Integrating micro devices into a system substrate

Abstract

This application relates to the integration of microdevices into a system substrate. In the microdevice integration process, a donor substrate is provided, on which initial fabrication and pixellation steps will be performed to define microdevices, which include a functional layer, such as a light-emitting layer, sandwiched between a top conductive layer and a bottom conductive layer. The microdevices are then transferred to a system substrate for finalization and electronic control integration. The transfer can be facilitated in various ways, including providing a continuous light-emitting functional layer, breakable anchors on the donor substrate, a temporary intermediate substrate that enables thermal transfer techniques, or a temporary intermediate substrate with a breakable substrate bonding layer.

Description

[0001] Cross-references to related applications

[0002] This application is a partial continuation-in-place of U.S. Application No. 15 / 820,683, filed November 22, 2017, and claims priority to it, which claims priority and benefit to 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.

[0003] 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.

[0004] This application further claims the benefit of U.S. Provisional Patent Application No. 62 / 746,300, filed October 16, 2018, which is incorporated herein by reference in its entirety. Technical Field

[0005] This disclosure relates to optoelectronic microdevices, and more particularly to integrating optoelectronic microdevices into system substrates with enhanced bonding and conductivity. Background Technology

[0006] The purpose of this invention is to overcome the shortcomings of the prior art by providing a system and method for transferring microdevices from a donor substrate to a system substrate. Summary of the Invention

[0007] According to one embodiment of the present invention, a method of 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; attaching the bonding contacts to a system substrate; and removing the donor substrate.

[0008] In one embodiment, sequential pixelation is used to turn the microdevices into an array.

[0009] In another embodiment, the device is separated and transferred to an intermediate substrate by filling the gaps between the microdevices.

[0010] In another embodiment, the microdevice is post-processed after being transferred to an intermediate substrate.

[0011] 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.

[0012] 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 selective set of microdevices from the substrate to the backplane; and separating the microdevice substrate to leave the selected set of bonded microdevices on the backplane. Attached Figure Description

[0013] The invention will be described in more detail with reference to the accompanying drawings, which illustrate preferred embodiments of the invention, in which:

[0014] Figure 1A A cross-sectional view of a lateral functional structure on an donor substrate according to an embodiment of the present invention is shown;

[0015] Figure 1B An embodiment of the present invention is shown having a current distribution layer deposited thereon. Figure 1A A cross-sectional view of the lateral structure;

[0016] Figure 1C This illustrates an embodiment of the invention following the patterning of a top dielectric conductive layer and the deposition of a second dielectric layer. Figure 1B A cross-sectional view of the lateral structure;

[0017] Figure 1D A cross-sectional view of a lateral structure after patterning a second dielectric layer is shown according to an embodiment of the present invention;

[0018] Figure 1E A cross-sectional view of the lateral structure after pad deposition and patterning according to an embodiment of the present invention is shown;

[0019] Figure 1F A cross-sectional view of a lateral structure after bonding to a system substrate via bonding regions to form an integrated structure, according to an embodiment of the present invention, is shown.

[0020] Figure 1G A cross-sectional view of the integrated structure after removing the donor substrate and patterned bottom electrode, according to an embodiment of the present invention, is shown.

[0021] Figure 1H A cross-sectional view of the integrated structure after removing the donor substrate and patterned bottom electrode, according to an embodiment of the present invention, is shown.

[0022] Figure 2A A cross-sectional view showing another embodiment of a lateral functional structure on an donor substrate with a pad layer;

[0023] Figure 2B This illustrates an embodiment of the invention following a patterned pad layer, a contact layer, and a current distribution layer. Figure 2A A cross-sectional view of the lateral structure;

[0024] Figure 2C This illustrates the effect of filling the distance between patterned pads according to an embodiment of the invention. Figure 2A A cross-sectional view of the lateral structure;

[0025] Figure 2D This demonstrates an embodiment of the invention involving patterned pad alignment and bonding to a system substrate. Figure 2A A cross-sectional view of the lateral structure;

[0026] Figure 2E This illustrates the removal of the device substrate according to an embodiment of the present invention. Figure 2A A cross-sectional view of the lateral structure;

[0027] Figure 3A A cross-sectional view of a mesa structure on a device (applier) substrate according to an embodiment of the present invention is shown;

[0028] Figure 3B A cross-sectional view showing the steps according to an embodiment of the invention is illustrated, wherein the steps are filled with... Figure 3A The blank space between the countertop structures;

[0029] Figure 3C A cross-sectional view of the steps according to an embodiment of the present invention is shown, wherein... Figure 3B The device (mesa structure) is transferred to a temporary substrate;

[0030] Figure 3D A cross-sectional view of the steps according to an embodiment of the present invention is shown, wherein... Figure 3C The device is aligned and bonded to the system substrate;

[0031] Figure 3EA cross-sectional view of the steps according to an embodiment of the present invention is shown, wherein the device is transferred to a system substrate;

[0032] Figure 3F The thermal profiles of the heat transfer steps according to an embodiment of the present invention are shown;

[0033] Figure 4A A cross-sectional view of a temporary substrate having grooves and means for transferring thereon is shown according to an embodiment of the present invention;

[0034] Figure 4B This illustrates the process of cleaning the packing material between the device space and the tank according to an embodiment of the present invention. Figure 4A A cross-sectional view of the temporary substrate;

[0035] Figure 4C A cross-sectional view of the steps according to an embodiment of the invention is shown, wherein the device is transferred to a system substrate by breaking the released surface;

[0036] Figure 5A A cross-sectional view of a microdevice with different anchors in a filler layer is shown according to an embodiment of the present invention;

[0037] Figure 5B A cross-sectional view of a microdevice after post-processing of the filler layer is shown according to an embodiment of the present invention;

[0038] Figure 5C An embodiment of the present invention is shown. Figure 5B A top view of the microdevice;

[0039] Figure 5D A cross-sectional view is shown illustrating a transfer step for transferring a microdevice to another substrate according to an embodiment of the present invention;

[0040] Figure 5E A cross-sectional view of transferring a microdevice to a substrate according to an embodiment of the present invention is shown;

[0041] Figure 6A A cross-sectional view of a mesa structure on a device (applier) substrate according to another embodiment of the present invention is shown;

[0042] Figure 6B A cross-sectional view of the steps is shown, in which the steps are filled. Figure 6A The blank space between the countertop structures;

[0043] Figure 6C A cross-sectional view of the steps according to an embodiment of the present invention is shown, wherein... Figure 6B The device (mesa structure) is transferred to a temporary substrate;

[0044] Figure 6D A cross-sectional view of the steps according to an embodiment of the present invention is shown, wherein the removal Figure 6C The bottom conductive layer portion;

[0045] Figure 6E A cross-sectional view of a microdevice having anchors in a filler layer is shown according to an embodiment of the present invention;

[0046] Figure 6F A cross-sectional view of a microdevice having anchors in a filler layer is shown according to an embodiment of the present invention;

[0047] Figure 6G A cross-sectional view of a microdevice having anchors in a filler layer is shown according to an embodiment of the present invention;

[0048] Figure 6H A cross-sectional view is shown of a preparatory step in another embodiment of the invention;

[0049] Figure 6I This illustrates an embodiment of the invention. Figure 6H Cross-sectional view of the etching step in the embodiment;

[0050] Figure 6J This illustrates an embodiment of the invention. Figure 6H Cross-sectional view of the separation step in the embodiment;

[0051] Figure 6K A top view of another embodiment of the invention according to an embodiment of the invention is shown;

[0052] Figure 6L An embodiment of the present invention is shown. Figure 6K A cross-sectional view of an embodiment;

[0053] Figure 6M An embodiment of the invention is shown with a filling material. Figure 6K and 6L A cross-sectional view of an embodiment;

[0054] Figure 7 This is a flowchart of a process according to an embodiment of the present invention;

[0055] Figure 8 This is a flowchart of the microdevice installation process according to an embodiment of the present invention;

[0056] Figure 9 This is a flowchart of the microdevice installation process according to an embodiment of the present invention;

[0057] Figure 10 This is a flowchart of the microdevice installation process according to an embodiment of the present invention;

[0058] Figure 11 Examples of donor or temporary (cassette) substrates having different types of pixelated microdevices are shown according to embodiments of the present invention;

[0059] Figure 12 Examples of donor or temporary (cassette) substrates having different types of pixelated microdevices are shown according to embodiments of the present invention;

[0060] Figure 13 Examples of donor substrates with different spacings between groups of microdevices but for the same type of microdevice are shown according to embodiments of the present invention.

