Light emitting diode chip and method of manufacturing the same

Abstract

The present disclosure provides a light emitting diode chip and a preparation method thereof, and belongs to the technical field of semiconductors. The light emitting diode chip comprises an epitaxial layer and a transparent conductive layer; the transparent conductive layer is located on one side of the epitaxial layer, the transparent conductive layer has an opening area, the orthographic projection of the opening area on the epitaxial layer is located on a P-type semiconductor layer of the epitaxial layer, the opening area has a plurality of light transmission holes, the light transmission holes penetrate through opposite surfaces of the transparent conductive layer, and the light transmission holes are arranged at intervals. The present disclosure can effectively improve the brightness of the light emitting diode chip.

Description

Technical Field

[0001] This disclosure belongs to the field of semiconductor technology, and specifically relates to a light-emitting diode chip and its fabrication method. Background Technology

[0002] A light-emitting diode (LED) is a semiconductor diode that can convert electrical energy into light energy.

[0003] In related technologies, light-emitting diode (LED) chips are a crucial component of LEDs. An LED chip primarily consists of an epitaxial layer and electrodes. To avoid current congestion around the electrodes due to high current density concentrated in the area below and near them, which negatively impacts the uniformity of light emission and heating, as well as the stability and reliability of far-field emission, a transparent conductive layer is typically placed between the electrodes and the epitaxial layer. This transparent conductive layer enables ohmic contact and improves current diffusion, thereby optimizing carrier injection and enhancing the luminous efficiency of the LED chip.

[0004] However, the transparent conductive layer inevitably absorbs some of the transmitted light, which affects the brightness of the LED chip. Summary of the Invention

[0005] This disclosure provides a light-emitting diode (LED) chip and its fabrication method, which can effectively improve the brightness of the LED chip. The technical solution is as follows: On one hand, embodiments of this disclosure provide a light-emitting diode chip, including an epitaxial layer and a transparent conductive layer; The transparent conductive layer is located on one side of the epitaxial layer. The transparent conductive layer has an opening region. The orthogonal projection of the opening region on the epitaxial layer is located on the P-type semiconductor layer of the epitaxial layer. The opening region has a plurality of light-transmitting holes. The light-transmitting holes penetrate the opposite sides of the transparent conductive layer, and the light-transmitting holes are arranged at intervals.

[0006] In another implementation of this disclosure, the light-transmitting hole is a circular hole with a diameter of 2~10µm.

[0007] In another implementation of this disclosure, the light-transmitting holes are evenly spaced within the opening area, and the distance between two adjacent light-transmitting holes is 10~30µm.

[0008] In another implementation of this disclosure, the distance between the outer edge of the opening region and the outer edge of the transparent conductive layer is 10~30µm.

[0009] In yet another implementation of this disclosure, the light-emitting diode includes a current-blocking layer; The current blocking layer is located between the epitaxial layer and the transparent conductive layer, and the orthographic projection of the current blocking layer on the epitaxial layer and the orthographic projection of the aperture region on the epitaxial layer are spaced apart from each other.

[0010] In another implementation of this disclosure, the distance between the orthographic projection of the current blocking layer on the epitaxial layer and the orthographic projection of the aperture region on the epitaxial layer is 10~30µm.

[0011] On the other hand, this disclosure provides a method for fabricating a light-emitting diode chip, the method comprising: Preparation of epitaxial layer; A transparent conductive layer is prepared on one side of the epitaxial layer; An opening area is defined on the transparent conductive layer, and multiple light-transmitting holes are photolithographically formed within the opening area. The light-transmitting holes penetrate both opposite sides of the transparent conductive layer, and the light-transmitting holes are arranged at intervals between each other.

[0012] In one implementation of this disclosure, a transparent conductive layer is prepared on one side of the epitaxial layer, comprising: A transparent conductive layer with a thickness of 300 to 1500 angstroms is prepared on one side of the epitaxial layer.

[0013] In one implementation of this disclosure, a plurality of light-transmitting holes are photolithographically formed within the opening area, including: The shape of the light-transmitting hole is set to be circular, and the diameter of the light-transmitting hole is set to be 2~10µm.

[0014] In one implementation of this disclosure, a plurality of light-transmitting holes are photolithographically formed within the opening area, including: The light-transmitting holes are evenly spaced within the opening area, and the distance between two adjacent light-transmitting holes is 10~30µm.

