CN111816663A

CN111816663A - Method for manufacturing pixelized structure

Info

Publication number: CN111816663A
Application number: CN201910848702.8A
Authority: CN
Inventors: 格拉姆雷扎·查济; 埃桑诺拉·法蒂
Original assignee: Vuereal Inc
Current assignee: Vuereal Inc
Priority date: 2019-04-09
Filing date: 2019-09-09
Publication date: 2020-10-23

Abstract

A method of fabricating a pixelated structure may be provided. The method may include: providing a donor substrate comprising a plurality of pixelated microdevices; bonding a selective set of the pixelated micro-devices from the donor substrate to a system substrate; and patterning a bottom conductive layer of the pixelated micro-device after separating the donor substrate from the system substrate. The patterning may be performed by completely isolating the layers or leaving some thin layers between the patterns.

Description

Method for manufacturing pixelized structure

Cross Reference to Related Applications

This application is a continuation-in-part application and claims priority from U.S. application serial No. 15/820,683 filed on 22/11/2017, which claims priority and benefit from U.S. provisional patent application serial No. 62/426,353 filed on 25/11/2016, U.S. provisional patent application serial No. 62/473,671 filed on 20/3/2017, U.S. provisional patent application serial No. 62/482,899 filed on 7/4/2017, U.S. provisional patent application serial No. 62/525,185 filed on 5/6/2017, and canadian patent application No. 2,984,214 filed on 30/10/2017, each of which is incorporated herein by reference in its entirety. This application also claims priority from U.S. provisional patent application serial No. 62/831,403(7PL06), filed at 2019, month 4, 09, which is incorporated herein by reference in its entirety.

Technical Field

The present disclosure relates to optoelectronic solid state array devices, and more particularly to methods for improving the light output profile of solid state array devices.

Background

It is an object of the present invention to overcome the disadvantages of the prior art by providing a micro device array display device, wherein the micro device array can be bonded to a back plate by a reliable method.

Disclosure of Invention

According to one embodiment of the invention, a method for fabricating a pixelated structure comprises: 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 electrically conductive layer; depositing a second conductive layer on the functional layer; patterning the second conductive layer to form a pixelated structure; providing a bonding contact for each pixelated structure; securing the bonding contact to a system substrate; and removing the donor substrate.

In one embodiment, the micro devices are turned into an array by sequential pixelation.

In another embodiment, the devices are separated by filling the voids between the micro devices and transferred to an intermediate substrate.

In another embodiment, the micro device is post-processed after transfer to the intermediate substrate.

According to one embodiment, a method of fabricating a pixelated structure may be provided. The method may include: providing a donor substrate comprising a plurality of pixelated microdevices; bonding a selective set of the pixelated micro-devices from the donor substrate to a system substrate; and separating the donor substrate from the system substrate and then patterning the bottom planar layer of the pixelated microdevice.

According to one embodiment, a donor substrate having a plurality of micro devices with bond pads and a filler layer filling spaces between the micro devices may be provided.

According to another embodiment, the donor substrate may be removed from the lateral functional device.

According to one embodiment, one or more of the bottom layers may be patterned after separating the donor substrate (or the micro device substrate).

According to some embodiments, the patterning may be performed by completely isolating the layers or leaving some thin layers between the patterns.

According to other embodiments, a specific ohmic contact may be required to obtain a suitable connection to the patterned bottom conductive layer.

According to one embodiment, the ohmic contact may be one of an opaque material or a transparent material.

Drawings

The invention will be described in more detail with reference to the appended drawings showing preferred embodiments of the invention, in which:

FIG. 1A illustrates a cross-sectional view of a lateral functional structure on a donor substrate according to an embodiment of the present invention;

FIG. 1B illustrates a cross-sectional view of the lateral structure of FIG. 1A with a current distribution layer deposited thereon, in accordance with an embodiment of the present invention;

FIG. 1C shows a cross-sectional view of the lateral structure of FIG. 1B after patterning the top dielectric conductive layer and depositing a second dielectric layer, in accordance with an embodiment of the present invention;

FIG. 1D illustrates a cross-sectional view of a lateral structure after patterning a second dielectric layer, in accordance with an embodiment of the present invention;

FIG. 1E illustrates a cross-sectional view of a lateral structure after deposition and patterning of a pad, in accordance with an embodiment of the present invention;

FIG. 1F illustrates a cross-sectional view of a lateral structure after bonding to a system substrate via a bonding region to form an integrated structure, in accordance with an embodiment of the present invention;

FIG. 1G illustrates a cross-sectional view of the integrated structure after removal of the donor substrate and the patterned bottom electrode, in accordance with an embodiment of the present invention;

FIG. 1H illustrates a cross-sectional view of the integrated structure after removal of the donor substrate and the patterned bottom electrode, in accordance with an embodiment of the present invention;

FIG. 1I illustrates a cross-sectional view of an integrated structure having a patterned bottom electrode with an ohmic contact, according to an embodiment of the invention;

FIG. 1J-1 shows a cross-sectional view of an integrated structure with an ohmic contact inside an isolation pattern of a patterned bottom electrode, according to an embodiment of the invention;

1J-2 illustrate a cross-sectional view of an integrated structure with an ohmic contact at an edge of an isolation pattern of a patterned bottom electrode, in accordance with an embodiment of the present invention;

FIG. 1K shows a cross-sectional view of an integrated structure with a patterned bottom electrode covered with a common electrode, according to an embodiment of the invention;

FIG. 2A shows a cross-sectional view of another embodiment of a lateral functional structure on a donor substrate with a pad layer;

fig. 2B illustrates a cross-sectional view of the lateral structure of fig. 2A after patterning the pad layer and the contact layer and the current distribution layer, in accordance with an embodiment of the present invention;

FIG. 2C illustrates a cross-sectional view of the lateral structure of FIG. 2A after filling the distance between the patterned pads, in accordance with an embodiment of the present invention;

FIG. 2D illustrates a cross-sectional view of the lateral structure of FIG. 2A aligned and bonded to a system substrate by patterned bonding pads, in accordance with an embodiment of the present invention;

FIG. 2E illustrates a cross-sectional view of the lateral structure of FIG. 2A with the device substrate removed, in accordance with an embodiment of the present invention;

FIG. 3A shows a cross-sectional view of a mesa structure on a device (donor) substrate according to an embodiment of the present invention;

FIG. 3B illustrates a cross-sectional view of a step of filling empty spaces between the mesa structures of FIG. 3A, in accordance with an embodiment of the present invention;

FIG. 3C shows a cross-sectional view of the step of transferring the device (mesa structure) of FIG. 3B to a temporary substrate according to an embodiment of the present invention;

FIG. 3D illustrates a cross-sectional view of a step of aligning and bonding the device of FIG. 3C to a system substrate, in accordance with an embodiment of the present invention;

FIG. 3E shows a cross-sectional view of a step of transferring the device to a system substrate according to an embodiment of the invention;

FIG. 3F illustrates a thermal profile of a thermal transfer step according to an embodiment of the invention;

FIG. 4A shows a cross-sectional view of a temporary substrate having a slot and a device transferred thereto, in accordance with an embodiment of the present invention;

FIG. 4B shows a cross-sectional view of the temporary substrate of FIG. 4A after cleaning the filler material from between the device space and the trough, in accordance with an embodiment of the present invention;

FIG. 4C shows a cross-sectional view of a step of transferring a device to a system substrate by damaging the released surface, in accordance with an embodiment of the present invention;

FIG. 5A illustrates a cross-sectional view of a microdevice having different anchors according to an embodiment of the invention;

FIG. 5B illustrates a cross-sectional view of a microdevice after post-processing a fill layer according to an embodiment of the invention;

FIG. 5C illustrates a top view of the micro device of FIG. 5B, according to an embodiment of the invention;

FIG. 5D shows a cross-sectional view of a transfer step for transferring a micro device to another substrate, in accordance with an embodiment of the present invention;

FIG. 5E illustrates a cross-sectional view of a micro device transferred to a substrate, according to an embodiment of the invention;

figure 6A shows a cross-sectional view of a mesa structure on a device (donor) substrate in accordance with an embodiment of the present invention;

FIG. 6B shows a cross-sectional view of a step of filling empty spaces between the mesa structures of FIG. 6A;

FIG. 6C shows a cross-sectional view of the step of transferring the device (mesa structure) of FIG. 6B to a temporary substrate according to an embodiment of the present invention;

FIG. 6D shows a cross-sectional view of a step of removing a portion of the bottom conductive layer of FIG. 6C, according to an embodiment of the invention;

FIG. 6E illustrates a cross-sectional view of a microdevice having anchors in the fill layer according to an embodiment of the invention;

FIG. 6F illustrates a cross-sectional view of a microdevice having anchors in the fill layer according to an embodiment of the invention;

FIG. 6G illustrates a cross-sectional view of a microdevice having anchors in the fill layer according to an embodiment of the invention;

FIG. 6H illustrates a cross-sectional view of a preliminary step in another embodiment of the present invention;

FIG. 6I illustrates a cross-sectional view of an etching step in the embodiment of FIG. 6H, in accordance with an embodiment of the present invention;

FIG. 6J illustrates a cross-sectional view of a separation step in the embodiment of FIG. 6H, in accordance with an embodiment of the present invention;

FIG. 6K illustrates a top view of another embodiment of the present invention, according to an embodiment of the present invention;

FIG. 6L illustrates a cross-sectional view of the embodiment of FIG. 6K, in accordance with an embodiment of the present invention;

FIG. 6M illustrates a cross-sectional view of the embodiment of FIGS. 6K and 6L with a filler material, in accordance with an embodiment of the present invention;

FIG. 7 is a flow chart of a process according to an embodiment of the invention;

FIG. 8 is a flow chart of a microdevice installation process according to an embodiment of the invention;

FIG. 9 is a flow chart of a microdevice installation process according to an embodiment of the invention;

