Integrated platform for micro devices

Abstract

This disclosure relates to a system for placing microdevices, including a backplane and microdevices. Furthermore, the use of conductive or ohmic contact layers, transparent layers, and reflective layers is discussed. This disclosure also discloses a method for integrating microdevices into a system substrate. Specifically, the transfer of microdevices using a system substrate employing a hollow adhesive pad is discussed.

Description

Cross-references to related applications

[0001] This application claims the benefits and priority of 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 herein by reference in their entirety. Technical Field

[0002] This disclosure relates to integrating circuits and systems into a microdevice substrate. This disclosure also relates to integrating microdevices into a system substrate. Summary of the Invention

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

[0004] The present invention relates to a method for integrating a microdevice, the method comprising: providing a system substrate having circuitry, connectors, and pads capable of being connected to the microdevice; forming a bonding agent on the system substrate, wherein at least a portion of the bonding agent overlaps with a first pad on the system substrate; aligning the microdevice with the system substrate, wherein a second pad partially overlaps with the bonding agent; and bonding the microdevice to the bonding agent and leaving it on the system substrate. Attached Figure Description

[0005] The foregoing and other advantages of this disclosure will become apparent after reading the following detailed description and after referring to the accompanying drawings.

[0006] Figure 1A An optoelectronic system is shown, which includes microdevices transferred into a system substrate using a hollow pad.

[0007] Figure 1B An optoelectronic system is shown, in which microdevices transferred into the system substrate are covered by a planarization layer.

[0008] Figure 1C An opening is shown that is formed on top of a microdevice in a planarization layer, and a conductive layer is coupled to the microdevice through the opening.

[0009] Figure 1D Another substrate is shown, either bonded or formed on top of the backplate.

[0010] Figure 1E The original system substrate that can be removed is shown.

[0011] Figure 1F The conductive material in the opening region is shown, which couples the device to a backplane formed on the substrate.

[0012] Figure 2 A bonding agent for an integration platform for microdevices is shown.

[0013] While this disclosure is susceptible to various modifications and alternatives, specific embodiments or particular implementations have been illustrated by way of example in the accompanying drawings and will be described in detail herein. However, it should be understood that this disclosure is not intended to limit it to the specific forms disclosed. Rather, this disclosure will cover all modifications, equivalents, and alternatives that fall within the spirit and scope of the invention as defined by the appended claims. Detailed Implementation

[0014] The following invention discloses methods, systems, and device structures.

[0015] With the increasing demand for high-resolution displays, sensors, and microelectronic systems, efficient methods for integrating microdevices onto substrates have become crucial. Conventional transfer processes often involve adhesive bonding, where microdevices are placed on a backplane using patterned adhesive pads. However, for microdevices smaller than 20 μm, patterning and etching adhesive polymers to fabricate electrical interconnects is challenging. If not performed precisely, this can lead to dark spot defects in optoelectronic devices, preventing pixels from emitting light.

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

[0017] In one embodiment, a microdevice is transferred to a designated location on a pre-patterned adhesive pad on a backplane. The semiconductor portion of the microdevice contacts non-conductive bumps to prevent direct electrical connection. To achieve conductivity, openings are patterned and etched on the bottom or back of the bumps. Following this, metal electrodes are deposited to establish electrical paths for device operation.

[0018] To address the challenge of etching reliability for microdevices smaller than 20 μm, an improved method was introduced in which the binder polymer is pre-patterned into rings prior to microdevice transfer. This ensures selective contact of the microdevice with the backplane, thereby avoiding extensive polymer adhesion. Consequently, metal can be directly deposited onto the semiconductor without the need for complex etching of the binder.

[0019] In one implementation, the polymer material used for adhesive bonding is photodeterminable and can be structured via photolithography. In another approach, a standard etching process is used to fabricate a ring-shaped adhesive pattern. These techniques ensure high transfer accuracy and reliability, thereby reducing defects in the final system.

[0020] This invention relates to integrating circuits and systems into microdevice substrates. Microdevice substrates may include miniature light-emitting diodes (LEDs), organic LEDs, sensors, solid-state devices, integrated circuits, microelectromechanical systems (MEMS) and / or other electronic components.

[0021] Microdevices are transferred to a backplane via adhesive bonding. Selective transfer to the backplane is achieved by transferring only the device to locations on a patterned adhesive pad. In this adhesive bonding method, the bottom semiconductor contacts a non-conductive bump. To drive current through the device after transfer, openings need to be patterned and etched on the bottom / back of the bumps. Following these openings, metal electrodes can be attached to the semiconductor.

