Method for accurately aligning and packaging micro display

Abstract

The invention discloses a method for accurately aligning and packaging a micro display, which comprises the following steps of: constructing an alignment cavity by using positive photoresist and a blue light emitting source of the micro display, and then filling red and green quantum dot materials, so that accurate alignment of a bottom blue light emitting structure and an upper light conversion layer can be realized in a micro display scheme; the method is realized by using a blue light source to illuminate and irradiate. The method is simple in process and high in implementability, atomic layer deposition can be utilized for good packaging, influence and interference of water and oxygen are blocked, the light absorption problem of a conventional black retaining wall is avoided through the side edge metal retaining wall, the optical effect can be integrally improved, and screen manufacturers can conveniently cut single-color chips of microchips. According to the invention, the technical problems of accurate alignment and packaging in the preparation of the Micro LED / Micro QLED are solved, and the commercialized service life is maintained while effective packaging is realized.

Description

Technical Field

[0001] This application relates to a method for precise alignment and packaging of a microdisplay, belonging to the technical field of optoelectronic display materials and microdisplay devices. Background Technology

[0003] The typical structure of a microdisplay device mainly includes a bottom light source, a light-converting material, an encapsulation and protection material, and an optical gain structure. Analysis of the Micro OLED device structure reveals a large number of components, from the bottom layer to the top: silicon substrate, anode electrode, white OLED (organic EL layer), cathode electrode, protective film layer, color filter, microlens, resin bonding and filling layer, and glass cover. The microfabrication process is quite complex. In Micro OLEDs, the bottom layer is a full-surface white OLED source, which is then divided into single green, single red, and single blue pixel units by the upper color filter. While it doesn't involve light source alignment, it does involve multiple processing and encapsulation techniques. The inherent problems with Micro OLEDs are relatively low brightness, difficulty in miniaturizing pixel size, and low resolution. Therefore, a more ideal solution is the Micro LED / Micro QLED solution, which utilizes a blue ultra-small pixel matrix point light source for excitation and quantum dot photoresist as the light-converting layer. This can achieve ultra-high brightness and ultra-high resolution, making it more promising.

[0004] In conventional large-size applications, the QDCC light-conversion layer is typically marked and bonded to the bottom blue light source. However, in micro-scale (below 100µm) displays, a new alignment method is required. MicroLED / Micro QLED utilizes quantum dot materials for light conversion, necessitating precise alignment between the blue light pixel and the upper quantum dot light-conversion layer. Otherwise, pixel unit control will become disordered, hindering high-precision display and control. Achieving precise alignment between the blue light emitting pixels and the quantum dot light-conversion pixels presents a significant technical challenge. Furthermore, quantum dot materials are sensitive to water and oxygen in the environment. Maintaining a commercially viable lifespan under the illumination of the bottom blue light chip is a major concern. Effective encapsulation of quantum dot materials is crucial to ensuring their lifespan. How to achieve effective encapsulation is another major technical challenge. Summary of the Invention

[0005] To address the technical challenges of precise alignment and packaging in the fabrication of Micro LEDs / Micro QLEDs, and to achieve effective packaging while maintaining a commercially viable lifespan, this application provides a method for precise alignment and packaging of microdisplays. It presents a technical implementation for the precise alignment of blue light-emitting pixels and quantum dot conversion pixels in a microdisplay. Unlike conventional photolithography alignment methods (which involve first creating a black barrier on the blue light chip and then filling it with red and green quantum dots—a method that directly constructs the chip but requires a relatively thick black photoresist, and precise alignment is difficult to achieve using negative black photoresist), this application utilizes positive photoresist and the blue light-emitting source of the microdisplay to construct an alignment cavity, which is then filled with red and green quantum dot material, effectively avoiding the problems encountered.

[0006] This application adopts the following technical solutions:

[0007] A method for precise alignment and packaging of a microdisplay, the method comprising the following steps:

[0008] A1. Deposit a metal thin film on the chip substrate, and then selectively etch the area using ICP to form a barrier, thus obtaining a patterned substrate.

[0009] The gaps between the retaining walls form a matrix of accommodating spaces;

[0010] A2. Fill the accommodating space with blue quantum dot adhesive and cure it to form a matrix of blue light-emitting pixel light sources on the chip.

