A Micro LED device based on wafer-level packaging and its fabrication method
By setting up coating channels on Micro LED wafers and combining the use of infrared lasers, hot melt adhesives, and UV adhesives, the problems of batch transfer and color shift of Micro LED devices have been solved, enabling the fabrication of efficient, waterproof, and oxidation-resistant Micro LED devices.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- E SURFING IOT CO LTD
- Filing Date
- 2022-12-27
- Publication Date
- 2026-07-03
AI Technical Summary
In the existing fabrication process of Micro LED devices, batch transfer is difficult, and traditional wafer-level packaging cannot achieve chip-level or micron-level packaging, resulting in devices lacking water and oxygen resistance, and RGB chip integration is prone to color shift.
By employing chip-level and micron-level coating processes to create coating channels on the wafer, dividing it into independent units, and sealing it through multiple coating steps, combined with the use of infrared lasers, hot melt adhesives, and UV adhesives, the fabrication of Micro LED devices can be completed in a single process, including bonding to the CMOS substrate, bonding of quantum dot films and CF filters.
This technology enables waterproof and oxidation-resistant Micro LED devices, avoids color shift caused by secondary packaging and RGB chip integration, simplifies the process, and improves production efficiency and device performance.
Smart Images
Figure CN115939289B_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of emerging information technology, and in particular to a Micro LED device based on wafer-level packaging and its fabrication method. Background Technology
[0002] Micro LED display technology refers to a display technology that uses self-emissive, micrometer-sized LEDs as light-emitting pixel units, assembling them onto a driving panel to form a high-density LED array. Micro LEDs can be applied to high-resolution displays and visible light communication. Compared to traditional display technologies, Micro LED displays offer higher power efficiency and resolution, making them more suitable for applications in VR and wearable devices. Compared to traditional visible light communication devices, color Micro LEDs can increase bandwidth.
[0003] The key step in the current fabrication process of Micro LED devices is the mass transfer of chips. However, due to the extremely small size of Micro LEDs, the number of chips on a single wafer is very large, making it difficult to achieve low-cost, high-efficiency mass transfer. Therefore, mass transfer has become one of the bottlenecks restricting the commercialization of Micro LEDs. Meanwhile, one technical route for full-color Micro LEDs is to integrate RGB chips together. However, because different color chips are made of different materials, their light decay is also different. Therefore, directly fabricating the three primary color Micro LED chips together can easily cause color shift, which is detrimental to display and visible light communication.
[0004] Wafer-level packaging can solve the problem of batch transfer to some extent, but traditional Micro LED wafer-level packaging cannot achieve the process of completing Micro LED device fabrication immediately after dicing, based on the free combination design of Micro LED devices. It still requires secondary packaging, resulting in a certain degree of process complexity. The key issue is that it is impossible to achieve chip-level or micron-level packaging directly on the Micro LED wafer, resulting in devices lacking water and oxygen resistance. Therefore, subsequent processes must be performed after dicing. Among these, traditional dispensing and coating methods are difficult to apply encapsulating adhesive at the chip level, adding to the process difficulty. Summary of the Invention
[0005] The technical problem to be solved by the present invention is to address the deficiencies and defects mentioned in the background art, and to provide a MicroLED device based on wafer-level packaging and its fabrication method.
[0006] To address the above problems, the present invention proposes the following technical solution:
[0007] In a first aspect, the present invention provides a method for fabricating a MicroLED device based on wafer-level packaging, comprising the following steps:
[0008] S1. A coating channel is formed on the chip side of the MicroLED wafer and a glass material is coated into the coating channel; the coating channel divides the MicroLED wafer into at least two independent units;
[0009] S2. Flip-chip bond the MicroLED wafer obtained in S1 to the CMOS substrate.
[0010] S3. Thin the substrate of the bonded MicroLED wafer;
[0011] S4. Irradiate the glass material through the MicroLED wafer substrate using an infrared laser;
[0012] S5. Apply hot melt adhesive to the surface of the MicroLED wafer substrate and bond it to the quantum dot film;
[0013] S6. Apply hot melt adhesive to the quantum dot film and bond it to the CF (color filter);
[0014] S7. Apply UV adhesive to the CF and attach it to the glass cover plate for sealing;
[0015] S8. Laser cut the packaged wafer to obtain MicroLED devices.
