Light-emitting diodes and their manufacturing methods, light-emitting devices

Abstract

This invention belongs to the field of semiconductor technology, and particularly relates to a light-emitting diode (LED) and its fabrication method and light-emitting device. The LED includes at least a substrate and an epitaxial unit. The substrate has an upper surface, a lower surface, and four side surfaces. The epitaxial unit is located on the upper surface of the substrate. The invention is characterized in that the side surfaces of the substrate have a first modified layer and a second modified layer, and the first modified layer and the second modified layer are not located on the same vertical plane. This invention can effectively improve the appearance yield and luminous brightness of LEDs.

Description

Light-emitting diode, manufacturing method thereof, and light-emitting device Technical Field

[0001] The present invention belongs to the field of semiconductor technology, and in particular relates to a light emitting diode, a manufacturing method thereof, and a light emitting device. Background Art

[0002] Light-emitting diodes (LEDs) are widely used in our daily lives. Compared with traditional light sources, LEDs have advantages such as small size, low energy consumption, and long life. They are a key trend in the development of modern lighting and have been widely used in indicator lights, backlights, display screens and other fields.

[0003] Light-emitting diodes are produced by singulating LED wafers. Existing dicing methods typically utilize two vertically overlapping laser beams to focus within a substrate 1', creating a burst (i.e., invisible dicing). This creates two modified layers 5' (i.e., laser scratches) within the substrate 1'. These two modified layers 5' are located on the same vertical plane, as shown in Figures 1-3. However, with this invisible dicing method, the two laser beams can interfere with each other during the invisible dicing process, potentially leaving localized areas of the substrate uncut and causing laser spot leaks. This can lead to low visual yield and brightness during the subsequent LED wafer splitting process. Summary of the Invention

[0004] In view of the above-mentioned shortcomings of the prior art, the present invention provides a light-emitting diode and a manufacturing method thereof, and a light-emitting device to solve the problem of laser hidden cutting leakage and improve the appearance yield and light brightness of the light-emitting diode.

[0005] According to a first aspect of the present invention, the present invention provides the following light-emitting diode, comprising at least a substrate and an epitaxial unit, wherein the substrate has an upper surface, a lower surface and four side surfaces, and the epitaxial unit is located on the upper surface of the substrate, and is characterized in that the side surfaces of the substrate have a first modified layer and a second modified layer, and the first modified layer and the second modified layer are not located on the same vertical plane.

[0006] In some embodiments, along the vertical direction, the distance between the first modified layer and the second modified layer is d1, 0 μm<d1≤25 μm.

[0007] In some embodiments, along the horizontal direction, the distance between the first modified layer and the second modified layer is d2, and 4 μm≤d2≤6 μm.

[0008] In some embodiments, the first modified layer is located farther from the bottom surface of the substrate than the second modified layer.

[0009] In some embodiments, the substrate has a thickness h, where h≥150 μm.

[0010] In some embodiments, the distance from the first modified layer to the lower surface of the substrate is d3, (2 / 5)*h≤d3≤(2 / 3)*h.

[0011] In some embodiments, the distance from the second modified layer to the lower surface of the substrate is d4, (1 / 4)*h≤d3≤(1 / 3)*h.

[0012] In some embodiments, there is a slope or step between the first modified layer and the second modified layer.

[0013] In some embodiments, at least one of the four sides of the substrate is a rough surface.

[0014] According to a second aspect of the present invention, the present invention provides a light-emitting device comprising the above-mentioned light-emitting diode.

[0015] According to a third aspect of the present invention, the present invention provides a method for manufacturing a light emitting diode, comprising the following steps:

[0016] S1. Providing an LED wafer, wherein the LED wafer comprises an original substrate and a plurality of independent epitaxial units located on the original substrate;

[0017] S2. Performing laser hidden cutting in the original substrate, wherein the laser hidden cutting is performed between two adjacent epitaxial units. The laser hidden cutting includes a first laser hidden cutting and a second laser hidden cutting. The beams of the first laser hidden cutting and the second laser hidden cutting do not overlap in the vertical direction and have a displacement difference, so as to form a first modified layer and a second modified layer in the original substrate.