[0061] Figure 14A Examples of donor substrates or temporary substrates having non-uniform output on a microdevice block are shown according to embodiments of the present invention;

[0062] Figure 14B Examples of acceptor substrates or system substrates having non-uniform output on multiple microdevice blocks are shown according to embodiments of the present invention;

[0063] Figure 14C An example of a system substrate with a skewed microdevice block is shown according to an embodiment of the present invention;

[0064] Figure 14D An example of a system substrate with a flip microdevice block according to an embodiment of the present invention is shown;

[0065] Figure 14E An example of a system substrate having flipped and alternating microdevice blocks according to an embodiment of the present invention is shown;

[0066] Figure 15A An example of an donor substrate having two different microdevice blocks according to an embodiment of the present invention is shown;

[0067] Figure 15B Examples of system substrates with skew blocks having different microdevices are shown according to embodiments of the present invention;

[0068] Figure 16A Examples of donor substrates having three different types of pixelated microdevice blocks according to embodiments of the present invention are shown;

[0069] Figure 16B An example of a system substrate having multiple different types of individual microdevices from each block is shown according to an embodiment of the present invention;

[0070] Figure 17A Examples of cassette substrates having various different types of pixelated microdevice blocks are shown according to embodiments of the present invention;

[0071] Figure 17B Examples of cassette substrates having various different types of offset pixelated microdevice blocks are shown according to embodiments of the present invention;

[0072] Figure 18 A donor substrate for holding a microdevice via a donor force element is shown according to an embodiment of the invention.

[0073] Figure 19 An example of a microdevice having one or more contact pads on one side according to an embodiment of the present invention is shown.

[0074] Figures 20A1-20A2 Examples of microdevices with a prominent temporary conductive material covering them are shown according to some embodiments of the present invention.

[0075] Figures 20B1-20B2 Another example of a microdevice covered with a highlighting temporary conductive material is shown according to some embodiments of the invention.

[0076] Figure 20C1-20C2 Another example of a microdevice covered with a highlighting temporary conductive material is shown according to some embodiments of the invention.

[0077] Figure 20D-20H Another example of a microdevice covered with a highlighting temporary conductive material is shown according to some embodiments of the invention.

[0078] Figures 20I1-20I2 Another example of a microdevice covered with a highlighting temporary conductive material is shown according to some embodiments of the invention.

[0079] Figure 21A An exemplary top view of FIG20A is shown according to an embodiment of the present invention.

[0080] Figure 21B1 An embodiment of the invention is shown. Figure 20B1 An exemplary top view representation.

[0081] Figure 21B2 An embodiment of the invention is shown. Figure 20B2 Another exemplary top view representation.

[0082] Figure 21C An embodiment of the invention is shown. Figure 20E An exemplary top view representation.

[0083] Figure 21D An embodiment of the invention is shown. Figure 20F An exemplary top view representation.

[0084] Figures 22A-22CA microdevice on a donor substrate is shown according to an embodiment of the invention, wherein the microdevice is selectively movable toward or away from the surface of the donor substrate.

[0085] Figures 23A-23B A microdevice on a donor substrate is shown according to an embodiment of the invention, wherein the microdevice is selectively movable toward or away from the surface of the donor substrate.

[0086] Figure 24 Another example of a microdevice on a donor substrate is shown according to an embodiment of the invention, wherein the microdevice is selectively movable toward or away from the surface of the donor substrate.

[0087] Figure 25A A cross-sectional view of a microdevice array on a microdevice substrate according to an embodiment of the present invention is shown.

[0088] Figure 25B A cross-sectional view of a microdevice array having a patterned buffer layer is shown according to an embodiment of the present invention.

[0089] Figure 25C A cross-sectional view of a microdevice array having a planarization layer is shown according to an embodiment of the present invention.

[0090] Figure 25D A cross-sectional view of an array of microdevices bonded to an intermediate substrate according to an embodiment of the present invention is shown.

[0091] Figure 25E A cross-sectional view of a microdevice array with pads according to an embodiment of the present invention is shown.

[0092] Figure 26 A cross-sectional view of an array of microdevices bonded to an intermediate substrate and a backplane according to an embodiment of the present invention is shown.

[0093] Figure 27A The process steps for extracting the location of a microdevice according to an embodiment of the present invention are shown.

[0094] Figure 27B The position / shape of a microdevice-based position modification electrode is shown according to an embodiment of the present invention.

[0095] Figure 27C An extension provided to an electrode according to an embodiment of the present invention is shown.

[0096] If the same reference numerals are used in different drawings, they indicate similar or identical elements.

[0097] This disclosure 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, this disclosure is not limited to the specific forms disclosed. In fact, this disclosure covers all modifications, equivalents, and alternatives that fall within the spirit and scope of the invention as defined by the appended claims. Detailed Implementation

[0098] While the teachings of the present invention have been described in conjunction with various embodiments and examples, the teachings are not intended to be limited to these embodiments. Rather, the teachings encompass various alternatives and equivalents, as will be understood by those skilled in the art.

[0099] 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 to which this invention pertains.

[0100] As used in this specification and claims, unless the context clearly indicates otherwise, the singular forms “a / an” and “the” include multiple referents.

[0101] 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.

[0102] In this specification, the terms "donor substrate" and "temporary substrate" are used interchangeably.

[0103] In this specification, the terms “receptor substrate,” “system substrate,” and “backplate” are used interchangeably.

[0104] Examples of optoelectronic devices include sensors and light-emitting devices, such as light-emitting diodes (LEDs).

[0105] This disclosure 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.

[0106] 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 intrinsic substrate of the device layer or a acceptor substrate to which the device layer or solid-state device is transferred.

[0107] The acceptor substrate can be any substrate and can be rigid or flexible. The acceptor substrate may include (but is not limited to) printed circuit boards, thin-film transistor (TFT) backplanes, integrated circuit substrates, or, in the case of an optical microdevice such as an LED, components of a display such as a driver circuit backplane. Microdevice patterning on the device donor and acceptor substrates can be combined 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).

[0108] In this disclosure, contact pads in the acceptor substrate refer to designated areas in the acceptor substrate to which the microdevice has been 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.

[0109] The system substrate can 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 the system substrate. In some cases, the system substrate may be a substrate with rows and columns of electrical signals. The system substrate may be a backplane with circuitry for routing the microLED device.

[0110] Figure 1A An embodiment of a donor substrate 110 with a lateral functional structure is shown, the lateral functional structure including 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, such as... Figure 1B As shown, 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, patterning can be performed by lift-off. In another, patterning can be performed 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 can be deposited over and between the patterned conductive layer 116 and the current distribution layer 118, as shown. Figure 1C As shown. The dielectric layer 120 can also be patterned to produce, for example... Figure 1D The opening 130 shown provides a pathway to the current distribution layer 118. An additional leveling layer 128 may also be provided to smooth the upper surface, such as... Figure 1E As shown.

[0111] like Figure 1E As shown, 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. Figure 1F As shown, the pads 154 in the system substrate 150 can be separated by the dielectric layer 156. Other layers 152, such as circuitry, planarization layers, and conductive traces, can 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 can also be deposited between the system device and the side device.

[0112] like Figure 1G As shown, the donor substrate 110 can be removed from lateral functional devices, such as 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 areas on the conductive layer 112 between pixels. 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 light generated by 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. Dielectric layers in these devices, such as dielectric layer 120, can be organic materials such as polyamide or inorganic materials such as SiN, SiO2, Al2O3. The 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. Bonding materials can be deposited only as a portion of the pads 132 of the donor substrate 110 or the system substrate pads 154. For some of the 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.

[0113] Figure 2A An exemplary embodiment of an donor substrate 210 with a lateral functional structure is shown, the lateral functional structure including 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. Figure 2BAll or one of patterned layers 216, 218, and 232 are shown to form a pixel structure. Conductive layers 212 and 216 can be composed of multiple layers including highly doped semiconductor layers. Layers 228, such as dielectrics, can be used between patterned layers 216, 218, and 232 to flatten the upper surface of the lateral functional structure, such as... Figure 2C As shown. Layer 228 can 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. Figure 2D As shown. The pads 254 in the system substrate can also be separated by the dielectric layer 256. Other layers 252, such as circuitry, planarization layers, and conductive traces, can exist between the system substrate pads 254 and the system substrate 250. These bonds can be performed, for example, by fusion bonding, anodic bonding, thermoforming bonding, eutectic bonding, or adhesive bonding. Other layers can also be deposited between the system device and the side device.

[0114] 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. The 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 the layers, an annealing process may also be present. For example, the current distribution layer 218 can be annealed depending on the material. In this example, the current distribution layer can be annealed at 500°C for 10 minutes. Annealing can also be performed after different steps.

[0115] exist Figure 3AIn another embodiment shown, 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 can be deposited before or after etching the top of the top conductive layer 316. In another case, multilayer contacts 332 can be used. In this case, a portion of the contact layer 332 can be deposited before etching, and a portion of the contact layer can be deposited after etching. For example, an initial contact layer can be deposited first to create ohmic contacts by annealing the conductive layer 316. In one example, the initial contact layer can be gold or nickel. Other layers 372, such as dielectrics or metal insulator structures (MIS), can also be used between the mesa structures to isolate and / or insulate each structure. After forming the microdevice, a filler layer 374, such as polyamide, can be deposited. Figure 3B As shown. If the selected microdevice is transferred only to the cassette (temporary) substrate 376 during the following steps, the filler layer 374 can be patterned. The filler layer 374 can also be deposited after the device has been transferred to the temporary substrate. The filler layer 374 can act as a housing for the microdevice. If the filler layer 374 is used before the transfer, the lift-off process may be more reliable.

