Patent ID: 12237443

Features and advantages of the present disclosure will become more apparent from the detailed description set forth below when taken in conjunction with the drawings, in which like reference characters identify corresponding elements throughout. In the drawings, like reference numbers generally indicate identical, functionally similar, and/or structurally similar elements. The figures are not necessarily drawn to scale. The vertical scale of the Figures can be exaggerated to clarify the illustrated structures.

DETAILED DESCRIPTION OF CERTAIN EMBODIMENTS

Electronic circuit performance and size (e.g., component spatial density) are important attributes of electronic systems. However, very small and dense electronic systems (micro-systems) are increasingly difficult and expensive to construct. Some micro-systems comprise micro-assembled micro-components from a variety of sources comprising a variety of materials disposed on a common substrate and electrically, optically, or electro-optically connected using photolithographic methods and materials. Such micro-systems have a desirably small footprint, e.g., a small area over a substrate or a substrate with a small area with densely packed micro-components. Micro-systems with even smaller micro-system areas can be provided by integrating a micro-component within a pocket in a micro-transfer-printed micro-device, e.g., a hole, pit, hollow, chamber, receptacle, or opening that extends through the micro-device. The micro-transfer-printed micro-device is separate from the micro-component and has a substrate distinct (e.g., separate, independent, individual) from the micro-component or a micro-component substrate. One or both of the micro-device and the micro-component can be micro-transfer printed. One or both of the micro-device and the micro-component can comprise a broken (e.g., fractured) or separated tether as a consequence of micro-transfer printing. Micro-transfer-printed micro-devices can be released from a source wafer with an etchant and can, but do not necessarily, comprise a thin etch-resistant insulating (e.g., dielectric) layer, for example ranging in thickness from a few nanometers to a few microns. Micro-components can be micro-transfer printed into a micro-device pocket that exposes the etch-resistant dielectric layer, thus reducing the thickness and area of the micro-system (as compared to stacking micro-component(s) on a micro-device). Micro-assembled micro-device(s) and micro-component(s) can be comprised in a micro-device structure that can be a micro-transfer printable or micro-transfer printed micro-system.

According to embodiments of the present disclosure and as illustrated inFIGS.1A-1C, a micro-device structure99comprises an insulating layer10and a micro-device20disposed on insulating layer10. Micro-device20comprises, has, or includes a pocket40formed in micro-device20that extends from a micro-device surface21(e.g., a side) of micro-device20opposite insulating layer10through micro-device20to insulating layer10, e.g., extends all of the way through micro-device20. A micro-component30is disposed in pocket40. Micro-component30can be disposed directly on a surface of insulating layer10or, as shown inFIG.1B, on an adhesive layer disposed on insulating layer10deposited, for example, with a spin, spray, or slot coater. Adhesive layer12can comprise a resin, polymer, or epoxy, for example a cured adhesive12(cured after disposing micro-component(s)30), can be transparent and have similar transparency as insulating layer10, and can adhere micro-component30to insulating layer10. In any case, either with or without adhesive layer12, and according to embodiments of the present disclosure, micro-component30is disposed on insulating layer10in pocket40. Pocket40can be formed by pattern-wise etching micro-device20with an etchant that differentially etches material of micro-device20and insulating layer10. Insulating layer can be an etch-stop layer. Pocket40can have substantially vertical sides with respect to micro-device surface21or can be substantially sloped (e.g., corresponding to an etch plane), depending on a material of micro-device20and the etchant.

Micro-component30can be non-native to micro-device20and/or to insulating layer10. Micro-component30can comprise one or more different materials than micro-device20. Micro-device20can comprise a micro-device substrate, micro-component30can comprise a micro-component substrate, and the micro-device substrate can be distinct (e.g., individual, separate, independent) from the micro-component substrate. Micro-device20can be native to and constructed on insulating layer10(e.g., can be constructed using photolithographic materials and methods in an epitaxial layer deposited on insulating layer10, for example by evaporation or sputtering). Micro-component30can be transferred (e.g., micro-transfer printed) from a component source wafer into pocket40. Micro-component30can comprise a broken (e.g., fractured) or separated micro-component tether32as a consequence of micro-transfer printing. Micro-component30can comprise a compound semiconductor material such as GaN, GaAs, or InP and micro-device20can comprise a semiconductor material such as silicon. Both micro-component and micro-device20can comprise a crystalline material such as a crystalline semiconductor material. Micro-device20can be or comprise a semiconductor-on-insulator device.

