Mask design method and micro light emitting diode manufacturing method

Abstract

The present invention relates to a method for designing a mask and a method for preparing a micro light emitting diode, wherein the design method comprises the following steps: establishing a simulation model, wherein the simulation model comprises a GaN epitaxial wafer of a micro light emitting diode and a protective layer, a photoresist layer and a mask located above the GaN epitaxial wafer; the mask comprises a substrate layer and a light shielding layer located on the substrate layer; setting simulation conditions, including the wavelength of an exposure light source, the thickness of each structural layer in the simulation model and the pattern structure of the light shielding layer; performing simulation based on the simulation model and the simulation conditions to obtain the light field distribution received by the photoresist layer after passing through the mask during exposure; changing the pattern structure of the light shielding layer, repeating the simulation, and obtaining the light field distribution again; determining the pattern structure of the light shielding layer corresponding to the optimal light field distribution according to the effect; the pattern structure comprises a main unit and auxiliary units located at one or more corners of the main unit.

Description

Technical Field

[0001] The present invention belongs to the technical field of micro light emitting diodes, and in particular relates to a method for designing a mask in a micro light emitting diode manufacturing process and a method for manufacturing a micro light emitting diode. Background Art

[0002] Light-emitting diodes (LEDs) are currently the most widely used lighting sources, with advantages such as high brightness, long service life, fast response speed, and environmental protection. The combination of semiconductor micro-nano manufacturing technology and LED devices has brought more possibilities to the performance of LEDs. When the size of LEDs is reduced to below 50μm, they can be called micro-light-emitting diodes (Micro-LEDs or μLEDs).

[0003] In the manufacture of Micro-LED, photolithography technology is an indispensable part of the manufacturing process. Photolithography can transfer the pre-made pattern to the photoresist, and then transfer the pattern on the photoresist to the substrate through dry etching and / or wet etching, so as to obtain the desired structure on the substrate.

[0004] However, as the size of Micro-LED continues to decrease, the contact area between the mask and the photoresist becomes smaller, resulting in poor stability of the pattern on the photoresist. If the original preset pattern is a rectangle, the photoresist will form rounded corners on all sides, and this rounded corner effect will be further amplified in the subsequent etching process, causing pattern deformation and affecting the overall quality of the Micro-LED. At the same time, the smaller the size of the Micro-LED, the greater the rounded corner effect and the degree of deformation of the pattern. Although the rounded corner effect can be improved to a certain extent by modifying the photolithography parameters, such as modifying the coating temperature, exposure time, and development time, it cannot solve the problem of rounded corner effect and pattern deformation.

[0005] At the same time, in addition to causing pattern deformation, the rounded corner effect will also cause interference at the edge of the pattern due to the interference between the incident light and the reflected light during exposure, which is called the standing wave effect. The phenomenon is that there will be wavy light and dark stripes at the edge. These stripes will be transferred to the material during etching, making the obtained structure deviate greatly from the original pattern. During the photolithography process, the rounded corner effect caused by scattering and the standing wave effect caused by interference are superimposed at the corners, aggravating the deformation of the pattern after photolithography. Summary of the invention

[0006] The object of the present invention is to provide a design method for a micro light emitting diode mask that can effectively improve the standing wave effect and the deformation of the photolithography pattern in view of the deficiencies in the prior art.

[0007] In order to achieve the above object, the technical solution adopted by the present invention is:

[0008] A method for designing a micro light emitting diode mask comprises the following steps:

[0009] Establishing a simulation model, the simulation model includes a GaN epitaxial wafer of a micro light emitting diode and a protective layer, a photoresist layer and a mask plate located above the GaN epitaxial wafer; the mask plate includes a base layer and a light shielding layer located on the base layer, and the light shielding layer is located between the photoresist layer and the base layer;

[0010] Setting simulation conditions, including the wavelength of the exposure light source, the thickness of each structural layer in the simulation model, and the pattern structure of the light shielding layer;

[0011] Perform simulation based on the simulation model and simulation conditions to obtain the initial light field distribution received by the photoresist layer after passing through the mask during exposure;

[0012] Changing the pattern structure of the shading layer, repeating the simulation, and re-obtaining the optimized light field distribution; determining the pattern structure of the shading layer corresponding to the optimal light field distribution according to the effect;

[0013] The pattern structure includes a main unit and auxiliary units located at one or more corners of the main unit.