[0116] The device is bonded to a temporary substrate (cassette) 376. For example, the bonding source can 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 T1 can 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 can be used to bias the device on the substrate 376 to identify defects and characterize device performance. This structure can be used in other embodiments presented herein. To address some surface profile inhomogeneity, pressure can be applied during the bonding process. The temporary substrate 376 or the donor substrate 310 can 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 can 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, such as... Figure 3D and 3EAs shown. Different techniques can be used to perform the transfer. 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 pad 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 pad 382.

[0117] In subsequent steps, the temperature is lowered to between T1 and T2. At this point, 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, moving the temporary substrate 376 keeps the microdevice on the system substrate 390, as... Figure 3E As shown. The process can be made selective by applying localized heating to the selected pad 382. Furthermore, 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 close to the melting point of the contact bonding layer 380, for example, between 5°C and 10°C below 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. Alternatively, the temperature can be raised to close to the melting point of the substrate bonding layer 378 (above the melting point of the contact bonding layer 378), for example, between 5°C and 10°C below the 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 temperature transfer from the pad 382 through the device.

[0118] Figure 3FAn example of a thermal profile is shown, where a melting temperature Tr melts the contact bonding layer 380 and the substrate bonding layer 378, and a curing temperature Ts cures the contact bonding layer 380 with 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 can 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 can include planarization, electrode deposition, color conversion deposition and patterning, color filter deposition and patterning, etc.

[0119] 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 molten (or soft enough) 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.

[0120] In another embodiment, a filler layer 374 may be deposited on top of a cartridge substrate 376 to form a polymer filler / bonding layer 374 / 378. A microdevice from a 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 in cases where 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. Another polymer filler / bonding layer 374 / 378 may then be deposited and patterned for the next type of microdevice. A second microdevice may then be embedded in the associated layer 374 / 378. In all cases, the polymer filler / bonding layer 374 / 378 can cover part or all of the device in a microdevice.

[0121] Another method to increase the temperature is to use microwaves or lamps. Therefore, layers can 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 contain heating elements that selectively and / or globally heat the microdevice.

[0122] Other methods can 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 can be used to cover the microdevice, which can be debonded to the temporary substrate 376 by chemical, optical, thermal, or mechanical forces. The debonding process can be selective or global. Global debonding transfer to the system substrate 390 is selective. If the debonding process of the device from the temporary substrate (cassette) 376 is selective, transfer forces can be applied selectively or globally to the system substrate 390.

[0123] The transfer process from cartridge 376 to acceptor substrate 390 can be based on different mechanisms. In one case, 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.

[0124] In another embodiment, the temperature of the bonding layer 380 used to solidify the device to the acceptor substrate 390 causes the device to be released from the cartridge 376.

[0125] In another scenario, a current or voltage causes the bonding layer 380 of the device to the donor substrate 310 to solidify. The same current or voltage can then release the device from the housing 376. Here, the release can be a function of the piezoelectric effect generated by the current or temperature.

[0126] In another method, after the device is bonded to the acceptor substrate 390, the bonded device is pulled out of 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.

[0127] In another approach, cartridge 376 has vias that can be used to push a device out of cartridge 376 and into receiver substrate 390. This pushing can be performed in different ways, such as using an array of microrods or by pneumatic means. For pneumatic structures, the selected device is disconnected. For microrods, the selected device is moved toward receiver substrate 390 by passing the microrods through their associated vias. 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 vias of another set of microdevices, or a new device is transferred using a set of vias aligned with a new selected microdevice.

[0128] In one embodiment, the box 376 can be stretched to increase the spacing between devices within the box 376, thereby increasing production capacity. For example, if the box 376 is 1×1cm... 2 If the device pitch is 5 micrometers and the pixel pitch of the acceptor substrate 390 (e.g., a display) is 50 micrometers, then the cell 376 can fill 200 × 200 (40,000) pixels at a time. However, if the cell 376 is stretched to 2 × 2 cm... 2 With a device pitch of 10 micrometers, the cell 376 can fill 400 × 400 (160,000) pixels at a time. Alternatively, the cell 376 can be stretched such that at least two microdevices on the cell 376 align with two corresponding locations in the acceptor substrate. This stretching can be performed in one or more directions. The cell substrate 376 can comprise or be composed of a stretchable polymer. The microdevices are also anchored in another layer or the same layer as the cell substrate 376.

[0129] The methods described above can also be combined to transfer the microdevice from the cassette 376 to the acceptor substrate 390.

[0130] During the generation of the cell (temporary substrate) 376, the microdevice can be tested to identify different 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 yet 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.

[0131] The above text is about Figures 3A-3D The methods described—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.

[0132] The method discussed herein for transferring a microdevice from a cassette (temporary substrate) 376 to a receiver substrate 390 can be applied to all cassette and receiver substrate configurations presented herein.

[0133] The device on donor substrate 310 can be fabricated to have two contacts 332 and 380 on the same side opposite to donor substrate 310. In this embodiment, a conductive layer on cartridge 376 can be patterned to independently bias the two contacts 332 and 380 of the device. In one case, the device can be transferred directly from cartridge substrate 376 to acceptor substrate 390. Here, contacts 332 and 380 may not be directly bonded to acceptor substrate 390, i.e., acceptor substrate 390 does not need to have special pads. In this case, a conductive layer is deposited and patterned to connect contacts 332 and 380 to appropriate connections in acceptor substrate 390. In another embodiment, the device can be transferred from cartridge 376 to a temporary substrate before being transferred to acceptor substrate 390. Here, contacts 332 and 380 can be directly bonded to acceptor substrate pad 382. The device can be tested in cartridge 376 or in a temporary substrate.

[0134] exist Figure 4A In another embodiment shown, a mesa structure as described above is formed on the 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.

[0135] The temporary substrate 476 comprises multiple 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. Furthermore, each microdevice may include additional passivation layers and / or MIS layers 472 surrounding each microdevice for isolation and / or protection. The spaces 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 can then be removed, and the trenches can be emptied by various suitable methods such as, for example, chemical etching or evaporation, to induce or facilitate the release of the surface and / or selected segments of the bonding layer 478. A process similar to that described above can be used to transfer the device to the system (receiver) substrate 490. Alternatively, in another embodiment, a force applied from the pad 432, such as a push or pull, may disrupt the surface and / or bonding layer 478 above the emptied trench 476-2 while maintaining the unselected mesa structure attached to the temporary substrate. This force can also release the device from the temporary substrate 476, as... Figure 4B and Figure 4C As shown. The depth of slot 476-2 can be selected to manage some of the height differences of the microdevices. For example, if the height difference is H, the depth of the slot can be greater than H.

[0136] The device on substrate 310 can be fabricated to have two contacts 432 and 480 on the same side opposite to substrate 310. In this case, a 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, a 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 a 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 on a temporary substrate.

[0137] exist Figure 5AIn another embodiment shown, 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 removal. The removal can 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 laser light 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 the device before the removal process. In another case, a filler layer 574, such as a dielectric, can be used between the devices.

[0138] In the first illustrated embodiment, layer 592 is provided to hold the device to the donor substrate 510. Layer 592 can be a separate layer or a portion of the microdevice layer that is not etched during mesa structure formation. In another embodiment, layer 592 can be a continuation of one of layers 572. In this case, layer 592 can be a metal layer or a dielectric layer (SiN or SiO2 or other materials). In yet 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 can later be removed to create void / gap 596. Extension 594 can also be avoided. Similar to the previous anchor 592, another anchor can be composed of a different structural layer. In yet 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.

[0139] Figure 5B Samples are shown after the removal of filler layer 574 and / or etching of the filler layer to form an anchor. In another case, after removal, the adhesion of the bridging layer 598 is sufficient to hold the device in place and act as an anchor. For illustrative purposes only, a sample in a substrate 510 is shown. Figure 5B The final device on the right side. One or a combination of the aforementioned devices can be used on the substrate.

[0140] like Figure 5CAs shown, the anchor may cover at least a portion of the perimeter of the device or the entire perimeter of the device, or it may be patterned to form arms 594 and 592. Any of the structures described can be used for any anchoring structure.

[0141] Figure 5D An example of transferring a device to the acceptor substrate 590 is shown. Here, the microdevice is bonded to pad 582 or placed in a predefined region without any pads. Pressure or separation force can release the anchor by breaking it. Alternatively, temperature can be used to release the anchor. The viscosity of the layer between the microdevice and the donor substrate 510 can be increased by controlling the temperature to act as an anchor. Figure 5E The device is shown after it has been transferred to the acceptor substrate 590, and a possible release point 598-2 in the anchor is shown. The anchor can also be connected directly or indirectly to the donor substrate 510 through other layers.

[0142] The device on the donor substrate 510 can be fabricated to have two contacts 532 and 480 on the same side opposite to the donor substrate 510. In one case, the device can be transferred directly from the donor substrate 510 to the recipient substrate 590. Here, contacts 532 and 480 can be directly bonded to the recipient substrate pads 582. The device can be tested in the donor substrate 510 or in a cassette. In another embodiment, the device can be transferred from the donor substrate 510 to a cassette substrate before being transferred to the recipient substrate 590. Here, 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 contacts 532 to appropriate connections in the recipient substrate 590.

