Ultraviolet light emitting diode and manufacturing method thereof

Abstract

The present invention relates to the field of semiconductor manufacturing technology, and in particular to an ultraviolet light-emitting diode and a manufacturing method thereof, comprising the following steps: 1. providing an LED wafer, the LED wafer comprising a substrate and a semiconductor stack located on an upper surface of the substrate, the semiconductor stack having a lower surface close to a side of the substrate and an opposite upper surface, the semiconductor stack sequentially comprising a first semiconductor layer, a light-emitting layer, and a second semiconductor layer from the lower surface to the upper surface; 2. providing a laser beam for multiple irradiations focused on the interior of the substrate, the laser beam comprising a first laser beam and a second laser beam, wherein the focusing position of the first laser beam is closer to the lower surface of the semiconductor stack than the focusing position of the second laser beam, the first laser beam being focused on the interior of the substrate to form a first laser cutting line, the laser scratch of the first laser cutting line being quasi-circular, and the first laser cutting line comprising the laser cutting line closest to the lower surface of the semiconductor stack; and 3. separating the LED wafer into a plurality of LED chips.

Description

Technical Field

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

[0002] A light-emitting diode (LED) is a semiconductor light-emitting element typically made of semiconductors such as GaN, GaAs, GaP, and GaAsP. Its core is a PN junction, which is responsible for the light-emitting properties. LEDs offer advantages such as high luminous intensity, high efficiency, compact size, and long life, making them considered one of the most promising light sources currently available.

[0003] In recent years, the enormous application value of ultraviolet LEDs, particularly deep ultraviolet LEDs, has attracted significant attention and become a new research hotspot. UV-LEDs (UV-LEDs) are solid-state semiconductor devices that directly convert electrical energy into ultraviolet light. With technological advancements, UV-LEDs have broad market applications in biomedicine, anti-counterfeiting, water and air purification, computer data storage, and the military.

[0004] During LED chip manufacturing, the industry typically uses invisible laser cutting to create a series of laser scratches within the sapphire substrate of the LED wafer. This is then followed by cleaving to form the LED chips. To achieve higher chip brightness, UV LEDs require thicker sapphire substrates to enhance light extraction. As the substrate becomes thicker, the power, blade depth, and number of blades used in the chip cleaving process must be increased. As these process parameters increase, the impact and damage of invisible laser cutting on the epitaxial light-emitting layer also increases. The epitaxial layer of blue LEDs is made of an InGaN system, which has relatively low stress. Its underlying layer is typically a GaN layer with a low thermal expansion coefficient. When the invisible laser cuts the sapphire substrate, some of the high-energy heat causes the substrate to crack, while the remaining high-energy heat continues to diffuse toward the epitaxial layer until it dissipates. In contrast, the epitaxial layer of UV LEDs is made of an AlGaN system, which has high overall stress. Its underlying layer is typically an AlN layer with a high thermal expansion coefficient. This makes the AlGaN-based UV LED epitaxial layer relatively sensitive to heat, making it prone to microcracks and leakage channels. Therefore, to avoid damaging the epitaxial layer, the laser invisible cut marks need to be placed further away from the epitaxial layer. This, coupled with increased substrate thickness, results in poor cleavage yield. Currently, the closest distance between the laser scratch and the semiconductor stack after invisible cutting of UV LEDs is approximately 130μm, and experiments have shown that when this distance is reduced to approximately 100μm, the yield decreases. Therefore, how to shorten the distance from the laser scratch to the semiconductor stack while maintaining the yield, so as to further improve the brightness of the product, is one of the technical problems that technicians in this field urgently need to solve. Summary of the Invention

[0005] The present invention provides a method for manufacturing an ultraviolet light-emitting diode, comprising the steps of:

[0006] 1. Provide an LED wafer, the LED wafer comprising a substrate and a semiconductor stack located on an upper surface of the substrate, the semiconductor stack having a lower surface proximal to the substrate and an upper surface opposite thereto, the semiconductor stack including, from the lower surface to the upper surface, a first semiconductor layer, a light-emitting layer, and a second semiconductor layer;

[0007] 2. providing a plurality of laser beams focused on the interior of the substrate, including a first laser beam and a second laser beam, wherein the focus position of the first laser beam is closer to the lower surface of the semiconductor stack than the focus position of the second laser beam, and the first laser beam is focused on the interior of the substrate to form a first laser cutting line, wherein the laser scratch of the first laser cutting line is substantially circular, and the first laser cutting line includes the laser cutting line closest to the lower surface of the semiconductor stack;

[0008] 3. Separate the LED wafer into several LED chips.

[0009] In some embodiments, the quasi-circular shape has a major axis and a minor axis, and the ratio of the minor axis to the major axis is no greater than 1:1.5.

[0010] In some embodiments, the first laser beam forms X rows of first laser cutting lines inside the substrate, where X≥2.

