporary material can hold the microdevice in place after the sacrificial layer is removed or released. The microdevice can then be transferred to another substrate. During the transfer process, the temporary material is removed or separated from the housing structure. The separation process can be mechanical (e.g., push or pull), optical, thermal, or chemical.

[0245] The microdevice may be covered with a temporary material / layer before transfer to the recipient substrate, or it may be covered after transfer to the recipient substrate. In one case, a shell material is coated on the substrate between the microdevices. It may be bonded to the donor substrate, and then the shell material may be cured. In another case, different materials may be present on the surface of the donor substrate that can be electrically coupled to the microdevice or the temporary layer. In yet another case, the shell material is coated on top of the donor substrate. The microdevice is then bonded and pushed into the material, and then the material is cured. The shell material may be epoxy, polymer, or other types of materials. In one case, BCB or polyamide may be used as the shell material.

[0246] The temporary material can be patterned to form an opening on the top of the donor substrate. This opening can facilitate a process such as removing the sacrificial layer to separate the microdevice from the housing sidewall.

[0247] Figures 20A1-20A2 show examples of a temporary conductive material covering the surface of a microdevice according to some embodiments of the present invention.

[0248] Referring to Figure 20A1, the microdevice is located inside the housing structure 2006a. A sacrificial layer may be present between the housing structure / wall 2006a and the microdevice 2016. In one case, the sacrificial layer 2008a may be a patterned sacrificial layer covering the length of the housing. In another case, the sacrificial layer 2008b may be provided to the length of the microdevice. The material between the donor substrate and the microdevice may be a bonding material 2010a, conductive pads 2004a, or a material similar to the housing wall, or a combination thereof. Anchors 2014a hold the microdevice in the donor substrate. The anchors may be made of the same or different material as the housing. A temporary conductive material 2002a may cover the surface of the microdevice 2016, which includes the conductive pads 2004a and the housing 2006a. This structure facilitates the transfer of the microdevice, thereby allowing inspection of defective microdevices on the system substrate.

[0249] In another embodiment, the housing wall may extend almost to the edge of the microdevice.

[0250] FIG20A2 shows a cross-sectional view of a microdevice on a device (donor) substrate according to an embodiment of the present invention, wherein the temporary conductive material does not cover the entire surface of the microdevice. Here, the housing 200b and the sacrificial layer 2008b may extend almost to the edge of the microdevice 2016. The temporary conductive material 2002a may include conductive pads 2004a. Traces on the conductive layer of the donor substrate or between donor substrates may couple the conductive material to a current / voltage source.

[0251] FIG20B1 shows a cross-sectional view of a microdevice on a device (donor) substrate according to an embodiment of the present invention, wherein a temporary conductive material covers a portion of the conductive pads of the microdevice. Here, conductive pads such as 2004c are patterned conductive pads, and the sacrificial layer 2008c is also a patterned sacrificial layer deposited around the microdevice and the conductive pads. Temporary conductive material 2002a may cover the surface of the microdevice 2016, which includes a portion of the conductive pads 2004a and the housing 2006a. In another case, the sacrificial layer may extend only to a portion of the microdevice. Temporary conductive material 2002a may be coupled to a current source / voltage to facilitate curing or debonding. Traces on the conductive layer between the donor substrates or donor substrates may couple the conductive material to the current / voltage source.

[0252] FIG2 shows a cross-sectional view of a microdevice on a device (donor) substrate according to an embodiment of the present invention, wherein the temporary conductive material does not cover the entire surface of the microdevice. Here, the housing 2006b may extend almost at the edge of the microdevice. The temporary conductive material 2002a may include a portion of the conductive pad 2004b.

[0253] Figure 20C1 illustrates an example of temporary conductive material forming a current / voltage path between conductive pads 2004c and 2006c, wherein the conductive pads may be on the top and bottom or the same side of the microdevice. Here, temporary conductive material 2002c also covers the microdevice, which facilitates the selective transfer of the microdevice to the system substrate. This structure helps redirect current through the temporary conductive material, rather than the microdevice, and thus avoids damage to the microdevice.

[0254] Figure 20C2 illustrates an example in which no bonding material exists between the donor substrate and the microdevice. A temporary conductive material forms a current / voltage path between conductive pads 2004c and 2006c, wherein the conductive pads may be on the top and bottom or the same side of the microdevice. Temporary conductive material 2002c also covers one of the surfaces of the microdevice. Here, the temporary conductive material acts as the bonding material to the microdevice.

[0255] Figure 20D shows another example of temporary conductive material 2002d forming a current / voltage path between conductive pads 2004d and 2006d of the microdevice when the temporary conductive material 2002d and the conductive pads do not cover the entire surface of the microdevice. Here, conductive pads such as 2004d are patterned conductive pads, and temporary material is deposited on the patterned conductive pads.

[0256] Figure 20E illustrates another example, in which temporary conductive material 2002e forms current / voltage paths for more than one pad on the surface of the microdevice. Here, the conductive material shorts the conductive pads to the surface of the microdevice. The conductive material covers or connects to pads 2004e, 2006e, or to pads 2008e, 2010e. Traces on the donor substrate (directly or indirectly) can connect some of the conductive material together. Here, the conductive material may partially or completely cover the conductive pads depending on voltage and current requirements.