[0015] The beneficial effects of the technical solutions provided in this disclosure are: The light-emitting diode (LED) chip provided in this embodiment includes an epitaxial layer and a transparent conductive layer. The transparent conductive layer has an opening region with multiple light-transmitting holes that penetrate both opposite sides of the transparent conductive layer. Since the orthogonal projection of the opening region onto the epitaxial layer lies on the P-type semiconductor layer of the epitaxial layer, the orthogonal projection of all the light-transmitting holes onto the epitaxial layer also lies on the P-type semiconductor layer. In this way, when light generated by the epitaxial layer passes through the transparent conductive layer, some of the light can pass directly through the light-transmitting holes without being absorbed by the transparent conductive layer itself, thereby effectively improving the brightness of the LED chip.

[0016] In other words, the light-emitting diode chip provided in this embodiment of the present disclosure, by providing a light-transmitting hole on the transparent conductive layer, allows some light to pass directly through the light-transmitting hole without being absorbed by the transparent conductive layer itself, thereby effectively improving the brightness of the light-emitting diode chip. Attached Figure Description

[0017] To more clearly illustrate the technical solutions in the embodiments of this disclosure, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of this disclosure. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0018] Figure 1 This is a cross-sectional view of a light-emitting diode chip provided in an embodiment of this disclosure; Figure 2 This is a top view of a light-emitting diode chip provided in an embodiment of this disclosure; Figure 3 This is a flowchart illustrating a method for fabricating a light-emitting diode chip according to an embodiment of this disclosure; Figure 4 This is a flowchart of another method for fabricating a light-emitting diode chip provided in this embodiment.

[0019] The symbols in the diagram represent the following meanings: 10. Epitaxial layer; 110. N-type semiconductor layer; 120. Active layer; 130. P-type semiconductor layer; 20. Transparent conductive layer; 210. Opening area; 211. Light-transmitting hole; 30. Current blocking layer; 40. N-type electrode; 50. P-type electrode; 60. Passivation layer; 70. Substrate.

[0020] The accompanying drawings have illustrated specific embodiments of this disclosure, which will be described in more detail below. These drawings and descriptions are not intended to limit the scope of the concept in any way, but rather to illustrate the concepts of this disclosure to those skilled in the art through reference to particular embodiments. Detailed Implementation

[0021] To make the objectives, technical solutions, and advantages of this disclosure clearer, the embodiments of this disclosure will be described in further detail below with reference to the accompanying drawings.

[0022] This disclosure provides an embodiment of a light-emitting diode chip. Figure 1 See the cross-sectional view of the LED chip. Figure 1 In this embodiment, the light-emitting diode chip includes an epitaxial layer 10 and a transparent conductive layer 20, with the transparent conductive layer 20 located on one side of the epitaxial layer 10.

[0023] Figure 2 This is a top view of a light-emitting diode chip, combined with... Figure 2 The transparent conductive layer 20 has an opening region 210. The orthogonal projection of the opening region 210 on the epitaxial layer 10 is located on the P-type semiconductor layer 130 of the epitaxial layer 10. The opening region 210 has a plurality of light-transmitting holes 211. The light-transmitting holes 211 penetrate through the opposite sides of the transparent conductive layer 20, and the light-transmitting holes 211 are arranged at intervals.

[0024] The light-emitting diode (LED) chip provided in this embodiment includes an epitaxial layer 10 and a transparent conductive layer 20. The transparent conductive layer 20 has an opening region 210, within which are multiple light-transmitting holes 211, penetrating both opposite sides of the transparent conductive layer 20. Since the orthogonal projection of the opening region 210 onto the epitaxial layer 10 is located on the P-type semiconductor layer 130 of the epitaxial layer 10, the orthogonal projection of all the light-transmitting holes 211 onto the epitaxial layer 10 is also located on the P-type semiconductor layer 130 of the epitaxial layer 10. In this way, when light generated by the epitaxial layer 10 passes through the transparent conductive layer 20, some of the light can pass directly through the light-transmitting holes 211 without being absorbed by the transparent conductive layer 20 itself, thereby effectively improving the brightness of the LED chip.

[0025] In other words, the light-emitting diode chip provided in this embodiment of the present disclosure, by providing a light-transmitting hole 211 on the transparent conductive layer 20, allows some light to pass directly through the light-transmitting hole 211 without being absorbed by the transparent conductive layer 20 itself, thereby effectively improving the brightness of the light-emitting diode chip.

