A patterned composite substrate, LED epitaxial wafer and preparation method thereof

Abstract

The embodiment of the present invention discloses a patterned composite substrate, an LED epitaxial wafer and a method for preparing the same. The patterned composite substrate includes a substrate base, a plurality of composite microstructures located on the substrate base, the composite microstructures include a heterogeneous layer and a substrate layer stacked up and down, the substrate layer and the substrate base are an integral structure; the surface where the substrate layer and the heterogeneous layer intersect is provided with at least one concave hole and / or at least one protrusion, the heterogeneous layer and the substrate layer constitute a composite microstructure protrusion. The embodiment of the present invention solves the problem that the internal quantum efficiency and light extraction efficiency of the existing patterned composite substrate are still low. On the one hand, it can improve the crystal quality of the epitaxial material and improve the internal quantum efficiency. On the other hand, it can increase the light reflection angle and improve the light extraction efficiency, which helps to improve the light extraction efficiency of the correspondingly prepared LED chip.

Description

Technical Field

[0001] The embodiments of the present invention relate to the field of semiconductor manufacturing technology, and in particular to a patterned composite substrate, an LED epitaxial wafer and a preparation method thereof. Background Art

[0002] Sapphire is the most common substrate for GaN growth due to its advantages such as good physical and chemical stability, non-absorption of visible light, moderate price, and mature manufacturing technology. However, due to the large lattice mismatch and thermal mismatch between GaN and sapphire, the dislocation and defect density of GaN grown on the sapphire substrate is large, which ultimately has an adverse effect on the luminous efficiency and life of LED devices.

[0003] With the development of technology, patterned sapphire substrate (PSS) has shown obvious advantages. On the one hand, the PSS structure changes the growth process of GaN by preparing a fine structure on the sapphire surface, causing the lattice mismatch dislocation to bend and close in the growth area at the bottom of the pattern, effectively inhibiting the extension of defects to the epitaxial surface, reducing epitaxial layer stress, improving crystal growth quality, thereby reducing non-radiative transitions, reducing non-radiative recombination centers, and improving the internal quantum efficiency of LEDs; on the other hand, the patterned GaN / sapphire interface can scatter photons emitted from the active area, allowing the originally fully reflected photons to have the opportunity to be emitted to the outside of the device, which can effectively improve the light extraction efficiency. In summary, the external quantum efficiency of PSS devices is improved due to the improvement of internal quantum efficiency and light extraction efficiency.

[0004] With the development of the industry, consumers have higher and higher requirements for the external quantum efficiency of LEDs. Traditional graphic substrates must start from the two aspects of materials and structure to further improve the internal quantum efficiency and light extraction efficiency to meet market demand. Summary of the invention

[0005] The present invention provides a patterned composite substrate, an LED epitaxial wafer and a preparation method thereof, so as to improve the crystal quality of epitaxial materials and enhance the internal quantum efficiency, and at the same time help to increase the light reflection angle and enhance the light extraction efficiency.

[0006] In a first aspect, an embodiment of the present invention provides a patterned composite substrate, comprising a substrate base plate, and a plurality of composite microstructures located on the substrate base plate, wherein the composite microstructures include a heterogeneous layer and a substrate layer stacked up and down, and the substrate layer and the substrate base plate are an integral structure;

[0007] The surface where the substrate layer and the heterogeneous layer meet is provided with at least one concave hole and / or at least one protrusion, and the heterogeneous layer and the substrate layer form a composite microstructure protrusion.

[0008] Optionally, in each of the composite microstructures, a surface where the substrate layer and the heterogeneous layer intersect is provided with a plurality of recessed holes, and the plurality of recessed holes are periodically arranged at the vertices of a regular polygon, or the plurality of recessed holes are periodically arranged at the vertices and center points of a regular polygon.

[0009] Optionally, the arrangement period of the concave holes is 0.5-3.0 μm, the width of the opening is 0.1-2.0 μm, and the depth is 0.1-1.5 μm.

[0010] Optionally, the ratio of the depth of the cavity to the thickness of the substrate layer is in the range of 50%-300%.

[0011] Optionally, the ratio of the thickness of the substrate layer to the height of the composite microstructure is in the range of 10%-80%.

[0012] Optionally, the recess is an inverted polygonal pyramid, cone, elliptical cone, cylinder, frustum or spherical cap.

[0013] Optionally, in each of the composite microstructures, at least one protrusion is provided on the surface where the substrate layer and the heterogeneous layer intersect, and the protrusion is a polygonal pyramid, a cone, an elliptical cone, a cylinder, a frustum or a spherical cap.

[0014] Optionally, the ratio of the thickness of the substrate layer to the sum of the height of the protrusion and the thickness of the substrate layer is in the range of 5%-20%.

[0015] Optionally, the bottom surface of the protrusion has a width of 0.2-3 μm and a height of 0.12-2.5 μm.

[0016] Optionally, the composite microstructure is a polygonal pyramid, a cone, an elliptical pyramid, a cylinder, a truncated cone or a spherical cap, or the composite microstructure is a quasi-polygonal pyramid, a quasi-cone or a quasi-elliptical pyramid, and the side wall of the composite microstructure has a curvature.

