TWI836592B - Methods of parallel transfer of micro-devices using mask layer - Google Patents

Abstract

A method of transferring micro-devices includes attaching micro-devices to one surface of a first body with a first adhesive layer, and selectively forming a masking layer on an opposite surface of the first body. A second adhesive layer on a second body is placed to contact the plurality of micro-devices. The first adhesive layer is exposed to illumination through the first body to create a neutralized portion while the masking layer blocks the illumination from reaching some of first adhesive layer to provide a less exposed portion that is more adhesive than the neutralized portion. The first surface is separated from the second surface such micro-devices on the less exposed portion of the first adhesive layer remain attached to the first surface and micro-devices corresponding to the neutralized portion attach to the second body and separate from the first surface.

Description

Method for parallel transfer of micro devices using mask layers

The present disclosure generally relates to transferring microdevices from a donor substrate to a destination substrate.

A wide variety of products include arrays of individual devices on a substrate that can be addressed or controlled by circuitry on the substrate. If the individual devices are micrometer-sized, for example, less than 100 micrometers in diameter, then the devices can be considered microdevices. In general, microdevices can be fabricated by depositing and patterning a series of layers using a range of microfabrication techniques such as deposition, lithography, and etching.

One way to make a device comprising an array of individual microdevices is to make the individual microdevices directly on a substrate that will form part of a product. This technique has been used, for example, to make TFT panels and color filter panels for active matrix liquid crystal displays (LCDs).

One proposed display panel technology uses an LED array, where individual LEDs provide individually controllable pixel elements. Such LED panels can be used in computers, touch panel devices, personal digital assistants (PDAs), cell phones, television monitors, etc.

Although organic light-emitting diode (OLED) panels are already in use, LED panels using micron-sized LEDs (also known as micro-LEDs) based on III-V semiconductor technology face more problems. In particular, depositing and growing III-V semiconductor micro-LEDs directly on the final display substrate poses technical and manufacturing hurdles. In addition, micro-LED panels are difficult to manufacture into curved or bendable displays.

The present disclosure generally relates to systems and methods for surface mounting microdevices over large areas.

In one aspect, a method of transferring microdevices includes the steps of: when a plurality of microdevices are attached to a first surface of a first body via a first adhesive layer, selectively processing the first adhesive layer to A treated portion of the adhesive layer and an untreated portion of the first adhesive layer are formed. The processed portion corresponds to one or more microdevices from the plurality of microdevices. When the plurality of micro devices are attached to the first surface through the first adhesive layer, the second surface of the second body is positioned relative to the first surface such that the second adhesive layer on the second surface is in the plurality of A side of each micro device opposite to the first surface is adjacent to the plurality of micro devices. Exposing the first adhesive layer to light in an area that overlaps at least some of the treated portions and at least some of the untreated portions, and exposing the first adhesive layer to light neutralizes the untreated portions. at least some of the portion to create a neutralized portion that is less viscous than the exposed area of the treated portion. Separating the first surface from the second surface such that one or more microdevices corresponding to the treated portion of the first adhesive layer remains attached to the first surface and one or more microdevices corresponding to the neutralized portion or a plurality of microdevices attached to the second surface and detached from the first surface.

In another aspect, a method of transferring microdevices includes the following steps: when a plurality of microdevices are attached to a first surface of a first body via a first adhesive layer, selectively treating the first adhesive layer to form a treated portion of the first adhesive layer and an untreated portion of the first adhesive layer, the treated portion partially but not completely extending through the first adhesive layer. The selective treatment causes the treated portion to have a higher opacity than the untreated portion for light of a first wavelength. When the plurality of microdevices are attached to the first surface via the first adhesive layer, positioning a second surface of a second body relative to the first surface so that a second adhesive layer on the second surface is adjacent to the plurality of microdevices on a side of the plurality of microdevices opposite the first surface. The first adhesive layer is exposed to light of the first wavelength in an area overlapping at least some of the treated portion and at least some of the untreated portion, and exposing the first adhesive layer to light neutralizes the at least some of the untreated portion to create a neutralized portion, while the treated portion blocks light from reaching at least some of the untreated portion, thereby providing a less exposed portion of the first adhesive layer that is more viscous than the neutralized portion. The first surface is separated from the second surface so that one or more microdevices corresponding to the treated portion of the first adhesive layer remain attached to the first surface, and one or more microdevices corresponding to the neutralized portion are attached to the second surface and separated from the first surface.

In another aspect, an apparatus for transferring a microdevice includes: a first body having a first surface for receiving a first adhesive layer; a second body having a second surface for receiving a second adhesive layer ; one or more actuators configured to provide relative movement between the first body and the second body; a first lighting system configured to selectively expose the first adhesive layer to a surface having a first a wavelength of light; a second illumination system configured to expose the first adhesive layer to light having a different second wavelength; and a controller configured to perform the necessary operations for implementing the process discussed above.

In another aspect, a method of transferring microdevices includes the steps of: attaching a plurality of microdevices to a first surface of a first body using a first adhesive layer; and connecting a plurality of microdevices to the first surface of the first body. The opposite side selectively forms a masking layer on the second surface of the first body. When the plurality of micro devices are attached to the first surface through the first adhesive layer, the third surface of the second body is positioned relative to the first surface such that the second adhesive layer on the third surface is in the plurality of A side of each micro device opposite to the first surface is adjacent to the plurality of micro devices. exposing the first adhesive layer to light through the first body to create a neutralizing portion, while the masking layer prevents the light from reaching at least some of the first adhesive layer to provide a less exposed portion of the first adhesive layer, The less exposed portion is more viscous than the neutralized portion. Separating the first surface from the second surface such that one or more microdevices corresponding to the less exposed portion of the first adhesive layer remains attached to the first surface and corresponds to the neutralizing portion One or more microdevices are attached to the third surface and separated from the first surface.

Implementations may optionally provide (and are not limited to) one or more of the following advantages. Microdevices on donor substrates can be built at a higher spatial density than required on the destination substrate, thereby increasing throughput and saving wafer space when building microdevices. A large number of microdevices can be transferred in parallel from the donor substrate to the destination substrate. This transfer can be performed with high precision. Therefore, the yield can be improved, and the manufacturing time and cost can be reduced. Defective microdevices on the donor substrate can be identified and excluded from this transfer. If the microdevices are arranged on the destination substrate at a different pitch than the donor substrate, the number of transfer steps can be reduced relative to previous techniques.

If the microdevices are micro-LEDs, the technology can be used to make multicolor displays, such as displays with three or more color sub-pixels. Flexible and/or stretchable displays can be made more easily.

Other aspects, features and advantages will be apparent from the description and drawings and claims.

Various implementations are described below. It is anticipated that elements and features of one implementation may be beneficially incorporated into other implementations without further recitation.

