Double-layer patterned sapphire substrate, preparation method and LED epitaxial wafer

Abstract

The embodiment of the application discloses a double-layer patterned sapphire substrate, a preparation method and an LED epitaxial wafer. The preparation method comprises the following steps: providing a first sapphire substrate and a second sapphire substrate; forming a convex microstructure on a first surface of the first sapphire substrate and a concave microstructure on a first surface of the second sapphire substrate; performing O2 plasma surface activation treatment on second surfaces of the first sapphire substrate and the second sapphire substrate; cleaning the second surfaces of the first sapphire substrate and the second sapphire substrate by using ammonia water to form Al-OH chemical bonds; and mutually adhering the second surfaces of the first sapphire substrate and the second sapphire substrate and performing vacuum heat treatment, so that the second surfaces of the first sapphire substrate and the second sapphire substrate are mutually bonded. By bonding the sapphire substrates with different patterns, the reflectivity of light is effectively improved, the light extraction efficiency is maximized, and the heat dissipation problem caused by the substrate thickness is reduced.

Description

TECHNICAL FIELD

[0001] Embodiments of the present application relate to the technical field of semiconductor technology, and particularly relate to a double-layer patterned sapphire substrate, a preparation method and an LED epitaxial wafer. BACKGROUND

[0002] Since the 20th century, various countries have taken low-carbon economy or resource-saving development as an important direction for future sustainable development, which is based on low energy consumption, low emission and low pollution. In the lighting field with huge power demand, Light Emitting Diode (LED) plays a crucial role. GaN-based LED chips are widely used in industry and general lighting due to their high electro-optical conversion efficiency, energy saving, environmental protection, long service life and small size.

[0003] Sapphire material is currently the mainstream GaN-based LED chip epitaxial material due to its moderate price, good chemical stability, high mechanical strength and good light transmittance. However, the large lattice mismatch and thermal expansion coefficient between sapphire and GaN greatly affect the light-emitting efficiency and service life of LED. To solve the defects of sapphire, Patterned Sapphire Substrate (PSS) technology is proposed. PSS technology is to process the surface of sapphire through microprocessing to obtain a periodic pattern microstructure. The patterned interface can change the light incidence angle at the GaN-sapphire interface, thereby suppressing internal total reflection in LED and improving the light extraction efficiency of GaN-based LED devices. In addition, due to the existence of patterned slope, the growth mode of GaN thin film epitaxied on the PSS substrate changes, the dislocation density of the epitaxial layer is reduced, and the internal quantum efficiency of the active layer MQW is significantly improved. However, the improvement of the existing patterned substrate is mostly the change of the pattern, from the initial groove shape to various patterns. Changing the shape of the pattern microstructure has limited effect on the light extraction and epitaxial quality of the entire LED device, resulting in low light extraction efficiency of the LED. SUMMARY

[0004] The present application provides a double-layer patterned sapphire substrate, a preparation method and an LED epitaxial wafer to increase the reflectivity of light and obtain greater light extraction efficiency.

[0005] In a first aspect, embodiments of the present application provide a preparation method of a double-layer patterned sapphire substrate, comprising:

[0006] providing a first sapphire substrate and a second sapphire substrate, the first sapphire substrate and the second sapphire substrate each comprising a first surface and a second surface facing away from each other;

[0007] forming a convex microstructure on the first surface of the first sapphire substrate and a concave microstructure on the first surface of the second sapphire substrate;

[0008] performing O2 plasma surface activation treatment on the second surface of the first sapphire substrate and the second sapphire substrate;

[0009] cleaning the second surface of the first sapphire substrate and the second sapphire substrate with ammonia water to form Al-OH chemical bonds;

[0010] bonding the second surfaces of the first sapphire substrate and the second sapphire substrate to each other and performing vacuum heat treatment, so that the second surfaces of the first sapphire substrate and the second sapphire substrate are bonded to each other.

