LED wafer and processing method

Abstract

According to the LED wafer and the processing method provided by the invention, the aluminum nitride coverage area is arranged on the front surface and / or the back surface of the sapphire substrate to cover the top points of the conical bulge structures, so that the problem of excessive decomposition of gallium nitride caused by refractive index difference in a laser lift-off process is reduced, the risk of chip cracks is reduced, and the yield of the LED wafer is improved. And the electrical property and the light extraction efficiency of the LED chip are improved.

Description

Technical Field

[0001] This application relates to the field of display panel technology, and in particular to an LED wafer and its processing method. Background Technology

[0002] Micro-LED, as a next-generation display technology, boasts significant advantages such as high photoelectric efficiency, high brightness, high contrast, and low power consumption. Combined with flexible panels, it can also achieve flexible displays, demonstrating broad application prospects. A crucial step in the manufacturing process of Micro-LED display panels is transferring the red, green, and blue LED chips from their respective growth substrates to the display backplane. To improve the light extraction efficiency of the LED chips, the industry often uses patterned sapphire substrates (PSS), whose surface features periodic micro-nano patterns with conical protrusions. This increases light scattering and reflection within the substrate, allowing more photons to escape from the chip.

[0003] However, the unique morphology of the patterned sapphire substrate introduced new problems during the subsequent laser lift-off process. When the laser beam irradiates the sapphire substrate from behind perpendicularly, the laser beam is refracted and deflected upon entering the gallium nitride (GaN) buffer layer due to the refractive index difference between the sapphire and the GaN buffer layer. Laser irradiation causes chemical decomposition of the GaN buffer layer, generating nitrogen gas impact forces to peel the LED chip from the sapphire substrate. However, the refracted nitrogen gas impact forces are directed in various directions, easily generating tearing forces on the LED chip, leading to cracks and affecting its electrical and optical extraction efficiency. Furthermore, at the tip of the conical protrusion structure, the morphological changes result in uneven laser energy density distribution, with some areas having excessively high energy density. This directly leads to excessive decomposition of GaN in these areas, further damaging the PSS tip morphology, roughening it, and potentially causing cracks. Summary of the Invention

[0004] The purpose of this application is to provide an LED wafer and a processing method that can improve the above-mentioned problems.

[0005] The embodiments of this application are implemented as follows:

[0006] In a first aspect, this application provides an LED wafer, comprising: a sapphire substrate and an LED chip grown on the sapphire substrate. The sapphire substrate includes a front surface and a back surface disposed opposite to each other. A plurality of conical protrusions are arranged in an array on the front surface. The LED chip is grown on the front surface. A plurality of aluminum nitride covering regions are also arranged in an array on the front surface and / or the back surface. The orthographic projection area of ​​each aluminum nitride covering region on the back surface is greater than or equal to a preset area threshold and covers the orthographic projection position of the vertex of the conical protrusion on the back surface. The sapphire substrate includes a front surface and a back surface disposed opposite to each other and parallel to each other. A plurality of conical protrusions are etched in an array on the front surface. The orthographic projection area of ​​the top region of each conical protrusion on the back surface is equal to the preset area threshold. Each top region is sputtered with aluminum nitride material to form an aluminum nitride covering region.

[0007] It is understood that this application provides an LED wafer by providing an aluminum nitride (ANT) covering region on the front and / or back surfaces of a sapphire substrate, covering the apex of a conical protrusion structure. This reduces the problem of excessive gallium nitride decomposition due to refractive index differences during subsequent laser lift-off, lowers the risk of chip cracking, and improves the electrical properties and optical extraction efficiency of the LED chip. In this embodiment, the ANT covering region is sputtered on the top of multiple conical protrusion structures, changing the laser energy distribution at the location where the laser passes through the conical protrusion structure. This reduces the laser energy density at the tip of the conical protrusion structure, decreasing the destructive power of the laser on the tip of the conical protrusion structure. This allows for laser lift-off while avoiding crack formation that could damage electrical properties and morphological changes that reduce optical extraction efficiency, further improving the yield of laser lift-off and transfer. When lifting the LED wafer provided in this embodiment, the laser beam preferably irradiates the sapphire substrate at a vertical angle.

[0008] Secondly, this application provides an LED wafer, comprising: a sapphire substrate and an LED chip grown on the sapphire substrate. The sapphire substrate includes a front surface and a back surface disposed opposite to each other. A plurality of conical protrusions are arranged in an array on the front surface. The LED chip is grown on the front surface. A plurality of aluminum nitride covering regions are also arranged in an array on the front surface and / or the back surface. The orthographic projection area of ​​each aluminum nitride covering region on the back surface is greater than or equal to a preset area threshold and covers the orthographic projection position of the vertex of the conical protrusion on the back surface. The sapphire substrate includes a front surface and a back surface disposed opposite to each other and parallel to each other. A plurality of conical protrusions are etched in an array on the front surface. An array of circular regions is formed on the back surface. The orthographic projection area of ​​each circular region on the back surface is equal to a preset area threshold, and the orthographic projection position of the vertex of the conical protrusion on the back surface is located at the center point of the orthographic projection area of ​​the circular region on the back surface. Each circular region is sputtered with aluminum nitride material to form an aluminum nitride covering region.

[0009] It is understood that in this embodiment, an array of aluminum nitride covering regions is prepared on the back side of the sapphire substrate according to the arrangement of the conical protrusions. The aluminum nitride covering regions change the laser energy distribution at the location where the laser passes through the conical protrusions, reducing the laser energy density at the tip of the conical protrusions and decreasing the laser's destructive ability at the tip of the conical protrusions. This allows for laser lift-off while avoiding crack formation that could damage the electrical properties and morphological changes that would reduce light extraction. The aluminum nitride covering regions can be selected as circular patterns of 1.3-1.5 μm, and the film thickness of the aluminum nitride covering regions can be 5-10 nm. When lifting the LED wafer provided in this embodiment, the laser beam is preferably irradiated onto the sapphire substrate at a vertical angle.