[0011] In some embodiments, the distance between the first laser beam and the bottom surface of the semiconductor stack is not less than 60 μm and not more than 130 μm.

[0012] In some embodiments, the second laser beam forms Y rows of second laser cutting lines inside the substrate, where Y≥1.

[0013] In some embodiments, the distance between the second laser beam and the bottom surface of the semiconductor stack is not less than 100 μm and not more than 210 μm.

[0014] The present invention also proposes an ultraviolet light-emitting diode, comprising a substrate and a semiconductor stack located on the upper surface of the substrate, the semiconductor stack having a lower surface close to the substrate and an opposite upper surface, the semiconductor stack including a first semiconductor layer, a light-emitting layer, and a second semiconductor layer in sequence from the lower surface to the upper surface, characterized in that: a first laser cutting line formed by a first laser beam and a second laser cutting line formed by a second laser beam are provided inside the substrate, wherein the position of the first laser cutting line is closer to the lower surface of the semiconductor stack than the position of the second laser cutting line, and the laser scratch of the first laser cutting line is quasi-circular.

[0015] In some embodiments, the substrate has X rows of first laser cutting lines formed by the first laser beam and Y rows of second laser cutting lines formed by the second laser beam, where X≥2 and Y≥1.

[0016] In some embodiments, a distance from the first laser cutting line to the bottom surface of the semiconductor stack is not less than 60 μm and not more than 130 μm.

[0017] In some embodiments, a distance from the second laser cutting line to the bottom surface of the semiconductor stack is not less than 100 μm and not more than 210 μm.

[0018] In some embodiments, the laser score of the first laser cut line is discontinuous.

[0019] In some embodiments, the first laser scratches are evenly spaced in the horizontal direction of the substrate, and the spacing of the first laser scratches in the horizontal direction of the substrate ranges from 1 μm to 16 μm.

[0020] In some embodiments, the second laser scratches are evenly spaced in the horizontal direction of the substrate, and the spacing of the second laser scratches in the horizontal direction of the substrate ranges from 2 μm to 18 μm.

[0021] In some embodiments, the first laser cutting lines are arranged in parallel, and the spacing between the first laser cutting lines in the vertical direction of the substrate is uniform or gradient.

[0022] In some embodiments, the spacing between the first laser cutting lines in the vertical direction of the substrate gradually increases as the spacing is away from the bottom surface of the semiconductor stack.

[0023] In some embodiments, a distance between two adjacent first laser cutting lines in a vertical direction of the substrate is 5 μm to 25 μm.

[0024] In some embodiments, the second laser cutting lines are arranged in parallel, and a distance between two adjacent second laser cutting lines in a vertical direction of the substrate is 35 μm to 100 μm.

[0025] In some embodiments, the thickness of the substrate is no less than 270 μm.

[0026] In some embodiments, the laser scratches of the second laser cutting lines are in the shape of thin strips.

[0027] In some embodiments, the laser scratches occupy an area ratio of greater than 20% on the side surface of the substrate.

[0028] The present invention also provides an ultraviolet light-emitting device, which uses the ultraviolet light-emitting diode provided by any of the above embodiments.

[0029] Compared with the prior art, one of the beneficial effects of the present invention is as follows:

[0030] The present invention provides a UV light-emitting diode and a method for manufacturing the same. The laser scratches near the first laser cutting line of the semiconductor stack are configured as quasi-circular burst points, replacing the existing thin strips. The incident angle of the quasi-circular burst points is close to 90 degrees, allowing most light to be emitted directly. Therefore, the quasi-circular shape is more conducive to light emission and can increase light emission. Secondly, by replacing the single high-energy first laser cutting line near the semiconductor stack with multiple low-energy first laser cutting lines, the distance between the laser hidden scratch and the semiconductor stack is shortened. This effectively solves the problem of poor cleavage yield. Second, the closer the laser hidden scratch is to the semiconductor stack, the smaller the incident angle of the light, which is more conducive to the emission of light near the active layer, thereby increasing light extraction. Third, the number of laser scratches on the chip side is increased, thereby increasing the degree of side roughening. This improves chip brightness while maintaining chip yield.