In order to manufacture some devices, new technologies are needed to accurately and economically provide micro devices on substrates such as large-area substrates or flexible substrates. For example, it is best to provide an LED panel based on III-V semiconductor technology, because micro LEDs have obvious advantages in brightness, life and efficiency compared with organic light-emitting diode (OLED) devices.

A method for fabricating an apparatus comprising an array of individual microdevices is to fabricate the microdevices collectively on an initial substrate and then transfer the microdevices to a receiving or destination substrate that will form part of a product. One reason for building the microdevices on an initial substrate is that the destination substrate may be a material that is incompatible with the fabrication processes (e.g., etching and deposition) required to form the microdevices. For example, in the case of LEDs, deposition of the LEDs is an epitaxial growth process in which single-crystalline gallium nitride (GaN) films are grown on sapphire wafers (sapphire wafers are used primarily due to the small lattice mismatch of GaN growth compared to other wafer materials). Another reason for building the microdevices on an initial substrate is that the microdevices can be fabricated at a higher spatial density than required by the destination substrate, thereby increasing yield and conserving wafer footprint when building the microdevices, thereby reducing costs.

One technique for transferring microdevices from an initial substrate to a destination substrate is a pick-and-place machine, such as a robot that transfers one microdevice at a time. However, this approach is not suitable for production because its throughput is very low, especially considering the large number of microdevices that need to be transferred.

As mentioned above, an improved method for fabricating microdevices is needed. As described below, a method for surface mounting microdevices over large areas is disclosed. The method includes the following steps: placing a transfer substrate with an adhesive layer over a micro-device on a donor substrate; adhering the adhesion layer to the micro-device; and removing the micro-device from the donor substrate while the micro-device is adhering to the adhesion layer. ; aligning the microdevice with the target location on the destination substrate; positioning the microdevice; exposing the transfer substrate to a light source to separate the microdevice from the transfer substrate; and moving away from the microdevice while the microdevice remains on the transfer substrate Move the transfer substrate. Microdevices using this approach can be transferred to a polymer photolayer and then transferred to a destination substrate using maskless lithography in a variety of patterns and can be transferred to a wide variety of substrates.

Additionally, maskless photolithography can be used to selectively release microdevices from the adhesive layer. Compared to projecting light onto an adhesive layer in a masked manner, maskless technology can adapt to different release patterns, is less expensive because a new mask does not need to be made for each release strategy, and because no mask needs to be made time, faster.

FIG. 1 illustrates a donor substrate 100 having an array of microdevices 110. The microdevices 110 are small electronic components, such as light emitting diodes (LEDs), and integrated circuit chips, such as logic ICs, processors, memories, controllers, etc. The microdevices 110 are micron-sized devices, for example, having a maximum lateral dimension of about 1 to 100 microns. For example, the devices can have a lateral dimension of about 1-50 microns, for example, 5-50 microns, for example, 10-30 microns. The microdevices 110 can be identical, i.e., identical in size, circuit pattern, and layer structure.

Although FIG. 1 illustrates microdevices 110 in a regular rectangular array with pitches PX1 and PY1 in two perpendicular directions parallel to the surface of the donor substrate, other array configurations are possible, such as a staggered arrangement.

Microdevice 110 can be fabricated directly on donor substrate 100 . Alternatively, microdevice 110 may be fabricated on another substrate (eg, a device substrate) and then transferred to donor substrate 100 . For example, the device substrate may include a wafer (eg, a sapphire wafer) on which the micro-device is fabricated at a density that is relatively high compared to, for example, the destination substrate. In some embodiments, the microdevice is transferred from the device substrate to the donor substrate without changing its pitch.

As an example of transferring a micro device, the micro device can be fabricated on a device substrate, and the donor substrate 100 can include or be a tape in contact with the device. Then, the device substrate can be removed or singulated so that each micro device 110 is individually attached to the donor substrate, for example, tape.

As another example, the donor substrate 100 may include an adhesive layer 112 (see FIG. 4 ) that contacts the microdevice 110 on the device substrate. The microdevice can then be detached from the device substrate using a lift-off technique. For example, in laser lift-off techniques, a laser beam (e.g., an ultraviolet laser beam) is directed to the back side of the substrate. The laser beam passes through the wafer and ablates material at the interface between the microdevice and the wafer. When the donor substrate is removed, the microdevice is adhered to the donor substrate by the adhesive and is thereby lifted off from the device substrate. In some embodiments, the adhesive layer is an adhesive that is UV-sensitive and becomes non-adhesive (also known as "neutralized") when exposed to UV light.

Figure 2 illustrates a destination substrate 200 having an array of cells 205, each cell having a site 210 for receiving a microdevice 110. Therefore, these sites 210 are also arranged in an array. However, the spacing of the array of sites 210 on the destination substrate 200 may be different from the spacing of the microdevices 110 on the donor substrate 100 . Typically, the spacing between sites 210 is greater than the spacing between microdevices 110 on the donor substrate 100 . For example, FIG. 2 illustrates sites 210 in a rectangular array with pitches PX2 and PY2 in two vertical directions parallel to the surface of destination substrate 200. Therefore, the pitch PX2 may be greater than the pitch PX1, and the pitch PY2 may be greater than the pitch PY1. As mentioned above, other array configurations are possible, for example, staggered arrangements. Because the spacing between sites 210 is different from the spacing between microdevices 110, the donor substrate 100 cannot simply be placed adjacent to the destination substrate 200 to collectively transfer the microdevices.

Although not illustrated in Figure 2, the destination substrate 100 (especially if it is a substrate that will form part of a product) may include means for delivering power and/or control to the microdevice 110 when properly secured in site 210. These microdevices address and/or control the circuitry and other components of these microdevices. For example, each site 210 may include one or more bonding pads that will be electrically connected to one or more bonding pads on the microdevice 110 .

Figure 13A illustrates a system 600 for transferring a microdevice from a donor substrate 100 to a destination substrate 200. For purposes of discussion, the Z-axis is a direction perpendicular to the plane of the substrates 100, 200, and the X-axis and Y-axis are two perpendicular directions parallel to the plane of the substrate 400. Typically, the Z axis will be the vertical axis, i.e. aligned with gravity, but this is not required.

The apparatus 600 includes a first support 610 for supporting the donor substrate 100 , a second support 510 for supporting the destination substrate 200 , and a transfer device 630 . The first support 610 may be an edge support ring supporting the edge of the donor substrate 100 . The second support 510 may be a platform on which the destination substrate 200 is located.

Transfer device 630 includes a surface 632 on which adhesive layer 420 can be placed. The transfer device 630 may include a retainer 520, such as an edge support ring or an edge gripper actuator, to hold a replaceable transfer substrate 410 that provides a surface 632 on which the adhesive layer 420 is formed. Alternatively, surface 632 may be an integral part of transfer device 630, for example, the transfer device includes a plate-like body having surface 632.