[0011] A3. Apply positive photoresist to the upper side of the patterned substrate to cover the barrier and the matrix blue light-emitting pixel light source;

[0012] A4. Light up the matrix-type blue light-emitting pixel light source and expose the positive photoresist on its upper side by irradiation.

[0013] A5. Turn off the matrix blue light-emitting pixel light source, and develop I to remove the positive photoresist that is vertically aligned on its upper side, forming a cavity matrix that is vertically aligned with the matrix blue light-emitting pixel light source.

[0014] A6. Fill the corresponding cavities of the cavity matrix in step A5 with red quantum dot adhesive, green quantum dot adhesive and transparent adhesive respectively, cure II and develop II to form red light-converting pixels, green light-converting pixels and transparent pixels respectively, and obtain the light-emitting device.

[0015] A7. Remove the residual positive photoresist that has not been developed and is filling the spaces between the red light-converting pixels, green light-converting pixels, and transparent pixels on the light-emitting device to form exposed red light-converting pixels, green light-converting pixels, and transparent pixels;

[0016] A8. A metal oxide layer is deposited on the atomic layer of the exposed red light-converting pixel, green light-converting pixel, and transparent pixel to obtain the microdisplay.

[0017] Optionally, in step A1, the height of the retaining wall is 0.25 to 5 μm.

[0018] Optionally, in step A1, the metal thin film is deposited by magnetron sputtering or vacuum evaporation.

[0019] Optionally, in step A1, the material of the deposited metal film is selected from at least one of aluminum, silver, and copper.

[0020] Optionally, in step A1, the material of the deposited metal film is preferably aluminum.

[0021] Optionally, in step A1, the maximum distance between any two points on the edge of the accommodating space formed by the gap between the retaining walls is 1 to 5 μm.

[0022] Optionally, in step A1, the horizontal cross-section of the accommodating space is square, and the spacing between the retaining walls is 1 to 5 μm.

[0023] Optionally, in step A2, the filling method for filling the accommodating space with blue quantum dot adhesive is to fill the gaps in the retaining wall by printing.

[0024] Optionally, in step A3, the positive photoresist is selected from at least one of acrylate photoresist, phenolic resin photoresist, and epoxy acrylate photoresist.

[0025] Optionally, in step A3, the positive photoresist is selected from at least one of S1800, AZ5214, BCI-3511, SPR955, AZ1500, and AZ6100. The aforementioned positive photoresist is selected from products of Suzhou Ruicai Co., Ltd.

[0026] Preferably, the positive photoresist is applied by spin coating;

[0027] The spin coating thickness is 3–6 μm.

[0028] Spin coating is used to apply photoresist evenly to the underlying device using centrifugal force, and the coating thickness is controlled.

[0029] Optionally, in step A4, the exposure time is 10 to 240 seconds.

[0030] Optionally, in step A4, the matrix-type blue light-emitting pixel light source is lit up, emitting photons in the blue light band to irradiate and expose the positive photoresist on its upper side. The exposure time is controlled to increase the solubility of the photoresist in the developer in the irradiated area.

[0031] Optionally, in step A5, after turning off the light source, the entire photoresist is developed and removed. The resin in the illuminated area is removed, leaving a cavity that is perpendicularly aligned with the light source pixel. Since the solubility of the positive photoresist increases in the area irradiated by light, a good patterning effect can be achieved by using a suitable developer.

[0032] Optionally, in step A6, the filling is preferably done by spin coating.

[0033] Optionally, in step A7, the solvent used for removing residual positive photoresist is selected from at least one of acetone, ethyl acetate, and alcohol.

[0034] Optionally, in step A7, the residual positive photoresist needs to be removed, which is beneficial for subsequent processing of the quantum dot pixel area.

[0035] Optionally, in step A8, the thickness of the deposit is 1 to 5 nm.

[0036] Optionally, in step A8, the metal oxide is selected from at least one of aluminum oxide and silicon oxide.

[0037] Alternatively, an atomic layer deposition method can be used to deposit a metal oxide layer on the surface of the quantum dot photoresist to protect it from damage by water and oxygen in the environment.