[0026] In this embodiment, the light-emitting diode chip also includes a substrate 70, which provides a basis for the growth of the epitaxial layer 10.

[0027] For example, the substrate 70 is a sapphire substrate, a silicon substrate, or other light-emitting diode chip substrate material.

[0028] Of course, in other embodiments, the light-emitting diode chip may not have a substrate 70, and this disclosure does not limit this.

[0029] In this embodiment, the epitaxial layer 10 includes an N-type semiconductor layer 110, an active layer 120, and a P-type semiconductor layer 130 stacked sequentially.

[0030] When the light-emitting diode chip is working, an electron transition occurs between the N-type semiconductor layer 110 and the P-type semiconductor layer 130, causing the active layer 120 to emit light.

[0031] For example, the N-type semiconductor layer 110 is an N-type GaN layer, the active layer 120 is a quantum well layer, and the P-type semiconductor layer 130 is a P-type GaN layer.

[0032] For a front-mounted LED chip, the epitaxial layer 10 has an N-type electrode 40 and a P-type electrode 50 on the side facing away from the substrate 70. Due to the insulating nature of the substrate 70, the current needs to move laterally. Since the P-type GaN layer is Mg-doped, its conductivity is much lower than that of the N-type GaN layer. This results in higher resistance when the current flows laterally at the P-type GaN layer, causing a concentrated area of ​​high current density below or near the corresponding P-type electrode 50. This current crowding effect significantly affects the uniformity of light emission and heating, as well as the stability and reliability of far-field emission of the LED chip. Furthermore, the current crowding effect can also cause a decrease in internal quantum efficiency in some areas of the LED chip due to excessively high current density.

[0033] Therefore, in order to solve the above problems, the transparent conductive layer 20 is provided between the epitaxial layer 10 and the P-type electrode 50, which can play the role of current expansion, form a uniform current distribution network, and reduce local current congestion.

[0034] For example, the transparent conductive layer 20 is an indium tin oxide (ITO) layer, which is formed by sputtering on the epitaxial layer 10 using magnetron sputtering technology. ITO has both optical transparency and high conductivity. When the epitaxial layer 10 emits light, the light can pass through the transparent conductive layer 20 well, and the current can be effectively transferred to the epitaxial layer 10, thereby improving the luminous efficiency of the light-emitting diode chip.

[0035] As mentioned above, providing a light-transmitting hole 211 on the transparent conductive layer 20 can reduce the absorption of light by the transparent conductive layer 20 while ensuring the current spreading capability of the transparent conductive layer 20. The light-transmitting hole 211 will be explained below.

[0036] For example, the light-transmitting hole 211 is a circular hole with a diameter of 2~10µm.

[0037] In the above implementation, the shape of the light-transmitting aperture 211 affects the light scattering pattern as light passes through it. Designing the aperture 211 as a circular hole ensures smooth edges, reducing light reflection and diffraction losses, thereby increasing the effective light output. Furthermore, circular holes are not only easier to fabricate, effectively reducing fabrication difficulty and cost, but also help alleviate thermal or mechanical stress concentration, improving the structural reliability of the transparent conductive layer 20.

[0038] Furthermore, the diameter of the light-transmitting aperture 211 directly affects the reduction in the area of ​​the transparent conductive layer 20. If the diameter of the light-transmitting aperture 211 is too small, the brightness improvement will be insignificant; if the diameter of the light-transmitting aperture 211 is too large, the current path of the transparent conductive layer 20 will be damaged, potentially leading to increased local resistance and voltage. Setting the diameter of the light-transmitting aperture 211 between 2 and 10 µm achieves a good balance between these two aspects.

[0039] In this embodiment, the diameter of the light-transmitting hole 211 is 4µm.

[0040] For example, each light-transmitting hole 211 is evenly spaced within the opening area 210, and the distance between two adjacent light-transmitting holes 211 is 10~30µm.

[0041] In the above implementation, each light-transmitting hole 211 is evenly spaced within the opening area 210. This ensures that light can be uniformly transmitted through the light-transmitting hole 211 and that the current can be uniformly expanded, thus avoiding local voltage increases.