[0022] In the case of microdevices smaller than 20 micrometers, the patterning and etching of the binder polymer can be unreliable and requires extensive characterization and testing. If not done correctly, the microdevice optoelectronic system may have numerous dark spot defects, such as pixels not emitting light.

[0023] One solution to the problem of creating reliable openings is to pattern polymer bumps into rings before microdevice transfer. By doing so, microdevices can be selectively transferred onto the backplane, and the semiconductor does not come into contact with the polymer everywhere. After processing, metal can be deposited directly onto the semiconductor without any polymer etching. In one embodiment, the polymer can be a photodeterminable binder, and the rings are patterned by photolithography. In a second embodiment, the polymer can be etched to create the ring pattern.

[0024] The foregoing and other advantages of this disclosure will become apparent after reading the following detailed description and after referring to the accompanying drawings.

[0025] Integrating microdevices into system substrates can lead to breakthroughs in delivering life-changing products. These microdevices can include miniature LEDs, miniature sensors, miniature solar cells, miniature AI, and nanodevices. As these devices become smaller, mechanical and electrical bonding becomes more challenging.

[0026] One embodiment involves an adhesive that provides electrical and mechanical bonding in a region. Here, the adhesive substrate is impregnated with at least two materials. These materials can be nanoparticles, such as nanowires, nanodots, sheets, etc. In one related embodiment, the embedded material is conductive, while the adhesive material is non-conductive. In one example, the two materials may form an alloy upon contact.

[0027] In one related embodiment, one material may be silver nanowires or silver sheets. The second material in the related embodiment may be nanoparticles, tin nanoparticles, or similar soft metals.

[0028] In one related implementation, heat or pressure can accelerate the bonding between the two materials during the bonding process.

[0029] In one related implementation, photopolymerization accelerates the bonding of microdevices to a bonding agent.

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

[0031] In related embodiments, the adhesive can be light-defined and can be patterned using photolithography. In related embodiments, an etching (wet or dry) process is used to pattern the adhesive layer.

[0032] Figure 1A An optoelectronic system (100) is illustrated in which a microdevice is transferred onto a system substrate using a hollow adhesive pad. The microdevice includes a functional semiconductor structure (102) having a conductive or ohmic contact layer (104) formed on top. A transparent protective layer (108-a) is applied, which is separated from the device by reflective layers (106-a, 106-b). A passivation layer (110) encapsulates the functional structure (102) for protection.

[0033] On the opposite side, a second protective layer (108-b) is applied, which is separated from the structure (102) by another reflective layer (106). The system substrate (120) includes an adhesive pad (110) having openings (112) that facilitate electrical connections. The passivation layer is characterized by additional openings (124) at the top or bottom of the structure for further connections. The adhesive pad (110) can be cured after transfer to hold the microdevice in place. The system substrate (120) may also incorporate a release layer (120) and a protective layer (122), with an additional intermediate layer between the substrate and the adhesive pad (110) to enhance mechanical and electrical properties. In related embodiments, conductive bumps can be used to form the protective layers (108-a and 108-b) to enable direct electrical interfaces between the microdevice and the backplane.

[0034] Figure 1A A photoelectric system 100 is shown, comprising a microdevice transferred into a system substrate using a hollow pad. The microdevice includes a functional structure 102. A conductive or ohmic layer 104 may be formed on top of layer 102. A protective layer 108-a may be formed on top of the surface. This protective layer may be separated from the device by reflective layers 106-a and 106-b. A passivation layer 110 may be formed around structure 102. On the other side, another protective layer 108-b may be formed, which may be separated from structure 102 by another layer 106. Protective layers 108-a and 108-b may be transparent. Pad 110 may be formed on a system substrate 120. The pad 110 has an opening 112 within it. The passivation layer may have an opening at the top or bottom of structure 124.

[0035] Pad 110 may be an adhesive. The pad can be cured after the microdevice is transferred onto the top of the pad. System substrate 120 may have a release layer 120 and a protective layer 122. Other layers may be present between the substrate and pad 110.

[0036] In the relevant implementation scheme, protective layers 108-a and 108-b are conductive bumps.

[0037] Figure 1B A photoelectric system 100 is shown, wherein microdevices transferred into a system substrate are covered by a planarization layer 126. Openings are formed using openings 130 on the top of the microdevices in the planarization layer 126, and a conductive layer 128 is coupled to the microdevices (e.g., ...) through the openings 130. Figure 1C (As shown). Backplane circuitry 132 may be formed on top of passivation layer 126. The backplane may be a combination of metal traces, capacitors, transistors, or other components. Backplane 132 may have pixel circuitry assigned to each microdevice 150. Another substrate 134 may be bonded or formed on top of backplane 132. Figure 1D ).