[0038] Optionally, the quantum dot material in the blue, red, and green quantum dot adhesives is generally at least one of carbon quantum dot material, silicon quantum dot material, germanium quantum dot material, cadmium sulfide quantum dot material, cadmium selenide quantum dot material, zinc selenide quantum dot material, indium phosphide quantum dot material, and perovskite quantum dot material.

[0039] Optionally, the filling method of the blue quantum dot adhesive, red quantum dot adhesive, green quantum dot adhesive, and transparent adhesive can be independently selected from printing, dispensing, inkjet printing, and microfluidics.

[0040] Blue quantum dot adhesive, red quantum dot adhesive, green quantum dot adhesive, and transparent adhesive are not strictly limited in this application. Those skilled in the art can select from the existing technology or choose a single component to combine and configure as needed.

[0041] Optionally, the curing methods I and II are independently selected from at least one of thermosetting crosslinking and photosetting crosslinking.

[0042] Optionally, the developer used for developing I and developing II is selected from at least one of alkaline potassium hydroxide developer, tetramethylammonium hydroxide developer, and sodium carbonate developer.

[0043] Optionally, after step A8, the method further includes: constructing a highly reflective metal barrier on the sides of the red light-converting pixels, green light-converting pixels, and transparent pixels of the surface atomic layer deposited with a metal oxide layer, thereby obtaining the microdisplay;

[0044] The method for constructing the highly reflective metal barrier can be referred to in patent CN117457838A.

[0045] High-reflectivity metal barriers can isolate pixel units to prevent light crosstalk and reflect the light from pixel units without absorption, thereby improving overall light output efficiency.

[0046] The beneficial effects that this application can produce include:

[0047] This application provides a method for precise alignment and packaging of microdisplays, specifically a technical implementation of precise alignment between blue light emitting pixels and quantum dot light-converting pixels in a microdisplay. This method achieves precise alignment between the underlying blue light-emitting structure and the upper light-converting layer within the microdisplay solution. This alignment is achieved by irradiating the surface with blue light from a light source. The alignment cavity is constructed using positive photoresist and the blue light emitting source of the microdisplay. Positive photoresist offers superior resolution compared to black negative barrier photoresist, and its thickness can be increased. The process is simple and highly feasible. After filling with red and green quantum dot materials, atomic layer deposition can be used to effectively encapsulate the quantum dot pixels, including side encapsulation to prevent interference from water and oxygen. The positive photoresist can be removed next to the quantum dot pixels, followed by a high-reflectivity metal barrier design. This metal barrier offers higher reflectivity than the original black barrier, effectively improving the optical gain of the overall optical system and enabling higher levels of device brightness.

[0048] The method for precise alignment and packaging of microdisplays provided in this application is beneficial for screen manufacturers to re-cut monochrome chips of microchips, and single-pixel chips can be reassembled for white light mini LED scenarios. The technical solution of this application focuses on solving the full-color realization scenario in the Mini and Micro fields of microdisplays. It provides a better solution to the technical challenges of high-precision alignment and packaging by combining quantum dot materials and photolithography process routes. Attached Figure Description

[0049] Figure 1 This is a schematic diagram of the method for precise alignment and packaging of the microdisplay of this application. A1 is the step of fabricating the barrier, A2 is the step of filling with blue quantum dots, A3 is the step of spin-coating positive photoresist, A4 is the step of irradiation exposure with blue light source, A5 is the step of development, A6 is the step of filling with red and green quantum dots, A7 is the step of removing positive photoresist, and A8 is the step of atomic layer deposition and packaging. Detailed Implementation

[0050] The present application is described in detail below with reference to the embodiments, but the present application is not limited to these embodiments.

[0051] Unless otherwise specified, all raw materials used in the embodiments of this application were purchased through commercial channels.

[0052] Unless otherwise specified, all test methods are conventional and all instrument settings are those recommended by the manufacturer.

