Structure for improving brightness of Micro LED and manufacturing method thereof
By adopting a reflective retaining wall structure with high aspect ratio and inclination angle in Micro LED microdisplay, the problem of insufficient width of the retaining wall between pixels is solved, brightness and resolution are improved, and power consumption and production costs are reduced.
Patent Information
- Application Number
- CN202411544973.1
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-10-31
- Publication Date
- 2025-02-25
AI Technical Summary
As the pixel density of Micro LED microdisplays increases, the width of the inter-pixel retaining wall is getting smaller and smaller, making it difficult to make a retaining wall of sufficient height to accommodate the quantum dot-to-light layer, resulting in a decrease in display color purity and an increase in energy consumption.
A high-deep aspect ratio reflective retaining wall structure with inclination angle is adopted. Through a stacked structure and electron beam evaporation technology, a high-deep aspect ratio reflective retaining wall is formed in the gap between the pixel light emitting unit matrix, thereby enhancing the resolution and luminous area of the Micro LED microdisplay.
Improves the brightness and resolution of Micro LED microdisplay, reduces leakage and power consumption of excitation light, enhances light output efficiency, and reduces production costs.
Smart Images
Figure CN119521924A_ABST
Abstract
Description
Technical Field
[0001] The present application relates to a structure for improving the brightness of Micro LEDs and a method for manufacturing the same, and belongs to the technical field of display devices. Background Art
[0002] The sidewall light emission in the technology of using quantum dot light conversion to achieve full colorization of Micro LED microdisplays will cause light crosstalk between pixels, reducing the display color purity of the panel. Therefore, it is necessary to add retaining walls between pixels to eliminate light crosstalk. Traditional retaining walls do not have the ability to reflect light, which will lead to reduced light output efficiency of pixels and increased energy consumption. And as the pixel density of Micro LED microdisplays increases, the width of the retaining walls is getting smaller and smaller. When using the lift off process to make retaining walls, it is more difficult to make retaining walls of sufficient height (high aspect ratio) to accommodate a quantum dot light conversion layer of sufficient thickness because the pores left for the retaining wall material to fill are too small. Summary of the invention
[0003] In order to solve the problem in the prior art that as the pixel density increases, the width of the retaining wall between pixels of the Micro LED micro display becomes smaller and smaller, making it difficult to make it high enough to accommodate the quantum dot light conversion layer, the present application provides a structure for greatly improving the brightness of the Micro LED and a method for making it, adopting a reflective retaining wall structure with an inclined angle, and utilizing a reflective retaining wall design with a high aspect ratio and an inclined angle to improve the resolution and luminous area of the Micro LED micro display.
[0004] The application adopts the following technical solutions:
[0005] According to one aspect of the present application, a structure for improving the brightness of Micro LEDs is provided, including a high aspect ratio reflective baffle wall disposed in the gap between pixel light emitting unit matrices;
[0006] The pixel light-emitting unit matrix and the high aspect ratio reflective baffle are both arranged on a Micro LED microdisplay wafer substrate.
[0007] The high aspect ratio reflective baffle wall comprises a substrate adhesive layer, a reflective layer, and a top encapsulation layer stacked from bottom to top;
[0008] The reflective layer is one metal layer or at least two metal layers with different widths;
[0009] In any two adjacent metal layers, the bottom end surface size of the metal layer on the side relatively close to the top packaging layer is smaller than the top end surface size of the metal layer on the side relatively far from the top packaging layer;
[0010] The size of the top end surface of the substrate bonding layer is larger than the size of the bottom end surface of the metal layer adjacent thereto;
[0011] The bottom end face size of the top encapsulation layer is smaller than the width and smaller than the top end face size of the metal layer adjacent thereto;
[0012] The high aspect ratio reflective baffle wall has an aspect ratio greater than 5.
[0013] The aspect ratio is the ratio of the depth of the pixel cavity formed by the retaining wall (the height of the retaining wall) to the half-height width of the retaining wall.
[0014] In the present application, the reflective layer is composed of at least two metal layer structures of different widths, each metal layer is narrow at the top and wide at the bottom, and the bottom thickness of the upper metal layer is not greater than the top thickness of the adjacent lower metal layer.
[0015] The pixel light-emitting unit in the present application is not strictly limited, and can be, for example, a light-emitting chip such as GaN.