[0011] Optionally, before forming a convex microstructure on the first surface of the first sapphire substrate and a concave microstructure on the first surface of the second sapphire substrate, the method further comprises:

[0012] cleaning and drying the first surface of the first sapphire substrate and the second sapphire substrate;

[0013] Optionally, before performing O2 plasma surface activation treatment on the second surface of the first sapphire substrate and the second sapphire substrate, the method further comprises:

[0014] cleaning and drying the second surface of the first sapphire substrate and the second sapphire substrate.

[0015] Optionally, cleaning and drying the first surface of the first sapphire substrate and the second sapphire substrate comprises:

[0016] immersing the first sapphire substrate and the second sapphire substrate in a mixed solution of H2SiO4 and H2O2 for acid pickling for 20-30 min;

[0017] taking out the first sapphire substrate and the second sapphire substrate and performing spin-drying or drying treatment.

[0018] Optionally, cleaning and drying the second surface of the first sapphire substrate and the second sapphire substrate comprises:

[0019] cleaning the first sapphire substrate and the second sapphire substrate with RCA solution mixed with ammonia water and H2O2 for 10-20 min;

[0020] rinsing the first sapphire substrate and the second sapphire substrate with 0.025-0.05% HF solution;

[0021] The first sapphire substrate and the second sapphire substrate are placed in an air environment at 200-300°C for drying treatment.

[0022] Optionally, after forming the convex microstructure on the first surface of the first sapphire substrate and forming the concave microstructure on the first surface of the second sapphire substrate, the method further comprises:

[0023] The second surfaces of the first sapphire substrate and the second sapphire substrate are subjected to thinning treatment.

[0024] Optionally, the concentration of the ammonia water is 20-30%.

[0025] Optionally, forming the convex microstructure on the first surface of the first sapphire substrate and forming the concave microstructure on the first surface of the second sapphire substrate comprises:

[0026] forming a first dielectric layer on the first surface of the first sapphire substrate, and patterning the first dielectric layer or the first dielectric layer and the first sapphire substrate to form the convex microstructure;

[0027] patterning the first surface of the second sapphire substrate to form the concave microstructure;

[0028] forming a second dielectric layer on the first surface of the second sapphire substrate, the second dielectric layer filling the concave microstructure.

[0029] In a second aspect, an embodiment of the present application provides a double-layer patterned sapphire substrate prepared by the method of any one of the first aspect.

[0030] The patterned sapphire substrate comprises a first sapphire substrate and a second sapphire substrate, and the first sapphire substrate and the second sapphire substrate each comprise mutually facing first and second surfaces;

[0031] The first surface of the first sapphire substrate is formed with a convex microstructure, the first surface of the second sapphire substrate is formed with a concave microstructure, and the second surfaces of the first sapphire substrate and the second sapphire substrate are mutually bonded.

[0032] Optionally, the convex microstructure comprises a first dielectric layer and a sapphire layer, and the first dielectric layer is located on a side of the sapphire layer facing away from the second sapphire substrate.

[0033] The second sapphire substrate further comprises a second dielectric layer on the side of the second sapphire substrate facing away from the first sapphire substrate, the second dielectric layer covering the second surface of the second sapphire substrate and filling the pit microstructure.

[0034] Optionally, the shape of the convex microstructure comprises at least one of a cone, a table, a spheroid, a cube, or the shape of the convex microstructure comprises a quasi-cone or a quasi-table with a side wall curvature.

[0035] The shape of the pit microstructure comprises at least one of a cone, a table, a spheroid, a cube, or the shape of the pit microstructure comprises a quasi-cone or a quasi-table with a side wall curvature.

[0036] Optionally, the material of the first dielectric layer comprises at least one of SiO2, AlN, Si3N4, and the material of the second dielectric layer comprises at least one of SiC and AlN.

[0037] In a third aspect, an LED epitaxial wafer is provided, comprising the double-layer patterned sapphire substrate according to any one of the second aspect, and further comprising an epitaxial layer on the double-layer patterned sapphire substrate.

