Miniature light emitting diode mask plate

Abstract

The utility model relates to a miniature light emitting diode mask plate, the mask plate comprises a base body layer and a shading layer located on the base body layer, and the shading layer comprises a main body unit and auxiliary units located at one or more corners of the main body unit. According to the micro light-emitting diode mask plate, the auxiliary units are arranged at the corners of the main body units of the pattern structure of the shading layer, so that the standing wave effect and the pattern deformation are effectively improved, and the fillet effect is improved to a certain extent.

Description

TECHNICAL FIELD

[0001] The utility model belongs to the technical field of micro light emitting diode and mask plate, specifically relates to a mask plate used in the preparation of micro light emitting diode. BACKGROUND

[0002] Light emitting diode (LED) is the most widely used lighting source at present, has high brightness, long service life, fast response speed, environmental protection and other advantages. The combination of semiconductor micro-nano manufacturing technology and LED device brings more possibilities for the performance of LED. When the size of LED is reduced to below 50 μm, it can be called micro light emitting diode (Micro-LED or μLED).

[0003] In the manufacture of Micro-LED, photolithography technology is an essential link in the manufacturing process. Photolithography can transfer the pre-prepared 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 of the mask plate and the photoresist becomes smaller, resulting in poor stability of the pattern on the photoresist. For example, if the original preset pattern is a rectangle, the photoresist will form a rounded corner around it, and this rounding effect will be further amplified in the subsequent etching process, causing the pattern to deform and affecting the overall quality of the Micro-LED. At the same time, the smaller the size of the Micro-LED, the greater the degree of rounding effect and pattern deformation. Although the rounding effect can be improved to some extent by modifying the photolithography parameters, such as modifying the uniformity temperature, exposure time, development time, etc., it cannot completely solve the problem of rounding effect and pattern deformation.

[0005] At the same time, in addition to the problem of pattern deformation caused by the rounding effect, the incident light and reflected light during exposure will produce interference, resulting in an interference effect at the edge of the pattern, known as the standing wave effect. The phenomenon is that there are wavy light and dark stripes at the edge. These stripes will be transferred to the material during etching, resulting in a large deviation between the obtained structure and the original pattern. The rounding effect caused by scattering and the standing wave effect caused by interference are superimposed in the corners during the photolithography process, which aggravates the deformation of the pattern after photolithography. SUMMARY

[0006] Therefore, in order to overcome the defects of the prior art, the utility model provides a mask plate used in the preparation of micro light emitting diode, which can improve the rounding effect and the standing wave effect.

[0007] In order to achieve the above-mentioned purpose, the utility model adopts the following technical scheme:

[0008] A micro light emitting diode mask plate, the mask plate comprises a substrate layer and a light shielding layer on the substrate layer, the light shielding layer comprises a main unit and an auxiliary unit at one or more corners of the main unit.

[0009] According to some preferred embodiments of the utility model, the main unit comprises a first rectangle, the auxiliary unit comprises a second rectangle, and the corner of the second rectangle is in contact with the corner of the first rectangle.

[0010] According to some preferred embodiments of the utility model, the diagonal of the first rectangle and the diagonal of the second rectangle are on the same straight line.

[0011] According to some preferred embodiments of the utility model, a plurality of second rectangles are arranged at the corner of each main unit correspondingly, and the size of the plurality of second rectangles gradually decreases from the direction close to the first rectangle to the direction away from the first rectangle.

[0012] According to some preferred embodiments of the utility model, the diagonal of the plurality of second rectangles at the corner of each main unit is on the same straight line with the diagonal of the first rectangle.

[0013] According to some preferred embodiments of the utility model, the side length of the first rectangle is 8-15 μm, and the side length of the second rectangle is 0.001-0.02 μm.

[0014] According to some preferred embodiments of the utility model, the side length of the second rectangle in contact with the corner of the first rectangle is 0.01-0.02 μm, and the side length of the remaining second rectangle is 0.001-0.01 μm.

[0015] According to some preferred embodiments of the utility model, the light shielding layer comprises a plurality of main units, and the plurality of main units are uniformly distributed on the substrate layer.

