Patterned composite substrate and LED chip thereof

Abstract

The present application relates to the technical field of semiconductor, in particular to a patterned composite substrate and LED chip thereof. The patterned composite substrate comprises a substrate body and a periodic composite structure protruding from the upper surface of the substrate body; the composite structure comprises a platform and a cone which are stacked; the material of the platform is different from that of the cone; the bottom angle of the cone is smaller than that of the platform. The patterned composite substrate has more light efficiency advantages than other patterned substrates with the same height and bottom diameter, and the brightness of the LED chip is increased by 5% to 10% compared with the conventional conical PSS substrate.

Description

Technical Field

[0001] This invention relates to the field of semiconductor technology, and in particular to a patterned composite substrate and its LED chip. Background Technology

[0002] The luminous efficiency of gallium nitride (GaN)-based LEDs depends on their internal quantum efficiency and light extraction efficiency. Due to the significant lattice and thermal mismatch between GaN and sapphire materials, the GaN epitaxial layer exhibits approximately 10-1 luminous efficiency. 9 cm -2 The high dislocation density of GaN hinders the improvement of LED internal quantum efficiency. Furthermore, the high refractive index of GaN (2.5) results in a small photon exit angle within the LED, with a critical angle for total internal reflection of only 24.6°, leading to a single-sided light extraction efficiency of only 4%. These two factors make it difficult to improve LED luminous efficiency. However, with continuous optimization of epitaxial growth technology, GaN crystal quality has been significantly improved, leading to a substantial increase in device internal quantum efficiency. In particular, the recently developed patterned sapphire substrate (PSS) technology not only weakens the limitation of total internal reflection through pattern scattering, allowing more light to pass through and improving light extraction efficiency, but also enables GaN to achieve a lateral epitaxial effect during epitaxial growth, reducing crystal defect density and further improving internal quantum efficiency. Currently, PSS has become the mainstream substrate material in the LED industry, accounting for over 90% of the total substrate usage. Continuously optimizing the size, morphology, and other parameters of the PSS pattern to improve the crystal quality and light extraction efficiency of the epitaxial layer has become an important way to improve LED performance.

[0003] Furthermore, the refractive index difference at the interface of heterogeneous materials is also a crucial factor affecting photon transmission within LEDs. A larger refractive index difference results in more pronounced photon scattering, which is more conducive to overcoming the limitation imposed by total internal reflection on photon emission and thus improving LED luminous efficiency. Considering that the difference between the refractive index of sapphire (n≈1.78) and that of GaN (n≈2.5) is only about 0.7, it is not conducive to further improving LED luminous efficiency. Moreover, PSS technology has already reached a very high level of development, making it difficult to achieve further breakthroughs in LED luminous efficiency through conventional PSS technology.

[0004] In view of this, the present invention is hereby proposed. Summary of the Invention

[0005] The primary objective of this invention is to provide a patterned composite substrate to address technical problems such as low light extraction efficiency in the prior art.

[0006] A second objective of this invention is to provide an LED chip.

[0007] In order to achieve the above-mentioned objectives of the present invention, the following technical solution is adopted:

[0008] A patterned composite substrate includes a substrate body and a periodic composite structure protruding from the upper surface of the substrate body; the composite structure includes stacked truncated platforms and cones; the materials of the truncated platforms and the cones are different; the base angle α of the cones is smaller than the base angle θ of the truncated platforms.

[0009] Wherein, the base angle θ of the platform refers to the angle between the side surface of the platform and the bottom surface of the platform; the base angle α of the cone refers to the angle between the side surface of the cone and the bottom surface of the cone.

[0010] In a specific embodiment of the present invention, the platform is made of sapphire and the cone is made of SiO2.

[0011] In a specific embodiment of the present invention, the base angle θ of the platform is 45° to 75°, and the ratio of the base angle α of the cone to the base angle θ of the platform is X, where 0.6 ≤ X < 1.