[0017] Optionally, the bottom surface of the composite microstructure has a width of 0.3-5.0 μm and a height of 0.2-3.5 μm.

[0018] Optionally, the material of the heterogeneous layer is at least one of oxide, nitride, carbide and a single substance.

[0019] In a second aspect, an embodiment of the present invention further provides an LED epitaxial wafer, comprising the patterned composite substrate as described in any one of the first aspects, and further comprising an epitaxial layer formed on the patterned composite substrate.

[0020] In a third aspect, an embodiment of the present invention further provides a method for preparing a patterned composite substrate, which is used to prepare the patterned composite substrate as described in any one of the first aspects, comprising:

[0021] Providing a substrate, and performing patterning on the substrate to form at least one concave hole and / or at least one protrusion;

[0022] forming a heterogeneous layer on the substrate;

[0023] The heterogeneous layer and the substrate are patterned to form a plurality of composite microstructures; wherein the composite microstructure comprises a heterogeneous layer and a substrate layer stacked up and down, and the substrate layer and the substrate are an integral structure; the at least one concave hole and / or the at least one protrusion are located on the surface where the substrate layer and the heterogeneous layer intersect, and the heterogeneous layer and the substrate layer constitute a composite microstructure protrusion.

[0024] Optionally, a substrate is provided, and patterning is performed on the substrate to form at least one concave hole and / or at least one protrusion, including:

[0025] forming a first photoresist layer on the substrate;

[0026] Using nanoimprint technology or photolithography technology to form a photoresist mask from the first photoresist layer;

[0027] A dry etching process is adopted to perform photolithography on the substrate using the photoresist mask to form at least one concave hole and / or at least one protrusion.

[0028] Optionally, the first photoresist layer has a thickness ranging from 0.2 to 2 μm.

[0029] Optionally, the heterogeneous layer and the substrate are patterned to form a plurality of composite microstructures, including:

[0030] forming a second photoresist layer on the heterogeneous layer;

[0031] Using nanoimprint technology or photolithography technology, the second photoresist layer is formed into a microstructure photoresist mask, wherein the microstructure photoresist mask includes a plurality of photoresist columns;

[0032] The substrate is photoetched using the microstructure photoresist mask by dry etching process to form a plurality of composite microstructures, wherein the composite microstructures correspond to the photoresist columns one by one and the vertical projections of their geometric centers on the substrate coincide.

[0033] The patterned composite substrate, LED epitaxial wafer and preparation method thereof provided by the embodiments of the present invention form a plurality of composite microstructures on a substrate substrate, wherein the composite microstructures include a heterogeneous layer and a substrate layer stacked up and down, wherein the substrate layer and the substrate substrate are an integral structure; and at least one concave hole and / or at least one protrusion are provided on the surface where the substrate layer and the heterogeneous layer intersect, and the heterogeneous layer and the substrate layer constitute a composite microstructure protrusion. On the one hand, the heterogeneous layer on the upper layer of the composite microstructure can be utilized to inhibit the growth of the epitaxial material on the microstructure side of the substrate, improve the crystal quality of the epitaxial material, and enhance the internal quantum efficiency. On the other hand, the refractive index difference between the heterogeneous layer and the substrate layer, as well as the concave holes at the interface between the heterogeneous layer and the substrate layer, can be utilized to increase the light reflection angle, thereby enhancing the light extraction efficiency, which helps to improve the light output efficiency of the correspondingly prepared LED chip. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 is a structural schematic diagram of a patterned composite substrate provided by an embodiment of the present invention;

[0035] Figure 2 yes Figure 1 A top view of the patterned composite substrate shown;

[0036] Figure 3 and Figure 4 Schematic diagrams of structures of two other patterned composite substrates provided by embodiments of the present invention;

[0037] Figure 5 and Figure 6 are top views of two other patterned composite substrates provided by embodiments of the present invention;

[0038] Figure 7 is a local SEM image of a patterned composite substrate provided by an embodiment of the present invention;

[0039] Figure 8 It is a structural schematic diagram of an LED epitaxial wafer provided by an embodiment of the present invention;

[0040] Fig. 9 is a flow chart of a method for preparing a patterned composite substrate provided by an embodiment of the present invention;

[0041] Fig.10 yes Fig. 9 The structural flow chart of the method for preparing the patterned composite substrate is shown;

[0042] Fig.11 is a flow chart of another method for preparing a patterned composite substrate provided by an embodiment of the present invention;

[0043] Fig.12 yes Fig.11 The structural flow chart of the method for preparing the patterned composite substrate is shown;

[0044] Fig.13 yes Figure 3 The structural flow chart of the method for preparing the graphic composite substrate is shown. DETAILED DESCRIPTION

[0045] The present invention will be further described in detail below in conjunction with the accompanying drawings and embodiments. It is to be understood that the specific embodiments described herein are only used to explain the present invention, rather than to limit the present invention. It should also be noted that, for ease of description, only parts related to the present invention, rather than all structures, are shown in the accompanying drawings.