[0042] Furthermore, the distance between two adjacent light-transmitting holes 211 determines the coverage density of the light-transmitting holes 211 within the opening region 210 and the current path length. If the distance between the light-transmitting holes 211 is too small, the holes 211 will be too densely packed, significantly reducing the body area of ​​the transparent conductive layer 20. This would require the current to frequently bypass the light-transmitting holes 211 during transmission, easily leading to problems such as increased local resistance and voltage instability. If the distance between the light-transmitting holes 211 is too large, the number of light-transmitting holes 211 will be too small, resulting in little improvement in brightness. Setting the distance between two adjacent light-transmitting holes 211 between 10 and 30 µm can effectively balance the above two aspects.

[0043] In this embodiment, the distance between two adjacent light-transmitting holes 211 is 15µm.

[0044] For example, the distance between the outer edge of the opening region 210 and the outer edge of the transparent conductive layer 20 is 10~30µm.

[0045] In the above implementation, if there is a light-transmitting hole 211 at the outer edge of the opening area 210, then the distance between the outer edge of the light-transmitting hole 211, which is closest to the outer edge of the transparent conductive layer 20, and the outer edge of the transparent conductive layer 20 is 10~30µm.

[0046] If the distance is too large, the light absorption at the outer edge of the transparent conductive layer 20 will increase, resulting in lower brightness than the central area and uneven brightness. If the distance is too small, it may cause leakage current at the boundary of the transparent conductive layer 20 or unstable etching. Setting the distance between 10 and 30 µm can effectively balance these two aspects.

[0047] In this embodiment, the distance between the outer edge of the opening region 210 and the outer edge of the transparent conductive layer 20 is 15µm.

[0048] See you again Figure 1 In this embodiment, the light-emitting diode includes a current blocking layer 30, which is located between the epitaxial layer 10 and the transparent conductive layer 20. The orthographic projection of the current blocking layer 30 on the epitaxial layer 10 and the orthographic projection of the aperture region 210 on the epitaxial layer 10 are spaced apart from each other.

[0049] In the above implementation, the current blocking layer 30 has the function of blocking current, which can effectively avoid the problem of local current congestion at the P-type electrode 50.

[0050] In some examples, the current blocking layer 30 is an Al2O3 layer or a SiO2 layer.

[0051] In other examples, the current blocking layer 30 is a TiO2 layer, a HfO2 layer, a Ta2O5 layer, a ZrO layer, an AlN layer, a TiN layer, or a SiN layer. x Layers, etc.

[0052] In addition, since the orthographic projection of the current blocking layer 30 on the epitaxial layer 10 and the orthographic projection of the aperture region 210 on the epitaxial layer 10 are spaced apart from each other, the etching of the light-transmitting hole 211 will not affect the current blocking layer 30, thus ensuring reliability.

[0053] For example, the distance between the orthographic projection of the current blocking layer 30 on the epitaxial layer 10 and the orthographic projection of the aperture region 210 on the epitaxial layer 10 is 10~30µm.

[0054] In the above implementation, if there is a light-transmitting hole 211 at the inner edge of the opening area 210, then the distance between the outer edge of the light-transmitting hole 211, which is closest to the outer edge of the current blocking layer 30, and the outer edge of the current blocking layer 30 is 10~30µm.

[0055] If the distance is too small, the light-transmitting aperture 211 may expose the current-blocking layer 30, causing a short circuit or current leakage. If the distance is too large, the area of ​​the opening region 210 will be too small, limiting the brightness improvement effect. Setting the distance between 10 and 30 µm can effectively balance these two aspects.

[0056] In this embodiment, the distance between the orthographic projection of the current blocking layer 30 on the epitaxial layer 10 and the orthographic projection of the aperture region 210 on the epitaxial layer 10 is 15µm.

[0057] See you again Figure 1 The light-emitting diode also includes a passivation layer 60, which covers the transparent conductive layer 20, the sidewall of the P-type electrode 50, the epitaxial layer 10, and the sidewall of the N-type electrode 40.

[0058] In the above implementation, the passivation layer 60 mainly serves as an insulating protection layer.

[0059] For example, the materials of the P-type electrode 50 and the N-type electrode 40 are one or more of the metals such as Cr, Al, AlCu, Ti, Ni, Pt, and Au.

[0060] A comparative experiment was conducted on the light-emitting diode chip provided in the embodiments of this disclosure and the light-emitting diode chips in related technologies, and the test results are shown in Table 1.