[0012] In a specific embodiment of the present invention, the arrangement period P of the periodic composite structure is 1.5 to 6 μm, preferably 2 to 5 μm.

[0013] In a specific embodiment of the present invention, the bottom diameter D of the platform is 85% to 98% of the arrangement period P. Furthermore, the distance R between two adjacent platforms is 0.03 to 0.9 μm.

[0014] In a specific embodiment of the present invention, when viewed from above, the distance S between the bottom edge and the top edge of the platform is 0.1 to 0.2 μm.

[0015] In a specific embodiment of the present invention, the height H of the composite structure is 55% to 80% of the arrangement period P.

[0016] Specifically, when the bottom surface of the platform is circular, the bottom diameter refers to the diameter of the bottom surface of the platform; when the bottom surface of the platform is elliptical, the bottom diameter refers to the diameter of the circumcircle of the elliptical bottom surface; and when the bottom surface of the platform is polygonal, the bottom diameter refers to the diameter of the circumcircle of the polygonal bottom surface.

[0017] In a specific embodiment of the present invention, the height h of the cone is 70% to 95% of the height H of the composite structure.

[0018] In a specific embodiment of the present invention, the base diameter d of the cone is 75% to 96% of the base diameter D of the platform. The base diameter of the cone and the base diameter of the platform are used interchangeably.

[0019] In a specific embodiment of the present invention, the cross-sectional area of ​​the composite structure parallel to the substrate body gradually decreases in the direction away from the substrate body.

[0020] In one specific embodiment of the present invention, the top surface of the platform and the bottom surface of the cone have the same shape, and the two are stacked accordingly, with the top surface of the platform and the bottom surface of the cone overlapping.

[0021] In another specific embodiment of the present invention, the sidewall surfaces of the platform and / or the sidewall surfaces of the cone are at least partially covered with a covering layer, the covering layer being made of SiO2, TiO2, GaN, AlN, AlGaN, or any combination of the above materials. Further, Furthermore, the thickness of the covering layer is Preferred

[0022] In a specific embodiment of the present invention, the periodic composite structure is formed in a two-dimensional hexagonal close-packed arrangement on the substrate surface.

[0023] In a specific embodiment of the present invention, the frustum includes any one of a frustum of a cylinder, a frustum of a prism, and an elliptic; the cone includes any one of a cone, a pyramid, and an elliptic cone.

[0024] In a specific embodiment of the present invention, the longitudinal section of the platform is an isosceles trapezoid; the longitudinal section of the cone is an isosceles triangle.

[0025] In a specific embodiment of the present invention, the substrate body is a sapphire substrate.

[0026] In a specific embodiment of the present invention, the stage and the substrate body are an integral structure.

[0027] The present invention also provides an LED chip comprising any of the patterned composite substrates described above.

[0028] In a specific embodiment of the present invention, the LED chip further includes an epitaxial layer formed on the patterned composite substrate. Further, the emission wavelength of the epitaxial layer is between 375 nm and 780 nm. For example, the epitaxial layer can be a GaN epitaxial layer.

[0029] In practice, the LED chip can be at least one of the following: a standard chip, a flip chip, and a high-voltage chip.

[0030] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0031] (1) The patterned composite substrate provided by the present invention forms a composite pattern with two dielectric materials, silicon dioxide and sapphire, on a sapphire substrate. On the one hand, it makes full use of the difference in GaN growth rate between the sapphire sidewall region at the bottom of the composite pattern and the spacing region of the composite pattern. At the same time, combined with the stacking fault effect formed by the SiO2 pattern sidewall, the dislocations generated in GaN during the production process are bent, effectively suppressing the extension of dislocations into the quantum well region, thereby significantly improving the internal quantum efficiency and antistatic capability of the LED device. On the other hand, the SiO2 dielectric at the top of the composite pattern has a refractive index of about 1.45, which is lower than that of sapphire material, and is more conducive to improving the light extraction efficiency of the LED.