[0031] Other features and advantages of the present invention will be set forth in the following description, and in part will be obvious from the description, or may be learned by practicing the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following is a brief introduction to the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0033] Figure 1 This is a schematic diagram of the cross-sectional structure of a UV LED chip manufactured using an existing invisible cutting process;

[0034] Figure 2 Schematic diagram of the cross-sectional structure of an ultraviolet LED chip manufactured by the invisible cutting process implemented in the present invention;

[0035] Figure 3 This is a schematic diagram comparing the optical paths of a quasi-circular laser scratch and a thin strip laser scratch;

[0036] Figure 4 illustrative diagrams of several types of circular laser scratches implemented in the present invention;

[0037] Figure 5 Schematic diagram of the cross-sectional structure of an ultraviolet LED chip manufactured by the invisible cutting process implemented in the present invention;

[0038] Figures 6 to 13 is based on Figure 5 A schematic structural diagram of the manufacturing process of the ultraviolet LED chip;

[0039] Figure 14 is a schematic cross-sectional structure diagram of another ultraviolet LED chip implemented according to the present invention;

[0040] Figure 15 is a schematic cross-sectional structure diagram of another ultraviolet LED chip implemented according to the present invention;

[0041] Figure 16 is a schematic cross-sectional structure diagram of another ultraviolet LED chip implemented according to the present invention;

[0042] Figure numerals: substrate 110; semiconductor stack 120; first semiconductor layer 121; light emitting layer 122; second semiconductor layer 123; upper surface 124; lower surface 125; first contact electrode 131; second contact electrode 132; first pad electrode 141; second pad electrode 142; insulating layer 150; first laser cutting line 100; second laser cutting line 200; first cutting line 101; second cutting line 102; first height D1. DETAILED DESCRIPTION

[0043] 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.

[0044] 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".

[0045] The present invention provides a method for manufacturing an ultraviolet light-emitting diode and an ultraviolet light-emitting diode formed by the manufacturing method. By setting a plurality of low-energy first laser cutting lines with laser scratches as circular explosion points, the laser scratches are further closer to the semiconductor stack, thereby effectively improving the brightness of the chip while maintaining the chip yield. Figure 2 、 Figure 5 Schematic diagram of the cross-sectional structure of an ultraviolet LED chip manufactured by the invisible cutting process implemented in the present invention; Figures 6 to 13 is based on Figure 5 The structural diagram of the manufacturing process flow of the ultraviolet LED chip mainly includes the following steps S110 to S130, which are described in detail below.

[0046] Step S110: Provide an LED wafer, the LED wafer comprising a substrate 110 and a semiconductor stack 120 located on the upper surface of the substrate 110, see Figure 6Specifically, the substrate 110 can be a transparent or translucent material, wherein the transparent substrate or translucent substrate can allow the light radiated by the light-emitting layer 122 to pass through the substrate 110 to reach the side of the substrate 110 away from the semiconductor stack 120. For example, the substrate 110 can be any one of a sapphire flat substrate, a sapphire patterned substrate, a silicon substrate, a silicon carbide substrate, a gallium nitride substrate, and a glass substrate. In some embodiments, a combined patterned substrate 110 can be used, wherein the pattern of the substrate 110 is a series of protruding structures. The protruding structures can be a single-layer or multi-layer structure, including at least one light extraction layer with a refractive index lower than the refractive index of the substrate 110. The thickness of the light extraction layer is greater than half the height of the protruding structure, which is more conducive to the light extraction efficiency of the ultraviolet light-emitting diode. Preferably, the protruding structure is a cannonball-shaped structure, and the material of the light extraction layer can be a refractive index preferably less than 1.6, for example, silicon dioxide can be selected. In some embodiments, the substrate 110 can be thinned or removed to form a thin film chip.

[0047] The semiconductor stack 120 has a lower surface 125 close to the substrate 110 and an opposite upper surface 124 . The semiconductor stack includes a first semiconductor layer 121 , a light emitting layer 122 , and a second semiconductor layer 123 in sequence from the lower surface 125 to the upper surface 124 .

[0048] The first semiconductor layer 121 is formed on the substrate 110. The first semiconductor layer 121 may be an N-type semiconductor layer that can supply electrons to the light-emitting layer 122 under the action of a power source. In some embodiments, the first semiconductor layer 121 comprises an N-type doped nitride layer. The N-type doped nitride layer may include one or more N-type impurities of Group IV elements. The N-type impurities may include one or a combination of Si, Ge, and Sn. In this embodiment, the first semiconductor layer 121 is doped with Al to facilitate ultraviolet light emission from the ultraviolet light-emitting diode. In some embodiments, a buffer layer is provided between the first semiconductor layer 121 and the substrate 110 to mitigate the lattice mismatch between the substrate 110 and the N-type semiconductor layer. The buffer layer may include an unintentionally doped AlN layer (u-AlN) or an unintentionally doped AlGaN layer (u-AlGaN). In other embodiments, the first semiconductor layer 121 may be bonded to the substrate 110 via an adhesive layer.