[0257] Figure 20F shows an example of conductive pads 2008f and 2010f on surfaces not shorted together by conductive layer 2002f. Here, the pads may be completely or partially covered by conductive layer 2002f, as shown. There is no bonding material between the donor substrate and the microdevice. Temporary conductive material acts as the bonding material for the microdevice.

[0258] Figure 20G illustrates another example, wherein a temporary conductive material 2002g forms a current / voltage path for more than one pad on the surface of the microdevice. Here, the conductive material forms a path between the surface facing the donor substrate and the surface away from the donor substrate. And in one case, it shorts the pads on the surface. Here, the conductive material covers or connects to conductive pads 2012g, 2014g.

[0259] Figure 20H shows an example of conductive pads 2008h and 2010h on surfaces not shorted together by conductive layer 2002h. Here, conductive pads 2012h and 2014h may be completely covered, or conductive pads 2008h and 2010h may be partially covered, as shown. In all cases, conductive material 2004h can directly couple a surface away from the donor substrate to the conductive layer at the donor substrate. In another case, it indirectly couples a surface away from the donor substrate to the conductive layer 2006h at the donor substrate.

[0260] Figures 20I1 and 20I2 show an example in which there are no conductive pads on the surface away from the donor substrate. Here, there are no conductive pads on the surface of the microdevice away from the donor substrate. In this case, the temporary material 2002h holds the device in place after the sacrificial layers 2006a and 2008a are removed. After the microdevice is transferred to another substrate, the temporary material is removed or separated from the housing, thereby releasing the microdevice from the donor substrate.

[0261] Figures 21A-21D show top views of various microdevices constructed with temporary materials (conductive or non-conductive) according to embodiments of the present invention. The temporary material may be patterned to form an opening on the top of the donor substrate. This opening may facilitate a process, such as removing the sacrificial layer, to separate the microdevice from the housing sidewalls. This process may be performed before or after the microdevice is transferred to the recipient substrate. In one case, chemical etching may be used to remove (or modify) the sacrificial layer. In another case, an electromagnetic signal (e.g., microwaves or light) may be used to release the device by removing / modifying the sacrificial layer. Here, the temporary layer may also act as an anchor to hold the device in place. If the temporary layer does not assist in the bonding process, it does not need to connect (or cover) the pads on the microdevice.

[0262] FIG21A shows an exemplary top view representation of FIG20A according to an embodiment of the present invention. Here, the microdevice 2102 on the donor substrate 2104 has conductive pads 2106 surrounded by a temporary conductive material 2108 and a sacrificial layer 2110. Here, traces of conductive material on the top of the donor substrate may be connected as a mesh, column, or row. Access points may be present on the top of the donor substrate to bias the temporary layer via the traces.

[0263] FIG21B1 shows an exemplary top view representation of FIG20B. Here, traces on the top of the donor substrate may be connected as meshes, columns, or rows. Access points may be present on the top of the donor substrate to bias a temporary layer via traces. The microdevice 2102 on the donor substrate 2104 has patterned conductive pads 2106-1 surrounded by a sacrificial layer 2110. Traces of temporary conductive material on the top of the donor substrate may be connected as meshes, columns, or rows. Access points may be present on the top of the donor substrate to bias a temporary layer via traces.

[0264] Figure 21B2 shows an example in which the temporary material is not connected to the pads. The microdevice 2102 on the donor substrate 2104 has conductive pads 2106-2 surrounded by a sacrificial layer 2110, and the traces of the temporary conductive material on the top of the donor substrate can be connected as a mesh, column, or row. This can be used in other embodiments or related structures of the present invention.

[0265] FIG21C shows an exemplary top view representation of FIG20E, wherein the microdevice 2102 has one or more pads (2106-3, 2106-4) on a donor substrate 2104 surrounded by a temporary conductive material 2108 and a sacrificial layer 2110. Here, traces on the top of the donor substrate 2104 may be connected as a mesh, column, or row. And the traces of each pad may be processed in a separate connection group. Access points may be present on the top of the donor substrate to bias the temporary layer via the traces.

[0266] FIG21D shows an exemplary top view representation of FIG20F, wherein the microdevice 2102 has one or more patterned conductive pads (2106-3, 2106-4) on a donor substrate 2104 surrounded by a temporary conductive material 2108 and a sacrificial layer 2110. Here, traces on the top of the donor substrate 2104 can be connected as a mesh, column, or row. And the traces of each pad can be processed in a separate connection group. Access points may be present on the top of the donor substrate to bias the temporary layer via the traces. The microdevice is released from the donor substrate via a breakable anchor.

[0267] Some embodiments of the present invention show that the microdevice may have different temporary anchors, whereby, after the device is peeled off, the temporary anchors hold the device to the donor substrate and can selectively move toward or away from the surface of the donor substrate. Thus, as the donor substrate becomes closer to the recipient substrate, some selected devices approach or connect to the recipient substrate, while other microdevices remain significantly away from the recipient substrate. The temporary anchors release the microdevice after or during bonding to pads in the recipient substrate by either push or pull. The anchors may break under pressure during pushing the donor and recipient substrates toward each other or by pulling the microdevice by the recipient substrate. The microdevice may be permanently retained on the recipient substrate. The anchors may be on one side of the microdevice or at the top (or bottom) of the microdevice.

[0268] Figures 22A-22C illustrate microdevices on a donor substrate according to an embodiment of the present invention, wherein the microdevices are selectively movable toward or away from the surface of the donor substrate.