[0046] Figure 1 is a schematic structural diagram of a patterned composite substrate provided by an embodiment of the present invention, Figure 2 yes Figure 1 The top view of the patterned composite substrate shown in FIG. Figure 1 and Figure 2 The patterned composite substrate includes a substrate 10, a plurality of composite microstructures 11 located on the substrate 10, the composite microstructure 11 includes a heterogeneous layer 112 and a substrate layer 111 stacked up and down, the substrate layer 111 and the substrate 10 are an integral structure; the surface where the substrate layer 111 and the heterogeneous layer 112 intersect is provided with at least one concave hole 1111, and the heterogeneous layer 112 and the substrate layer 111 form a composite microstructure protrusion. Among them, the upper surface of the patterned composite substrate is used to grow an epitaxial layer, and the epitaxial material nucleates on the flat C surface and then grows into an epitaxial layer. Forming the composite microstructure 11 on the substrate 10 can reduce the C surface area of ​​the substrate 10 used for epitaxial growth, reduce the defects generated during epitaxial growth, thereby reducing the dislocation density and ensuring the quality of the epitaxial layer. The heterogeneous layer 112 in the composite microstructure 11 is made of a heterogeneous material, and the heterogeneous material is essentially a material different from the substrate 10 and the epitaxial material relative to the substrate 10 and the epitaxial layer material, such as gallium nitride. Since it is difficult for epitaxial material to grow on the heterogeneous material, that is, the heterogeneous material has the effect of inhibiting the growth of epitaxial material. At this time, the composite microstructure 11 made of heterogeneous material can inhibit the growth of epitaxial material on the side of the microstructure 11, and help the dislocation of the epitaxial material to bend along the side of the microstructure and close at the top of the microstructure, thereby helping to avoid the epitaxial layer stress concentration caused by the growth of epitaxial material on the side and top of the microstructure, and helping to improve the quality of epitaxial growth.

[0047] It should be noted that the heterogeneous layer 112 is the upper half of the composite microstructure 11, and the substrate layer 111 is the lower half of the composite microstructure 11. In essence, when the heterogeneous layer 112 is etched, the surface of the substrate 10 is further etched. Therefore, the substrate layer 111 and the substrate 10 are essentially an integrated structure. In addition, the multiple pits set on the surface of the intersection of the substrate layer 111 and the heterogeneous layer 112 are pre-etched on the substrate 10 by a photolithography process before the heterogeneous layer 112 is formed. By properly adjusting the etching conditions and masks of the photolithography process, the depth, opening and other dimensions, shapes and positions of the pits can be controlled. The formation of multiple pits inside the composite microstructure 11 helps to change the flatness of the interface between the substrate layer 111 and the heterogeneous layer 112, adjust the light reflection angle, so that more photons can escape, and improve the light extraction efficiency.

[0048] Figure 3 and Figure 4 is a schematic diagram of the structure of two other patterned composite substrates provided by embodiments of the present invention. First, refer to Figure 3 The patterned composite substrate includes a substrate 10 and a plurality of composite microstructures 11 located on the substrate 10. The composite microstructure 11 includes a heterogeneous layer 112 and a substrate layer 111 stacked up and down. The substrate layer 111 and the substrate 10 are an integral structure. At least one protrusion 1112 is provided on the surface where the substrate layer 111 and the heterogeneous layer 112 intersect. The heterogeneous layer 112 and the substrate layer 111 constitute a composite microstructure protrusion.

[0049] refer to Figure 4 The patterned composite substrate includes a substrate 10 and a plurality of composite microstructures 11 located on the substrate 10. The composite microstructure 11 includes a heterogeneous layer 112 and a substrate layer 111 stacked up and down. The substrate layer 111 and the substrate 10 are an integral structure. The surface where the substrate layer 111 and the heterogeneous layer 112 intersect is provided with at least one concave hole 1111 and at least one protrusion 1112. The heterogeneous layer 112 and the substrate layer 111 constitute a composite microstructure protrusion.

[0050] Similarly, if Figure 3 and Figure 4 In the patterned composite substrate shown, the protrusion 1112 is also pre-etched on the substrate 10 by a photolithography process before forming the heterogeneous layer 112. By properly adjusting the etching conditions and mask of the photolithography process, the height, bottom surface and other dimensions, shapes and positions of the protrusion can be controlled. At the same time, a composite microstructure with both concave holes and protrusions can be formed. By using the protrusions or concave holes inside the composite microstructure, the reflection angle of light can be adjusted, so that more photons can escape and the light extraction efficiency can be improved.

[0051] It should be noted that Figure 4The patterned composite substrate shown has both concave holes and convex holes inside the same composite microstructure, which is only one embodiment provided by the present invention. In other embodiments, it can be considered that for different composite microstructures, some composite microstructures can have concave holes inside, and some composite microstructures can have convex holes inside. Those skilled in the art can design and prepare according to actual needs, and there is no limitation here.