[0016] Optionally, the top end surface size of the substrate bonding layer, the top packaging layer, and the metal layer is smaller than the bottom end surface size.
[0017] Optionally, the side walls of the substrate adhesive layer, the top packaging layer, and the metal layer are independently a planar structure or an inwardly concave arc structure.
[0018] Optionally, the material of each metal layer is independently selected from at least one of Ti, Al, Pt, Au, Cr, Ag, Cu, Sn, Ti, In, and Bi. It can be a single material of the above materials or an alloy material, such as Au-Sn, TiAl, TiNi and other alloys.
[0019] Optionally, the material of the substrate bonding layer is selected from at least one of Cr, Ti, Pt and Au.
[0020] Optionally, the material of the top packaging layer is selected from Au.
[0021] Optionally, the layer structure of the reflective retaining wall can be made of materials selected from Cr-Pt-Au-Ti-Al-Al-Ti-Au, Ti-Pt-Au-Ag-Ag-Ag-Au, Cr-Pt-Au-Ti-Al-Ti-Al-Ti-Au, Cr-Pt-Au-Ti-Al-Au-Ti-Al-Au-Ti-Al-Au-Ti-Al-Au from bottom to top, wherein Cr, Pt, and Au are substrate bonding layers, Al, Ti, Ag, and their intermediate insertion layers such as Au are reflective layers, and the upper layer Au is an encapsulation layer.
[0022] Optionally, the thickness of the substrate adhesive layer is less than 500 nm.
[0023] Optionally, the thickness of the substrate adhesive layer is less than 100 nm.
[0024] Optionally, the thickness of the substrate adhesive layer is less than 20 nm.
[0025] Optionally, the thickness of the reflective layer is less than 10 μm.
[0026] Optionally, the thickness of the reflective layer is less than 5 μm.
[0027] Optionally, the thickness of the reflective layer is less than 2 μm.
[0028] Optionally, the thickness of the metal layer is less than 100 nm.
[0029] Optionally, the thickness of the metal layer is less than 50 nm.
[0030] Optionally, the thickness of the top encapsulation layer is less than 500 nm.
[0031] Optionally, the thickness of the top encapsulation layer is less than 100 nm.
[0032] Optionally, the bottom width of the high aspect ratio reflective blocking wall is less than 5 μm.
[0033] Optionally, the bottom width of the high aspect ratio reflective blocking wall is less than 2 μm.
[0034] Optionally, the bottom width of the high aspect ratio reflective blocking wall is less than 0.5 μm.
[0035] Optionally, the bottom width of the high aspect ratio reflective blocking wall is less than 0.3 μm.
[0036] The width of the substrate bonding layer is not less than the bottom width of the reflective layer, the width of the top encapsulation layer is not less than the top width of the reflective layer, and the width of any metal layer is not less than the top width of the lower metal layer it contacts.
[0037] Optionally, the top width of the high aspect ratio reflective blocking wall is less than 1 μm.
[0038] Optionally, the top width of the high aspect ratio reflective blocking wall is less than 0.4 μm.
[0039] Optionally, the top width of the high aspect ratio reflective blocking wall is less than 0.25 μm.
[0040] According to another aspect of the present application, a method for preparing the above-mentioned structure for improving the brightness of Micro LED is provided, comprising the following steps:
[0041] On a substrate containing a pixel light-emitting unit array, a substrate bonding layer, a reflective layer, and a top encapsulation layer are sequentially deposited on the substrate by electron beam evaporation in the vertical space between the pixel light-emitting units using a photoresist mask, thereby forming a high-aspect-ratio reflective baffle located in the gap between the pixel light-emitting unit matrix, thereby obtaining the structure for highly enhancing the brightness of the Micro LED;
[0042] The steps of making the photoresist mask include: using a negative photoresist to perform photolithography using a mask plate, developing, forming a photoresist mask covering the pixel light-emitting units, and forming gaps for electron beam evaporation in the vertical spaces between the pixel light-emitting units on the photoresist mask;
[0043] The cross section of the photoresist mask covering the pixel light-emitting unit is an inverted trapezoid.
[0044] In the preparation method of the structure for improving the brightness of Micro LED provided in the present application, the processing of the reflective baffle with high aspect ratio is to use the photolithography method to process the gap filled with the reflective baffle in the groove between the pixel light-emitting units such as GaN, and the gap is covered by the photoresist, and the photoresist mask is an inverted trapezoidal structure. Then, the metal is filled in the pores by electron beam evaporation and the photoresist is removed to complete the production of the first layer of reflective baffle. Then, by repeating the above processing process, the height of the reflective baffle is increased until the design index is reached.