[0049] The light-emitting layer 122 may be a quantum well structure (Quantum Well, abbreviated as QW). In some embodiments, the light-emitting layer 122 may also be a multiple quantum well structure (Multiple Quantum Well, abbreviated as MQW), wherein the multiple quantum well structure includes multiple quantum well layers (Wel1) and multiple quantum barrier layers (Barrier) alternately arranged in a repeated manner, for example, it may be a multiple quantum well structure such as GaN / AlGaN, InAlGaN / InAlGaN or InGaN / AlGaN. In addition, the composition and thickness of the well layer in the light-emitting layer 122 determine the wavelength of the generated light. In order to improve the luminous efficiency of the light-emitting layer 122, it can be achieved by changing the depth of the quantum well, the number of layers, thickness and / or other characteristics of the paired quantum wells and quantum barriers in the light-emitting layer 122. In particular, by adjusting the composition of the well layer, a light-emitting layer 122 that generates different colors of light such as ultraviolet light, blue light, and green light can be provided. In this embodiment, the emission wavelength range of the ultraviolet light emitting diode 1 is 200 nm-420 nm, that is, the emission wavelength range of the light emitting layer 122 is 200 nm-420 nm.

[0050] The second semiconductor layer 123 may be a P-type semiconductor layer that can provide holes to the light-emitting layer 122 under the action of a power source. In some embodiments, the second semiconductor layer 123 includes a P-type doped nitride layer. The P-type doped nitride layer may include one or more P-type impurities of Group II elements. The P-type impurities may include one or a combination of Mg, Zn, and Be.

[0051] Although the first semiconductor layer 121 and the second semiconductor layer 123 can each be a single-layer structure, the present invention is not limited thereto. The first semiconductor layer 121 and the second semiconductor layer 123 can also be a multi-layer structure having different compositions and can also include a superlattice layer. In addition, the configuration of the semiconductor stack 120 is not limited thereto, and other types of semiconductor stacks 120 can be selected based on actual needs. For example, in other embodiments, when the first semiconductor layer 121 is doped with p-type impurities, the second semiconductor layer 123 can be doped with n-type impurities, that is, the first semiconductor layer 121 is a p-type semiconductor layer and the second semiconductor layer 123 is an n-type semiconductor layer.

[0052] Next, see Figure 7 , an etching process is used to remove a portion of the second semiconductor layer 123 and the light emitting layer 122 , and expose the first semiconductor layer 121 .

[0053] Next, see Figure 8 A current blocking layer (not shown), a current diffusion layer (not shown), a first contact electrode 131 and a second contact electrode 132 are formed on the semiconductor stack 120 .

[0054] The first contact electrode 131 directly contacts the first semiconductor layer 121. The first contact electrode 131 is selected from one or more of Cr, Pt, Au, Ni, Ti, and Al. Because the first semiconductor layer 121 has a high Al content, the first contact electrode 131 needs to be fused at high temperature to form an alloy after being deposited on the mesa to establish a good ohmic contact with the first semiconductor layer 121. The first contact electrode 131 can have a single-layer, double-layer, or multi-layer structure, for example, a stacked structure of Ti / Al, Ti / Al / Au, Ti / Al / Ni / Au, Cr / Al / Ti / Au, or Ti / Al / Au / Pt.

[0055] The second contact electrode 132 directly contacts the second semiconductor layer 123. This second contact electrode 132 can be made of a transparent conductive oxide material or a metal material, such as a metal alloy such as NiAu, NiAg, or NiRh. Its thickness is preferably 30 nm or less to minimize its light absorption rate. In a preferred embodiment, the wavelength emitted by the light-emitting layer 122 is 280 nm or less. The second contact electrode 132 is made of ITO with a thickness of 5 to 20 nm, for example, 10 to 15 nm. In this case, the ITO layer's absorption rate of light emitted by the light-emitting layer 122 can be reduced to less than 40%.

[0056] Next, see Figure 9 An insulating layer 150 is further coated on the contact electrodes, the exposed upper surface 124 of the semiconductor stack 120, and the sidewalls. In existing coating processes, such as evaporation or sputtering, the thickness of the insulating layer 150 on the sidewalls of the semiconductor stack 120 is typically thinner than on the upper surface 124 of the semiconductor stack 120 and the upper surface of the substrate 110 due to the shadowing effect. As a result, the thickness on the sidewalls of the semiconductor stack 120 is 40-90% of the thickness of the upper surface 124 of the semiconductor stack 120. The insulating layer 150 has an opening to expose the first contact electrode 131 and the second contact electrode 132. The insulating layer 150 comprises a non-conductive material. The non-conductive material is preferably an inorganic material or a dielectric material. Inorganic materials include silica gel or glass, and dielectric materials include aluminum oxide, silicon nitride, silicon oxide, titanium oxide, or magnesium fluoride. For example, the insulating layer 180 may be silicon dioxide, silicon nitride, titanium oxide, tantalum oxide, niobium oxide, barium titanate, or a combination thereof. The combination may be, for example, a Bragg reflector (DBR) formed by repeatedly stacking two materials. In some embodiments, the insulating layer 150 is preferably a reflective insulating layer, which can effectively improve the light extraction efficiency of the LED.