[0010] Thirdly, this application provides an LED wafer, comprising: a sapphire substrate and an LED chip grown on the sapphire substrate, the sapphire substrate comprising a front surface and a back surface disposed opposite to each other, a plurality of conical protrusions arranged in an array on the front surface, the LED chip grown on the front surface, and a plurality of aluminum nitride covering regions arranged in an array on the front surface and / or the back surface, wherein the orthogonal projection area of ​​each aluminum nitride covering region on the back surface is greater than or equal to a preset area threshold and covers the orthogonal projection position of the vertex of the conical protrusion on the back surface;

[0011] The sapphire substrate includes a front surface and a back surface arranged opposite to each other, and multiple conical protrusions are etched in an array on the front surface;

[0012] Multiple frustum-shaped protrusions are etched on the back surface in an array. The area of ​​the top surface of the frustum-shaped protrusions is greater than a preset area threshold. The vertex of the conical protrusion is located at the center of the top surface in the orthographic projection of the top surface.

[0013] The inclination angle i of the sidewall of the frustum-shaped protrusion relative to the back surface satisfies the following formula:

[0014]

[0015] Wherein, θ1 represents the incident angle of the light beam passing through the sidewall of the frustum-shaped protrusion when it irradiates the sapphire substrate perpendicular to the back surface; φ1 represents the refraction angle of the light beam entering the sapphire substrate through the sidewall of the frustum-shaped protrusion; α2 represents the incident angle of the light beam passing through the sidewall of the conical protrusion; β2 represents the refraction angle of the light beam entering the LED chip through the sidewall of the conical protrusion; here, β2 is defined as e, where e represents the tilt angle of the sidewall of the conical protrusion relative to the front surface; i represents the tilt angle of the sidewall of the frustum-shaped protrusion relative to the back surface; n1 represents the refractive index of air; n2 represents the refractive index of the sapphire substrate; and n3 represents the refractive index of gallium nitride, the material in the LED chip.

[0016] The height h5 of the frustum-shaped protrusion relative to the back surface satisfies the following formula:

[0017]

[0018] Wherein, h5 represents the height of the frustum-shaped protrusion relative to the back surface, h3 represents the height of the conical protrusion, and S represents a preset area threshold.

[0019] The diameter L1 of the top surface of the frustum-shaped protrusion satisfies the following formula:

[0020]

[0021] Where h4 represents the thickness of the sapphire substrate, that is, the distance between the bottom of the frustum-shaped protrusion and the bottom of the conical protrusion;

[0022] Each of the top surfaces is sputtered with aluminum nitride material to form an aluminum nitride-covered area.

[0023] It is understood that when peeling off the LED wafer provided in this embodiment, the laser beam preferably irradiates the sapphire substrate at a vertical angle. When it irradiates the inclined surface of the frustum-shaped protrusion structure, the laser beam undergoes a first refraction and enters the sapphire substrate at an angle φ1. When the beam irradiates the sidewall of the conical protrusion structure, it undergoes a second refraction and enters the epitaxial layer of the LED chip at an angle β2. Since the refractive indices of air, the sapphire substrate, and the epitaxial layer gradually decrease, the frustum-shaped protrusion structure can be designed with specific parameters so that the beam entering the LED chip at angle β2 exits vertically, no longer forming a component oriented horizontally. This embodiment avoids the tearing force generated on the LED chip due to the different directions of nitrogen impact, which could lead to cracks in the chip.

[0024] Fourthly, this application provides an LED wafer, comprising: a sapphire substrate and an LED chip grown on the sapphire substrate, the sapphire substrate comprising a front surface and a back surface disposed opposite to each other, a plurality of conical protrusions arranged in an array on the front surface, the LED chip grown on the front surface, and a plurality of aluminum nitride covering regions arranged in an array on the front surface and / or the back surface, wherein the orthogonal projection area of ​​each aluminum nitride covering region on the back surface is greater than or equal to a preset area threshold and covers the orthogonal projection position of the vertex of the conical protrusion on the back surface;

[0025] The sapphire substrate includes a front surface and a back surface that are arranged opposite to each other and parallel to each other, and a plurality of conical protrusions are etched on the front surface.

[0026] The back surface is prepared with an array of circular aluminum nitride covering areas, such that the vertex of the conical protrusion structure is located at the center point of the corresponding aluminum nitride covering area on the back surface, and the area of ​​the aluminum nitride covering area is greater than a preset area threshold.

[0027] The diameter L2 of the aluminum nitride-covered area satisfies the following formula:

[0028]

[0029] Where S represents a preset area threshold, h3 represents the height of the conical protrusion structure, h4 represents the thickness of the sapphire substrate, i.e., the distance between the bottom of the frustum-shaped protrusion structure and the bottom of the conical protrusion structure, α3 represents the incident angle of the light beam through the sidewall of the conical protrusion structure, β3 represents the refraction angle of the light beam through the sidewall of the conical protrusion structure into the LED chip, and here β3 is defined as e, where e represents the tilt angle of the sidewall of the conical protrusion structure relative to the front surface, n2 represents the refractive index of the sapphire substrate, and n3 represents the refractive index of gallium nitride material in the LED chip;

[0030] A first semi-circular transparent layer formed of a first light-transmitting material is prepared on the back surface. The first light-transmitting material transmits a first wavelength beam and reflects other wavelength beams. A second semi-circular transparent layer formed of a second light-transmitting material is prepared on the back surface. The second light-transmitting material transmits a second wavelength beam and reflects other wavelength beams. The first semi-circular transparent layer and the second semi-circular transparent layer are spliced ​​together to form a complete ring around the aluminum nitride covered area. The inner diameter of the complete ring is the diameter L2 of the aluminum nitride covered area.

[0031] The width W of the complete circular ring satisfies the following formula:

[0032]

[0033] The aluminum nitride-covered area is coated with a third reflective material, which is used to reflect the first band beam and the second band beam and transmit other band beams.

[0034] Fifthly, this application provides an LED wafer processing method, which includes steps S1 to S4, wherein S1, S2, etc. are merely step identifiers, and the execution order of the method does not necessarily follow the numerical order from smallest to largest. For example, step S2 can be executed first and then step S1 can be executed. This application does not impose any restrictions.