[0269] Referring to FIG22A, according to one embodiment, the stack includes electrodes 2204, 2206 and an electroactive polymer (EPE) layer 2208 formed beneath microdevices (e.g., 2210, 2212 on top of donor substrate 2214). Movement of the donor substrate and / or acceptor substrate causes some microdevices in the donor substrate to align with some locations in the acceptor substrate. In one case, a voltage is applied to the stack, causing the stack to thin and thus bringing the devices closer to the surface of the acceptor substrate.

[0270] Referring to FIG22B, according to another embodiment, the stack includes electrodes 2208, 2206 and an electroactive polymer (EPE) layer 2222 formed beneath the microdevices (e.g., 2210, 2212 on top of the donor substrate 2214). In one case, the electrodes may be disposed around the EPE layer. The EPE layer may be thin or thick as required. The stack thickens when a voltage is applied to the stack including the electrodes and the EPE layer. In one case, a housing and anchors may also hold the microdevices 2210, 2212 in place.

[0271] Figure 22C illustrates another example in which the stacked electrodes and microdevices 2210, 2212 on top of EPEs 2222, 2220 are surrounded by a housing structure 2226. Furthermore, anchors 2234 secure the microdevices 2210, 2212 within the housing structure 2226. In another case, a bonding layer may hold the microdevices on top of the stacked EPEs. The housing may have different shapes. In one case, the housing may match the shape of the device. The housing sidewalls may be shorter than the height of the microdevice. The housing sidewalls may be connected to the microdevice prior to transfer cycles to support different post-processing of the microdevice.

[0272] During the transfer of microdevices 2210 and 2212 from the donor substrate 2214 to the recipient substrate, the EPE stack 2222 pushes the microdevice 2210 forward. This thrust releases the anchor 2234, and the microdevice can be placed on the surface of the recipient substrate.

[0273] Figures 23A-23B show another embodiment of a microdevice on a donor substrate, wherein the microdevice can be selectively moved toward or away from the surface of the donor substrate.

[0274] In FIG. 23A, according to another embodiment, stacks of different materials 2304, 2308, and 2310 with different coefficients of thermal expansion are formed on the top of the donor substrate 2320, below the microdevices 2312, 2314, and 2318, respectively. When the temperature of the stack 2308 changes, the stack 2308 becomes distorted and pushes the device 2314 further away from the surface of the donor substrate. In one case, applying current through the stack changes the temperature. Here, electrodes 2302 and 2306 can transport current. In another case, a light-absorbing layer, as part of the stack, converts light into heat energy. In yet another case, the stack can resonate to a specific signal frequency, such as microwaves or ultrasound. This resonance can increase the temperature or directly deform the stack.

[0275] Figure 23B illustrates another example, wherein the microdevices 2312, 2314, and 2318 structures on top of the stacked layers 2304, 2308, and 2310 are surrounded by a housing 2322. Furthermore, anchors 2332 and 2326 hold the devices 2312, 2314, and 2318 within the housing structure. The anchors can be attached to either the microdevices or the housing. During the transfer of device 2314 from the donor substrate 2320 to the recipient substrate, the stack 2308 pushes the microdevice 2314 forward. This thrust releases the anchors 2326, allowing the microdevice 2314 to be placed on the surface of the recipient substrate.

[0276] FIG24 illustrates another example of a microdevice on a donor substrate according to an embodiment of the present invention, wherein the microdevice is selectively movable toward or away from the surface of the donor substrate.

[0277] Here, the microdevices 2410, 2414, and 2418 structures on top of the stacked layer 2404 are surrounded by a housing 2422. Furthermore, anchors 2426 and 2428 hold the devices 2410, 2414, and 2418 within the housing structure. During the transfer of device 2414 from the donor substrate to the recipient substrate, the electroactive polymer layer becomes gas 2456, and the pressure generated by this change propels the microdevice 2414 forward. This push / pull force releases the anchors 2426, allowing the microdevice 2414 to be placed on the surface of the recipient substrate. Thermal, optical, electrical, or chemical forces can cause layer 2404 to become gaseous. In one case, the absorbing layer 2458 can absorb light and heat layer 2404-1, generating gas pressure that propels the microdevice forward. Microdevice housing structure

[0278] Some embodiments of the present invention also disclose methods for integrating a monolithic microdevice array into a system substrate or selectively transferring a microdevice array to a system substrate.

[0279] According to one embodiment, a method for integrating microdevices on a backplane may be provided, comprising: providing a microdevice substrate including one or more microdevices; bonding a set of selective microdevices from the substrate to the backplane by connecting pads on the microdevices and corresponding pads on the backplane; and leaving the bonded set of selective microdevices on the backplane by separating the microdevice substrate.

[0280] In one embodiment, an array of microdevices may be formed on a microdevice substrate, wherein the microdevices may be formed by etching one or more planar layers.

[0281] In another embodiment, one or more planarization layers may be formed on a microdevice substrate and cured by temperature, light or other sources.

[0282] In one embodiment, an intermediate substrate may be provided, wherein, in one case, one or more bonding layers may be formed on the intermediate substrate or on the planarization layer.

[0283] In another embodiment, the microdevice substrate can be removed by laser or chemical stripping.