[0038] The double-layer patterned sapphire substrate is prepared by the method provided in the embodiments of the present application, which comprises the following steps: providing a first sapphire substrate and a second sapphire substrate, wherein the first sapphire substrate and the second sapphire substrate each comprise a first surface and a second surface facing away from each other; forming a convex microstructure on the first surface of the first sapphire substrate and a pit microstructure on the first surface of the second sapphire substrate; performing O2 plasma surface activation treatment on the second surface of the first sapphire substrate and the second surface of the second sapphire substrate; cleaning the second surface of the first sapphire substrate and the second surface of the second sapphire substrate by using ammonia water to form Al-OH chemical bonds; and bonding the second surface of the first sapphire substrate and the second surface of the second sapphire substrate to each other and performing vacuum heat treatment, so that the second surface of the first sapphire substrate and the second surface of the second sapphire substrate are bonded to each other. The embodiments of the present application solve the problem that the existing patterned substrate is limited in improving the light extraction efficiency of an LED. The double-layer sapphire patterned substrate can be realized, the difference in structural characteristics such as the side slope of the two-layer patterned microstructure is utilized to increase the reflection of light, improve the reflection efficiency, and improve the light regulation effect, thereby further improving the light extraction efficiency of the LED chip. BRIEF DESCRIPTION OF DRAWINGS

[0039] Figure 1 A flowchart of a method for preparing a double-layer patterned sapphire substrate is provided in the embodiments of the present application;

[0040] Figure 2A structural flowchart of a double-layer patterned sapphire substrate preparation method provided by an embodiment of the present application is shown in FIG. 1.

[0041] Figure 3 A flowchart of another double-layer patterned sapphire substrate preparation method provided by an embodiment of the present application is shown in FIG. 2.

[0042] Figure 4 A structural diagram of a double-layer patterned sapphire substrate provided by an embodiment of the present application is shown in FIG. 3.

[0043] Figure 5 A structural diagram of an LED epitaxial wafer provided by an embodiment of the present application is shown in FIG. 4. DETAILED DESCRIPTION

[0044] The present application will be further described below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are intended to be merely illustrative of the present application and not in limitation thereof. It should also be noted that, for the purpose of description, only the parts related to the present application are shown in the accompanying drawings rather than all the parts.

[0045] Figure 1 A flowchart of a double-layer patterned sapphire substrate preparation method provided by an embodiment of the present application is shown in FIG. 1. Figure 1 As shown in FIG. 1, a double-layer patterned sapphire substrate preparation method comprises the following steps:

[0046] S101, providing a first sapphire substrate and a second sapphire substrate, both of which comprise a first surface and a second surface facing away from each other.

[0047] S102, forming a convex microstructure on the first surface of the first sapphire substrate and a concave microstructure on the first surface of the second sapphire substrate.

[0048] In the present application, the convex microstructure formed on the first surface of the first sapphire substrate and the concave microstructure formed on the first surface of the second sapphire substrate are shown in FIG. 1. Figure 2 A structural flowchart of a double-layer patterned sapphire substrate provided by an embodiment of the present application is shown in FIG. 1. Figure 1 and Figure 2The first dielectric layer 111 is deposited on the first surface of the first sapphire substrate 11 by MOCVD or PVD, and then the first photoresist mask layer 112 is obtained by the processes of gluing, exposing, developing and positive developing. The first sapphire substrate 11 with the first photoresist mask layer 112 is etched by dry etching or wet etching to obtain the convex microstructure 113 with a bottom diameter of 2.5-3.5 um and a height of 1.0-2.0 um. Optionally, in this embodiment, the etching process of the first dielectric layer 111 is over-etching, that is, after the first dielectric layer 111 is completely etched, the exposed first sapphire substrate 11 is also etched to a certain extent, and the etching depth of the sapphire is 100-300 nm. At this time, the convex microstructure 113 includes a dielectric layer and a sapphire layer, and the dielectric layer is located on the side of the sapphire layer away from the first sapphire substrate. The convex microstructure 113 is formed by using the first dielectric layer 111, and the difference in refractive index between the first dielectric layer 111 and the sapphire substrate can form a reflection interface. At the same time, the convex microstructure 113 formed by the dielectric material can also form a reflection interface with the epitaxial layer. In addition, since the convex microstructure 113 can be made of a dielectric material with a relatively low refractive index, when light is incident on the convex microstructure 113 from the epitaxial layer, it is essentially a propagation path from a light-dense medium to a light-lean medium. The dielectric material with a relatively low refractive index can increase the total reflection angle of the interface, that is, the probability of total reflection at the interface, so that more light is reflected at the interface. In addition, due to the structural features such as the side wall of the convex microstructure 113, the slope of the interface is also changed, further increasing the probability of light reflection.