[0061]

[0062] Table 1 As shown in Table 1, the light output power (LOP) of the LED chip provided in this embodiment is effectively improved compared with the LED chip in the related art, while the difference in forward voltage (VF) is only 0.002, which can be ignored.

[0063] Figure 3 This is a flowchart of a method for fabricating a light-emitting diode chip according to an embodiment of the present disclosure. In this embodiment, the fabrication method includes: Step 301: Prepare epitaxial layer 10.

[0064] Step 302: Prepare a transparent conductive layer 20 on one side of the epitaxial layer 10.

[0065] Step 303: Define an opening region 210 on the transparent conductive layer 20, and photolithographically obtain multiple light-transmitting holes 211 within the opening region 210.

[0066] The light-transmitting holes 211 penetrate both opposite sides of the transparent conductive layer 20, and the light-transmitting holes 211 are arranged at intervals.

[0067] The light-emitting diode (LED) chip prepared by the method provided in this embodiment includes an epitaxial layer 10 and a transparent conductive layer 20. The transparent conductive layer 20 has an opening region 210, within which are multiple light-transmitting holes 211 penetrating both opposite sides of the transparent conductive layer 20. Since the orthogonal projection of the opening region 210 onto the epitaxial layer 10 is located on the P-type semiconductor layer 130 of the epitaxial layer 10, the orthogonal projection of all the light-transmitting holes 211 onto the epitaxial layer 10 is also located on the P-type semiconductor layer 130 of the epitaxial layer 10. In this way, when the light generated by the epitaxial layer 10 passes through the transparent conductive layer 20, some of the light can pass directly through the light-transmitting holes 211 without being absorbed by the transparent conductive layer 20 itself, thereby effectively improving the brightness of the LED chip.

[0068] In other words, by providing a light-transmitting hole 211 on the transparent conductive layer 20, some light can pass directly through the light-transmitting hole 211 without being absorbed by the transparent conductive layer 20 itself, thereby effectively improving the brightness of the light-emitting diode chip. Figure 4 This is a flowchart of a method for fabricating a light-emitting diode chip according to an embodiment of the present disclosure. In this embodiment, the fabrication method includes: Step 401: Provide a substrate.

[0069] For example, the substrate may be a sapphire substrate, a silicon substrate, or other light-emitting diode chip substrate materials.

[0070] Step 402: Prepare epitaxial layer 10.

[0071] For example, metal-organic chemical vapor deposition (MOCVD) is used to sequentially grow an N-type semiconductor layer 110, an active layer 120, and a P-type semiconductor layer 130.

[0072] For example, the N-type semiconductor layer 110 is an N-type GaN layer, the active layer 120 is a quantum well layer, and the P-type semiconductor layer 130 is a P-type GaN layer.

[0073] Step 403: Etch a step on the epitaxial layer 10.

[0074] For example, steps are etched on the epitaxial layer 10 using a dry etching technique to expose the N-type semiconductor layer 110.

[0075] Step 404: Prepare the current blocking layer 30.

[0076] For example, a SiO2 thin film is first deposited, and then the corresponding pattern is obtained by photolithography.

[0077] Step 405: Prepare transparent conductive layer 20.

[0078] For example, an ITO thin film is deposited.

[0079] For example, an ITO film with a thickness of 300 to 1500 angstroms is prepared on one side of the epitaxial layer 10.

[0080] In this embodiment, the thickness of the ITO film is 900 angstroms.

[0081] Step 406: Define an opening region 210 on the transparent conductive layer 20, and photolithographically obtain multiple light-transmitting holes 211 within the opening region 210.

[0082] For example, the shape of the light-transmitting hole 211 is set to circular, and the diameter of the light-transmitting hole 211 is set to 2~10µm. The light-transmitting holes 211 are evenly spaced within the opening region 210, and the distance between two adjacent light-transmitting holes 211 is 10~30µm. The distance between the outer edge of the opening region 210 and the outer edge of the transparent conductive layer 20 is 10~30µm. The distance between the orthographic projection of the current blocking layer 30 on the epitaxial layer 10 and the orthographic projection of the opening region 210 on the epitaxial layer 10 is 10~30µm.

[0083] Step 407: Prepare N-type electrode 40 and P-type electrode 50.

[0084] For example, N-type electrode 40 and P-type electrode 50 are prepared by electron beam evaporation of metal and stripping and desizing process.