[0045] Optionally, the following steps are included:
[0046] S1. On a substrate having an array of pixel light-emitting units, photolithography is performed using a negative photoresist and a mask, and development is performed to form a photoresist mask covering the pixel light-emitting units, and gaps are formed in the vertical spaces between the pixel light-emitting units, and then electron beam evaporation is used to deposit a substrate bonding layer in the gaps, and the photoresist mask is removed;
[0047] S2, on the substrate processed in step S1, using a negative photoresist and a mask plate to perform photolithography, develop, form a photoresist mask covering the pixel light-emitting units, and form a gap on the upper side of the substrate bonding layer in the vertical space between the pixel light-emitting units, then use electron beam evaporation to deposit a metal layer in the gap, and remove the photoresist mask;
[0048] S3, forming a reflective layer after step S2 or after step S2 and then after at least one of the following steps: performing photolithography using a negative photoresist and developing the mask to form a photoresist mask covering the pixel light-emitting units, and forming a gap on the upper side of the metal layer formed in the previous step in the vertical space between the pixel light-emitting units, and then using electron beam evaporation to deposit a new metal layer in the gap, and removing the photoresist mask;
[0049] S4. On the substrate processed in step S3, photolithography is performed using a negative photoresist using a mask template, and development is performed to form a photoresist mask covering the pixel light-emitting units, and a gap is formed on the upper side of the metal layer formed in the previous step in the vertical space between the pixel light-emitting units, and then a top encapsulation layer is deposited in the gap using electron beam evaporation, and the photoresist mask is removed to form a high aspect ratio reflective baffle wall in the gap between the pixel light-emitting unit matrix to obtain the structure that highly enhances the brightness of the Micro LED.
[0050] Optionally, in step S1, the bottom width of the gap is <2 μm.
[0051] Optionally, in step S1, the top width of the gap is <1.8 μm.
[0052] Optionally, in step S1, the height of the gap is greater than 2 μm.
[0053] In the present application, a first layer of photoresist mask is made: the photoresist mask completely covers the pixel light-emitting units such as GaN, and there are gaps between the photoresist masks for subsequent filling of metal reflective baffles. The metal is filled into the gaps by evaporation, wherein the substrate bonding layer can also be used as the connecting metal of the upper electrode (common cathode / common anode) of the GaN pixel, preferably Ti, Cr or Pt, and the reflective layer metal is preferably Al, Ag, Ti, Sn, Pt, Au, and the photoresist thickness, the maximum thickness is determined by the photoresist removal process. After the photoresist is removed, the production of the first layer of reflective baffles is completed; then the second layer of photoresist mask is prepared: the gaps (if any) between the pixel light-emitting units such as GaN and below the top of the first layer of reflective baffles are completely filled by the second layer of photoresist mask, and the area above the top of the first layer of reflective baffles has gaps of the second layer of photoresist mask, the bottom width of the gap is not greater than the width of the top of the first layer of reflective baffles, and the gap boundary is within the edge of the first layer of reflective baffles. Use the evaporation method to fill the pores with metal. The thickness of the metal filled is less than the height of the pores between the photoresists. The maximum thickness is determined by the process of removing the photoresist. If you need to continue to increase the height of the reflective retaining wall, repeat the second layer of reflective retaining wall process.
[0054] Optionally, the electron beam evaporation is single-gun electron beam evaporation or double-gun electron beam evaporation;
[0055] Optionally, the evaporation source of the dual-gun electron beam evaporation is a single source or a dual source.
[0056] Optionally, in step S2 to step S4, the photoresist mask covering the pixel light-emitting unit independently covers partial edges of the substrate bonding layer, the metal layer, and the top packaging layer, so that the top end surface thereof is not completely exposed in the gap.
