Microplating for integration of micro devices into system substrate

Abstract

The present invention discloses a method and a system in a microdevice transfer setup. In particular it describes, where the micro devices are on a donor substrate with bonding pads and micro bonding plates. In addition, it describes when there is a system substrate including traces, driving system, bonding pads and micro bonding plate. Further use of electroplating and an electrochemically assisted bonding process is discussed.

Description

Atorney Docket Number: 075913-000067WOPTMICROPLATING FOR INTEGRATION OF MICRO DEVICES INTO SYSTEM SUBSTRATECross-Reference to Related Applications

[0001] This application claims the benefit of, and priority to, U.S. Provisional Patent Application No. 63 / 738,023 filed December 23, 2024, which is hereby incorporated by reference herein in its entirety.Field of the Invention

[0002] The present disclosure relates to the integration of micro devices into system substrates. A microdevice transfer and bonding system is discussed.Summary

[0003] The present invention relates to a method to develop bonding pads for integration of micro devices into system substrates comprising, having the system substrate including traces, driving system, first bonding pads and micro bonding plates, having a micro device transfer set including a donor substrate with microdevices landing area, including the system substrate with micro devices landing area with second bonding pads and a donor substrate during the micro device transfer process, having a temporary electrolyte microplate part of the system substrate or other layers on the system substrate or micro devices landing area and applying a potential on either pads and the microplate on either system substrate or donor substrate which results in forming the bonding between the pads on the micro device and landing area on system substrate.

[0004] The present invention also relates to a method for bonding micro devices to a system substrate, comprising, providing a donor substrate having one or more micro devices, providing a system substrate having corresponding microdevice landing areas, positioning the donor substrate and the system substrate in opposing relation with a spacing structure disposed there between, the spacing structure defining a separation distance between the donor substrate and the system substrate flexing at least one of the donor substrate or the system substrate to equalize the separation distance across a bonding region and forming an electrical and mechanical bond between the micro devices and the system substrate.

[0005] The present invention also relates to a microdevice transfer and bonding system, comprising, a donor substrate carrying one or more micro devices, a system substrate having landing areas corresponding to the micro devices, a spacing structure configured to maintain a predetermined distance between the donor substrate and the system substrate and a pressure-14926-9187-4948.1075913-000067WOPTAtorney Docket Number: 075913-000067WOPTapplication structure configured to flex at least one of the donor substrate or the system substrate to promote bonding between the micro devices and the system substrate.Brief Description of the Drawings

[0006] The foregoing and other advantages of the disclosure will become apparent upon reading the following detailed description and upon reference to the drawings.

[0007] FIG 1A shows a micro device transfer set that includes a donor substrate with micro devices.

[0008] FIG IB shows a micro device transfer set that includes a system substrate with microdevices landing area.

[0009] FIG 1C shows a micro device transfer process that includes a system substrate with micro devices landing area and a donor substrate with micro devices.

[0010] While the present disclosure is susceptible to various modifications and alternative forms, specific embodiments or implementations have been shown by way of example in the drawings and will be described in detail herein. It should be understood, however, that the disclosure is not intended to be limited to the particular forms disclosed. Rather, the disclosure is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of an invention as defined by the appended claims.Detailed Description

[0011] The present invention describes a method and a system in a microdevice transfer setup. In particular it describes, where the micro devices are on a donor substrate with bonding pads and micro bonding plates. In addition, it describes when there is a system substrate including traces, driving system, bonding pads and micro bonding plate. In particular, the following methods with their variations and system are discussed.

[0012] The present invention relates to a method to develop bonding pads for integration of micro devices into system substrates comprising, having the system substrate including traces, driving system, first bonding pads and micro bonding plates, having a micro device transfer set including a donor substrate with microdevices landing area, including the system substrate with micro devices landing area with second bonding pads and a donor substrate during the micro device transfer process, having a temporary electrolyte microplate part of the system substrate or other layers on the system substrate or micro devices landing area and applying a potential on either pads and the microplate on either system substrate or donor substrate which results in forming the bonding between the pads on the micro device and landing area on system substrate.24926-9187-4948.1075913-000067WOPTAtorney Docket Number: 075913-000067WOPT

[0013] The present invention also relates to a method for bonding micro devices to a system substrate, comprising, providing a donor substrate having one or more micro devices, providing a system substrate having corresponding microdevice landing areas, positioning the donor substrate and the system substrate in opposing relation with a spacing structure disposed there between, the spacing structure defining a separation distance between the donor substrate and the system substrate flexing at least one of the donor substrate or the system substrate to equalize the separation distance across a bonding region and forming an electrical and mechanical bond between the micro devices and the system substrate.