FIG. 10 is a flow chart of a microdevice installation process according to an embodiment of the invention;

FIG. 11 shows an example of a donor or temporary (box) substrate with different types of pixelated micro-devices, according to an embodiment of the invention;

FIG. 12 shows an example of a donor or temporary (box) substrate with different types of pixelated micro-devices, according to an embodiment of the invention;

FIG. 13 shows an example of a donor substrate for the same type of micro device but with different spacing between groups of micro devices, according to an embodiment of the invention;

FIG. 14A shows an example of a donor substrate or temporary substrate with output non-uniformities on a microdevice block according to an embodiment of the invention;

FIG. 14B shows an example of a receiver substrate or system substrate with output non-uniformity across multiple micro device blocks, according to an embodiment of the invention;

FIG. 14C shows an example of a system substrate with a skewed micro device tile, according to an embodiment of the invention;

FIG. 14D shows an example of a system substrate with flipped micro device tiles in accordance with an embodiment of the invention;

FIG. 14E shows an example of a system substrate with flipped and alternating micro device blocks according to an embodiment of the invention;

FIG. 15A shows an example of a donor substrate with two different micro device blocks, according to an embodiment of the invention;

FIG. 15B shows an example of a system substrate with deflection blocks for different micro devices according to an embodiment of the present invention;

FIG. 16A shows an example of a donor substrate with three different types of pixelated micro-device blocks, according to an embodiment of the invention;

FIG. 16B shows an example of a system substrate with multiple different types of individual micro devices from each block, according to an embodiment of the invention;

FIG. 17A shows an example of a cassette substrate with multiple different types of pixelated micro-device blocks, according to an embodiment of the invention; and is

FIG. 17B shows an example of a cassette substrate with multiple different types of offset pixelated microdevice blocks.

Detailed Description

While the present teachings are described in conjunction with various embodiments and examples, the present teachings are not intended to be limited to such embodiments. On the contrary, the present teachings encompass various alternatives and equivalents, as will be appreciated by those skilled in the art.

In this specification, the terms "device" and "microdevice" are used interchangeably. However, it will be clear to those skilled in the art that the embodiments described herein are independent of device size.

In this specification, the terms "donor substrate" and "microdevice substrate" are used interchangeably.

In this specification, the terms "receptor substrate", "system substrate" and "backplane" are used interchangeably.

Examples of optoelectronic devices are sensors and light emitting devices, such as, for example, Light Emitting Diodes (LEDs).

The present disclosure relates to a micro device array display device in which a micro device array can be bonded to a back plate by a reliable method. The micro device is fabricated over a micro device substrate. The micro device substrate may include micro Light Emitting Diodes (LEDs), inorganic LEDs, organic LEDs, sensors, solid state devices, integrated circuits, Micro Electro Mechanical Systems (MEMS), and/or other electronic components.

Light Emitting Diodes (LEDs) and LED arrays can be classified as vertical solid state devices. The micro device may be a sensor, a Light Emitting Diode (LED), or any other solid state device grown, deposited, or fabricated monolithically on a substrate. The substrate may be a native substrate of the device layer or a receptor substrate to which the solid state device is transferred.

The receptor substrate may be any substrate and may be rigid or flexible. The system substrate may be made of glass, silicon, plastic or any other commonly used material. The system substrate may also have active electronic components such as, but not limited to, transistors, resistors, capacitors, or any other electronic components commonly used in system substrates. In some cases, the system substrate may be a substrate having rows and columns of electrical signals. The system substrate may be a backplane with circuitry for obtaining micro LED devices.

FIG. 1A shows an embodiment of a donor substrate 110 having a lateral functional structure comprising a bottom planar or sheet-like conductive layer 112; functional layers 114, such as light-emitting quantum wells; and a top pixelated conductive layer 116.

Conductive layers

112 and 116 may be comprised of doped semiconductor material or other suitable type of conductive layer. The top conductive layer 116 may comprise several different layers. In one embodiment, as shown in FIG. 1B, a current distribution layer 118 is deposited on top of conductive layer 116. The current distribution layer 118 may be patterned. In one embodiment, the patterning may be performed by lift off. In another case, the patterning may be performed by photolithography. In an embodiment, the dielectric layer may be deposited and patterned first and then used as a hard mask for patterning the current distribution layer 118. After patterning the current distribution layer 118, the top conductive layer 116 may also be patterned, forming a pixel structure. After patterning the current distribution layer 118 and/or the conductive layer 116, a final dielectric layer 120 may be deposited over and between the patterned conductive layer 116 and the current distribution layer 118, as shown in fig. 1C. The dielectric layer 120 may also be patterned to create an opening 130 as shown in fig. 1D to provide access to the current distribution layer 118. An additional leveling layer 128 may also be provided to level the upper surface, as shown in FIG. 1E.

As shown in fig. 1E, a pad 132 is deposited in each opening 130 on top of the current distribution layer 118. The resulting structure with bond pads 132 is bonded to a system substrate 150 with bond pads 154, as shown in FIG. 1F. The pads 154 in the system substrate 150 may be separated by a dielectric layer 156. Other layers 152, such as circuitry, planarization layers, conductive traces, may be present between the system substrate pads 154 and the system substrate 150. Bonding of system substrate pads 154 to pads 132 may be performed by fusion bonding, anodic bonding, thermocompression bonding, eutectic bonding, or adhesive bonding. One or more other layers may also be deposited between the system device and the lateral device.

One case for pixelating the lateral functional structure from the top layer is described above. However, the pixelation of the lateral structures from the top can be done in different ways.

To improve pixelation or to adjust the light output profile, one or more of the bottom layers are patterned after separation of the donor substrate (or micro device substrate). The resolution of the patterned bottom layer is at least the same as the pixel resolution (however, it may be a higher resolution). The patterning may be done to completely isolate the layers, and the patterning may leave some thin layers between the patterns. In both cases, a common electrode (or patterned electrode) may be used in order to obtain connections to those layers.

As shown in fig. 1G, donor substrate 110 can be removed from the lateral functional device, such as conductive layer 112. The conductive layer 112 may be thinned and/or partially or fully patterned. In this case, the conductive layer 112 is thinned.

In some embodiments, a reflective layer or black matrix may be deposited and patterned to cover the regions of the conductive layer 112 between the pixels. After this stage, other layers may be deposited and patterned according to the function of the device. For example, a color conversion layer may be deposited to adjust the color of light produced by the lateral devices and pixels in the system substrate 150. One or more color filters may also be deposited before and/or after the color conversion layer. The dielectric layer in these devices, e.g., dielectric layer 120, may be an organic material such as polyamide or an organic material such as SiN or SiO₂、Al₂O₃And the like. The deposition can be performed with different processes, such as Plasma Enhanced Chemical Vapor Deposition (PECVD), Atomic Layer Deposition (ALD), and other methods. Each layer may be one deposited material or a combination of different materials deposited separately or together. The bonding material may be deposited only as a portion of pad 132 of donor substrate 110 or system substrate pad 154. For some of the layers, there may also be some annealing process. For example, the current distribution layer 118 may be annealed depending on the material. In one exampleThe current distribution layer 118 may be annealed at 500 c for 10 minutes. Annealing may also be performed after the different steps.

As shown in fig. 1H, the donor substrate 110 can be removed from the lateral functional device and the conductive layer 112 completely patterned to form an isolation pattern for the bottom planarization layer 112. In one case, the bottom planar layer is a bottom conductive layer. In one case, the bottom planar layer is a bottom doped layer.

Fig. 1I shows a cross-sectional view of an integrated structure having a patterned bottom conductive layer with ohmic contacts according to an embodiment of the invention. To obtain connections to those layers, ohmic contacts and/or common electrodes (or patterned electrodes) may be used.

In this case, a specific ohmic contact 202 is required to obtain a proper connection to the patterned bottom conductive layer 112. In one embodiment, the ohmic contact may be similar to the common conductive layer. In one case, the ohmic contact is a transparent material. In another case, if the ohmic contact is semi-transparent, the ohmic contact is patterned to provide a light output pathway. The pattern may be inside the isolated patterned conductive layer 112 or at the edge of the isolated patterned conductive layer 112. The isolated patterned conductive layer 112 may also have a 3D shape such as a lens (a portion of a sphere) to control the direction of light output.

Figure 1J illustrates a cross-sectional view of an integrated structure having an ohmic contact and a dielectric layer between patterned bottom electrodes according to an embodiment of the invention.

Figure 1J-1 illustrates the case where the ohmic contact 202-1 is inside the isolated patterned bottom conductive layer 112. A conductive layer 204 may be deposited and patterned around the isolated patterned bottom conductive layer 112. A dielectric layer may also be deposited prior to depositing the ohmic contacts 202.

Figure 1J-2 shows the case where the ohmic contact 202-2 is at the edge of the isolated patterned bottom conductive layer 112. In the case of an external ohmic contact layer, the layer may be used as a common electrode. In another case, another layer may be deposited on the top layer.

Fig. 1K shows a cross-sectional view of an integrated structure with another electrode covering a patterned bottom electrode, according to an embodiment of the invention. The common electrode 206 may be deposited over the patterned bottom conductive layer 112 with the ohmic contact 202 and the dielectric layer 204 therebetween.

Fig. 2A shows an exemplary embodiment of a donor substrate 210 having a lateral functional structure comprising 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-distributing layer 218; and/or bond pad layer 232. Fig. 2B shows all or one of the

patterned layers

216, 218, 232, forming a pixel structure. The

conductive layers

212 and 216 may be composed of a plurality of layers including a highly doped semiconductor layer. Some layers 228, such as a dielectric, may be used between

patterned post-layers

216, 218, and 232 to planarize the upper surface of the lateral functional structures, as shown in fig. 2C. Layer 228 may also perform other functions such as a black matrix. The resulting structure with pads 232 is bonded to a system substrate 250 with substrate pads 254, as shown in fig. 2D. The pads 254 in the system substrate may also be separated by a dielectric layer 256. Other layers 252, such as circuitry, planarization layers, and conductive traces, may be present between the system substrate pads 254 and the system substrate 250. The bonding may be performed, for example, by fusion bonding, anodic bonding, thermocompression bonding, eutectic bonding, or adhesive bonding. Other layers may also be deposited between the system means and the lateral means.