[0143] 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 system 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.

[0144] Figure 6A Showing Figures 3A to 3FAn alternative embodiment of the mesa structure is provided, wherein the mesa structure is initially not etched through all layers. 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 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. 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 via one or more substrate bonding layers 378. The one or more bonding layers 378 may provide one or more different forces, such as electrostatic forces, chemical forces, physical forces, thermal forces, etc. After removing the device 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. Figure 6C Other layers, such as contact bonding layer 380, can be deposited and patterned. Here, 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 filler layer 374 and prepare it for transfer to acceptor substrate 390. This separation can be performed selectively, as described above. In another embodiment, filler layer 374 can be etched to form, for example, a truncated cone or frustoconical shape, at least partially surrounding each microdevice's housing, base, or anchor 375, such as... Figure 6E As shown. Another layer can be deposited over the base 375 and can be used to form the anchor 598-2. After forming the additional layer 598-2, the filler base layer 375 can be left or removed from the anchoring device. Figure 6G An apparatus with a sacrificial layer 372-2 is shown. The sacrificial layer 372-2 can be removed by etching or by thermal deformation or thermal removal.

[0145] In another embodiment, the anchor is the same as that of housing 375 and is constructed of polymeric, organic, or other layers after the microdevice is transferred to cartridge 376. Housing 375 can have different shapes. In one case, the housing can 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 the post-processing of different microdevices in cartridge 376 and the packaging of the microdevice cartridge for transport and storage. The housing sidewalls can be separated, or the connection from the device to the microdevice can be weakened from the device by different methods such as heating, etching, or exposure before or during the transfer cycle.

[0146] The device on donor substrate 310 can be fabricated to have two contacts 332 and 380 on the same side opposite to donor substrate 310. In this case, the conductive layer on cartridge 376 can be patterned to independently bias the two contacts 332 and 380 of the device. In one case, the device can be transferred directly from cartridge substrate 376 to acceptor substrate 390. Here, contacts 332 and 380 will not be directly bonded to acceptor substrate 390, i.e., acceptor substrate 390 does not need to have special pads. In this case, the conductive layer is deposited and patterned to connect contacts 332 and 380 to appropriate connections in acceptor substrate 390. In another embodiment, the device can be transferred from cartridge 376 to a temporary substrate before being transferred to acceptor substrate 390. Therefore, contacts 332 and 380 can be directly bonded to acceptor substrate pads. The device can be tested in cartridge 376 or in a temporary substrate.

[0147] 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 with 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, as thick as the donor substrate 6110. The buffer layers 6114 / 6118 can also be separated during the separation (lifting) of the microdevice from the donor substrate 6110. Therefore, the buffer layer deposition should be repeated each time. Figure 6HA structure on substrate 6110 is shown, wherein a separation layer 6116 is situated between a 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 are unresponsive to other layers. 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 a chemical substance that does not affect other layers. This chemical substance 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. Some surface treatment, such as cleaning or buffering, can be performed before the next device deposition. In another example, one or more buffer layers 6114 / 6118 may comprise zinc oxide.

[0148] Before the separation process (lifting), microdevices can be separated using different etching processes, such as... Figure 6I As shown. 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. Figure 6J As shown, the first buffer layer 6114 can remain substantially intact on the donor substrate 6110.

[0149] exist Figure 6K to 6M In another embodiment shown, 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 A top view shows an island 6212 formed in an array of microdevices. The size of the island 6212 can be the same as or a multiple of the box size. The island 6212 can be formed starting from or after the buffer layers 6114 / 6118. Here, surface treatment or gaps 6262, 6263 can be formed on the surface to initiate thin film growth into islands. Figure 6LTo handle microdevices, the gaps can be filled with a filler layer 6220, such as... Figure 6M As shown in the diagram. The filler 6220 may consist of a polymer layer, a metal layer, or a dielectric layer. The filler layer 6220 can be removed after processing the microdevice.

[0150] Figure 7 The process for creating the microdevice cassette is emphasized. During a 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 it. During a 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 a 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 via a bonding layer, such as 378 or 478. The microdevice is then separated from the microdevice cassette substrate 376 or 476. In another embodiment, the cassette is formed on a microdevice donor substrate, such as 510. After the device is secured to the cassette substrate 376, 476, or 510, other processing steps may be performed, such as removing layers, such as 312, 374, 472, or 574; or adding electrical layers (e.g., contacts 380 or 480) or optical layers (lenses, reflectors, etc.). During the fourth step 708, the cassette 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 cassette substrate, such as 376 or 476, or after the microdevice has been transferred to a recipient substrate, such as 390, 490, or 590, a testing step 707A may be performed on the microdevice to determine if it is defective. Defective microdevices may be removed or repaired in situ in step 707B. 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.

[0151] Figure 8The steps for transferring a device from cartridges 376, 476, or 510 to receiver substrates 390, 490, or 590 are illustrated. Here, during a 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 a 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 a third step, the microdevice is transferred to a selected landing area. During step 808, if the acceptor substrate 390, 490, or 590 is completely filled, in step 810, the cassette substrate 376, 476, or 510 is moved to a next step, such as another acceptor substrate 390, 490, or 590. If the current acceptor 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 step 802. If the cassettes 376, 476, or 510 have sufficient space in step 812, in step 814, the cassettes 376, 476, or 510 are offset (or moved and aligned) to a new area of ​​the acceptor substrate 390, 490, or 590, and a new cycle continues to step 806. Some of these steps may be combined and / or rearranged.

[0152] Figure 9The steps for 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, are illustrated. Here, during a first step 902, cassette 376 or 476 is loaded (or picked up), or in another embodiment, a spare device arm is pre-loaded with the cassette. During a second step 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 a 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 the microdevices and landing areas on recipient substrates 390, 490, or 590. Then, during a third step 906, the microdevice can be transferred to the selected landing area. In an optional step 906-1, the selected microdevice in the cassette can be attached to the recipient substrate. In optional step 906-2, the microdevice can be switched on, for example, by biasing through the acceptor substrate 390, 490, or 590, to test the connection between the microdevice and the acceptor substrate. If individual microdevices are found to be defective or nonfunctional, additional adjustment step 906-3 can be performed to correct or repair some or all of the nonfunctional microdevices.

[0153] If the acceptor substrate is completely filled, acceptor substrates 390, 490, or 590 move to the next step. If acceptor substrates 390, 490, or 590 require further filling, additional transfer steps are performed from one or more additional cassettes 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 cassettes 376, 476, or 510 have sufficient space, in steps 902-2, cassettes 376, 476, or 510 are offset (or moved and aligned) to a new area of ​​acceptor substrates 390, 490, or 590.

[0154] Figure 10Exemplary processing steps for producing multiple types of microdevice cassettes 376, 476, 510, or 1108 are demonstrated. 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 devices are formed, and post-processing is performed on them. During a second step 1004, the devices are prepared for separation from the donor substrate, such as 310 or 510. This step may involve securing the microdevices 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 can have different heights. For example, a second type of microdevice transferred to cartridges 376, 476, 510, or 1108 can 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 can be slightly higher). Here, after cartridges 376, 476, 510, or 1108 are fully filled, the height of the microdevice can be adjusted to flatten the surface of cartridges 376, 476, 510, or 1108. This can be done by adding material to shorter microdevices or removing material from taller ones. In another scenario, the landing area on the acceptor substrates 390, 490, or 590 may have different heights 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. A pick-and-place process can be used to move microdevices into 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 can be moved into cassettes 376, 476, 510, or 1108 in other ways. In another embodiment, additional devices are moved away from the cassette substrates 376, 476, 510, or 1108 of the first or second (or third or other) microdevices, and other types of microdevices are transferred to empty areas on cassettes 376, 476, 510, or 1108.After the device is secured to the cartridge substrate 376, 476, 510, or 1108, further processing steps may be performed, such as adding a filler layer 374, 474, or 574; removing some layers; or adding an electrical layer (e.g., contacts 380, 480, or 580) or an optical layer (lens, reflector). The device may be tested before or after it is used to fill the acceptor substrate 390, 490, or 590. The tests may be electrical tests, optical tests, or a combination of both. The tests may identify defects and / or performance issues of the device on the cartridge. During the final step 1010, the cartridge 376, 476, 510, or 1108 is moved to the acceptor substrate 390, 490, or 590 to transfer the device to the acceptor substrate 390, 490, or 590. Some of these steps may be rearranged or combined.

[0155] The transfer process described herein (e.g.) Figure 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 before alignment or may be part of an alignment step. This step may increase the number of microdevices aligned with landing areas (or pads) on acceptor substrates 390, 490, or 590. Furthermore, the 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 acceptor substrates 390, 490, or 590.