[0014] The present invention also relates to a microdevice transfer and bonding system, comprising, a donor substrate carrying one or more micro devices, a system substrate having landing areas corresponding to the micro devices, a spacing structure configured to maintain a predetermined distance between the donor substrate and the system substrate and a pressureapplication structure configured to flex at least one of the donor substrate or the system substrate to promote bonding between the micro devices and the system substrate.

[0015] The present invention relates to a few embodiments of this description related to integration of micro devices into the system substrate. The system substrate may comprise micro light emitting diodes (LEDs), Organic LEDs, sensors, solid state devices, integrated circuits, (micro-electro-mechanical systems) MEMS, and / or other electronic components. Other embodiments are related to patterning and placing of micro devices in respect to the pixel arrays to optimize the micro device utilizations in selective transfer processes. The receiving substrate may be, but is not limited to, a printed circuit board (PCB), thin film transistor backplane, integrated circuit substrate, or, in one case of optical micro devices such as LEDs, a component of a display, for example a driving circuitry backplane. The patterning of micro device donor substrate and receiver substrate can be used in combination with different transfer technology including but not limited to pick and place with different mechanisms (e.g. electrostatic transfer head, elastomer transfer head), or direct transfer mechanism such as dual function pads and more.

[0016] Developing a few micrometer or smaller bonding pads on large areas for integration of micro devices into a system substrate is challenging. A different bonding process requires materials that are not compatible with a large area, expensive, or have no reliable bonding or no electrical connection. This embodiment is to develop reliable electrical bonding on large substrates with lower cost head, elastomer transfer head, or direct transfer mechanism such as dual function pads and more.

[0017] In one embodiment, the micro devices are on a donor substrate with bonding pads and 34926-9187-4948.1075913-000067WOPTAtorney Docket Number: 075913-000067WOPTmicro bonding plates.

[0018] In another embodiment, there is a system substrate including traces, driving system, bonding pads and micro bonding plate.

[0019] Developing a few micrometer or smaller bonding pads on large areas for integration of micro devices into a system substrate is challenging. A different bonding process requires materials that are not compatible with a large area, are expensive, or have no reliable bonding or no electrical connection. This embodiment is to develop reliable electrical bonding on large substrates with lower cost.

[0020] In one embodiment, the micro devices are on a donor substrate with bonding pads and micro bonding plates.

[0021] In another embodiment, there is a system substrate including traces, driving system, bonding pads and micro bonding plate.

[0022] A micro device could have different contacts on either side, and only the side facing the system substrate is bonded to the substrate directly.

[0023] FIG 1 A shows a micro device transfer set 100 including a donor substrate 102 with micro devices 104a, and 104b. The micro devices 104a, 104b can have bonding pads 106-a, and 106-b. Also, there can be a temporary electrolyte microplate 108. The microplate 108 can be part of the donor substrate or other layers on the donor substrate or micro devices.

[0024] FIG IB shows a micro device transfer set 120 includes a system substrate 122 with microdevices landing area 124a, 124b. The micro devices landing area 124a, 124b can have bonding pads 126-a, 126-b. Also, there can be a temporary electrolyte microplate 108. The microplate 108 can be part of the system substrate or other layers on the system substrate or micro devices landing area.

[0025] FIG 1C shows a micro device transfer process 130 includes a system substrate 122 with micro devices landing areas 124a, and 124b and a donor substrate 102 with micro devices 104a, 104b. The pads 106-a and 106-b for a selected micro device 104a is aligned with the pads 126a and 126b on a landing area 124a on system substrate 122. The pads get either in contact or in close proximity. There is an electrolyte 132 around (or between the pads) the pads. The electrolyte 132 can be a gel type or liquid. Applying a potential on either pads and the microplate on either system substrate or donor substrate can result in forming a joint between the pads on the micro device and landing area on system substrate.