[0052] The patterned composite substrate provided by the embodiment of the present invention forms a plurality of composite microstructures on a substrate substrate, wherein the composite microstructures include a heterogeneous layer and a substrate layer stacked up and down, wherein the substrate layer and the substrate substrate are an integral structure; and, the surface where the substrate layer and the heterogeneous layer intersect is provided with at least one concave hole and / or at least one protrusion, and the heterogeneous layer and the substrate layer constitute a composite microstructure protrusion, which can solve the problem that the internal quantum efficiency and light extraction efficiency of the existing patterned composite substrate are still low. On the one hand, the heterogeneous layer on the upper layer of the composite microstructure can be utilized to inhibit the growth of the epitaxial material on the microstructure side of the substrate, improve the crystal quality of the epitaxial material, and enhance the internal quantum efficiency. On the other hand, the refractive index difference between the heterogeneous layer and the substrate layer, as well as the concave holes at the interface between the heterogeneous layer and the substrate layer, can be utilized to increase the light reflection angle, thereby enhancing the light extraction efficiency, which helps to improve the light extraction efficiency of the correspondingly prepared LED chip.

[0053] In the patterned composite substrate as described above, the heterogeneous material may be at least one of oxide, nitride, carbide and a simple substance, that is, it may be a single material of oxide, nitride, carbide and a simple substance, or a combination of multiple materials. Specifically, the heterogeneous material can be selected from oxides, nitrides, carbides or single substances, etc., where the oxides can be SiOx, ZnO, TiOx, TaOx, HfO2, ZrOx, AlOx, GaOx, MgOx, BaOx, InOx, SnO2, LiOx, CaOx, CuOx, IrOx, RhOx, CdGeO, InGaZnO, ZnRhO, GaIn2O4, LaO, LaCuO, etc., the nitrides can be SiNx, TiN, WN, CN, BN, LiN, TiON, SiON, CrN, CrNO, etc., the carbides can be SiC, HfC, ZrC, WC, TiC, CrC, etc., and the single substances can be diamond, Si, Mo, Cu, Fe, Ag, Wu, Ni, Al, etc. The substrate 10 can be made of materials such as sapphire, silicon carbide, silicon, gallium nitride, silicon nitride, zinc oxide, spinel, molybdenum, copper, iron, silver, tungsten, nickel or aluminum, for example, a traditional sapphire substrate.

[0054] Considering that the shape of the composite microstructure directly affects the growth quality of the epitaxial layer, it is necessary to reasonably set the shape of the composite microstructure to reduce the dislocation density during epitaxial growth, reduce the generation of defects, and ensure the epitaxial quality. Therefore, the composite microstructure can be set as a polygonal cone, a cone, an elliptical cone, a cylinder, a truncated cone or a spherical crown, or the composite microstructure is a quasi-polygonal cone, a quasi-cone, a quasi-elliptical cone, and the sidewall of the composite microstructure has a curvature. In addition, optionally, the width L0 of the bottom surface of the composite microstructure is 0.3-5.0μm, and the height H0 is 0.2-3.5μm. At this time, the composite microstructure has a certain size. Due to the anisotropy of the heterogeneous material and the substrate material, the epitaxial material can be grown longitudinally and transversely at the flat C surface of the substrate. During the lateral growth process, the dislocation will bend and merge laterally at the top of the composite microstructure due to the stress, thereby preventing the dislocation from extending to the surface of the epitaxial layer, and effectively reducing the dislocation density of the epitaxial layer, thereby improving the crystal quality and internal quantum efficiency.

[0055] Continue to refer Figure 2 Optionally, in each composite microstructure 11 , a plurality of recesses 1111 may be periodically arranged with vertices of a regular polygon. Figure 5 and Figure 6 are top views of two other patterned composite substrates provided by embodiments of the present invention, with reference to Figure 5 and Figure 6 , multiple concave holes 1111 may be arranged periodically at the vertices and center points of the regular polygon. And, further optionally, multiple concave holes 1111 may be arranged periodically at the vertices and center points of the regular polygon, and the shapes of the concave holes 1111 located at the vertices of the regular polygon may be the same as or different from the shapes of the concave holes 1111 located at the center points of the regular polygon. Figure 5 and Figure 6 It can be seen that in the patterned composite substrate provided by the embodiment of the present invention, the concave hole 1111 located at the center of the square and the concave hole 1111 at the vertex of the square can be arranged to have the same shape, and both are conical (such as Figure 5 As shown in FIG. 1 ), the concave hole 1111 at the center of the square and the concave holes 1111 at the vertices of the square may also be configured to have different shapes, wherein the concave hole 1111 at the center of the square may be configured to be a quadrangular pyramid, and the concave holes 1111 at the vertices of the square may be configured to be conical (as shown in FIG. 1 ). Figure 6 shown).

[0056] Optionally, refer to Figure 1 and Figure 2, the arrangement period C of the holes can be set to 0.5-3.0 μm, the width L1 of the opening is 0.1-2.0 μm, and the depth D is 0.1-1.5 μm. At this time, the holes 1111 in the composite microstructure 11 have a certain ability to make the interface between the substrate layer 111 and the heterogeneous layer 112 concave and convex, that is, the concave and convex changes of the interface are relatively large, which can meet the requirements of the light reflection angle, thereby realizing the reflection of light and improving the light extraction efficiency.