[0049] The first surface of the second sapphire substrate 12 is coated with photoresist, exposed, and developed by positive photoresist negative development or negative photoresist positive development, or a mask prepared by a convex microstructure different from the first sapphire substrate 11, to obtain a second photoresist mask layer 121 complementary to the first photoresist mask layer 112. The second sapphire substrate 12 with the second photoresist mask layer 121 is etched by dry etching or wet etching, to obtain a concave microstructure 123 with a bottom diameter of 2.5-3.5 um and a depth of 1.0-2.0 um. Optionally, a second dielectric layer 122 can be deposited on the concave microstructure 123 by MOCVD or PVD in the embodiment, that is, the second dielectric layer 122 covers the second surface of the second sapphire substrate 12 and fills the concave microstructure 123. At this time, the refractive index difference between the second dielectric layer 122 and the sapphire substrate can be used to form a reflection interface for the concave microstructure 123. Moreover, the second dielectric layer 122 can form an interface with the external air, and when the refractive index of the second dielectric layer 122 is higher than that of the sapphire substrate, the refractive index difference between the two sides of the interface formed by the second dielectric layer 122 and the air layer increases, and the light transmitted by the epitaxial layer propagates from the optically dense to the optically sparse at the interface, thereby increasing the angle of total reflection and making it easier to occur total reflection, thereby increasing the reflection probability.

[0050] In addition, the convex microstructure 113 formed on the first surface of the first sapphire substrate 11 and the concave microstructure 123 formed on the first surface of the second sapphire substrate 12 are staggered, which can maximize the light reflection interface and improve the light reflection ability of the patterned substrate.

[0051] S103, performing O2 plasma surface activation treatment on the second surfaces of the first sapphire substrate and the second sapphire substrate.

[0052] The step is essentially a first pretreatment process for the first sapphire substrate and the second sapphire substrate before bonding. O2 plasma surface activation treatment can cause various chemical or physical changes on the second surfaces of the first sapphire substrate and the second sapphire substrate, thereby improving the surface energy. O2 plasma surface activation treatment is performed on the second surfaces of the first sapphire substrate and the second sapphire substrate for 30-300 s, so that the surface state can meet the process requirements of subsequent bonding.

[0053] S104, cleaning the second surfaces of the first sapphire substrate and the second sapphire substrate with ammonia water to form Al-OH chemical bonds.

[0054] This step is the process of the second pretreatment of the first sapphire substrate and the second sapphire substrate before bonding. By treating the sapphire with ammonia water, active chemical bonds for bonding can be formed on the surface of the sapphire, thereby facilitating the close bonding of the two sapphire substrates. Alternatively, the concentration of ammonia water in this step can be selected as 20-30%.

[0055] S105, the second surfaces of the first sapphire substrate and the second sapphire substrate are adhered to each other and vacuum heat treated to bond the second surfaces of the first sapphire substrate and the second sapphire substrate to each other.

[0056] Wherein, continuing to refer to Figure 2 The second surfaces of the processed first sapphire substrate 11 and the second sapphire substrate 12 are adhered to each other and placed in a vacuum cavity for vacuum heat treatment. The heat treatment condition is 400-800℃ for 1-6 hours. The Al-OH chemical bonds of the second surfaces of the first sapphire substrate and the second sapphire substrate undergo a chemical reaction of Al-OH+OH-Al=Al-O-Al+H2O, thereby realizing the mutual bonding of the second surfaces of the first sapphire substrate and the second sapphire substrate and forming a double-layer patterned sapphire substrate.