[0026] The electrolyte can be inkjet or spray printed on either substrates or it can be transferred to the donor substrate with a wetting process or stamping process.

[0027] FIG. 1A illustrates a microdevice transfer set (100) comprising a donor substrate (102)44926-9187-4948.1075913-000067WOPTAtorney Docket Number: 075913-000067WOPTon which a plurality of micro devices (104a, 104b) is formed, fabricated, or temporarily mounted. The donor substrate (102) may be a semiconductor wafer, glass substrate, polymer substrate, or any other suitable carrier used during microdevice fabrication or intermediate handling.

[0028] Each micro device (104a, 104b) includes one or more bonding pads (106-a, 106-b) configured to provide electrical and / or mechanical connection to a corresponding system substrate during transfer. The bonding pads may be formed of conductive materials such as copper, aluminum, nickel, gold, or multilayer metal stacks, and may be passivated or exposed depending on the process flow.

[0029] In one embodiment, a temporary electrolyte microplate (108) is associated with the donor substrate (102), the micro devices (104a, 104b), or an intermediate layer disposed therebetween. The microplate (108) may be a thin electrolyte layer, gel, liquid, or solid-state ionic medium capable of supporting electrochemical reactions when an electrical potential is applied. The electrolyte microplate may be patterned, selectively deposited, or globally applied depending on the desired bonding configuration.

[0030] The donor substrate may further include release layers, sacrificial layers, or weak adhesion interfaces (not explicitly shown) to facilitate separation of the micro devices from the donor substrate following bonding to the system substrate.

[0031] FIG. IB illustrates a system substrate transfer set (120) comprising a system substrate (122) configured to receive an electrical interface with micro devices transferred from the donor substrate.

[0032] The system substrate (122) may include, but is not limited to, a printed circuit board (PCB), thin-film transistor (TFT) backplane, CMOS backplane, interposer, or integrated circuit substrate. The system substrate includes one or more microdevice landing areas (124a, 124b), each landing area being spatially arranged to correspond to the intended placement of a micro device.

[0033] Each landing area (124a, 124b) includes one or more bonding pads (126-a, 126-b) that are electrically connected to traces, driving circuitry, or other functional elements of the system substrate. The bonding pads are positioned to align with the bonding pads of the micro devices during transfer.

[0034] Similar to the donor substrate, a temporary electrolyte microplate (108) may be formed on or integrated with the system substrate (122), the landing areas (124a, 124b), or an intermediate layer. In some embodiments, the electrolyte microplate is present only on the system substrate; in other embodiments, it is present only on the donor substrate; and in yet 54926-9187-4948.1075913-000067WOPTAtorney Docket Number: 075913-000067WOPTother embodiments, electrolyte material is present on both substrates.

[0035] FIG. 1C illustrates a microdevice transfer and bonding process (130) in which the donor substrate (102) and the system substrate (122) are brought into alignment and proximity.

[0036] During this process, a selected micro device (104a) on the donor substrate is aligned such that its bonding pads (106-a, 106-b) correspond to and face the bonding pads (126-a, 126-b) of a landing area (124a) on the system substrate. Alignment may be achieved using optical, mechanical, or electrostatic alignment techniques, and the pads may be brought into direct contact or maintained at a controlled separation distance.

[0037] An electrolyte region (132) is present at or around the interface between the bonding pads. The electrolyte region may originate from the electrolyte microplate (108) on either substrate and may be delivered by inkjet printing, spray coating, wetting, stamping, or other deposition methods.

[0038] Once alignment is achieved, an electrical potential is applied between selected bonding pads and the electrolyte microplate, either through the donor substrate, the system substrate, or both. The applied potential induces an electrochemical reaction within the electrolyte region (132), resulting in localized micro-plating or electrochemical joint formation between the bonding pads of the micro device and the bonding pads of the system substrate.

[0039] This electrochemically assisted bonding process forms a mechanically robust and electrically conductive joint without requiring high temperature reflow, solder materials, or external bonding pressure. Following bond formation, the micro device (104a) may be released from the donor substrate (102), leaving it permanently integrated with the system substrate (122).