[0057] In addition, when preparing the concave hole 1111 and the substrate layer 112, it is necessary to pre-calculate the depth of the concave hole 1111 and the thickness of the substrate layer 112 to ensure that the concave hole 1111 is located inside the composite microstructure 11. Therefore, optionally, the ratio of the depth D of the concave hole 1111 to the thickness H1 of the substrate layer 111 can be set in the range of 50%-300%. Among them, when the ratio of the depth D of the concave hole 1111 to the thickness H1 of the substrate layer 111 is less than or equal to 100%, it means that the concave hole 1111 is located inside the substrate layer 111, and when the ratio is greater than 100%, it means that the depth of the concave hole 1111 is deeper, and the bottom of the concave hole 1111 has extended to the inside of the substrate 10. At the same time, in order to ensure that the light has a reasonable light reflection space when it is transmitted to the inside of the composite microstructure 11, it should be ensured that the substrate layer and the heterogeneous layer have a considerable thickness. Therefore, optionally, the ratio of the thickness H1 of the substrate layer 112 to the height H0 of the composite microstructure 11 may be set in the range of 10%-80%.

[0058] When the concave holes are formed by etching on the substrate 10, the shapes of the concave holes 1111 can be set to be consistent, or the concave holes 1111 can be set to include multiple shapes. Optionally, it can be set to an inverted polygonal cone, cone, elliptical cone, cylinder, truncated cone or spherical cap. By reasonably selecting the concave holes of the above shapes, the light reflection effect of the heterogeneous microstructure in the concave hole can be improved. It should be noted that in the actual etching process to form the concave holes, there may be errors in the shape of the concave holes. The concave holes 1111 can also be inverted polygonal pyramids, cones, elliptical cones, truncated cones, cylinders, polygons, etc. with side wall curvatures, which are not limited here. In addition, the interior of the concave holes in the composite microstructure can be filled with heterogeneous materials, that is, when depositing the heterogeneous layer, the heterogeneous materials can be deposited simultaneously inside the concave holes to achieve the filling of the concave holes. Of course, the shape of the concave holes, the size of the concave hole openings and the process conditions for the deposition of the heterogeneous layers can also be reasonably set so that the interior of the concave holes is not filled with heterogeneous materials, that is, the interior of the concave holes is in a hollow state. In addition, due to process errors, the inside of the cavity can also be partially filled with an appropriate amount of heterogeneous material. In the above cavity structures, it can be ensured that there is a patterned structure inside the composite microstructure, and the patterned structure and the substrate layer have different refractive indices, so that light can be reflected and the light extraction efficiency can be improved.

[0059] for Figure 3 and Figure 4 The graphical composite substrate shown, wherein the protrusions can be optionally set as polygonal cones, cones, elliptical cones, cylinders, truncated cones or spherical caps. In addition, the width L2 of the bottom surface of the protrusion 1112 ranges from 0.2 to 3 μm, and the height H2 ranges from 0.12 to 2.5 μm. Similarly, the protrusions 1112 in the above size range can ensure that there is a certain volume inside the composite microstructure 11, so that the interface between the substrate layer 111 and the heterogeneous layer 112 has a certain convex-concave ability, that is, the concave-convex variation of the interface is relatively large, which can meet the requirements of the light reflection angle, thereby realizing the reflection of light and improving the light extraction efficiency.

[0060] and Figure 1 The same thing as the patterned composite substrate shown is that after the protrusions are prepared, Figure 3 In the graphical composite substrate shown, it is necessary to etch on the dielectric layer 111 to form a composite microstructure protrusion, and it is necessary to over-etch to partially etch the substrate layer 112 at the same time. Therefore, the lower half of the composite microstructure is actually the substrate layer 112. In order to reasonably adjust the position of the protrusion 1112 inside the composite microstructure 11, it is necessary to consider the thickness of the substrate layer 112 in the composite microstructure 11 and the height of the protrusion 1112. In an embodiment of the present invention, optionally, the thickness H1 of the substrate layer 112 accounts for 5%-20% of the sum of the height H2 of the protrusion 1112 and the thickness H1 of the substrate layer 112 H1+H2. At this time, the protrusion 1112 is located at a lower position inside the composite microstructure 11, which can ensure that the light is reflected inside the composite microstructure 11, and prevent the light from escaping from the bottom of the composite microstructure 11, thereby increasing the light extraction and improving the light output efficiency.

[0061] Figure 7 is a local SEM image of a patterned composite substrate provided by an embodiment of the present invention, Figure 7 It can be seen from the graphic composite substrate shown that the composite microstructure 11 therein includes a heterogeneous layer 112 and a substrate layer 111 stacked up and down, and a cavity 1111 is provided on the surface where the substrate layer 111 and the heterogeneous layer 112 intersect. The cavity 1111 can form an inverted spherical crown shape by using etching process and conditions.

[0062] Based on the patterned composite substrate provided in the above embodiment, an embodiment of the present invention further provides an LED epitaxial wafer. Figure 8 is a schematic diagram of the structure of an LED epitaxial wafer provided by an embodiment of the present invention, with reference to Figure 8 The LED epitaxial wafer includes the patterned composite substrate 1 provided in the above embodiment, and also includes an epitaxial layer 2 formed on the patterned composite substrate 1.