[0057] A first pad electrode 141 and a second pad electrode 142 are formed on the insulating layer 150 through photolithography and evaporation processes. The first pad electrode 141 is electrically connected to the first contact electrode 131 through an opening extending through the insulating layer 150, and the second contact electrode 142 is electrically connected to the second contact electrode 132 through an opening extending through the insulating layer 150. The minimum horizontal spacing between the first pad electrode 141 and the second pad electrode 142 on the insulating layer 150 is preferably greater than 5 μm, for example, 20 to 40 μm, 40 to 60 μm, or 60 to 80 μm. The material can be a combination of metals such as Cr, Pt, Au, Ti, Ni, and Al. Preferably, the electrode has a multilayer structure, with the surface layer preferably made of Au.

[0058] Step S120: Provide multiple laser beams focused on the inside of the substrate 110, including a first laser beam and a second laser beam, wherein the first laser beam is focused closer to the lower surface 125 of the semiconductor stack 120 than the second laser beam. Specifically, the first laser beam with the first pulse energy forms the first laser cutting line 100 inside the substrate 110, see Figure 10 A second laser beam with a second pulse energy is used to form a second laser cutting line 200 inside the substrate 110, see Figure 11 .

[0059] Please see Figure 2 The laser marks on the first laser cutting line 100 are quasi-circular explosion points, and the laser marks on the second laser cutting line 200 are thin strip explosion points. The first laser cutting line 100 includes the laser cutting line closest to the lower surface of the semiconductor stack, that is, the laser marks on the laser cutting line closest to the lower surface of the semiconductor stack are quasi-circular explosion points. Figure 3 (a) A light ray 1 emitted from the light emitting layer 122 is incident on a thin laser scratch with an incident angle of θ1. When θ1 is greater than the critical angle, light reflection occurs and oscillates inside the LED chip. The same light ray 2 emitted from the light emitting layer 122 is incident on a circular laser scratch with an incident angle of θ2. Figure 3As can be clearly seen in (b), θ1 is greater than θ2. The probability of θ1 exceeding the critical angle is greater than θ2, making ray 1 more likely to be fully emitted. Therefore, a quasi-circular laser scratch is more conducive to light emission. Furthermore, UV LEDs emit more lateral light, and a quasi-circular laser spot facilitates light emission, thus improving brightness. Changing the emission angle results in a more uniform light pattern. When a quasi-circular laser scratch is made on the sidewall, as shown in the figure, ray 2 will exit laterally. It should be noted that the quasi-circular explosion point described in the present invention is a explosion point close to a circle, and is not limited to a completely circular explosion point. Based on factors such as actual process conditions, it is difficult to make the laser scratches completely identical and completely circular explosion points, but it is possible to make the shapes of the explosion points relatively uniform and close to a circle. In some specific embodiments, the quasi-circular shape has a major axis and a minor axis, and the ratio of the minor axis to the major axis is not greater than 1:1.5. More preferably, the ratio can be 1:1 to 1:1.3, such as 1:1, 1:1.1 or 1:1.25. When the ratio is closer to 1:1, the probability that the incident angle θ of the light emitted from the light-emitting layer 122 incident on the quasi-circular laser scratch is less than the critical angle is greater, and the probability of full emission of the light 1 is lower, which is more conducive to the emission of light. Please refer to Figure 4 Examples of quasi-circular burst points include but are not limited to the following: (1) circular burst points with radial / serrated edges, (2) elliptical burst points with radial / serrated edges and a ratio of the short axis to the long axis not greater than 1:1.5, and (3) circular burst points with irregular / uneven edges. All of the above belong to the quasi-circular burst points mentioned in this case. Specifically, the thin strip-shaped burst points described in the present invention also have a long axis and a short axis, and the ratio of the short axis to the long axis is greater than 1:1.5. More preferably, the ratio can be 1:1.5 to 1:2, which reduces the difficulty of cracking while increasing light emission and improving the brightness of the chip.

[0060] Further, in some embodiments, see Figure 5The first laser beam is focused within the substrate using a single-blade multi-focus method to form X rows of first laser cutting lines 100. The second laser beam is focused within the substrate using a single-blade multi-focus method to form Y rows of second laser cutting lines 200, where X ≥ 2 and Y ≥ 1. By replacing a single high-energy first laser cutting line close to the semiconductor stack with multiple low-energy first laser cutting lines, even if the first pulse energy is increased to a certain extent, the energy of any low-energy first laser cutting line is necessarily lower than that of the single high-energy first laser cutting line. This allows the laser scratch to be closer to the semiconductor stack, solving the problem of AlGaN-based UV LEDs, which have increased substrate thickness to improve light extraction, due to the heat sensitivity of the epitaxial layer, making it difficult to laser scratch close to the epitaxial layer, which can easily lead to poor cleavage yield. Furthermore, the closer the laser scratch explosion point is to the light-emitting layer, the smaller the incident angle of the light, which is more conducive to the emission of light close to the light-emitting layer and improves light extraction. Furthermore, this method increases the number of laser scratches on the chip side, increases the side roughening, and further improves the chip brightness. Among them, the first laser cutting line 100 is preferably 3≤X≤5. When too many rows of first laser cutting lines 100 are formed, if the energy of the first laser cutting lines 100 in each row is too low, it will make it difficult to split; if the energy of the first laser cutting lines 100 in each row is too high, the total energy will be too high, which will easily damage the semiconductor stack 120.