[0053] Example 1

[0054] A 3µm aluminum thin film was deposited on a chip substrate using magnetron sputtering, followed by selective area ICP etching to obtain a patterned substrate with aluminum as the barrier (barrier spacing of 2µm). CdSe blue quantum dot adhesive (printed in) was filled into the barrier gaps to serve as the blue light source for the bottom layer illumination. The substrate was baked at 70°C for 3 minutes to remove the solvent, allowing for quantum dot thermal crosslinking. Positive photoresist S1800 was spin-coated over the device structure at 4000 rpm for 60 seconds to obtain a 5µm thick layer. The bottom CdSe blue quantum dots were then illuminated, emitting blue light photons to irradiate the positive photoresist for 30 seconds. The light source was then turned off, and the entire substrate was developed and the photoresist removed using tetramethylammonium hydroxide as the developer. The irradiated resin was removed, leaving a cavity perpendicular to the light source pixels with a depth of 5µm. CdSe red-green quantum dots were mixed with negative photoresist SU-8, with a solid content controlled at 20%, to prepare three types of adhesives: single red, single green, and transparent. These adhesives were then used to fill the cavity above the light source, with a curing energy of 200 mJ / cm². 2 The exposure energy was 30 s, and development was performed using a 0.45% KOH aqueous solution for 1 min. The positive photoresist at the spin-coated edges was removed with acetone. An aluminum oxide layer was deposited on the quantum dot photoresist surface using atomic layer deposition (ALD) for protection, with the layer thickness controlled at 3 nm. After ALD, a metal barrier was constructed on the side according to the method described in patent CN117457838A, and a metal reflective layer was selectively grown in specific areas.

[0055] Example 2

[0056] A 0.5µm aluminum thin film was deposited on a chip substrate using vacuum evaporation, followed by selective area etching (ICP) to obtain a patterned substrate with aluminum as the barrier (barrier spacing of 1µm). Modified ZnSe blue quantum dot adhesive was then filled into the barrier gaps (dispensing introduction) to serve as the blue light source for the underlying illumination, achieving a blue light irradiance of 150mW / cm². 2Quantum dot photocrosslinking can be achieved after 20 seconds of irradiation. Positive photoresist AZ5214 is spin-coated onto the device structure at 6000 rpm for 60 seconds to obtain a 4µm thick layer. The underlying ZnSe blue quantum dots are then illuminated, emitting blue light photons to irradiate the positive photoresist for 60 seconds. The light source is then turned off, and overall development and photoresist removal are performed using alkaline potassium hydroxide as the developer. The resin in the irradiated areas is removed, leaving cavities perpendicular to the light source pixels. ZnSe red-green quantum dots are mixed with negative photoresist SU-8 at a solid content of 20% to prepare single-red, single-green, and transparent adhesives. These are then filled into the cavities above the light source (3µm deep) at a curing energy of 100 mJ / cm². 2 The exposure energy was 30s, and development was performed using a 0.45% KOH aqueous solution for 30s. The positive photoresist at the spin-coated edges was removed with acetone, and an aluminum oxide layer was deposited on the surface of the quantum dot photoresist using atomic layer deposition (ALD) for protection. The thickness of the deposited layer was controlled to be 4nm.

[0057] Example 3

[0058] A 1µm aluminum thin film was deposited on a chip substrate using magnetron sputtering, followed by selective area etching (ICP) to obtain a patterned substrate with aluminum as baffles (baffle spacing of 3µm). CdZnSe blue quantum dot adhesive (introduced through spray printing) was filled into the baffle gaps to serve as the blue light source for illumination. The substrate was baked at 80°C for 3 minutes, followed by a 150mW / cm² heat treatment. 2 Quantum dot dual curing and crosslinking can be achieved with irradiation for 10 seconds. Positive photoresist AZ6100 is spin-coated onto the device structure at 8000 rpm for 60 seconds to obtain a 3µm thick layer. The underlying CdZnSe blue quantum dots are then illuminated, emitting blue light photons to irradiate the positive photoresist for 120 seconds. The light source is then turned off, and overall development and photoresist removal are performed using tetramethylammonium hydroxide as the developer. The irradiated resin is removed, leaving a cavity perpendicular to the light source pixels with a depth of 3µm. CdZnSe red-green quantum dots are mixed with negative photoresist SU-8 at a solid content of 20% to prepare single-red, single-green, and transparent adhesives, which are then filled into the cavities above the light source. The curing energy is 200 mJ / cm². 2 Exposure energy was set to 30 s, and development was performed using a 0.45% KOH aqueous solution for 1 min. The positive photoresist at the spin-coated edges was removed with alcohol, and an aluminum oxide layer was deposited on the quantum dot photoresist surface using atomic layer deposition for protection, with the deposition layer thickness controlled to 1 nm.

