Integration platform for microdevices

Abstract

This disclosure is related to arranging a system comprising of backplane and microdevices. In addition, use of conductive or ohmic contact layer, transparent layer and a reflective layer is discussed. The present also discloses a method of integrating microdevices into a system substrate. In particular, transfer of microdevices using a system substrate using hollow adhesive pads is discussed.

Description

INTEGRATION PLATFORM FOR MICRODEVICESCross-Reference to Related Applications

[0001] The present application claims the benefit of and priority to and U.S. Provisional Application No. 63 / 691,872, filed September 6, 2024, and U.S. Provisional Application No. 63 / 550,576, filed February 6, 2024, the contents of which are incorporated by reference herein in their entireties.Field of the invention

[0002] The present disclosure relates to the Integration of circuits and systems into a microdevice substrate. The present disclosure also relates to integrating microdevices into a system substrateSummary

[0003] The present invention relates method of integrating a MicroLED into a backplane of an optoelectronic system comprising, forming a conductive or ohmic layer on the top of the layer and a protective layer on top of the surface, separating the protective layer from the microdevice by a reflective layer; transferring the microdevice into a system substrate is covered by a planarization layer, creating a pad by stacking a layers on system substrate; and recovering the pad after transferring microdevices on the top of the pad.

[0004] The present invention relates to a method to integrate microdevices the method comprising, having a system substrate with circuitries, connections, and pads connectable to the microdevices, forming a bonding agent on the system substrate, where at least part of it overlaps with a first pad on the system substrate, aligning the microdevice with the system substrate, and a second pad overlaps partially with the bonding agent, and bonding microdevices into the bonding agent and left on the system substrate.Brief description of the Drawings

[0005] The foregoing and other advantages of the disclosure will become apparent upon reading the following detailed description and upon reference to the drawings.

[0006] Figure 1A shows an optoelectronic system includes a transferred microdevice into a system substrate using hollow pads.

[0007] Figure IB shows an optoelectronic system where the transferred microdevice into a system substrate is covered by a planarization layer.

[0008] Figure 1C shows an opening is formed with an opening on top of the microdevice in the planarization layer and a conductive layer is coupled to the microdevice through the opening.

[0009] Figure ID shows another substrate bonded or formed on the top of the backplane.

[0010] Figure IE shows the original system substrate which can be removed.

[0011] Figure IF shows conductive materials in the opening area that couple devices to the backplane formed on substrate.

[0012] Figure 2 shows a bonding agent for integration platform for microdevices.

[0013] 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

[0014] The following inventions disclose methods, system and device structures.

[0015] As demand for high-resolution displays, sensors, and microelectronic systems increases, efficient methods for integrating microdevices onto substrates become critical. Conventional transfer processes often involve adhesive bonding, where microdevices are placed onto backplanes using patterned adhesive pads. However, for microdevices smaller than 20 pm, patterning and etching of the adhesive polymer to create electrical interconnects is challenging. If not executed precisely, this can lead to dark defects in optoelectronic devices, where pixels fail to emit light.

[0016] This invention presents an advanced technique for selectively transferring microdevices onto system substrates via patterned adhesive bonding. The core innovation lies in the precise formation of electrical interconnects using patterned polymer structures, which facilitate robust electrical contact while maintaining high device reliability.

[0017] In one embodiment, microdevices are transferred to designated locations on a backplane where patterned adhesive pads are pre-formed. The semiconductor portion of the microdevice contacts a non-conductive bump, preventing direct electrical connection. To enable electrical conductivity, openings are patterned and etched at the bottom or back of the bump. Following this, metal electrodes are deposited, establishing electrical pathways for device operation.

[0018] To address challenges in etching reliability for microdevices smaller than 20 pm, an improved approach is introduced wherein the adhesive polymer is pre-patterned into a ring before microdevice transfer. This ensures that the microdevice contacts the backplane selectively, avoiding widespread polymer adhesion. As a result, the metal can be deposited directly onto the semiconductor without requiring complex etching of the adhesive.

[0019] In one implementation, the polymer material used for adhesive bonding is photodefinable and can be structured via lithography. In another approach, standard etching processes are employed to create the ring-shaped adhesive pattern. These techniques ensure a high degree of transfer accuracy and reliability, thereby reducing defects in the final system.

[0020] The present invention relates to integration of circuits and systems in microdevice substrates. The microdevice 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.