Surface 632 may be planar, for example, the bottom of a flat sheet, and may be parallel to the top surface of platforms 610, 510. Alternatively, surface 632 may be cylindrical, such as the outer surface of a rotatable drum.

One or more actuators 660 provide relative movement between transfer device 630 and supports 610 and 620. For example, transfer device 630 may include a three-axis robotic arm that may move surface 632 along the X, Y, and Z axes. However, many other arrangements are possible. For example, the platforms 610, 620 may move vertically while the arms only provide X- and Y-axis movement, or the platforms may move along the Y-axis, etc. Assuming that the transfer device 630 includes a replaceable transfer substrate 410, the robotic arm may include an end effector to hold the substrate. The end effector can be a vacuum suction cup or an edge gripper actuator.

The apparatus 600 also includes a system for selectively "neutralizing" a portion of the adhesive layer 112 that attaches the microdevice 110 to the donor surface substrate 100, and/or for selectively "neutralizing" the adhesive layer 420 on the surface 632. part of the system. In this context, "neutralization" includes completely removing the adhesive layer (such as by dissolving or melting), or modifying the physical properties of the material so that it is no longer sticky (also known as "denaturation" ). Each system may be an illumination system configured to selectively direct light from a light source to the backside of the body to which the microdevice is attached. In particular, device 600 may include illumination system 530 to selectively direct light onto the backside of donor substrate 100 and/or illumination system 580 to selectively direct light into the body providing surface 632 ( For example, the back side of the transfer substrate 410). Alternatively or additionally, the system may include individually controllable heaters embedded in the body providing surface 632 .

A controller 650 (e.g., a programmable computer) coordinates the operation of the various components of the apparatus (e.g., actuators 660 and illumination systems 530, 580). In operation, the adhesive layer 420 on the surface 632 is lowered into contact with the microdevices 110 on the donor substrate 100. The adhesive layer 112 is neutralized in selected areas, and the surface 632 is peeled off, wherein the microdevices 110 corresponding to the neutralized areas are fixed to the adhesive layer 420 and peeled off with the surface 632. The microdevices 110 on the adhesive layer 420 are moved laterally above the destination substrate 200 and lowered onto the destination substrate 200. The adhesive layer 420 is then neutralized in the selected areas, and the surface 632 with the remaining adhesive layer 420 is peeled off from the destination substrate 200, leaving microdevices on the destination substrate at locations corresponding to the neutralized areas of the adhesive layer 420. Although the above description is expressed as the surface 632 providing the relative motion, it will be understood that the motion of the supports 610, 620 may provide some or all of the necessary relative motion.

3 is a flowchart of a method 300 for transferring a plurality of microdevices from a donor substrate to a destination substrate. 4-12 are schematic cross-sectional side views illustrating a method of transferring multiple microdevices from a donor substrate to a destination substrate.

As shown in Figure 4, a donor substrate 100 having an array of microdevices 110 is manufactured or received from a manufacturing plant (step 304). Donor substrate 100 may include a body 114, such as a glass or sapphire wafer 114, on which adhesion layer 112 is formed. Body 114 is a material, such as glass or quartz, that is substantially transparent to the wavelengths of light that will be used to neutralize adhesive layer 112 . Adhesive layer 112 may be a UV-sensitive adhesive that becomes neutralized when exposed to UV light. For example, adhesive layer 420 may be an adhesive polymer, such as uncured or partially cured positive photoresist. The micro device 110 is fixed to the main body 114 via an adhesive layer 112 .

The adhesive layer 112 extends across at least the portion of the surface of the donor substrate 100 corresponding to the array of microdevices 110 . In some embodiments, the adhesive layer 112 is a continuous monolithic layer that spans all of the microdevices 110 . The advantage of such a layer is that the donor substrate 100 does not require precise lateral positioning relative to the device substrate during transfer. Alternatively, the adhesive layer 112 may be applied in individual spots corresponding to the location of the microdevice 110 on the device substrate 110, or in stripes or other patterns.

In some embodiments, the support body 114 is divided into a plurality of individual islands, each island corresponding to one of the microdevices 110 . However, in such an embodiment, the donor substrate 100 would need to be laterally positioned so that the islands are in contact with the microdevice 110 on the device substrate.

As shown in Figure 5, donor substrate 100 is positioned adjacent surface 632 of transfer device 630 (step 308). The donor substrate 100 is oriented such that the microdevice 110 is located on the side of the donor substrate 100 facing the transfer device 630 . The transfer device includes an adhesive layer 420. Adhesion layer 420 may be part of removable transfer substrate 400 . The adhesive layer 420 may also be a UV-sensitive adhesive that becomes neutralized when exposed to UV light. Adhesion layer 420 may be an adhesive polymer, such as uncured or partially cured positive photoresist.

The adhesive layer 420 extends across at least the portion of the surface 632 corresponding to the array of microdevices 110. In some embodiments, the adhesive layer 420 is a continuous single layer that spans all of the microdevices 110. An advantage of such a layer is that the transfer device 630 does not need to be precisely positioned laterally relative to the donor substrate 100. In some embodiments, the adhesive layer 632 is divided into a plurality of separate islands, each corresponding to one of the microdevices 110. However, in such embodiments, the transfer device 630 will need to be positioned laterally so that the islands are in contact with the microdevices 110 on the donor substrate 100.

Adhesive layer 420 may be applied to surface 632 of transfer device 630 by spin coating or droplet printing. The body (eg, backing substrate 410 ) providing surface 632 is a material, such as glass or quartz, that is substantially transparent to the wavelengths of light that will be used to cure or dissolve adhesive layer 420 .

Although FIG. 5 illustrates the adhesive layer 420 as a continuous layer, this is not required. For example, the adhesive layer 420 may be applied in individual locations corresponding to the locations of the microdevices 110 on the donor substrate 100, or in stripes or other patterns.

As shown in FIG. 6 , the transfer device 630 is then placed near the donor substrate 100 so that the microdevice 110 adheres to the adhesive layer 420 (step 312 ).

As an alternative to the method shown in FIGS. 5-6 , the adhesive layer 420 can be deposited directly onto the donor substrate 100 so that the adhesive material covers at least the microdevice 110 . For example, a large continuous layer of adhesive material 420 may be deposited across at least the array of microdevices 110 . Surface 632 of transfer device 630 may then be lowered into contact with adhesive layer 420.