[0057] In this embodiment, by forming a convex microstructure on the first surface of the first sapphire substrate and a concave microstructure on the first surface of the second sapphire substrate, and through plasma surface activation of the second surfaces of the first sapphire substrate and the second sapphire substrate, the second surfaces of the first sapphire substrate and the second sapphire substrate are realized to be plasma activated and bonded to each other, thereby obtaining a double-layer patterned sapphire substrate, and the double-layer sapphire substrate is integrated. On the basis of the double-layer patterning, by using the difference in the structure characteristics such as the side slope of the two-layer patterned microstructure, the reflection of light is increased, the reflection efficiency is improved, the regulation effect on light is improved, and the light extraction efficiency of the LED chip is further improved.

[0058] Specifically, Figure 3 Another flowchart of the preparation method of the double-layer patterned sapphire substrate provided by the embodiment of the present application is shown in Figure 3 The preparation method of the double-layer patterned sapphire substrate includes:

[0059] S301, providing a first sapphire substrate and a second sapphire substrate, both the first sapphire substrate and the second sapphire substrate include first surfaces and second surfaces facing away from each other.

[0060] S302, cleaning and drying the first surfaces of the first sapphire substrate and the second sapphire substrate.

[0061] S303, a raised microstructure is formed on the first surface of the first sapphire substrate, and a pit microstructure is formed on the first surface of the second sapphire substrate.

[0062] Optionally, the shape of the protruding microstructure includes at least one of a cone, a frustum, a spherical cap, and a cube; or, the shape of the protruding microstructure includes a cone-like or frustum-like structure with curved sidewalls. The shape of the pit microstructure includes at least one of a cone, a frustum, a spherical cap, and a cube; or, the shape of the pit microstructure includes a cone-like or frustum-like structure with curved sidewalls.

[0063] Among them, such as Figure 2 As shown, exemplarily, the protruding microstructure 113 is shaped like a cone, and the pit microstructure 123 is shaped like a spherical cap. In other embodiments of the present invention, the actual etching rate can be changed by adjusting the dry or wet etching process parameters and the environment, so that the formed cone or truncated structure has a certain sidewall curvature, that is, a cone-like or truncated structure is formed.

[0064] S304. The second surfaces of both the first and second sapphire substrates are cleaned and dried.

[0065] S305. The second surfaces of both the first and second sapphire substrates are subjected to O2 plasma surface activation treatment.

[0066] S306. The second surfaces of both the first and second sapphire substrates are cleaned with ammonia water to form Al-OH chemical bonds.

[0067] S307, The second surfaces of the first sapphire substrate and the second sapphire substrate are thinned.

[0068] It is understandable that the main purpose of adding the thinning step S307 is to relatively increase the thickness of the first and second sapphire substrates when providing them in step S301. This increases the rigidity of the first and second sapphire substrates, preventing chip cracking caused by excessively thin substrates when forming microstructures, thus ensuring the quality of the patterned substrates. Specifically, the thickness of the first and second sapphire substrates after thinning is 100-200 μm. While utilizing plasma-activated bonding to integrate the two patterned substrates, this ensures a relatively thin overall substrate thickness, avoiding the increased processing and heat dissipation difficulties caused by excessively thick substrates, which is beneficial for LED chip processing and heat dissipation.

[0069] S308. The second surfaces of the first sapphire substrate and the second sapphire substrate are bonded together and subjected to vacuum heat treatment to bond the second surfaces of the first sapphire substrate and the second sapphire substrate together.

[0070] The first surface and the second surface of the first sapphire substrate and the second sapphire substrate are cleaned and dried, so that the cleanliness of the first surface and the second surface of the first sapphire substrate and the second sapphire substrate is ensured.

[0071] Optionally, the second surface of the first sapphire substrate and the second sapphire substrate is cleaned and dried, comprising:

[0072] The first sapphire substrate and the second sapphire substrate are cleaned with RCA solution mixed with ammonia and H2O2 for 10-20 min;

[0073] The first sapphire substrate and the second sapphire substrate are rinsed with 0.025-0.05% HF solution;

[0074] The first sapphire substrate and the second sapphire substrate are dried in an air environment at 200-300℃.