[0063] Different LED epitaxial wafer growth technologies are required for forming epitaxial layers on heterogeneous microstructures of different materials, and for the patterned composite substrate provided in the embodiment of the present invention, the epitaxial layer 2 on the LED epitaxial wafer can be a GaN, AlGaN epitaxial layer, etc. Since the LED epitaxial wafer adopts the patterned composite substrate 1 provided in the above embodiment, it has the same beneficial effects as the patterned composite substrate 1.

[0064] In view of the above-mentioned patterned composite substrate, an embodiment of the present invention further provides a method for preparing the patterned composite substrate. Fig. 9 is a flow chart of a method for preparing a patterned composite substrate provided by an embodiment of the present invention. Fig.10 yes Fig. 9 The structural flow chart of the method for preparing the graphic composite substrate shown in FIG. Fig. 9 and Fig.10 , below Figure 1 Taking the patterned composite substrate structure shown as an example, the preparation method of the patterned composite substrate provided by the embodiment of the present invention is introduced. The preparation method includes:

[0065] S110, providing a substrate, and performing patterning on the substrate to form at least one concave hole and / or at least one protrusion;

[0066] refer to Fig. 9 a), wherein the preparation process of the cavity 1111 is usually formed by etching. Since the cavity 1111 needs to be formed inside the final composite microstructure, the specific position, size and number of the cavity prepared in this process need to be coordinated with the position and size of the composite microstructure prepared subsequently. The specific position, size and number can be adjusted by adjusting the mask pattern and etching conditions of the etching process.

[0067] S120, forming a heterogeneous layer on the substrate;

[0068] refer to Fig. 9 As shown in FIG. b), this step is essentially a process of depositing heterogeneous materials to form a heterogeneous layer 112. Generally, the deposition process may be magnetron sputtering, chemical vapor deposition, etc. The heterogeneous materials include oxides, nitrides, carbides, single substances, and combinations thereof.

[0069] S130, patterning the heterogeneous layer and the substrate to form a plurality of composite microstructures; wherein the composite microstructure comprises a heterogeneous layer and a substrate layer stacked up and down, and the substrate layer and the substrate are an integral structure; at least one concave hole and / or at least one protrusion is located on the surface where the substrate layer and the heterogeneous layer intersect, and the heterogeneous layer and the substrate layer constitute a composite microstructure protrusion.

[0070] refer to Fig. 9c), in this step, the patterning process of the heterogeneous layer 112 and the base substrate 10 requires continuing to etch the base substrate 10 after etching the heterogeneous layer 112, and the lower half of the composite microstructure 11 is substantially provided by the base substrate 10.

[0071] Specifically, the embodiment of the present invention also provides a specific preparation method. Fig.11 is a flow chart of another method for preparing a patterned composite substrate provided by an embodiment of the present invention. Fig.12 yes Fig.11 The structural flow chart of the method for preparing the graphic composite substrate shown in FIG. Fig.10 and Fig.11 , the preparation method comprises:

[0072] Step S210, forming a first photoresist layer on the substrate;

[0073] refer to Fig.11 In a), the first photoresist layer 21 is used to etch a concave hole 1111 on the substrate 10 by using a photolithography process. The first photoresist layer 21 can be selected to be a positive photoresist or a negative photoresist, and the thickness of the photoresist can be adjusted by a spin coating or spray coating process, and the thickness can be set to 0.2-2 μm.

[0074] Step S220: using nanoimprint technology or photolithography technology to form a photoresist mask from the first photoresist layer;

[0075] refer to Fig.11 b) of the figure, this step is the step of exposing and developing the first photoresist 21 to form a mask. Taking the positive photoresist as an example, the photoresist 21 in the exposed area is modified so that it can be easily dissolved in a specific solvent, so that the unexposed area forms a photoresist mask, and the photoresist mask is essentially a hole photoresist mask. The hole photoresist mask needs to design the location, shape and size of the hole in advance. When preparing the photoresist mask, the hole pattern is directly transferred to the first photoresist layer 21 using the exposure mask. Of course, those skilled in the art can also use other graphic processes such as nanoimprinting to pattern the photoresist to form a hole photoresist mask, which is not limited here.

[0076] Step S230: adopting a dry etching process and using a photoresist mask to perform photolithography on the substrate to form at least one concave hole and / or at least one protrusion.

[0077] refer to Fig.11c), this step adopts dry etching process to transfer the pattern, and the etching gas used may include BCl3, Cl2, CF4, CHF3, etc. The dry etching process can be sufficient or insufficient. When the etching is sufficient, the concave photoresist mask 210 can be completely removed; when the etching is insufficient, the residual photoresist material can be removed by organic cleaning. Step S240, forming a heterogeneous layer on the substrate;

[0078] Step S250, forming a second photoresist layer on the heterogeneous layer;

[0079] refer to Fig.11 As shown in FIG. e), the second photoresist layer 22 is used to form the composite microstructure 11 by etching on the substrate 10 using a photolithography process. Similarly, the second photoresist layer 22 can optionally use a positive photoresist or a negative photoresist, and the thickness of the photoresist can be adjusted by a spin coating or spray coating process, which will not be described in detail here.