[0061] Please see Figure 12 Each row of laser cutting lines includes a plurality of first cutting lines 101 and a plurality of second cutting lines 102 . The first cutting lines 101 and the second cutting lines 102 may be substantially perpendicular to each other.

[0062] In some embodiments, the energy range of the first pulse energy is no greater than 1W, preferably 0.3~0.7W. When the first pulse energy is too low, when forming X rows of first laser cutting lines 100, the energy of each row of first laser cutting lines 100 is too low, which will make it difficult to split; when the first pulse energy is too high, it is easy to damage the semiconductor stack 120. The energy range of the second pulse energy is no greater than 1W, preferably 0.3~0.7W. The energy of the first laser beam can be greater than or less than the energy of the second laser beam. When the energy of the first laser beam is less than the energy of the second laser beam, the first laser scratch 100 can be closer to the semiconductor stack 120, thereby achieving the effect of further improving the brightness of the product; when the energy of the second laser beam is less than the energy of the first laser beam, it is avoided that the second laser beam energy is too high, which will cause the bottom surface of the substrate 110 to be uneven.

[0063] In some embodiments, the distance between the first laser beam and the lower surface 125 of the semiconductor stack 120 is not less than 60 μm and not more than 130 μm. The distance between the second laser beam and the lower surface of the semiconductor stack is not less than 100 μm and not more than 210 μm. In this embodiment, the first laser beam is focused inside the substrate 110 to form several rows of low-energy first laser cutting lines 100, thereby bringing the laser scratches closer to the semiconductor stack 120 and improving the brightness of the chip.

[0064] Step S130: Separate the LED wafer into several LED chips. Figure 13 The substrate 110 has X rows of first laser cutting lines 100 formed by the first laser beam and Y rows of second laser cutting lines 200 formed by the second laser beam.

[0065] In some embodiments, the first laser cutting line 100 is located closer to the lower surface 125 of the semiconductor stack 120 than the second laser cutting line 200. The distance between the first laser cutting line 100 and the lower surface 125 of the semiconductor stack 120 is not less than 60 μm and not more than 130 μm. The distance between the second laser cutting line 200 and the lower surface 125 of the semiconductor stack 120 is not less than 100 μm and not more than 210 μm. The shortest distance between the first laser cutting line 100 and the lower surface 125 of the semiconductor stack 120 is defined as a first height D1. For example, in some embodiments, when X=1, the energy range of the first laser beam is 0.4W-0.7W, and the range of the first height D1 is 120-130 μm; when X=2, the energy range of the first laser beam is 0.4W-0.72W, and the range of the first height D1 is 110-120 μm; when X=5, the energy range of the first laser beam is 0.4W-0.75W, and the range of the first height D1 is 90-110 μm.

[0066] In some embodiments, the laser marks are evenly spaced horizontally on the substrate 110. Specifically, the first laser marks 100 are spaced horizontally on the substrate 110 in a range of 1 μm to 16 μm, preferably 2 μm to 8 μm. The second laser marks 200 are spaced horizontally on the substrate 110 in a range of 2 μm to 18 μm, preferably 4 μm to 12 μm. By providing low-energy, closely spaced first laser marks, difficulty in chipping is avoided and the cleavage yield is improved.

[0067] In this embodiment, a single-blade multi-focus method is used to form the first laser cutting line 100, and the first laser cutting lines 100 are arranged in parallel, and the spacing in the vertical direction of the substrate 110 is uniformly arranged. The spacing between two adjacent first laser cutting lines 100 in the vertical direction of the substrate 110 is in the range of 5μm to 25μm. Preferably, the spacing range is 9 to 16μm. The second laser cutting lines 200 are arranged in parallel, and the spacing between two adjacent second laser cutting lines 200 in the vertical direction of the substrate 110 is 35μm to 100μm. By setting a low-energy, densely spaced first laser scratch, it is avoided that it is difficult to split and the splitting yield is improved.