[0035] S1, Prepare an LED wafer as described in any one of the first to fourth aspects;

[0036] S2, attach the side of the LED chip in the LED wafer away from the sapphire substrate to a temporary substrate;

[0037] S3, at least one laser beam is provided to irradiate the sapphire substrate, the LED chip on the sapphire substrate is peeled off onto a temporary substrate, and the light-emitting surface of the LED chip on the temporary substrate is pre-processed;

[0038] S4, using at least three of the LED chips to fabricate an LED display unit, and then transferring the LED display unit to a display backplane for encapsulation to obtain an LED display; or, directly transferring the LED chips on the temporary substrate to the display backplane for encapsulation to obtain an LED display.

[0039] In an optional embodiment, when an LED wafer as described in any one of the first to third aspects is fabricated, the step of providing at least one laser beam to irradiate the sapphire substrate includes: providing a laser beam to irradiate the sapphire substrate at a vertical angle.

[0040] In an optional embodiment, when an LED wafer as described in any of the fourth aspects is fabricated, the step of providing at least one laser beam to irradiate the sapphire substrate includes:

[0041] A first laser beam of a first wavelength is provided to irradiate the sapphire substrate at a first angle, the first laser beam being emitted in a horizontal direction toward a first direction;

[0042] A second laser beam of a second wavelength is provided to irradiate the sapphire substrate at a second angle. The second laser beam is emitted in a horizontal direction toward a second direction, which is opposite to the first direction.

[0043] A third laser beam of the third band is provided to irradiate the sapphire substrate at a vertical angle.

[0044] Optionally, the first angle is equal to the second angle, and satisfies the following formula:

[0045]

[0046] Wherein, θ2 represents the angle values ​​of the first angle and the second angle.

[0047] It is understood that this embodiment provides three different wavelengths of laser beams to irradiate the sapphire substrate. The third laser beam of the third wavelength irradiates the sapphire substrate at a vertical angle. After passing through the aforementioned third reflective material coating layer, it is weakened by the aluminum nitride covering area before entering the top of the conical protrusion structure. The aluminum nitride covering area changes the laser energy distribution of the third laser beam passing through the top position, reducing the laser energy density at the top of the conical protrusion structure and reducing the destructive ability of the laser on the top position of the conical protrusion structure. The first laser beam of the first wavelength and the second laser beam of the second wavelength irradiate the sapphire substrate in different directions at an angle θ2, respectively. Due to the coating of various light-transmitting and reflective materials, the first laser beam and the second laser beam can only enter the sapphire substrate from the coating areas of the first and second light-transmitting materials, respectively. After being refracted twice by the back surface and the sidewall of the conical protrusion structure, they enter the LED chip in a vertical direction and no longer form a component in the horizontal direction. Therefore, the solution in this embodiment can not only reduce the laser energy density at the top of the conical protrusion structure and reduce the destructive power of the laser on the top of the conical protrusion structure, but also avoid the tearing force generated on the LED chip due to the different directions of nitrogen impact force, which would cause cracks in the chip.

[0048] In optional embodiments of this application, the preset processing includes at least one of the following.

[0049] 1. A light-transmitting additional layer is prepared on the light-emitting surface of the LED chip. The refractive index of the light-transmitting additional layer is less than that of gallium nitride (GaN) and greater than a preset refractive index value. It is understood that the high refractive index of the gallium nitride material in the LED chip easily leads to total internal reflection at the interface, reducing light extraction efficiency. By preparing a light-transmitting additional layer with a refractive index lower than that of gallium nitride but higher than the preset value on the light-emitting surface of the LED chip, total internal reflection can be effectively reduced, allowing more light to escape smoothly from the chip. This light-transmitting additional layer can significantly improve the light extraction efficiency of the LED chip, increase luminous brightness, and maintain good light transmittance without affecting the overall performance of the LED chip.

[0050] 2. The light-emitting surface of the LED chip on the temporary substrate is subjected to accelerated oxidation treatment to form a gallium oxide layer on the light-emitting surface of the LED chip. It is understood that metallic gallium may remain during the laser stripping process, affecting the performance of the LED chip. By accelerating the oxidation treatment of the light-emitting surface of the LED chip, the residual metallic gallium can be converted into gallium oxide. Furthermore, gallium oxide has a lower refractive index than gallium nitride, which helps to improve light extraction efficiency. This treatment not only removes harmful residues but also further optimizes the optical performance of the LED chip and improves luminous efficiency by forming a low-refractive-index gallium oxide layer.

[0051] 3. A coating process is performed on the light-emitting surface of the LED chip on the temporary substrate to form a coating layer on the light-emitting surface of the LED chip. The refractive index of the coating layer is less than that of the gallium oxide layer but greater than a preset refractive index value. It can be understood that depositing a transparent film layer with a refractive index lower than gallium oxide but higher than the preset value on the light-emitting surface of the LED chip creates a gradually decreasing refractive index interface structure, which helps light escape from the chip more smoothly and reduces interface reflection loss. The coating process can further improve the light extraction efficiency of the LED chip and enhance the luminous effect. At the same time, the coating layer also plays a certain protective role and extends the lifespan of the LED chip.

[0052] In an optional embodiment of this application, the refractive index of the material layer in the LED display that is in contact with the light-emitting surface of the LED chip is less than the preset refractive index value. It can be understood that in this embodiment, the refractive index of the material layer in the LED display that is in direct contact with the light-emitting surface of the LED chip is designed to be less than the preset refractive index value. This design is based on optical principles; by reducing the refractive index of the contact layer, the reflection of light at the interface between the LED chip and the contact layer can be effectively reduced, promoting smoother light escape from the chip.

[0053] To make the above-mentioned objectives, features and advantages of this application more apparent and understandable, optional embodiments are described below in detail with reference to the accompanying drawings. Attached Figure Description

[0054] To more clearly illustrate the technical solutions of the embodiments of this application, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of this application and should not be regarded as a limitation of the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0055] Figure 1 This is a schematic diagram of the laser lift-off optical path for a conventional LED wafer;

[0056] Figure 2 This application provides a schematic diagram of the laser lift-off optical path for a first type of LED wafer;

[0057] Figure 3 This application provides a schematic diagram of the laser lift-off optical path for a second type of LED wafer;

[0058] Figure 4 This application provides a schematic diagram of the laser lift-off optical path for a third type of LED wafer;

[0059] Figure 5 yes Figure 4 A magnified view of a portion of the image;

[0060] Figure 6 This application provides a schematic diagram of the laser lift-off optical path for a fourth type of LED wafer;

[0061] Figure 7 yes Figure 6 A magnified view of a portion of the image;

[0062] Figure 8 This is a schematic diagram of the laser stripping process for LED wafers provided in this application. Detailed Implementation

[0063] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of this application.