[0032] (2) The patterned composite substrate of the present invention has a greater light efficiency advantage than other patterned substrates with the same height and bottom diameter, and the brightness of the LED chip is increased by 5% to 10% compared with conventional conical PSS substrates. In addition, the patterned composite substrate of the present invention has a significant brightening effect on upright chips, flip chips and high voltage chips. Attached Figure Description

[0033] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0034] Figure 1 This is a schematic diagram of the structure of an LED chip provided in an embodiment of the present invention;

[0035] Figure 2 This is a schematic diagram of the structure of the patterned composite substrate provided in an embodiment of the present invention;

[0036] Figure 3 A cross-sectional view (a) and a top view (b) of a patterned composite substrate provided in an embodiment of the present invention;

[0037] Figure 4 A schematic diagram of the hexagonal close-packed arrangement of the patterned composite substrate provided in an embodiment of the present invention;

[0038] Figure 5 A flowchart of a method for preparing a patterned composite substrate provided in an embodiment of the present invention;

[0039] Figure 6 A schematic diagram of the patterned composite substrate fabrication method provided in an embodiment of the present invention;

[0040] Figure 7A tilted SEM image of the patterned composite substrate provided in an embodiment of the present invention;

[0041] Figure 8 This is a top SEM view of the patterned composite substrate provided in an embodiment of the present invention;

[0042] Figure 9 This is a schematic diagram of the structure of a patterned composite substrate provided in another embodiment of the present invention;

[0043] Figure 10 This is a magnified SEM image of a physical part of the patterned composite substrate provided in this embodiment;

[0044] Figure 11 This is a schematic diagram of the GaN epitaxial wafer in Comparative Example 1;

[0045] Figure 12 XRD rocking curves of GaN epitaxial wafer (a) corresponding to the patterned composite substrate provided in the embodiments of the present invention and GaN epitaxial wafer (b) corresponding to the conventional conical PSS substrate;

[0046] Figure 13 The luminous flux of the patterned composite substrate LED chip and the conventional conical PSS substrate LED chip provided in the embodiments of the present invention is compared.

[0047] Figure label:

[0048] 1- Patterned composite substrate; 2- N-type GaN layer; 3- MQW quantum well layer;

[0049] 4-P-type GaN layer; 11-Substrate body; 12-Composite structure;

[0050] 121-Platform; 122-Cone; 123-Covering layer;

[0051] 15-Sapphire substrate; 16-Silicon dioxide thin film layer; 17-Mask pattern structure;

[0052] 18 - Photoresist layer. Detailed Implementation

[0053] The technical solution of the present invention will be clearly and completely described below with reference to the accompanying drawings and specific embodiments. However, those skilled in the art will understand that the embodiments described below are some embodiments of the present invention, but not all embodiments, and are only used to illustrate the present invention, and should not be regarded as limiting the scope of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall be followed. Where the manufacturers of reagents or instruments are not specified, they are all conventional products that can be purchased commercially.

[0054] In the description of this invention, it should be noted that the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0055] This invention provides an LED chip comprising a patterned composite substrate and an epitaxial layer formed on the patterned composite substrate. Further, the emission wavelength of the epitaxial layer is between 375 nm and 780 nm, and the epitaxial layer may be a GaN epitaxial layer. In practical operation, the LED chip may be at least one of a conventional chip, a flip chip, and a high-voltage chip.

[0056] Figure 1 This is a schematic diagram of the LED chip provided in an embodiment of the present invention. Figure 1 As shown, the LED chip includes a patterned composite substrate 1, an N-type GaN layer 2, an MQW quantum well layer 3, and a P-type GaN layer 4 arranged sequentially.