According to some embodiments, insulating layer10is transparent, for example substantially transparent or no less than 50%, 60%, 70%, 80%, 90%, or 95% transparent to desired wavelengths of electromagnetic radiation, such as visible light. Insulating layer can comprise an oxide, a nitride, silicon dioxide, silicon nitride, or combinations of layers of different oxides or nitrides, for example to control stress in insulating layer10. Insulating layer10can be differentially etchable from material comprising micro-device20.

In some embodiments and as shown inFIG.2, micro-component30is an electromagnetic-radiation-emitting or -receiving component, e.g., a light-emitting component such as an inorganic light-emitting diode or laser or a light-receiving component such as a photo-diode. Light34can be visible light or include ultraviolet or infrared electromagnetic radiation. The light-emitting or light-receiving micro-component can be disposed on insulating layer10in pocket40to emit light34through insulating layer10, for example as shown inFIG.2, or to receive light. Micro-component30can be electrically connected to micro-device20, e.g., through photolithographically defined wires.

In some embodiments, micro-component30is controllable by micro-device20. For example, micro-device20can comprise a micro-circuit22electrically connected to contact pads24of micro-device20that are electrically connected to electrodes26that are electrically connected to contact pads24of micro-component30. Micro-circuit22can be an integrated circuit formed using photolithographic methods and materials. Pocket40can be planarized after micro-component30is disposed in pocket40, for example with a dielectric material42, e.g., an organic material such as benzocyclobutene (BCB) or Intervia™ (from Rohm and Haas) spin, spray, or curtain coated over pocket40or an inorganic material such as silicon dioxide or silicon nitride evaporated or sputtered over pocket40. In any case, dielectric material42can be photolithographically defined to open contact pads24on micro-circuit22or micro-component30. Electrically conductive material (e.g., metal) can then be deposited and patterned using photolithographic methods and materials to form electrodes26(e.g., wires) that electrically connect micro-circuit22to micro-component30. Micro-circuit22can at least partially surround (e.g., fully or only partially surround) pocket40and therefore micro-component(s)30. For example, micro-circuit22can be formed on one side of pocket40.

As shown inFIG.3, and according to some embodiments of the present disclosure, more than one micro-component30is disposed in pocket40so that micro-device structure99comprises a plurality of micro-components30disposed in pocket40on insulating layer10that are non-native to micro-device20and non-native to insulating layer10. Micro-components30of the plurality of micro-components30can be identical or can be different and some or all can be disposed in pocket40by transfer printing, such as micro-transfer printing. Two or more of micro-components30in the plurality of micro-components30can be electrically connected together in pocket40. Two or more of micro-components in a plurality of micro-components30can be electrically connected to micro-circuit22of micro-device20, for example as described with respect toFIG.2. In some embodiments, micro-components30in the plurality of micro-components30comprise one or more red micro-LEDs30R operable to emit red light34R disposed in pocket40, one or more green micro-LEDs30G operable to emit green light34G disposed in pocket40, one or more blue micro-LEDs30B operable to emit blue light34B disposed in pocket40, or some combination thereof. Micro-device20can be or comprise a pixel controller electrically connected to red micro-LED(s)30R, green micro-LED(s)30G, and blue micro-LED(s)30B and the pixel controller and red micro-LED(s)30R, green micro-LED(s)30G, and blue micro-LED(s)30B can be comprised in a pixel, for example a display pixel or a single pixel that can emit a desired color of light.