[0064] like Figure 1As shown, to improve the light extraction efficiency of the LED chip 20, the industry often uses a patterned sapphire substrate 10, whose surface exhibits a periodic micro-nano pattern of conical protrusions 11 to increase light scattering and reflection within the substrate, allowing more photons to escape from the chip. At the tip of the conical protrusion, morphological changes lead to uneven distribution of laser energy density, with some areas having excessively high energy density. This directly results in excessive decomposition of gallium nitride in that region, which in turn damages the morphology of the PSS tip, roughening it and potentially causing cracks.

[0065] In a first aspect, this application provides an LED wafer, including a sapphire substrate and an LED chip 20 grown on the sapphire substrate. The sapphire substrate includes a front surface and a back surface disposed opposite to each other. A plurality of conical protrusion structures 11 are arranged in an array on the front surface. The LED chip is grown on the front surface. A plurality of aluminum nitride covering regions are also arranged in an array on the front surface and / or the back surface. The orthogonal projection area of ​​each aluminum nitride covering region on the back surface is greater than or equal to a preset area threshold and covers the orthogonal projection position of the vertex of the conical protrusion structure 11 on the back surface.

[0066] It is understood that the LED wafer provided in this application, by setting an aluminum nitride covering area on the front and / or back surface of the sapphire substrate to cover the apex of the conical protrusion structure 11, reduces the problem of excessive gallium nitride decomposition caused by refractive index difference during laser stripping, reduces the risk of chip cracking, and improves the electrical and optical extraction efficiency of the LED chip.

[0067] The sapphire substrate 10 includes a front surface and a back surface that are arranged opposite to each other and parallel to each other. Multiple conical protrusions 11 arranged in an array are etched on the front surface. The top region of each conical protrusion 11, when projected onto the back surface, has an area equal to a preset threshold. For example... Figure 2 As shown, the orthographic projection of the top region onto the back surface can be circular, with a diameter of k, satisfying the following equation: S = π·(k / 2). 2 Where S represents a preset area threshold. Each top region is sputtered with aluminum nitride material, forming a first aluminum nitride coverage area 113.

[0068] It is understood that in this embodiment, the first aluminum nitride covering area 113 is sputtered on the top of multiple conical protrusions 11, which changes the laser energy distribution at the location where the laser passes through the conical protrusions 11, reduces the laser energy density at the tip of the conical protrusions 11, and reduces the destructive ability of the laser at the tip of the conical protrusions 11. This allows the laser to achieve laser lift-off while avoiding crack generation that damages electrical properties and morphological changes that reduce light extraction, and further improves the yield of laser lift-off and transfer. When lifting the LED wafer provided in this embodiment, the laser beam preferably irradiates the sapphire substrate 10 at a vertical angle.

[0069] Secondly, this application provides an LED wafer, including a sapphire substrate and an LED chip 20 grown on the sapphire substrate. The sapphire substrate includes a front surface and a back surface disposed opposite to each other. A plurality of conical protrusion structures 11 are arranged in an array on the front surface. The LED chip is grown on the front surface. A plurality of aluminum nitride covering regions are also arranged in an array on the front surface and / or the back surface. The orthogonal projection area of ​​each aluminum nitride covering region on the back surface is greater than or equal to a preset area threshold and covers the orthogonal projection position of the vertex of the conical protrusion structure 11 on the back surface.

[0070] The sapphire substrate 10 includes a front surface and a back surface that are arranged opposite to each other and parallel to each other. Multiple conical protrusions 11 arranged in an array are etched on the front surface. Arrayed circular regions are formed on the back surface, where the orthographic projection area of ​​each circular region on the back surface is equal to a preset area threshold, and the orthographic projection position of the apex of each conical protrusion 11 on the back surface is located at the center point of the orthographic projection area of ​​the circular region on the back surface. Figure 3 As shown, the orthographic projection of the circular region onto the back surface can be a circle. The diameter of this orthographic projection region in the figure is k, and it satisfies the following equation: S = π·(k / 2). 2 Where S represents a preset area threshold. Each circular region is sputtered with aluminum nitride material, forming a second aluminum nitride coverage area 114.

[0071] The specific method for fabricating the second aluminum nitride covered area is as follows: photoresist is applied to the back surface to form a photoresist layer, and then array holes are drilled in the photoresist layer to expose the back surface and form an array of circular areas. After sputtering aluminum nitride material into each circular area, the photoresist covered area is removed, leaving the fourth aluminum nitride covered area.

[0072] It is understood that in this embodiment, an array of second aluminum nitride covering regions 114 are prepared on the back side of the sapphire substrate 10 according to the arrangement of the conical protrusions 11. The second aluminum nitride covering regions 114 change the laser energy distribution at the location where the laser passes through the conical protrusions 11, reduce the laser energy density at the tip of the conical protrusions 11, and reduce the destructive ability of the laser at the tip of the conical protrusions 11. This allows the laser to be lifted while avoiding crack formation that damages the electrical properties and morphological changes that reduce light extraction. The second aluminum nitride covering regions 114 can be selected as a circular pattern of 1.3-1.5 μm, and the film thickness of the second aluminum nitride covering regions 114 can be 5-10 nm. When lifting the LED wafer provided in this embodiment, the laser beam preferably irradiates the sapphire substrate 10 at a vertical angle.

[0073] like Figure 1 As shown, when a laser beam (indicated by the arrow in the figure) shines perpendicularly onto the sapphire substrate 10 from behind, the laser beam is refracted and deflected when it enters the gallium nitride buffer layer due to the refractive index difference between the sapphire and the gallium nitride buffer layer of the LED chip 20. Figure 1 As shown, when a beam of light illuminates the sapphire substrate 10 perpendicularly to its back surface, it will pass through the sidewall of the conical protrusion structure 11 at an angle α. i The incident sidewall is then refracted at an angle β i The laser then enters the gallium nitride buffer layer. Laser irradiation causes chemical decomposition of the gallium nitride buffer layer, generating nitrogen gas impact forces to peel off the LED chip 20 and the sapphire substrate 10. However, the refracted nitrogen gas impact forces are directed in different directions, easily generating tearing forces on the LED chip 20, leading to cracks in the chip and affecting its electrical properties and light extraction efficiency.