[0075] The first sapphire substrate and the second sapphire substrate are cleaned with RCA solution mixed with ammonia and H2O2, which helps to remove the surface metal impurities of the second surface of the first sapphire substrate and the second sapphire substrate; the first sapphire substrate and the second sapphire substrate are rinsed with 0.025-0.05% HF solution, which further ensures the cleanliness of the first sapphire substrate and the second sapphire substrate.

[0076] Optionally, a convex microstructure is formed on the first surface of the first sapphire substrate, and a concave microstructure is formed on the first surface of the second sapphire substrate, comprising:

[0077] A first dielectric layer is formed on the first surface of the first sapphire substrate, and the first dielectric layer or the first dielectric layer and the first sapphire substrate are patterned to form the convex microstructure;

[0078] The first surface of the second sapphire substrate is patterned to form the concave microstructure;

[0079] A second dielectric layer is formed on the first surface of the second sapphire substrate, and the second dielectric layer fills the concave microstructure.

[0080] The convex microstructure is formed by using the first dielectric layer, which can reduce the problem of stress concentration when an epitaxial layer is formed on the sapphire substrate, reduce the lattice defects of the epitaxial material (such as gallium nitride), and thus improve the epitaxial growth quality. The second dielectric layer is formed by using MOCVD or PVD deposition on the first surface of the second sapphire substrate, and the second dielectric layer fills the concave microstructure.

[0081] Specifically, the material of the first dielectric layer includes at least one of SiO2, AlN and Si3N4; the material of the second dielectric layer includes at least one of SiC and AlN. The thickness of the first dielectric layer can be set to 2-5 um, and the refractive indexes of SiO2, AlN and Si3N4 in the material of the first dielectric layer are 1.46, 2.16 and 2.04 respectively, which are all lower than the refractive index of GaN (n=2.56), so that the refractive index difference between the convex microstructure and the epitaxial layer can be ensured, the light is from light dense to light beam at the interface between the epitaxial layer and the convex microstructure, the total reflection angle should increase with the increase of the refractive index difference, that is, the probability of total reflection of the light at the interface increases, thereby the reflectivity of the light is improved; the thickness of the second dielectric layer is 1-2 um, and the refractive index of SiC in the material of the second dielectric layer is 2.64, and the thermal conductivity is 490 W / (m K), the refractive index of AlN is 2.16, and the thermal conductivity is 270 W / (m K); the refractive indexes are all higher than the refractive index of the sapphire substrate (n=1.78), compared with the interface formed by the second sapphire substrate and the air layer, the refractive index difference of the interface formed by the second dielectric layer and the air layer is larger, when the light passes through the interface between the second dielectric layer and the air layer, the total reflection angle of the light increases due to the increase of the refractive index difference, the light is more likely to be totally reflected at the interface, that is, the reflection probability is also increased to avoid the light emission, thereby the reflection efficiency is improved, and the light extraction efficiency of the LED front surface is improved. In addition, the second dielectric layer adopts a material with good thermal conductivity, which is also beneficial to reduce the heat dissipation problem caused by the thickness of the composite structure substrate.

[0082] In the embodiment, the convex microstructure is formed on the first surface of the first sapphire substrate, and the concave microstructure is formed on the first surface of the second sapphire substrate, and the second surfaces of the first sapphire substrate and the second sapphire substrate are bonded to each other through the processing of the second surfaces of the first sapphire substrate and the second sapphire substrate, so that the double-layer patterned sapphire substrate is obtained. The embodiment solves the problem that the existing patterned substrate is limited in improving the light extraction efficiency of the LED, and not only can realize the double-layer sapphire patterned substrate, but also can increase the total reflection angle of the interface by using the difference between the structure characteristics such as the side slope of the two-layer patterned microstructures and the refractive index difference of the interface, increase the reflection of the light, improve the reflection efficiency, improve the light control effect, and further improve the light extraction efficiency of the LED chip. In addition, in the embodiment, the convex microstructure is formed by using the first dielectric layer, and the concave microstructure is formed by using the second dielectric layer, so that the good heat conduction performance of the dielectric material can be used to improve the heat dissipation capacity of the substrate to a certain extent; at the same time, through the thinning processing step in the preparation process, the thickness of the whole substrate can be effectively reduced, and the heat dissipation problem caused by the thick thickness can be prevented.