[0014] According to some preferred embodiments of the present invention, when changing the pattern structure of the shading layer, taking the boundary of the initial light field distribution as a reference, if the boundary of the optimized light field distribution exceeds the boundary of the initial light field distribution, the size of the auxiliary unit is reduced; if the boundary of the optimized light field distribution is smaller than the boundary of the initial light field distribution, the size of the auxiliary unit is increased.

[0015] According to some preferred implementation aspects of the present invention, the main unit includes a first rectangle, and the auxiliary unit includes a second rectangle, and corners of the second rectangle are in contact with corners of the first rectangle.

[0016] According to some preferred implementation aspects of the present invention, the diagonal line of the first rectangle and the diagonal line of the second rectangle are located on the same straight line.

[0017] According to some preferred implementation aspects of the present invention, a plurality of second rectangles are correspondingly arranged at the corners of each of the main body units; and the sizes of the plurality of second rectangles gradually decrease from approaching the first rectangle to away from the first rectangle.

[0018] According to some preferred implementation aspects of the present invention, the diagonals of the plurality of second rectangles at the corners of each of the main body units are located on the same straight line as the diagonals of the first rectangles.

[0019] According to some preferred implementation aspects of the present invention, the pattern structure of the light shielding layer is changed by dividing the outer corners of the main unit into grids, and filling some squares in the grids to form the auxiliary unit.

[0020] According to some preferred implementation aspects of the present invention, the side length of each square in the grid is 0.001 μm-0.005 μm.

[0021] According to some preferred implementation aspects of the present invention, the side length of the second rectangle is 0.001-0.02 μm.

[0022] According to some preferred implementation aspects of the present invention, the side length of the second rectangle in contact with the corner of the first rectangle is 0.01-0.02 μm; the side length of the remaining second rectangle is 0.001-0.01 μm.

[0023] The present invention also provides a mask designed based on the above design method, a method for preparing a micro light emitting diode including the above design method, and the prepared micro light emitting diode.

[0024] Due to the application of the above-mentioned technical scheme, the present invention has the following advantages compared with the prior art: the design method of the micro-light-emitting diode mask of the present invention, by changing the pattern structure of the shading layer, makes the pattern structure include a main unit and an auxiliary unit located at one or more corners of the main unit, thereby effectively improving the standing wave effect and the deformation of the pattern, and improving the rounded corner effect to a certain extent. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following briefly introduces the drawings required for use in the description of the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0026] Figure 1 It is a schematic diagram of the simulation model structure established in the preferred embodiment of the present invention;

[0027] Figure 2a A diagram showing simulation results based on a mask pattern structure having only the first rectangle in a preferred embodiment of the present invention;

[0028] Figure 2b for Figure 2a A partial enlarged view of

[0029] Figure 3 A schematic diagram of a mask pattern structure including a main unit and an auxiliary unit in a preferred embodiment of the present invention;

[0030] Figure 4 It is a schematic diagram of the structure of dividing the grid outside the corners of the main unit in the preferred embodiment of the present invention;

[0031] Figure 5 It is a schematic structural diagram of an auxiliary unit with a side length of 0.02 μm added outside the corner of the main unit in a preferred embodiment of the present invention;

[0032] Figure 6a For the corresponding Figure 5 A simulation result diagram after simulating the mask pattern;

[0033] Figure 6b for Figure 6a A partial enlarged view of

[0034] Figure 7 It is a schematic structural diagram of an auxiliary unit with a side length of 0.01 μm added outside the corner of the main unit in a preferred embodiment of the present invention;

[0035] Figure 8a For the corresponding Figure 7 A simulation result diagram after simulating the mask pattern;

[0036] Figure 8b for Figure 8a A partial enlarged view of

[0037] Fig. 9 It is a schematic structural diagram of adding auxiliary units with side lengths of 0.01 μm and 0.005 μm outside the corners of the main unit in a preferred embodiment of the present invention;

[0038] Fig.10a For the corresponding Fig. 9 A simulation result diagram after simulating the mask pattern;

[0039] Fig.10b for Fig.10a A partial enlarged view of

[0040] Fig.11 is a schematic diagram of the mask pattern structure in Example 2;

[0041] Among them, the figure markings are: SiO2 base layer-1, Cr shading layer-2, photoresist layer-3, SiO2 protective layer-4, GaN layer-5, sapphire substrate layer-6, main unit-7, auxiliary unit-8. DETAILED DESCRIPTION

[0042] In order to enable those skilled in the art to better understand the scheme of the present invention, the technical scheme in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work should fall within the scope of protection of the present invention.