[0156] Figure 11 An example of a multi-type microdevice box 1108 similar to temporary substrates 376, 476, or 510 is shown. Box 1108 contains three different types of microdevices, such as those of colors (red, green, and blue), 1102, 1104, and 1106. However, more device types can exist. The distances x1, x2, and x3 between the microdevices are related to the spacing of the landing areas in the acceptor substrates 390, 490, or 590. Different spacings x4 and x2 can exist after several devices that may be related to the pixel spacing in the acceptor 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 box 1108, the force elements can be in the form of columns corresponding to each microdevice type, or the force elements can be separate elements for each microdevice.

[0157] Figure 12An example of a multi-type microdevice cassette 1208, similar to temporary substrates 376, 476, or 510, is shown. Cassette 1208 contains three different types of microdevices, such as those of different colors (red, green, and blue), 1202, 1204, and 1206. Other regions 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 regions in the acceptor 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 acceptor substrates 390, 490, or 590. This spacing compensates for the mismatch between the pixel spacing and the microdevice spacing (landing region spacing).

[0158] Figure 13 An example of a microdevice 1302 fabricated on a donor substrate 1304, similar to donor substrate 310 or 510, prior to transfer to multi-type microdevice cassettes 376, 476, 510, 1108, 1208, is shown. Here, support layers 1306 and 1308 can be used for individual devices 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.

[0159] 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 and second box structures.

[0160] Figure 14A An embodiment of a microdevice in a donor substrate 1480, similar to donor substrates 310 or 510, is shown. Due to manufacturing and material defects, the output power of the microdevice on donor substrate 1480 may gradually decrease or increase, exhibiting non-uniformity, as shown by the dark-to-light coloring. Adjacent devices in recipient substrates 390, 490, or 590 gradually degrade because devices can be transferred together to a block, such as block 1482, or sequentially, one or more at a time, to acceptor substrates 390, 490, or 590. However, worse problems 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, for example, along intersection line 1484. This can lead to abrupt changes in output performance, such as… Figure 14B As shown. This sudden change can cause visual illusions in optoelectronic devices such as displays.

[0161] To solve the problem of unevenness, Figure 14COne embodiment shown involves using blocks above and below individual blocks 1482 and 1483 on the display to skew or intersect these individual blocks, such that the edges or intersections of the blocks are not sharp lines, thereby eliminating intersection 1484, and thus 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.

[0162] Figure 14D Another embodiment is shown 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 in 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 can keep the changes and transitions between blocks very smooth and eliminate long, sharp intersections 1484.

[0163] Figure 14E Exemplary combinations of flipping devices are shown, 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, device performance alternates between high and low in two directions, i.e., in adjacent horizontal blocks and adjacent vertical blocks.

[0164] In one case, the performance of the microdevices at the edge of the adjacent transferred blocks (arrays) is matched for the recipient substrates 390, 490, or 590 before transfer.

[0165] Figure 15A This demonstrates the use of two or more blocks 1580, 1582 to fill blocks in the acceptor substrate 1590. In the illustrated embodiment, skew or flipping methods can be used to further improve average uniformity, such as… Figure 15B As shown. 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 connections above and below the blocks. Furthermore, a cell or acceptor substrate 1590 having more than one block can be filled with random or defined patterns.

[0166] Figure 16A Samples with more than one block 1680, 1682, and 1684 are shown. 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 Examples are shown where box 1690 is filled with different blocks 1680, 1682 and 1684 to eliminate the non-uniformity found in any block.

[0167] Figure 17A and 17BA structure with multiple cassettes 1790 is shown. As described above, the positions of the cassettes 1790 are selected in such a way that overlap between the same region of the acceptor substrates 390, 490, 590, or 1590 and the cassette 1790 having the same microdevices is eliminated during different transfer cycles. In one instance, the cassettes 1790 can be independent, meaning that a separate arm or controller handles each cassette independently. In another embodiment, the alignment can be performed independently, but other operations can be performed simultaneously. In this embodiment, the acceptor substrates 390, 490, 590, or 1590 can be moved to facilitate transfer after alignment. In another instance, the cassettes 1790 move together to facilitate transfer after alignment. In yet another instance, both the cassette 1790 and the acceptor substrates 390, 490, 590, or 1590 can be moved to facilitate transfer. In yet another case, the cassettes 1790 can be assembled in advance. In this case, a frame or substrate can hold the assembled cassettes 1790.

[0168] The distances X3 and Y3 between boxes 1790 can be multiples of the widths X1 and X2 or the lengths Y1 and Y2 of boxes 1790. These distances can be functions of movement step sizes in different directions. For example, X3 = KX1 + HX2, where K is the leftward (direct or indirect) movement step size for filling the acceptor substrates 390, 490, 590, or 1590, and H is the rightward (direct or indirect) movement step size for filling the acceptor substrates. The same logic applies to the distance Y3 between boxes 1790 and the lengths Y1 and Y2. Figure 17A As shown, box 1790 can be aligned in one or both directions. (As...) Figure 17B As shown, in another example, the cassette 1790 is not aligned in at least one direction. Each cassette 1790 may have independent controls for applying pressure and temperature to the acceptor substrates 390, 490, 590, or 1590. Other arrangements are also possible depending on the direction of movement between the acceptor substrates 390, 490, 590, or 1590 and the cassette 1790.

[0169] In another example, the cartridge 1790 may have different devices and thus fill different regions of the acceptor substrates 390, 490, 590, or 1590 with different devices. In this case, the relative positions of the cartridge 1790 and the acceptor 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.

[0170] In another embodiment, a plurality of box arrays 1790 are fabricated. Here, after a device is transferred from a first box array to a receiver substrate 390, 490, 590 or 1590, the receiver substrate 390, 490, 590 or 1590 moves to the next microdevice array to fill the remaining area in the receiver substrate 390, 490, 590 or 1590 or to receive different devices.

[0171] In another example, the housing 1790 may be on a curved surface, and thus circumferential movement will provide contact points to transfer the microdevice into the acceptor substrate 390, 490, 590, or 1590.

[0172] 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 separation 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 separation layer while the buffer layer remains on the substrate.

[0173] In one embodiment, the process of altering the properties of the one or more separation layers includes chemical etching or deforming the separation layers.

[0174] In another embodiment, the process of altering the properties of the one or more separation layers includes exposure to photoelectron waves, thereby deforming the separation layers.

[0175] 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.

[0176] In one embodiment, reusing the buffer layer to create a new optoelectronic stack layer includes surface treatment.

[0177] In one embodiment, the surface treatment uses chemical or physical etching or polishing.

[0178] In another embodiment, the surface treatment uses the deposition of an additional thin layer or buffer layer to reform the surface.

[0179] In one embodiment, the optoelectronic device is an LED.

[0180] In one embodiment, the separation layer is zinc oxide.

[0181] Embodiments of the present invention include a continuous pixelated structure comprising a fully or partially continuous active layer, a pixelated contact layer, and / or a current distribution layer.

[0182] 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.

[0183] In the above embodiments, a dielectric opening may be present on top of each pixelated contact layer and / or current distribution layer.

[0184] Another embodiment includes an donor substrate comprising a microdevice having bonding pads and a filler layer filling the space between the microdevices.

[0185] Another embodiment includes a temporary substrate comprising a bonding layer to which a microdevice from the donor substrate is bonded.

[0186] Another embodiment includes a heat transfer technology comprising the following steps:

[0187] 1) Align the microdevices on the temporary substrate with the bonding pads on the system substrate;

[0188] 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;

[0189] 3) Generate a thermal profile that melts both the bonding pads and the bonding layer, and thereafter keeps the bonding layer molten and the bonding pads solidified; and

[0190] 4) Separate the temporary substrate from the system substrate.

[0191] In another embodiment of the transfer technology, the thermal profile is generated by a local or global heat source or both.

[0192] Another embodiment includes a microdevice structure in which, after the microdevice is released from the donor substrate by a lift-off process, at least one anchor holds the device to the donor substrate.

[0193] Another embodiment includes a transfer technique for microdevice structures, wherein the anchor releases the microdevice after or during bonding the microdevice to a pad in a recipient substrate by pushing or pulling.

[0194] In another embodiment, the anchor according to the microdevice structure consists of at least one layer extending from the side of the microdevice to the substrate.

[0195] In another embodiment, the anchor according to the microdevice structure consists of at least one layer consisting of a void or the top of the void.

[0196] In another embodiment, the anchors according to the microdevice structure consist of a filler layer surrounding the device.

[0197] Another embodiment includes a structure based on a microdevice structure, wherein the viscosity of a layer separating the microdevice from the donor substrate is increased by controlling the temperature to act as an anchor.

[0198] Another embodiment includes a release process for anchors in a microdevice structure, wherein the temperature is adjusted to reduce the force between the anchor and the microdevice.

[0199] Another embodiment includes a process of transferring a microdevice into 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.

[0200] Another embodiment includes a process of transferring a microdevice into a receptor substrate, wherein the microdevice is formed in a cassette; selecting a set of microdevices with defective microdevices less than a threshold; aligning the selected set 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.

[0201] The embodiments include a cartridge having various types of microdevices transferred therein.

[0202] The embodiments include a microdevice housing, wherein a sacrificial layer separates at least one side of the microdevice from a filler layer or a bonding layer.