[0057] Figure 2 This is a schematic diagram of the structure of the patterned composite substrate provided in an embodiment of the present invention; Figure 3 A cross-sectional view (a) and a top view (b) of a patterned composite substrate provided in an embodiment of the present invention; Figure 4 This is a schematic diagram illustrating the hexagonal close-packed arrangement of the patterned composite substrate provided in an embodiment of the present invention. (See diagram below.) Figures 2-4As shown, the patterned composite substrate provided in this embodiment includes a substrate body 11 and a periodic composite structure 12 protruding from the upper surface of the substrate body 11. The composite structure 12 includes a stacked platform 121 and a cone 122. The cone 122 is disposed on the platform 121. The platform 121 and the cone 122 are made of different materials; specifically, the platform 121 is made of sapphire, and the cone 122 is made of SiO2. The base angle θ of the platform 121 is 45° to 75°, preferably 51° to 68°, and the base angle α of the cone 122 is smaller than the base angle θ of the platform 121.

[0058] Wherein, the base angle θ of the platform 121 refers to the angle between the side surface of the platform 121 and the bottom surface of the platform 121; the base angle α of the cone 122 refers to the angle between the side surface of the cone 122 and the bottom surface of the cone 122.

[0059] In different embodiments, the base angle θ of the platform 121 can be 45°, 47°, 49°, 51°, 55°, 58°, 60°, 62°, 65°, 68°, 70°, 72°, 75°, etc.

[0060] Furthermore, the ratio of the base angle α of the cone 122 to the base angle θ of the frustum 121 is X, and satisfies 0.6 ≤ X < 1. In different embodiments, the ratio X of the base angle α of the cone 122 to the base angle θ of the frustum 121 can be 0.6, 0.65, 0.7, 0.75, 0.8, 0.85, 0.9, 0.95, etc.

[0061] Furthermore, the arrangement period P of the periodic composite structure 12 is 1.5 to 6 μm, preferably 2 to 5 μm.

[0062] In different embodiments, the arrangement period P of the periodic composite structure 12 can be 1.5μm, 2μm, 2.5μm, 3μm, 3.5μm, 4μm, 4.5μm, 5μm, 5.5μm, 6μm, etc.

[0063] Furthermore, the bottom diameter D of the platform 121 is 85% to 98% of the arrangement period P. Furthermore, the distance R between two adjacent platforms 121 is 0.03 to 0.9 μm, and further, the distance R between two adjacent platforms 121 is 0.1 to 0.5 μm.

[0064] In different embodiments, the bottom diameter D of the platform 121 can be 85%, 88%, 90%, 92%, 95%, 98%, etc., of the arrangement period P. The distance R between two adjacent platforms 121 can be 0.1μm, 0.15μm, 0.2μm, 0.25μm, 0.3μm, 0.4μm, 0.45μm, 0.5μm, etc.

[0065] Specifically, when the bottom surface of the platform is circular, the bottom diameter D of the platform 121 refers to the diameter of the bottom surface of the platform; when the bottom surface of the platform is elliptical, the bottom diameter D of the platform 121 refers to the diameter of the circumcircle of the elliptical bottom surface of the platform; when the bottom surface of the platform is polygonal, the bottom diameter D of the platform 121 refers to the diameter of the circumcircle of the polygonal bottom surface of the platform.

[0066] Furthermore, the height H of the composite structure 12 is 55% to 80% of the arrangement period P.

[0067] In different embodiments, the height H of the composite structure 12 can be 55%, 60%, 65%, 70%, 75%, 80%, etc. of the arrangement period P.

[0068] Furthermore, the height h of the cone 122 is 70% to 95% of the height H of the composite structure 12.

[0069] In different embodiments, the height h of the cone 122 can be 70%, 72%, 75%, 78%, 80%, 82%, 85%, 88%, 90%, 92%, 95%, etc., of the height H of the composite structure 12.

[0070] Furthermore, the base diameter d of the cone 122 is 75% to 96% of the base diameter D of the platform 121. The base diameter d of the cone and the base diameter D of the platform are used interchangeably.

[0071] In different embodiments, the bottom diameter d of the cone 122 can be 75%, 78%, 80%, 82%, 85%, 88%, 90%, 92%, 95%, 96%, etc., of the bottom diameter D of the platform 121.