Electronic micro-systems of the present disclosure can be constructed using micro-transfer printing. In some embodiments, micro-device system99, micro-device20, and micro-component30can each (e.g., all) have dimension(s) no greater than 1,000 μm. According to embodiments of the present disclosure, micro-device structure99has a length or width, or both, no greater than 1 mm, no greater than 750 μm, no greater than 500 μm, no greater than 200 μm, no greater than 100 μm, no greater than 50 μm, or no greater than 20 μm. Micro-device structure99can have a thickness no greater than 50 μm, no greater than 20 μm, or no greater than 10 μm. Micro-device structure99can be a micro-transferable with a micro-system tether56or a micro-transferred structure with a broken (e.g., fractured) or separate micro-system tether56, as shown inFIG.3. (For clarity, micro-system tethers56are not shown inFIGS.1A-2but can be present).

Similarly and according to embodiments of the present disclosure, micro-device can have one or more of: a length no greater than 1,000 μm (e.g., no greater than 750 μm, no greater than 500 μm, no greater than 200 μm, no greater than 100 μm, no greater than 50 μm, or no greater than 20 μm, or no greater than 10 μm), a width no greater than 1,000 μm (e.g., no greater than 750 μm, no greater than 500 μm, no greater than 200 μm, no greater than 100 μm, no greater than 50 μm, no greater than 20 μm, or no greater than μm), and a thickness no greater than 100 μm (e.g., no greater than 50 μm, no greater than 20 μm, no greater than 10 μm, or no greater than 5 μm).

In some embodiments, micro-component30can have one or more of: a length no greater than 50 μm (e.g., no greater than 20 μm, no greater than 10 μm, no greater than 5 μm, or no greater than 2 μm), a width no greater than 50 μm (e.g., no greater than 20 μm, no greater than 10 μm, no greater than 5 μm, or no greater than 2 μm), and a thickness no greater than 50 μm (e.g., no greater than 20 μm, no greater than 10 μm, no greater than 5 μm, no greater than 1 μm, or no greater than 1 μm).

Micro-device structure99can have a length or width, or both, greater than a length or width, or both, of micro-device20, respectfully. Micro-device20can have a length or width (or both a length and a width) greater than a length or width (or both) of micro-component30, respectfully. Pocket40can have a length or width (or both a length and a width) greater than a length or width (or both) of micro-component30and smaller than a length or width (or both a length and a width) of micro-device20, respectfully.

Micro-component30can have a thickness no greater than a thickness of micro-device20so that micro-component30is entirely within pocket40. Micro-component30can have a thickness greater than a thickness of micro-device20so that micro-component protrudes from pocket40in a direction opposite insulating layer10. Micro-component can have a thickness substantially equal to or within 10%, 20%, or 30% of a thickness of micro-device20so that micro-component30. Micro-component30can have a thickness no more than 30% (e.g., no greater than 20% or no greater than 10%) greater than a thickness micro-device20.

FIGS.4A-4JandFIGS.9A-9Bshow successive structures made according to the flow diagram ofFIG.5illustrating various embodiments of the present disclosure. Experienced practitioners of photolithographic techniques will understand that different processes and materials can be used to construct embodiments of the present disclosure and that claimed embodiments of the present disclosure are not limited to the specific examples presented herein.

As shown inFIG.5, a source wafer50, for example a semiconductor-on-insulator (SOI) source wafer50comprising an epitaxial layer53disposed on an insulating layer10disposed on a sacrificial layer52of a bulk semiconductor layer51, is provided in step100. SOI source wafer50can comprise a bulk semiconductor layer51a portion of which can be a sacrificial layer52. An insulating layer10is disposed over bulk semiconductor layer51and sacrificial layer52and an epitaxial layer53of semiconductor material disposed over insulating layer10. Micro-circuits22and contact pads24can be formed in epitaxial layer53in step110, for example using photolithographic methods and materials, as shown inFIG.4Afor example, and pattern-wise etched through epitaxial layer53to insulating layer10in step120, thereby exposing insulating layer10and forming micro-devices20and pockets40, as shown inFIG.4Bfor example. In some embodiments, SOI source wafer50is provided with exposed insulating layer10, pockets40, and micro-devices20already formed. In some embodiments, a small residual (e.g., discontinuous) amount of epitaxial layer53remains on insulating layer10when etching is complete such that when micro-component(s)30are disposed in pocket40on insulating layer10, some portion (or all) of the small residual amount of epitaxial layer53may be disposed between micro-component(s)30and insulating layer10. In some embodiments an adhesive layer12can adhere micro-component30to insulating layer10.