[0284] In one embodiment, the buffer layer may contain openings for connecting the microdevice to the planarization layer. In one case, electrodes may be disposed on the top or bottom of the planarization layer.

[0285] In another embodiment, additional processes may occur after the microdevice substrate is removed, such as removing an additional common layer, or thinning the planarization layer and / or the microdevice.

[0286] In one case, multiple pads may be added to the microdevice. The pads may be conductive or purely for bonding to the system substrate. In one case, a buffer layer may connect at least one microdevice to a test pad. The test pad may be used to bias the microdevice and test its functionality. Testing may be performed at the wafer level or the intermediate (cassette) level. The pads may be accessible at the intermediate level after multiple layers have been removed.

[0287] In one case, the microdevice may have more than one contact on the top side, and the buffer layer may be patterned to connect at least one contact of the microdevice to a test pad.

[0288] In one embodiment, a backplane may be provided. In one case, the backplane may have transistors and other elements for driving microdevices via pixel circuitry. In another case, the backplane may be a substrate without components.

[0289] In one embodiment, one or more pads may be disposed on a backplane for the bonding process. In one case, the pads on the backplane or on the microdevice may generate a pull-out force on the microdevice.

[0290] After the microdevice is transferred to the backplane, it is possible to detect the position / location of the microdevice and adjust the patterning of other layers to match the alignment during the transfer process. In one case, different components can be used to detect the position of the microdevice, such as a camera or probe tip. In another case, the offset in the transfer setup can be used to identify misalignment of the microdevice's position on the system substrate. In yet another case, the color filter or conversion layer can also be adjusted based on the position of the microdevice. In one case, some random offset can be induced in the microdevice's position to reduce optical artifacts.

[0291] In one embodiment, the pattern of the microdevice may be modified (e.g., electrodes that couple the microdevice to a signal, tunable layers such as color filters or color conversions, vias opened in passivation / planarization layers, or backplane layers).

[0292] In one case, the position / shape of the electrodes can be modified based on the position of the microdevice. In another case, there may be some extensions of the electrodes whose position or length can be modified based on the position of the microdevice.

[0293] FIG25A shows a cross-sectional view of a microdevice array on a microdevice substrate according to an embodiment of the present invention. Here, a microdevice substrate 2502 is provided. A microdevice array 2504 may be formed on the microdevice substrate 2502. In one case, the microdevice may be a microLED. In another case, the microdevice may be any microdevice typically manufactured in planar batches, including LEDs, OLEDs, sensors, solid-state devices, integrated circuits, MEMS and / or other electronic components.

[0294] In one embodiment, one or more planar active layers may be formed on the substrate. The planar active layers may include a first bottom conductive layer, a functional layer (e.g., a light-emitting layer), and a second top conductive layer. The microdevice may be generated by etching the planar active layers. In one embodiment, the etching may extend all the way to the microdevice substrate. In another embodiment, partial etching may be present on the planar layer to leave some on the surface of the microdevice substrate. Other layers may be deposited and patterned before or after the formation of the microdevice.

[0295] FIG25B shows a cross-sectional view of a microdevice array having a buffer layer according to an embodiment of the present invention. Here, a buffer layer 2506 may be formed on the microdevice array 2504. The buffer layer 2506 may extend over the surface of the microdevice substrate 2502. The buffer layer may be conductive. In one case, the buffer layer may be a patterned buffer layer. In another case, the buffer layer may be a common buffer layer. In one embodiment, the buffer layer 2506 may include electrodes that can be patterned or used as common electrodes.

[0296] FIG25C shows a cross-sectional view of a microdevice array having a planarization layer according to an embodiment of the present invention. A planarization layer 2508 may be deposited on top of a microdevice substrate 2502 around each microdevice 2504. The planarization layer 2508 may be used for isolation and / or protection of the microdevices. The planarization layer may include polymers such as polyamide, SU8, or BCB. The planarization layer may be cured. In one case, the planarization layer may be cured via temperature, light, or some other source.

[0297] FIG25D shows a cross-sectional view of a microdevice array bonded to an intermediate substrate according to an embodiment of the present invention. In one embodiment, one or more bonding layers 2512 may be formed on a planarization layer 2508. The bonding layer 2512 may be the same as or different from the planarization layer. In another embodiment, the bonding layer may be formed on top of an intermediate substrate (cassette) 2510. The bonding layer may be provided with one or more different forces, such as electrostatic, chemical, physical, or thermal. The bonding layer 2512 may contact the planarization layer 2508. In order to form a contact between the planarization layer and the bonding layer, the bonding layer is cured by pressure, temperature, light, or other sources.

[0298] In one embodiment, after the intermediate substrate 2510 is formed over the bonding layer, the microdevice substrate 2502 can be removed, which can be done by laser or chemical peeling.

[0299] In one embodiment, the buffer layer 2506 may have openings that allow the microdevice 2504 to connect to the planarization layer 2508. This connection can act as an anchor. In one embodiment, the buffer layer may be etched to form a housing, substrate, or anchor that at least partially surrounds each microdevice. After stripping, the anchor can hold the microdevice to the substrate. In another embodiment, the buffer layer can couple at least one of the microdevice pads to an electrode. The electrode can be placed on top of or on the bottom of the planarization layer.

