TW202315163A - Methods of parallel transfer of micro-devices using treatment - Google Patents

Abstract

A method of transferring micro-devices includes selectively treating a first adhesive layer to form a treated portion and an untreated portion while micro-devices are attached the first adhesive layer. A second adhesive layer on a second surface is placed to abut the micro-devices. The first adhesive layer is exposed to illumination in a region that overlaps at least some of the treated portion and at least some of the untreated portion. Exposing the first adhesive layer to illumination neutralizes the at least some of the untreated portion to create a neutralized portion that is less adhesive than an exposed area of the treated portion. The first surface is separated from the second surface such that micro-devices in the treated portion remain attached to the first surface and micro-devices in the neutralized portion are attached to the second surface and separate from the first surface.

Description

Method for transferring microdevices in parallel using processing

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

The various products include arrays of individual devices on a substrate that can be addressed or controlled by circuitry on the substrate. If these individual devices are on the micron scale, eg, less than 100 microns in diameter, then these individual devices may be considered microdevices. In general, a series of layers can be deposited and patterned using a series of microfabrication techniques (such as deposition, photolithography and etching) to fabricate microdevices.

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

One proposed display panel technology uses an array of LEDs in which individually controllable pixel elements are provided by individual LEDs. Such LED panels can be used in computers, touch panel devices, personal digital assistants (PDAs), mobile phones, TV monitors, and the like.

While 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, directly depositing and growing III-V semiconductor micro-LEDs on the final display substrate will bring technical and manufacturing obstacles. Additionally, Micro LED panels are difficult to manufacture into curved or bendable displays.

The present disclosure generally relates to systems and methods for large area surface mounting of microdevices.

In one aspect, a method of transferring microdevices includes the step of selectively treating the first adhesive layer when a plurality of microdevices are attached to the first surface of the first body by 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 microdevices are attached to the first surface by 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 plural A side of a 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 portion and at least some of the untreated portion, and exposing the first adhesive layer to light neutralizes the untreated 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 remain attached to the first surface and one corresponding to the neutralized portion One or more microdevices are attached to the second surface and detached from the first surface.

In another aspect, a method of transferring microdevices includes the step of: selectively treating the first adhesive layer when a plurality of microdevices are attached to the first surface of the first body by 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 extends partially but not completely through the first adhesive layer. The selective treatment results in the treated portion having a higher opacity to light of the first wavelength than the untreated portion. When the plurality of microdevices are attached to the first surface by 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 plural A side of a micro-device opposite to the first surface is adjacent to the plurality of micro-devices. The first adhesive layer is exposed to light at the first wavelength in regions 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 untreated portion. treating the at least some of the portions to create a neutralized portion, while the treated portion prevents light from reaching at least some of the untreated portion, thereby providing a less exposed portion of the first adhesive layer, the less exposed portion of the adhesive Sex is larger than the neutralization part. 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 one corresponding to the neutralized portion One or more microdevices are attached to the second surface and detached 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 motion between the first body and the second body; a first lighting system configured to selectively expose the first adhesive layer to a first wavelength of light; a second illumination system configured to expose the first adhesive layer to light having a second, different wavelength; and a controller configured to perform the necessary operations for implementing the processes 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 with a first adhesive layer; The opposite side selectively forms a masking layer on the second surface of the first body. When the plurality of microdevices are attached to the first surface by 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 among the plurality of A side of a 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 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 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 remain attached to the first surface and correspond to the neutralized portion One or more microdevices are attached to the third surface and detached from the first surface.

Embodiments may optionally provide (and are not limited to) one or more of the following advantages. Microdevices on the donor substrate can be built at a higher spatial density than required on the destination substrate, increasing yield and saving wafer space when building the microdevices. A large number of microdevices can be transferred in parallel from a donor substrate to a destination substrate. This transfer can be performed with high precision. Therefore, yield can be increased, and manufacturing time and cost can be reduced. Microdevices with defects on the donor substrate can be identified and excluded from the 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 microLEDs, the technology could be used to make multicolor displays, such as those with three or more colored subpixels. Flexible and/or stretchable displays could be more easily fabricated.

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

Various implementations are described below. It is contemplated that elements and features of one embodiment may be beneficially incorporated in other embodiments without further recitation.

To fabricate some devices, new technologies are needed to precisely and economically provide microdevices on substrates such as large-area substrates or flexible substrates. For example, it would be desirable to provide an LED panel based on III-V semiconductor technology, since micro-LEDs offer clear advantages in brightness, lifetime, and efficiency compared to organic light-emitting diode (OLED) devices.