The donor substrate 210 may be removed from the lateral functional means. The conductive layer 212 may be thinned and/or patterned. A reflective layer or black matrix 270 may be deposited and patterned to cover the regions of the conductive layer 212 between the pixels. After this stage, other layers may be deposited and patterned according to the function of the device. For example, a color conversion layer may be deposited to adjust the color of the light produced by the lateral devices and pixels in the system substrate 250. One or more color filters may also be deposited before and/or after the color conversion layer. The dielectric layers, e.g. 228 and 256, in these devices may be organic, e.g. polyamideSubstances or materials such as SiN, SiO₂、Al₂O₃And the like. The deposition can be performed with different processes, such as Plasma Enhanced Chemical Vapor Deposition (PECVD), Atomic Layer Deposition (ALD), and other methods. Each layer may be one deposited material or a combination of different materials deposited separately or together. The material of bond pad 232 may be deposited as a portion of pad 232 of donor substrate 210 or system substrate pad 254. For some of the layers, there may also be some annealing process. For example, the current distribution layer 218 may be annealed depending on the material. In an example, the current distribution layer may be annealed at 500 ℃ for 10 minutes. Annealing may also be performed after the different steps.

In another embodiment, shown in fig. 3A, a mesa structure is created on a donor substrate 310. The microdevice structure is formed by etching through different layers, such as the first bottom conductive layer 312, the functional layer 314, and the second top conductive layer 316. Top contact 332 may be deposited before or after etching the top of top conductive layer 316. In another case, a multi-layer contact 332 may be used. In this case, a portion of the contact layer 332 may be deposited before etching and a portion of the contact layer may be deposited after etching. For example, an initial contact layer that creates an ohmic contact by annealing the conductive layer 316 may be first deposited. In one example, the initial contact layer may be gold or nickel. Other layers 372 such as dielectric or MIS (metal insulator structure) may also be used between the mesa structures to isolate and/or insulate each structure. After the microdevice is formed, a filler layer 374, such as polyamide, may be deposited, as shown in fig. 3B. The filler layer 374 can be patterned if only selected micro devices are transferred to the cartridge (temporary) substrate 376 during the next steps. The filler layer 374 can also be deposited after the device is transferred to a temporary substrate. The filler layer 374 can serve as a shell for the microdevice. By using a filler layer 374 prior to transfer, the lift-off process may be more reliable.

The device is bonded to a temporary substrate (cassette) 376. For example, the bonding source may vary and may include one or more of the following: electrostatic bonding, electromagnetic bonding, adhesive bonding, Van Der Waals force (Van-Der-Waals force) bonding, or thermal bonding. In the case of thermal bonding, a substrate bonding layer 378 having a melting temperature T1 may be used. Bonding layer 378 may be electrically conductive or may include a conductive layer and a bonding layer, which may be an adhesive bond, a thermal bond, or a light assisted bond. The conductive layer may be used to bias devices on the substrate 376 to identify defects and characterize performance. This structure may be used in other embodiments presented herein. To account for some surface profile non-uniformity, pressure may be applied during the bonding process. Temporary substrate 376 or donor substrate 310 may be removed and the device left on either. The process is explained herein based on leaving the device on temporary substrate 376, however, similar steps may be used when the device is left on donor substrate 310. After this stage, additional processes may be performed on the microdevice, such as thinning the device, creating a contact bonding layer 380 on the bottom conductive layer 312, and removing the filler layer 374. The device can be transferred to a system substrate 390 as shown in fig. 3D and 3E. Different techniques may be used to perform the transfer. In one case, the transfer is carried out using thermal bonding. In this case, the melting point of the contact bonding layer 380 on the system substrate contact pads 382 is T2, where T2> T1. Here, a temperature higher than T2 will melt both the substrate bonding layer 378 and the contact bonding layer 380 on the pads 382.

In a subsequent step, the temperature is reduced to between T1 and T2. At this point, the device is bonded to the system substrate 390 through the contact bonding layer 380 because the contact bonding layer 380 solidifies, but the substrate bonding layer 378 remains molten. Thus, moving temporary substrate 376 will leave the micro devices on system substrate 390, as shown in FIG. 3E. The process can be made selective by applying localized heating to selected pads 382. Also, in addition to local heating, a global temperature may be used, for example, by placing

substrates

376 and 390 in an oven and performing the process therein by increasing the overall atmosphere therein, thereby increasing the transfer rate. Here, the global temperature on the temporary substrate 376 or the system substrate 390 may be such that the temperature is close to the melting point of the contact bonding layer 380, e.g., 5 ℃ to 10 ℃ below the melting point, and the local temperature may be used to melt the contact bonding layer 380 and the substrate bonding layer 378 corresponding to the selected device. In another case, the temperature may be raised to near the melting point of substrate bonding layer 378 (above the melting point of contact bonding layer 378), e.g., 5 to 10 ℃ below the melting point, and for devices in contact with heated pad 382, the temperature transfer from pad 382 through the device melts selected regions of substrate bonding layer 378.

Fig. 3F shows an example of a thermal profile where the melting temperature Tr melts the contact bonding layer 380 and the substrate bonding layer 378 and the curing temperature Ts cures the contact bonding layer 380 with the bond pads 382 while the substrate bonding layer 378 is still molten. The melting may be localized or may at least make the bonding layer soft enough to release the microdevice or activate the alloying process. Here, other forces may also be used in combination or alone to hold the device on the bond pad 382. In another case, the temperature profile may be generated by applying a current through the device. Because the contact resistance will be high prior to bonding, the power dissipated across the bond pad 382 and the device will be high, melting the contact bonding layer 380 and the substrate bonding layer 378. As the bond forms, the resistance will drop and the power dissipation will also drop, thereby lowering the local temperature. The voltage or current through the pad 382 may be used as an indication of the quality of the bond and when to stop the process. Donor substrate 310 and temporary substrate 376 may be the same or different. After the device is transferred to the system substrate 390, different process steps may be performed. These additional processing steps may be planarization, electrode deposition, color conversion deposition and patterning, color filter deposition and patterning, and the like.

In another embodiment, the temperature used to release the micro devices from the cassette substrate 376 increases as the alloy begins to form. In this case, the temperature may be kept constant while the bonding alloy is formed on the bonding pad 382 of the receptor substrate 390 and the bonding layer is solidified, thereby keeping the micro device in place on the receptor substrate 390. At the same time, the bonding layer 378 on the cartridge 376 that is attached to the selected micro device is still molten (or soft enough) to release the device. Here, a portion of the material needed to form the alloy may be on the microdevice and another portion deposited on the bond pad 382.

In another embodiment, the filler layer 374 may be deposited on top of the cartridge substrate 376 to form a polymer filler/bonding layer 374/378. The microdevice from donor substrate 310 may then be pushed into polymer filler/tie layer 374/378. The microdevice can then be selectively or generally detached from the donor substrate 310. The polymer filler/tie layer 374/378 may be cured before or after the microdevice is separated from the donor substrate 310. The polymer filler/tie layer 374/378 may be patterned, particularly where multiple different devices are integrated into the cartridge substrate 376. In this case, the polymer filler/tie layer 374/378 may be created for one type, with the microdevice buried in the layer and separated from its donor body 310. Another polymeric filler/bonding layer 374/378 is then deposited and patterned for the next type of micro device. The second microdevice may then be buried in the associated layer 374/378. In all cases, the polymeric filler/bonding layer 374/378 may cover some or all of the microdevices.

Another method of increasing the temperature may be to use microwaves or lamps. Thus, layers can be deposited on: a bonding pad 382; a part of the pad 382; a micro device; or the cartridge 376 absorbs microwaves or light and locally heats a portion of the microdevice. Alternatively, the cartridge 376 and/or the receptor substrate 390 may contain heating elements that can selectively and/or globally heat the microdevice.

Other methods of separating the microdevice from temporary substrate 376 may also be used, such as chemical, optical, or mechanical forces. In one example, the microdevice can be covered with a sacrificial layer that can be debonded from the temporary substrate 376 by chemical, optical, thermal, or mechanical forces. The de-splicing process may be selective or global. In the case of global debonding, the transfer to the system substrate 390 is selective. If the process of debonding of the device from the temporary substrate (cassette) 376 is selective, a transfer force may be selectively or globally applied to the system substrate 390.

The transfer process from the cartridge 376 to the recipient substrate 390 can be based on different mechanisms. In one instance, the cartridge 376 has a bonding material that releases the device in the presence of light while the same light cures the bonding of the device to the receptor substrate.

In another embodiment, the temperature used to cure the bonding layer 380 of the device to the receptor substrate 390 releases the device from the cartridge 376.

In another case, the current or voltage cures the bonding layer 380 from the device to the donor substrate 310. The same current or voltage may cause the device to release from the cartridge 376. Here, the release may be a function of the piezo-electric or temperature generated by the current.

In another approach, after bonding of the curing device to the receptor substrate 390, the bonded device is pulled from the cassette 376. Here, the force holding the device to the cartridge 376 is less than the force bonding the device to the recipient substrate 390.

In another approach, the cartridge 376 has vias that can be used to push the device out of the cartridge 376 and into the recipient substrate 390. The pushing may be performed in different ways, such as using a micro-rod array or by pneumatic means. In the case of a pneumatic configuration, the selected device is disconnected. In the case of a micro-rod, the selected device is moved toward the receptor substrate 390 by passing the micro-rod through its associated via. The micron rods may have different temperatures to facilitate transfer. After the transfer of the selected device is complete, the micro-rods are retracted and the same rods are aligned with the vias of another set of micro-devices or a set of vias aligned with a new selected micro-device is used to transfer the new device.