[0072] Furthermore, when viewed from above, the distance S between the bottom edge and the top edge of the platform 121 is 0.1 to 0.2 μm.

[0073] Furthermore, the cross-sectional area of ​​the composite structure 12 parallel to the substrate body 11 gradually decreases in the direction away from the substrate body 11.

[0074] Furthermore, the top surface of the platform 121 has the same shape as the bottom surface of the cone 122, and the two are stacked accordingly, with the top surface of the platform 121 coinciding with the bottom surface of the cone 122.

[0075] Furthermore, the periodic composite structure 12 is formed in a two-dimensional hexagonal close-packed arrangement on the surface of the substrate body 11.

[0076] Furthermore, the frustum 121 includes any one of a frustum of a cylinder, a truncated pyramid, and an elliptic; the cone 122 includes any one of a cone, a truncated pyramid, and an elliptic cone. In one embodiment, the frustum 121 is a frustum of a cylinder, and the cone 122 is a cone.

[0077] Furthermore, the longitudinal section of the platform 121 is an isosceles trapezoid; the longitudinal section of the cone 122 is an isosceles triangle.

[0078] Furthermore, the substrate body 11 is a sapphire substrate. Furthermore, the stage 121 and the substrate body 11 are an integral structure.

[0079] Figure 9 This is a schematic diagram of a patterned composite substrate provided in another embodiment of the present invention. Further, at least partially, a capping layer 123 covers the sidewall surfaces of the platform 121 and / or the sidewall surfaces of the cone 122. The capping layer 123 is made of SiO2, TiO2, GaN, AlN, AlGaN, or any combination of the above materials. The capping layer 123 reduces lattice mismatch between the substrate pattern and the epitaxial layer.

[0080] Furthermore, the exposed upper surface of the substrate body 11 is at least partially covered by a cover layer 123.

[0081] In practice, the structural parameters of the patterned composite substrate can be achieved using conventional processes.

[0082] Example 1

[0083] This embodiment provides a patterned composite substrate, the structure of which is referenced. Figure 2 The patterned composite substrate includes a substrate body 11 and a periodic composite structure 12 protruding from the upper surface of the substrate body 11. The substrate body 11 is a sapphire substrate. The composite structure 12 includes a stacked platform 121 and a cone 122. The platform 121 is made of sapphire, and the cone 122 is made of SiO2. The platform 121 is a frustum, and the cone 122 is a cone. The platform 121 and the substrate body 11 are an integral structure, and the cone 122 is disposed on the platform 121.

[0084] The periodic composite structure 12 is formed in a two-dimensional hexagonal close-packed arrangement on the upper surface of the substrate body 11.

[0085] The periodicity P of the periodic composite structure 12 is 3μm±0.1μm, the bottom diameter D of the platform 121 is 2.85μm±0.1μm, and the height H of the composite structure 12 is 1.95μm±0.1μm.

[0086] The height h of the cone 122 is approximately 85% of the height H of the composite structure 12, and the bottom diameter d of the cone 122 is approximately 89.5% of the bottom diameter D of the platform 121.

[0087] Based on the above dimensions, the base angle θ of the platform 121 and the base angle α of the cone 122 can be obtained respectively. The base angle θ of the platform 121 and the base angle α of the cone 122 can be 62.9°±1° and 52.4°±1° respectively.

[0088] This invention also provides a method for preparing a patterned composite substrate. Figure 5 This is a flowchart of the patterned composite substrate fabrication method provided in the embodiments of the present invention. Figure 6 This is a schematic diagram of the patterned composite substrate fabrication method provided in an embodiment of the present invention, for reference. Figure 5 and Figure 6 The fabrication method of this patterned composite substrate includes the following steps:

[0089] (1) Provide a sapphire substrate 15;

[0090] refer to Figure 6 In (a), the sapphire substrate 15 is a flat Al2O3 sapphire substrate with a surface crystal orientation of (0001) and atomic-level flatness, and the substrate size is 4 inches.