One method for fabricating a device comprising an array of individual microdevices is to collectively fabricate the microdevices 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 microdevices on an initial substrate is that the destination substrate may be a material that is incompatible with the fabrication processes (such as etching and deposition) required to form the microdevices. For example, in the case of LEDs, the deposition of LEDs is an epitaxial growth process in which single-crystal gallium nitride (GaN) thin films are grown on sapphire wafers (the use of sapphire wafers is mainly due to the fact that GaN The grown lattice mismatch is small). Another reason for building microdevices on the initial substrate is that the microdevices can be fabricated at a higher spatial density than required on the destination substrate, increasing yield and saving wafer footprint when building microdevices, thereby Reduced costs.

One technique for transferring microdevices from an initial substrate to a destination substrate is a pick-and-place machine, for example, a robot that transfers microdevices one at a time. However, this method is not suitable for production because of its low yield, especially considering the large number of tiny devices that would need to be transferred.

As noted above, there is a need for an improved method of fabricating microdevices. As described below, a method for surface mounting of microdevices over large areas is disclosed. The method comprises the steps of: placing a transfer substrate having an adhesive layer over the microdevice on a donor substrate; adhering the adhesive layer to the microdevice; and removing the microdevice from the donor substrate while the microdevice is adhering to the adhesive layer ; aligning the microdevice with a target location on the destination substrate; placing the microdevice; exposing the transfer substrate to a light source to separate the microdevice from the transfer substrate; Move the transfer substrate. Microdevices using this method can be transferred to a polymer photolayer, then transferred to a destination substrate in a variety of patterns using maskless lithography, and can be transferred to a wide variety of substrates.

In addition, maskless lithography can be used to selectively release microdevices from the adhesive layer. Compared to projecting light onto the adhesive layer in a masked manner, maskless technology can accommodate different release modes and is less expensive since no new masks need to be fabricated for each release strategy, and since no mask time, faster.

FIG. 1 illustrates a donor substrate 100 with an array of microdevices 110 . Micro devices 110 are small electronic components, such as light emitting diodes (LEDs), and integrated circuit chips, such as logic ICs, processors, memories, controllers, and the like. Microdevice 110 is a micron-scale device, eg, having a largest lateral dimension of about 1 to 100 microns. For example, these devices may have lateral dimensions of about 1-50 microns, eg, 5-50 microns, eg, 10-30 microns. The microdevices 110 may be identical, ie, 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, eg, staggered.

The microdevice 110 can be fabricated directly on the donor substrate 100 . Alternatively, the microdevice 110 can be fabricated on another substrate, such as a device substrate, and then transferred to the donor substrate 100 . For example, a device substrate may comprise a wafer (eg, a sapphire wafer) on which microdevices are fabricated, at a relatively high density, eg, compared to the destination substrate. In some embodiments, the microdevices are transferred from the device substrate to the donor substrate without changing their pitch.

As an example of transferring microdevices that can be fabricated on a device substrate, the donor substrate 100 can include or be an adhesive tape that contacts the device. The device substrate may then be removed or singulated such that each microdevice 110 is individually attached to a donor substrate, eg, adhesive tape.

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

FIG. 2 illustrates a destination substrate 200 having an array of cells 205 each having a site 210 for receiving a microdevice 110 . Accordingly, 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 a rectangular array of sites 210 with pitches PX2 and PY2 in two perpendicular directions parallel to the surface of destination substrate 200 . Therefore, the pitch PX2 may be larger than the pitch PX1, and the pitch PY2 may be larger than the pitch PY1. As noted above, other array configurations are possible, eg, staggered. Since the spacing between sites 210 is different from that between microdevices 110, donor substrate 100 cannot simply be placed adjacent to destination substrate 200 to transfer the microdevices collectively.

Although not illustrated in FIG. 2 , destination substrate 100 (particularly if it is a substrate that will form part of a product) may include a These microdevices address and/or control circuitry and other components of these microdevices. For example, each site 210 may include one or more bond pads that will be electrically connected to one or more bond pads on the microdevice 110 .

FIG. 13A illustrates a system 600 for transferring microdevices 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 substrate 100 , 200 , and the X and Y axes 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 does not have to be.

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 supporter 610 may be an edge support ring supporting the edge of the donor substrate 100 . The second supporter 510 may be a platform on which the destination substrate 200 is positioned.