[0057] The beneficial effects of this application include:
[0058] The structure for improving the brightness of Micro LED provided by the present application has a reflective baffle with a high aspect ratio, which can increase the thickness of the quantum dot light conversion layer, reduce the leakage of excitation light, improve energy utilization (more excitation light is absorbed and converted into light of the required wavelength, less energy loss, and reduced power consumption at the same required brightness), reduce power consumption, and the reflective baffle with an inclined angle can reflect more light from the front, improve light extraction efficiency, and reduce power consumption. The method for making the structure for improving the brightness of Micro LED provided by the present application has the characteristics of simple process, low cost, and obvious effect of improving resolution and brightness. It is compatible with the Micro LED micro-display processing technology in the prior art and can be quickly introduced. BRIEF DESCRIPTION OF THE DRAWINGS
[0059] Figure 1 A schematic diagram of a method for processing a reflective retaining wall with a high aspect ratio according to the present application;
[0060] Figure 2 This is a schematic diagram of a reflective retaining wall structure with a high aspect ratio and an inclined angle in Example 2 of the present application;
[0061] Figure 3 This is a schematic diagram of a reflective retaining wall structure with a high aspect ratio and an arc-shaped inclination angle in Example 3 of the present application;
[0062] Figure 4 This is a scanning electron microscope image of the reflective retaining wall with a high aspect ratio in Example 2 of the present application, with a scale of 20 μm.
[0063] Figure 5 This is a confocal microscope image of the reflective baffle with a high aspect ratio in Example 2 of the present application.
[0064] Figure 6 This is a scanning electron microscope image of the reflective retaining wall with a high aspect ratio and an inclined angle in Example 3 of the present application, with a scale of 20 μm.
[0065] Figure 7 This is a confocal microscope image of the reflective baffle with a high aspect ratio and an inclined angle in Example 3 of the present application.
[0066] List of parts and reference numerals:
[0067] 1. First photoresist mask; 2. GaN pixel light-emitting unit; 3. Micro LED microdisplay wafer substrate; 4. First layer of reflective baffles; 5. Second photoresist mask; 6. Second layer of reflective baffles. DETAILED DESCRIPTION
[0068] The present application is described in detail below with reference to embodiments, but the present application is not limited to these embodiments.
[0069] Unless otherwise specified, the raw materials in the examples of this application were purchased through commercial channels.
[0070] Unless otherwise specified, conventional methods were used for testing and instrument settings were those recommended by the manufacturer.
[0071] Example 1
[0072] Taking a Micro LED microdisplay wafer substrate (3) with a pixel size of 5 μm as an example, the diameter of the GaN pixel light-emitting unit (2) is 3.5 μm, the pixel pitch is 1.5 μm, and the height of the GaN pixel light-emitting unit (2) is 1.2 μm. Figure 1 The schematic diagram of the manufacturing process is shown below. The steps for making a structure that can improve the brightness of Micro LED are as follows:
[0073] S1. Make the first layer of reflective retaining wall:
[0074] Firstly, a negative photoresist is used to photolithographically produce a first photoresist mask (1) on the GaN pixel light-emitting unit (2): the photoresist completely covers the GaN pixel light-emitting unit (2), the cross section of the covered photoresist is an inverted trapezoid, and gaps are formed in the area between the pixel light-emitting units (2);
[0075] Then, a single-gun electron beam evaporation device is used to sequentially evaporate Cr, Pt, and Au in the gap to thicknesses of 10 nm, 20 nm, and 500 nm, respectively, to form a first layer of reflective retaining wall (4) as a substrate bonding layer, which can also serve as a top common electrode. After the evaporation is completed, a degumming liquid is used to remove the first photoresist mask (1), thereby completing the production of the first layer of reflective retaining wall (4).
[0076] S2, stacked and elevated reflective retaining wall:
[0077] First, a second photoresist mask (5) is made on the GaN pixel light-emitting unit (2) using a negative photoresist: the photoresist completely covers the GaN pixel light-emitting unit (2) and the gap between it and the first layer of reflective baffle wall (4), and covers part of the edge of the top surface of the first layer of reflective baffle wall (4) (covering about 100nm), the cross section of the covered photoresist is an inverted trapezoid, and a gap is formed in the upper area of the first layer of reflective baffle wall (4);
[0078] Then, Ag is sequentially evaporated in the gap using a single-gun electron beam evaporation device, with a thickness of 2000 nm, to form a second layer of reflective baffles (4) as a metal layer. After the evaporation is completed, the second photoresist mask (5) is removed using a degumming liquid to complete the production of the second layer of reflective baffles (6). The bottom end face size of the second layer of reflective baffles (6) is smaller than the top end face size of the first layer of reflective baffles (4), to form two layers of superimposed reflective baffles;
[0079] S3. Repeat the process of making the retaining wall in step S2 once to complete the production of the third layer of reflective retaining wall which also serves as a metal layer (the thickness of the third layer of reflective retaining wall is the same as that of the second layer), the bottom end face size of the third layer of reflective retaining wall is smaller than the top end face size of the second layer of reflective retaining wall (6), forming a three-layer stacked reflective retaining wall, of which two metal layers serve as reflective layers.