One or more micro-component(s)30are disposed in pocket40, for example by micro-transfer printing with a stamp60in step130, for example as shown inFIG.4C, to provide micro-device structure99, as shown inFIG.4D. Optionally, an adhesive layer12(shown inFIG.1B) is provided in pocket40before micro-component(s)30are disposed in pocket40and cured after micro-component(s)30are disposed in pocket40. Adhesive12can be spray- or spin-coated or inkjet printed as a liquid on epitaxial layer53and, after curing, exposed adhesive12(e.g., not covered by micro-component(s)30) can be removed if desired, for example by exposure to a plasma. After micro-transfer-printing micro-component(s)30into pocket40, the epitaxial layer53and pocket40with micro-component(s)30can be planarized to fill pocket40and provide a processing surface over micro-device20in step140. Electrodes26(e.g., wires) electrically connecting micro-component30to micro-device20(e.g., to micro-circuit22and contact pads24) can be patterned using photolithographic methods and materials (e.g., metal) in step150and as shown, for example, inFIG.4E.

Micro-device system99can itself be micro-transfer printed to a target substrate62. As shown inFIG.4F, SOI source wafer50can comprise a sacrificial layer52comprising sacrificial portions54spaced apart by anchors58. Micro-device structures99are disposed entirely above a sacrificial portion54and a micro-system tether56connects micro-device structure99to an anchor58. Sacrificial portions54are etched in step160to release micro-device system99from SOI source wafer50so that micro-device structure99is suspended by micro-system tether56over etched sacrificial portion54as shown inFIG.4G. Micro-device structure99can then be micro-transfer printed from SOI source wafer50(as shown inFIG.4H) to a target substrate62(as shown inFIG.4I) with a stamp60in step170, providing a micro-device structure99disposed on target substrate62as shown inFIG.4J.

Pocket40in epitaxial layer53and micro-device20can be rectangular or polygonal in horizontal cross section and can have sidewalls41extending from micro-device surface21to insulating layer10. In some embodiments, pocket40is completely surrounded by micro-device20, as shown inFIGS.1A-3, so that micro-device20completely surrounds micro-component30in a plane parallel to a surface of insulating layer10(e.g., the surface on which micro-component30is disposed or micro-device surface21). In some embodiments, pocket40is open so that pocket40is not completely surrounded by micro-device20in a plane parallel to a surface of insulating layer10, for example because pocket40has fewer than four sidewalls41. The perspective ofFIG.6Aand corresponding cross section ofFIG.6Billustrate a pocket40in micro-device20open on three sides with only one sidewall41and two micro-components30in pocket40. Micro-component(s)30are adjacent to (e.g., in contact with) the one sidewall41of pocket40in micro-device20. The perspective ofFIG.7Aand corresponding cross section ofFIG.7Billustrate a pocket40in micro-device20with two sidewalls41and one micro-component30in pocket40. Micro-component30is adjacent to (e.g., in contact with) both of the two sidewalls41of pocket40in micro-device20. The perspective ofFIG.8Aand corresponding cross section ofFIG.8Billustrate a pocket40in micro-device with three sidewalls41forming a U-shape around pocket40and one micro-component30in pocket40. Micro-component30can be contacted or adhered to one or more pocket40sidewalls41using micro-transfer printing. Contacting micro-component to a pocket40sidewalls41enables a very accurate positioning of micro-component with respect to micro-device20, for example to facilitate alignment. Accurate alignment can be important for opto-electronic structures such as light-emitters (LEDs, lasers), light-receivers (photodiodes), and light transmitters (fibers). When micro-component(s)30are contacted to sidewall(s)41, micro-component(s) can be finally disposed within 1 μm (e.g., within 500 nm or within 250 nm) of sidewall(s)41. Pockets that are open on a side can facilitate micro-transfer printing (e.g., by enabling horizontal stamp motion and stamp shear detachment as described in U.S. Pat. Nos. 10,714,374 and 10,937,679, the content of each of which is incorporated by reference herein in its entirety).