Transfer device 630 includes a surface 632 on which adhesive layer 420 may be placed. The transfer apparatus 630 may include a holder 520, eg, an edge support ring or an edge grab actuator, to hold a replaceable transfer substrate 410 that provides a surface 632 on which the adhesive layer 420 is formed. Alternatively, the surface 632 may be an integral part of the transfer device 630 , eg, the transfer device includes a plate-like body with the surface 632 .

Surface 632 may be planar, eg, the bottom of a flat sheet, and may be parallel to the top surface of platform 610 , 510 . Alternatively, surface 632 may be cylindrical, eg, the outer surface of a rotatable drum.

One or more actuators 660 provide relative motion 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 X-, Y-, and Z-axes. However, many other arrangements are also possible. For example, the platforms 610, 620 could move vertically while the arms only provide the Y axis and Y axis movement, or the platforms could move along the Y axis, etc. Assuming that the transfer apparatus 630 includes a replaceable transfer substrate 410, the robotic arm may include end effectors to hold the substrate. The end effector can be a vacuum chuck or an edge grab actuator.

Apparatus 600 also includes a system to selectively "neutralize" a portion of adhesive layer 112 attaching microdevice 110 to donor surface substrate 100, and/or selectively "neutralize" the portion of adhesive layer 420 on surface 632. part of the system. In this context, "neutralizing" includes removing the adhesive layer completely (for example, by dissolving or melting), or modifying the physical properties of the material so that it is no longer sticky (also known as "denaturing"). ). Each system may be an illumination system configured to selectively direct light from the 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 to the body providing surface 632 ( For example, transfer the back side of the substrate 410 ). Alternatively or additionally, the system may include individually controllable heaters embedded in the body providing the surface 632 .

A controller 650, such as a programmable computer, coordinates the operation of the various components of the device (eg, actuator 660 and lighting systems 530, 580). In operation, adhesive layer 420 on surface 632 is lowered into contact with microdevice 110 on 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 micro devices 110 on the adhesive layer 420 are moved laterally over the destination substrate 200 and lowered onto the destination substrate 200 . Then, the adhesive layer 420 is neutralized in the selected area, and the surface 632 with the remaining adhesive layer 420 is peeled off from the destination substrate 200, so that at the site corresponding to the area where the adhesive layer 420 is neutralized, the target Tiny devices are left on the ground plate. Although the above description has been expressed as the surface 632 providing relative movement, it will be appreciated that movement of the supports 610, 620 may provide some or all of the necessary relative movement.

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 a plurality of microdevices from a donor substrate to a destination substrate.

As shown in FIG. 4 , a donor substrate 100 having an array of microdevices 110 is fabricated or received from a fab (step 304 ). The donor substrate 100 may include a body 114, eg, a glass or sapphire wafer 114, on which an adhesive layer 112 is formed. Body 114 is a material, such as glass or quartz, that is substantially transparent to the wavelength 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 an uncured or partially cured positive photoresist. The micro device 110 is fixed to the main body 114 by the 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, adhesive layer 112 is a continuous monolithic layer that spans all of microdevice 110 . An advantage of such a layer is that during transfer the donor substrate 100 does not require precise lateral positioning relative to the device substrate. Alternatively, the adhesive layer 112 may be applied in individual locations corresponding to the locations of the microdevices 110 on the device substrate 110, or in stripes or other patterns.

In some embodiments, support body 114 is divided into a plurality of individual islands, each island corresponding to one of microdevices 110 . However, in such an embodiment, the donor substrate 1100 would need to be positioned laterally such that the islands make contact with the microdevices 110 on the device substrate.

As shown in FIG. 5 , the donor substrate 100 is positioned near the surface 632 of the transfer apparatus 630 (step 308 ). The orientation of the donor substrate 100 is 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 . The adhesive layer 420 may be a part of the removable transfer substrate 400 . Adhesive layer 420 may also be a UV sensitive adhesive that becomes neutralized when exposed to UV light. Adhesive layer 420 may be an adhesive polymer such as uncured or partially cured positive photoresist.

Adhesive layer 420 extends across at least a portion of surface 632 corresponding to the array of microdevices 110 . In some embodiments, adhesive layer 420 is a continuous monolithic layer that spans all of microdevice 110 . An advantage of this layer is that the transfer device 630 does not require precise lateral positioning relative to the donor substrate 100 . In some implementations, the adhesive layer 632 is divided into a plurality of individual islands, each island corresponding to one of the microdevices 110 . However, in such an embodiment, the transfer device 630 would need to be positioned laterally such 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 drop printing. The body (eg, backing substrate 410 ) providing surface 632 is a material, eg, glass or quartz, substantially transparent to the wavelengths of light that will be used to cure or dissolve adhesive layer 420 .