[0091] (2) A silicon dioxide thin film layer 16 is formed on the surface of the sapphire substrate 15;

[0092] refer to Figure 6 In (b), a silicon dioxide thin film layer 16 is formed on the surface of a sapphire substrate 15 using plasma-enhanced chemical vapor deposition (PECVD). The process parameters, such as temperature, pressure, SiH4 and N2O flow rates, and plasma RF power, are adjusted in the PECVD reaction chamber to deposit the silicon dioxide thin film layer 16 at a uniform rate.

[0093] (3) Using step-by-step lithography, a periodic mask pattern structure 17 is formed on the surface of the silicon dioxide thin film layer 16;

[0094] refer to Figure 6In (c) and (d), firstly, a photoresist layer 18 is spin-coated onto the surface of the silicon dioxide thin film layer 16, and the photoresist layer 18 is fabricated into a periodic cylindrical mask pattern structure 17 arranged in a hexagonal close-packed manner by a step-through exposure process.

[0095] (4) Using plasma dry etching technology, the mask pattern structure 17 is transferred to the surface of silicon dioxide thin film layer 16 and sapphire substrate 15 by etching to form a protruding periodic composite structure.

[0096] refer to Figure 6 In step (e), the photoresist mask pattern is transferred to the silicon dioxide thin film layer 16 using plasma dry etching technology; as shown in the figure. Figure 6 In step (f), the etching continues until it reaches the sapphire substrate 15, and finally the photoresist mask pattern is transferred to the silicon dioxide thin film layer 16 and the sapphire substrate 15, thereby forming a protruding periodic composite structure.

[0097] The process conditions for the aforementioned plasma dry etching are as follows: the etching gas is a mixture of trifluoromethane and boron trichloride, with flow rates of 10 sccm and 10 sccm respectively; the upper electrode power is 1400W, and the lower electrode power is 600W. The cleaning process conditions after etching are as follows: cleaning is performed using a mixed solution of concentrated sulfuric acid and hydrogen peroxide, with a volume ratio of 5:1, and the operating temperature is 120℃. After cleaning, the product is dried using a spin dryer and can then be directly used for gallium nitride epitaxial growth.

[0098] Figure 7 and Figure 8 The images shown are a tilted SEM image and a top view of the patterned composite substrate prepared in this embodiment.

[0099] The arrangement of the periodic composite structure 12 on the upper surface of the substrate body 11, the arrangement period P, and the bottom diameter of the platform 121 are related to the mask pattern structure 17 in step (3). The periodic composite structure 12 can be adjusted by adjusting the arrangement, arrangement period, and pattern size of the mask pattern structure 17. The height of the cone 122 and the height of the platform 121 in the periodic composite structure 12 are related to the thickness of the silicon dioxide thin film layer 16 formed on the sapphire substrate 15 in step (2) and the plasma dry etching technology used in step (4).

[0100] In a modified embodiment of Example 1, the periodic composite structure is uniformly distributed on the substrate body 11, with approximately the same spacing between adjacent patterns. The arrangement period P of the periodic composite structure is 4 μm ± 0.2 μm, the base diameter D of the platform 121 is 3.5 μm ± 0.2 μm, and the height H of the composite structure is 2.4 μm ± 0.2 μm. The height h of the cone is 2 μm ± 0.1 μm, and the base diameter d of the cone 122 is 3.1 μm ± 0.2 μm.

[0101] Based on the above dimensions, the base angle θ of the platform 121 and the base angle α of the cone 122 can be obtained respectively. For example, the base angle θ of the platform 121 and the base angle α of the cone 122 can be 63°±1° and 52°±1° respectively.