[0016] A further technical solution is that the adhesive coating channel is a chip-sized, micron-sized sealed adhesive coating channel with a width of 10-30 microns.
[0017] Understandably, each of the individual units is surrounded by adhesive channels so that the resulting Micro LED device after cutting is waterproof and oxygen-proof.
[0018] A further technical solution is that step S1 specifically includes: coating a photosensitive adhesive on a MicroLED wafer;
[0019] The photomask has a pattern pre-set on it for forming the adhesive coating path. The photomask is placed on the MicroLED wafer coated with photosensitive adhesive.
[0020] Development exposes the corresponding coating paths on the MicroLED wafer;
[0021] Coating glass frit onto MicroLED wafers;
[0022] After coating, preheating is performed to allow the glass frit to initially solidify on the MicroLED wafer;
[0023] After removing the photosensitive adhesive, only the glass material on the adhesive coating path remains on the MicroLED wafer.
[0024] A further technical solution is that each of the independent units is provided with a cutting channel along the outer side of the adhesive coating channel, and the cutting channel is used for laser cutting in step S8. Specifically, the cutting channel is located 1-3 micrometers outside the adhesive coating channel, where "outer side" is relative to the independent unit surrounded by the adhesive coating channel.
[0025] A further technical solution is that, in steps S5-S6, the hot melt adhesive coating position corresponds to the position of the adhesive application channel.
[0026] Specifically, in this invention, the hot melt adhesive is a chip-scale hot melt adhesive. Steps S5 and S6 both use the same mask as in step S1 for development to expose the adhesive application path, followed by the application of hot melt adhesive. More specifically, the hot melt adhesive used is a micron-scale hot melt adhesive.
[0027] A further technical solution is that, in step S7, the UV adhesive coating position corresponds to the position of the adhesive application channel.
[0028] Specifically, in this invention, the UV adhesive is a chip-scale UV adhesive, and the process involves developing the UV adhesive using the same mask as in step S1 to expose the adhesive coating path, and then applying the UV adhesive. More specifically, the UV adhesive is a micron-scale UV adhesive.
[0029] A further technical solution is that, in step S3, the substrate of the bonded MicroLED wafer is thinned to 95-105 micrometers.
[0030] A further technical solution is that, in step S4, the glass material is irradiated with an infrared laser spot of 10-30 micrometers.
[0031] A further technical solution is that, in step S2, both the MicroLED wafer and the CMOS substrate are provided with alignment marks. The alignment marks facilitate precise alignment during bonding between the MicroLED wafer and the CMOS substrate, and also ensure sufficient contact between the glass frit and the CMOS substrate. Specifically, the alignment marks are cross-shaped alignment marks.
[0032] It should be noted that in the wafer-level packaging-based MicroLED device fabrication method provided by this invention, the MicroLED wafer is a horizontally structured blue light chip fabricated on a 4-inch or 6-inch sapphire substrate; the CMOS substrate has its circuitry and metal bumps pre-fabricated according to pixel control requirements. During flip-chip bonding, the markings on the MicroLED wafer are aligned with the markings on the CMOS substrate, allowing for precise bonding. The metal bumps on the CMOS substrate are electrically connected to the P and N electrodes of the MicroLED through bonding.
[0033] After the MicroLED wafer is bonded to the CMOS substrate, the process also includes attaching a quantum dot film to the side of the MicroLED wafer, allowing the blue light chip to pass through the quantum dot film to generate white light; attaching a CF chip to the quantum dot film; and finally encapsulating the wafer with a glass cover. Cutting the wafer yields multiple MicroLED devices.
[0034] In this invention, CF stands for color filter, and the RGB pixel points have been pre-set.
[0035] Secondly, the present invention provides a MicroLED device, which is fabricated using the wafer-level packaging-based MicroLED device fabrication method described in the first aspect.