[0038] Removable original system substrate 120 ( Figure 1E A protective layer 136 may be formed on a surface, where the opening of the protective layer is located at the same position as the aperture in the pad. A conductive layer 138 may be formed to couple to the microdevice through the aperture. Backplane circuitry and electrodes 132 may also be formed on the side of the structure having the conductive layer 138. Here, the conductive layer 138 may be part of the backplane layer.

[0039] exist Figure 1FIn one related embodiment, the opening region 112 may contain a conductive material 220 that couples the device 102 to a backplane formed on the substrate 120. Here, layers 224 and 222 may be buffer layers, passivation layers, pixel circuitry, and / or electrodes. Here, another electrode 128 may be used to connect a second side / contact of the microdevice to the backplane. If a planarization layer 126 is used, an opening in the planarization can be formed to connect the electrode 128 to the backplane. In another related embodiment, the top electrode may be a common electrode that is not directly connected to the backplane.

[0040] Integrating micro-LEDs into the back panel

[0041] Figure 2 An example of an integration platform for microdevices is shown. Here, system substrate 200 has circuitry, connectors, and pads 202 connectable to microdevice 210. Here, a bonding agent is formed on system substrate 200, wherein at least a portion of the bonding agent overlaps with pads 202 on the substrate. Here, microdevice 210 is aligned with the system substrate, and microdevice pads 212 partially overlap with bonding agent 204. Microdevice 210 is bonded to the bonding agent and remains on the system substrate.

[0042] In one related embodiment, the bonding agent is cured by transferring the microdevices into the system substrate. In another related embodiment, complete curing is performed after the microdevices are integrated into the substrate.

[0043] One transfer method involves patterning a bonding agent 204 comprising an adhesive and at least two different conductive particles 206, 208 on the surface of a system substrate 200. A microdevice 210 is aligned with a pad 202 and the adhesive 204. The microdevice is then transferred into the system substrate by various means, wherein a microdevice pad 212 is in partial contact with the bonding agent 204.

[0044] During or after the transfer, pressure and temperature can cure the adhesive 104 and activate the electrical connections. The conductive particles in the adhesive can react to form an alloy, creating a more permanent bond.

[0045] While this disclosure is susceptible to various modifications and alternatives, specific embodiments or particular implementations have been illustrated by way of example in the accompanying drawings and will be described in detail herein. However, it should be understood that this disclosure is not intended to limit it to the specific forms disclosed. Rather, this disclosure will cover all modifications, equivalents, and alternatives falling within the spirit and scope of the invention as defined by the appended claims.

Claims

1. A method for integrating microdevices, the method comprising: A system substrate is provided, the system substrate having circuitry, connectors, and pads capable of being connected to the microdevice; An adhesive is formed on the system substrate, wherein at least a portion of the adhesive overlaps with a first pad on the system substrate; The microdevice is aligned with the system substrate, and the second pad partially overlaps with the bonding agent; as well as The microdevices are bonded to the bonding agent and remain on the system substrate.

2. The method of claim 1, wherein the bonding agent is cured by transferring the microdevice into the system substrate.

3. The method of claim 1, wherein complete curing is performed after the microdevice is integrated into the system substrate.

4. The method of claim 1, wherein the transfer method involves patterning the adhesive, which consists of an adhesive and at least two different conductive particles, on the surface of the system substrate.

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

6. The method of claim 5, wherein the microdevice is transferred into the system substrate by various means, wherein the microdevice pad is in partial contact with the bonding agent.

7. The method of claim 6, wherein during or after the transfer, pressure and temperature cure the adhesive and activate the electrical connection.

8. The method of claim 6, wherein the conductive particles in the adhesive react to form an alloy, thereby establishing a more permanent bond.

9. A method for integrating micro-LEDs into a backplane of an optoelectronic system, the method comprising: A conductive or ohmic layer is formed on top of the layer, and a protective layer is formed on top of the surface; The protective layer is separated from the microdevice by a reflective layer; The microdevice is transferred to a system substrate covered by a planarization layer; The pad is fabricated by stacking layers on a system substrate; as well as The pad is recycled after the microdevices are transferred onto the top of the pad.

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

11. The method of claim 9, wherein the system substrate comprises an adhesive pad having openings that facilitate electrical connections.

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