[0102] Example 2

[0103] This embodiment provides a patterned composite substrate, the structural schematic of which is shown in the reference diagram. Figure 9 The patterned composite substrate includes a substrate body 11 and a periodic composite structure 12 protruding from the upper surface of the substrate body 11. The substrate body 11 is a sapphire substrate. The composite structure 12 includes stacked platforms 121 and cones 122, and a capping layer 123 that at least partially covers the sidewall surfaces of the platforms 121 and / or the cones 122. The material of the capping layer 123 may be the same as or different from the material of the cones. The capping layer 123 also covers the upper surface of the substrate body 11 between adjacent platforms 121 of the periodic composite structure 12. The platform 121 is made of sapphire, the cone 122 is made of SiO2, and the capping layer 123 is made of SiO2, TiO2, GaN, AlN, AlGaN, or any combination of the above materials. For example, the capping layer 123 is a bilayer structure or a superlattice structure composed of AlN and GaN layers. The capping layer 123 further improves the lattice mismatch between the patterned composite substrate and the subsequently grown epitaxial layer, thereby improving the crystal quality of the epitaxial wafer. Alternatively, the capping layer 123 can also be a Bragg reflective layer formed by alternating distributions of SiO2 and TiO2.

[0104] The platform 121 is a frustum of a cone, and the cone 122 is a cone. The platform 121 and the substrate body 11 are an integral structure, the cone 122 is disposed on the platform 121, and the capping layer 123 is deposited on the sidewall surface of the periodic composite structure 12 and the upper surface of the substrate body 11.

[0105] The steps of the fabrication method for the patterned composite substrate in this embodiment include:

[0106] Following steps (1) to (4) of the preparation method in Example 1, a capping layer 123 is deposited on the composite structure, such that the capping layer 123 at least partially covers the sidewall surfaces of the cone 122 and the platform 121, and at least partially covers the upper surface of the substrate body 11 between adjacent platforms 121. Specifically, an AlN layer can be deposited first by PVD, and then a GaN buffer layer can be deposited on the AlN layer by MOCAD. Furthermore, the thickness of the covering layer 123 is

[0107] Figure 10 This is a magnified SEM image of a portion of the patterned composite substrate obtained in this embodiment, corresponding to a structural schematic. Figure 9 The enlarged view of point A shown in the image.

[0108] Example 3

[0109] This embodiment provides an LED chip, the structure of which is referenced. Figure 1 The LED chip consists of a patterned composite substrate 1, an N-type GaN layer 2, an MQW quantum well layer 3, and a P-type GaN layer 4 arranged sequentially.

[0110] The structural parameters of the patterned composite substrate 1 are as described in Embodiment 2. Specifically, the patterned composite substrate includes a substrate body 11 and a periodic composite structure 12 protruding from the upper surface of the substrate body 11. The composite structure 12 includes a platform 121 made of the same material as the substrate body, a cone 122 formed on the platform, and a cover layer 123 disposed on the sidewall surfaces of the platform 121 and the cone 122. The cover layer 123 simultaneously covers the upper surface of the substrate body 11 between adjacent platforms 121.

[0111] The substrate 11 and the platform 121 are made of sapphire Al2O3, the cone 122 is made of SiO2, and the capping layer 123 comprises a bilayer structure consisting of an AlN layer and a GaN buffer layer. The thickness of the AlN layer is... The thickness of the GaN buffer layer is

[0112] Comparative Example 1

[0113] Comparative Example 1 provides a GaN epitaxial wafer formed on a conventional conical PSS substrate 1', such as Figure 11 As shown, it includes a PSS substrate 1' and an N-type GaN layer 2', an MQW quantum well layer 3', and a P-type GaN layer 4' sequentially deposited on its upper surface.

[0114] PSS substrate 1' includes a sapphire substrate and a periodic pattern on the substrate surface. The periodic pattern is a cone made of sapphire material, and the cone and the substrate are an integral structure. A capping layer is formed on the sidewall surface of the cone and on the upper surface of the substrate between adjacent cones. The cyclic arrangement, period, height, pattern diameter, and capping layer of the periodic pattern are the same as in Example 3.