[0018] S3. Use the modified layer to split the original substrate to form a plurality of light-emitting diodes having a substrate, wherein the substrate has an upper surface, a lower surface and four side surfaces, the upper surface of the substrate has an epitaxial unit, the side surfaces of the substrate have a first modified layer and a second modified layer, and the first modified layer and the second modified layer are not located in the same vertical plane.

[0019] In some embodiments, the depths of the first laser cutting and the second laser cutting are different.

[0020] In some embodiments, the position of the first laser hidden cutting is farther away from the lower surface of the original substrate than the position of the second laser hidden cutting.

[0021] In some embodiments, the first laser ablation and the second laser ablation are performed simultaneously or at different times.

[0022] In some embodiments, the original substrate is first subjected to a first laser stealth cutting, and then the original substrate is subjected to a second laser stealth cutting.

[0023] In some embodiments, along the vertical direction, the distance between the first laser hidden cutting position and the second laser hidden cutting position is no more than 25 μm and is not 0 μm.

[0024] In some embodiments, the distance between the first laser cutting position and the second laser cutting position in the horizontal direction is not less than 4 μm and not more than 6 μm.

[0025] In some embodiments, before performing the laser stealth cutting step in the original substrate, the side of the original substrate away from the epitaxial unit is thinned, and the thickness of the original substrate after thinning is not less than 150 μm.

[0026] Other features and advantages of the present invention will be described in the following description, and in part will become apparent from the description, or will be understood by practicing the present invention. The purposes and other advantages of the present invention can be realized and obtained by the structures particularly pointed out in the description, claims and drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] The accompanying drawings are used to provide a further understanding of the present invention and constitute a part of the specification. Together with the embodiments of the present invention, they are used to explain the present invention and do not constitute a limitation of the present invention. In addition, the accompanying drawings are for description only and are not drawn to scale.

[0028] FIG1 is a schematic diagram of laser hidden cutting of a local area of ​​an LED wafer in the prior art.

[0029] FIG. 2 is a partial SEM image of the substrate side of a light emitting diode after being split in the prior art.

[0030] FIG3 is a schematic structural diagram of a light emitting diode in the prior art.

[0031] FIG4 is a schematic structural diagram of an original substrate in an embodiment of the present invention.

[0032] FIG5 is a schematic diagram of the structure of growing an epitaxial layer on an original substrate according to an embodiment of the present invention.

[0033] FIG6 is a schematic diagram of the structure of the epitaxial layer after etching in an embodiment of the present invention.

[0034] FIG7 is a schematic diagram of the structure of the electrode fabricated in an embodiment of the present invention.

[0035] FIG8 is a schematic diagram of the structure of laser hidden cutting of LED wafers according to an embodiment of the present invention.

[0036] FIG9 is a schematic structural diagram of a light emitting diode according to an embodiment of the present invention.

[0037] FIG10 is a schematic structural diagram of the substrate side of a light emitting diode according to an embodiment of the present invention.

[0038] FIG11 is a partial SEM image of the side surface of the light emitting diode to the substrate in an embodiment of the present invention.

[0039] Figure 12 is a data chart comparing different spacings d1 and thrust values ​​(anti-fracture performance).

[0040] FIG13 is a data chart comparing different spacings d1 and appearance defect loss rates.

[0041] Figure annotation:

[0042] 1', substrate; 5', modified layer;

[0043] 1. Original substrate; 10. Substrate; 11. Upper surface; 12. Lower surface; 13. Side surface; 2. Epitaxial unit; 20. Epitaxial layer; 21. First semiconductor layer; 22. Active layer; 23. Second semiconductor layer; 24. Step structure (Mesa); 25. Isolation trench; 31. First electrode; 32. Second electrode; 40. Laser emitter; 41. First laser hidden cut; 42. Second laser hidden cut, 51. First modified layer; 52. Second modified layer. DETAILED DESCRIPTION

[0044] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions 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 part of the embodiments of the present invention, not all of the embodiments; the technical features designed in different implementation modes of the present invention described below can be combined with each other as long as they do not conflict with each other; based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0045] In the description of the present invention, it should be understood that the terms "center", "lateral", "up", "down", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside" and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or component referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore cannot be understood as limiting the present invention. In addition, the terms "first" and "second" are used for descriptive purposes only, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, features defined as "first" and "second" may explicitly or implicitly include one or more of the features. In the description of the present invention, unless otherwise specified, "multiple" means two or more. In addition, the term "including" and any variations thereof all mean "at least including". Example 1

[0046] This embodiment provides a method for manufacturing a light emitting diode, comprising the following steps:

[0047] Step S1: providing an LED wafer. The LED wafer includes an original substrate 1 and a plurality of independent epitaxial units 2 located on the original substrate 1, as shown in FIG. 4 to FIG. 7 .