Referring to FIGS. 6 and 7 , the connection between the microdevice 110 and the donor substrate 100 is severed (step 314 ). For example, selected areas 118 of the adhesive layer 112 corresponding to the microdevice 110 desired for delivery to the transfer device 630 are neutralized, eg, removed or denatured, by the radiation 130 from the illumination system 530 (see Figures 13A and 13B). Alternatively, if microdevice 110 is a direct If fabricated on a donor substrate 100, laser lift-off technology can be used to separate the micro-devices from the underlying wafer. For example, a light source (eg, a UV laser) may be used to ablate the area where each microdevice 110 is attached to the donor substrate 100 , thereby detaching the donor substrate 100 from the microdevice 110 . As another example, an infrared heat source may be used to melt the areas where microdevice 110 is attached to donor substrate 100 .

In some embodiments, not all microdevices 110 are transferred from the donor substrate 100 to the transfer device 630 . For example, the micro-device may be tested, eg, while attached to the donor substrate 100, to detect one or more defective micro-devices 110b. In this case, the area 118b of the adhesive layer 112 corresponding to the defective microdevice 110b is not neutralized.

As shown in FIGS. 7 and 8 , the donor substrate 100 can now be removed (step 316 ), leaving the microdevice 110 attached to the adhesive layer 420 on the transfer device 630 . Optionally, one or more microdevices (eg, defective microdevice 110b) will remain on the donor substrate 100. Assuming that the adhesion force of the micro device 110 to the adhesive layer 112 is stronger than the adhesion force of the micro device 110 to the adhesive layer 420 , the micro device will remain in the unneutralized region 118 b of the adhesive layer 112 .

As shown in Figures 8 and 9, one or more functional microdevices 110c can be optionally placed at one or more locations 422 of the untransferred microdevices on the transfer substrate 410, such as one or more locations corresponding to defective microdevices. For example, a conventional pick-and-place robot can be used to position the functional microdevices on the adhesive layer 420 on the transfer substrate 410.

Referring to FIG. 10 , transfer device 630 may be positioned to contact microdevice 110 with destination substrate 200 (step 320 ).

10 and 11, selected regions 430 of the adhesive layer 420 corresponding to the microdevices 110 desired to be transported to the destination substrate 200 are neutralized, e.g., removed or denatured (step 324). For example, light 450 can be selectively directed to the regions 430 by an illumination system 580 (see FIGS. 13A and 13C) through a body (e.g., backing substrate 410) providing a surface 632. The light 450 can neutralize (e.g., melt or dissolve) the regions 430 of the adhesive layer 420, or cure the regions 430 into a non-adhesive composition. In some embodiments, the light exposes the adhesive layer 420, and the exposed portion is removed with a developer.

As shown in Figures 12 and 14-15, once the selected area 430 is illuminated, the transfer device 630 can be peeled off, leaving the selected microdevice 110a in place on the destination substrate 200 (step 328). The remaining microdevice 110b whose adhesive layer 430 is not exposed remains on the transfer substrate 400.

FIG11B illustrates an apparatus 500 for transferring a microdevice from a donor substrate 100 to a transfer substrate 400. FIG11C illustrates a similar system 550 for transferring a microdevice from a transfer substrate 400 to a destination substrate 200. For purposes of discussion, the Z axis is the direction perpendicular to the plane of the transfer substrate 400, and the X axis and the Y axis are two perpendicular directions parallel to the plane of the transfer substrate 400. Typically, the Z axis will be a vertical axis, i.e., aligned with gravity, but this is not required.

Returning to FIG. 11B , the device 500 includes a support 610 , such as an edge support ring or an edge capture actuator, to support the donor substrate 100 and a retainer 520 , such as an edge support ring or edge capture actuator. , to hold the transfer substrate 400. An actuator 512, such as a linear actuator, may provide relative movement along the Z-axis between support 610 and retainer 520. Actuator 512 may be coupled and configured to move platform 510 along the Z-axis while retainer 520 remains stationary, or vice versa.

Device 500 also includes lighting system 530. Illumination system 530 includes a light source 532 and a mechanism to selectively direct light from the light source onto the backside of donor substrate 100 . In one embodiment, illumination system 530 includes a two-dimensional array of independently controllable mirrors, such as a digital micromirror device (DMD) 534 . Illumination system 530 may also include illumination optics 536 for directing light from light source 532 to DMD 534 , and/or projection optics 538 for directing light reflected by an activation mirror of DMD 534 onto adhesive layer 112 . By controlling which mirrors of DMD 534 are activated, light 450 can be selectively directed to desired areas 118 .

Referring to Figure 11C, apparatus 550 is similar to apparatus 500 and includes a platform 510 for supporting destination substrate 200, and a holder 520 for holding transfer substrate 400, such as an edge support ring or an edge gripper actuator. An actuator 562, such as a linear actuator, may provide relative movement along the Z-axis between platform 510 and retainer 520. As shown, actuator 512 may be coupled and configured to move platform 510 along the Z-axis while retainer 520 remains stationary, or vice versa.

The apparatus 500 also includes an illumination system 580. The illumination system 580 includes a light source 582 and a mechanism to selectively direct light from the light source onto the back side of the transfer substrate 400. In one embodiment, the illumination system 580 includes a two-dimensional array of independently controllable mirrors, such as a digital micromirror device (DMD) 584. The illumination system 580 may also include an illumination optical component 586 for directing light from the light source 582 to the DMD 584, and/or a projection optical component 588 for directing light reflected by an activated mirror of the DMD 584 onto the adhesive layer 420. By controlling which mirrors of the DMD 584 are activated, the light 450 can be selectively directed to the desired area 430.

11C , each of the DMD 534 and the DMD 584 may include a plurality of independent mirrors 550, such as a two-dimensional array of mirrors 550. Each mirror 550 may be independently tilted between a first position, such as shown by mirror 550a, in which incident light from the light source 532 is reflected and transmitted to the projection optical element 538 and illuminates a specific pixel in the imaging plane (e.g., the adhesive layer on the transfer substrate 400), and a second position, such as shown by mirror 550b, in which incident light from the light source 532 is reflected along a path such that the reflected light does not reach the imaging area (e.g., the adhesive layer on the transfer substrate 400). Mirrors 550 may be supported on posts 552 above a substrate 554 on which circuitry is formed to control each mirror 550; many other forms of DMDs are possible.

Each of the light sources 532 and 582 can be an arc lamp, such as a mercury arc lamp, or a laser, such as a solid-state laser diode. One end of a bundle of optical fibers can be coupled to one or more laser diodes; light from the other end of the optical fibers can be directed to illumination optics or sent directly to the DMD.

In some embodiments, one or more additional actuators provide relative motion between the support 610 or platform 510 and the holder 520 along the X-axis and the Y-axis. Likewise, the actuators can be coupled and configured to move the support 610 or platform 510 in the X-Y plane while the holder 520 remains stationary, or vice versa. For example, the support 610 or holder 520 can be positioned on a robotic arm that provides X-Y plane motion.