[0085] Step 408: Prepare passivation layer 60.

[0086] For example, a SiO2 thin film is first deposited, and then the corresponding pattern is obtained by photolithography.

[0087] Unless otherwise defined, the technical or scientific terms used herein shall have the ordinary meaning understood by one of ordinary skill in the art to which this disclosure pertains. The terms “first,” “second,” “third,” and similar terms used in this patent application specification and claims do not indicate any order, quantity, or importance, but are merely used to distinguish different components. Similarly, the terms “an” or “a” and similar terms do not indicate a quantity limitation, but rather indicate the presence of at least one. The terms “comprising” or “including” and similar terms mean that the elements or objects preceding “comprising” or “including” encompass the elements or objects listed following “comprising” or “including” and their equivalents, and do not exclude other elements or objects. The terms “connected” or “linked” and similar terms are not limited to physical or mechanical connections, but can include electrical connections, whether direct or indirect. The terms “upper,” “lower,” “left,” “right,” etc., are used only to indicate relative positional relationships; when the absolute position of the described objects changes, the relative positional relationship may also change accordingly.

[0088] The above description is merely an optional embodiment of this disclosure and is not intended to limit this disclosure. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this disclosure should be included within the protection scope of this disclosure.

Claims

1. A light-emitting diode chip, characterized in that, It includes an epitaxial layer (10) and a transparent conductive layer (20); The transparent conductive layer (20) is located on one side of the epitaxial layer (10). The transparent conductive layer (20) has an opening region (210). The orthogonal projection of the opening region (210) on the epitaxial layer (10) is located on the P-type semiconductor layer (130) of the epitaxial layer (10). The opening region (210) has a plurality of light-transmitting holes (211). The light-transmitting holes (211) penetrate through the opposite sides of the transparent conductive layer (20). The light-transmitting holes (211) are arranged at intervals.

2. The light-emitting diode chip according to claim 1, characterized in that, The light-transmitting hole (211) is a circular hole with a diameter of 2~10µm.

3. The light-emitting diode chip according to claim 1, characterized in that, Each of the light-transmitting holes (211) is evenly spaced within the opening area (210), and the distance between two adjacent light-transmitting holes (211) is 10~30µm.

4. The light-emitting diode chip according to claim 1, characterized in that, The distance between the outer edge of the opening area (210) and the outer edge of the transparent conductive layer (20) is 10~30µm.

5. The light-emitting diode chip according to claim 1, characterized in that, The light-emitting diode includes a current blocking layer (30); The current blocking layer (30) is located between the epitaxial layer (10) and the transparent conductive layer (20), and the orthographic projection of the current blocking layer (30) on the epitaxial layer (10) and the orthographic projection of the aperture region (210) on the epitaxial layer (10) are spaced apart from each other.

6. The light-emitting diode chip according to claim 5, characterized in that, The distance between the orthographic projection of the current blocking layer (30) on the epitaxial layer (10) and the orthographic projection of the aperture region (210) on the epitaxial layer (10) is 10~30µm.

7. A method for fabricating a light-emitting diode chip, characterized in that, include: Prepare an epitaxial layer (10); A transparent conductive layer (20) is prepared on one side of the epitaxial layer (10); An opening region (210) is defined on the transparent conductive layer (20), and multiple light-transmitting holes (211) are photolithographically formed in the opening region (210). The light-transmitting holes (211) penetrate the two opposite sides of the transparent conductive layer (20), and each of the light-transmitting holes (211) is arranged at intervals.

8. The preparation method according to claim 7, characterized in that, A transparent conductive layer (20) is formed on one side of the epitaxial layer (10), comprising: A transparent conductive layer (20) with a thickness of 300~1500 angstroms is prepared on one side of the epitaxial layer (10).

9. The preparation method according to claim 7, characterized in that, Multiple light-transmitting holes (211) are photolithographically formed within the opening region (210), including: The shape of the light-transmitting hole (211) is set to be circular, and the diameter of the light-transmitting hole (211) is set to 2~10µm.

10. The preparation method according to claim 7, characterized in that, Multiple light-transmitting holes (211) are photolithographically formed within the opening region (210), including: The light-transmitting holes (211) are evenly spaced within the opening area (210), and the distance between two adjacent light-transmitting holes (211) is 10~30µm.

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