In one embodiment, the cartridge 376 may be stretched to increase the device spacing in the cartridge 376 to increase throughput. For example, if the cartridge 376 is 1X 1cm²Where the device pitch is 5 microns and the pixel pitch of the receptor substrate 390 (e.g., display) is 50 microns, the cell 376 can fill 200 x 200(40,000) pixels at a time. However, if the cartridge 376 is stretched to 2X 2cm²Where the device spacing is 10 microns, the cartridge 376 can be filled at one time400 × 400(160,000) pixels. In another case, the cartridge 376 may be stretched such that at least two micro devices on the cartridge 376 become aligned with two corresponding locations in the recipient substrate. The stretching may be performed in one or more directions. The cartridge substrate 376 may include or consist of a stretchable polymer. The microdevice is also mounted in another layer or in the same layer as the cartridge substrate 376.

Combinations of the above-described methods may also be used in the process of transferring the microdevice from the cartridge 376 to the recipient substrate 390.

During the production of the cartridge (temporary substrate) 376, the microdevice may be tested to identify different defects and device performance. In one embodiment, the device may be biased and tested prior to separation of the top electrode. In the case where the device is an emissive device, a camera (or sensor) may be used to extract defects and device performance. Where the device is a sensor, a stimulus may be applied to the device to extract defects and performance. In another embodiment, the top electrodes 332 may be patterned into groups for testing before being patterned into individual devices. In another example, a temporary common electrode between more than one device is deposited or coupled to the device to extract device performance and/or extract defects.

The methods described above with respect to fig. 3A-3D, including but not limited to separating, forming filler layers, different roles of filler layers, testing, and other structures, can be used with other structures including those described below.

The methods discussed herein for transferring a microdevice from a cartridge 376 (temporary substrate) to a receiver substrate 390 may be applied to all cartridge and receiver substrate configurations presented herein.

The device on the donor substrate 310 can be created with two

contacts

332 and 380 on the same side facing away from the donor substrate 310. In this embodiment, the conductive layer on the cartridge 376 may be patterned to independently bias the two

contacts

332 and 380 of the device. In one case, the device can be transferred directly from the cartridge substrate 376 to the receptor substrate 390. Here, the

contacts

332 and 380 may not be directly bonded to the receptor substrate 390, i.e., the receptor substrate 390 need not have special pads. In this case, a conductive layer is deposited and patterned to connect

contacts

332 and 380 to appropriate connections in receptor substrate 390. In another embodiment, the device may first be transferred from the cassette 376 to a temporary substrate before being transferred to the recipient substrate 390. Here,

contacts

332 and 380 may be bonded directly to acceptor substrate pad 382. The device may be tested in the cassette 376 or in a temporary substrate.

In another embodiment, shown in fig. 4A, a mesa structure as described above is created on a donor substrate 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 is formed with a micro device structure. Top contact 432 may be deposited before or after etching on top of top conductive layer 416.

Temporary substrate 476 comprises a substrate that is initially filled with a filler material, for example, a soft material such as a polymer or a material such as SiO₂And a plurality of grooves 476-2 of a solid material such as SiN. The groove 476-2 is below the surface and/or substrate bonding layer 478. The device is transferred to a temporary substrate 476 on top of the slot 476-2 and the device includes contact pads 432. Also, each micro device may contain other passivation and/or MIS layers 472 surrounding each micro device for isolation and/or protection. The space between the devices may be filled with a filler material 474. After post-processing the device, another lower contact pad 480 may be deposited on the opposite surface of the device. Contact layer 412 may be thinned prior to depositing lower contact pad 480. The fill material 474 may then be removed and the grooves may be evacuated by various suitable means, such as chemical etching or evaporation, to cause or facilitate release of the surface and/or selected segments of the bonding layer 478. The device may be transferred to the system (receptor) substrate 490 using a process similar to that previously described hereinabove. Additionally, in another embodiment, a force applied from the pad 432, such as a pushing or pulling force, may damage the surface above the evacuated trench 476-2 and/or the bonding layer 478 while keeping the unselected mesa structures attached to the temporary substrate. This force may also release the device from the temporary substrate 476, as shown in fig. 4B and 4CShown in the figure. The depth of the slot 476-2 may be selected to manage some of the microdevice height differences. For example, if the height difference is H, the depth of the groove may be greater than H.

A device on the substrate 310 can be created with two

contacts

432 and 480 on the same side of the substrate 310 that faces away. In this case, the conductive layer on the cassette substrate 476 may be patterned to independently bias the two contacts of the device. In one case, the device can be transferred directly from the cartridge substrate 476 to a recipient substrate. Here,

contacts

432 and 480 will not be bonded directly to the recipient substrate (the recipient substrate need not have special pads). In this case, a conductive layer is deposited and patterned to connect

contacts

432 and 380 to appropriate connections in the receptor substrate. In another case, the device may first be transferred from the cassette 476 to a temporary substrate before being transferred to a recipient substrate. Here,

contacts

432 and 480 may be bonded directly to the receptor substrate pads. The device may be tested in a cassette or in a temporary substrate.

In another embodiment, shown in fig. 5A, a mesa structure as described above is created on a donor substrate 510 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 is formed with a micro device structure. Top contact pads 532 may be deposited before or after etching on top of top conductive layer 516. Moreover, each micro device may contain additional passivation and/or MIS layers 572 surrounding each micro device for isolation and/or protection. In this embodiment, the device may be provided with different anchors, whereby the anchors hold the device to the donor substrate 510 after the device is lifted off. The lift-off may be performed by a laser. In an example, the laser scans only the device. In an embodiment, a mask may be used that has openings for devices only on the backside 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 connected to the device to hold the device prior to the lift-off process. In another case, a filler layer 574, such as a dielectric, can be used between the devices.

In the first shown case, a layer 592 is provided for holding the device to the donor substrate 510. Layer 592 can be a separate layer or part of a layer of a microdevice that is not etched during the creation of the mesa structure. In another case, 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 SiO)₂Or other material). In another instance, the anchor is created as a separate structure including the extension 594, the void/gap 596, and/or the bridge 598. Here, a sacrificial layer having the same shape as the void/gap 596 is deposited and patterned. An anchor layer is then deposited and patterned to form the bridge 598 and/or the extension 594. The sacrificial material may be later removed to create the void/gap 596. The extension 594 may also be avoided. Similar to the previous anchor 592, the other anchor may be constructed of a different structural layer. In another case, the fill layer 574 acts as an anchor. In this case, the filling layer 574 may be etched or patterned, or left as it is.

Figure 5B shows the sample after removing filler layer 574 and/or etching the filler layer to form anchors. In another case, the adhesion of the bridging layer 598 is sufficient to hold the device in place and act as an anchor after lift-off. The final device on the right side of fig. 5B is shown in one substrate 510 for illustrative purposes only. One or a combination of the devices may be used in a substrate.

As shown in fig. 5C, the anchors may cover at least a portion of the perimeter of the device or the entire perimeter of the device, or may be patterned to form

arms

594 and 592. Any of the structures may be used for any anchoring structure.

Fig. 5D shows one example of transferring the device to a receptor substrate 590. Here, the micro device is bonded to the pads 582 or placed in a predefined area without any pads. The pressure or separation force may release the anchor by breaking the anchor. In another case, temperature may also 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. Fig. 5E illustrates the device after transfer to the receptor substrate 590 and shows possible release points 598-2 in the anchors. The anchors may also be connected to the donor substrate 510 directly or indirectly through other layers.

The device on the donor substrate 510 can be created with two

contacts

532 and 480 on the same side facing away from the donor substrate 510. In one case, the devices may be transferred directly from the donor substrate 510 to the acceptor substrate 590. Here,

contacts

532 and 480 may be bonded directly to recipient substrate pads 582. The device may be tested in the donor body 510 or in a cassette substrate. In another embodiment, the device may first be transferred from the donor substrate 510 to the cassette substrate before being transferred to the acceptor substrate 590. Here, the contacts 532 will not be bonded directly to the receptor substrate 590, i.e., the receptor substrate 590 need not have special pads 582. In this case, a conductive layer is deposited and patterned to connect contact 532 to the appropriate connection in receptor substrate 590.

The system or

acceptor substrates

390, 490, and 590 may include Light Emitting Diodes (LEDs), organic LEDs, sensors, solid state devices, integrated circuits, MEMS (micro-electro-mechanical systems), and/or other electronic components. Other embodiments relate to patterning and placing micro devices with respect to pixel arrays to optimize micro device utilization in selective transfer processes. The system or

acceptor substrate

390, 490, 590 can be, but is not limited to, a Printed Circuit Board (PCB), a thin film transistor backplane, an integrated circuit substrate, or in the case of an optical micro device such as an LED, a component of a display, such as a drive circuitry backplane. Patterning of the microdevice donor substrate and the receptor substrate may be used in combination with different transfer techniques, including but not limited to pick and place with different mechanisms (e.g., electrostatic transfer heads, elastomeric transfer heads) or direct transfer mechanisms such as dual function pads.