Embodiments of the present disclosure can be thinner and have a smaller area than micro-systems using an additional substrate on which micro-devices20and micro-components30are disposed. Furthermore, embodiments of the present disclosure can be more robust under mechanical and thermal stress since micro-device structure99can be more flexible and incorporate fewer and smaller components within a smaller, more flexible structure.

Micro-component30can be any structure, circuit, or system useful in combination with micro-device20, for example an electronic or opto-electronic device such as an active or passive integrated circuit, light-emitting diode, vertical cavity surface emitting laser (VCSEL), photodiode, or sensor. Micro-component30can comprise any one or more of a combination of semiconductor, conductive metals, or dielectric materials, such as inorganic oxides (e.g., silicon oxide), nitrides (e.g., silicon nitride), or organic materials such as resins or epoxies. In some embodiments, micro-component30can comprise a compound semiconductor, for example GaN, GaAs, InP, or other III/V or II/VI compound semiconductor materials. Micro-component30can be constructed using photolithographic methods and materials known in the art. Similarly, micro-device20can be any electronic or opto-electronic structure useful in combination with one or more micro-components30, for example an active or passive electronic or opto-electronic integrated circuit. Micro-device20can be a silicon integrated circuit. Micro-device20can control, respond to, or interact with micro-component(s)30.

Bulk semiconductor layer51can be constructed using methods known in the semiconductor art, for example using the Czochralski (CZ) method to form a single-crystal wafer, for example a silicon wafer, and can have any useful diameter or thickness, for example industry-standard wafer diameters such as 150, 200, or 300 mm, thickness such as 300-950 microns, or crystal orientation, such as <100>, <110> or <111>, and can have a polished back surface. Insulating layer10can be any useful substrate on or in which an epitaxial layer53can be disposed and micro-device20formed. Insulating layer can be a buried oxide (BOx) layer, for example a thermal oxide layer having a thickness in the range of 0.3 microns to 4 microns, typically 0.5 microns to 2 microns. Insulating layer10can be formed on a semiconductor wafer or other wafer, such as sapphire, for example by chemical vapor deposition (CVD) or plasma-enhanced CVD (PECVD). Insulating layer10can be or comprise silicon dioxide or silicon nitride, or both, for example to control insulating layer10stress. Insulating layer10can be differentially etchable, for example using tetramethylammonium hydroxide (TMAH) or potassium hydroxide (KOH), from bulk semiconductor layer51, epitaxial layer53, or both. Epitaxial layer53can comprise a same material as bulk semiconductor layer51, can be deposited by CVD or PECVD and, in some embodiments, can have a thickness in the range of 1 micron to 200 microns. Epitaxial layer53(and micro-device20) can be coated with an encapsulating or protective layer to enable bulk semiconductor layer51etching without etching epitaxial layer53or micro-device20. Bulk semiconductor layer51and epitaxial layer53can be or comprise doped or undoped crystalline silicon, for example having N-type dopants such as phosphorus or red phosphorus or P-type dopants such as boron.

Reference is made throughout the present description to examples of micro-transfer printing with stamp60when describing certain examples of printing micro-components30or micro-device structures99. Similar other embodiments are expressly contemplated where a transfer device60that is not a stamp60is used to similarly print micro-components30or micro-device structure99. For example, in some embodiments, a transfer device60that is a vacuum-based or electrostatic transfer device60can be used to print micro-components30or micro-device structure99. A vacuum-based or electrostatic transfer device60can comprise a plurality of transfer posts, each transfer post being constructed and arranged to pick up a single micro-component30or micro-device structure99.