[0048] The original substrate 1 can be an insulating substrate or a conductive substrate. The material of the substrate is selected from one of Al2O3, SiC, GaAs, GaN, AlN, GaP, Si, ZnO, MnO and any combination thereof.

[0049] In this embodiment, the original substrate 1 is a sapphire (Al2O3) substrate. The c-plane surface of the sapphire substrate is defined as the front surface (upper surface 11), and the opposite surface is defined as the back surface (lower surface 12). The epitaxial layer is grown on the front surface of the original substrate 1. The epitaxial layer can be formed by physical vapor deposition (PVD), chemical vapor deposition (CVD), and epitaxial growth. For details, see Figures 4 and 5.

[0050] Continuing with FIG5 , the epitaxial layer 20 includes at least a first semiconductor layer 21, an active layer 22, and a second semiconductor layer 23, which are sequentially formed on the front surface of the original substrate 1. The first semiconductor layer 21, the active layer 22, and the second semiconductor layer 23 are merely the basic components of the epitaxial layer 20. Furthermore, the epitaxial layer 20 may also include other functional structural layers that optimize the performance of the light-emitting diode, such as a buffer layer, a stress relief layer, and an electron blocking layer. The conductivity type of the second semiconductor layer 23 is opposite to that of the first semiconductor layer 21. For example, the first semiconductor layer 21 may be an n-type semiconductor layer and the second semiconductor layer 23 may be a p-type semiconductor layer, or the first semiconductor layer 21 may be a p-type semiconductor layer and the second semiconductor layer 23 may be an n-type semiconductor layer. In this embodiment, the first semiconductor layer 21 is an n-type semiconductor layer and the second semiconductor layer 23 is a p-type semiconductor layer. The active layer 22 is a quantum well region for emitting light and may emit red, green, blue, or other light-emitting types.

[0051] Referring to Figures 6 and 7 , the chip manufacturing process etches the epitaxial layer 20 to form isolation trenches 25 and a stepped structure (Mesa) 24, and forms a first electrode 31 and a second electrode 32 on the epitaxial layer 20 to form an LED wafer. The isolation trenches 25 isolate the epitaxial layer 20 to form a number of independent epitaxial units 2, thereby defining the size of the light-emitting diode; the stepped structure 24 provides an area for the fabrication of the first electrode 31 and the second electrode 32. Since the specific process of completing the chip manufacturing process on the epitaxial layer 20 to obtain multiple epitaxial units 2 is well known to those skilled in the art, this application will not be repeated here. Furthermore, the chip manufacturing process can also form other functional structural layers on the epitaxial layer 20 that optimize the performance of the light-emitting diode, such as a current spreading layer, a current blocking layer, and a Bragg reflector (DBR).

[0052] Step S2: performing laser hidden cutting in the original substrate 1 to form a modified layer in the original substrate 1. The position of the laser hidden cutting is located between two adjacent epitaxial units 2, as shown in FIG8 .

[0053] In this embodiment, the original substrate 1 is processed by adopting two laser hidden cutting processes to facilitate the subsequent cutting and splitting, and to avoid the problem of poor splitting or failure to split. Both laser hidden cuttings act on the original substrate 1 and are located between two adjacent epitaxial units 2, that is, below the area where the corresponding isolation groove 25 is located, rather than below the area where the corresponding epitaxial unit 2 is located. Specifically, the laser hidden cutting includes a first laser hidden cutting 41 and a second laser hidden cutting 42. The first laser hidden cutting 41 and the second laser hidden cutting 42 act on different positions in the original substrate 1 to facilitate the formation of two modified layers, specifically a first modified layer 51 and a second modified layer 52. In other embodiments, the original substrate 1 can also be treated with more laser hidden cutting processes to facilitate cutting and splitting, but the more laser hidden cuttings are performed, the worse the fracture resistance of the light-emitting diode after splitting.