Fig. 6A shows an alternative embodiment of the mesa structure of fig. 3A-3F, where the mesa structure is not initially etched through all layers. Here, some portion of the buffer layer 312 and/or the contact layer 312 may remain during the initial step. A mesa structure is created on the donor substrate 310. The microdevice structure is formed by etching through different layers, such as the first bottom conductive layer 312, the functional layer 314, and the second top conductive layer 316. Top contact 332 may be deposited before or after etching the top of top conductive layer 316. The mesa structure may contain other layers 372 that will be deposited and patterned before or after the mesa structure is formed. These layers may be dielectrics, MIS layers, contacts, sacrificial layers, etc. After the mesa structure is created, one or more filler layers 374, such as dielectric materials, are used between and around the micro devices to hold the micro devices together. The micro device is bonded to a temporary substrate 376 by one or more substrate bonding layers 378. The one or more bonding layers 378 may provide one or more different forces, such as electrostatic, chemical, physical, thermal, and the like. After the devices are removed from donor substrate 310, additional portions of bottom conductive layer 312 may be etched away or patterned to separate the devices, as described above (fig. 6C). Other layers such as contact bonding layer 380 may be deposited and patterned. Here, the filler layer 374 may be etched to separate the micro devices, or the sacrificial layer may be removed to separate the devices. In another embodiment, temperature may be applied to separate the device from the filler layer 374 and prepare it for transfer to the receiver substrate 390. The separation may optionally be performed as described above. In another embodiment, filler layer 374 can be etched to form a shell, base, or anchor 375, e.g., in the shape of a truncated cone or a truncated pyramid, that at least partially surrounds each microdevice, as shown in fig. 6E. Another layer may be deposited over base 375 and may be used to form anchors 598-2. After additional layers 598-2 are formed, padding base layer 375 may be left behind or removed from the anchoring device. Fig. 6G shows a device with a sacrificial layer 372-2. The sacrificial layer 372-2 may be removed by etching or may be thermally deformed or removed.

In another embodiment, the anchors are identical to housing 375 and are constructed from a polymer layer, organic layer, or other layer after the microdevice is transferred to cartridge 376. The housing 375 may have different shapes. In one case, the housing may match the shape of the device. The housing sidewall may be shorter than the microdevice height. The housing sidewalls can be attached to the microdevice prior to the transfer cycle to provide support for various post-processing of the microdevices in cassette 376 and packaging of the microdevice cassette for shipping and storage. The housing sidewalls can be separated or the connections to the microdevice can be weakened by different means such as heating, etching, or exposure before or during the transfer cycle.

The device on the donor substrate 310 can be created with two

contacts

332 and 380 on the same side facing away from the donor substrate 310. In this case, the conductive layer on the cartridge 376 may be patterned to independently bias the two

contacts

332 and 380 of the device. In one case, the device can be transferred directly from the cartridge substrate 376 to the receptor substrate 390. Here,

contacts

332 and 380 will not be bonded directly to recipient substrate 390, i.e., recipient substrate 390 need not have special pads. In this case, a conductive layer is deposited and patterned to connect

contacts

332 and 380 to appropriate connections in receptor substrate 390. In another embodiment, the device may first be transferred from the cassette 376 to a temporary substrate before being transferred to the recipient substrate 390. Thus,

contacts

332 and 380 may be bonded directly to the receptor substrate pads. The device may be tested in the cassette 376 or in a temporary substrate.

Due to the mismatch between the substrate lattice and the microdevice layer, the growth of the layer contains several defects such as dislocations, voids, and the like. To reduce defects, at least one first buffer layer 6114 and/or second buffer layer 6118 with a separation layer 6116 in between or near it can be deposited first on the donor substrate 6110 and then the active layer 6112 is deposited over the buffer layer 6114 and/or 6118. The thickness of the buffer layers 6114 and 6118 can be quite large, e.g., as thick as the donor substrate 6110. Buffer layer 6114/6118 may also be detached during detachment (lift-off) of the microdevice from donor substrate 6110. Therefore, the buffer layer deposition should be repeated each time. Fig. 6H shows a structure over the substrate 6110, where a separation layer 6116 is interposed between the first buffer layer 6114 and the actual device layer 6112. A second buffer layer 6118 may be present between the separation layer 6116 and the device layer 6112. The second buffer layer 6118 may also prevent contaminants from the separation layer 6116 from penetrating the device layer 6112.

Buffer layers

6114 and 6118 may each include more than one layer. The separation layer 6116 may also comprise a stack of different materials. In one example, the separating layer 6116 reacts to wavelengths of light to which the other layers are not responsive. This light source may 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 reacts to a chemical without the same chemical affecting the other layers. Such chemicals may be used to remove or alter the properties of the separation layer 6116 to separate the device from the one or more buffer layers 6114/6118 and substrate 6110. This method leaves the first buffer layer 6114 intact on the donor substrate 6110 and, therefore, can be reused for the next device generation. Some surface treatment such as cleaning or buffering may be performed before the next device deposition. In another example, the one or more buffer layers 6114/6118 may include zinc oxide.

The microdevice may be separated by a different etching process before the separation process (lift-off), as shown in fig. 6I. The etching can etch the second buffer layer 6118 (if present), and can etch a portion or all of the separation layer 6116 and the device layer 6112. In another example, the second buffer layer 6118 or the separation layer 6116 is not etched. After the etching step, the micro device is temporarily (or permanently) bonded to another substrate 6150, and the separation layer 6116 is removed or modified to separate the micro device from the first buffer layer 6114 and the second buffer layer 6118. As shown in fig. 6J, the first buffer layer 6114 may remain substantially intact on the donor substrate 6110.

In another embodiment, shown in fig. 6K-6M, layers can be formed on the donor substrate 6210 in the form of islands 6212, such as a first bottom conductive layer 312, a functional layer 314, and a second top conductive layer 316. Figure 6K shows a top view of islands 6212 formed in the micro device array. The size of the island 6212 can be the same as or a multiple of the size of the box. The islands 6212 may be formed starting from the buffer layer 6114/6118 or after the buffer layer. Here, a surface treatment or formation of

gaps

6262, 6263 may be performed on the surface to initiate film growth as islands (fig. 6L). To handle the microdevice, the gap may be filled with a filler layer 6220, as shown at 6M. The filler 6220 may be composed of a polymer layer, a metal layer, or a dielectric layer. The filler layer 6220 can be removed after the microdevice is processed.

Fig. 7 highlights the process of creating a microdevice cartridge. During a first step 702, a micro device is fabricated on a donor substrate (e.g., 310 or 510). During this step, the device is formed and post-processing is performed on the device. During a second step 704, the device is prepared to be separated from the

donor substrate

310 or 510. This step may involve securing the microdevice by using anchors, e.g., 375, 476-1, 592, 594, 598, and 598-2, and fillers, e.g., 374, 472, and 574. During a third step 706, a cartridge or temporary substrate, e.g., 376 or 476, is formed by the pre-processed microdevices in the first step 702 and the second step 704. In one case, during this step, the microdevice is bonded directly or indirectly to the

cartridge substrate

376 or 476 by a bonding layer, such as 378 or 478. The microdevice is then separated from the

microdevice cartridge substrate

376 or 476. In another embodiment, the cartridge is formed on a microdevice donor substrate, such as 510. After the device is secured to the

cassette substrate

376, 476, or 510, other processing steps may be performed, such as removing some layers, e.g., 312, 374, 472, 574; an electrical layer (e.g., contact 380 or 480) or an optical layer (lens, reflector, etc.) is added. During a fourth step 708, the

cartridge

376 or 476 moves to a recipient substrate, such as 390, 490 or 590 to transfer the device to the

recipient substrate

390, 490 or 590. Some of these steps may be rearranged or combined. While the microdevice is still on the cartridge substrate, e.g., 376 or 476, or after the microdevice has been transferred to a recipient substrate, e.g., 390, 490 or 590, a test step 707A may be performed on the microdevice to determine if the microdevice is defective. Defective micro devices may be removed or repaired in situ in step 707B. For example, a predetermined number of a group of micro devices may be tested, and if the number of defects exceeds a predetermined threshold, the entire group of micro devices may be removed, at least some of the defective micro devices may be removed, and/or at least some of the defective micro devices may be repaired.

FIG. 8 illustrates the step of transferring the device from the

cartridge

376, 476, or 510 to a

recipient substrate

390, 490, or 590. Here, during a first step 802, the

cartridge

376, 476, or 510 is loaded (or picked up), or in another embodiment, the spare equipment arm is pre-loaded with the

cartridge

376, 476, or 510. During a second step 804, the

cartridge

376, 476, or 510 is aligned with a portion (or all) of the receptor substrate. The alignment may be performed using dedicated alignment marks on the

cartridge

376, 476, or 510 and the

receptor substrate

390, 490, or 590 or using micro-devices and landing areas on the

receptor substrate

390, 490, or 590. During a third step, the micro device is transferred to a selected landing area. During a fourth step 808, if the

recipient substrate

390, 490 or 590 is completely filled, the

cassette substrate

376, 476 or 510 is moved to a next step 810, such as another

recipient substrate

390, 490 or 590. If the

current receiver substrate

390, 490 or 590 requires further filling, then one or more

additional cassettes

376, 476 or 510 are used to perform additional transfer steps. Before the new transfer loop, if 376, 476 or 510 does not have enough devices, the loop starts with a first step 802. If the

cartridge

376, 476, or 510 has sufficient devices in step 812, the

cartridge

376, 476, or 510 is shifted (or moved and aligned) to a new area of the

recipient substrate

390, 490, or 590 in step 814 and the new loop continues to step 806. Some of these steps may be combined and/or rearranged.

Fig. 9 illustrates the step of transferring the device from a cartridge, e.g.,

temporary substrate

376, 476, or 510, to a recipient substrate, e.g., 390, 490, or 590. Here, during a first step 902, the

cartridge

376 or 476 is loaded (or picked up), or in another embodiment, the standby equipment arm is pre-loaded with a cartridge. During a second step 902-2, a set of micro devices in which the number of defects is less than a threshold is selected in the

cartridge

376, 476, or 510. During a third step 904, the

cartridge

376, 476, or 510 and/or the

recipient substrate

390, 490, or 590 or using micro devices and landing areas on the

recipient substrate

390, 490, or 590. Then, during a third step 906, the micro device may be transferred to the selected landing area. In optional step 906-1, selected micro devices in the cartridge can be attached to the receptor substrate. In another optional step 906-2, the micro device can be tested for connection to a receptor substrate, for example, by turning on the micro device by biasing through the

receptor substrate

390, 490, or 590. If individual micro devices are found to be defective or non-functional, an additional adjustment step 906-3 may be performed to correct or repair some or all of the non-functional micro devices.