[0016] Compared with the prior art, the micro light emitting diode mask plate of the utility model effectively improves the standing wave effect and the deformation of the pattern, and improves the round corner effect to a certain extent. BRIEF DESCRIPTION OF DRAWINGS

[0017] In order to more clearly illustrate the technical scheme in the embodiments of the utility model, the drawings needed to be used in the embodiment description will be briefly introduced below, and obviously, the drawings in the following description are only some embodiments of the utility model, and other drawings can be obtained by those skilled in the art without creative labor on the premise of not paying.

[0018] Figure 1 A simulation model structure schematic diagram established in the preferred embodiment of the utility model;

[0019] Figure 2a A simulation result diagram after simulation of the mask plate pattern corresponding to

[0020] Figure 2b A partial enlarged view of Figure 2a ;

[0021] Figure 3 A mask plate pattern structure schematic diagram containing a main unit and an auxiliary unit in the preferred embodiment of the utility model;

[0022] Figure 4 A structure schematic diagram in which a grid is divided outside the corner of the main unit in the preferred embodiment of the utility model;

[0023] Figure 5 A structure schematic diagram in which an auxiliary unit with a side length of 0.02μm is added outside the corner of the main unit in the preferred embodiment of the utility model;

[0024] Figure 6a A simulation result diagram after simulation of the mask plate pattern corresponding to Figure 5 ;

[0025] Figure 6b A partial enlarged view of Figure 6a ;

[0026] Figure 7 A structure schematic diagram in which an auxiliary unit with a side length of 0.01μm is added outside the corner of the main unit in the preferred embodiment of the utility model;

[0027] Figure 8a A simulation result diagram after simulation of the mask plate pattern corresponding to Figure 7 ;

[0028] Figure 8b A partial enlarged view of Figure 8a ;

[0029] Figure 9 A structure schematic diagram in which auxiliary units with side lengths of 0.01μm and 0.005μm are added outside the corner of the main unit in the preferred embodiment of the utility model;

[0030] Figure 10a A simulation result diagram after simulation of the mask plate pattern corresponding to Figure 9 ;

[0031] Figure 10b A partial enlarged view of Figure 10a ;

[0032] Figure 11 A schematic diagram of the mask plate pattern structure in Example 2;

[0033] Wherein, the reference signs are: SiO2 base layer-1, Cr light shielding layer-2, photoresist layer-3, SiO2 protective layer-4, GaN layer-5, sapphire substrate layer-6, main unit-7, auxiliary unit-8. DETAILED DESCRIPTION

[0034] In order to make the person skilled in the art better understand the technical scheme of the present application, the technical scheme in the embodiments of the present application will be described clearly and completely below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by the person skilled in the art without creative labor should belong to the scope of protection of the present application.

[0035] Design method of micro light emitting diode mask plate

[0036] Due to the round corner effect and standing wave effect, the pattern will be deformed, and it is also impossible to eliminate by improving the process conditions. In order to improve the problem, the present embodiment provides a design method of micro light emitting diode mask plate, which changes the pattern structure prepared on the mask plate, and obtains the expected pattern after lithography. The design method uses FDTD to simulate the Micro-LED structure, and provides the corresponding simulation structure and simulation results.

[0037] Specifically, the design method of micro light emitting diode mask plate of the present embodiment includes the following steps:

[0038] Step one, establish a simulation model

[0039] As shown in Figure 1 GaN epitaxial wafer is usually grown on a sapphire substrate, and the present embodiment establishes a simulation model of GaN epitaxial wafer based on FDTD, and adds SiO2 protective layer 4, photoresist layer 3 and mask plate on this basis. The mask plate includes SiO2 base layer 1 and Cr light shielding layer 2 located on SiO2 base layer 1, and Cr light shielding layer 2 is located between photoresist layer 3 and SiO2 base layer 1. The pattern design of the mask plate is to design the number and position of Cr light shielding layer 2 on SiO2 base layer 1.

[0040] The simulation model established in the present embodiment is SiO2 base layer 1, Cr light shielding layer 2, photoresist layer 3, SiO2 protective layer 4, GaN layer 5 and sapphire substrate layer 6 from top to bottom.

[0041] Wherein, the SiO2 substrate layer 1 and the Cr light shielding layer 2 constitute a mask plate, the SiO2 substrate layer 1 is a mask plate substrate, and the Cr is a mask plate light shielding material. During ultraviolet exposure, the light beam passes through the SiO2 substrate layer 1, the light beam is blocked in the area with Cr, the light beam passes through in the area without Cr, and is irradiated onto the PR (photoresist), and then through development, the exposed area of the photoresist is dissolved, and the unexposed area is reserved, so as to realize the transfer of the pattern.