[0054] Regarding laser stealth cutting, it is achieved by emitting laser pulses of a certain power, wavelength, and focal length at a specific frequency through a laser emitter 40 toward the original substrate 1. The laser is directly focused within the original substrate 1 to form multiple hidden cutting points, thereby forming a modified layer within the original substrate 1. The modified layer is generally a cavity or cavity with a relaxed material structure (laser scratch). This modified layer is composed of a combination of multiple hidden cutting points, wherein a single point can be circular, thin strip, or diamond-shaped, or other shapes are not particularly limited in the present invention. The frequency and power of the laser during the laser stealth cutting process are not limited and are determined according to actual conditions. In this embodiment, the light beam of the laser emitter 40 is emitted from the back side of the original substrate 1 toward the interior of the original substrate 1.

[0055] To reduce the mutual influence of the two laser beams during the hidden cutting process and improve the defect of laser leakage points in the prior art, this embodiment uses two non-overlapping laser beams in the perpendicular direction (vertical direction) to cut different positions within the substrate and focus them to produce a hotspot. In other words, the first laser hidden cutting 41 and the second laser hidden cutting 42 are staggered in position for cutting, as shown in Figure 8. The laser beam emission path can be achieved by adjusting the optical path of the laser emitter 40 or the control software, so that the laser beams of the first laser hidden cutting 41 and the second laser hidden cutting 42 produce a position offset or displacement difference.

[0056] In this embodiment, the first laser implicit cut 41 and the second laser implicit cut 42 have different vertical depths, which refers to the distance from the back surface (lower surface 12) of the original substrate 1 to the implicit cut position. Preferably, the depth of the first laser implicit cut 41 is greater than the depth of the second laser implicit cut 42, meaning that the first laser implicit cut 41 is located further from the back surface (lower surface 12) of the original substrate 1 than the second laser implicit cut 42. Horizontally, there is a displacement difference between the first laser implicit cut 41 and the second laser implicit cut 42; the two laser beams do not overlap, but are separated by a distance greater than 0 μm.

[0057] It should be noted that the first laser hidden cutting 41 will form a first modified layer 51, and the second laser hidden cutting 42 will form a second modified layer 52. Moreover, the first laser hidden cutting 41 and the second laser hidden cutting 42 are only used to distinguish the two laser hidden cuttings, and it is not necessary to perform the first laser hidden cutting 41 first and then the second laser hidden cutting 42. In some embodiments, the first laser hidden cutting 41 and the second laser hidden cutting 42 can be performed simultaneously or at different times, that is, two laser beams can be used for hidden cutting at the same time, or a single laser beam can be used for hidden cutting twice. In this embodiment, during the laser hidden cutting process, it is preferred to first perform the first laser hidden cutting 41 on the original substrate 1, and then perform the second laser hidden cutting 42 on the original substrate 1. By first performing large-depth laser hidden cutting and step-by-step hidden cutting, the loss of hidden cutting energy can be effectively avoided, thereby reducing the laser leak phenomenon to ensure the overall cutting yield.

[0058] In some embodiments, along the vertical direction, the distance from the first laser hidden cutting 41 position to the second laser hidden cutting 42 position is not greater than 25 μm and is not 0 μm, so as to ensure that the light-emitting diode has excellent anti-fracture performance; along the horizontal direction, the distance from the first laser hidden cutting 41 position to the second laser hidden cutting 42 position is not less than 4 μm and not greater than 6 μm, so as to ensure the light output efficiency and production cost of the light-emitting diode.

[0059] In some embodiments, the location of the first laser cut 41 corresponds to the midpoint of the isolation trench 25 between two adjacent epitaxial units 2. This allows for a better cracking effect, improves the appearance yield of the LED, and effectively avoids damage to the epitaxial layer 20 and Mesa 24 anomalies, thereby achieving higher light extraction efficiency. The second laser cut 42 is located to one side of the first laser cut 41. For details, see Figure 8. It can be located to the left or right of the first laser cut 41, and the present invention does not impose any further limitations.