[0115] Experimental Example 1

[0116] To illustrate the differences between different substrates, the conventional conical PSS substrate of Comparative Example 1 and the patterned composite substrate of Example 3 of the present invention, which have the same size and specifications, were co-grown in an MOCVD equipment under the same epitaxial growth conditions to produce identical LED epitaxial layer structures (growing conditions, etc., adopted existing conventional techniques). After XRD testing, LED chips with identical structures were fabricated using conventional semiconductor processes, and the luminous flux of the two LED chips was tested under the same test conditions.

[0117] like Figure 12 As shown, the full width at half maximum (FWHM) of the XRD rocking curve (002) of the GaN epitaxial layer of the patterned composite substrate in Example 3 is 122 arcsec, which is 67 arcsec lower than the 189 arcsec of the epitaxial layer corresponding to the conventional conical PSS in Comparative Example 1. This indicates that the patterned composite substrate of the present invention utilizes the large number of stacking faults formed in GaN near the SiO2 pattern sidewalls to block mismatched dislocations originating from the GaN / sapphire interface, significantly reducing the dislocation density of the GaN epitaxial material and improving the crystal quality of the GaN epitaxial layer.

[0118] like Figure 13 As shown, the luminous flux of the LED chip obtained using the patterned composite substrate of Embodiment 3 of the present invention is significantly improved compared to the LED chip obtained using a conventional conical PSS substrate. Based on a comparison of the luminous flux data of GaN-based LED chips at different wavelengths on two 4-inch substrates, the luminous flux of the LED chip on the patterned composite substrate of this embodiment is 5% to 10% higher than that of the LED chip on a conventional conical PSS substrate.

[0119] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features. These modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention. In particular, it should be understood that due to the limitations of the preparation method of patterned composite substrates, it is difficult for all patterns in a substrate to be completely identical, and there will also be differences between substrates formed in the same batch.

Claims

1. A patterned composite substrate, characterized in that, The system includes a substrate body and a periodic composite structure protruding from the upper surface of the substrate body; the composite structure includes stacked truncated pyramids and cones; the materials of the truncated pyramids and the cones are different; the base angle α of the cones is smaller than the base angle θ of the truncated pyramids. The base angle θ of the platform is 45°~75°; The base diameter D of the platform is 85% to 98% of the arrangement period P of the periodic composite structure; The ratio of the base angle α of the cone to the base angle θ of the frustum is X, where 0.6 ≤ X < 1; The height H of the composite structure is 55% to 80% of the arrangement period P; The height h of the cone is 70% to 95% of the height H of the composite structure.

2. The patterned composite substrate according to claim 1, characterized in that, The platform is made of sapphire, and the cone is made of SiO2.

3. The patterned composite substrate according to claim 1, characterized in that, The arrangement period P of the periodic composite structure is 1.5~6μm.

4. The patterned composite substrate according to claim 3, characterized in that, The arrangement period P of the periodic composite structure is 2~5μm.

5. The patterned composite substrate according to claim 1, characterized in that, The base diameter d of the cone is 75% to 96% of the base diameter D of the truss.

6. The patterned composite substrate according to claim 1, characterized in that, The distance R between two adjacent platforms is 0.03~0.9μm.

7. The patterned composite substrate according to claim 1, characterized in that, When viewed from above, the distance S between the bottom edge and the top edge of the platform is 0.1~0.2μm.

8. The patterned composite substrate according to any one of claims 1-7, characterized in that, The sidewall surfaces of the platform and / or the cone are at least partially covered with a covering layer.

9. The patterned composite substrate according to claim 8, characterized in that, The thickness of the covering layer is ≥50 Å.

10. The patterned composite substrate according to claim 8, characterized in that, The covering layer is any one or a combination of materials selected from SiO2, TiO2, GaN, AlN, or AlGaN.

11. An LED chip, characterized in that, Includes the patterned composite substrate as described in any one of claims 1-10.

12. The LED chip according to claim 11, characterized in that, It also includes an epitaxial layer formed on the patterned composite substrate.

13. The LED chip according to claim 12, characterized in that, The emission wavelength of the epitaxial layer is between 375nm and 780nm.

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