If the receptor substrate is completely filled, the

receptor substrate

390, 490, or 590 moves to the next step. If the

recipient substrate

390, 490 or 590 requires further filling, additional transfer steps from one or more

additional cassettes

376, 476 or 510 are performed. Before a new transfer loop, if 376, 476 or 510 does not have enough devices, the loop starts with a first step 902. If the

cartridge

376, 476, or 510 has sufficient devices, then in step 902-2, the

cartridge

376, 476, or 510 is shifted (or moved and aligned) to a new area of the

receptor substrate

390, 490, or 590.

FIG. 10 illustrates exemplary process steps for generating a

multi-type microdevice cartridge

376, 476, 510, or 1108. During a first step 1002, at least two different microdevices are fabricated on different donor substrates, e.g., 310 or 510. During this step, the device is formed and post-processing is performed on the device. During a second step 1004, the device is prepared to be separated from a donor substrate, e.g. 310 or 510. This step may involve securing the microdevice by using anchors, e.g., 375, 476-1, 592, 594, 598, and 598-2, and fillers, e.g., 374, 472, and 574. During a third step 1006, the first device is moved to the

cartridge

376, 476, 510, or 1108. During a fourth step 1008, at least a second microdevice is moved to a

cartridge

376, 476, 510, or 1108. In one case, during this step, the microdevice is bonded directly or indirectly to the

cartridge substrate

376, 476, 510, or 1108 through a bonding layer, such as 378 or 478. The microdevice is then separated from the

microdevice cartridge substrate

310 or 510. In the case of direct transfer, different types of microdevices may have different heights to assist direct transfer. For example, the second type of micro device transferred to

cartridge

376, 476, 510, or 1108 may be slightly higher than the first type of micro device (or the position on

cartridge

376, 476, 510, or 1108 may be slightly higher for the second micro device type). Here, after the

cartridge

376, 476, 510, or 1108 is completely filled, the microdevice height may be adjusted to flatten the surface of the

cartridge

376, 476, 510, or 1108. This can be done by adding material to the shorter microdevice or removing material from the taller device. In another case, the landing areas on the

receptor substrate

390, 490, or 590 may have different heights associated with differences in the

cartridges

376, 476, 510, or 1108. Another method of filling the

cartridge

376, 476, 510, or 1108 is based on picking. The micro device may be moved to the

cartridge

376, 476, 510, or 1108 by a pick-up process. Here, the force elements on the pick-up head may be uniform for the micro devices in one cluster in a

cartridge

376, 476, 510, or 1108, or a single force element may be used for each micro device. Also, the micro device may be moved to the

cartridge

376, 476, 510, or 1108 in other ways. In another embodiment, the additional devices are moved away from the

cartridge substrate

376, 476, 510, or 1108 of the first or second (third or other) micro device and the other types of micro devices are transferred into blank areas on the

cartridge

376, 476, 510, or 1108. After the device is secured to the

cartridge substrate

376, 476, 510, or 1108, other processing steps may be performed, such as adding filler layers 374, 474, or 574; removing some of the layers; an electrical layer (e.g., contact 380, 480, or 580) or an optical layer (lens, reflector, etc.) is added. The device may be tested after or before it is used to fill the

receptor substrate

390, 490 or 590. The test may be an electrical test or an optical test or a combination of both. The test may identify defects and/or performance of the devices on the cartridge. During a final step 1010, the

cartridge

376, 476, 510, or 1108 is moved to a

recipient substrate

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.

The transfer process described herein (e.g., fig. 7, 8, 9, and 10) may include a stretching step to increase the pitch of the micro devices on the

cartridges

376, 476, 510, or 1108. This step may be performed prior to alignment or may be part of the alignment step. This step may increase the number of micro devices aligned with the landing areas (or pads) on the

receptor substrate

390, 490, or 590. Further, the steps may match the pitch between the micro device arrays on the

cartridges

376, 476, 510, or 1108 that include at least two micro devices to match the pitch of the landing areas (or pads 382) on the

recipient substrates

390, 490, or 590.

FIG. 11 illustrates one example of a multi-type micro device cartridge 1108 that is similar to the

temporary substrate

376, or 510. The cartridge 1108 contains three different types of

micro devices

1102, 1104, 1106, e.g., colors (red, green, and blue), although there may be more device types. The distance x1, x2, x3 between micro devices is related to the pitch of the landing areas in the

receptor substrate

390, 490 or 590. After several devices, which may be related to the pixel pitch in the

receptor substrate

390, 490 or 590, there may be different pitches x4, y 2. This spacing is used to compensate for the mismatch between the pixel pitch and the micro device pitch (landing area pitch). In this case, if pick-and-place is used to create the cartridge 1108, the force elements may take the form of columns corresponding to the columns of each microdevice type, or the force elements may be separate elements for each microdevice.

Fig. 12 shows an example of a multi-type micro device cartridge 1208 similar to the

temporary substrate

376, 476, or 510. The cartridge 1208 contains three different types of

micro devices

1202, 1204, 1206, for example, colors (red, green, and blue). Other regions 1206-2 may be empty, filled with spare micro devices, or contain a fourth different type of micro device. The distance x1, x2, x3 between micro devices is related to the pitch of the landing areas in the

receptor substrate

390, 490 or 590. After several device arrays, possibly related to the pixel pitch in the

receptor substrate

390, 490 or 590, there may be different pitches x4, y 2. This spacing is used to compensate for the mismatch between the pixel pitch and the micro device pitch (landing area pitch).

Fig. 13 shows one example of a microdevice 1302 prepared on a donor substrate 1304 similar to the

donor substrate

310 or 510 prior to transfer to a

multi-type microdevice cell

376, 476, 510, 1108, 1208. Here, the support layers 1306 and 1308 may be used for a single device or a group of devices. Here, the pitch may match the pitch in the

cartridges

376, 476, 510, 1108, 1208, or the pitch may be a multiple of the cartridge pitch.

In all of the above configurations, the microdevice may be moved from the first cassette to the second cassette before filling the substrate with the microdevice. Additional processing steps may be performed after the transfer, or some of the processing steps may be divided between the first and second cassette arrangements.

Fig. 14A shows an embodiment of a micro device in a donor substrate 1480 similar to

donor substrate

310 or 510. Due to manufacturing and material defects, the output power of the micro device may gradually decrease or increase, i.e., there is non-uniformity, on the donor substrate 1480, as shown by the coloring from dark to light. Neighboring devices in the

receptor substrate

390, 490, or 590 gradually degrade because the devices may be transferred together into a block, such as block 1482, or may be transferred one or more devices at a time in sequence into the

receptor substrate

390, 490, or 590. However, where one block, e.g., 1482 or a series of adjacent blocks, ends and another block, e.g., 1483 or another series of blocks begins, e.g., along intersection line 1484, a worse problem may arise which may result in an abrupt change in output performance, as shown in fig. 14B. Such abrupt changes may result in visual artifacts of optoelectronic devices such as displays.

To address the issue of non-uniformity, one embodiment shown in FIG. 14C includes using blocks above and below

separate blocks

1482 and 1483 in the display to skew or interleave the separate blocks so that the edges or crosshairs of the blocks are not sharp lines, eliminating the crosshairs 1484, and thereby the device blocks form a skewed pattern on the display. Thus, the average effect of sharp transitions is significantly reduced. The skew may be random and may have different profiles.

Fig. 14D illustrates another embodiment in which the micro-device devices in adjacent blocks are flipped so that devices with similar performance are adjacent to each other, e.g., the performance in a first block 1482 decreases from a first outer side a to a first inner side B, while the performance of a second adjacent block 1483 increases from a second inner side B adjacent to the first inner side B to a second outer side a, which can keep the changes and transitions between blocks very smooth and eliminate long sharp intersections 1484.

FIG. 14E shows an exemplary combination of flipping devices, e.g., alternating high and low performance devices on the inside and skewing the edges to further improve the average uniformity. In the illustrated embodiment, the device performance alternates between high and low in both directions, i.e., in adjacent horizontal blocks and adjacent vertical blocks.

In one case, the performance of the micro devices at the tile edges are matched for adjacent transferred tiles (arrays) prior to transfer to the

receptor substrate

390, 490 or 590.

Fig. 15A shows the use of two or

more blocks

1580, 1582 to fill in blocks in an acceptor substrate 1590. In the illustrated embodiment, the average uniformity may be further improved using a skew or flip approach, as shown in FIG. 15B. The higher (or lower) output power sides B and C from

blocks

1580 and 1582, respectively, may be positioned adjacent to each other, in addition to which the connections of the blocks above and below the blocks are used to skew or interleave the connections between the blocks. Also, a random or defined pattern can be used to fill a cassette or receptor substrate 1590 having more than one patch.

Fig. 16A shows a sample with more than one

block

1680, 1682, and 1684.

Blocks

1680, 1682, and 1684 may be from the

same donor substrate

310 or 510 or from

different donor substrates

310 or 510. Fig. 16B shows an example of filling the box 1690 with

different blocks

1680, 1682, and 1684 to eliminate any non-uniformities found in the blocks.

Fig. 17A and 17B illustrate a structure having a plurality of cassettes 1790. As described above, the location of the cassette 1790 is selected in a manner that eliminates overlap of the same area in the

recipient substrate

390, 490, 590, or 1590 with a cassette 1790 having the same micro-devices during different transfer cycles. In one example, the cassettes 1790 can be independent, meaning that a separate arm or controller processes each cassette independently. In another embodiment, the alignment may be performed independently, but other operations may be performed simultaneously. In this embodiment, the

receptor substrate

390, 490, 590 or 1590 may be moved for ease of transfer after alignment. In another example, the cassettes 1790 move together for easy transfer after alignment. In another example, both the cassette 1790 and the

recipient substrate

390, 490, 590, or 1590 can be moved for ease of transfer. In another case, the cartridge 1790 may be assembled in advance. In this case, the frame or substrate may hold the assembled case 1790.