[0060] In some embodiments, before the laser hidden cutting step is performed in the original substrate 1, the side of the original substrate 1 away from the epitaxial unit 2 is thinned. Specifically, the thinning can be achieved by grinding and polishing. Grinding and polishing not only reduce the thickness of the original substrate 1, but also reduce the stress between the original substrate 1 and the epitaxial unit 2. In addition, grinding and polishing can also flatten the surface of the original substrate 1 to a transparent and bright state, which is beneficial for subsequent laser hidden cutting. For example, taking a conventional sapphire substrate with a thickness of 600μm to 750μm as an example, the substrate is thinned to 150μm to 250μm after one grinding to avoid substrate warping caused by a thin substrate, but it is not limited to this.

[0061] In some embodiments, the thickness of the thinned original substrate 1 is h. Preferably, the thickness h of the original substrate 1 is not less than 150 μm; further preferably, the thickness h of the original substrate 1 is 150 μm~200 μm. The distance from the position of the first laser hidden cut 41 to the lower surface 12 of the original substrate 1 is defined as d3, and the distance from the position of the second laser hidden cut 42 to the lower surface 12 of the original substrate 1 is defined as d4. In one embodiment, the positions of the first laser hidden cut 41 and the second laser hidden cut 42 are equivalent to being located in the middle or lower part of the original substrate 1, so as to avoid the cracks generated by the laser hidden cut inside the substrate from extending to the upper surface 11 of the original substrate 1, thereby avoiding damage to the epitaxial unit 2 by the laser hidden cut. Taking the thickness h of the original substrate 1 as 200 μm as an example, d3 is 100 μm~110 μm, and d4 is 80 μm~90 μm. In a preferred embodiment, (2 / 5)*h≤d3≤(2 / 3)*h, (1 / 4)*h≤d3≤(1 / 3)*h, to ensure the yield of subsequent light-emitting diodes. It should be noted that the above distance and spacing refer to the shortest distance and vertical distance between the two.

[0062] Step S3: Using the modified layer to split the original substrate 1 to form a plurality of light-emitting diodes having the substrate 10, as shown in FIG9 .

[0063] Specifically, the first modified layer 51 and the second modified layer 52 formed within the original substrate 1 are used for cleaving to form multiple LED chips (light-emitting diodes). The cleaving process can employ either a forward cleavage or a reverse cleavage method, cleaving the original substrate 1 along the first modified layer 51 and the second modified layer 52. The specific processes of forward cleavage and reverse cleavage are well known to those skilled in the art and are not described in detail herein. In other embodiments, film expansion can also be used to achieve this.

[0064] After cleaving, the LED wafer is split into multiple light-emitting diodes each having a substrate 10. The original substrate 1 is split into multiple substrates 10, each having an upper surface 11, a lower surface 12, and four side surfaces 13. An epitaxial unit 2 is located on the upper surface 11 of each substrate 10 to form a light-emitting diode. It should be noted that the upper surface 11 and lower surface 12 of the substrate 10 are portions of the upper surface 11 and lower surface 12 of the original substrate 1. The side surfaces 13 of the substrate 10 are concave and convex after cleaving, and the side surfaces 13 of the substrate 10 have a first modified layer 51 and a second modified layer 52. The first modified layer 51 and the second modified layer 52 are located on the convex and concave surfaces, respectively, and are not located on the same vertical plane. For details, see Figures 10 and 11. The first modified layer 51 is located farther from the lower surface 12 of the substrate 10 than the second modified layer 52. It should be noted that the modified layer located on the side surface 13 of the substrate 10 is formed by laser cutting in step S2 , and the first modified layer 51 and the second modified layer 52 are cleaved to form the side surface 13 of the substrate 10 .

[0065] In some embodiments, the distance between the first modified layer 51 and the second modified layer 52 in the vertical direction is d1; in the horizontal direction, the distance between the first modified layer 51 and the second modified layer 52 is d2. Preferably, 0μm<d1≤25μm, which can ensure that the light-emitting diode has excellent anti-breaking performance while improving the appearance yield; 4μm≤d2≤6μm, in order to improve the light extraction efficiency of the light-emitting diode, increase the output of the light-emitting diode and reduce production costs. It has been verified that when d2 is less than 4μm, not only can the luminous efficiency not be improved, but it will also be limited by the small spacing between the two modified layers (that is, the spacing between the two laser hidden cuts is too small), resulting in the problem of laser leakage, which ultimately affects the appearance yield of the light-emitting diode.