[0074] Thirdly, this application provides an LED wafer, including a sapphire substrate and an LED chip 20 grown on the sapphire substrate. The sapphire substrate includes a front surface and a back surface disposed opposite to each other. A plurality of conical protrusion structures 11 are arranged in an array on the front surface. The LED chip is grown on the front surface. A plurality of aluminum nitride covering regions are also arranged in an array on the front surface and / or the back surface. The orthogonal projection area of ​​each aluminum nitride covering region on the back surface is greater than or equal to a preset area threshold and covers the orthogonal projection position of the vertex of the conical protrusion structure 11 on the back surface.

[0075] The sapphire substrate 10 includes a front surface and a back surface arranged opposite each other. Multiple conical protrusions 11 arranged in an array are etched on the front surface, such as... Figure 4 As shown.

[0076] Multiple frustum-shaped protrusions 12 are etched on the back surface in an array. The area of ​​the top surface of the frustum-shaped protrusions 12 is greater than a preset area threshold. The vertex of the conical protrusion 11 is located at the center of the top surface in the orthographic projection of the top surface.

[0077] like Figure 5 As shown, the inclination angle i of the sidewall of the frustum-shaped protrusion 12 relative to the back surface satisfies the following equation:

[0078]

[0079] Wherein, θ1 represents the incident angle of the light beam passing through the sidewall of the frustum-shaped protrusion 12 when it illuminates the sapphire substrate 10 perpendicular to the back surface; φ1 represents the refraction angle of the light beam entering the sapphire substrate 10 through the sidewall of the frustum-shaped protrusion 12; α2 represents the incident angle of the light beam passing through the sidewall of the conical protrusion 11; β2 represents the refraction angle of the light beam entering the LED chip 20 through the sidewall of the conical protrusion 11; here, β2 is defined as e, where e represents the tilt angle of the sidewall of the conical protrusion 11 relative to the front surface; i represents the tilt angle of the sidewall of the frustum-shaped protrusion 12 relative to the back surface; n1 represents the refractive index of air; n2 represents the refractive index of the sapphire substrate 10; and n3 represents the refractive index of gallium nitride material in the LED chip 20.

[0080] The height h5 of the frustum-shaped protrusion 12 relative to the back surface satisfies the following formula:

[0081]

[0082] Where h5 represents the height of the frustum-shaped protrusion 12 relative to the back surface, h3 represents the height of the conical protrusion 11, and S represents the preset area threshold.

[0083] The diameter L1 of the top surface of the frustum-shaped protrusion 12 satisfies the following formula:

[0084]

[0085] Where h4 represents the thickness of the sapphire substrate 10, that is, the distance between the bottom of the frustum-shaped protrusion 12 and the bottom of the conical protrusion 11.

[0086] Aluminum nitride material is sputtered on each top surface, forming a third aluminum nitride coverage area 115.

[0087] It is understood that when peeling off the LED wafer provided in this embodiment, the laser beam preferably irradiates the sapphire substrate 10 at a vertical angle. When it irradiates the inclined surface of the frustum-shaped protrusion structure 12, the laser beam undergoes a first refraction and enters the sapphire substrate 10 at an angle φ1. When the beam irradiates the sidewall of the conical protrusion structure 11, it undergoes a second refraction and enters the epitaxial layer of the LED chip 20 at an angle β2. Since the refractive indices of air, the sapphire substrate 10, and the epitaxial layer gradually decrease, the frustum-shaped protrusion structure 12 can be designed with specific parameters so that the beam entering the LED chip 20 at an angle β2 exits vertically, no longer forming a component oriented towards the horizontal direction. This embodiment can avoid the tearing force generated on the LED chip 20 due to the different directions of nitrogen impact, which could lead to cracks in the chip.

[0088] Fourthly, this application provides an LED wafer, including a sapphire substrate and an LED chip 20 grown on the sapphire substrate. The sapphire substrate includes a front surface and a back surface disposed opposite to each other. A plurality of conical protrusion structures 11 are arranged in an array on the front surface. The LED chip is grown on the front surface. A plurality of aluminum nitride covering regions are also arranged in an array on the front surface and / or the back surface. The orthogonal projection area of ​​each aluminum nitride covering region on the back surface is greater than or equal to a preset area threshold and covers the orthogonal projection position of the vertex of the conical protrusion structure 11 on the back surface.

[0089] The sapphire substrate 10 includes a front surface and a back surface that are arranged opposite to each other and parallel to each other. Multiple conical protrusions 11 arranged in an array are etched on the front surface.

[0090] like Figure 6 As shown, an array of circular fourth aluminum nitride covering regions 116 are prepared on the back surface, such that the orthographic projection of the vertex of the conical protrusion structure 11 on the back surface is located at the center point of the corresponding fourth aluminum nitride covering region 116, and the area of ​​the fourth aluminum nitride covering region 116 is greater than a preset area threshold.

[0091] like Figure 7 As shown, the diameter L2 of the fourth aluminum nitride covered region 116 satisfies the following formula:

[0092]

[0093] Where S represents the preset area threshold, h3 represents the height of the conical protrusion structure 11, h4 represents the thickness of the sapphire substrate 10, i.e. the distance between the bottom of the frustum-shaped protrusion structure 12 and the bottom of the conical protrusion structure 11, α3 represents the incident angle of the light beam through the sidewall of the conical protrusion structure 11, β3 represents the refraction angle of the light beam through the sidewall of the conical protrusion structure 11 into the LED chip 20, and here β3 is defined as e, where e represents the tilt angle of the sidewall of the conical protrusion structure 11 relative to the front surface, n2 represents the refractive index of the sapphire substrate 10, and n3 represents the refractive index of gallium nitride material in the LED chip 20.