The distances X3, Y3 between cassettes 1790 may be multiples of the width X1, X2 or length Y1, Y2 of cassette 1790. The distance may be a function of the step size of the movement in different directions. For example, X3 ═ KX1+ HX2, where K is the step of moving to the left (directly or indirectly) to fill the

receiver substrate

390, 490, 590, or 1590 and H is the step of moving to the right (directly or indirectly) to fill the receiver substrate. The same reasoning can be used for the distance Y3 between cassettes 1790 and for the lengths Y1 and Y2. As shown in fig. 17A, the cassette 1790 can be aligned in one or two directions. As shown in fig. 17B, in another example, the cassette 1790 is misaligned in at least one direction. Each cassette 1790 can have independent controls for applying pressure and temperature to the

receptor substrate

390, 490, 590, or 1590. Other arrangements are possible depending on the direction of movement between the

recipient substrate

390, 490, 590 or 1590 and the cassette 1790.

In another example, the cassette 1790 may have different devices and thus fill different areas in the

recipient substrate

390, 490, 590, or 1590 with different devices. In this case, the relative positions of the cassette 1790 and the

recipient substrate

390, 490, 590 or 1590 are changed after each transfer cycle to fill different areas with all required microdevices from different cassettes 1790.

In another embodiment, several cartridge arrays 1790 are prepared. Here, after transferring the device from the first cartridge array to the

acceptor substrate

390, 490, 590, or 1590, the

acceptor substrate

390, 490, 590, or 1590 moves to the next micro device array to fill the remaining area in the

acceptor substrate

390, 490, 590, or 1590 or receive a different device.

In another example, the cassette 1790 may be on a curved surface, and thus the circular movement provides a contact point for transferring the micro device into the

recipient substrate

390, 490, 590 or 1590.

The vertical optoelectronic stack comprises 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 said substrate.

In one embodiment, the process of altering the properties of the one or more separation layers includes chemical reactive etching or deforming the separation layer.

In another embodiment, the process of altering the properties of the one or more separation layers comprises exposure to an optoelectronic wave, thereby deforming the separation layers.

In another embodiment, the process of changing the property of the one or more separation layers comprises changing the temperature, thereby deforming the separation layer.

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

In one embodiment, the surface treatment uses chemical or physical etching or buffing.

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

In one embodiment, the optoelectronic device is a light emitting diode.

In one embodiment, the separation layer is zinc oxide.

Embodiments of the invention include continuous pixelated structures comprising fully or partially continuous active layers, pixelated contact layers and/or current spreading layers.

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

In the above embodiments, there may be a dielectric opening on top of each pixelated contact layer and/or current spreading layer.

Another embodiment includes a donor substrate including micro devices having bond pads and a filler layer filling spaces between the micro devices.

Another embodiment includes a temporary substrate that includes a bonding layer to which a micro device from a donor substrate is bonded.

Another embodiment includes a heat transfer technique comprising the steps of:

1) aligning the micro device on the temporary substrate with a bond pad of the system substrate;

2) the melting point of the bonding pad on the system substrate is higher than the melting point of the bonding layer in the temporary substrate;

3) creating a thermal profile that melts both the bonding pad and the bonding layer and after that keeps the bonding layer molten and the bonding pad solidified; and

4) separating the temporary substrate from the system substrate.

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

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

Another embodiment includes a transfer technique for a micro device structure in which an anchor releases the micro device after or during bonding of the micro device to a pad in a recipient substrate by a pushing or pulling force.

In another embodiment, the anchors according to the microdevice structure are comprised of at least one layer extending from the side of the microdevice to the substrate.

In another embodiment, the anchors according to the microdevice structure are composed of a void or at least one layer on top of a void.

In another embodiment, the anchors according to the microdevice structure are comprised of a filler layer surrounding the device.

Another embodiment includes a structure according to a microdevice structure in which the viscosity of a layer lifted off between the microdevice and the donor substrate is increased by controlling the temperature to act as an anchor.

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.

Another embodiment includes a process of transferring a microdevice into a receptor substrate, wherein the microdevice is formed in a cartridge; aligning the cartridge with a selected landing area in a recipient substrate; and transferring the micro device associated with the selected landing area in the cartridge to a recipient substrate.

Another embodiment includes a process of transferring a microdevice into a receptor substrate, wherein the microdevice is formed in a cartridge; selecting a group of micro devices having a defective micro device less than a threshold; aligning a selected set of micro devices in the cartridge with a selected landing area in the recipient substrate; and transferring the micro device associated with the selected landing area in the cartridge to a recipient substrate.

Embodiments include cartridges having multiple types of microdevices transferred thereto.

Embodiments include microdevice cartridges in which a sacrificial layer separates at least one side of the microdevice from a filler layer or a bonding layer.

The sacrificial layer is removed to release the microdevice from the filler layer or the bonding layer.

The sacrificial layer releases the microdevice from the filler under certain conditions, such as high temperature.

The microdevice may be tested to extract information related to the microdevice including, but not limited to, defects, uniformity, operating conditions, and the like. In one embodiment, one or more microdevices are temporarily attached to a cartridge having one or more electrodes for testing the microdevice. In one embodiment, the other electrode is deposited after the microdevice is positioned in the cartridge. This electrode can be used to test the microdevice before or after patterning. In one embodiment, the cartridge is placed in a predefined position (which may be a holder). The cassette and/or the recipient substrate are moved for alignment. At least one selected device is transferred to a recipient substrate. If more micro devices are available on/in the cartridge, the cartridge or the recipient substrate is moved to align with a new area in the same recipient substrate or a new recipient substrate, and at least another selected device is transferred to a new location. This process may continue until the cartridge does not have enough micro devices, at which point a new cartridge may be placed in a predefined location. In one example, the transfer of the selected device is controlled based on information extracted from the cartridge. In one example, the defect information extracted from the cassette may be used to limit the number of defective devices transferred to the recipient substrate to below a threshold number by eliminating the transfer of a group of devices having a number of defects that exceeds a threshold, or the cumulative number of defects transferred will exceed a threshold. In another example, the boxes will be binned based on one or more extracted parameters, and each bin will be used for a different application. In another case, cells having similar properties based on one or more parameters will be used in a receptor substrate. The examples presented herein can be combined to improve cassette transfer performance.

In embodiments, physical contact and pressure and/or temperature may be used to transfer the device from the cartridge into the receptor substrate. Here, the pressure and/or temperature may generate an engagement force (clamping force) for holding the microdevice to the receptor substrate, and/or also the temperature may reduce a contact force between the microdevice and the cartridge. Thus, transfer of the microdevice to the receptor substrate is achieved. In this case, the locations assigned to the micro devices on the receiver substrate may have a higher profile than the rest of the receiver to enhance the transfer process. In embodiments, the cartridge is free of micro devices in areas that may come into contact with unwanted areas of the recipient substrate, such as locations assigned to other types of micro devices during the transfer process. The two instances may be combined. In embodiments, the dispensed locations of the microdevices on the substrate may have been wetted with adhesive or may have been covered with bonding alloy, or additional structures may be placed on the dispensed locations. In the stamping process, a separate cartridge, printing or other process may be used. In an embodiment, selected micro devices on the cassette may be moved closer to the recipient substrate to enhance selective transfer. In another case, the receiver substrate exerts a pulling force to assist or initiate transfer of the microdevice from the cartridge. The pulling force may be combined with other forces.

In one embodiment, the housing may support a microdevice in a cartridge. The housing may be fabricated around the microdevice on the donor substrate or the cassette substrate or separately, and then the microdevice is moved inside and bonded to the cassette. In one embodiment, at least one polymer (or another type of material) may be deposited on top of the cassette 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 can be patterned, especially if a plurality of different devices are integrated into the cartridge. In this case, the layer may be created for a type in which the microdevice is buried and separated from its donor. Another layer is then deposited and patterned for the next type of micro device. The second microdevice is then buried in the associated layer. In all cases, this layer may cover some or all of the microdevices. In another case, the housing is constructed from a polymer layer, an organic layer, or other layer after the transfer of the microdevice to the cartridge. The housing may have different shapes. In one case, the housing may match the shape of the device. The housing sidewall may be shorter than the microdevice height. The housing sidewalls can be attached to the microdevice prior to the transfer cycle to provide support for various post-processing of the microdevices in the cassette and packaging of the microdevice cassette for shipping and storage. The housing sidewalls can be separated or the connections to the microdevice can be weakened by different means such as heating, etching, or exposure before or during the transfer cycle. There may be a contact point holding the microdevice to the cartridge substrate. The contact point to the cartridge may be the bottom side or the top side of the device. The contact points may be weakened or eliminated by different means such as heating, chemical processes or exposure before or during transfer. This process may be performed for some selected devices or may be performed globally for all of the micro devices on the cartridge. The contacts may also be conductive to enable testing of the microdevice by biasing the device at the contacts and other electrodes connected to the microdevice. During the transfer cycle, the cartridge may be under the receptor substrate to prevent the microdevice from falling out of the housing with the contact points globally removed or weakened.

In one embodiment, the microdevice cartridge may include at least one anchor that holds the microdevice to the cartridge surface. The cassette and/or the receptor substrate are moved such that some of the micro devices in the cassette are aligned with some of the locations in the receptor substrate. This anchor may break under pressure during the pushing of the cassette and the receptor substrate towards each other or the pulling of the device through the receptor substrate. The micro device may be permanently resting on the receptor substrate. The anchors can be on the sides of the microdevice or on the top (or bottom) of the microdevice.

The top side is the side of the device facing the cartridge and the bottom is the opposite side of the microdevice. The other sides are referred to as sides or sidewalls.