According to some embodiments, micro-transfer printing can include any method of transferring micro-components30or micro-device structures99from a source substrate (e.g., a micro-component source wafer or semiconductor-on-insulator source wafer50) to a destination substrate or surface (e.g., insulating layer10for micro-components30or target substrate62for micro-device structure99) by contacting micro-components30or micro-device structure99on component source wafer or SOI source wafer50with a patterned or unpatterned stamp surface of a transfer device (e.g., stamp60) to remove micro-components30or micro-device structure99from the component source wafer or SOI source wafer50, transferring the transfer device (e.g., stamp60) and contacted micro-components30or micro-device structures99, and contacting micro-components30or micro-device structure99to a surface of insulating layer10or target substrate62. Micro-components30or micro-device structures99can be adhered to transfer device (e.g., stamp60), insulating layer10, or target substrate62by, for example, van der Waals forces, electrostatic forces, magnetic forces, chemical forces, adhesives, or any combination of the above. In some embodiments, micro-components30or micro-device structures99are adhered to a stamp60with separation-rate-dependent adhesion, for example kinetic control of viscoelastic stamp materials such as can be found in elastomeric transfer devices60such as a PDMS stamp60. Micro-transfer printing is a useful way to micro-assemble micro-device structure99because it can print micro-components30that are smaller than other prior components using prior assembly methods, such as pick-and-place. Thus, embodiments of the present disclosure enable smaller and spatially denser micro-device structures99and micro-systems.

Stamps60can be patterned or unpatterned and can comprise stamp posts having a stamp post area on the distal end of the stamp posts. The stamp posts can have a length, a width, or both a length and a width, similar or substantially equal to a length, a width, or both a length and a width of micro-components30or micro-device structures99. In some embodiments, the stamp posts can be smaller than micro-components30or micro-device structures99or have a dimension, such as a length and/or a width, substantially equal to or smaller than a length or a width of micro-components30or micro-device structures99in one or two orthogonal directions. In some embodiments, the stamp posts each have a contact surface of substantially identical area.

In exemplary methods, a viscoelastic elastomer (e.g., PDMS) stamp60(e.g., comprising a plurality of stamp posts) is constructed and arranged to retrieve and transfer micro-components30or micro-device structures99from their native micro-component source wafer or SOI source wafer50onto non-native insulating layer10or target substrate62. In some embodiments, stamp60mounts onto motion-plus-optics machinery (e.g., an opto-mechatronic motion platform) that can precisely control stamp60alignment and kinetics with respect to both component source wafers and SOI source wafer50and target substrate62. During micro-transfer printing, the motion platform brings stamp60into contact with micro-components30or micro-device structures99, with optical alignment performed before contact. Rapid upward movement of the print-head (or, in some embodiments, downward movement of the component source wafer or SOI source wafer50) breaks (e.g., fractures) or separates micro-component tether(s)32or micro-system tether56forming broken (e.g., fractured) or separated tethers, transferring micro-components30or micro-device structures99to stamp60. The populated stamp60then travels to SOI source wafer50(for micro-components30) or target substrate62(for micro-device structures99) and prints micro-components30or micro-device structures99.

Micro-components30disposed in and non-native to micro-device structure99can be constructed using integrated circuit, micro-electro-mechanical, or photolithographic methods and can comprise one or more different component materials, for example non-crystalline (e.g., amorphous), polycrystalline, or crystalline semiconductor materials such as silicon or compound semiconductor materials. Similarly, micro-devices20constructed in and native to epitaxial layer53and SOI source wafer50can be constructed using integrated circuit, micro-electro-mechanical, or photolithographic methods and can comprise one or more different component materials, for example non-crystalline (e.g., amorphous), polycrystalline, or crystalline semiconductor materials such as silicon or compound semiconductor materials.

In certain embodiments, micro-devices20can be native to and formed on insulating layer10over sacrificial portions54of SOI source wafers50and can include seed layers for constructing crystalline layers on or in SOI source wafers50. Micro-devices20, sacrificial portions54, anchors58, and micro-system tethers56can be constructed, for example using photolithographic processes. Micro-components30can each be an unpackaged die transferred from a component source wafer to insulating layer10. Micro-device structures99can be unpackaged dies (each an unpackaged die) transferred directly from native SOI source wafers50on or in which micro-device structures99are constructed to target substrate62.

Anchors58and micro-system tethers56can each be or can comprise portions of SOI source wafer50that are not sacrificial portions54and can include layers formed on micro-device structure99, for example dielectric or metal layers and for example layers formed as a part of photolithographic processes used to construct or encapsulate micro-device20and micro-components30.