[0042] The SiO2 protective layer 4 is used as a hard mask during etching, the photoresist used in the embodiment has a thickness of 500 nm, which cannot meet the etching requirement of 1.2 μm GaN in the subsequent etching, so 200 nm SiO2 is used as a hard mask in the middle to meet the etching requirement of GaN.

[0043] The GaN layer 5 is a Micro-LED structure area, which includes p-GaN, quantum well and n-GaN, and since the quantum well is an alternating structure of InGaN and GaN and the refractive index difference is not large, GaN is used to replace the entire Micro-LED in the simulation.

[0044] The sapphire substrate layer 6 is a substrate material of the GaN epitaxial wafer.

[0045] Step two, set the simulation conditions

[0046] The simulation conditions include the wavelength of the exposure light source, the thickness of each structure layer in the simulation model and the pattern structure of the light shielding layer 2.

[0047] In the FDTD simulation, a plane wave with a wavelength of 365 nm is used as a light source to simulate the ultraviolet exposure, and the boundary condition of the simulation area is set to Periodic (periodic boundary) to simulate the light emission of the Micro-LED array.

[0048] The thickness of each structure layer is as follows: the SiO2 substrate layer 1 is infinite, the Cr light shielding layer 2 is 1 μm, the photoresist layer 3 is 500 nm, the SiO2 protective layer 4 is 200 nm, the GaN layer 5 is 3 μm, and the sapphire substrate layer 6 is infinite.

[0049] Five monitors are set, which are E xy -1, E xy , E xy -2, E xz and E yz , wherein E xy -1 is set at the top of the xy plane of the photoresist layer 3, E xy is 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 is set in the middle of the xz plane, and Eyz Set in the middle of the yz plane. Where E xy -1, E xy , E xy -2 three monitors for monitoring the XY plane, respectively, monitor the top, middle and bottom of the photoresist layer 3, the results of the three monitors can be obtained from the XY plane of the photoresist layer 3 topography;E xz and E yz Monitor the changes in the XZ and YZ vertical plane photoresist layer 3, verify the standing wave effect.

[0050] Step three, simulation

[0051] Based on the initial light shielding layer 2 pattern structure, simulation model and simulation conditions for simulation, the initial light field distribution received by the photoresist layer 3 after exposure through the mask plate.

[0052] The initial pattern structure of the conventional light shielding layer 2 only includes the first rectangular main unit 7, which is the mask pattern in this step for simulation, the first rectangle is a square with a side length of 10 μm, and the simulation results are shown in Figure 2a and Figure 2b , wherein the horizontal and vertical coordinate ranges are the simulation area set, and the area of -5 ~ 5 μm is the actual photoetching area. The blue area in the simulation result is beyond -5 ~ 5 μm because the actual light shielding area size is larger than the mask size due to light diffraction, which is a normal phenomenon.

[0053] The blue area in the simulation result corresponds to the shielding area of the Cr shielding layer on the mask plate. As can be seen from the simulation result, the corners of the shielding area will change from the original square right angle to round angle due to light diffraction, that is, the round angle effect, and the bright and dark alternating ripples appear in the corners, which is due to the interference between the incident light and the reflected light, forming a standing wave, that is, the standing wave effect, and Figure 2a and Figure 2b It can be seen that the edge of the blue area is severely deformed.

[0054] That is, the initial light field distribution received by the photoresist layer 3 corresponding to the shielding area of the Cr light shielding layer 2 of the mask pattern with only the first rectangular main unit 7 of the conventional mask pattern will produce obvious round angle effect, standing wave effect and pattern deformation.

[0055] Step four, change the pattern structure of the light shielding layer 2, repeat the above simulation, and get the optimal pattern structure of the light shielding layer 2

[0056] By changing the pattern structure of the light shielding layer 2, repeating the simulation, the optimized light field distribution received by the photoresist layer 3 after exposure through the mask plate is obtained again; according to the effect of the light field distribution, the pattern structure of the light shielding layer 2 corresponding to the optimal light field distribution is determined.