[0083] Figure 4 A structure schematic diagram of the double-layer patterned sapphire substrate is provided for the embodiment, as shown in Figure 4As shown, the double-layer patterned sapphire substrate is made by using the preparation method of the double-layer patterned sapphire substrate according to any one of the above embodiments;

[0084] The patterned sapphire substrate includes a first sapphire substrate 11 and a second sapphire substrate 12, and each of the first sapphire substrate 11 and the second sapphire substrate 12 includes a first surface and a second surface facing away from each other, as shown, the first sapphire substrate 11 includes a first surface 101 and a second surface 103, and the second sapphire substrate 12 includes a first surface 102 and a second surface 104; the first surface 101 of the first sapphire substrate 11 is formed with a convex microstructure 113; the first surface 102 of the second sapphire substrate 12 is formed with a concave microstructure 123; and the second surface 103 of the first sapphire substrate 11 and the second surface 104 of the second sapphire substrate 12 are bonded to each other.

[0085] In this embodiment, by forming a convex microstructure on the first surface of the first sapphire substrate and a concave microstructure on the first surface of the second sapphire substrate, and through plasma surface activation of the second surfaces of the first sapphire substrate and the second sapphire substrate, the second surfaces of the first sapphire substrate and the second sapphire substrate are plasma activated and bonded to each other, and an integrated double-layer patterned sapphire substrate is obtained. On the basis of the double-layer patterning, by using the difference in the structure characteristics such as the side slope of the two-layer patterned microstructures, the reflection of light can be increased, the reflection efficiency can be improved, the regulation effect on light can be improved, and the light extraction efficiency of the LED chip can be further improved. In addition, the entire substrate can have a relatively thin thickness, avoiding the problem of increased processing and heat dissipation difficulty caused by the over-thickness of the substrate, which is beneficial to the processing and heat dissipation of the LED chip.

[0086] Figure 5 A structure schematic diagram of an LED epitaxial wafer provided by the embodiment of the present application is shown in the figure, which includes any one of the double-layer patterned sapphire substrates provided by the above embodiments 301, and further includes an epitaxial layer 302 on the double-layer patterned sapphire substrate. Figure 5

[0087] Since the LED epitaxial wafer provided by the embodiment includes the double-layer patterned sapphire substrate provided by the above embodiments, it has the same or corresponding beneficial effects as the double-layer patterned sapphire substrate, which will not be described here.

[0088] ​Note that the above merely describes preferred embodiments of the present application and the principles of the technology applied. Those skilled in the art will understand that the present application is not limited to the specific embodiments described herein, and that various obvious changes, modifications, combinations and substitutions can be made by those skilled in the art without departing from the scope of the present application. Therefore, although the present application has been described in detail through the above embodiments, the present application is not limited to the above embodiments, and can include more other equivalent embodiments without departing from the concept of the present application, and the scope of the present application is determined by the scope of the claims.

Claims

1. A method for preparing a double-layer patterned sapphire substrate, characterized in that, The method comprises the following steps: providing a first sapphire substrate and a second sapphire substrate, each of the first sapphire substrate and the second sapphire substrate comprising a first surface and a second surface facing away from each other; forming a convex microstructure on the first surface of the first sapphire substrate and a concave microstructure on the first surface of the second sapphire substrate; performing a thinning treatment on the second surface of the first sapphire substrate and the second sapphire substrate; performing an O2 plasma surface activation treatment on the second surface of the first sapphire substrate and the second sapphire substrate; cleaning the second surface of the first sapphire substrate and the second sapphire substrate with ammonia water to form Al-OH chemical bonds; bonding the second surfaces of the first sapphire substrate and the second sapphire substrate to each other and performing vacuum heat treatment to bond the second surfaces of the first sapphire substrate and the second sapphire substrate to each other.