[0094] like Figure 6 and Figure 7 As shown, a first semi-circular transparent layer 117 formed of a first light-transmitting material is prepared on the back surface. The first light-transmitting material transmits a first-band light beam and reflects other-band light beams. A second semi-circular transparent layer 118 formed of a second light-transmitting material is prepared on the back surface. The second light-transmitting material transmits a second-band light beam and reflects other-band light beams. The first semi-circular transparent layer 117 and the second semi-circular transparent layer 118 are spliced ​​together to form a complete ring around the fourth aluminum nitride covered area 116. The inner diameter of the complete ring is the diameter L2 of the fourth aluminum nitride covered area 116.

[0095] like Figure 7 As shown, the width W of the complete annulus satisfies the following formula:

[0096]

[0097] A third reflective material is coated on the fourth aluminum nitride covered area 116, forming a third reflective material coating layer 119. The third reflective material is used to reflect the first band beam and the second band beam and transmit other band beams. The third reflective material may include a first reflective material and a second reflective material stacked sequentially, wherein the first reflective material is used to reflect the first band beam and transmit other band beams, and the second reflective material is used to reflect the second band beam and transmit other band beams.

[0098] Fifthly, this application provides an LED wafer processing method, which includes steps S1 to S4, wherein S1, S2, etc. are merely step identifiers, and the execution order of the method does not necessarily follow the numerical order from smallest to largest. For example, step S2 can be executed first and then step S1 can be executed. This application does not impose any restrictions.

[0099] S1, Prepare an LED wafer as described in any one of the first to fourth aspects.

[0100] S2, attach the side of the LED chip in the LED wafer away from the sapphire substrate to a temporary substrate.

[0101] S3, providing at least one laser beam to irradiate the sapphire substrate, peeling the LED chip on the sapphire substrate onto a temporary substrate, and performing a preset treatment on the light-emitting surface of the LED chip on the temporary substrate.

[0102] S4. An LED display unit is fabricated using at least three LED chips, and then the LED display unit is transferred to a display backplane for encapsulation to obtain an LED display; or, the LED chips on the temporary substrate are directly transferred to the display backplane for encapsulation to obtain an LED display.

[0103] In an optional embodiment, when an LED wafer as described in any one of the first to third aspects is fabricated, the step of providing at least one laser beam to irradiate the sapphire substrate includes: providing a laser beam to irradiate the sapphire substrate at a vertical angle.

[0104] In an optional embodiment, when an LED wafer as described in any of the fourth aspects is fabricated, such as Figure 6 As shown, at least one laser beam is provided to irradiate the sapphire substrate 10, including:

[0105] A first laser beam of the first wavelength (shown by the red arrow in the figure) is provided to irradiate the sapphire substrate 10 at a first angle, and the first laser beam is emitted in the horizontal direction toward the first direction;

[0106] A second laser beam of the second band (shown by the blue arrow in the figure) is provided to irradiate the sapphire substrate 10 at a second angle. The second laser beam is emitted in a second direction in the horizontal direction, which is opposite to the first direction.

[0107] A third laser beam of the third band (shown by the black arrow in the figure) is provided to irradiate the sapphire substrate 10 at a vertical angle.

[0108] Where the first angle is equal to the second angle, and satisfies the following equation:

[0109] θ2 represents the angle values ​​of the first angle and the second angle.

[0110] It is understood that this embodiment provides three different wavelengths of laser beams to irradiate the sapphire substrate 10. The third laser beam of the third wavelength irradiates the sapphire substrate 10 at a vertical angle. After passing through the aforementioned third reflective material coating layer, it is weakened by the fourth aluminum nitride covering area 116 before entering the top of the conical protrusion structure 11. The fourth aluminum nitride covering area 116 changes the laser energy distribution of the third laser beam passing through the top position, reducing the laser energy density at the top of the conical protrusion structure 11 and reducing the destructive ability of the laser on the top position of the conical protrusion structure 11. The first laser beam of the first wavelength and the second laser beam of the second wavelength irradiate the sapphire substrate 10 in different directions at an angle θ2. Due to the coating of various light-transmitting and reflective materials, the first laser beam and the second laser beam can only enter the sapphire substrate 10 from the coating areas of the first light-transmitting material and the second light-transmitting material, respectively. After being refracted twice by the back surface and the sidewall of the conical protrusion structure 11, they enter the LED chip 20 in a vertical direction and no longer form a component in the horizontal direction. Therefore, this embodiment can not only reduce the laser energy density at the top of the conical protrusion 11 and reduce the destructive power of the laser on the top of the conical protrusion 11, but also avoid the tearing force generated on the LED chip 20 due to the different directions of nitrogen impact force, which would cause cracks in the chip.

[0111] like Figure 8 As shown, the side of the LED chip 20 facing away from the sapphire substrate 10 in the LED wafer is attached to a temporary substrate 40. At least one laser beam is provided to irradiate the sapphire substrate 10 to peel off the LED chip 20 and the sapphire substrate 10. The contact layer between the LED chip 20 and the sapphire substrate 10 is typically a gallium nitride buffer layer. Under laser irradiation, the gallium nitride material decomposes into nitrogen gas and metallic gallium. Therefore, after laser peeling, some metallic gallium remains on the surface of the LED chip 20, affecting the light emission effect. Therefore, the light-emitting surface of the LED chip 20 on the temporary substrate needs to be pre-treated.

[0112] In optional embodiments of this application, the preset processing includes at least one of the following.

[0113] 1. A light-transmitting additional layer is fabricated on the light-emitting surface of the LED chip. The refractive index of the light-transmitting additional layer is lower than that of gallium nitride (GaN) but higher than a preset refractive index value. It is understood that the high refractive index of GaN in LED chips easily leads to total internal reflection at the interface, reducing light extraction efficiency. By fabricating a light-transmitting additional layer with a refractive index lower than that of GaN but higher than the preset value on the light-emitting surface of the LED chip, total internal reflection can be effectively reduced, allowing more light to escape smoothly from the chip. This light-transmitting additional layer can significantly improve the light extraction efficiency of the LED chip, increase luminous brightness, and maintain good light transmittance without affecting the overall performance of the LED chip. The light-transmitting additional layer can be made of materials such as gallium oxide, argon oxide (HfO), aluminum oxide (Al₂O₃), zinc oxide (ZnO), aluminum nitride (AlN), or silicon nitride (SiN).