[0040] In another related embodiment, the spacer structure (108) is configured to define, control, and maintain a predetermined separation distance between the donor substrate (102) and the system substrate (122) during the microdevice transfer and bonding process.

[0041] In this embodiment, element (108) functions as a mechanical spacing element that prevents unintended collapse, tilt, or non-uniform gap formation between the two substrates during alignment and bonding. The controlled separation distance ensures uniform electrochemical conditions, consistent current density, and reliable bonding across the microdevice pads.

[0042] The spacing defined by element (108) may range from nanometers to several micrometers, depending on microdevice size, pad geometry, electrolyte composition, and desired bonding characteristics.

[0043] In this embodiment, either or both of the donor substrate (102) and the system substrate 64926-9187-4948.1075913-000067WOPTAtorney Docket Number: 075913-000067WOPT(122) are configured to exhibit controlled mechanical flexibility. The flexibility may be inherent to the substrate material (e.g., thin glass, polymer, silicon thinned to a predefined thickness) or may be enabled through structural design, such as localized thinning, trenches, or compliant layers.

[0044] The controlled flexibility allows the donor substrate and / or system substrate to locally deform toward or away from each other so that the separation distance defined by element (108) is substantially uniform across the bonding region. This self-leveling behavior compensates for, substrate bow or warp, local topography variations, thickness non-uniformities, and alignment tolerances.

[0045] As a result, micro devices (104a, 104b) can be bonded to the system substrate (122) with high uniformity, even over large-area substrates.

[0046] In this related embodiment, bonding materials may be located, exclusively on the micro device bonding pads (106-a, 106-b), exclusively on the system substrate bonding pads (126-a, 126-b), or distributed on both the donor-side pads and system-side pads.

[0047] The bonding materials may include electroplatable metals, metal alloys, or multilayer stacks configured to grow, merge, or interlock during electrochemical bonding induced by the applied electrical potential.

[0048] In another related embodiment, a diaphragm structure is used to apply pressure to either the donor substrate (102), the system substrate (122), or both during alignment and bonding.

[0049] The diaphragm may be pneumatically, hydraulically, mechanically, or electrostatically actuated and applies to a distributed, substantially uniform pressure across the substrate surface. This pressure causes controlled bending or flexing of the substrate, allowing the substrate to conform to the spacing defined by element (108).

[0050] The diaphragm-based pressure application, improves pad-to-pad proximity, stabilizes the electrolyte region, enhances electrochemical bonding kinetics, and reduces localized bonding failures.

[0051] In another related embodiment, the structure applying pressure to the donor substrate or system substrate includes a flexible or compliant surface layer. The flexible surface may comprise materials such as, polymers, elastomers, graphite, composite materials, or layered compliant films.

[0052] The flexible surface distributes pressure evenly while allowing localized deformation of the underlying substrate. This configuration enables adaptive conformal contact without inducing excessive mechanical stress, cracking, or particle generation.

[0053] The flexible pressure-application structure may be used alone or in combination with the 74926-9187-4948.1075913-000067WOPTAtorney Docket Number: 075913-000067WOPTdiaphragm to further enhance bonding uniformity and yield.

[0054] While particular embodiments and applications of the present invention have been illustrated and described, it is to be understood that the invention is not limited to the precise construction and compositions disclosed herein and that various modifications, changes, and variations can be apparent from the foregoing descriptions without departing from the spirit and scope of the invention as defined in the appended claims.84926-9187-4948.1075913-000067WQPT

Claims

Atorney Docket Number: 075913-000067WOPTCLAIMS1. A method to develop bonding pads for integration of micro devices into system substrates comprising:having the system substrate including traces, driving system, first bonding pads and micro bonding plates;having a micro device transfer set including a donor substrate with microdevices landing area;including the system substrate with micro devices landing area with second bonding pads and a donor substrate during the micro device transfer process;having a temporary electrolyte microplate part of the system substrate or other layers on the system substrate or micro devices landing area;andapplying a potential on either pads and the microplate on either system substrate or donor substrate which results in forming the bonding between the pads on the micro device and landing area on system substrate.

2. The method of claim 1, wherein the first bonding pads with a selected micro device are aligned with the second boding pads on a landing area on system substrate.