[0021] Microdevices are transferred onto the backplane via adhesive bonding. Devices are only transferred to locations where there is a patterned adhesive pad, which enables selective transfer onto the backplane. In this method of adhesive bonding, the bottom semiconductor is contacting a non-conductive bump. In order to drive current through the device after transfer, openings will need to be patterned and etched at the bottom / back of the bump. After this opening, metal electrodes can be connected to the semiconductor.

[0022] In the case of microdevices smaller than 20 micrometers, the patterning and etching of the adhesive polymer can be unreliable and needs extensive characterization and testing. If not done properly, then the microdevice optoelectronic system could potentially have a significant number of dark defects where the pixel does not emit light.

[0023] One solution to this problem of making reliable openings is to pattern the polymer bump into a ring prior to microdevice transfer. By doing so, the microdevice can be transferred onto the backplane selectively and the semiconductor does not contact the polymer everywhere. After processing, metal could be deposited directly onto the semiconductor without any polymer etching. In one embodiment, this polymer could be photo definable adhesive, and the ring is patterned by lithography. In a second embodiment, this polymer can be etched to create this ring pattern.

[0024] The foregoing and other advantages of the disclosure will become apparent upon reading the following detailed description and upon reference to the drawings.

[0025] Integrating microdevices into the system substrate can create a breakthrough in offering life-changing products. These microdevices can be microLED, microSensors, microSolar,microAI, and nanodevices etc. As these devices become smaller, the mechanical and electrical bonding becomes challenging.

[0026] One embodiment is related to a bonding agent that offers electrical and mechanical bonding in one area. Here, an adhesive base is impregnated with at least two materials. These materials can be nanoparticles, for example, nanowires, nanodots, flacks, etc. In one related embodiment, the embedded materials are conductive, and the adhesive material is not conductive. In one example, the two materials can form alloys when in contact.

[0027] In one related embodiment, one material can be a silver nanowire or silver flack. The second material in a related embodiment can be nanoparticles, Tin nanoparticles, or similar soft metals.

[0028] In one related embodiment, the thermal or pressure can accelerate the connection between two materials during the bonding.

[0029] In one related embodiment, light curing accelerates bonding the microdevices into the bonding agent.

[0030] In one related embodiment, the pads on the system substrate can be modified to enhance the bonding between two materials or adhesive layers.

[0031] In a related embodiment, the adhesive agent can be photo-definable and patterned using photolithography. The adhesive layer is patterned in a related embodiment using an etching (wet or dry) process.

[0032] FIG. 1 A illustrates an optoelectronic system (100) in which a microdevice is transferred onto a system substrate using hollow adhesive pads. The microdevice comprises of a functional semiconductor structure (102), with a conductive or ohmic contact layer (104) formed on top. A protective transparent layer (108-a) is applied, separated from the device by a reflective layer (106-a, 106-b). A passivation layer (110) encapsulates the functional structure (102) for protection.

[0033] On the opposing side, a second protective layer (108-b) is applied, separated from the structure (102) by another reflective layer (106). The system substrate (120) includes adhesive pads (110) with an opening (112) that facilitates electrical connections. The passivation layer features additional openings (124) at the top or bottom of the structure for further connectivity. The adhesive pad (110) can be cured post-transfer to secure the microdevices in place. The system substrate (120) may also incorporate a release layer (120) and a protection layer (122), with additional intermediate layers between the substrate and adhesive pads (110) to enhance mechanical and electrical performance. In a related embodiment, the protective layers (108-a and 108-b) can be formed using conductive bumps, which enable direct electrical interfacingbetween the microdevice and the backplane.

[0034] FIG. 1A shows an optoelectronic system 100 includes a transferred microdevice into a system substrate using hollow pads. The microdevice includes a functional structure 102. A conductive or ohmic layer 104 can be formed on top of layer 102. A protective layer 108-a can be formed on top of the surface. The protective layer can be separated from the device by a reflective layer 106-a and 106-b. A passivation layer 110 can be formed around the structure 102. At the other side, another protective layer 108-b can be formed, and the protective layer can be separated from the structure 102 by another layer 106. The protective layers 108-a 108- b can be transparent. A pad 110 can be formed on the system substrate 120. The pad has an opening 112 in pad 110. The passivation layer can have openings at the top or bottom of structure 124.

[0035] The pad 110 can be adhesive. The pad can be cured after microdevices are transferred on top of the pad. The system substrate 120 can have a release layer 120 and a protection layer 122. There can be other layers between the substrate and the pads 110.

[0036] In a related embodiment, the protective layers 108-a and 108-b are conductive bumps.