[0068] In some embodiments, the thickness of the substrate 110 is not less than 270 μm. In a specific embodiment, when the thickness of the substrate 110 is 300 μm, the first laser beam is focused inside the substrate to form 2 to 4 rows of first laser cutting lines 100. For example, the first laser beam is focused inside the substrate to form 3 rows of first laser cutting lines 100 and 2 rows of second laser cutting lines 200. In a specific embodiment, when the thickness of the substrate 110 is 400 μm, the first laser beam is focused inside the substrate to form 3 to 7 rows of first laser cutting lines 100. For example, the first laser beam is focused inside the substrate to form 5 rows of first laser cutting lines 100 and 3 rows of second laser cutting lines 200.

[0069] In some embodiments, the laser scratch area on the side of substrate 110 is greater than 20%, preferably 30%-60%. If the laser scratch area on the side of substrate 110 is too small, it will be difficult to break the wafer. If the laser scratch area on the side of substrate 110 is too large, it will easily damage semiconductor stack 120, and the manufacturing process time will be too long, wasting production capacity. Example

[0070] Figure 14 A schematic cross-sectional structure diagram of another ultraviolet LED chip implemented according to the present invention is shown.

[0071] In this embodiment, a multi-tool multi-focus method is used to form an X-row first laser cutting line 100, where X ≥ 2, and the first laser cutting lines 100 are arranged in parallel. The spacing in the vertical direction of the substrate 110 is a gradient arrangement. Specifically, the spacing of the first laser cutting lines 100 in the vertical direction of the substrate 110 gradually increases as it moves away from the lower surface 125 of the semiconductor stack 120. As shown in the figure, the first laser cutting lines 100 are M1, M2, M3, and so on as they move away from the lower surface 125 of the semiconductor stack 120. Under the energy condition of equal first pulse energy, Compared with the first laser cutting lines 100 with uniform spacing in the vertical direction of the substrate 110, the distance between the first laser cutting lines 100 such as M2 and M3 arranged in a gradient manner and the lower surface 125 of the semiconductor stack 120 will be larger, that is, the degree of damage to the semiconductor stack 120 caused by the first laser cutting lines 100 such as M2 and M3 will be smaller. Therefore, the M1 first laser cutting line 100 can be set to be closer to the lower surface 125 of the semiconductor stack 120, that is, the first height D1 can be smaller, which further improves the chip splitting yield and chip brightness to a certain extent. Example

[0072] Figure 15 A schematic cross-sectional structure diagram of another ultraviolet LED chip implemented according to the present invention is shown.

[0073] In this embodiment, a single-blade multi-focus or multi-blade multi-focus method is used to form X rows of first laser cutting lines 100 and Y rows of second laser cutting lines 200, where X ≥ 2 and Y ≥ 1. The laser cutting lines are arranged in parallel, and the first laser cutting lines 100 and the Y rows of second laser cutting lines 200 are arranged in a cross pattern in the vertical direction of the substrate 110. This improves light emission to a certain extent, thereby further improving chip brightness. Example

[0074] Figure 16 A schematic cross-sectional structure diagram of another ultraviolet LED chip implemented according to the present invention is shown.

[0075] In this embodiment, a single-blade multi-focus or multi-blade multi-focus method is used to form an X-row first laser cutting line 100 and a Y-row second laser cutting line 200, where X≥2 and Y≥1. The laser cutting lines are all arranged in parallel, and the first laser cutting line 100 and the Y-row second laser cutting line 200 are arranged crosswise in the vertical direction of the substrate 110. For example, the area of the first laser scratch on the side of the substrate 110 is more than 1 times the area of the second laser scratch on the side of the substrate 110, that is, the area of the quasi-circular laser scratch on the side of the substrate 110 is more than 1 times the area of the thin strip laser scratch on the side of the substrate 110. More preferably, the area of the quasi-circular laser scratch on the side of the substrate 110 is more than 2 times the area of the thin strip laser scratch on the side of the substrate 110. According to the above analysis, the quasi-circular laser explosion point contributes to the emission of light. In this embodiment, further increasing the proportion of quasi-circular laser scratches can further increase the emission of light, which is conducive to improving brightness.

[0076] 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.

[0077] 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 method for manufacturing an ultraviolet light-emitting diode, comprising the steps of:

1. Provide an LED wafer, comprising a substrate and a semiconductor stack located on an upper surface of the substrate, wherein the semiconductor stack has a lower surface proximal to the substrate and an upper surface opposite thereto, and the semiconductor stack includes, in order from the lower surface to the upper surface, a first semiconductor layer, a light-emitting layer, and a second semiconductor layer; 2. Provide a laser beam that is irradiated multiple times and focused on the inside of the substrate, including a first laser beam and a second laser beam, wherein the position where the first laser beam is focused is closer to the lower surface of the semiconductor stack than the position where the second laser beam is focused, the first laser beam is focused on the inside of the substrate to form a first laser cutting line, the laser scratch of the first laser cutting line is quasi-circular, the quasi-circular has a major axis and a minor axis, and the ratio of the minor axis to the major axis of the quasi-circular is not greater than 1:1.5; the second laser beam is focused on the inside of the substrate to form a second laser cutting line, the laser scratch of the second laser cutting line is in the shape of a thin strip, the thin strip has a major axis and a minor axis, and the ratio of the minor axis to the major axis of the thin strip is greater than 1:1.5, and the first laser cutting line includes the laser cutting line closest to the lower surface of the semiconductor stack; 3. Separate the LED wafer into several LED chips.