[0203] In the embodiments, the sacrificial layer is removed to release the microdevice from the filler layer or bonding layer.

[0204] In the embodiments, the sacrificial layer releases the microdevice from the packing material under certain conditions such as high temperature.

[0205] Microdevices can be tested to extract information related to them, including but not limited to defects, uniformity, and operational status. 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 microdevice is positioned in the cassette. This electrode can be used to test the microdevice before or after patterning. In one embodiment, the cassette is placed in a predefined location (which may be a holder). The cassette and / or acceptor substrate are 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 in the same acceptor substrate or a new 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 a predefined location. In one instance, the transfer of selected devices is controlled based on information extracted from the cassette. In one instance, 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 where the number of defects exceeds a threshold, or if the cumulative number of transferred defects exceeds a threshold. In another instance, the cells will be binned based on one or more extracted parameters, and each bin will be 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.

[0206] In embodiments, devices can be transferred from a cassette to a recipient substrate using physical contact and pressure and / or temperature. 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 cassette. 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 embodiments, the cassette does not contain 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 embodiments, the assigned location of the microdevice on the substrate may have been wetted with adhesive or covered with a bonding alloy, or additional structures may have been placed at the assigned location. During stamping, separate cassettes, printing, or other processes can be used. In embodiments, selected microdevices on the cassette can be moved closer to the recipient substrate to enhance selective transfer. In another case, a pull force is applied to the recipient substrate to assist or initiate the transfer of the microdevice from the cassette. The pull force can be combined with other forces.

[0207] In one embodiment, a 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 the microdevice is then 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, particularly in cases where multiple different devices are integrated into a 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. The second microdevice is then embedded in the associated layer. In all cases, this layer may cover part or all of the devices in the microdevice. In another embodiment, the housing is constructed from polymer layers, organic layers, or other layers after the microdevice is transferred to the cartridge. The housing may have different shapes. In one embodiment, 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 can be attached to the microdevices prior to the transfer cycle to support post-processing of the various microdevices within the cassette and for packaging the microdevices for transport and storage. The housing sidewalls can be separated, 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 microdevices to the cassette substrate. These contact points to the cassette can be on the bottom or top side of the device. These 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 cassette. The contacts can also be conductive to enable testing of the microdevices by biasing the device at the contact points and other electrodes connected to the microdevices. During the transfer cycle, the cassette can be positioned below the acceptor substrate to prevent the microdevices from falling off the housing if the contact points are globally removed or weakened.

[0208] In one embodiment, the microdevice cassette may include at least one anchor that holds the microdevice to the cassette surface. The cassette and / or the receiver substrate are moved such that some of the microdevices in the cassette are aligned with some of the microdevices in the receiver substrate. This anchor may break under pressure during the pushing of the cassette and the receiver substrate toward each other or during the pulling of the device through the receiver substrate. The microdevice may remain permanently attached to the receiver substrate. The anchor may be located on the side of the microdevice or on top (or bottom) of the microdevice.

[0209] 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 referred to as the sides or sidewalls.

[0210] 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. The cassette can be placed in a predefined location (which may be a holder). The cassette and / or acceptor substrate can be moved for alignment. At least one selected device can be transferred to the acceptor substrate. If more microdevices become available on / in the cassette, the cassette or acceptor substrate can be moved to align with a new region within the same acceptor substrate or a new acceptor substrate, and at least another selected device can be transferred to a new location. This process can continue until the cassette no longer has enough microdevices, at which point a new cassette will be placed in a predefined 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 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 the cumulative number of transferred defects exceeding a threshold. In another case, the cassette is compartmentalized based on one or more extracted parameters, and each compartment can be used for a different application. 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.

[0211] One embodiment includes a method of transferring a device onto a receptor substrate. The method comprises:

[0212] a) Fabricating a cassette having a substrate, wherein microdevices are positioned on at least one surface of the cassette substrate, and the substrate has additional microdevices in regions other than those of the same size as the microdevices in the recipient substrate.

[0213] b) By extracting at least one parameter from the device on the test box.

[0214] c) Pick up the cassette or transfer the cassette to a location with the microdevice facing the receptor substrate.

[0215] d) Use the test data to select a set of microdevices on the box.

[0216] e) Align the selected set of microdevices on the cassette with the selected location on the receptor substrate. Transfer the set of microdevices from the cassette to the receptor substrate.

[0217] f) Processes d and e can continue until the box is completely filled without any useful devices or acceptor substrate.

[0218] 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.

[0219] 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 row or column such that the edge of at least one row or column is not aligned with the edge of at least another row or column.

[0220] One embodiment is a method for transferring devices to a recipient substrate. The method includes transferring an array of microdevices into the substrate, wherein the edges of at least one row or column of transferred microdevices are not aligned with the edges of at least another row or column of transferred devices.

[0221] One embodiment includes a method for transferring devices to a recipient substrate. The method comprises 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 row or column of microdevices having two distinct regions from the donor substrate corresponding to the transferred array.

[0222] One embodiment includes a process of transferring an array of microdevices into a receptor substrate, wherein the microdevices are deflected at the edges of the array to eliminate abrupt changes.

[0223] Another embodiment includes a process for 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.

[0224] Another embodiment includes a process for transferring a microdevice array into a acceptor substrate, wherein the microdevice array is filled from at least two different regions of the microdevice donor substrate.

[0225] Another embodiment includes a process of transferring an array of microdevices from a cassette to a receptor substrate, wherein a plurality of microdevice cassettes are placed in different locations corresponding to different regions of the receptor substrate, the cassettes are then aligned with the receptor substrate, and the microdevices are transferred from the cassettes to the receptor substrate.

[0226] Different anchoring schemes for securing microdevices to donor substrates

[0227] 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 acceptor 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 system substrates to assist in forming a strong bond. Curing agents include one of the following: polyamides, SU8, PMMA, BCB thin films, 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 exceed the current / voltage requirements that the microdevices can withstand.

[0228] To avoid damaging microdevices, structures and methods are needed to integrate them into system substrates with enhanced bonding and conductivity. Furthermore, alternative current / voltage paths can be formed to prevent damage to the microdevices.

[0229] 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.

[0230] In one case, temporary material acts as an anchor, holding the plurality of microdevices within a housing structure in the donor substrate.

[0231] In another case, all or part 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.

[0232] In one scenario, the microdevice may have one conductive pad on each side of the microdevice. In another scenario, the microdevice may have more than one conductive pad on one side.

[0233] Figure 18 A donor substrate 1802, which holds multiple microdevices via a donor force element according to an embodiment of the invention, is shown. The donor substrate 1802 may be a growth substrate (where microdevices are fabricated or grown) to which it has been transferred or another temporary substrate. Reference is made to gallium nitride (GaN)-based LEDs described below; however, the structure described herein can be used with any type of LED having different material systems.

[0234] In general, GaN-based microLEDs are fabricated by stacking materials deposited on a sapphire substrate. Conventional GaNLED devices include a substrate such as sapphire, an n-type GaN layer formed on the substrate, or a buffer layer (e.g., GaN), and an active layer / semiconductor layer, such as a multiple quantum well (MQW) layer and a p-type GaN layer.

[0235] like Figure 18As shown, 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 to be transferred 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), 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 dielectric having a high-resistivity trace that generates heat under an applicable current / voltage, and the generated heat causes the dielectric to locally cure.

[0236] The donor substrate 1802 has at least one donor force element 1804. The donor force element 1804 is a 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 by a selected means of 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.

[0237] Figure 19 A microdevice with more than one conductive pad on one side is shown according to an embodiment of the 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 pad 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 a selected acceptor force element (e.g., 1918), thereby causing it to harden and hold the microdevice in place.

[0238] Voltage / current 1910, 1912 can be applied to a selected receiving force element (e.g., 1918) to cure it, thereby hardening it and holding the microdevice in place.

[0239] 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 either the donor substrate 1902 or the acceptor substrate 1908.

[0240] However, the current / voltage requirements of the solidified force-bearing element may exceed the current / voltage requirements that the microdevice can withstand. To avoid damaging the microdevice, an alternative current / voltage path can be formed. In another case, part or all of the microdevice may be covered with a temporary conductive material, which redirects current through the temporary conductive material rather than the microdevice, thus preventing damage to the microdevice.

[0241] Figures 20A-20I illustrate examples of microdevices partially / completely covered by temporary conductive material according to some embodiments of the present invention.

[0242] The microdevice may be partially or entirely 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. The conductive material may be connected as a sheet or trace to the same or a different conductive material on the donor substrate.

[0243] In one embodiment, the microdevice may be located within 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.

[0244] 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 walls are shorter than the microdevice. The housing may also be taller than the microdevice.

[0245] In another case, the temporary conductive material can be replaced by a non-conductive material.

[0246] In cases involving both conductive and non-conductive temporary materials, 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.