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

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

As an alternative to the method shown in FIGS. 5-6 , the adhesive layer 420 may be deposited directly onto the donor substrate 100 such 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 regions 118 of adhesive layer 112 corresponding to microdevices 110 desired to be delivered to transfer device 630 are neutralized, eg, removed or denatured, by radiation 130 from illumination system 530 (see FIGS. 13A and 13B ). Alternatively, if the micro-device 110 is fabricated directly on the donor substrate 100, laser lift-off techniques may be used to detach the micro-device from the underlying wafer. For example, a light source such as an ultraviolet 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 area where the microdevice 110 is attached to the donor substrate 100 .

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

As shown in FIGS. 7 and 8 , the donor substrate 100 may now be removed (step 316 ), leaving the microdevice 110 attached to the adhesive layer 420 on the transfer device 630 . Optionally, yet another microdevice (eg defective microdevice 110 b ) will remain on the donor substrate 100 . Assuming that the adhesion of the microdevice 110 to the adhesive layer 112 is stronger than the adhesion of the microdevice 110 to the adhesive layer 420, the microdevice will remain in the region 118b where the adhesive layer 112 is not neutralized.

As shown in FIGS. 8 and 9 , one or more functional microdevices 110 c may optionally be placed at one or more locations 422 of non-transferred microdevices on the transfer substrate 410 , for example in the same position as the defective microdevices. in one or more locations corresponding to the miniature device. For example, conventional pick and place robots can be used to position functional microdevices on the adhesive layer 420 on the transfer substrate 410 .

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

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

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

FIG. 11B illustrates an apparatus 500 for transferring microdevices from a donor substrate 100 to a transfer substrate 400 . FIG. 11C illustrates a similar system 550 for transferring microdevices from a transfer substrate 400 to a destination substrate 200 . For purposes of discussion, the Z axis is a direction perpendicular to the plane of the transfer substrate 400 , and the X and Y axes are two perpendicular directions parallel to the plane of the transfer substrate 400 . Typically, the Z axis will be the vertical axis, i.e. aligned with gravity, but this does not have to be.

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

Apparatus 500 also includes lighting system 530 . Illumination system 530 includes light source 532 and a mechanism to selectively direct light from the light source onto the backside of donor substrate 100 . In one embodiment, the 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 activation mirrors 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 FIG. 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 grab actuator. Actuator 562 , such as a linear actuator, may provide relative motion between platform 510 and holder 520 along the Z-axis. As shown, actuator 512 may be coupled and configured to move platform 510 along the Z-axis while holder 520 remains stationary, and vice versa.

Apparatus 500 also includes lighting system 580 . The illumination system 580 includes a light source 582 and a mechanism for selectively directing light from the light source onto the backside 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 . Illumination system 580 may also include illumination optics 586 for directing light from light source 582 to DMD 584 , and/or projection optics 588 for directing light reflected by activation mirrors of DMD 584 onto adhesive layer 420 . By controlling which mirrors of DMD 584 are activated, light 450 can be selectively directed to desired area 430 .

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

Each of light sources 532 and 582 may be an arc lamp, such as a mercury arc lamp, or a laser, such as a solid state laser diode. One end of a bundled set of fibers can be coupled to one or more laser diodes; light from the other end of the 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, actuators may be coupled and configured to move support 610 or platform 510 in the X-Y plane while holder 520 remains stationary, or vice versa. For example, support 610 or holder 520 may be positioned on a robotic arm that provides X-Y plane motion.

Additional discussion of lighting systems including DMDs can be found in US 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 a light source 532/582 to a 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 the light 130 and the donor substrate 100 or between the light 450 and the 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 can provide an illumination system 530 and the donor substrate 100 or an 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 array of mirrors rather than a two-dimensional array of mirrors, and the actuator may provide relative motion in the X-Y plane between the illumination system 530 or 580 and the transfer substrate 400 to span the transfer substrate. 400 scan linear array of mirrors. Alternatively, illumination system 530 or 580 may include a linear array of mirrors, and an actuator (eg, a galvo) may rotate linear DMD array 534 or 584 to scan the resulting reflected light across donor substrate 410 or transfer substrate 400 .