[0066] In some embodiments, during the LED wafer splitting process, a slope or step can be formed between the first modified layer 51 and the second modified layer 52, as shown in Figure 9 or 11, to increase the reflection area of ​​the side surface, thereby changing the propagation path and angle of the light on the side surface, thereby increasing the light extraction efficiency and greatly improving the brightness of the light-emitting diode.

[0067] In some embodiments, to further improve light extraction efficiency, some of the four side surfaces 13 of the substrate 10 may be roughened so that at least one side surface 13 is roughened to avoid total reflection. The roughened surface may have a regular or irregular roughening pattern, preferably a regular roughening pattern. Example 2

[0068] This embodiment provides a light-emitting diode, as shown in FIG9 . The light-emitting diode can be manufactured using the method described in Example 1 above, but is not limited to the method described in Example 1. The light-emitting diode comprises at least a substrate 10 and an epitaxial unit 2. The substrate 10 is defined as having an upper surface 11, a lower surface 12, and four side surfaces 13. Specifically, the epitaxial unit 2 comprises an epitaxial layer 20 formed on the upper surface 11 of the substrate 10 by an epitaxial process, a stepped structure (Mesa) 24 formed by a chip manufacturing process, and an electrode on the epitaxial layer 20.

[0069] The substrate 10 can be an insulating substrate or a conductive substrate. The material of the substrate 10 is selected from Al2O3, SiC, GaAs, GaN, AlN, GaP, Si, ZnO, MnO, or any combination thereof. In this embodiment, the substrate 10 is preferably a sapphire substrate (Al2O3).

[0070] The epitaxial layer 20 includes at least a first semiconductor layer 21, an active layer 22, and a second semiconductor layer 23, stacked sequentially on the upper surface 11 of the substrate 10. For example, in this embodiment, the first semiconductor layer 21 is an n-type GaN layer, the active layer 22 is a GaN / InGaN multi-quantum well layer, and the second semiconductor layer 23 is a p-type GaN layer. The first semiconductor layer 21, the active layer 22, and the second semiconductor layer 23 are the basic building blocks of the epitaxial layer 20. Furthermore, the epitaxial layer 20 may also include other functional structural layers that optimize the performance of the light-emitting diode. Furthermore, the epitaxial layer 20 includes a stepped structure (Mesa) 24, which exposes a portion of the first semiconductor layer 21 for connection to electrodes. These electrodes include a first electrode 31 and a second electrode 32. The first electrode 31 is disposed on the exposed first semiconductor layer 21, and the second electrode 32 is disposed on the second semiconductor layer 23, thereby forming an electrical connection with the epitaxial layer 20. In this embodiment, the first electrode 31 is an n-electrode, and the second electrode 32 is a p-electrode.

[0071] Specifically, the first electrode 31 and the second electrode 32 are both metal electrodes, and the materials of the second electrode 31 and the first electrode 32 are selected from the group consisting of nickel (Ni), palladium (Pd), platinum (Pt), chromium (Cr), gold (Au), titanium (Ti), silver (Ag), aluminum (Al), germanium (Ge), tungsten (W), tungsten silicide (SiW), tantalum (Ta), gold-zinc alloy (AuZn), gold-beryllium alloy (AuBe), gold-germanium alloy (AuGe), and gold-germanium-nickel alloy (AuGeNi), or a combination thereof. Typically, the first electrode 31 and the second electrode 32 are formed by depositing multiple metal material layers.

[0072] In this embodiment, the side surface 13 of the substrate 10 has a first modified layer 51 and a second modified layer 52. The first modified layer 51 and the second modified layer 52 do not overlap and are not located on the same vertical plane to ensure the appearance yield and light extraction efficiency of the LED. Furthermore, the first modified layer 51 is located further away from the lower surface 12 of the substrate 10 than the second modified layer 52.

[0073] In some embodiments, the distance between the first modified layer 51 and the second modified layer 52 along the vertical direction is d1; and the distance between the first modified layer 51 and the second modified layer 52 along the horizontal direction is d2.