[0036] Compared with the prior art, the technical effects achieved by the present invention include:
[0037] This invention provides a method for fabricating MicroLED devices based on wafer-level packaging. Utilizing an innovative MicroLED wafer-level, micron-level coating process, it directly creates coating channels on the wafer, dividing it into at least two independent units, and then performs multiple coating steps. This allows for the fabrication of multiple waterproof and oxidation-resistant MicroLED devices on the MicroLED wafer, avoiding secondary packaging. Furthermore, this method allows for direct bonding of MicroLED wafers to CMOS wafers and the attachment of quantum dot films and CF filters, enabling the fabrication of multiple MicroLED devices in a single process. This avoids color shifts caused by batch transfers and direct integration of RGB chips. Attached Figure Description
[0038] Figure 1 A flowchart illustrating the fabrication method of a MicroLED device based on wafer-level packaging provided by this invention;
[0039] Figure 2 This is a schematic diagram of the mask used to create the adhesive application path in step S1 of the present invention;
[0040] Figure 3This is a schematic diagram of applying glass material to the adhesive coating channel in step S1 of the present invention;
[0041] Figure 4 This is a schematic diagram showing the completion of glass material coating in the adhesive coating channel in step S1 of the present invention;
[0042] Figure 5 This is a schematic diagram of the MicroLED device structure based on wafer-level packaging provided by the present invention.
[0043] Figure Labels
[0044] MicroLED wafer 10, photosensitive adhesive 11, mask 12, pattern 13, coating path 14, independent cell 15, glass material 16, dicing path 17, CMOS substrate 20, quantum dot film 30, CF 40, glass cover 50, hot melt adhesive 60, UV adhesive 70. Detailed Implementation
[0045] The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Similar component reference numerals in the drawings represent similar components. Obviously, the embodiments described below are only some embodiments of the present invention, and not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.
[0046] It should be understood that, when used in this specification and the appended claims, the terms "comprising" and "including" indicate the presence of the described features, integrals, steps, operations, elements and / or components, but do not exclude the presence or addition of one or more other features, integrals, steps, operations, elements, components and / or collections thereof.
[0047] It should also be understood that the terminology used in this specification of embodiments of the invention is for the purpose of describing particular embodiments only and is not intended to limit the embodiments of the invention. As used in this specification of embodiments of the invention and the appended claims, the singular forms “a,” “an,” and “the” are intended to include the plural forms unless the context clearly indicates otherwise.
[0048] See Figures 1-5 This invention provides a MicroLED device based on wafer-level packaging and its fabrication method, specifically including the following steps:
[0049] S1. A coating channel 14 is formed on the chip side of the MicroLED wafer 10 and a glass material 16 is coated into the coating channel 14; the coating channel 14 divides the MicroLED wafer 10 into at least two independent units 15.
[0050] It should be noted that MicroLED wafers and individual cells are both small in size, so the size that can be used as coating channels is also small, about tens of micrometers. Furthermore, the coating channels need to surround the individual cells, so the coating precision requirements are high, and traditional dispensing and coating processes are difficult to meet the requirements.
[0051] like Figure 2-4 As shown, this invention employs a specific coating process to coat glass adhesive onto a MicroLED wafer. Specifically, it includes: coating a photosensitive adhesive 11 onto a MicroLED wafer 10; pre-setting a pattern 13 on a mask 12 for forming coating channels 14; placing the mask 12 on the MicroLED wafer 10 coated with photosensitive adhesive 11; irradiating with ultraviolet light and then developing to expose the corresponding coating channels 14 on the MicroLED wafer 10. The coating channels 14 divide the MicroLED wafer 10 into at least two independent units 15. A glass frit 16 is then coated into the coating channels 14. After coating, pre-baking is performed to allow the glass frit 16 to initially solidify on the MicroLED wafer 10. Then, the photosensitive adhesive 11 is cleaned to remove it, leaving only the glass frit 16 on the coating channels 14 on the MicroLED wafer 10.
[0052] Because there are numerous electrical connections between CMOS and MicroLED wafers, a glass frit with better waterproof and oxygen-resistant properties than UV adhesive and hot melt adhesive is required.
[0053] In the method for fabricating a MicroLED device based on wafer-level packaging provided by the present invention, the MicroLED wafer is a horizontal structure blue light chip of MicroLED fabricated on a 6-inch sapphire substrate; the CMOS substrate has been prefabricated with circuits and metal bumps according to pixel control requirements.