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

1-2 and FIG. 14, the initial spatial density of the microdevices 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 microdevices on the transfer device 630 is also greater than that of the destination. The spatial density of the sites 210 on the substrate 200 . However, assuming the sites 210 are aligned with specific microdevices 110 on the transfer substrate, only those microdevices 110 corresponding to the sites 210 may be transferred. For example, if the pitch PX2 is an integer multiple of the pitch PX1 and the pitch PY1 is an integer multiple of the pitch PX2, then one of every (PX2*PY2)/(PX1*PY1) microdevices 110 will be transferred. For a rectangular array, 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 the unit 440 missing the microdevice 110b. However, the transfer device 630 ′ can be reused for additional destination substrates 200 . In short, steps 320, 324, 328 can 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 the new destination substrate, but with a different collection of microdevices aligned with site 120 . For example, the 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 FIG. 16 , some products may require multiple different types of microdevices 110i , 110j , 110k in each unit 205 . For example, for a color LED display, three tiny LEDs may be needed, one each for 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 simply be arranged in a single column or row. Or, for example, the subpixels within a cell can be arranged in a quincunx pattern, where two subpixels represent two colors, such as red and green, and a single subpixel of a third color, such as blue (this pattern Also known as PenTile matrix). The transfer technique can be used to form displays with sub-pixels of more than three colors, for example, displays with red, green, blue and yellow micro-LEDs.

Different colored LEDs can be LEDs with phosphor layers that emit different colored light, or they can be LEDs with different colored filter layers, or they can be LEDs that emit white light but also absorb white light and re-emit different colored light LEDs with superimposed phosphor materials (this material can be quantum dots).

Different microdevices, such as microLEDs of different colors, can be fabricated on different donor substrates at a higher spatial density than is required on the destination substrate. A transfer process can then be performed on each donor substrate. That is, microdevices 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 a 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 above discussion assumes that the donor substrate has microdevices that are properly aligned with the destination sites of each cell on the destination substrate (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., simultaneously exposing all corresponding areas of the adhesive layer).

However, it may be the case that the spacing between the microdevices on the donor substrate makes it impossible to transfer all the microdevices to the destination site 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, significant increases in manufacturing throughput are possible, at least compared to having to pick and place individual tiny devices. Referring to Figure 18, the modified process allows placement of the microdevices in a rectangular array with arbitrary spacing relative to the original spacing of the microdevices on the donor substrate.

Initially, microdevices 110 are 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. Then, the first transfer substrate 400a is positioned adjacent to the second surface of the second transfer device (eg, the second transfer substrate 400b). One row at a time is transferred, and between each transfer, the first transferred substrate is laterally repositioned to provide proper spacing in one of the directions, rather than transferring all microdevices at once. The microdevices are then transferred from the second transfer substrate to the destination substrate one column at a time, with the first transfer substrate being laterally repositioned between each transfer to provide proper spacing in the other direction.

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

Once the array of micro devices of M rows and N columns is transferred to the second transfer substrate 400 b, the micro devices 110 may be transferred to the destination substrate 200 . The second transfer substrate 400b is positioned adjacent to the second substrate 400b, and the lighting system is controlled to illuminate an area corresponding to M microdevices 110 within a single column. Thus, a single column containing M microdevices 110 will be transferred to the destination substrate 200 . Then, the second transfer substrate 400b moves along the Y-axis relative to the destination substrate 400b, and the lighting system is controlled to illuminate the area corresponding to another M microdevices 100 in another single column, thereby placing another column of M microdevices 100 equipment. This moving and placing process is repeated N−1 times until the micro devices in N columns and M rows are transferred to the destination substrate 200 . The amount of movement of the second transfer substrate 400 b relative to the destination substrate 200 is such that the pitch of the microdevices on the destination substrate 200 along the Y axis matches the desired pitch PY2 of the destination substrate 200 . Thus, the pitch of the microdevices on the destination substrate is now PX2 along the X axis and PY2 along the Y axis, 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 about M+N. While this M+N total may still be a large number for high-resolution displays, it is much smaller than the number of transfer steps M*N would require for pick and place alone.