Additional discussion of lighting systems including DMDs can be found in U.S. Patent Publication Nos. 2016/0282728, 2016/0219684, and 2016/0124316. In particular, U.S. Patent Publication No. 2016/0124316 discusses an optical system that includes an illumination-projection beam splitter that can be used to direct light from light source 532/582 to DMD 534/ 584, and split the reflected light 130/450.

In some embodiments, the field of view of projection optics 538 or 588 spans the entire donor substrate 100 or transfer substrate 400. In this case, no lateral movement is required between light 130 and donor substrate 100 or between light 450 and transfer substrate 400 . However, in some embodiments, the field of view of projection optics 538 or 588 spans only a portion of donor substrate 100 or transfer substrate 400. In this case, between the exposure of the donor substrate 100 or the transfer substrate 400 , the actuator may provide the illumination system 530 and the donor substrate 100 or the illumination system 580 and the transfer substrate 400 in the X-Y plane, respectively. relative motion.

The illumination system 530 or 580 may include a linear mirror array rather than a two-dimensional mirror array, and the actuator may provide relative motion between the illumination system 530 or 580 and the transmission substrate 400 in the X-Y plane to scan the linear mirror array across the transfer substrate 400. Alternatively, the illumination system 530 or 580 may include a linear mirror array, and the actuator (e.g., a galvo) may rotate the linear DMD array 534 or 584 to scan the resulting reflected light across the donor substrate 410 or the transfer substrate 400.

As another embodiment, a beam (e.g., from a laser) can be raster scanned across the donor substrate 100 or the transfer substrate 400 and modulated as it scans to provide the same functionality as a DMD. For example, the illumination system 530 or 580 can include a dual-axis mirror gimbal that can rotate a single mirror around two perpendicular axes to scan the beam along two perpendicular axes on the transfer substrate. As another example, the illumination system 530 or 580 can include two galvanometer scanners in series (in series along the path of the beam), allowing the beam to scan along two perpendicular axes on the transfer substrate.

Referring to FIGS. 1-2 and 14 , the initial spatial density of the micro-devices on the donor substrate 100 is greater than the spatial density of the sites 210 on the destination substrate 200 , so the spatial density of the micro-devices on the transfer device 630 is also greater than that of the destination. The spatial density of sites 210 on substrate 200. However, assuming that sites 210 are aligned with specific microdevices 110 on the transfer substrate, only those microdevices 110 corresponding to sites 210 can be transferred. For example, if the distance PX2 is an integer multiple of the distance PX1 and the distance PY1 is an integer multiple of the distance PX2, then one of every (PX2*PY2)/(PX1*PY1) micro devices 110 will be transferred. For a rectangular array, the transferred microdevices 110 may be positioned every PX2/PX1 row and every PY2/PY1 column.

As shown in Figure 15, the resulting transfer device 630' will have unit 440 missing microdevice 110b. However, the transfer apparatus 630' may be reused for additional destination substrates 200. Briefly, steps 320, 324, 328 may be repeated, but with a different destination substrate, and using a different set of microdevices from the transfer device 630. That is, transfer device 630' may be positioned near a new destination substrate, but with a different set of microdevices aligned with site 120. For example, transfer device 630' may move one unit per cycle. Ideally, for a rectangular array, this would allow transfer device 630 to be used a total of (PX2*PY2)/(PX1*PY1) times.

As shown in FIG16 , some products may require multiple different types of micro devices 110i, 110j, 110k in each cell 205. For example, for a color LED display, three micro LEDs may be required, one each of red, blue, and green. Each micro LED can provide a sub-pixel. The sub-pixels can have various patterns. For example, sub-pixels of different colors can be simply arranged in a single column or row. Or, for example, the sub-pixels within a cell can be arranged in a plum blossom pattern, where two sub-pixels represent two colors, such as red and green, and there is a single sub-pixel of a third color, such as blue (this pattern is also called a PenTile matrix). Transfer technology can be used to form a display with more than three color sub-pixels, for example, a display with red, green, blue, and yellow micro LEDs.

Different color LEDs can be LEDs with phosphor layers that emit different colors of light, or they can be LEDs with different color filter layers, or they can be LEDs that emit white light but also absorb the white light and re-emit light of a different color. An LED superimposed with a phosphor material (this material could be quantum dots).

Different microdevices, such as microLEDs of different colors, can be fabricated on different donor substrates at a higher spatial density than required on the destination substrate. Each donor substrate can then undergo a transfer process. That is, a microdevice from each specific donor substrate can be transferred to its own transfer substrate. For example, there can be a transfer substrate with blue micro-LEDs, a transfer substrate with red micro-LEDs, and a transfer substrate with green micro-LEDs. For each transfer substrate, microdevices can be transferred to the destination substrate for each unit.

As shown in FIG. 17 , in some embodiments, the destination substrate 200 is a flexible substrate. For example, the destination substrate 200 may be a flexible circuit, and the micro device 110 may be a micro LED, thereby providing a flexible display screen. Alternatively or additionally, the destination substrate 200 may be a stretchable substrate.

The discussion above assumes that the donor substrate has microdevices correctly aligned with the destination site of each cell on the destination substrate (and therefore the destination substrate has such microdevices). This allows all microdevices to be transferred from the transfer substrate to the destination substrate in a single release operation (i.e., all corresponding areas of the adhesive layer are exposed simultaneously).

However, it may be the case that the spacing between microdevices on the donor substrate makes it impossible to transfer all microdevices to the destination location in a single release operation. For example, pitch PX2 may not be an integer multiple of pitch PX1 and/or pitch PY1 may not be an integer multiple of pitch PX2.

Still, it is possible to achieve significant increases in manufacturing throughput, at least compared to having to pick and place individual microdevices. Referring to Figure 18, the modified process allows microdevices to be placed in a rectangular array with arbitrary spacing relative to the original spacing of the microdevices on the donor substrate.

Initially, microdevice 110 is transferred from a donor substrate to a first surface of a first transfer device, eg, first transfer substrate 400a. The micro devices 110 are arranged on the first transfer substrate 110 with a pitch PX1 along the X axis and a pitch PY1 along the Y axis. The first transfer substrate 400a is then positioned adjacent the second surface of the second transfer device (eg, the second transfer substrate 400b). One row is transferred at a time, with the first transfer substrate laterally repositioned between each transfer to provide appropriate spacing in one of the directions, rather than transferring all microdevices at once. The microdevices are then transferred one column at a time from the second transfer substrate to the destination substrate, with the first transfer substrate laterally repositioned between each transfer to provide appropriate spacing in the other direction.