[0080] S4. Repeat the process of making the retaining wall in step S3 once to complete the production of the fourth layer of reflective retaining wall as the top packaging layer. The bottom end surface size of the fourth layer of reflective retaining wall is smaller than the top end surface size of the third layer of reflective retaining wall, forming 4 layers of stacked reflective retaining walls. The difference from step S3 is that the evaporated layer is Au with a thickness of 500nm.
[0081] After steps S1 to S4, a total of four layers of superimposed reflective baffles with a high aspect ratio are formed between the GaN pixel light-emitting units (2), with a height of 4.5 μm and an aspect ratio of 4 (the width is the half-height width of the reflective baffle). Since each layer of the reflective baffle is narrow at the top and wide at the bottom, the four superimposed reflective baffles have a high aspect ratio, and the macroscopic side walls of the reflective baffles also form a certain tilt angle with the vertical direction of the Micro LED microdisplay wafer substrate, that is, a reflective baffle with an inclined angle is formed.
[0082] The 4.5μm retaining wall filled with red quantum dot material with a thickness of 4.5μm can absorb all blue light excitation light, and the brightness is 1250 nits (relative value). The 2μm retaining wall filled with red quantum dot material with a thickness of 2μm can absorb 80% of the blue light excitation light. After using a filter to filter out the unabsorbed 20% blue light, the brightness is 980 nits.
[0083] Example 2
[0084] The manufacturing steps are the same as those in Example 1, except that the process of forming the retaining wall by evaporation uses a single-gun electron beam evaporation device to form a reflective retaining wall structure with a high aspect ratio and an inclined angle. The difference in evaporation makes the sidewalls of each reflective retaining wall layer form a certain inclined angle with the vertical direction of the Micro LED microdisplay wafer substrate. The structure is as follows Figure 2 As shown, the actual Figure 4 , Figure 5 (Scanning electron microscope images, confocal microscope images).
[0085] Example 3
[0086] The manufacturing steps are the same as those in Example 1, except that the process of forming the retaining wall by evaporation uses a double-gun electron beam evaporation device and a double-source evaporation to form a reflective retaining wall with a high aspect ratio and an arc-shaped inclination angle. The difference in evaporation makes the sidewalls of each reflective retaining wall layer form a certain inclination angle with the vertical direction of the Micro LED micro-display wafer substrate, and the sidewalls are concave inward to form an arc surface. Its structure is as follows Figure 3 As shown, the actual Figure 6 , Figure 7 (Scanning electron microscope images, confocal microscope images).
[0087] The above are only a few embodiments of the present application and do not constitute any form of limitation to the present application. Although the present application is disclosed as above with preferred embodiments, it is not intended to limit the present application. Any technician familiar with the profession, without departing from the scope of the technical solution of the present application, using the technical content disclosed above to make slight changes or modifications are equivalent to equivalent implementation cases and fall within the scope of the technical solution.
Claims
1. A structure for improving the brightness of Micro LED, characterized in that: It includes a high aspect ratio reflective baffle wall disposed in the gap between the pixel light emitting unit matrix; The high aspect ratio reflective baffle wall comprises a substrate adhesive layer, a reflective layer, and a top encapsulation layer stacked from bottom to top; The reflective layer is one metal layer or at least two metal layers with different widths; In any two adjacent metal layers, the bottom end surface size of the metal layer on the side relatively close to the top packaging layer is smaller than the top end surface size of the metal layer on the side relatively far from the top packaging layer; The size of the top end surface of the substrate bonding layer is larger than the size of the bottom end surface of the metal layer adjacent thereto; The bottom end face size of the top encapsulation layer is smaller than the width and smaller than the top end face size of the metal layer adjacent thereto; The high aspect ratio reflective baffle wall has an aspect ratio greater than 5.