Target substrate62can be any destination substrate or target substrate62to which micro-device structures99can be transferred (e.g., micro-transfer printed), for example flat-panel display substrates, printed circuit boards, or similar substrates comprising one or more of semiconductor, glass, polymer, quartz, ceramics, metal, and sapphire. Target substrate62can be or comprise a semiconductor substrate (for example silicon) or compound semiconductor substrate.

Patterned electrical conductors (e.g., wires, traces, or electrodes (e.g., electrical contact pads) such as those found on printed circuit boards, flat-panel display substrates, and in thin-film circuits) can be formed on any combination of micro-components30and micro-devices20, as well as insulating layer10, and any one can comprise electrodes26(e.g., electrical contact pads24) that electrically connect to micro-components30or micro-devices20. Such patterned electrical conductors and electrodes26(e.g., contact pads24) can comprise, for example, metal, transparent conductive oxides, or cured conductive inks and can be constructed using photolithographic methods and materials, for example metals such as aluminum, gold, or silver deposited by evaporation and patterned using pattern-wise exposed, cured, and etched photoresists, or constructed using imprinting methods and materials or inkjet printers and materials, for example comprising cured conductive inks deposited on a surface or provided in micro-channels, or both.

Adhesive12can be a curable or cured adhesive12. Adhesive12can be an uncured adhesive12that is subsequently cured. Uncured adhesive12can be deposited on insulating layer10as a liquid, and optionally on micro-device20or SOI substrate50, for example by laminating, coating, inkjet printing, or spraying adhesive12. Adhesive12can be a soft-cured adhesive12, for example an adhesive12from which at least some, a majority, or a substantial majority of solvents or other volatile materials are evaporated or otherwise removed or driven out from uncured adhesive12that is still relatively malleable, compliant, or conformable compared to a hard-cured adhesive12and can be shaped or otherwise deformed by pressing against the soft-cured adhesive12, for example with a micro-component30. An uncured or soft-cured adhesive12can be hard cured by, for example, by heating or exposure to electromagnetic radiation that renders adhesive12a cured, relatively rigid, non-compliant, non-conformable, and solid adhesive12with substantially reduced stickiness or adhesion compared to uncured or soft-cured adhesive12. Thus, in some embodiments, adhesive12can be completely uncured, soft-cured, or hard-cured at various stages of constructing printed micro-device structures99of the present disclosure. A layer of soft-cured (e.g., partially cured) adhesive12can be patterned, for example by photolithographic processing using masks to expose the layer of uncured adhesive12and removing either the exposed or unexposed adhesive12to form a patterned layer of soft-cured adhesive12on insulating layer10. According to embodiments of the present disclosure, adhesive12can comprise an organic material, a polymer, a resin, or an epoxy. According to some embodiments, adhesive12is a photoresist.

Examples of micro-transfer printing processes suitable for disposing micro-components30onto insulated layers10or micro-device structures99onto target substrates62are described in Inorganic light-emitting diode displays using micro-transfer printing (Journal of the Society for Information Display, 2017, DOI #10.1002/jsid.610, 1071-0922/17/2510-0610, pages 589-609), U.S. Pat. No. 8,722,458 entitled Optical Systems Fabricated by Printing-Based Assembly, U.S. patent application Ser. No. 15/461,703 entitled Pressure-Activated Electrical Interconnection by Micro-Transfer Printing, U.S. Pat. No. 8,889,485 entitled Methods for Surface Attachment of Flipped Active Components, U.S. patent application Ser. No. 14/822,864 entitled Chiplets with Connection Posts, U.S. patent application Ser. No. 14/743,788 entitled Micro-Assembled LED Displays and Lighting Elements, and U.S. patent application Ser. No. 15/373,865, entitled Micro-Transfer Printable LED Component, the disclosure of each of which is incorporated herein by reference in its entirety. Examples of micro-transfer printed acoustic wave filter devices are described in U.S. patent application Ser. No. 15/047,250, entitled Micro-Transfer Printed Acoustic Wave Filter Device, the disclosure of which is incorporated herein by reference in its entirety.