For example, assume that the destination substrate has N columns and M rows of cells to receive the micro devices 110. The first transfer substrate 400a is positioned adjacent to the second substrate 400b, and the lighting system is controlled to illuminate the area corresponding to the N micro devices 110 in the single row. Therefore, the single row containing the N micro devices 110 is transferred to the second transfer substrate 400b. Then, the first transfer substrate 400a is moved along the X axis relative to the second transfer substrate 400b, and the lighting system is controlled to illuminate the area corresponding to another N micro devices 100 in another single row, thereby placing another row of N micro devices. This process of moving and placing is repeated M-1 times until the micro devices of M rows and N columns are transferred to the second transfer substrate 400b. The movement amount of the first transfer substrate 400a relative to the second transfer substrate 400b makes the spacing of the micro devices on the second transfer substrate 400b along the X axis match the desired spacing PX2 of the destination substrate. The spacing of the micro devices along the Y axis can be PY1, or an integer multiple of PY1.

Once the array of M rows and N columns of microdevices is transferred to the second transfer substrate 400b, the microdevices 110 can be transferred to the destination substrate 200. The second transfer substrate 400b is positioned adjacent to the second substrate 400b, and the illumination system is controlled to illuminate the area corresponding to the M microdevices 110 in the single row. Thus, the single row containing the M microdevices 110 is transferred to the destination substrate 200. The second transfer substrate 400b is then moved along the Y axis relative to the destination substrate 200, and the illumination system is controlled to illuminate the area corresponding to another M microdevices 100 in another single row, thereby placing another row of M microdevices. This process of moving and placing is repeated N-1 times until the microdevices of N rows and M columns are transferred to the destination substrate 200. The movement amount of the second transfer substrate 400b relative to the destination substrate 200 makes the pitch of the micro devices on the destination substrate 200 along the Y axis match the desired pitch PY2 of the destination substrate 200. Therefore, the pitch of the micro devices on the destination substrate is now PX2 along the X axis and PY2 along the Y axis, and the relationship between PX1 and PX2 and between PY1 and PY2 is arbitrary.

One advantage of this multi-step transfer process is that the total number of transfer steps is approximately M+N. Although this total number of M+N may still be a large number for a high-resolution display, it is far smaller than the number of transfer steps that would be required for separate pick and place, that is, M*N.

In some embodiments, the microdevice is inspected or tested before being transferred to the destination substrate. Testing can be performed while the microdevice is still on the donor substrate, or it can be inspected while the microdevice is on the transfer substrate. For each unit in which inspection or testing indicates that the microdevice is defective, the lighting system of the transfer system is controlled not to illuminate the area of the transfer substrate corresponding to the defective microdevice. Therefore, identified defective microdevices are not transferred to the destination substrate. Any cell on the destination substrate that therefore lacks a microdevice can receive a functional microdevice in a later pick-and-place operation. This allows destination substrates, and thus products, to be manufactured at very high yields.

For some embodiments, depending on which side of the microdevice needs to contact the destination substrate, it may be necessary to transfer the microdevice to a third transfer substrate (which may be before the first transfer substrate, after the second transfer substrate, or between the first transfer substrate and the second transfer substrate) in order to flip the microdevice.

Another technique for controlling which microdevices are transferred from a donor substrate to a transfer substrate or from a transfer substrate to a destination substrate is to modify a portion of the adhesive layer so that it remains adhesive after subsequent processing steps. Figures 19-22 illustrate such a process.

As shown in FIG. 19 , the transfer substrate 410 of the transfer device 630 must be positioned adjacent to the donor substrate 100 so that the micro device 110 adheres to the adhesive layer 420 on the transfer substrate 410.

As shown in FIG. 20 , at least one region 112a of the adhesive layer 112 on the donor substrate 114 is treated so that it will remain sticky during a subsequent illumination step. For example, the adhesive layer 112 may be a material that reacts differently to exposure to two different wavelengths of light. The light of the first wavelength may neutralize the adhesive, for example, curing the material so that it is no longer sticky. In contrast, the light of the second wavelength may induce a chemical change in the material such that the material is no longer sensitive to the first wavelength. For example, the light of the second wavelength 132 may be directed from the back side of the donor substrate 100 through the donor substrate 100 to illuminate various regions of the adhesive layer 112. The light 132 may come from, for example, a laser scanning system or a digital micromirror device (DMD), such as an array as shown in FIG. 13D .

The processed area 112a may correspond to one or more defective microdevices 110b. For example, the microdevices may be tested, such as before the transfer substrate is positioned, to detect one or more defective microdevices 110b. The area 112a of the adhesive layer 112 corresponding to the detected defective microdevice 110b is processed.

Alternatively or additionally, the processed area 112a may correspond to one or more microdevices 110c that are not part of the subset of microdevices 110 to be transferred. For example, one can do to move microdevices positioned at a certain spacing, or only in certain columns or rows.

21, the adhesive layer 112 is then illuminated to neutralize (e.g., remove or denature) at least some portions of the untreated regions of the adhesive layer 112. For example, light 134 of a first wavelength may be directed through the back side of the transfer substrate 100. Such light 134 may illuminate both the treated and untreated regions of the adhesive layer.

In some embodiments, the entire adhesive layer 112 is illuminated. In this case, the light 134 may come from a general wide-area collimated light source, such as a lamp with an appropriate lens. Alternatively, the light can illuminate a selected area. In this case, light 134 may come from, for example, a laser scanning system or a digital micromirror device (DMD) array. In either case, the treated area 113a corresponding to the adhesive layer of microdevice 110b and/or 110c remains sticky. In contrast, other areas, such as the remainder of the adhesive layer 112, are neutralized.

The selection of adhesives 112 and 420 makes the processed area 112a of the adhesive layer 112 have stronger adhesion to the micro device than the adhesive layer 420. Therefore, as shown in FIG. 22, when the donor substrate 100 and the transfer substrate 410 are separated, the micro device 110b and/or 110c remain on the donor substrate 100, while the remaining micro device 110d is transferred to the transfer substrate 410.

Although Figures 19-22 illustrate each processed area 112a as a single fragment, this is not required. The treated area 112a may span a plurality of micro devices 110b/c and portions of the adhesive layer 112 between adjacent micro devices 110b/c.

Referring to FIG. 23 , the treated area 112 a does not necessarily extend through the entire thickness of the adhesive layer 112 . A certain depth of treatment of the adhesive layer 112 may be sufficient to cause the treated areas of the adhesive layer 112 to have stronger adhesion to the microdevice than the adhesive layer 420 .

Furthermore, referring to Figure 24, the treated area 112a does not necessarily extend across the entire width of the microdevice 110b/c. For example, treated area 112a may extend across only a portion of the surface area of microdevice 110b/c. Likewise, treating the adhesive layer 112 across a certain percentage of the surface area of the microdevice may be sufficient to provide the treated area 112a with stronger adhesion to the microdevice than the adhesive layer 420 . The treated areas can be in the corners, or overlap the edges, or in the center of the micro device.