[0054] In this embodiment, the adhesive coating channel is a chip-sized, micron-sized sealed adhesive coating channel with a width of 10-30 microns.
[0055] S2. Flip-chip bonding is performed between the MicroLED wafer 10 obtained in S1 and the CMOS substrate 20.
[0056] Cross-shaped marks are pre-set at corresponding positions on the edge of the MicroLED wafer and the CMOS substrate for bonding alignment. During alignment, an optical system is used to observe whether the alignment marks coincide to ensure perfect alignment, allowing for precise bonding of the MicroLED electrodes to the substrate bumps and ensuring full contact between the glass frit and the CMOS substrate. A flip-chip method is used to thermally bond the MicroLED wafer and the CMOS substrate together.
[0057] S3. Thin the substrate of the bonded MicroLED wafer 10.
[0058] After bonding, the MicroLED wafer is thinned to approximately 100 micrometers thickness using a thinning machine to reduce the sapphire substrate.
[0059] S4. Use an infrared laser to irradiate the glass material through the MicroLED wafer substrate.
[0060] Infrared lasers are used to irradiate glass frit on a chip-level coating path through a transparent sapphire substrate, ensuring the glass frit adheres fully between the MicroLED wafer chip and the CMOS substrate, thus achieving waterproof and oxygen-resistant encapsulation of the device directly on the wafer. The infrared laser uses a spot size of 10 to 30 micrometers to scan the glass frit line by line.
[0061] S5. Apply hot melt adhesive 60 to the substrate surface of the MicroLED wafer 10 and bond it to the quantum dot film 30;
[0062] Chip-scale hot melt adhesive is coated onto the sapphire substrate of a MicroLED wafer. The application location of the hot melt adhesive must be aligned with the glass frit coating path of the MicroLED wafer chip, ensuring consistent dimensions and conformity. Figure 1 Therefore, in this embodiment, the hot melt adhesive coating location still needs to be fabricated using a mask with the same layout as in step S1, and then the hot melt adhesive is coated on the sapphire substrate of the MicroLED wafer using micro-nano processes. Then, a quantum dot film is laminated onto the MicroLED wafer surface, ensuring full contact with the hot melt adhesive, and then heated to cure the hot melt adhesive. The hot melt adhesive serves to adhere and seal the surface.
[0063] S6. Apply hot melt adhesive 60 to the quantum dot film 30 and bond it to CF40;
[0064] Similar to the method used in step S5 for applying hot melt adhesive, in this embodiment, step S6, applying hot melt adhesive to the quantum dot film, also uses a mask with the same layout as in step S1 to create hot melt adhesive application positions corresponding to the adhesive application paths. Hot melt adhesive is then applied to the quantum dot film using micro-nano processes. The CF and MicroLED wafers are then aligned and attached to the quantum dot film, and heating is used to cure the hot melt adhesive.
[0065] S7. Apply UV adhesive 70 to the CF40 and attach it to the glass cover plate 50 for sealing.
[0066] Similar to the aforementioned hot melt adhesive coating step, in this embodiment, step S7, coating the CF with UV adhesive, also uses a mask with the same layout as in step S1 to create UV adhesive coating positions corresponding to the adhesive coating path positions, and performs UV adhesive coating on the CF using micro-nano technology.
[0067] Meanwhile, to ensure a stronger bond, this embodiment also fabricates chip-level adhesive channels on the glass cover and applies UV adhesive with a size of 10-30 micrometers, aligned with the positions of the previously applied adhesive channels. The glass cover is then attached to the CF (Chip-on-Chip), and UV light is irradiated through the glass cover to cure the UV adhesive, completing the encapsulation process.
[0068] S8. Laser cut the packaged wafer to obtain MicroLED devices.
[0069] See further Figure 4 Each of the individual units 15 is further provided with a cutting channel 17 along the outer side of the adhesive coating channel 14. Specifically, the cutting channel 17 is located 1-3 micrometers outside the adhesive coating channel, where "outer side" refers to the individual unit 15 surrounded by the adhesive coating channel 14. Using a laser cutting device, laser cutting is performed along the preset cutting channel to obtain an individual MicroLED device.