[0074] It has been verified that the size of the spacing d1 affects the LED's fracture resistance and appearance yield, as shown in Figures 12 and 13. A smaller spacing d1 improves the LED's fracture resistance, but also increases the appearance yield loss. A larger spacing d1, while lessening the appearance yield loss, worsens the LED's fracture resistance, making it more susceptible to force and fracture. Our research has found that appearance yield is primarily affected by hidden cutting. The smaller the spacing d1, the more likely the second laser hidden cutting process will produce laser leaks, making it difficult to crack locally. Forced cracking severely impacts the LED's appearance yield. The present invention mitigates the leak defects during laser hidden cutting by arranging the first and second modified layers 51 and 52 on different vertical planes. Therefore, in some embodiments, by arranging the first and second modified layers on different vertical planes and setting an appropriate spacing d1 (preferably 0μm < d1 ≤ 25μm), the LED can maintain excellent fracture resistance while also improving appearance yield.

[0075] In some embodiments, the distance d2 between the first modified layer 51 and the second modified layer 52 is set to 4μm to 6μm. If the horizontal distance d2 between the first modified layer 51 and the second modified layer 52 is too small, the light extraction efficiency of the LED cannot be improved and the appearance yield of the LED is also affected (there may be hidden cutting leakage issues). If the horizontal distance d2 between the first modified layer 51 and the second modified layer 52 is too large, the output of LEDs on a single LED wafer will be reduced, affecting production costs.

[0076] In some embodiments, the thickness of substrate 10 is h. Preferably, the thickness h of substrate 10 is no less than 150 μm; more preferably, the thickness h of substrate 10 is between 150 μm and 200 μm. The distance between the first modified layer 51 and the lower surface 12 of substrate 10 is d3, and the distance between the second modified layer 52 and the lower surface 12 of substrate 10 is d4. In one embodiment, the first modified layer 51 and the second modified layer 52 are located in the middle or lower portion of substrate 10. Taking the thickness h of substrate 10 as 200 μm as an example, d3 is between 100 μm and 110 μm, and d4 is between 80 μm and 90 μm. In a preferred embodiment, (2 / 5)*h ≤ d3 ≤ (2 / 3)*h, and (1 / 4)*h ≤ d3 ≤ (1 / 3)*h. This can produce light-emitting diodes with improved appearance yield and brightness. It should be noted that the distances and spacings mentioned above refer to the shortest distance between the two and the vertical distance between them.

[0077] In some embodiments, there is a slope or step between the first modified layer 51 and the second modified layer 52, as shown in Figure 8 or 10, so as to increase the reflection area of ​​the side 13, thereby changing the propagation path and angle of the light on the side 13, thereby increasing the light extraction efficiency and greatly improving the brightness of the light-emitting diode.

[0078] In some embodiments, to further improve light extraction efficiency, at least one of the four side surfaces 13 of the substrate 10 is roughened to avoid total reflection. The roughened surface may be a surface having a regular or irregular roughening pattern, preferably a surface having a regular roughening pattern.

[0079] By conducting a comparative experiment between the light-emitting diode of the prior art shown in FIG3 and the light-emitting diode of the present invention shown in FIG9 , it was found that the light-emitting efficiency of the light-emitting diode of the present invention is greatly improved (the following data is the average value verified by multiple light-emitting diodes), as follows:

[0080]

[0081] Table 1 Point measurement data of light-emitting diodes

[0082]

[0083] Table 2 Package data of light emitting diodes

[0084] As shown in Tables 1 and 2, under the same test conditions, the brightness of the light-emitting diode of the present invention is improved by 0.61% under spot measurement and by 0.18% under package measurement compared with the light-emitting diode of the prior art. Overall, the brightness of the light-emitting diode of the present invention is improved by 0.79% compared with the light-emitting diode of the prior art.

[0085] This embodiment also provides a light-emitting device comprising a light-emitting diode according to any of the above embodiments. The light-emitting device can be, for example, a white light illumination device, a backlight display device, a car light, a flashlight, a projection light, a stage light, or the like. The light-emitting device has higher light extraction efficiency and higher brightness.