[0043] Embodiment 1 Design method of micro light emitting diode mask

[0044] Since the rounded corner effect and standing wave effect will cause pattern deformation, and it cannot be eliminated by improving the process conditions, in order to improve this problem, this embodiment provides a design method for a micro-light-emitting diode mask, by changing the prefabricated pattern structure on the mask, and obtaining the expected pattern after photolithography. The design method uses FDTD to simulate the Micro-LED structure and provides the corresponding simulation structure and simulation results.

[0045] Specifically, the design method of the micro light emitting diode mask of this embodiment includes the following steps:

[0046] Step 1: Build a simulation model

[0047] like Figure 1 As shown, GaN epitaxial wafers are usually grown on sapphire substrates. This embodiment establishes a simulation model of GaN epitaxial wafers based on FDTD, and on this basis, adds a SiO2 protective layer 4, a photoresist layer 3 and a mask. The mask includes a SiO2 substrate layer 1 and a Cr light shielding layer 2 located on the SiO2 substrate layer 1, and the Cr light shielding layer 2 is located between the photoresist layer 3 and the SiO2 substrate layer 1. The pattern design of the mask is to design the number and position of the Cr light shielding layer 2 on the SiO2 substrate layer 1.

[0048] The simulation model established in this embodiment includes, from top to bottom, a SiO2 base layer 1, a Cr light shielding layer 2, a photoresist layer 3, a SiO2 protective layer 4, a GaN layer 5 and a sapphire substrate layer 6.

[0049] Among them, the SiO2 base layer 1 and the Cr light shielding layer 2 constitute a mask, the SiO2 base layer 1 is the mask substrate, and Cr is the mask light shielding material. During ultraviolet exposure, the light beam passes through the SiO2 base layer 1, the light beam is blocked in the area with Cr, and the light beam passes through the area without Cr and irradiates the PR (photoresist). Then, through development, the exposed area of ​​the photoresist is dissolved, and the unexposed area is retained, thereby realizing the transfer of the pattern.

[0050] The SiO2 protective layer 4 is used as a hard mask during etching. The photoresist used in this embodiment has a thickness of 500nm, which cannot meet the subsequent etching requirements of 1.2μmGaN. Therefore, 200nm SiO2 is used as a hard mask in the middle to meet the etching requirements of GaN.

[0051] The GaN layer 5 is the Micro-LED structure area, which includes p-GaN, quantum wells and n-GaN. Since the quantum well is an alternating structure of InGaN and GaN, and the refractive index is not much different, GaN is used to replace the entire Micro-LED in the simulation.

[0052] The sapphire substrate layer 6 is the substrate material of the GaN epitaxial wafer.

[0053] Step 2: Set simulation conditions

[0054] The simulation conditions include the wavelength of the light source used for exposure, the thickness of each structural layer in the simulation model, and the pattern structure of the light shielding layer 2 .

[0055] In the FDTD simulation, a plane wave with a wavelength of 365nm is used as the light source to simulate the UV exposure situation, and the boundary condition of the simulation area is set to Periodic to simulate the light emission of the Micro-LED array.

[0056] The thickness of each structural layer is: SiO2 base layer 1 is infinite, Cr light shielding layer 2 is 1μm, photoresist layer 3 is 500nm, SiO2 protection layer 4 is 200nm, GaN layer 5 is 3μm, and sapphire substrate layer 6 is infinite.

[0057] Set up five monitors at the same time, namely: E xy -1, E xy 、E xy -2. E xz and E yz , where E xy -1 is set on the top of the xy plane of the photoresist layer 3, E xy Set in the middle of the xy plane of the photoresist layer 3, E xy -2 is set at the bottom of the xy plane of the photoresist layer 3, E xz Set in the middle of the xz plane, E yz Set in the middle of the yz plane. xy -1, E xy 、E xy -2 Three monitors are used to monitor the XY plane, respectively monitoring the top, middle and bottom of the photoresist layer 3. The morphology of the XY plane of the photoresist layer 3 can be obtained from the results of these three monitors; E xz and E yzThe monitor monitors the changes of the photoresist layer 3 in the XZ and YZ vertical planes respectively to verify the standing wave effect.