[0114] 2. Accelerated oxidation treatment is applied to the light-emitting surface of the LED chip on the temporary substrate to form a gallium oxide layer. It is understood that residual metallic gallium may remain during laser stripping, affecting LED chip performance. By accelerating oxidation treatment of the light-emitting surface of the LED chip, the residual metallic gallium can be converted into gallium oxide. Furthermore, gallium oxide has a lower refractive index than gallium nitride, which helps improve light extraction efficiency. This treatment not only removes harmful residues but also further optimizes the optical performance of the LED chip and improves luminous efficiency by forming a low-refractive-index gallium oxide layer.

[0115] 3. A coating treatment is applied to the light-emitting surface of the LED chip on the temporary substrate, forming a coating layer on the light-emitting surface of the LED chip. It can be understood that coating materials such as gallium oxide and aluminum oxide can penetrate into tiny cracks, effectively repairing them through physical filling and chemical bonding, thus enhancing the integrity of the chip structure. This process not only reduces light scattering and absorption at the cracks but also improves the luminous efficiency and reliability of the LED chip, extending its lifespan. Preferably, the refractive index of the coating layer is lower than that of the gallium oxide layer but higher than a preset refractive index value. It can be understood that depositing a transparent film layer with a refractive index lower than gallium oxide but higher than the preset value on the light-emitting surface of the LED chip creates an interface structure with a gradually decreasing refractive index, which helps light escape from the chip more smoothly and reduces interface reflection loss. The coating treatment can further improve the light extraction efficiency of the LED chip, enhance the luminous effect, and at the same time, the coating layer also plays a certain protective role, extending the lifespan of the LED chip. The coating layer can be gallium oxide, yttrium oxide (HfO), aluminum oxide (Al₂O₃), zinc oxide (ZnO), aluminum nitride (AlN), silicon nitride (SiN), silicon oxide, etc.

[0116] In an optional embodiment of this application, the refractive index of the material layer in the LED display that is in contact with the light-emitting surface of the LED chip is less than a preset refractive index value. It can be understood that in this embodiment, the refractive index of the material layer in the LED display that is in direct contact with the light-emitting surface of the LED chip is designed to be less than the preset refractive index value. This design is based on optical principles; by reducing the refractive index of the contact layer, the reflection of light at the interface between the LED chip and the contact layer can be effectively reduced, promoting smoother light escape from the chip.

[0117] The terms "first," "second," "first," or "second" as used in the various embodiments of this disclosure may modify various components regardless of their order and / or importance, but these terms do not limit the corresponding components. The above terms are configured only for the purpose of distinguishing an element from other elements. For example, "first user equipment" and "second user equipment" refer to different user equipments, although both are user equipment. For example, without departing from the scope of this disclosure, a first element may be referred to as a second element, and similarly, a second element may be referred to as a first element.

[0118] When a component (e.g., a first component) is referred to as being "(operably or communicatively) coupled" or "(operably or communicatively) coupled to" or "connected to" another component (e.g., a second component), it should be understood that the first component is directly connected to the second component or that the first component is indirectly connected to the second component via yet another component (e.g., a third component). Conversely, it can be understood that when a component (e.g., a first component) is referred to as being "directly connected" or "directly coupled" to another component (the second component), no component (e.g., a third component) is inserted between the two.

[0119] It should be noted that, in this document, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes that element. Furthermore, components, features, and elements with the same names in different embodiments of this application may have the same meaning or different meanings, the specific meaning of which must be determined by its interpretation in that specific embodiment or further in conjunction with the context of that specific embodiment.

[0120] The above description is merely an optional embodiment of this application and an explanation of the technical principles employed. Those skilled in the art should understand that the scope of the invention involved in this application is not limited to technical solutions formed by specific combinations of the above-described technical features, but should also cover other technical solutions formed by arbitrary combinations of the above-described technical features or their equivalents without departing from the above-described inventive concept. For example, technical solutions formed by substituting the above-described features with (but not limited to) technical features with similar functions disclosed in this application.

[0121] Depending on the context, the words “if” or “suppose” as used here can be interpreted as “when” or “in response to determination” or “in response to detection.” Similarly, depending on the context, the phrases “if determination” or “if detection (of the stated condition or event)” can be interpreted as “when determination” or “in response to determination” or “when detection (of the stated condition or event)” or “in response to detection (of the stated condition or event).”

[0122] The above description is merely an optional embodiment of this application and an explanation of the technical principles employed. Those skilled in the art should understand that the scope of the invention involved in this application is not limited to technical solutions formed by specific combinations of the above-described technical features, but should also cover other technical solutions formed by arbitrary combinations of the above-described technical features or their equivalents without departing from the above-described inventive concept. For example, technical solutions formed by substituting the above-described features with (but not limited to) technical features with similar functions disclosed in this application.

[0123] The above description is merely an optional embodiment of this application and is not intended to limit this application. Various modifications and variations can be made to this application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. An LED wafer, characterized in that, include: A sapphire substrate and an LED chip grown on the sapphire substrate. The sapphire substrate includes a front surface and a back surface disposed opposite to each other. A plurality of conical protrusions are arranged in an array on the front surface. The LED chip is grown on the front surface. A plurality of aluminum nitride covering regions are also arranged in an array on the front surface and / or the back surface. The orthogonal projection area of ​​each aluminum nitride covering region on the back surface is greater than or equal to a preset area threshold and covers the orthogonal projection position of the vertex of the conical protrusion on the back surface.

2. The LED wafer according to claim 1, characterized in that, The sapphire substrate includes a front surface and a back surface that are arranged opposite to each other and parallel to each other, and a plurality of conical protrusions are etched on the front surface. The top region of each of the conical protrusions is projected onto the back surface in a manner equal to a preset area threshold. Each of the top regions is sputtered with aluminum nitride material to form an aluminum nitride-covered area.

3. The LED wafer according to claim 1, characterized in that, The sapphire substrate includes a front surface and a back surface that are arranged opposite to each other and parallel to each other, and a plurality of conical protrusions are etched on the front surface. The back surface is formed with an array of circular regions, and the orthographic projection area of ​​each circular region on the back surface is equal to a preset area threshold, and the orthographic projection position of the vertex of the conical protrusion structure on the back surface is located at the center point of the orthographic projection area of ​​the circular region on the back surface. Each of the circular regions is sputtered with aluminum nitride material to form an aluminum nitride-covered area.