Returning to Figure 23, in addition to or in lieu of desensitizing the adhesive, portion 112a of adhesive layer 112 may be treated to block (eg, absorb) light of the first wavelength. For example, the adhesive layer 112 may include a material, such as a photoactive dye, that changes absorption of a first wavelength in response to being illuminated by light of a second wavelength. In particular, the adhesive layer 112 may be processed so that the portion 112 extends partially, but not entirely, through the thickness of the adhesive layer 112 . Therefore, the portion 112b of the adhesive layer between the treated portion 112a and the microdevice 110 will be less exposed to the light of the first wavelength during the subsequent illumination step. Thus, portion 112b can maintain stronger adhesion to the microdevice than adhesive layer 420.

Another technique for controlling which microdevices are transferred from the donor substrate to the transfer substrate or from the transfer substrate to the destination substrate is to deposit a masking layer on the backside of the appropriate substrate (such as the donor substrate) to provide the necessary support during the illumination step. During this step, the illumination of the corresponding area of the adhesive layer is blocked. Figures 25-29 illustrate such a process.

As shown in FIG. 25 , a masking layer 500 is selectively deposited onto the side of the donor substrate 100 opposite the adhesion layer 112 . Masking layer 500 is deposited at locations corresponding to microdevices 110b/110c that will not be transferred.

As shown in FIG. 26 , the transfer substrate 410 of the transfer device 630 is positioned adjacent to the donor substrate 100 so that the microdevice 110 adheres to the adhesive layer 420 on the transfer substrate 410 .

As shown in FIG27 , a masking layer 500 is deposited to form at least one masking region on the side of the donor substrate 100 opposite the adhesive layer 112. The masking layer 500 can be deposited by forming a layer across the entire donor substrate 100 and then selectively removed. For example, a metal layer can be deposited by a process such as CVD and then removed by etching with an appropriate photoresist. Alternatively, a positive or negative photoresist that blocks the wavelength of light used in the illumination step can be deposited, for example, by spin coating. The photoresist layer can then be illuminated, for example, by a laser scanning system or a digital micromirror device (DMD) array, and developed to remove appropriate portions of the photoresist. Alternatively, the masking layer 500 can be selectively deposited. For example, droplets of a material that is opaque to the wavelength of light used in the illumination step can be sprayed onto selected areas, such as by an inkjet printer.

As shown in FIG. 28 , light 138 may be directed through the donor substrate 100 from the backside of the donor substrate 100 to neutralize the adhesive layer 112 . However, light 138 is blocked by the masking layer 500 so that each corresponding area 112a is not exposed (or less exposed), thereby maintaining stickiness.

In some embodiments, the entire back side of the donor substrate 100 is illuminated. In this case, the light 138 can come from a general wide-area collimated light source, such as a lamp with an appropriate lens. Alternatively, the light can illuminate selected areas. In this case, the light 138 can come from, for example, a laser scanning system or a digital micromirror device (DMD) array. In either case, the masked areas 112a of the adhesive layer corresponding to the mask 500 remain adhesive. In contrast, other areas (such as the rest of the adhesive layer 112) are neutralized.

Then, as shown in FIG. 29 , when the donor substrate 100 and the transfer substrate 410 are separated, the micro devices 110b and/or 110c corresponding to the area covered by the mask 500 remain on the donor substrate 100, while the remaining micro devices 110d are transferred to the transfer substrate 410.

Although FIGS. 19-23 and 25-29 illustrate transfer from a donor substrate to a transfer substrate, similar processes may also be used to transfer a microdevice from a transfer substrate to a destination substrate. In particular, in any of the embodiments discussed above, the transfer substrate 410 and the adhesive layer 420 may replace the donor substrate 100 and the adhesive layer 112, respectively, and the destination substrate 200 may replace the transfer substrate 410 and the adhesive layer 420.

It should be understood that while a method of surface mounting a single microdevice has been described above, the method may also include more than one microdevice.

The controller may be implemented in a digital electronic circuit system, or in computer software, firmware or hardware, or in a combination thereof. The controller may comprise one or more computer program products, i.e. one or more computer programs, which are tangibly embodied in an information carrier, such as a non-transitory machine-readable storage medium or in a propagation signal, to be processed by the data A device (such as a programmable processor, computer, or multiple processors or computers) performs or controls its operations. A computer program (also called a program, software, software application, or code) may be written in any form of programming language (including a compiled or interpreted language), and it may be deployed in any form, including as a stand-alone program or as a module, component, subroutine, or other unit suitable for use in a computing environment. A computer program may be deployed to execute on a single computer or on multiple computers located at a single location or distributed across multiple locations and interconnected by a communications network.

The processes and logic flows described in this specification may be performed by one or more programmable processors executing one or more computer programs to perform functions by operating on input data and generating output. These processes and logic flows may also be performed by, and the apparatus may be implemented as, a special purpose logic circuit system such as an FPGA (field programmable gate array) or an ASIC (application specific integrated circuit).

Positioning terms, such as vertical and lateral, have been used. However, it should be understood that such terms refer to relative positioning, not absolute positioning relative to gravity. For example, lateral is a direction parallel to the substrate surface, while vertical is a direction orthogonal to the substrate surface.

Those skilled in the art will appreciate that the foregoing examples are illustrative and not restrictive. It is expected that all substitutions, enhancements, equivalents, and improvements that will become apparent to those skilled in the art upon reading the specification and studying the drawings are included within the true spirit and scope of the present disclosure. Therefore, it is expected that the claims appended hereto include all such modifications, substitutions, and equivalents that fall within the true spirit and scope of these teachings.

100:Donor substrate 110:Microdevices 112:Adhesive layer 114:Subject 118:Area 130:Radiation 132:Light 134:Light 138:Light 200: Destination substrate 205:Unit 210:site 304: Step 308:Step 312: Steps 314: Steps 316: Steps 320: Steps 324: Steps 328: Steps 400:Transfer substrate 410: Donor substrate 420:Adhesive layer 422: Location 430:Area 440:Unit 450:Light 500:Device 510:Platform 512: Actuator 520: retainer 530:Lighting system 532:Light source 534:Digital Micromirror Device (DMD) 536:Lighting optics 538:Projection optics 550:Device 552:Pillar 554:Substrate 562: Actuator 580:Lighting system 582:Light source 584:Digital Micromirror Device (DMD) 586:Lighting optics 588:Projection optics 600:System 610: first support member 630:Transfer device 632:Surface 650:Controller 660: Actuator 110a:Microdevices 110b:Microdevices 110c: Microdevices 110d:Microdevices 110i: micro device 110j:Microdevices 110k:Microdevices 112a:Area 112b: Part 118b:Region 400a: First transfer substrate 400b: Second transfer substrate 550a:Mirror 550b:Mirror PX1: spacing PX2: spacing PY1: spacing PY2: spacing

Figure 1 is a schematic perspective view of a donor substrate with an array of microdevices.