[0057] Specifically, the pattern structure of the light-shielding layer 2 in this step is to set auxiliary units 8 at one or more corners of the main unit 7 of the first rectangle, the auxiliary units 8 being second rectangles, the corners of the second rectangles being in contact with the corners of the first rectangle, and the size of the second rectangle being smaller than that of the first rectangle, the side length of the second rectangle being 0.001-0.02 μm, as shown in Figure 3 The pattern structure of the light-shielding layer 2 in this embodiment includes the main unit 7 and the auxiliary units 8 at the four corners of the main unit 7, and the diagonal of the first rectangle of the main unit 7 and the diagonal of the second rectangle of the auxiliary unit 8 are on the same straight line.

[0058] Preferably, when the pattern structure of the light-shielding layer 2 is changed, a certain area extending outward from the corners of the main unit 7 is divided into a grid, and some of the squares in the grid are filled to form the auxiliary units 8, by changing the number and position of the filled squares in the grid, as shown in Figure 4 , 5 , 7, 9, the side length of each square in the grid is 0.001-0.005 μm, and 0.005 μm is preferred in this embodiment. The pattern after lithography is simulated step by step, and finally the 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 taken:

[0059] (I) A second rectangle with a side length of 0.02 μm is added at the four corners of the main unit 7 to form the auxiliary unit 8, as shown in Figure 5 The simulation results are shown in Figure 6a and Figure 6b .

[0060] From the simulation results of Figure 6a and Figure 6b , it can be seen that after the second rectangle structure with a side length of 0.02 μm is added at the four corners of the main unit 7, the corrugated area at the corners is reduced, and the corrugated shape at the corners is improved, indicating that adding auxiliary structures at the corners of the main unit 7 can significantly reduce the influence of standing wave effect, and the deformation is significantly reduced. However, there is a tendency to extend outward as a whole, because the blue area represents the actual lithography pattern, and the purpose of this application is to correct the inward shrinkage of the lithography pattern at the corners due to the interference and diffraction of light during exposure. If the blue area extends outward, it indicates that the correction at the corner area is excessive, indicating that the second rectangle structure added at the corner is too large.

[0061] (II) A second rectangle with a side length of 0.01 μm is added at the four corners of the main unit 7 to form the auxiliary unit 8, as shown in Figure 7 The simulation results are shown in Figure 8a and Figure 8b .

[0062] Based on the size of the auxiliary unit 8 in (1) and the simulation results, the size of the second rectangle on the corner is reduced to 0.01 μm square.

[0063] From Figure 8a and Figure 8b The simulation results show that, compared with the mask plate without the auxiliary unit 8 structure in step three, the corner rounding effect is obviously improved, the corner is closer to a square than without the auxiliary unit 8 structure, and the edge wave-shaped area is reduced, and the standing wave effect is improved, but at the same time, from the simulation results, there are still waves at the corner.

[0064] (Three) A plurality of second rectangles are arranged at the corners of each main unit 7; the size of the plurality of second rectangles gradually decreases from the direction close to the first rectangle to the direction away from the first rectangle. Among them, 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. The diagonal lines of the plurality of second rectangles at the corners of each main unit 7 are on the same straight line as the diagonal lines of the first rectangle.

[0065] Specifically, since the corner of the 0.01 μm structure simulation result still has a rounding, and the 0.02 μm structure simulation result obviously exceeds the original square, based on the previous simulation results, the number of filled squares is reduced, and 0.01 μm plus 0.005 μm squares are filled, the schematic diagram is shown in Figure 9 , and the simulation results are shown in Figure 10a and Figure 10b .

[0066] According to the simulation results of Figure 10a and Figure 10b , it can be seen that in the simulation results of the auxiliary unit 8 structure of the second rectangle of 0.01 μm plus 0.005 μm, the rounding effect of the square is improved to a certain extent, but the rounding effect is related to the light source and the mask material. Generally, the light source for photolithography is ultraviolet light, and the mask material is chromium, which cannot be changed too much, so the rounding effect can only be improved to a certain extent and cannot be eliminated. At the same time, from the simulation results, it can be seen that the corner wave is significantly reduced, which shows that the method in the embodiment can effectively improve the influence of the standing wave effect on photolithography, and the deformation of the pattern is obviously reduced.

[0067] From the above (1)-(3), it can be seen that when changing the pattern structure of the light shielding layer, the boundary of the initial light field distribution is taken as the benchmark, 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.

[0068] The embodiment also provides a preparation method of a micro light emitting diode including the design method.