4. The LED wafer according to claim 1, characterized in that, The sapphire substrate includes a front surface and a back surface arranged opposite to each other, and multiple conical protrusions are etched in an array on the front surface; Multiple frustum-shaped protrusions are etched on the back surface in an array. The area of ​​the top surface of the frustum-shaped protrusions is greater than a preset area threshold. The vertex of the conical protrusion is located at the center of the top surface in the orthographic projection of the top surface. The inclination angle i of the sidewall of the frustum-shaped protrusion relative to the back surface satisfies the following formula: Wherein, θ1 represents the incident angle of the light beam passing through the sidewall of the frustum-shaped protrusion when it irradiates the sapphire substrate perpendicular to the back surface; φ1 represents the refraction angle of the light beam entering the sapphire substrate through the sidewall of the frustum-shaped protrusion; α2 represents the incident angle of the light beam passing through the sidewall of the conical protrusion; β2 represents the refraction angle of the light beam entering the LED chip through the sidewall of the conical protrusion; here, β2 is defined as e, where e represents the tilt angle of the sidewall of the conical protrusion relative to the front surface; i represents the tilt angle of the sidewall of the frustum-shaped protrusion relative to the back surface; n1 represents the refractive index of air; n2 represents the refractive index of the sapphire substrate; and n3 represents the refractive index of gallium nitride, the material in the LED chip. The height h5 of the frustum-shaped protrusion relative to the back surface satisfies the following formula: Wherein, h5 represents the height of the frustum-shaped protrusion relative to the back surface, h3 represents the height of the conical protrusion, and S represents a preset area threshold. The diameter L1 of the top surface of the frustum-shaped protrusion satisfies the following formula: Where h4 represents the thickness of the sapphire substrate, that is, the distance between the bottom of the frustum-shaped protrusion and the bottom of the conical protrusion; Each of the top surfaces is sputtered with aluminum nitride material to form an aluminum nitride-covered area.

5. The LED wafer according to claim 1, characterized in that, The sapphire substrate includes a front surface and a back surface that are arranged opposite to each other and parallel to each other, and a plurality of conical protrusions are etched on the front surface. The back surface is prepared with an array of circular aluminum nitride covering areas, such that the vertex of the conical protrusion structure is located at the center point of the corresponding aluminum nitride covering area on the back surface, and the area of ​​the aluminum nitride covering area is greater than a preset area threshold. The diameter L2 of the aluminum nitride-covered area satisfies the following formula: Where S represents a preset area threshold, h3 represents the height of the conical protrusion structure, h4 represents the thickness of the sapphire substrate, i.e., the distance between the bottom of the frustum-shaped protrusion structure and the bottom of the conical protrusion structure, α3 represents the incident angle of the light beam through the sidewall of the conical protrusion structure, β3 represents the refraction angle of the light beam through the sidewall of the conical protrusion structure into the LED chip, and here β3 is defined as e, where e represents the tilt angle of the sidewall of the conical protrusion structure relative to the front surface, n2 represents the refractive index of the sapphire substrate, and n3 represents the refractive index of gallium nitride material in the LED chip; A first semi-circular transparent layer formed of a first light-transmitting material is prepared on the back surface. The first light-transmitting material transmits a first wavelength beam and reflects other wavelength beams. A second semi-circular transparent layer formed of a second light-transmitting material is prepared on the back surface. The second light-transmitting material transmits a second wavelength beam and reflects other wavelength beams. The first semi-circular transparent layer and the second semi-circular transparent layer are spliced ​​together to form a complete ring around the aluminum nitride covered area. The inner diameter of the complete ring is the diameter L2 of the aluminum nitride covered area. The width W of the complete circular ring satisfies the following formula: The aluminum nitride-covered area is coated with a third reflective material, which is used to reflect the first band beam and the second band beam and transmit other band beams.

6. A method for processing LED wafers, characterized in that, Includes the following steps: S1, preparing the LED wafer as described in any one of claims 1-5; S2, attach the side of the LED chip in the LED wafer away from the sapphire substrate to a temporary substrate; S3, at least one laser beam is provided to irradiate the sapphire substrate, the LED chip on the sapphire substrate is peeled off onto a temporary substrate, and the light-emitting surface of the LED chip on the temporary substrate is pre-processed; S4, using at least three of the LED chips to fabricate an LED display unit, and then transferring the LED display unit to a display backplane for encapsulation to obtain an LED display; or, directly transferring the LED chips on the temporary substrate to the display backplane for encapsulation to obtain an LED display.

7. The LED wafer processing method according to claim 6, characterized in that, When an LED wafer as described in any one of claims 1-4 is fabricated, the step of providing at least one laser beam to irradiate the sapphire substrate includes: providing a laser beam to irradiate the sapphire substrate at a vertical angle.

8. The LED wafer processing method according to claim 6, characterized in that, When the LED wafer as described in claim 5 is fabricated, the step of providing at least one laser beam to irradiate the sapphire substrate includes: A first laser beam of a first wavelength is provided to irradiate the sapphire substrate at a first angle, the first laser beam being emitted in a horizontal direction toward a first direction; A second laser beam of a second wavelength is provided to irradiate the sapphire substrate at a second angle. The second laser beam is emitted in a horizontal direction toward a second direction, which is opposite to the first direction. A third laser beam of the third band is provided to irradiate the sapphire substrate at a vertical angle.

9. The LED wafer processing method according to claim 8, characterized in that, The first angle is equal to the second angle, and satisfies the following formula: Wherein, θ2 represents the angle values ​​of the first angle and the second angle.

10. The LED wafer and processing method according to claim 6, characterized in that, The preset processing includes at least one of the following: A light-transmitting additional layer is prepared on the light-emitting surface of the LED chip. The refractive index of the light-transmitting additional layer is less than that of gallium nitride and greater than a preset refractive index value. The light-emitting surface of the LED chip on the temporary substrate is subjected to accelerated oxidation treatment, so that a gallium oxide layer is formed on the light-emitting surface of the LED chip; The light-emitting surface of the LED chip on the temporary substrate is coated to form an aluminum oxide layer on the light-emitting surface of the LED chip.

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