In one embodiment, the microdevice may be tested to extract information related to the microdevice including, but not limited to, defects, uniformity, operating conditions, and the like. The cartridge may be placed in a predefined position (which may be a holder). The cassette and/or the receptor substrate may be moved to perform alignment. At least one selected device may be transferred to a recipient substrate. If more micro devices are available on/in the cartridge, the cartridge or the recipient substrate can be moved to align with a new area in the same recipient substrate or a new recipient substrate, and at least another selected device can be transferred to a new location. This process may continue until the cartridge does not have enough micro devices, at which point a new cartridge will be placed in the predefined location. In one case, the transfer of the selected device may be controlled based on information extracted from the cassette. In one case, the defect information extracted from the cartridge may be used to limit the number of defective devices transferred to the recipient substrate to below a threshold number, or the cumulative number of defects transferred exceeds a threshold, by eliminating the transfer of a group of devices having a number of defects that exceeds a threshold. In another case, the cartridges would be binned based on one or more extracted parameters, and each bin could be used for a different application. In another case, cells having similar properties based on one or more parameters may be used in a receiver substrate. The examples presented herein can be combined to improve cassette transfer performance.

One embodiment includes a method of transferring a device to a receptor substrate. The method comprises the following steps:

a) preparing a cartridge having a substrate, wherein a micro device is positioned on at least one surface of the cartridge substrate, and the substrate has more micro devices in an area outside of a same sized micro device location corresponding to an area in a recipient substrate.

b) The device on the cartridge is tested by extracting at least one parameter.

c) The cassette is picked and transferred to a position with the micro device facing the recipient substrate.

d) The test data is used to select a set of micro devices on the cartridge.

e) A selected set of micro devices on the cartridge is aligned with selected locations on the receptor substrate. Transferring the set of micro devices from the cartridge to a recipient substrate.

f) Processes d and e may continue until the cartridge does not have any useful devices or the receptor substrate is completely filled.

One embodiment includes a cassette having more than one type of microdevice positioned in the cassette at the same pitch as in the recipient substrate.

One embodiment includes a cartridge having a substrate with micro devices positioned (directly or indirectly) on a surface thereof, and the micro devices are skewed in any row or column such that an edge of at least any one row or column is not aligned with an edge of at least another row or column.

One embodiment is a method of transferring a device to a recipient substrate. The method includes transferring an array of micro devices into a substrate, wherein an edge of a transferred micro device of at least any one row or column is not aligned with an edge of a transferred device of at least another row or column.

One embodiment includes a method of transferring a device to a receptor substrate. The method includes transferring an array of devices from a donor substrate to a recipient substrate, where in any area on the recipient substrate similar in size to the transferred array, there is at least any one row or column of micro devices having two different areas from the donor substrate corresponding to the transferred array.

One embodiment includes a process of transferring an array of micro devices into a recipient substrate, where the micro devices are deflected at the edges of the array to eliminate abrupt changes.

Another embodiment includes a process of transferring an array of micro devices into a receptor substrate, wherein the performance of the micro devices at adjacent edges of two arrays of micro devices are matched prior to transfer.

Another embodiment includes a process of transferring a micro device array into a receptor substrate, wherein the micro device array is filled from at least two different regions of a micro device donor substrate.

Another embodiment includes a process for transferring an array of micro devices from a cartridge to a receiver substrate, wherein a number of micro device cartridges are placed in different positions corresponding to different areas of the receiver substrate, then the cartridge is aligned with the receiver substrate, and the micro devices are transferred from the cartridge to the receiver substrate.

According to one embodiment, a method of fabricating a pixelated structure comprises: providing a donor substrate comprising a plurality of pixelated microdevices; bonding a selective set of the pixelated micro-devices from the donor substrate to a system substrate; and separating the donor substrate from the system substrate and then patterning at least one bottom planar layer of the pixelated microdevice, wherein the at least one bottom planar layer comprises one of: a bottom conductive layer or a bottom doped layer.

According to yet another embodiment, patterning the at least one bottom conductive layer may comprise one of: thinning the at least one bottom planarization layer or forming an isolation pattern of the at least one bottom conductive layer.

According to a further embodiment, the method may further comprise: providing an ohmic contact to the isolation pattern of the bottom conductive layer, wherein the ohmic contact is a transparent material or is opaque, wherein if the ohmic contact is opaque, patterning the ohmic contact to provide an optical pathway, wherein providing an ohmic contact to the isolation pattern of the bottom conductive layer comprises providing the ohmic contact inside the isolation pattern of the bottom conductive layer, and wherein providing an ohmic contact to an isolation pattern of a bottom conductive layer comprises providing the ohmic contact at an edge of the isolation pattern of the bottom conductive layer.

According to some embodiments, the method may further comprise: depositing a patterned dielectric layer between the isolation patterns of the bottom conductive layer, wherein the patterned dielectric layer is deposited before or after depositing the ohmic contacts.

According to another embodiment, the method may further comprise: providing an electrode over the patterned bottom conductive layer, wherein the electrode is one of: a common electrode or a patterned electrode.

According to one embodiment, the pixelated micro-device is formed by including the steps of: depositing the bottom conductive layer on the donor substrate; depositing a fully or partially continuous light-emitting functional layer on the bottom conductive layer; depositing a top conductive layer on the functional layer; and patterning the top conductive layer to form a pixelated micro device.

According to another embodiment, the method may further comprise: depositing a current distribution layer on the top conductive layer; depositing a dielectric layer between the patterned top conductive layer and the current distribution layer; and patterning the dielectric layer to form an opening for providing access to the current distribution layer.

According to some embodiments, bonding the selective set of the pixelated micro-devices from the donor substrate to a system substrate comprises the steps of: depositing a pad for each pixelated micro-device in each opening of the dielectric layer; and bonding contact pads of the system substrate with pads of the selected pixelated micro-device.

According to another embodiment, the contact pads of the system substrate are separated by a dielectric layer and the bonding between the contact pads of the system substrate and the pads of the selected pixelated micro-device is by one of: fusion bonding, anodic bonding, thermocompression bonding, eutectic bonding, or adhesive bonding.

According to some embodiments, a plurality of other layers are deposited between the contact pads and the system substrate and include a circuit layer, a planarization layer, and conductive traces.

According to one embodiment, the method further comprises: depositing a further patterned layer on the at least one bottom conductive layer, wherein the further layer comprises one of: a reflective layer, a color conversion layer, a color filter, or a black matrix.

The foregoing description of one or more embodiments of the invention has been presented for the purposes of illustration and description. The foregoing description is not intended to be exhaustive or to limit the invention to the precise form disclosed. Many modifications and variations are possible in light of the above teaching. It is intended that the scope of the invention be limited not by this detailed description, but rather by the claims appended hereto.

Claims

1. A method of fabricating a pixelated structure, comprising:

providing a donor substrate comprising a plurality of pixelated microdevices;

bonding a selective set of the pixelated micro-devices from the donor substrate to a system substrate; and

patterning at least one bottom planar layer of the pixelated micro-device after separating the donor substrate from the system substrate.

2. The method of claim 1, wherein the at least one bottom planar layer comprises one of: a bottom conductive layer or a bottom doped layer.

3. The method of claim 1, wherein patterning the at least one bottom planar layer comprises thinning the at least one bottom planar layer.

4. The method of claim 1, wherein patterning the at least one bottom planar layer comprises forming an isolation pattern of the at least one bottom planar layer.

5. The method of claim 4, further comprising:

providing an ohmic contact to the isolation pattern of the bottom planar layer, wherein the ohmic contact is a transparent material or is opaque.

6. The method of claim 5, wherein if the ohmic contact is opaque, the ohmic contact is patterned to provide an optical pathway.

7. The method of claim 5, wherein providing ohmic contact to the isolation pattern of the bottom planar layer comprises providing the ohmic contact inside the isolation pattern of the bottom planar layer.

8. The method of claim 5, wherein providing an ohmic contact to the isolation pattern of the bottom planar layer comprises providing the ohmic contact at an edge of the isolation pattern of the bottom planar layer.

9. The method of claim 1, further comprising:

depositing a patterned dielectric layer between the isolation patterns of the bottom planar layer.

10. The method of claim 9, wherein the patterned dielectric layer is deposited before or after depositing the ohmic contact.

11. The method of claim 1, further comprising:

providing an electrode over the patterned bottom planar layer, wherein the electrode is one of: a common electrode or a patterned electrode.

12. The method of claim 1, wherein the pixelated micro-device is formed by comprising:

depositing the bottom planar layer on the donor substrate;

depositing a fully or partially continuous luminescent functional layer on said bottom planar layer;

depositing a top conductive layer on the functional layer; and

the top conductive layer is patterned to form a pixelated micro device.

13. The method of claim 12, further comprising:

depositing a current distribution layer on the top conductive layer;

depositing a dielectric layer between the patterned top conductive layer and the current distribution layer; and

patterning the dielectric layer to form an opening for providing access to the current distribution layer.

14. The method of claim 13 wherein bonding the selective set of the pixelated micro-devices from the donor substrate to a system substrate comprises the steps of:

depositing a pad for each pixelated micro-device in each opening of the dielectric layer; and

bonding contact pads of the system substrate to pads of selected pixelated micro-devices.

15. The method of claim 14, wherein the contact pads of the system substrate are separated by a dielectric layer.

16. The method of claim 14, wherein the bonding between the contact pad of the system substrate and a pad of the selected pixelated micro-device is by one of: fusion bonding, anodic bonding, thermocompression bonding, eutectic bonding, or adhesive bonding.

17. The method of claim 14, wherein a plurality of other layers are deposited between the contact pad and the system substrate.

18. The method of claim 17, wherein the plurality of other layers comprises a circuit layer, a planarization layer, and a conductive trace.

19. The method of claim 1, further comprising:

depositing a further patterned layer on the at least one bottom planar layer, wherein the further layer comprises one of: a reflective layer, a color conversion layer, a color filter, or a black matrix.

20. The method of claim 1, wherein the depositing the additional patterned layer is performed by one of: plasma enhanced chemical vapor deposition PECVD or atomic layer deposition ALD.