[0300] Figure 25E shows a cross-sectional view of a microdevice array with pads according to an embodiment of the present invention. The microdevice substrate can be removed to enable a flexible system or for post-processing steps performed on the substrate-facing side of the system. After substrate removal, additional processes can be performed. These processes include one of the following: removal of additional common layers or thinning of planarization layers and / or microdevices. In one case, one or more pads 2520 may be added to the microdevice 2504. In one case, these pads may be conductive. In another case, these pads are purely for bonding to the system substrate. In one case, the buffer layer 2506 may be conductive.

[0301] In one embodiment, buffer layer 2506 can connect one or more microdevices to test pads. Test pads can be used to bias microdevices and test their functionality. In one case, testing can be performed at the wafer / substrate level. In another case, testing can be performed at the intermediate (cell) level. Pads are accessible at the intermediate level after multiple layers have been removed.

[0302] In one case, if the microdevice has more than one contact on the top side, the buffer layer may be patterned to connect at least one contact of the microdevice to the test pad.

[0303] FIG26 shows a cross-sectional view of a microdevice array bonded to an intermediate substrate and a backplane according to an embodiment of the present invention. Here, a backplane 2630 may be provided. In one case, the backplane may be manufactured using a TFT process. In another case, the backplane may be manufactured using a chiplet manufactured using complementary metal-oxide-semiconductor (CMOS) or other processes.

[0304] In one embodiment, the backplane may have transistors and other components for driving microdevices via pixel circuitry. In another embodiment, the backplane may be a substrate without components. One or more pads 2622 may be formed on the backplane 2630 to bond the backplane to the microdevice array. In one case, the one or more pads on the backplane may be conductive.

[0305] In one embodiment, the buffer layer 2606 can be removed or deformed to release the microdevice. Pads 2622 on the backplane or pads 2620 on the microdevice can create a pull-out force on the selected microdevice 2640. In another embodiment, the buffer layer 2606 or housing can be etched back, reduced in size, or removed. The housing can be removed from the empty LED dot.

[0306] Figure 27A illustrates the process steps for extracting the position of a microdevice according to an embodiment of the present invention. After the microdevice is transferred to a backplane, the position of the microdevice on the backplane can be detected, and if misalignment exists during the transfer, the patterning of other layers can be adjusted to match this misalignment. The process steps include: step 2702, placing the microdevice on a system substrate; step 2704, extracting the position of the microdevice on the system substrate using a camera, surface profilometer (optical, ultrasonic, electrical) or other components; step 2706, possibly modifying the pattern of the microdevice, wherein the pattern may include one of the following: electrodes coupling the microdevice to signals, a functionally tunable layer (e.g., color conversion or color filter), vias opened in a passivation / planarization layer, or a backplane layer. A reference structure may exist on the system substrate to first calibrate the tool used to extract the position of the microdevice, or the reference may be used to find the relative position of the microdevice.

[0307] In one embodiment, different components can detect the position of the microdevice. For example, a camera, probe tip, surface profilometer (optical, ultrasonic, electrical), or other components can detect / extract the position / location of the microdevice. In another embodiment, offset in the transfer setup can identify misalignment of the position of the microdevice on the system substrate / backplane.

[0308] For example, in one case, metallization patterning can prevent short circuits. In another case, the color filter or color conversion can be adjusted based on the position of the microdevice. This can reduce the tolerance required for placing the microdevice. A random offset can also be induced in the position of the microdevice to reduce optical artifacts.

[0309] Figure 27B illustrates the modification of electrode position / shape based on the position of a microdevice according to one embodiment of the present invention. One or more microdevices 2710, 2712, or 2714 may have contact pads 2706. In one case, the position / shape of electrodes 2702, 2704 may be modified based on the position of microdevices 2710, 2712, 2714. In another case, the position / shape of the electrodes may be modified based on the position of vias. In yet another case, the position of vias in the planarization / passivation layer may be modified according to the position of the microdevices.

[0310] FIG27C shows an extension provided to an electrode according to one embodiment of the present invention. In one case, the position of the electrode 2702 can be modified. And for each electrode, there may be an extension 2720 such that its position or length can be modified based on the position of the microdevices 2710, 2712 or 2714. This can be used for common electrodes or individual electrodes.

[0311] According to one embodiment, a bonding structure may be provided. The bonding structure may include a plurality of microdevices on a donor substrate, each microdevice including one or more conductive pads formed on the surface of the microdevice; and a temporary material for covering at least a portion of each microdevice or the one or more conductive pads, wherein the temporary material is coupled to a current / voltage source to redirect current through the temporary material to the one or more conductive pads. The temporary material includes a conductive material or a non-conductive material, and wherein the temporary conductive material further completely or partially covers the one or more conductive pads.

[0312] According to another embodiment, the method may further include a conductive layer at the donor substrate for coupling a temporary conductive material to a current / voltage source; and a housing structure for covering at least a portion of each microdevice on the donor substrate, wherein the temporary material acts as an anchor inside the housing structure holding the plurality of microdevices in the donor substrate.

[0313] According to another embodiment, the method may further include at least one sacrificial layer between the housing structure and the microdevices, wherein a temporary material is patterned to form an opening on the top surface of the donor substrate. The opening at the top surface of the donor substrate is used to release the microdevices from the sidewalls of the housing structure by removing the sacrificial layer. After the sacrificial layer is removed, the temporary material holds the microdevices in place, and the sacrificial layer is removed by using a chemical etching process or an electromagnetic signal.