3. The method of claim 1, wherein here is an electrolyte around or between the pads and wherein the electrolyte is a gel type or liquid.

4. The method of claim 3, wherein the electrolyte is an inkjet or spray printed on either substrates or it is transferred to the donor substrate with a wetting process or a stamping process.

5. The method of claim 1, wherein the donor substrate is a semiconductor wafer, glass substrate, polymer substrate, or any carrier used during microdevice fabrication or intermediate handling.

6. The method of claim 1, wherein the first bonding pads are configured to provide electrical and / or mechanical connection to a corresponding system substrate during transfer and are be formed of conductive materials such as copper, aluminum, nickel,94926-9187-4948.1075913-000067WOPTAtorney Docket Number: 075913-000067WOPTgold, or multilayer metal stacks, and are passivated or exposed depending on a process flow.

7. The method of claim 1, wherein the microplate is a thin electrolyte layer, gel, liquid, or solid-state ionic medium capable of supporting electrochemical reactions when an electrical potential is applied and is patterned, selectively deposited, or globally applied depending on the desired bonding configuration.

8. The method of claim 1, wherein the donor substrate further includes release layers, sacrificial layers, or weak adhesion interfaces to facilitate separation of the micro devices from the donor substrate following bonding to the system substrate.

9. The method of claim 1, wherein the system substrate includes one or more microdevice landing areas wherein each landing area being spatially arranged to correspond to the intended placement of a micro device.

10. The method of claim 1, wherein the electrolyte microplate is present only on the system substrate; in other embodiments, it is present only on the donor substrate; and in yet other embodiments, electrolyte material is present on both substrates.

11. The method of claim 2, wherein the alignment is achieved using optical, mechanical, or electrostatic alignment techniques, and the pads are brought into direct contact or maintained at a controlled separation distance.

12. The method of claim 11, wherein the applied potential induces an electrochemical reaction within the electrolyte region, resulting in localized micro-plating or electrochemical joint formation between the bonding pads of the micro device and the bonding pads of the system substrate.

13. The method of claim 12, wherein an electrochemically assisted bonding process forms a mechanically robust and electrically conductive joint without requiring high temperature reflow, solder materials, or external bonding pressure.104926-9187-4948.1075913-000067WOPTAtorney Docket Number: 075913-000067WOPT14. The method of claim 13, wherein following bond formation, the micro device is released from the donor substrate leaving it permanently integrated with the system substrate.

15. A method for bonding micro devices to a system substrate, comprising:providing a donor substrate having one or more micro devices;providing a system substrate having corresponding microdevice landing areas; positioning the donor substrate and the system substrate in opposing relation with a spacing structure disposed there between, the spacing structure defining a separation distance between the donor substrate and the system substrate;flexing at least one of the donor substrate or the system substrate to equalize the separation distance across a bonding region; andforming an electrical and mechanical bond between the micro devices and the system substrate.

16. A microdevice transfer and bonding system, comprising:a donor substrate carrying one or more micro devices;a system substrate having landing areas corresponding to the micro devices;a spacing structure configured to maintain a predetermined distance between the donor substrate and the system substrate; anda pressure-application structure configured to flex at least one of the donor substrate or the system substrate to promote bonding between the micro devices and the system substrate.

17. The method of claim 15, wherein the spacing structure comprises an electrolytecontaining microplate.

18. The method of claim 15, wherein the separation distance is maintained within a micrometer-scale tolerance.

19. The method of claim 15, wherein bonding materials are disposed on the micro devices, the system substrate, or both.114926-9187-4948.1075913-000067WOPTAtorney Docket Number: 075913-000067WOPT20. The system of claim 16, wherein the pressure-application structure comprises a diaphragm.

21. The system of claim 20, wherein the diaphragm is pneumatically or hydraulically actuated.

22. The system of claim 16, wherein the pressure-application structure includes a flexible surface.

23. The system of claim 22, wherein the flexible surface comprises a polymer, elastomer, or graphite material.

24. The method of claim 15, wherein flexing compensates for substrate bow or thickness variation.

25. The system of claim 16, wherein both the donor substrate and the system substrate are configured to flex.124926-9187-4948.1075913-000067WOPT

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