2. The structure for improving the brightness of Micro LED according to claim 1, characterized in that: The top end surface dimensions of the substrate bonding layer, the top packaging layer and the metal layer are smaller than the bottom end surface dimensions.
3. The structure for improving the brightness of Micro LED according to claim 1, characterized in that: The side walls of the substrate bonding layer, the top packaging layer and the metal layer are independently a planar structure or an inwardly concave arc surface structure.
4. The structure for improving the brightness of Micro LED according to claim 1, characterized in that: The material of each metal layer is independently selected from at least one of Ti, Al, Pt, Au, Cr, Ag, Cu, Sn, Ti, In, and Bi; The material of the substrate bonding layer is selected from at least one of Cr, Ti, Pt and Au; The material of the top encapsulation layer is selected from Au.
5. The structure for improving the brightness of Micro LED according to claim 1, characterized in that: The thickness of the substrate bonding layer is less than 500 nm; Preferably, the thickness of the reflective layer is less than 10 μm; Preferably, the thickness of the metal layer is less than 100 nm; Preferably, the thickness of the top encapsulation layer is less than 500 nm.
6. The structure for improving the brightness of Micro LED according to claim 1, wherein: The bottom width of the high aspect ratio reflective baffle wall is less than 5 μm; Preferably, the top width of the high aspect ratio reflective blocking wall is less than 1 μm.
7. The method for preparing a structure for improving the brightness of Micro LED according to any one of claims 1 to 6, characterized in that: The steps include: On a substrate containing a pixel light-emitting unit array, a substrate bonding layer, a reflective layer, and a top encapsulation layer are sequentially deposited on the substrate by electron beam evaporation in the vertical space between the pixel light-emitting units using a photoresist mask, thereby forming a high-aspect-ratio reflective baffle located in the gap between the pixel light-emitting unit matrix, thereby obtaining the structure for highly enhancing the brightness of the Micro LED; The steps of making the photoresist mask include: using a negative photoresist to perform photolithography using a mask plate, developing, forming a photoresist mask covering the pixel light-emitting units, and forming gaps for electron beam evaporation in the vertical spaces between the pixel light-emitting units on the photoresist mask; Preferably, the cross-section of the photoresist mask covering the pixel light-emitting unit is an inverted trapezoid.
8. The preparation method according to claim 7, characterized in that: The steps include: S1. On a substrate having an array of pixel light-emitting units, photolithography is performed using a negative photoresist and a mask, and development is performed to form a photoresist mask covering the pixel light-emitting units, and gaps are formed in the vertical spaces between the pixel light-emitting units, and then electron beam evaporation is used to deposit a substrate bonding layer in the gaps, and the photoresist mask is removed; S2, on the substrate processed in step S1, using a negative photoresist and a mask plate to perform photolithography, develop, form a photoresist mask covering the pixel light-emitting units, and form a gap on the upper side of the substrate bonding layer in the vertical space between the pixel light-emitting units, then use electron beam evaporation to deposit a metal layer in the gap, and remove the photoresist mask; S3, forming a reflective layer after step S2 or after step S2 and then after at least one of the following steps: performing photolithography using a negative photoresist and developing the mask to form a photoresist mask covering the pixel light-emitting units, and forming a gap on the upper side of the metal layer formed in the previous step in the vertical space between the pixel light-emitting units, and then using electron beam evaporation to deposit a new metal layer in the gap, and removing the photoresist mask; S4. On the substrate processed in step S3, photolithography is performed using a negative photoresist using a mask template, and development is performed to form a photoresist mask covering the pixel light-emitting units, and a gap is formed on the upper side of the metal layer formed in the previous step in the vertical space between the pixel light-emitting units, and then a top encapsulation layer is deposited in the gap using electron beam evaporation, and the photoresist mask is removed to form a high aspect ratio reflective baffle wall in the gap between the pixel light-emitting unit matrix to obtain the structure that highly enhances the brightness of the Micro LED.
9. The preparation method according to claim 7 or 8, characterized in that: The electron beam evaporation is single-gun electron beam evaporation or double-gun electron beam evaporation; The evaporation source of the double-gun electron beam evaporation is a single source or a double source.
10. The preparation method according to claim 7 or 8, characterized in that: In step S2 to step S4, the photoresist mask covering the pixel light emitting unit independently covers the substrate bonding layer, the metal layer, and part of the edges of the top encapsulation layer, so that the top end surface is not completely exposed in the gap.