In some embodiments, the microdevices are inspected or tested before being transferred to a destination substrate. Testing can be performed while the microdevice is still on the donor substrate, or it can be verified while the microdevice is on the transfer substrate. For each unit for which inspection or testing indicates that the microdevice is defective, the illumination system of the transfer system is controlled to not illuminate the area of the transfer substrate corresponding to the defective microdevice. Therefore, the identified defective microdevices are not transferred to the destination substrate. Any cells on the destination substrate that thus lack 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 (this may be before the first transfer substrate, after the second transfer substrate, or on the second transfer substrate). between a transfer substrate and a second transfer substrate) 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 sticky 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 such that the microdevices 110 adhere 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 such that it will remain tacky during subsequent illumination steps. For example, adhesive layer 112 may be a material that responds differently to exposure to two different wavelengths of light. Light at the first wavelength can neutralize the adhesive, eg, cure the material so that it is no longer tacky. In contrast, light at a second wavelength may induce chemical changes in the material such that the material is no longer sensitive to the first wavelength. For example, light 132 of the second wavelength may be directed through the donor substrate 110 from the backside of the donor substrate 110 to illuminate regions of the adhesive layer 112 . Light 132 may come from, for example, a laser scanning system or a digital micromirror device (DMD), such as the array shown in Figure 13D.

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

Alternatively or additionally, the treated region 112a may correspond to one or more microdevices 110c that are not part of the subset of microdevices 110 to be transferred. For example, this can be done to transfer microdevices positioned at certain pitches, or only certain columns or rows of microdevices.

Referring to FIG. 21 , the adhesive layer 112 is then illuminated to neutralize (eg, remove or denature) at least some portions of the untreated areas of the adhesive layer 112 . For example, light 134 at the first wavelength may be directed through the backside of the transfer substrate 100 . Such light 134 may illuminate both treated and untreated areas of the adhesive layer.

In some embodiments, the entire adhesive layer 112 is illuminated. In this case, light 134 may come from a generally wide-area collimated light source, such as a lamp with an appropriate lens. Alternatively, the light may illuminate selected areas. 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 the microdevice 110b and/or 110c remains adhesive. In contrast, other areas, such as the remainder of the adhesive layer 112, are neutralized.

The adhesive 112, 420 is chosen such that the treated area 112a of the adhesive layer 112 has a stronger adhesion to the microdevice than the adhesive layer 420. Therefore, as shown in FIG. 22 , when the donor substrate 100 and the transfer substrate 410 are separated, the microdevices 110 b and/or 110 c remain on the donor substrate 100 , while the remaining microdevices 110 d are transferred to the transfer substrate 410 .

Although FIGS. 19-22 illustrate each treated region 112a as a single patch, this is not required. The treated region 112a may span multiple microdevices 110b/c and portions of the adhesive layer 112 between adjacent microdevices 110b/c.

Referring to FIG. 23 , the treated region 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 make the treated areas of the adhesive layer 112 more adherent to the microdevices than the adhesive layer 420 .

Furthermore, referring to FIG. 24, the treated region 112a does not necessarily extend across the entire width of the microdevice 110b/c. For example, the treated region 112a may extend across only a portion of the surface area of the microdevice 110b/c. Likewise, treating the adhesive layer 112 across a certain percentage of the surface area of the microdevice may be sufficient to make the treated region 112a more strongly adhered to the microdevice than the adhesive layer 420 . The treated areas can be in the corners, or overlapping the edges, or in the center of the microdevice.

Returning to FIG. 23, in addition to or instead of desensitizing the adhesive, portion 112a of adhesive layer 112 may be treated to block (eg, absorb) light at the first wavelength. For example, adhesive layer 112 may include a material, such as a photoactivatable dye, that alters its absorption of a first wavelength in response to being illuminated by light of a second wavelength. In particular, adhesive layer 112 may be treated such that portion 112 extends partially, but not completely, through the thickness of adhesive layer 112 . Thus, the portion 112b of the adhesive layer between the treated portion 112a and the microdevice 110 will be less exposed to light of the first wavelength during subsequent illumination steps. Thus, compared with the adhesive layer 420, the portion 112b can maintain stronger adhesion to the micro-device.

Another technique to control which microdevices are transferred from the donor substrate to the transfer substrate or from the transfer substrate to the destination substrate is to modify the deposited masking layer on the backside of the appropriate substrate, such as the donor substrate, to block the light during the illumination step. Illumination of the corresponding area of the sticky layer. Figures 25-29 illustrate such a process.

As shown in FIG. 25 , masking layer 500 is selectively deposited onto the side of donor substrate 100 opposite adhesive layer 112 . The masking layer 500 is deposited at locations corresponding to the 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 such that the microdevices 110 adhere to the adhesive layer 420 on the transfer substrate 410 .