[0059] Example 4

[0060] A 2µm aluminum thin film was deposited on a chip substrate using vacuum evaporation, followed by selective area etching (ICP) to obtain a patterned substrate with aluminum as the barrier (barrier spacing of 5µm). InP blue quantum dot adhesive (introduced via microfluidics) was filled into the barrier gaps to serve as the blue light source for the bottom layer illumination. The substrate was baked at 70°C for 3 minutes to remove the solvent, allowing for quantum dot thermal crosslinking. A positive photoresist, BCI-3511, was spin-coated over the device structure at 3000 rpm for 60 seconds to obtain a 6µm thick adhesive layer. The bottom InP blue quantum dots were then illuminated, emitting blue light photons to irradiate the positive photoresist for 240 seconds. The light source was then turned off, and the entire substrate was developed and the photoresist removed using tetramethylammonium hydroxide as the developer. The resin in the illuminated areas was removed, leaving cavities perpendicular to the light source pixels with a depth of 6µm. InP red and green quantum dots were mixed with negative photoresist SU-8, with a solid content controlled at 20%, to prepare three types of adhesives: single red, single green, and transparent. These adhesives were then used to fill the cavity above the light source, with a curing energy of 200 mJ / cm². 2 The exposure energy was 30s, and development was performed using a KOH (0.45% concentration) aqueous solution for 1min. The positive photoresist at the spin-coated edges was removed with ethyl acetate, and an aluminum oxide layer was deposited on the surface of the quantum dot photoresist using atomic layer deposition to protect it, with the thickness of the deposited layer controlled at 5nm.

[0061] Comparative Example

[0062] A 4µm thick black barrier layer with a 200µm spacing is first photolithographically etched onto an 8-inch glass slide. The pixel apertures are 300µm x 300µm in length and width. Red and green quantum dot photoresist is then used to fill the pixel apertures within the barrier layers, with a solid content controlled at 20%, followed by photocuring to obtain the QDCC component. An 8-inch wafer chip substrate is placed on a microscope platform, and a layer of structural double-curing adhesive is applied to the wafer chip surface for pixel bonding and curing.

[0063] By comparing and implementing the experiments in Cases 1 to 4, the performance parameters are shown in Table 1. The results show that the minimum resolution of red and green pixels using the positive photoresist AZ5214 is 3µm, with no residual adhesive at the edges and good edge roughness. This proves that the method for precise alignment of the microdisplay designed in this application is feasible, and the sample encapsulated by ALD has much better environmental stability than the sample without encapsulation.

[0064] Table 1: Comparison of Performance Parameters with Implementation Cases 1-4

[0065] Sample differences Positive photoresist Red / green pixel resolution Residual adhesive at the edges Pixel edge roughness Comparative Example / 300um / / Implementation Case 1 S1800 5um good good Implementation Case 2 AZ5214 3um good good Implementation Case 3 AZ6100 11um good good Implementation Case 4 BCI-3511 6um good good

[0066] This application embodies, but is not limited to, the underlying quantum dot blue light emitting layer of Micro QLED, and is also applicable to the high-precision alignment of the blue light chip of MicroLED with the QDCC color conversion layer, as well as the high-precision alignment of Micro OLED with the QDCC color conversion layer.

[0067] The above description is merely a few embodiments of this application and is not intended to limit this application in any way. Although this application discloses preferred embodiments as described above, it is not intended to limit this application. Any changes or modifications made by those skilled in the art without departing from the scope of the technical solution of this application using the disclosed technical content are equivalent to equivalent implementation cases and fall within the scope of the technical solution.