[0314] According to other embodiments, after each microdevice is transferred to the recipient substrate by one of the following processes: mechanical process, optical process, thermal process, and chemical process. Conductive traces on the top surface of the donor substrate are connected as one of the following: mesh, column, or row.

[0315] According to some embodiments, a plurality of access points on the top surface of the donor substrate are used to bias temporary material via conductive traces. The temporary material forms a pathway between the surface facing the donor substrate and the surface facing away from the donor substrate.

[0316] According to one embodiment, a method for bonding at least one microdevice to a acceptor substrate is provided. The method includes: forming a stack including electrodes and an electroactive polymer layer on a donor substrate below the at least one microdevice; applying a voltage to the stack to bring the at least one microdevice into contact / proximal range within the surface of the acceptor substrate.

[0317] According to some embodiments, the method may further include: providing a housing structure around the at least one microdevice; and providing anchors to hold the at least one microdevice inside the housing structure.

[0318] According to another embodiment, the anchor releases a microdevice on the surface of the receptor substrate by either a pushing or a pulling force, the stack further comprising an absorption layer that converts light into a thermally altered layer, and an electroactive polymer layer that becomes a gas, and the pressure generated by the alteration pushes the at least one microdevice to the surface of the receptor substrate.

[0319] According to one embodiment, a method for integrating a microdevice onto a backplane may be provided, comprising: forming a buffer layer on or over one or more microdevices extending over a substrate; forming a planarization layer on the buffer layer, the planarization layer comprising a polymer, wherein the polymer comprises one of polyamide, SU8 or BCB; and depositing a bonding layer between the planarization layer and an intermediate substrate.

[0320] According to another embodiment, the method may further include curing the bonding layer after contacting the planarization layer, and removing the microdevice substrate by laser or chemical peeling. The bonding layer is cured by pressure, temperature, or light.

[0321] According to another embodiment, the method may further include removing the microdevice substrate by laser or chemical stripping, and wherein bonding a set of selective microdevices from the substrate to a backplane includes the steps of: aligning the microdevices and the backplane and bringing them into contact; removing a buffer layer to release the microdevices; forming a force to pull out the set of selected microdevices; and bonding the set of selected microdevices to the backplane.

[0322] According to another embodiment, the method may further include providing openings in a buffer layer to allow a microdevice to be connected to a planarization layer. The buffer layer is conductive, wherein the buffer layer connects at least one microdevice to a test pad.

[0323] According to another embodiment, the method may further include: providing an electrode on either the top or bottom of a planarization layer; coupling at least one microdevice to the electrode via a buffer layer; extracting the position of the microdevice on a backplane; and extending the position of the electrode to the extraction position of the microdevice on the backplane, wherein the position of the microdevice is extracted by means of a camera, a probe tip or a surface profilometer.

[0324] In summary, the present invention provides a microdevice integration process and electronic control integration that is transferred to a system substrate. This transfer can be facilitated by various means, including providing temporary materials, breakable anchors on a donor substrate, or a temporary intermediate substrate.

[0325] The foregoing description of one or more embodiments of the invention has been presented for purposes of illustration and description. The foregoing description is not intended to be exhaustive or to limit the invention to the precise forms disclosed. Many modifications and variations are possible in light of the foregoing teachings. It is intended that the scope of the invention is not limited by this detailed description, but rather by the claims appended herein. [Simplified Explanation of the Diagram]

[0009] The invention will be described in more detail with reference to the accompanying drawings, which illustrate preferred embodiments of the invention, in which:

[0010] FIG1A shows a cross-sectional view of a lateral functional structure on a donor substrate according to an embodiment of the present invention;

[0011] FIG1B shows a cross-sectional view of the lateral structure of FIG1A having a current distribution layer deposited thereon according to an embodiment of the present invention;

[0012] FIG1C shows a cross-sectional view of the side structure of FIG1B after patterning the top dielectric conductive layer and depositing the second dielectric layer according to an embodiment of the present invention.

[0013] FIG1D shows a cross-sectional view of a lateral structure after patterning a second dielectric layer according to an embodiment of the present invention;

[0014] FIG1E shows a cross-sectional view of the lateral structure after pad deposition and patterning according to an embodiment of the present invention;

[0015] FIG1F shows a cross-sectional view of the side structure after bonding to the system substrate via the bonding region to form an integrated structure according to an embodiment of the present invention;

[0016] FIG1G shows a cross-sectional view of the integrated structure after removing the donor substrate and the patterned bottom electrode according to an embodiment of the present invention;

[0017] FIG1H shows a cross-sectional view of the integrated structure after removing the donor substrate and the patterned bottom electrode according to an embodiment of the present invention;

[0018] FIG2A shows a cross-sectional view of another embodiment of a lateral functional structure on a donor substrate having a pad layer;

[0019] FIG2B shows a cross-sectional view of the side structure of FIG2A after the patterned pad layer, contact layer and current distribution layer according to an embodiment of the present invention;

[0020] FIG2C shows a cross-sectional view of the side structure of FIG2A after filling the distance between the patterned pads according to an embodiment of the present invention;

[0021] FIG2D shows a cross-sectional view of the side structure of FIG2A by patterned pad alignment and bonding to the system substrate according to an embodiment of the present invention;

[0022] FIG2E shows a cross-sectional view of the side structure of FIG2A of the removal device substrate according to an embodiment of the present invention;