[0037] FIG. IB shows an optoelectronic system 100 where the transferred microdevice into a system substrate is covered by a planarization layer 126. An opening is formed with an opening 130 on top of the microdevice in the planarization layer 126 and a conductive layer 128 is coupled to the microdevice through the opening 130 (as shown in FIG 1C). A backplane circuit 132 can form on top of the passivation layer 126. The backplane can be a combination of metal traces, capacitors, transistors or other components. The backplane 132 can have a pixel circuit allocated to each microdevice 150. There can be another substrate 134 bonded or formed on the top of backplane 132 (FIG ID).

[0038] The original system substrate 120 can be removed (FIG IE). A protective layer 136 can be formed on the surface where it has an opening at the same place as the hollow in the pads. A conductive layer 138 is formed to couple to the microdevice through the hollow. The backplane circuits and electrodes 132 can also be formed on the side of the structure with conductive layer 138. Here, the conductive 138 can be part of the backplane layers.

[0039] In one related embodiment shown in Figure IF, there can be conductive materials 220 in the opening area 112 that couple devices 102 to the backplane formed on substrate 120. Here layers 224, 222 can be buffer layer, passivation, pixel circuits and / or electrodes. Here, another electrode 128 can be used to connect the second side / contacts of the microdevice to the backplane. If a planarization layer 126 is used an opening in planarization may be formed to connect the electrode 128 to the backplane. In another related embodiment, the top electrodecan be a common electrode and not connected to the backplane directly.INTEGRATION OF MICROLEDS INTO BACKPLANE

[0040] Figure 2 shows an example of an integration platform for microdevices. Here, a system substrate 200 has circuitries, connections, and pads 202 that can be connected to microdevices 210. Here, a bonding agent is formed on system substrate 200, where at least part of it overlaps with pad 202 on the substrate. Here, microdevice 210 is aligned with the system substrate, and microdevice pad 212 overlaps partially with the bonding agent 204. The microdevices 210 are bonded into the bonding agent and left on the system substrate.

[0041] In one related embodiment, the bonding agents are cured by transferring microdevices into the system substrate. In another related embodiment, full curing is done after microdevices are integrated into the substrate.

[0042] One transfer method is to pattern a bonding agent 204 comprising of adhesive and at least two different conductive particles 206, 208 on the surface of a system substrate 200. A microdevice 210 is aligned with pads 202 and adhesive agent 204. The microdevice is transferred into the system substrate by different means where the microdevice pads 212 are in contact with part of the bonding agent 204.

[0043] During or after the transfer, pressure and temperature may cure the bonding agent 104 and activate the electrical connections. The conductive particles in the adhesive may react to form an alloy to create more permanent connections.

[0044] 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 the invention as defined by the appended claims.

Claims

CLAIMS1. A method to integrate microdevices the method comprising: having a system substrate with circuitries, connections, and pads connectable to the microdevices; forming a bonding agent on the system substrate, where at least part of it overlaps with a first pad on the system substrate; aligning the microdevice with the system substrate, and a second pad overlaps partially with the bonding agent; and bonding microdevices into the bonding agent and left on the system substrate.

2. The method of claim 1, wherein bonding agents are cured by transferring the microdevices into the system substrate.

3. The method of claim 1, wherein a full curing is done after the microdevices are integrated into the system substrate.

4. The method of claim 1, wherein a transfer method is to pattern the bonding agent consisting of adhesive and at least two different conductive particles on a surface of the system substrate.

5. The method of claim 4, wherein the microdevice is aligned with the first pads and an adhesive agent.

6. The method of claim 5, wherein the microdevice is transferred into the system substrate by different means where the microdevice pads are in contact with part of the bonding agent.

7. The method of claim 6, wherein during or after the transfer, a pressure and a temperature cures the bonding agent and activates electrical connections.

8. The method of claim 6, wherein conductive particles in the adhesive agent reacts to form an alloy to create more permanent connections.

9. A method of integrating a MicroLED into a backplane of an optoelectronic system comprising: forming a conductive or ohmic layer on the top of the layer and a protective layer on top of the surface; separating the protective layer from the microdevice by a reflective layer; transferring the microdevice into a system substrate is covered by a planarization layer; creating a pad by stacking a layer on system substrate; and recovering the pad after transferring microdevices on the top of the pad.

10. The method of claim 9, wherein on an opposing side, a second protective layer is applied, separated from the microdevice structure by another reflective layer.

11. The method of claim 9, wherein the system substrate includes adhesive pads with an opening that facilitates electrical connections.

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