[0058] Step 3: Simulation

[0059] A simulation is performed based on the pattern structure of the initial light shielding layer 2 , the simulation model and the simulation conditions to obtain the initial light field distribution received by the photoresist layer 3 after passing through the mask during exposure.

[0060] The pattern structure of the initial conventional light shielding layer 2 only includes the main unit 7 of the first rectangle, which is the mask pattern in the simulation in this step. The first rectangle is a square with a side length of 10 μm. The simulation results are as follows: Figure 2a and Figure 2b As shown in the figure, the horizontal and vertical coordinates are the set simulation area, and the area of ​​-5~5μm is the actual lithography area. The blue area in the simulation result exceeds -5~5μm because the diffraction of light causes the actual shading area size to be larger than the mask size, which is a normal phenomenon.

[0061] The blue area in the simulation results corresponds to the blocked area of ​​the Cr blocking layer on the mask. From the simulation results, we can see that the corners of the shading area will change from the original square right angles to rounded corners due to the diffraction of light, which is the rounded corner effect. At the same time, the corners appear in a wavy shape with alternating light and dark. This is because the incident light and the reflected light interfere with each other to form standing waves, which is the standing wave effect. Figure 2a and Figure 2b It can be seen that the edge deformation of the blue area is serious.

[0062] That is, the initial light field distribution received by the photoresist layer 3 in the shielding area of ​​the Cr light shielding layer 2 in the conventional mask pattern having only the first rectangular main body unit 7 will produce obvious rounded corner effect, standing wave effect and pattern deformation.

[0063] Step 4: Change the pattern structure of the light shielding layer 2, repeat the above simulation, and obtain the optimal pattern structure of the light shielding layer 2

[0064] By changing the pattern structure of the shading layer 2 and repeating the simulation, the optimized light field distribution received by the photoresist layer 3 after passing through the mask during exposure is obtained again; the pattern structure of the shading layer 2 corresponding to the optimal light field distribution is determined according to the effect of the light field distribution.

[0065] Specifically, the pattern structure of the light shielding layer 2 in this step is provided with an auxiliary unit 8 at one or more corners of the main unit 7 of the first rectangle, the auxiliary unit 8 is a second rectangle, the corners of the second rectangle are in contact with the corners of the first rectangle, and the size of the second rectangle is smaller than the first rectangle, and the side length of the second rectangle is 0.001-0.02 μm, such as Figure 3In this embodiment, the pattern structure of the light shielding layer 2 includes a main unit 7 and auxiliary units 8 located at four corners of the main unit 7, and the diagonal line of the first rectangle of the main unit 7 and the diagonal line of the second rectangle of the auxiliary unit 8 are located on the same straight line.

[0066] Preferably, when changing the pattern structure of the light shielding layer 2, a certain area is extended outward from the corners of the main unit 7 and divided into grids, and some of the squares in the grid are filled to form the auxiliary unit 8, and the number and position of the squares in the filled grid are changed, such as Figure 4 , 5 As shown in , 7, and 9, the side length of each square in the grid is 0.001μm-0.005μm, and 0.005μm is preferred in this embodiment. The pattern after photolithography is simulated step by step, and finally a filling pattern with the smallest standing wave effect and the smallest deformation is obtained, which is the optimal pattern structure of the light shielding layer 2. The following steps can be followed:

[0067] (i) Add a second rectangle with a side length of 0.02 μm at the four corners of the main unit 7 to form an auxiliary unit 8, such as Figure 5 The simulation results are shown in Figure 6a and Figure 6b shown.

[0068] according to Figure 6a and Figure 6b From the simulation results, we can see that after adding the second rectangular structure of 0.02μm to the four corners of the main unit 7, the corrugated area at the corners is reduced and the corrugation of the corners is improved, indicating that adding auxiliary structures to the corners of the main unit 7 can significantly reduce the impact of the standing wave effect, and at the same time the deformation is significantly reduced. However, there is a tendency to extend outward as a whole, because the blue area represents the actual photolithography pattern. The purpose of the present invention is to correct the inward contraction of the photolithography pattern at the corners caused by the interference diffraction of light during the exposure process. If the blue area extends outward, it means that the corner area is over-corrected, indicating that the second rectangular structure added at the corner is too large.

[0069] (ii) Add a second rectangle with a side length of 0.01 μm at the four corners of the main unit 7 to form an auxiliary unit 8, such as Figure 7 The simulation results are shown in Figure 8a and Figure 8b shown.