As shown in FIG. 27 , 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 . Masking layer 500 may be deposited by forming a layer across the entirety of donor substrate 100, followed by selective removal. For example, metal layers can be deposited by processes such as CVD and then removed by etching with a suitable photoresist. Alternatively, a positive or negative photoresist that blocks the wavelengths of light used in the illumination step can be deposited, eg, by spin coating. The photoresist layer may then be illuminated, eg, by a laser scanning system or a digital micromirror device (DMD) array, and developed to remove appropriate portions of the photoresist. Alternatively, masking layer 500 may be selectively deposited. For example, droplets of a material that is opaque to the wavelength of light used in the illuminating step can be jetted onto a selected area, for example by an inkjet printer.

As shown in FIG. 28 , light 138 may be directed through donor substrate 100 from the backside of donor substrate 110 to neutralize adhesive layer 112 . However, light 138 is blocked by masking layer 500 such that each corresponding region 112a is not (or is less exposed) exposed, thereby maintaining adhesion.

In some embodiments, the entire backside of the donor substrate 100 is illuminated. In this case, light 138 may come from a generally wide-area collimated light source, such as a lamp with an appropriate lens. Alternatively, the light may illuminate selected areas. In this case, light 138 may come from, for example, a laser scanning system or a digital micromirror device (DMD) array. In either case, masking regions 112a of the adhesive layer corresponding to mask 500 remain adhesive. In contrast, other areas, such as the remainder 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 microdevices 110b and/or 110c corresponding to the areas covered by the mask 500 remain on the donor substrate 100, while the remaining microdevices 110d is transferred to the transfer substrate 410 .

Although Figures 19-23 and Figures 25-29 illustrate transfer from a donor substrate to a transfer substrate, a similar process can be used to transfer microdevices from a transfer substrate to a destination substrate. In particular, in any of the embodiments discussed above, transfer substrate 410 and adhesive layer 420 may replace donor substrate 100 and adhesive layer 112 , respectively, and destination substrate 200 may replace transfer substrate 410 and 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 can be implemented with a digital electronic circuit system, or implemented with computer software, firmware, or hardware, or a combination thereof. The controller may include one or more computer program products, i.e. one or more computer programs, tangibly embodied in an information carrier, such as a non-transitory machine-readable storage medium or in a propagated signal, for processing by data A device (such as a programmable processor, computer, or multiple processors or computers) performs or controls its operations. A computer program (also known as a program, software, software application, or code) can be written in any form of programming language, including compiled or interpreted languages, and it can 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 can be deployed to execute on one computer or on multiple computers at one site or distributed across multiple sites and interconnected by a communication network.

The processes and logic flows described in this specification can be performed by one or more programmable processors executing one or more computer programs to perform operations on input data and Produces output to perform a function. These processes and logic flows can also be implemented by special purpose logic circuitry such as FPGA (Field Programmable Gate Array) or ASIC (Application Specific Integrated Circuit) and the device can also act as the special purpose logic circuitry to implement.

Positioning terms, such as vertical and lateral, have been used. However, it should be understood that such terms refer to relative positioning, rather than absolute positioning with respect to gravity. For example, lateral is a direction parallel to the substrate surface, and vertical is a direction normal to the substrate surface.

Those skilled in the art will appreciate that the foregoing examples are illustrative and not restrictive. It is contemplated that all permutations, enhancements, equivalents and improvements that would be apparent to those skilled in the art after reading the specification and studying the drawings are included within the true spirit and scope of this disclosure. Accordingly, it is contemplated that the following appended claims include all such modifications, permutations, and equivalents that fall within the true spirit and scope of these teachings.

100: Donor substrate 110:Micro Devices 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: Step 314: Step 316: Step 320: Step 324: step 328:Step 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: Illumination optics 538: Projection optics 550: device 552: pillar 554: Substrate 562:Actuator 580: Lighting system 582: light source 584:Digital Micromirror Device (DMD) 586: Illumination optics 588: Projection optics 600: system 610: the first support 630: transfer device 632: surface 650: controller 660: Actuator 110a: Micro Devices 110b: Micro Devices 110c: Micro Devices 110d: Micro Devices 110i: Micro Devices 110j: Micro Devices 110k: Micro Devices 112a: Area 112b: part 118b: area 400a: the first transfer substrate 400b: second transfer substrate 550a: Mirror 550b: Mirror PX1: Pitch PX2: Pitch PY1: Spacing PY2: Spacing

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

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

3 is a flowchart of a method 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 a plurality of microdevices from a donor substrate to a destination substrate.

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

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

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

Figure 13D 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 microdevices 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 cell.

Fig. 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 treatment extending partially through the thickness of the adhesive layer.

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

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

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

Similar reference characters in the various drawings indicate similar elements.