[0023] FIG3A shows a cross-sectional view of the mesa structure on the substrate of the device (donor) according to an embodiment of the present invention;

[0024] FIG3B shows a cross-sectional view of the steps according to an embodiment of the present invention, wherein the blank space between the tabletop structures of FIG3A is filled;

[0025] FIG3C shows a cross-sectional view of the steps according to an embodiment of the present invention, wherein the device (mesa structure) of FIG3B is transferred to a temporary substrate;

[0026] FIG3D shows a cross-sectional view of the steps according to an embodiment of the present invention, wherein the device of FIG3C is aligned and bonded to a system substrate;

[0027] FIG3E shows a cross-sectional view of the steps according to an embodiment of the present invention, wherein the device is transferred to the system substrate;

[0028] Figure 3F shows the thermal curve of the heat transfer step according to an embodiment of the present invention;

[0029] FIG4A shows a cross-sectional view of a temporary substrate having a groove and a means for transferring thereon according to an embodiment of the present invention;

[0030] FIG4B shows a cross-sectional view of the temporary substrate of FIG4A after cleaning the filler between the device space and the tank according to an embodiment of the present invention;

[0031] FIG4C shows a cross-sectional view of the steps according to an embodiment of the present invention, wherein the device is transferred to the system substrate by breaking the released surface;

[0032] FIG5A shows a cross-sectional view of a microdevice with different anchors in the filler layer according to an embodiment of the present invention;

[0033] FIG5B shows a cross-sectional view of a microdevice after post-processing of the filler layer according to an embodiment of the present invention;

[0034] FIG5C shows a top view of the microdevice of FIG5B according to an embodiment of the present invention;

[0035] FIG5D shows a cross-sectional view of a transfer step for transferring a microdevice to another substrate according to an embodiment of the present invention;

[0036] FIG5E shows a cross-sectional view of transferring a microdevice to a substrate according to an embodiment of the present invention;

[0037] FIG6A shows a cross-sectional view of a mesa structure on a device (donor) substrate according to another embodiment of the present invention;

[0038] Figure 6B shows a cross-sectional view of the step, in which the blank space between the tabletop structures of Figure 6A is filled;

[0039] FIG6C shows a cross-sectional view of the steps according to an embodiment of the present invention, wherein the device (mesa structure) of FIG6B is transferred to a temporary substrate;

[0040] FIG6D shows a cross-sectional view of the steps according to an embodiment of the present invention, wherein a portion of the bottom conductive layer of FIG6C is removed;

[0041] FIG6E shows a cross-sectional view of a microdevice having anchors in a filler layer according to an embodiment of the present invention;

[0042] FIG6F shows a cross-sectional view of a microdevice having anchors in a filler layer according to an embodiment of the present invention;

[0043] FIG6G shows a cross-sectional view of a microdevice having anchors in a filler layer according to an embodiment of the present invention;

[0044] Figure 6H shows a cross-sectional view of the preparatory steps in another embodiment of the present invention;

[0045] FIG6I shows a cross-sectional view of the etching step in the embodiment of FIG6H according to an embodiment of the present invention;

[0046] FIG6J shows a cross-sectional view of the separation step in the embodiment of FIG6H according to an embodiment of the present invention;

[0047] FIG6K shows a top view of another embodiment of the present invention according to an embodiment of the present invention;

[0048] FIG6L shows a cross-sectional view of the embodiment of FIG6K according to an embodiment of the present invention;

[0049] FIG6M shows a cross-sectional view of the embodiment of FIG6K and 6L having a filling material according to an embodiment of the present invention;

[0050] Figure 7 is a flowchart of an embodiment of the present invention;

[0051] Figure 8 is a flowchart of the microdevice installation process according to an embodiment of the present invention;

[0052] Figure 9 is a flowchart of the microdevice installation process according to an embodiment of the present invention;

[0053] Figure 10 is a flowchart of the microdevice installation process according to an embodiment of the present invention;

[0054] FIG11 shows an example of a donor or temporary (cassette) substrate having different types of pixelated microdevices according to an embodiment of the present invention;

[0055] FIG12 shows an example of a donor or temporary (cassette) substrate having different types of pixelated microdevices according to an embodiment of the present invention;

[0056] FIG13 shows an example of a donor substrate for the same type of microdevice but with different spacing between microdevice groups according to an embodiment of the present invention;

[0057] FIG14A shows an example of a donor substrate or temporary substrate having non-uniform output on a microdevice block according to an embodiment of the present invention;

[0058] FIG14B shows an example of a receptor substrate or system substrate having non-uniform output on multiple microdevice blocks according to an embodiment of the present invention;

[0059] FIG14C shows an example of a system substrate having a skewed microdevice block according to an embodiment of the present invention;

[0060] FIG14D shows an example of a system substrate having a flip microdevice block according to an embodiment of the present invention;

[0061] FIG14E shows an example of a system substrate having flipped and alternating microdevice blocks according to an embodiment of the present invention;

[0062] FIG15A shows an example of a donor substrate having two different microdevice blocks according to an embodiment of the present invention;

[0063] FIG15B shows an example of a system substrate with skew blocks having different microdevices according to an embodiment of the present invention;

[0064] FIG16A shows an example of a donor substrate having three different types of pixelated microdevice blocks according to an embodiment of the present invention;

[0065] FIG16B shows an example of a system substrate having multiple different types of individual microdevices from each block according to an embodiment of the present invention;

[0066] FIG17A shows an example of a cassette substrate having various different types of pixelated microdevice blocks according to an embodiment of the present invention;

[0067] FIG17B shows an example of a cassette substrate having various types of offset pixelated microdevice blocks according to an embodiment of the present invention;

[0068] FIG18 shows a donor substrate for holding a microdevice via a donor force element according to an embodiment of the present invention.