Claims

1. A method for precise alignment and packaging of a microdisplay, characterized in that, The method includes the following steps: A1. Deposit a metal thin film on the chip substrate, and then selectively etch the area using ICP to form a barrier, thus obtaining a patterned substrate. The gaps between the retaining walls form a matrix of accommodating spaces; A2. Fill the accommodating space with blue quantum dot adhesive and cure it to form a matrix of blue light-emitting pixel light sources on the chip; A3. Apply positive photoresist to the upper side of the patterned substrate to cover the barrier and the matrix blue light-emitting pixel light source; A4. Light up the matrix-type blue light-emitting pixel light source and expose the positive photoresist on its upper side by irradiation. A5. Turn off the matrix blue light-emitting pixel light source, and develop I to remove the positive photoresist that is vertically aligned on its upper side, forming a cavity matrix that is vertically aligned with the matrix blue light-emitting pixel light source. A6. Fill the corresponding cavities of the cavity matrix in step A5 with red quantum dot adhesive, green quantum dot adhesive and transparent adhesive respectively, cure II and develop II to form red light-converting pixels, green light-converting pixels and transparent pixels respectively, and obtain the light-emitting device. A7. Remove the residual positive photoresist that has not been developed and is filling the spaces between the red light-converting pixels, green light-converting pixels, and transparent pixels on the light-emitting device to form exposed red light-converting pixels, green light-converting pixels, and transparent pixels; A8. A metal oxide layer is deposited on the atomic layer of the exposed red light-converting pixel, green light-converting pixel, and transparent pixel to obtain the microdisplay.

2. The method according to claim 1, characterized in that, In step A1, the height of the retaining wall is 0.25–5 μm; Preferably, in step A1, the method of depositing the metal thin film is magnetron sputtering or vacuum evaporation; Preferably, in step A1, the material of the deposited metal film is selected from at least one of aluminum, silver, and copper; Preferably, in step A1, the maximum distance between any two points on the edge of the accommodating space formed by the gap between the retaining walls is 1 to 5 μm; Preferably, in step A1, the horizontal cross-section of the accommodating space is square, and the spacing between the retaining walls is 1 to 5 μm.

3. The method according to claim 1, characterized in that, In step A3, the positive photoresist is selected from at least one of acrylate photoresist, phenolic resin photoresist, and epoxy acrylate photoresist; Preferably, in step A3, the positive photoresist is selected from at least one of S1800, AZ5214, BCI-3511, SPR955, AZ1500, and AZ6100; Preferably, in step A3, the positive photoresist is applied by spin coating; The spin coating thickness is 3–6 μm.

4. The method according to claim 1, characterized in that, In step A4, the exposure time is 10 to 240 seconds.

5. The method according to claim 1, characterized in that, In step A7, the solvent used to remove residual positive photoresist is selected from at least one of acetone, ethyl acetate, and alcohol.

6. The method according to claim 1, characterized in that, In step A8, the thickness of the deposit is 1–5 nm; Preferably, in step A8, the metal oxide is selected from at least one of aluminum oxide and silicon oxide.

7. The method according to claim 1, characterized in that, The quantum dot materials in blue, red, and green quantum dot adhesives are generally at least one of the following: carbon quantum dot materials, silicon quantum dot materials, germanium quantum dot materials, cadmium sulfide quantum dot materials, cadmium selenide quantum dot materials, zinc selenide quantum dot materials, indium phosphide quantum dot materials, and perovskite quantum dot materials.

8. The method according to claim 1, characterized in that, The filling methods for blue quantum dot adhesive, red quantum dot adhesive, green quantum dot adhesive, and transparent adhesive are independently selected from printing, dispensing, inkjet printing, and microfluidics.

9. The method according to claim 1, characterized in that, The curing methods I and II are independently selected from at least one of thermosetting crosslinking and photosetting crosslinking; Preferably, the developer used for developing I and developing II is selected from at least one of alkaline potassium hydroxide developing agent, tetramethylammonium hydroxide developing agent, and sodium carbonate developing agent.

10. The method according to claim 1, characterized in that, Following step A8, the process further includes: constructing highly reflective metal barriers on the sides of the red light-converting pixels, green light-converting pixels, and transparent pixels of the surface atomic layer deposited with a metal oxide layer, thereby obtaining the microdisplay.

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