[0070] Based on the size of the auxiliary unit 8 in (a) and the simulation results, the size of the second rectangle on the corner was reduced to a 0.01 μm square.

[0071] from Figure 8a and Figure 8bIt can be seen from the simulation results that, compared with the mask without the auxiliary unit 8 structure in step three, the rounded corner effect is significantly improved, the corner is closer to a square, and the corrugated area at the edge is reduced, and the standing wave effect is improved. However, from the simulation results, there are still ripples at the corners.

[0072] (III) A plurality of second rectangles are provided at the corners of each main body unit 7; the sizes of the plurality of second rectangles gradually decrease from the direction close to the first rectangle to the direction away from the first rectangle. The side length of the second rectangle in contact with the corner of the first rectangle is 0.01-0.02 μm; the side length of the remaining second rectangles is 0.001-0.01 μm. The diagonals of the plurality of second rectangles at the corners of each main body unit 7 are located on the same straight line as the diagonals of the first rectangle.

[0073] Specifically, since the corners of the 0.01μm structure simulation result still have rounded corners, and the 0.02μm structure simulation result obviously exceeds the original square, based on the previous simulation results, the number of filled squares is reduced and changed to fill squares of 0.01μm plus 0.005μm, as shown in the schematic diagram Fig. 9 The simulation results are shown in Fig.10a and Fig.10b shown.

[0074] according to Fig.10a and Fig.10b From the simulation results, it can be seen that in the simulation results of the auxiliary unit 8 structure of the second rectangle of 0.01μm plus 0.005μm, the rounded corner effect of the square is improved to a certain extent, but the rounded corner effect is related to the light source and the mask material. Generally, the light source of photolithography is ultraviolet light and the mask material is chromium, which cannot be changed too much. Therefore, the rounded corner effect can only be improved to a certain extent and cannot be eliminated. At the same time, from the simulation results, the corner corrugation is significantly reduced, indicating that the method in this embodiment can effectively improve the influence of the standing wave effect on photolithography, and the deformation of the pattern is significantly reduced.

[0075] It can be seen from the above (1)-(3) that when changing the pattern structure of the shading layer, taking the boundary of the initial light field distribution as a reference, if the boundary of the optimized light field distribution exceeds the boundary of the initial light field distribution, the size of the auxiliary unit is reduced; if the boundary of the optimized light field distribution is smaller than the boundary of the initial light field distribution, the size of the auxiliary unit is increased.

[0076] This embodiment also provides a method for preparing a micro light emitting diode including the above design method and the prepared micro light emitting diode.

[0077] Based on the influence of the standing wave effect and the rounded corner effect, the design method of the micro-light emitting diode mask in the present invention changes the pattern of the shading area so that the pattern structure includes a main unit 7 and an auxiliary unit 8 located at one or more corners of the main unit 7, thereby effectively improving the standing wave effect and the deformation of the pattern, and improving the rounded corner effect to a certain extent.

[0078] Example 2 Micro-light emitting diode mask

[0079] like Figure 3-Figure 5 , Figure 7 , Fig. 9 , Fig.11 As shown, this embodiment provides a micro-LED mask based on the design obtained in Embodiment 1. The mask includes a base layer 1 and a light shielding layer 2 located on the base layer 1. When the mask is in use, the light shielding layer 2 is located between the photoresist layer 3 and the base layer 1. The light shielding layer 2 is formed by a plurality of Cr materials regularly distributed on the base layer 1 to form a pattern structure.

[0080] In this embodiment, the pattern structure of the mask light shielding layer 2 includes a main unit 7 and an auxiliary unit 8 located at one or more corners of the main unit 7. The main unit 7 includes a first rectangle, and the auxiliary unit 8 includes a second rectangle, and the corners of the second rectangle are in contact with the corners of the first rectangle. The size of the second rectangle is smaller than the first rectangle, and the side length of the second rectangle is 0.001-0.02 μm, such as Figure 3 shown.

[0081] That is, the pattern structure includes a main unit 7 and auxiliary units 8 located at the four corners of the main unit 7, and preferably, the diagonal line of the first rectangle of the main unit 7 and the diagonal line of the second rectangle of the auxiliary unit 8 are located on the same straight line.