For a discussion of various micro-transfer printing techniques, see also U.S. Pat. Nos. 7,622,367 and 8,506,867, each of which is hereby incorporated by reference in its entirety. Micro-transfer printing using compound micro-assembly structures and methods can also be used in certain embodiments, for example, as described in U.S. patent application Ser. No. 14/822,868, filed Aug. 10, 2015, entitled Compound Micro-Assembly Strategies and Devices, which is hereby also incorporated by reference in its entirety.

Various embodiments of structures and methods were described herein. Structures and methods were variously described as transferring, printing, or micro-transfer printing micro-components30and micro-device structures99. Micro-transfer-printing involves using a transfer device (e.g., an elastomeric stamp60, such as a PDMS stamp) to transfer a micro-component30or micro-device structure99using controlled adhesion. For example, an exemplary transfer device60can use kinetic or shear-assisted control of adhesion between a transfer device60and a micro-component30or micro-device structure99. It is contemplated that, in certain embodiments, where a method is described as including micro-transfer-printing a micro-component30or micro-device structure99, other analogous embodiments exist using a different transfer method. As used herein, transferring a micro-component30or micro-device structure99can be accomplished using any one or more of a variety of known techniques. For example, in certain embodiments, a pick-and-place method can be used. As another example, in certain embodiments, a flip-chip method can be used (e.g., involving an intermediate, handle or carrier substrate). In methods according to certain embodiments, a vacuum tool or other transfer device is used to transfer a micro-component30or micro-device structure99.

The foregoing disclosure has been described with reference to illustrative embodiments where micro-component(s)30are disposed in a single pocket40in micro-device20. Analogous embodiments are contemplated where one or more micro-component(s)30are disposed in each of two or more pockets40in a single micro-device20. For example, a red micro-LED30R, green micro-LED30G, and blue micro-LED30B can each be separately disposed in a respective pocket40in micro-device20.

As is understood by those skilled in the art, the terms “over” and “under” are relative terms and can be interchanged in reference to different orientations of the layers, elements, and substrates included in various embodiments of the present disclosure. Furthermore, a first layer or first element “on” a second layer or second element, respectively, is a relative orientation of the first layer or first element to the second layer or second element, respectively, that does not preclude additional layers being disposed therebetween. For example, a first layer on a second layer, in some implementations, means a first layer directly on and in contact with a second layer. In other implementations, a first layer on a second layer includes a first layer and a second layer with another layer therebetween (e.g., and in mutual contact).

Throughout the description, where apparatus and systems are described as having, including, or comprising specific elements, or where processes and methods are described as having, including, or comprising specific steps, it is contemplated that, additionally, there are apparatus and systems of the disclosed technology that consist essentially of, or consist of, the recited elements, and that there are processes and methods according to the disclosed technology that consist essentially of, or consist of, the recited processing steps.

It should be understood that the order of steps or order for performing certain action is immaterial so long as the disclosed technology remains operable. Moreover, two or more steps or actions in some circumstances can be conducted simultaneously.

Having described certain implementations of embodiments, it will now become apparent to one of skill in the art that other implementations incorporating the concepts of the disclosure may be used. The disclosure has been described in detail with particular reference to certain embodiments thereof, but it will be understood that variations and modifications can be effected within the spirit and scope of the following claims.

PARTS LIST

A cross section line10insulating layer12adhesive layer/adhesive/layer of adhesive20micro-device21micro-device surface22micro-circuit24contact pad26electrode30micro-component/micro-LED30R red micro-LED30G green micro-LED30B blue micro-LED32micro-component tether34light34R red light34G green light34B blue light40pocket41sidewall42dielectric material/dielectric structure50semiconductor-on-insulator source wafer/SOI source wafer51bulk semiconductor layer52sacrificial layer53epitaxial layer54sacrificial portion56micro-system tether58anchor60stamp/transfer device62target substrate99micro-device structure100provide source wafer step110form micro-device step120etch pocket step130print component into pocket step140fill pocket step150form electrodes step160release structure from source wafer step170print structure to target substrate step