[0080] Step S260: using nanoimprint technology or photolithography technology to form a microstructure photoresist mask from the second photoresist layer, wherein the microstructure photoresist mask includes a plurality of photoresist columns;

[0081] refer to Fig.11 f), in this step, since the size of the composite microstructure 11 is larger than the size of the concave hole 1111, when performing photolithography, there is a significant difference between the mask pattern of the composite microstructure 11 and the mask pattern of the concave hole 1111. Among them, the mask of the composite microstructure 11 is relatively thick, and the pattern of each composite microstructure 11 is relatively large. The composite microstructure photoresist mask 220 is essentially composed of a plurality of photoresist columns 221, each of which can prevent the underlying heterogeneous layer 112 and the substrate 10 from being etched. After etching the area between the photoresist columns 221, the composite microstructure 11 can be formed.

[0082] Step S270: adopting a dry etching process and using a microstructure photoresist mask to perform photolithography on the substrate to form a plurality of composite microstructures, wherein the composite microstructures correspond to the photoresist columns one by one and the vertical projections of the geometric centers on the substrate coincide.

[0083] refer to Fig.11g), since the composite microstructure 11 is formed by using a photoresist column 221 mask, each composite microstructure 11 corresponds to the photoresist column 221 one by one. Moreover, the shape, size and position of the photoresist column 221 directly determine the shape, size and position of the composite microstructure 11, so when designing the mask pattern, the shape of the composite microstructure 11 can be adjusted by setting the pattern of the photoresist column 221. It should also be noted that the shape of the composite microstructure 11 is not only related to the microstructure photoresist mask, but also to the process conditions of dry etching. Those skilled in the art can reasonably select the dry etching gas according to actual needs, and can also reasonably set the gas ratio and the dry etching time to obtain a composite microstructure of target shape and size.

[0084] Fig.13 yes Figure 3 The structural flow chart of the method for preparing the graphic composite substrate shown in FIG. Fig.13 , for example Figure 3 The patterned composite substrate shown in FIG. Figure 1 The graphical microstructures shown are basically the same, the only difference is that the reference Fig.13 In step b), when the first photoresist layer is formed into a photoresist mask by using nanoimprint technology or photolithography technology in step S220, the photoresist mask is a raised photoresist mask. The raised photoresist mask is essentially a pattern composed of multiple glue pillars. For example, the bottom diameter of the glue pillars can be set to 0.9 μm, the height of the glue pillars is 1.2 μm, and the period is 3.0 μm.

[0085] For Figure 3 The patterned composite substrate shown, for example, is shown in FIG. Fig.13 Figure c) shows that in the process of ICP dry etching, the specific etching parameters are: upper electrode power 1400W, lower electrode power 600W, BCl3 flow 80sccm, CHF3 flow 18sccm, etching time 1800s; after etching, a sapphire substrate with periodically arranged protrusions is obtained. Among them, the bottom width of the protrusion is 1.5μm and the height is 0.9μm. After this step, since there may be residues on the lithography mask, the etched patterned sapphire substrate can be cleaned with SPM solution (H2SO4:H2O2=1:6). The cleaning time is 10min, the temperature is 110℃, and then rinse with water for 8min and spin dry, and finally a clean patterned sapphire substrate can be obtained.

[0086] In the process of preparing composite microstructures, reference Fig.13 d), a 2.0 μm thick SiO2 heterogeneous layer can be deposited on the surface of the patterned sapphire substrate by chemical vapor deposition technology. The surface of the SiO2 heterogeneous layer is flat and completely covers the protrusions on the sapphire substrate; continue to refer to Fig.13 e) Figure, then a 2.0 μm thick photoresist is applied by spin coating, and the special photomask is used as a mask for exposure, with an exposure time of 196 ms; Fig.13 f), after development, a periodically arranged glue column pattern is obtained on the surface of the SiO2 heterogeneous layer, the glue column bottom diameter is 1.95μm, the glue column height is 2.0μm, and the center of the glue column is aligned with the center of the protrusion on the sapphire substrate; reference Fig.13 g), and finally, the SiO2 heterogeneous layer and the patterned sapphire substrate were etched by ICP dry etching. The recipe parameters were: upper electrode power 1400W, lower electrode power 800W, BCl3 flow rate 100sccm, and etching time 15min. A composite microstructure patterned substrate with a SiO2 heterogeneous layer and a sapphire substrate layer was obtained. The bottom diameter of the composite microstructure protrusion was 2.85μm, the total height was 1.85μm, and the height of the sapphire substrate layer in the composite microstructure protrusion was 180nm.

[0087] Note that the above are only preferred embodiments of the present invention and the technical principles used. Those skilled in the art will understand that the present invention is not limited to the specific embodiments described herein, and that various obvious changes, readjustments, combinations and substitutions can be made by those skilled in the art without departing from the scope of protection of the present invention. Therefore, although the present invention has been described in more detail through the above embodiments, the present invention is not limited to the above embodiments, and may include more other equivalent embodiments without departing from the concept of the present invention, and the scope of the present invention is determined by the scope of the appended claims.