[0069] Based on the influence of standing wave effect and round corner effect, the design method of the micro light emitting diode mask plate in the application effectively improves the standing wave effect and the deformation of the pattern by changing the pattern of the light shielding area, and improves the round corner effect to some extent.

[0070] Example 2 micro light emitting diode mask plate

[0071] As shown in Figures 3-5 , Figure 7 , Figure 9 , Figure 11 The embodiment provides a micro light emitting diode mask plate based on the design obtained in example 1. The mask plate includes a substrate layer 1 and a light shielding layer 2 on the substrate layer 1. When the mask plate is used, the light shielding layer 2 is located between the photoresist layer 3 and the substrate layer 1. The light shielding layer 2 is formed by a plurality of Cr materials regularly distributed on the substrate layer 1 to form a pattern structure.

[0072] In this embodiment, the pattern structure of the mask plate 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, the auxiliary unit 8 includes a second rectangle, and the corners of the second rectangle contact the corners of the first rectangle. The size of the second rectangle is smaller than that of the first rectangle, and the side length of the second rectangle is 0.001-0.02μm, as shown in Figure 3 .

[0073] That is, the pattern structure includes a main unit 7 and an auxiliary unit 8 located at 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.

[0074] Preferably, a plurality of second rectangles are arranged at the corners of each main unit 7; and the size of the plurality of second rectangles gradually decreases from the direction close to the first rectangle to the direction away from the first rectangle. As shown in Figure 9 , in this embodiment, the side length of the second rectangle contacting the corner of the first rectangle is 0.01-0.02μm; the side length of the remaining second rectangle is 0.001-0.01μm. And the diagonal line of the plurality of second rectangles at the corners of each main unit 7 is located on the same straight line as the diagonal line of the first rectangle. In this embodiment, the side length of the first rectangle is preferably 10μm, the side length of the second rectangle contacting the side length of the first rectangle is 0.01μm, and another second rectangle is arranged on the side away from the first rectangle, and the side length of the second rectangle is 0.005μm, as shown in Figure 9 .

[0075] Figure 11The 3*3 array mask plate is shown, wherein the dark area is the metal Cr light shielding layer 2, the side length of the first rectangle is 10 μm, and the interval between the adjacent two main units is 15 μm. Figure 11 In the middle, because the second rectangle size is too small, the ratio difference between the first rectangle is too large, so Figure 11 In the middle, the second rectangle cannot be displayed, and the first rectangle and the second rectangle in other drawings are also structural diagrams and not actual sizes.

[0076] The above embodiments are only for illustrating the technical concept and characteristics of the present application, the purpose is to enable the person skilled in the art to understand the content of the present application and to implement it, and cannot limit the protection scope of the present application, any equivalent changes or modifications according to the spirit and essence of the present application should be covered within the protection scope of the present application.

[0077] The endpoints of the ranges and any values claimed herein are not to be construed as limited. They are presented as being approximate values. Ranges can be expressed as from about one particular value to about another particular value. When such a range is provided, the endpoints of the range are included in the range, and the endpoints can be combined with one another. When two ranges are provided, they can be combined to form a new range. These new ranges are also contemplated within the scope of the disclosed embodiments.

Claims

1. A mask for micro light emitting diodes, characterized in that The mask plate comprises a substrate layer and a light shielding layer on the substrate layer, the light shielding layer comprises main units and auxiliary units at one or more corners of the main units; the main unit comprises a first rectangle, the auxiliary unit comprises a second rectangle, and the corners of the second rectangle are in contact with the corners of the first rectangle; the diagonal of the first rectangle and the diagonal of the second rectangle are on the same straight line.

2. The micro light emitting diode mask template of claim 1, wherein, A plurality of second rectangles are arranged at the corners of each main unit; the size of the plurality of second rectangles gradually decreases from the direction close to the first rectangle to the direction away from the first rectangle.

3. The micro light emitting diode mask template of claim 2, wherein, The diagonal of the plurality of second rectangles at the corners of each main unit is on the same straight line as the diagonal of the first rectangle.

4. The micro light emitting diode mask template of claim 3, wherein, The side length of the first rectangle is 8-15 μm; the side length of the second rectangle is 0.001-0.02 μm.

5. The micro light emitting diode mask template of claim 4, wherein, 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.

6. The micro-LED mask template according to any one of claims 1-5, wherein, The light shielding layer comprises a plurality of main units, and the plurality of main units are uniformly distributed on the substrate layer.

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