2. The method for manufacturing an ultraviolet light emitting diode according to claim 1, wherein: The first laser beam forms X rows of first laser cutting lines inside the substrate, where X≥2.

3. The method for manufacturing an ultraviolet light emitting diode according to claim 1, wherein: The distance from the first laser beam to the lower surface of the semiconductor stack is not less than 60 μm and not more than 130 μm.

4. The method for manufacturing an ultraviolet light emitting diode according to claim 1, wherein: The second laser beam forms Y rows of second laser cutting lines inside the substrate, where Y≥1.

5. The method for manufacturing an ultraviolet light emitting diode according to claim 1, wherein: The distance between the second laser beam and the lower surface of the semiconductor stack is not less than 100 μm and not more than 210 μm.

6. An ultraviolet light-emitting diode comprising a substrate and a semiconductor stack located on an upper surface of the substrate, the semiconductor stack having a lower surface proximal to the substrate and an upper surface opposite thereto, the semiconductor stack comprising, from the lower surface to the upper surface, a first semiconductor layer, a light-emitting layer, and a second semiconductor layer, characterized in that: The substrate has a first laser cutting line formed by a first laser beam and a second laser cutting line formed by a second laser beam, wherein the position of the first laser cutting line is closer to the lower surface of the semiconductor stack than the position of the second laser cutting line, the laser scratch of the first laser cutting line is quasi-circular, the quasi-circular has a major axis and a minor axis, and the ratio of the minor axis to the major axis of the quasi-circular is not greater than 1:1.5; the laser scratch of the second laser cutting line is in the shape of a thin strip, the thin strip has a major axis and a minor axis, and the ratio of the minor axis to the major axis of the thin strip is greater than 1:1.

5.

7. The ultraviolet light emitting diode according to claim 6, characterized in that: The substrate has X rows of first laser cutting lines formed by the first laser beam and Y rows of second laser cutting lines formed by the second laser beam, where X≥2 and Y≥1.

8. The ultraviolet light emitting diode according to claim 6, characterized in that: The distance from the first laser cutting line to the lower surface of the semiconductor stack is not less than 60 μm and not more than 130 μm.

9. The ultraviolet light emitting diode according to claim 6, characterized in that: The distance from the second laser cutting line to the lower surface of the semiconductor stack is not less than 100 μm and not more than 210 μm.

10. The ultraviolet light emitting diode according to claim 6, characterized in that: The laser scratches on the first laser cutting line are discontinuous.

11. The ultraviolet light emitting diode according to claim 6, characterized in that: The laser scratches of the first laser cutting line are evenly distributed in the horizontal direction of the substrate, and the laser scratches of the first laser cutting line are in the horizontal direction of the substrate. The interval range of the laser scratches is 1 μm to 16 μm.

12. The ultraviolet light emitting diode according to claim 6, characterized in that: The laser scratches of the second laser cutting line are evenly distributed in the horizontal direction of the substrate, and the intervals between the laser scratches of the second laser cutting line in the horizontal direction of the substrate range from 2 μm to 18 μm.

13. The ultraviolet light emitting diode according to claim 6, characterized in that: The first laser cutting lines are arranged in parallel, and the spacing between them in the vertical direction of the substrate is uniform or gradient.

14. The ultraviolet light emitting diode according to claim 13, characterized in that: The spacing between the first laser cutting lines in the vertical direction of the substrate gradually increases as the spacing is away from the lower surface of the semiconductor stack.

15. The ultraviolet light emitting diode according to claim 13, characterized in that: The distance between two adjacent first laser cutting lines in the vertical direction of the substrate is 5 μm to 25 μm.

16. The ultraviolet light emitting diode according to claim 6, characterized in that: The second laser cutting lines are arranged in parallel, and a distance between two adjacent second laser cutting lines in a vertical direction of the substrate is 35 μm to 100 μm.

17. The ultraviolet light emitting diode according to claim 6, characterized in that: The thickness of the substrate is not less than 270 μm.

18. The ultraviolet light emitting diode according to claim 6, characterized in that: The laser scratches account for more than 20% of the area of the side surface of the substrate.

19. An ultraviolet light emitting device, characterized in that: The ultraviolet light emitting device adopts the ultraviolet light emitting diode according to any one of claims 6 to 18, or adopts the ultraviolet light emitting diode manufactured by the method for manufacturing the ultraviolet light emitting diode according to any one of claims 1 to 5.

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