Claims

1. A method for preparing a patterned composite substrate, characterized in that: include: Providing a substrate, and performing patterning on the substrate to form at least one concave hole and / or at least one protrusion; forming a heterogeneous layer on the substrate; The heterogeneous layer and the substrate are patterned to form a plurality of composite microstructures; wherein the composite microstructure comprises a heterogeneous layer and a substrate layer stacked up and down, and the substrate layer and the substrate are an integral structure; the at least one concave hole and / or the at least one protrusion are located on the surface where the substrate layer and the heterogeneous layer intersect, and the heterogeneous layer and the substrate layer constitute a composite microstructure protrusion.

2. The preparation method according to claim 1, characterized in that: Providing a substrate, and patterning the substrate to form at least one concave hole and / or at least one protrusion, comprising: forming a first photoresist layer on the substrate; Using nanoimprint technology or photolithography technology to form a photoresist mask from the first photoresist layer; A dry etching process is adopted to perform photolithography on the substrate using the photoresist mask to form at least one concave hole and / or at least one protrusion.

3. The preparation method according to claim 2, characterized in that: The thickness of the first photoresist layer is in the range of 0.2-2 μm.

4. The preparation method according to claim 1, characterized in that: The heterogeneous layer and the substrate are patterned to form a plurality of composite microstructures, including: forming a second photoresist layer on the heterogeneous layer; Using nanoimprint technology or photolithography technology, the second photoresist layer is formed into a microstructure photoresist mask, wherein the microstructure photoresist mask includes a plurality of photoresist columns; The substrate is photoetched using the microstructure photoresist mask by dry etching process to form a plurality of composite microstructures, wherein the composite microstructures correspond to the photoresist columns one by one and the vertical projections of their geometric centers on the substrate coincide.

5. A patterned composite substrate, characterized in that: The patterned composite substrate is prepared by the method for preparing the patterned composite substrate according to any one of claims 1 to 4, wherein the patterned composite substrate comprises a substrate substrate and a plurality of composite microstructures located on the substrate substrate, wherein the composite microstructure comprises a heterogeneous layer and a substrate layer stacked up and down, and the substrate layer and the substrate substrate are an integral structure; The surface where the substrate layer and the heterogeneous layer meet is provided with at least one concave hole and / or at least one protrusion, and the heterogeneous layer and the substrate layer form a composite microstructure protrusion.

6. The patterned composite substrate according to claim 5, characterized in that: In each of the composite microstructures, a plurality of concave holes are arranged on the surface where the substrate layer and the heterogeneous layer meet, and the plurality of concave holes are periodically arranged at the vertices of a regular polygon, or the plurality of concave holes are periodically arranged at the vertices and center points of a regular polygon.

7. The patterned composite substrate according to claim 6, characterized in that: The arrangement period of the concave holes is 0.5-3.0 μm, the width of the opening is 0.1-2.0 μm, and the depth is 0.1-1.5 μm.

8. The patterned composite substrate according to claim 6, characterized in that: The ratio of the depth of the cavity to the thickness of the substrate layer is in the range of 50%-300%.

9. The patterned composite substrate according to claim 5, characterized in that: The ratio of the thickness of the substrate layer to the height of the composite microstructure is in the range of 10% to 80%.

10. The patterned composite substrate according to claim 6, characterized in that: The concave hole is an inverted polygonal pyramid, cone, elliptical cone, cylinder, truncated cone or spherical cap.

11. The patterned composite substrate according to claim 5, characterized in that: In each of the composite microstructures, at least one protrusion is provided on the surface where the substrate layer and the heterogeneous layer intersect, and the protrusion is a polygonal pyramid, a cone, an elliptical cone, a cylinder, a frustum or a spherical cap.

12. The patterned composite substrate according to claim 11, characterized in that: The ratio of the thickness of the substrate layer to the sum of the height of the protrusion and the thickness of the substrate layer is in the range of 5%-20%.

13. The patterned composite substrate according to claim 11, characterized in that: The bottom surface of the protrusion has a width of 0.2-3 μm and a height of 0.12-2.5 μm.

14. The patterned composite substrate according to claim 5, characterized in that: The composite microstructure is a polygonal pyramid, a cone, an elliptical pyramid, a cylinder, a truncated cone or a spherical cap, or the composite microstructure is a quasi-polygonal pyramid, a quasi-cone or a quasi-elliptical pyramid, and the side wall of the composite microstructure has a curvature.

15. The patterned composite substrate according to claim 5, characterized in that: The bottom surface of the composite microstructure has a width of 0.3-5.0 μm and a height of 0.2-3.5 μm.

16. The patterned composite substrate according to claim 5, characterized in that: The material of the heterogeneous layer is at least one of oxide, nitride, carbide and a single substance.

17. An LED epitaxial wafer, characterized in that: It comprises the patterned composite substrate as described in any one of claims 5 to 16, and also comprises an epitaxial layer formed on the patterned composite substrate.

Images