[0082] Preferably, a plurality of second rectangles are correspondingly arranged at the corners of each main body unit 7; and the sizes of the plurality of second rectangles gradually decrease from close to the first rectangle to away from the first rectangle. Fig. 9 As shown, in this embodiment, the side length of the second rectangle in contact with the corner of the first rectangle is 0.01-0.02μm; the side length of the remaining second rectangles is 0.001-0.01μm. And the diagonal lines of the multiple second rectangles at the corners of each main unit 7 are located on the same straight line as the diagonal lines of the first rectangle. In this embodiment, it is preferred that the side length of the first rectangle is 10μm, the side length of the second rectangle in contact with the side length of the first rectangle is 0.01μm, and another second rectangle with a side length of 0.005μm is provided on the side of the second rectangle away from the first rectangle, as shown in FIG. Fig. 9 shown.

[0083] Fig.11The figure shows a schematic diagram of a 3*3 array mask, wherein the dark area is the metal Cr light shielding layer 2, the side length of the first rectangle in the dark area is 10 μm, and the interval between two adjacent main units is 15 μm. Fig.11 Because the second rectangle is too small and its ratio to the first rectangle is too different, Fig.11 The second rectangle cannot be displayed in the figure, and the first rectangle and the second rectangle in other figures are also for structural illustration and are not actual sizes.

[0084] The above embodiments are only for illustrating the technical concept and features of the present invention, and their purpose is to enable people familiar with this technology to understand the contents of the present invention and implement them accordingly. They cannot be used to limit the protection scope of the present invention. Any equivalent changes or modifications made according to the spirit of the present invention should be included in the protection scope of the present invention.

[0085] The endpoints and any values ​​of the ranges disclosed in this article are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of each range, the endpoint values ​​of each range and the individual point values, and the individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed in this article.

Claims

1. A method for designing a mask, characterized in that: The steps include: Establishing a simulation model, the simulation model includes a GaN epitaxial wafer of a micro light emitting diode and a protective layer, a photoresist layer and a mask plate located above the GaN epitaxial wafer; the mask plate includes a base layer and a light shielding layer located on the base layer, and the light shielding layer is located between the photoresist layer and the base layer; Setting simulation conditions, including the wavelength of the exposure light source, the thickness of each structural layer in the simulation model, and the pattern structure of the light shielding layer; Perform simulation based on the simulation model and simulation conditions to obtain the initial light field distribution received by the photoresist layer after passing through the mask during exposure; Changing the pattern structure of the shading layer, repeating the simulation, and re-obtaining the optimized light field distribution; determining the pattern structure of the shading layer corresponding to the optimal light field distribution according to the effect; The pattern structure includes a main unit and auxiliary units located at one or more corners of the main unit; When changing the pattern structure of the shading layer, taking the boundary of the initial light field distribution as a reference, if the boundary of the optimized light field distribution exceeds the boundary of the initial light field distribution, the size of the auxiliary unit is reduced; if the boundary of the optimized light field distribution is smaller than the boundary of the initial light field distribution, the size of the auxiliary unit is increased.

2. The design method according to claim 1, characterized in that: The main unit includes a first rectangle, and the auxiliary unit includes a second rectangle, and corners of the second rectangle are in contact with corners of the first rectangle.

3. The design method according to claim 2, characterized in that: The diagonal line of the first rectangle and the diagonal line of the second rectangle are located on the same straight line.

4. The design method according to claim 2, characterized in that: A plurality of second rectangles are correspondingly arranged at the corners of each main body unit; the sizes of the plurality of second rectangles gradually decrease from being close to the first rectangle to being away from the first rectangle.

5. The design method according to claim 4, characterized in that: The diagonals of the plurality of second rectangles at the corners of each of the main body units are located on the same straight line as the diagonals of the first rectangles.

6. The design method according to claim 2, characterized in that: The pattern structure of the light shielding layer is changed by dividing the outer corners of the main unit into grids, and filling some squares in the grids to form the auxiliary unit.

7. The design method according to claim 6, characterized in that: The side length of each square in the grid is 0.001 μm-0.005 μm.

8. The design method according to claim 6, characterized in that: The side length of the second rectangle is 0.001-0.02 μm.

9. The design method according to claim 8, characterized in that: The side length of the second rectangle in contact with the corner of the first rectangle is 0.01-0.02 μm; the side length of the remaining second rectangle is 0.001-0.01 μm.

10. A method for preparing a micro light emitting diode comprising the design method steps as described in any one of claims 1 to 9.

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