[0247] Microdevices may be covered with a temporary material / layer before transfer to the recipient substrate, or they may be covered after transfer to the recipient substrate. In one case, a housing material is coated on the substrate between the microdevices. It may be bonded to the donor substrate, and then the housing material may cure. In another case, different materials may be present on the surface of the donor substrate that can be electrically coupled to the microdevices or temporary layers. In yet another case, the housing material is coated on top of the donor substrate. The microdevices are then bonded and pushed into the material, and then the material cures. The housing material may be epoxy, polymer, or other types of materials. In one case, BCB or polyamide may be used as the housing material.

[0248] Temporary material can be patterned to form an opening on top of the donor substrate. This opening can facilitate a process, such as removing the sacrificial layer, to separate the microdevice from the housing sidewalls.

[0249] Figures 20A1-20A2 Examples of highlighting temporary conductive material covering the surface of a microdevice are shown according to some embodiments of the present invention.

[0250] See Figure 20A1 Here, 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 along the length of the microdevice. The bond 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. An anchor 2014a may hold the microdevice in the donor substrate. The anchor 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.

[0251] In another embodiment, the housing wall may extend almost to the edge of the microdevice.

[0252] Figure 20A2 A cross-sectional view of a microdevice on a device (donor) substrate according to an embodiment of the invention is shown, 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 layers of the donor substrate or between donor substrates may couple the conductive material to a current / voltage source.

[0253] Figure 20B1A cross-sectional view of a microdevice on a device (donor) substrate according to an embodiment of the invention is shown, 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 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 on the donor substrate or between donor substrates may couple the conductive material to the current / voltage source.

[0254] Figure 20B2 A cross-sectional view of a microdevice on a device (donor) substrate according to an embodiment of the invention is shown, 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.

[0255] Figure 20C1 An example of temporary conductive material forming a current / voltage path between conductive pads 2004c and 2006c is shown, wherein the conductive pads may be on the top and bottom or the same side of the microdevice. Here, the 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.

[0256] Figure 20C2 An example is shown 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, which 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.

[0257] Figure 20D Another example of temporary conductive material 2002d forming a current / voltage path between conductive pads 2004d and 2006d of a microdevice is shown, where 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 the temporary material is deposited on the patterned conductive pads.

[0258] Figure 20EAnother example is shown, 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. Furthermore, 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.

[0259] Figure 20F Examples of conductive pads 2008f and 2010f on surfaces not shorted together by conductive layer 2002f are shown. Here, the pads may be completely or partially covered by conductive layer 2002f, as shown. Furthermore, there is no bonding material between the donor substrate and the microdevice. A temporary conductive material serves as the bonding material for the microdevice.

[0260] Figure 20G Another example is shown, in which temporary conductive material 2002g forms current / voltage paths for more than one pad on the surface of the microdevice. Here, the conductive material forms a pathway 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.

[0261] Figure 20H Examples are shown 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 remote from the donor substrate to the conductive layer at the donor substrate. In another case, it indirectly couples a surface remote from the donor substrate to conductive layer 2006h at the donor substrate.

[0262] Figure 20I1 and Figure 20I2 An example is shown 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, 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.

[0263] Figures 21A-21DA top view of various microdevices constructed from temporary materials (conductive or non-conductive) according to embodiments of the invention is shown. The temporary material may be patterned to form an opening on top of a donor substrate. This opening facilitates a process, such as removing a sacrificial layer, to separate the microdevice from the housing sidewalls. This process may be performed before or after the microdevice is transferred to a 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 the bonding process, it does not need to connect (or cover) the pads on the microdevice.

[0264] Figure 21A An exemplary top view of FIG20A is shown 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 the conductive material on the top of the donor substrate may be connected as a mesh, row, or column. Access points may be present on the top of the donor substrate to bias the temporary layer via the traces.

[0265] Figure 21B1 An exemplary top view representation of Figure 20B is shown. Here, traces on the top of the donor substrate may be connected as a mesh, row, or column. Access points may be present on the top of the donor substrate to bias the temporary layer via the 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 a mesh, row, or column. Access points may be present on the top of the donor substrate to bias the temporary layer via the traces.

[0266] Figure 21B2 An example is shown 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 traces of the temporary conductive material on the top of the donor substrate can be connected as a mesh, row, or column. This can be used in other embodiments or related structures in this disclosure.

[0267] Figure 21C Show Figure 20E An exemplary top view shows that 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 can be connected as a mesh, row, or column. Furthermore, the traces for 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.

[0268] Figure 21D Show Figure 20F An exemplary top view shows that 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, row, or column. Furthermore, the traces for 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.

[0269] Microdevices released from donor substrate via breakable anchors

[0270] Some embodiments of this disclosure illustrate that microdevices may have different temporary anchors, whereby, after removal of the device, 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 approaches 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 pulling the microdevice through 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.

[0271] Figures 22A-22C A microdevice on a donor substrate is shown according to an embodiment of the invention, wherein the microdevice is selectively movable toward or away from the surface of the donor substrate.

[0272] See Figure 22A According to one embodiment, the stack includes electrodes 2204, 2206 and an electroactive polymer (EPE) layer 2208 formed beneath the microdevices (e.g., 2210, 2212 on top of donor substrate 2214). Movement of the donor and / or acceptor substrates 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 it to thin and thus bringing the devices closer to the surface of the acceptor substrate.

[0273] See Figure 22BAccording 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 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.

[0274] Figure 22C Another example is shown, 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 attached to the microdevice prior to transfer cycles to support different post-processing of the microdevice.

[0275] 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. The thrust releases the anchor 2234, and the microdevice can be placed on the surface of the recipient substrate.

[0276] Figures 23A-23B Another embodiment of a microdevice on a donor substrate is shown, wherein the microdevice is selectively movable toward or away from the surface of the donor substrate.

[0277] exist Figure 23A In another embodiment, stacks of different materials 2304, 2308, and 2310 with different coefficients of thermal expansion are formed on top of the donor substrate 2320, below 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.

[0278] Figure 23BAnother example is shown, in which microdevices 2312, 2314, 2318 structures on top of stacked layers 2304, 2308, 2310 are surrounded by a housing 2322. Furthermore, anchors 2332, 2326 hold 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, stack 2308 pushes microdevice 2314 forward. This thrust releases anchors 2326, allowing microdevice 2314 to be placed on the surface of the recipient substrate.

[0279] Figure 24 Another example of a microdevice on a donor substrate is shown according to an embodiment of the invention, wherein the microdevice is selectively movable toward or away from the surface of the donor substrate.

[0280] Here, the microdevices 2410, 2414, and 2418 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 acceptor 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 acceptor 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.

[0281] Microdevice box structure

[0282] 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.

[0283] 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 to corresponding pads on the backplane; and leaving the bonded set of selective microdevices on the backplane by separating the microdevice substrate.

[0284] In one embodiment, an array of microdevices can be formed on a microdevice substrate, wherein the microdevices can be formed by etching one or more planar layers.

[0285] In another embodiment, one or more planarization layers may be formed on the microdevice substrate and cured by temperature, light or other sources.

[0286] 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.

[0287] In another embodiment, the microdevice substrate can be removed by laser or chemical removal.

[0288] In one embodiment, the buffer layer may contain openings for connecting microdevices to the planarization layer. In another case, electrodes may be disposed on the top or bottom of the planarization layer.

[0289] 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.

[0290] In one scenario, multiple pads can be added to the microdevice. These pads can be conductive or purely for bonding to the system substrate. In another scenario, a buffer layer can connect at least one microdevice to a test pad. The test pad can be used to bias the microdevice and test its functionality. Testing can be performed at the wafer level or the intermediate (cassette) level. Pads are accessible at the intermediate level after removing too many layers.

[0291] 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.

[0292] In one embodiment, a backplane may be provided. In one case, the backplane may have transistors and other components for driving microdevices via pixel circuitry. In another case, the backplane may be a substrate without components.

[0293] In one embodiment, one or more pads may be provided on the backplane for the bonding process. In another case, the pads on the backplane or on the microdevice may generate a pull-out force on the microdevice.

[0294] 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, such as a camera or probe tip, can be used to detect the position of the microdevice. 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, color filters or conversion layers can also be adjusted based on the position of the microdevice. In one case, some random offsets can be induced in the microdevice's position to reduce optical artifacts.

[0295] 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).

[0296] In one scenario, the position / shape of the electrodes can be modified based on the location of the microdevice. In another scenario, there may be some extensions of each electrode whose position or length can be modified based on the location of the microdevice.

[0297] Figure 25A A cross-sectional view of a microdevice array on a microdevice substrate according to an embodiment of the present invention is shown. 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.

[0298] 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. Microdevices can be fabricated 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 layers to leave some residue on the surface of the microdevice substrate. Other layers may be deposited and patterned before or after the formation of the microdevice.

[0299] Figure 25B A cross-sectional view of a microdevice array having a buffer layer according to an embodiment of the present invention is shown. Here, a buffer layer 2506 may be formed on a microdevice array 2504. The buffer layer 2506 may extend over the surface of a 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 an electrode that can be patterned or used as a common electrode.

[0300] Figure 25C A cross-sectional view of a microdevice array having a planarization layer according to an embodiment of the present invention is shown. 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 comprise 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.