2. The method of claim 1, wherein the method further comprises: Before forming the convex microstructure on the first surface of the first sapphire substrate and the concave microstructure on the first surface of the second sapphire substrate, the method further comprises the following steps: cleaning and drying the first surface of the first sapphire substrate and the second sapphire substrate; and / or, before performing the O2 plasma surface activation treatment on the second surface of the first sapphire substrate and the second sapphire substrate, the method further comprises the following steps: cleaning and drying the second surface of the first sapphire substrate and the second sapphire substrate.

3. The method of claim 2, wherein the method further comprises: The cleaning and drying the first surface of the first sapphire substrate and the second sapphire substrate comprises the following steps: immersing the first sapphire substrate and the second sapphire substrate in a mixed solution of H2SiO4 and H2O2 for acid cleaning for 20-30 min; taking out the first sapphire substrate and the second sapphire substrate and performing spin-drying or drying treatment.

4. The method of claim 2, wherein the method further comprises: The cleaning and drying the second surface of the first sapphire substrate and the second sapphire substrate comprises the following steps: cleaning the first sapphire substrate and the second sapphire substrate with RCA solution mixed with ammonia water and H2O2 for 10-20 min; rinsing the first sapphire substrate and the second sapphire substrate with 0.025-0.05% HF solution; immersing the first sapphire substrate and the second sapphire substrate in an air environment at 200-300°C for drying treatment.

5. The method of claim 1, wherein the method further comprises: The concentration of the ammonia water is 20-30%.

6. The method of claim 1, wherein the method further comprises: The forming of the convex microstructure on the first surface of the first sapphire substrate and the concave microstructure on the first surface of the second sapphire substrate comprises the following steps: forming a first dielectric layer on the first surface of the first sapphire substrate, and patterning the first dielectric layer or the first dielectric layer and the first sapphire substrate to form the convex microstructure; patterning the first surface of the second sapphire substrate to form the concave microstructure; forming a second dielectric layer on the first surface of the second sapphire substrate, and the second dielectric layer filling the concave microstructure.

7. A double layer patterned sapphire substrate, characterized by, The double-layer patterned sapphire substrate is prepared by the method according to any one of claims 1-6. The patterned sapphire substrate comprises a first sapphire substrate and a second sapphire substrate, and the first sapphire substrate and the second sapphire substrate each comprise a first surface and a second surface facing away from each other. The first surface of the first sapphire substrate is formed with a convex microstructure. The first surface of the second sapphire substrate is formed with a concave microstructure.

8. The dual layer patterned sapphire substrate of claim 7, wherein, The second surfaces of the first sapphire substrate and the second sapphire substrate are bonded to each other. The convex microstructure comprises a first dielectric layer and a sapphire layer, and the first dielectric layer is located on a side of the sapphire layer facing away from the second sapphire substrate.

9. The dual layer patterned sapphire substrate of claim 7, wherein, The side of the second sapphire substrate facing away from the first sapphire substrate further comprises a second dielectric layer, the second dielectric layer covers the second surface of the second sapphire substrate and fills the concave microstructure. The shape of the convex microstructure comprises at least one of a cone, a mesa, a spherocylinder or a cube, or the shape of the convex microstructure comprises a cone-like shape or a mesa-like shape with a side wall curvature.

10. The dual layer patterned sapphire substrate of claim 8, wherein, The shape of the concave microstructure comprises at least one of a cone, a mesa, a spherocylinder or a cube, or the shape of the concave microstructure comprises a cone-like shape or a mesa-like shape with a side wall curvature.

11. An LED epitaxial wafer, characterized by, The material of the first dielectric layer comprises at least one of SiO2, AlN or Si3N4, and the material of the second dielectric layer comprises at least one of SiC or AlN. The double-layer patterned sapphire substrate according to any one of claims 8-10 further comprises an epitaxial layer on the double-layer patterned sapphire substrate.

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