FIG. 2 is a schematic perspective view of a destination substrate.

3 is a flowchart of a method for transferring multiple microdevices from a donor substrate to a destination substrate.

4-12 are schematic cross-sectional side views illustrating a method of transferring multiple microdevices from a donor substrate to a destination substrate.

13A is a schematic cross-sectional side view of a system for transferring a microdevice from a donor substrate to a destination substrate.

13B is a schematic cross-sectional side view of a system illustrating an adhesive layer on a donor substrate.

FIG. 13C is a schematic cross-sectional side view of a system for illustrating a system for transferring an adhesive layer on a substrate.

FIG13D is a schematic perspective view of a digital micromirror device.

Figure 14 is a schematic perspective view of a destination substrate with an array of micro devices mounted thereon.

Figure 15 is a schematic perspective view of the transfer device after some microdevices have been transferred.

Figure 16 is a schematic perspective view of a destination substrate with multiple microdevices per unit.

Figure 17 is a schematic perspective view of a flexible substrate on which micro-LEDs have been mounted.

FIG. 18 is a schematic top view illustrating a multi-step transfer process.

19-22 are schematic cross-sectional side views illustrating another method of transferring a plurality of microdevices from a donor substrate to a transfer substrate.

Figure 23 is a schematic cross-sectional side view illustrating a process that extends partially through the thickness of the adhesive layer.

FIG. 24 is a schematic bottom view illustrating a process extending partially across a microdevice.

Figure 25 is a schematic cross-sectional side view illustrating formation of a masking layer on a substrate.

26-29 are schematic cross-sectional side views illustrating another method of transferring multiple microdevices from a donor substrate to a transfer substrate.

Similar reference characters in the various drawings identify similar elements.

Domestic storage information (please note the order of storage institution, date, and number) None

Overseas storage information (please note the storage country, institution, date, and number in order) None

100: Donor substrate

110: Micro equipment

112:Adhesive layer

114: Subject

138:Light

410: Donor substrate

420:Adhesive layer

500:Device

630: Transfer equipment

110b:Microdevices

110c: Micro equipment

112a: Area

Claims (20)

A method for transferring micro devices, the method comprising the following steps: attaching a plurality of micro devices to a first surface of a first body with a first adhesive layer; selectively forming a masking layer on a second surface of the first body on a side of the first body opposite to the first surface; when the plurality of micro devices are attached to the first surface by the first adhesive layer, positioning a third surface of a second body relative to the first surface so that a second adhesive layer on the third surface is adjacent to the plurality of micro devices on a side of the plurality of micro devices opposite to the first surface. The first adhesive layer is exposed to light through the first body to create a neutralized portion, while the masking layer blocks the light from reaching at least some of the first adhesive layer to provide a less exposed portion of the first adhesive layer, the less exposed portion having a greater viscosity than the neutralized portion; and the first surface is separated from the second surface so that one or more microdevices corresponding to the less exposed portion of the first adhesive layer remain attached to the first surface, and one or more microdevices corresponding to the neutralized portion are attached to the third surface and separated from the first surface. The method of claim 1, wherein selectively forming the masking layer includes the following steps: selectively depositing the masking layer. A method as described in claim 2, wherein selectively depositing the masking layer comprises the following steps: spraying droplets onto the second surface of the first body. The method of claim 3, wherein the droplets include a material that is opaque to the light. The method of claim 1, wherein selectively forming the masking layer includes the steps of depositing the masking layer across a first region and selectively removing a portion of the first region. The method of claim 5, wherein selectively removing a portion of the masking layer includes the following steps: etching the masking layer. The method of claim 6, wherein the masking layer includes a metal. The method of claim 1, wherein exposing the first adhesive layer to light includes the following steps: exposing the first adhesive layer across an area spanning all of the plurality of microdevices. The method of claim 1, wherein selectively forming a masking layer includes forming at least a portion of the masking layer across two or more adjacent microdevices. The method of claim 1, wherein selectively forming a masking layer includes forming at least a portion of the masking layer to be smaller than a cross-sectional area of a micro device. The method as claimed in claim 1, wherein the micro devices include micro LEDs. A method for transferring micro-devices, the method includes the following steps: when a plurality of micro-devices are attached to a first surface of a first body through a first adhesive layer, selectively processing the first adhesive layer to Forming a treated portion of the adhesive layer and an untreated portion of the first adhesive layer, the treated portion partially but not completely extending through the adhesive layer, the step of selectively treating causes the treated portion to react with a first The opacity of light of a wavelength is higher than that of the untreated portion; when the plurality of microdevices are attached to the first surface through the first adhesive layer, a first portion of a second body is positioned relative to the first surface. Two surfaces, such that a second adhesive layer on the second surface is adjacent to the plurality of micro devices on the side of the plurality of micro devices opposite to the first surface; placing the first adhesive layer on the treated part Exposing the first adhesive layer to light of the first wavelength in an area overlapping at least some of the untreated portion, wherein exposing the first adhesive layer to the light neutralizes the at least some of the untreated portion to create a neutral and portions, while the treated portion prevents the light from reaching at least some of the untreated portion, thereby providing a less exposed portion of the first adhesive layer that is more viscous than the neutralized portion. ; and separating the first surface from the second surface such that one or more microdevices corresponding to the treated portion of the first adhesive layer remain attached to the first surface and correspond to the neutralized portion one or A plurality of microdevices are attached to the second surface and detached from the first surface. The method of claim 12, wherein selectively treating the first adhesive layer comprises the steps of directing light of a different second wavelength onto the first adhesive layer. The method of claim 13, wherein directing the second wavelength of light onto the first adhesive layer includes the steps of: directing the light through the first body, and wherein exposing the first adhesive layer to light The method includes the following steps: illuminating the first adhesive layer through the first body. The method of claim 13, wherein directing the light of the second wavelength through the first body includes the following steps: scanning a beam with a laser scanning system. The method of claim 13, wherein selectively processing the first adhesive layer includes the following steps: activating a photosensitive dye. The method of claim 12, wherein exposing the first adhesive layer to light comprises the following steps: exposing the first adhesive layer across an area that spans all of the plurality of microdevices. The method of claim 12, wherein the micro devices include micro LEDs. The method of claim 12, wherein selectively processing the first adhesive layer includes the step of simultaneously processing an area of the first adhesive layer corresponding to two or more adjacent microdevices. The method of claim 12, wherein selectively processing the first adhesive layer includes the following steps: processing an area of the first adhesive layer that is smaller than a cross-sectional area of a micro device.