[0301] Figure 25DA cross-sectional view of an array of microdevices bonded to an intermediate substrate according to an embodiment of the present invention is shown. 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 forces. The bonding layer 2512 may contact the planarization layer 2508. To form a contact between the planarization layer and the bonding layer, the bonding layer is cured by pressure, temperature, light, or other sources.

[0302] 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 removal.

[0303] 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 another embodiment, the buffer layer may be etched to form a housing, substrate, or anchor that at least partially surrounds each microdevice. After lift-off, the anchor can hold the microdevice to the substrate. In yet 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.

[0304] Figure 25E A cross-sectional view of a microdevice array with pads according to an embodiment of the present invention is shown. 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.

[0305] In one embodiment, buffer layer 2506 can connect one or more microdevices to test pads. The test pads can be used to bias the 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 (cassette) level. The pads are accessible at the intermediate level after removing too many layers.

[0306] 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.

[0307] Figure 26A cross-sectional view of an array of microdevices bonded to an intermediate substrate and a backplane according to an embodiment of the present invention is shown. Here, a backplane 2630 may be provided. In one case, the backplane may be fabricated using a TFT process. In another case, the backplane may be fabricated using a chiplet or other process fabricated with complementary metal-oxide-semiconductor (CMOS).

[0308] 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.

[0309] 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.

[0310] Figure 27A The process steps for extracting the location of a microdevice according to an embodiment of the present invention are illustrated. After the microdevice is transferred to a backplane, the location 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 location of the microdevice on the system substrate using a camera, surface profilometer (optical, ultrasonic, electrical), or other means; step 2706, possibly modifying the pattern with respect to 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 be present on the system substrate to first calibrate the tool used for extracting the microdevice location, or the reference may be used to find the relative position of the microdevice.

[0311] 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 microdevice's position on the system substrate / backplane.

[0312] For example, in one case, metallization patterning can prevent short circuits. In another, color filters or color conversions can be adjusted based on the location of the microdevice. This reduces the tolerance required for placing the microdevice. It can also induce a random offset in the microdevice's location to reduce optical artifacts.

[0313] Figure 27B This illustration shows the modification of electrode position / shape based on the position of a microdevice according to an 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 a planarization / passivation layer may be modified according to the position of the microdevices.

[0314] Figure 27C An extension to an electrode is shown according to an embodiment of the invention. In one case, the position of electrode 2702 can be modified. Furthermore, for each electrode, an extension 2720 may exist such that its position or length can be modified based on the position of microdevices 2710, 2712, or 2714. This can be used for common electrodes or individual electrodes.

[0315] 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 a 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 to the one or more conductive pads through the temporary material. 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.

[0316] 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 within the housing structure holding the plurality of microdevices in the donor substrate.

[0317] According to another embodiment, the method may further include at least one sacrificial layer between the housing structure and each microdevice, 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 microdevice from the sidewall of the housing structure by removing the sacrificial layer. After removing the sacrificial layer, the temporary material holds each microdevice in place, and the sacrificial layer is removed by using a chemical etching process or an electromagnetic signal.

[0318] According to other embodiments, the temporary material is separated from the housing structure after each microdevice is transferred to the recipient substrate via one of the following processes: mechanical, optical, thermal, and chemical processes. Conductive traces on the top surface of the donor substrate are connected as one of the following: mesh, row, or column.

[0319] 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.

[0320] According to one embodiment, a method is provided for bonding at least one microdevice to a acceptor substrate. The method includes: forming a stack including electrodes and an electroactive polymer layer on a donor substrate beneath the at least one microdevice; and applying a voltage to the stack to bring the at least one microdevice into contact / proximity range with respect to the surface of the acceptor substrate.

[0321] 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 within the housing structure.

[0322] According to another embodiment, the anchor releases a microdevice on the surface of the receptor substrate by either a thrust or a pull force, the stack further comprising an absorption layer that converts light into a thermally altered state, and an electroactive polymer layer that becomes a gas, and the pressure generated by the alteration pushes the at least one microdevice onto the surface of the receptor substrate.

[0323] According to one embodiment, a method for integrating microdevices on 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.

[0324] 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 extraction. The bonding layer may be cured by pressure, temperature, or photopolymerization.

[0325] According to another embodiment, the method may further include removing the microdevice substrate by one of laser or chemical removal, 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.

[0326] According to another embodiment, the method may further include providing openings in a buffer layer to allow microdevices to connect to a planarization layer. The buffer layer is conductive, wherein the buffer layer connects at least one microdevice to a test pad.

[0327] 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 location of the microdevice on a backplane; and extending the position of the electrode to extract the location of the microdevice on the backplane, wherein the location of the microdevice is extracted by a camera, probe tip, or surface profilometer.

[0328] In summary, this disclosure provides a microdevice integration process and electronic control integration that involves transferring components to a system substrate. This transfer can be facilitated by various means, including providing temporary materials, breakable anchors on a donor substrate, or temporary intermediate substrates.

[0329] 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. In view of the above teachings, many modifications and variations are possible. It is intended that the scope of the invention is not limited by this detailed description, but rather by the appended claims.

Claims

1. A bonding structure comprising: a plurality of micro devices on a donor substrate, each micro device comprising one or more electrically conductive pads formed on a surface of the micro device; and a temporary material to cover at least a portion of each micro device or the one or more electrically 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 electrically conductive pads, wherein a receiver substrate has at least one receiver force element for each selected micro device chosen to be transferred to the receiver substrate, the receiver force element being a current / voltage solidifiable component, the donor substrate having at least one donor force element, the at least one donor force element being an element that loses its adhesive property under current or voltage.

2. The bonding structure of claim 1, wherein the temporary material comprises an electrically conductive material or a non-conductive material.

3. The bonding structure of claim 1, further comprising: an electrically conductive layer at the donor substrate that couples the temporary material to the current / voltage source.

4. The bonding structure of claim 2, wherein the temporary material further completely or partially covers the one or more electrically conductive pads.

5. The bonding structure of claim 1, further comprising: a housing structure to cover at least a portion of each micro device on the donor substrate.

6. The bonding structure of claim 5, wherein the temporary material acts as an anchor to hold the plurality of micro devices inside the housing structure in the donor substrate.

7. The bonding structure of claim 5, further comprising: at least one sacrificial layer between the housing structure and each micro device.

8. The bonding structure of claim 7, wherein the temporary material is patterned to form an opening on a top surface of the donor substrate.

9. The bonding structure of claim 8, wherein the opening at the top surface of the donor substrate is used to release the micro device from a sidewall of the housing structure by removing the sacrificial layer.

10. The bonding structure of claim 9, wherein the temporary material holds each micro device in place after the sacrificial layer is removed, and wherein the sacrificial layer is removed by using a chemical etching process or an electromagnetic signal.

11. The bonding structure of claim 8, wherein the temporary material is separated from the housing structure after each micro device is transferred to a receiver substrate by one of the following processes: a mechanical process, an optical process, a thermal process, and a chemical process.

12. The bonding structure of claim 11, wherein electrically conductive traces on the top surface of the donor substrate are connected as one of the following: a mesh, a row, or a column.

13. The bonding structure of claim 12, wherein a plurality of access points on the top surface of the donor substrate are used to bias the temporary material via the electrically conductive traces.

14. The bonding structure of claim 1, wherein the temporary material forms a passage between a surface facing the donor substrate and a surface facing away from the donor substrate.

15. A method of integrating micro devices on a backplane, the method comprising: providing a micro device substrate comprising one or more micro devices; forming a buffer layer on or over the one or more micro devices extending above the substrate; forming a planarization layer on the buffer layer; depositing a bonding layer between the planarization layer and an intermediate substrate; removing the micro device substrate; bonding a select group of the micro devices to the backplane by connecting contact pads on the select group of the micro devices to corresponding pads on the backplane; leaving the bonded select group of the micro devices on the backplane by separating the bonded select group of the micro device substrate from the buffer layer.

16. The method of claim 15, wherein: the planarization layer comprises a polymer, and wherein the polymer comprises one of polyamide, SU8, or BCB.

17. The method of claim 16, further comprising curing the bonding layer after contacting the planarization layer, wherein the bonding layer is cured by any one of pressure, temperature, or light.

18. The method of claim 15, wherein the micro device substrate is removed by one of a laser or chemical lift-off.

19. The method of claim 15, wherein the pads on the micro devices and the corresponding pads on the backplane are electrically conductive.

20. The method of claim 15, wherein the contact pads on the select group of the micro devices or the corresponding pads on the backplane create a force that pulls the select group of the micro devices.

21. The method of claim 15, further comprising providing an opening in the buffer layer to allow the micro devices to connect to the planarization layer.

22. The method of claim 16, wherein the buffer layer is electrically conductive.

23. The method of claim 16, wherein the buffer layer connects at least one micro device to a test pad.

24. The method of claim 16, further comprising providing an electrode on either the top or bottom of the planarization layer; and coupling at least one micro device to the electrode via the buffer layer.

25. The method of claim 24, further comprising extracting the position of a micro device on the backplane; and extending the position of the electrode to extract the position of a micro device on the backplane, wherein the position of a micro device is extracted by one of a camera, a probe tip, or a surface profiler.

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