Domestic deposit information (please note in order of depositor, date, and number) none

Overseas storage information (please note in order of storage country, organization, date, and number) none

100: Donor substrate

110:Micro Devices

112: Adhesive layer

114: subject

134: light

410: Donor Substrate

420: Adhesive layer

630: transfer device

110b: Micro Devices

110c: Micro Devices

Claims (18)

A method of transferring microdevices, the method comprising the steps of: When a plurality of microdevices are attached to a first surface of a first body by a first adhesive layer, the first adhesive layer is selectively processed to form a treated portion of the adhesive layer and the first adhesive layer. an unprocessed portion of a layer, the processed portion corresponding to one or more microdevices from the plurality of microdevices; When the plurality of microdevices are attached to the first surface by the first adhesive layer, a second surface of a second body is positioned relative to the first surface such that a second adhesive layer on the second surface a layer adjoins the plurality of microdevices on a side of the plurality of microdevices opposite the first surface; exposing the first adhesive layer to light in an area overlapping at least some of the treated portion and at least some of the untreated portion, wherein exposing the first adhesive layer to light neutralizes the untreated the at least some of the parts to create a neutralized part that is less viscous than an exposed area of the treated part; 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 one corresponding to the neutralized portion One or more microdevices are attached to the second surface and detached from the first surface. The method of claim 1, wherein the light has a first wavelength. The method of claim 2, wherein selectively treating the first adhesive layer comprises the step of directing light of a different second wavelength onto the first adhesive layer. The method of claim 3, wherein directing light of the second wavelength onto the first adhesive layer comprises 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 3, wherein directing the light of the second wavelength through the first body comprises the step of: scanning a light beam with a laser scanning system. The method of claim 1, wherein exposing the first adhesive layer to light comprises the step of: exposing the first adhesive layer across an area spanning all of the plurality of microdevices. The method as recited in claim 1, wherein selectively treating the first adhesive layer comprises the step of simultaneously treating an area of the first adhesive layer corresponding to two or more adjacent microdevices. The method of claim 1, wherein selectively treating the first adhesive layer comprises the step of: treating an area of the first adhesive layer, the area being smaller than a cross-sectional area of a microdevice. The method of claim 1, wherein selectively treating the first adhesive layer comprises the step of: treating a portion that extends through the first adhesive layer to an extent less than the full thickness of the first adhesive layer. The method of claim 1, wherein the micro devices comprise micro LEDs. An apparatus for transferring microdevices, the apparatus comprising: A first body having a first surface for receiving a first adhesive layer; A second body has a second surface for receiving a second adhesive layer; one or more actuators configured to provide relative motion between the first body and the second body; a first lighting system configured to selectively expose the first adhesive layer to a light having a first wavelength; and a second illumination system configured to expose the first adhesive layer to a light having a second, different wavelength; and A controller, configured to: causing the one or more actuators to create relative motion such that a plurality of microdevices attached to the first body via the first adhesive layer come into contact with the second adhesive layer; causing the first illumination system to selectively expose the first adhesive layer to create a treated portion corresponding to one or more microdevices from the plurality of microdevices and one or more microdevices from the plurality of microdevices An unprocessed portion corresponding to the microdevice; causing the second lighting system to expose the first adhesive layer in an area that overlaps at least some of the treated portion and at least some of the untreated portion to create a neutralized portion while the treated portion at least some of which remain viscous; and causing the one or more actuators to create relative motion such that the first body and the second body move away from each other, the one or more microdevices corresponding to the treated portion of the first adhesive layer remain in contact with the second body A surface is attached, and one or more microdevices corresponding to the neutralizing portion are attached to the second surface and detached from the first surface. The apparatus of claim 11, wherein the first illumination system is configured to generate a light beam having a spot size smaller than a cross-sectional area of one of the microdevices. The apparatus of claim 11, wherein the first illumination system is configured to generate a light beam with a spot size spanning at least two microdevices. The apparatus of claim 11, wherein the first illumination system and the second illumination system are positioned to direct the light having the first wavelength and the light having the second wavelength through the first body to the second an adhesive layer. The apparatus of claim 11, wherein the second lighting system is configured to expose an area that spans all of the plurality of microdevices simultaneously. The device of claim 11, wherein the first body includes a first substrate, and the first substrate can be removed from a first support. The device of claim 11, wherein the second body includes a second substrate, and the second substrate can be removed from a second support. The device of claim 11, wherein the one or more actuators comprise a robotic arm operable to vertically move the first body relative to one of the first body or the second body or the other of the second subject.

Images