[0086] In addition, those skilled in the art should understand that, although there are many problems in the prior art, each embodiment or technical solution of the present invention may be improved in only one or several aspects, without having to simultaneously solve all the technical problems listed in the prior art or background art. Those skilled in the art should understand that any content not mentioned in a claim should not be construed as limiting the claim.

[0087] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the above embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A light-emitting diode comprising at least a substrate and an epitaxial unit, wherein the substrate has an upper surface, a lower surface, and four side surfaces, and the epitaxial unit is located on the upper surface of the substrate, characterized in that: The side surface of the substrate has a first modified layer and a second modified layer, and the first modified layer and the second modified layer are not located in the same vertical plane.

2. The light emitting diode according to claim 1, characterized in that Along the vertical direction, the distance between the first modified layer and the second modified layer is d1, 0 μm<d1≤25 μm.

3. The light emitting diode according to claim 1, characterized in that In the horizontal direction, the distance between the first modified layer and the second modified layer is d2, 4 μm≤d2≤6 μm.

4. The light emitting diode according to claim 1, characterized in that The first modified layer is located farther from the bottom surface of the substrate than the second modified layer.

5. The light emitting diode according to claim 1, characterized in that The thickness of the substrate is h, where h is ≥ 150 μm.

6. The light emitting diode according to claim 5, characterized in that The distance from the first modified layer to the lower surface of the substrate is d3, (2 / 5)*h≤d3≤(2 / 3)*h.

7. The light emitting diode according to claim 5, characterized in that The distance from the second modified layer to the lower surface of the substrate is d4, (1 / 4)*h≤d3≤(1 / 3)*h.

8. The light emitting diode according to claim 1, characterized in that There is an inclined surface or a step between the first modified layer and the second modified layer.

9. The light emitting diode according to claim 1, characterized in that At least one of the four side surfaces of the substrate is a rough surface.

10. A light emitting device, characterized in that The light-emitting device comprises the light-emitting diode according to any one of claims 1 to 9.

11. A method for manufacturing a light emitting diode, characterized in that: The following steps are involved: S1. Providing an LED wafer, wherein the LED wafer comprises an original substrate and a plurality of independent epitaxial units located on the original substrate; S2. Performing laser hidden cutting in the original substrate, wherein the laser hidden cutting is performed between two adjacent epitaxial units. The laser hidden cutting includes a first laser hidden cutting and a second laser hidden cutting. The beams of the first laser hidden cutting and the second laser hidden cutting do not overlap in the vertical direction and have a displacement difference, so as to form a first modified layer and a second modified layer in the original substrate. S3. Use the modified layer to split the original substrate to form a plurality of light-emitting diodes having a substrate, wherein the substrate has an upper surface, a lower surface and four side surfaces, the upper surface of the substrate has an epitaxial unit, the side surfaces of the substrate have a first modified layer and a second modified layer, and the first modified layer and the second modified layer are not located in the same vertical plane.

12. The method for manufacturing a light emitting diode according to claim 11, wherein: The depths of the first laser hidden cutting and the second laser hidden cutting are different.

13. The method for manufacturing a light emitting diode according to claim 11, wherein: The position of the first laser hidden cutting is farther away from the lower surface of the original substrate than the position of the second laser hidden cutting.

14. The method for manufacturing a light emitting diode according to claim 11, wherein: The first laser stealth cutting and the second laser stealth cutting are performed simultaneously or at different times.

15. The method for manufacturing a light emitting diode according to claim 13, wherein: The original substrate is first subjected to a first laser hidden cutting process, and then the original substrate is subjected to a second laser hidden cutting process.

16. The method for manufacturing a light emitting diode according to claim 11, wherein: In the vertical direction, the distance between the first laser hidden cutting position and the second laser hidden cutting position is not greater than 25 μm and is not 0 μm.

17. The method for manufacturing a light emitting diode according to claim 11, wherein: In the horizontal direction, the distance between the first laser hidden cutting position and the second laser hidden cutting position is not less than 4 μm and not more than 6 μm.

18. The method for manufacturing a light emitting diode according to claim 11, wherein: Before performing the laser stealth cutting step in the original substrate, the side of the original substrate away from the epitaxial unit is thinned, and the thickness of the original substrate after thinning is not less than 150 μm.

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