[0069] Figure 19 shows an example of a microdevice having one or more contact pads on one side according to an embodiment of the present invention.

[0070] Figures 20A1-20A2 illustrate examples of microdevices with prominent temporary conductive material coverings according to some embodiments of the present invention.

[0071] Figures 20B1-20B2 show another example of a microdevice with a prominent temporary conductive material covering according to some embodiments of the present invention.

[0072] Figures 20C1-20C2 show another example of a microdevice with a prominent temporary conductive material covering according to some embodiments of the present invention.

[0073] Figures 20D-20H show another example of a microdevice covered with a prominent temporary conductive material according to some embodiments of the present invention.

[0074] Figures 20I1-20I2 show another example of a microdevice covered with a prominent temporary conductive material according to some embodiments of the present invention.

[0075] FIG21A shows an exemplary top view representation of FIG20A according to an embodiment of the present invention.

[0076] FIG21B1 shows an exemplary top view representation of FIG20B1 according to an embodiment of the present invention.

[0077] FIG21B2 shows another exemplary top view representation of FIG20B2 according to an embodiment of the present invention.

[0078] FIG21C shows an exemplary top view representation of FIG20E according to an embodiment of the present invention.

[0079] FIG21D shows an exemplary top view representation of FIG20F according to an embodiment of the present invention.

[0080] Figures 22A-22C illustrate microdevices on a donor substrate according to an embodiment of the present invention, wherein the microdevices are selectively movable toward or away from the surface of the donor substrate.

[0081] Figures 23A-23B illustrate microdevices on a donor substrate according to an embodiment of the present invention, wherein the microdevices are selectively movable toward or away from the surface of the donor substrate.

[0082] FIG24 illustrates another example of a microdevice on a donor substrate according to an embodiment of the present invention, wherein the microdevice is selectively movable toward or away from the surface of the donor substrate.

[0083] FIG25A shows a cross-sectional view of a microdevice array on a microdevice substrate according to an embodiment of the present invention.

[0084] FIG25B shows a cross-sectional view of a microdevice array having a patterned buffer layer according to an embodiment of the present invention.

[0085] FIG25C shows a cross-sectional view of a microdevice array having a planarization layer according to an embodiment of the present invention.

[0086] FIG25D shows a cross-sectional view of an array of microdevices bonded to an intermediate substrate according to an embodiment of the present invention.

[0087] FIG25E shows a cross-sectional view of a microdevice array with pads according to an embodiment of the present invention.

[0088] FIG26 shows a cross-sectional view of a microdevice array bonded to an intermediate substrate and a backplane according to an embodiment of the present invention.

[0089] Figure 27A illustrates the process steps for extracting the location of a microdevice according to an embodiment of the present invention.

[0090] Figure 27B shows the position / shape of a microdevice-based position modification electrode according to an embodiment of the present invention.

[0091] FIG27C shows an extension provided to an electrode according to an embodiment of the present invention.

[0092] If the same reference numerals are used in different drawings, they indicate similar or identical elements.

[0093] This invention allows for various modifications and alternatives, and specific embodiments or implementations are shown as examples in the drawings and will be described in detail herein. However, the invention is not limited to the specific forms disclosed. In fact, the invention covers all modifications, equivalents, and alternatives that fall within the spirit and scope of the invention as defined by the appended claims.

Claims

1. A method for integrating a microdevice into a system substrate, the method comprising: Multiple microdevices are held on a donor substrate by a donor force element, wherein the donor force element is a component that loses its adhesive properties under current or voltage; conductive pads are provided on both the top and bottom of the stack of semiconductor layers on the multiple microdevices on the donor substrate; at least one receiver force element is provided in the receiver substrate for each selected microdevice selected for transfer to the receiver substrate; and a voltage / current is applied to the donor force element holding the selected microdevice for transfer.

2. The method of claim 1, wherein the donor force element is a polymer that decomposes under the application of charge.

3. The method of claim 1, wherein the power supply element is a high-resistivity trace burned at an applicable current / voltage.

4. The method of claim 1, wherein the receiving force element comprises a monomer that forms a polymer under an applicable charge.

5. The method of claim 1, wherein the receiving force element is a medium having a high-resistivity trace that generates heat under an applicable current / voltage, and the generated heat causes the medium to locally solidify.

6. The method of claim 1, wherein the microdevice has two conductive / contact pads at the bottom of the stack of semiconductor layers on the donor substrate.

7. The method of claim 6, wherein the acceptor substrate has an acceptor force element corresponding to a contact pad for each microdevice selected for transfer to the acceptor substrate.

8. The method of claim 1, wherein the microdevice is used as part of a bias circuit.

9. The method of claim 8, wherein a voltage / current is applied via the donor substrate or a voltage / current is applied to the acceptor substrate, the voltage / current passing through the microdevice and through either the donor substrate or the acceptor substrate.

Images