[0070] Each of the individual units is surrounded by adhesive channels and sealed layer by layer so that the MicroLED device obtained after cutting has waterproof and oxygen-proof functions.
[0071] This invention provides a method for fabricating MicroLED devices based on wafer-level packaging. Utilizing an innovative chip-level, micron-level adhesive coating process, it directly creates adhesive channels on the wafer, dividing it into at least two independent units, followed by multiple steps of chip-level adhesive coating and sealing. This allows for the fabrication of multiple waterproof and oxidation-resistant MicroLED devices on the MicroLED wafer, avoiding secondary packaging. Furthermore, this method allows for direct bonding of MicroLED wafers to CMOS wafers, along with the attachment of quantum dot films and CF filters, enabling the fabrication of multiple MicroLED devices in a single process. This avoids color shifts caused by batch transfers and direct integration of RGB chips.
[0072] In the above embodiments, the descriptions of each embodiment have different focuses. For parts that are not described in detail in a certain embodiment, please refer to the relevant descriptions in other embodiments.
[0073] The above description describes specific embodiments of the present invention, but the scope of protection of the present invention is not limited thereto. Any person skilled in the art can easily conceive of various equivalent modifications or substitutions within the technical scope disclosed in the present invention, and these modifications or substitutions should all be covered within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.
Claims
1. A method for fabricating a Micro LED device based on wafer-level packaging, characterized in that, Includes the following steps: S1. A coating channel is formed on the chip side of the Micro LED wafer and a glass material is coated into the coating channel; the coating channel divides the Micro LED wafer into at least two independent units; S2. Flip-chip bond the Micro LED wafer obtained in S1 to the CMOS substrate; S3. Thin the substrate of the bonded Micro LED wafer; S4. Irradiate the glass material through the Micro LED wafer substrate using an infrared laser; S5. Apply hot melt adhesive to the surface of the Micro LED wafer substrate and bond it to the quantum dot film; S6. Apply hot melt adhesive to the quantum dot film and bond it to CF; S7. Apply UV adhesive to the CF and attach it to the glass cover plate for sealing; S8. Laser cut the packaged wafer to obtain Micro LED devices; The width of the adhesive application channel is 10-30 micrometers; Each of the independent units has a cutting channel 1-3 micrometers away from the outer side of the adhesive coating channel. In step S8, the packaged wafer is laser-cut along the cutting channel.
2. The method for fabricating a Micro LED device based on wafer-level packaging as described in claim 1, characterized in that, Step S1 specifically includes: Coating photosensitive adhesive onto Micro LED wafers; The photomask has a pattern pre-set on it for forming the adhesive coating path. The photomask is placed on the MicroLED wafer coated with photosensitive adhesive. Development exposes the corresponding coating paths on the Micro LED wafer; Coating glass frit onto Micro LED wafers; After coating, preheating is performed to allow the glass material to initially solidify on the Micro LED wafer; After removing the photosensitive adhesive, only the glass material on the adhesive coating path remains on the Micro LED wafer.
3. The method for fabricating a Micro LED device based on wafer-level packaging as described in claim 1, characterized in that, Each of the independent units is also provided with a cutting channel along the outer side of the adhesive application channel.
4. The method for fabricating a Micro LED device based on wafer-level packaging as described in claim 1, characterized in that, In step S5, the hot melt adhesive application position corresponds to the position of the adhesive application channel.
5. The method for fabricating a Micro LED device based on wafer-level packaging as described in claim 1, characterized in that, In step S6, the hot melt adhesive application position corresponds to the position of the adhesive application channel.
6. The method for fabricating a Micro LED device based on wafer-level packaging as described in claim 1, characterized in that, In step S7, the UV adhesive coating position corresponds to the position of the adhesive application channel.
7. The method for fabricating a Micro LED device based on wafer-level packaging as described in claim 1, characterized in that, In step S4, the glass material is irradiated with an infrared laser spot of 10-30 micrometers.
8. The method for fabricating a Micro LED device based on wafer-level packaging as described in claim 1, characterized in that, In step S3, the substrate of the bonded Micro LED wafer is thinned to 95-105 micrometers.
9. A Micro LED device, characterized in that, The device is fabricated using the method for fabricating a Micro LED device based on wafer-level packaging as described in any one of claims 1-8.