Sapphire composite substrate and manufacturing method thereof

Abstract

The present invention discloses a sapphire composite substrate and a method for manufacturing the same. The composite substrate comprises a thinned sapphire substrate, a defect barrier layer disposed on the front of the thinned sapphire substrate, a thickening layer for preventing the thinned sapphire substrate from bending, and an adhesive layer for bonding the thickening layer to the back of the thinned sapphire substrate; the defect barrier layer is provided with a plurality of openings, the defect barrier layer is made of a transparent non-conductive material, the lattice of the transparent non-conductive material matches the lattice of the epitaxial layer, and the thickening layer is made of a thermally conductive material. The present invention forms a defect barrier layer with a plurality of openings on the thinned sapphire substrate, effectively reducing the dislocation density of the gallium nitride epitaxial material and reducing the lattice defects; the thickening layer is formed on the back of the thinned sapphire substrate, which can reduce the warping of the substrate.

Description

Technical Field

[0001] The invention relates to the technical field of light emitting diodes, and in particular to a sapphire composite substrate and a manufacturing method thereof. Background Art

[0002] GaN epitaxy is mainly grown on sapphire substrates. Sapphire substrates have many advantages: first, the production technology of sapphire substrates is mature and the device quality is good; second, sapphire has good stability and can be used in high-temperature growth processes; finally, sapphire has high mechanical strength and is easy to handle and clean. Therefore, most processes generally use sapphire as the substrate.

[0003] There are also some problems with using sapphire as a substrate, such as lattice mismatch and thermal stress mismatch, which will produce a large number of defects in GaN epitaxy and cause difficulties in subsequent device processing.

[0004] Sapphire is very hard, second only to diamond in hardness among natural materials, but it needs to be thinned and cut (from 400μm to about 100μm) in the production process of LED devices. Adding equipment to complete the thinning and cutting process requires a large investment.

[0005] Sapphire's thermal conductivity is not very good (about 25W / (m·K) at 100°C). Therefore, when using LED devices, a lot of heat will be conducted; especially for large-area high-power devices, thermal conductivity is a very important consideration. In order to overcome the above difficulties, many people have tried to grow GaN optoelectronic devices directly on silicon substrates to improve thermal and electrical conductivity. However, the price of silicon substrates is too high, which affects the mass production of LED devices. Summary of the invention

[0006] The technical problem to be solved by the present invention is to provide a sapphire composite substrate with low cost, good heat dissipation effect and good quality of the formed epitaxial layer lattice.

[0007] The technical problem to be solved by the present invention is to provide a method for manufacturing a sapphire composite substrate, which does not require grinding of the sapphire substrate, has low cost, good heat dissipation effect, and good quality of the formed epitaxial layer lattice.

[0008] In order to solve the above technical problems, the present invention provides a sapphire composite substrate, comprising a thinned sapphire substrate, a defect barrier layer arranged on the front side of the thinned sapphire substrate, a thickening layer for preventing the thinned sapphire substrate from bending, and an adhesive layer for bonding the thickening layer to the back side of the thinned sapphire substrate;

[0009] The defect barrier layer is provided with a plurality of openings, the openings are etched from the surface of the defect barrier layer to the front side of the thinned sapphire substrate, the defect barrier layer is made of a transparent non-conductive material, and the crystal lattice of the transparent non-conductive material matches the crystal lattice of the epitaxial layer;

[0010] The thickened layer is made of a heat-conducting material, and the thermal expansion coefficient of the heat-conducting material is smaller than the thermal expansion coefficient of the thinned sapphire substrate.

[0011] As an improvement of the above solution, an adhesion layer is provided between the defect barrier layer and the thinned sapphire substrate, the material of the defect barrier layer is SiO2 or Si2N4, and the material of the adhesion layer is Al2O3.

[0012] As an improvement of the above solution, multiple layers of adhesion layers and defect barrier layers are alternately stacked to form a reflector structure.

[0013] As an improvement of the above solution, the thickness of the defect barrier layer is 1000-1500 nm, wherein the thickness of the adhesion layer is 10-100 nm.

[0014] As an improvement of the above solution, the width of the openings is 2 to 5 μm, and the intervals between the openings are 2 to 5 μm.

[0015] As an improvement of the above solution, the thickened layer is an AlN substrate or a SiC substrate, and the material of the bonding layer is Al.

[0016] As an improvement of the above solution, the thickness of the thickened layer is 300-500 μm, and the thickness of the adhesive layer is 300-1000 nm.

[0017] As an improvement of the above solution, the thickness of the thinned sapphire substrate is 90-200 μm.

[0018] Accordingly, the present invention also provides a method for manufacturing a sapphire composite substrate, comprising:

[0019] forming a defect barrier layer on the front side of the thinned sapphire substrate, the defect barrier layer being made of a transparent non-conductive material having a lattice matching that of the epitaxial layer;

[0020] Etching the defect barrier layer to form a plurality of openings, wherein the openings are etched from the defect barrier layer to the front side of the thinned sapphire substrate;

[0021] forming an adhesive layer on the back side of the thinned sapphire substrate;

[0022] The thickened layer is bonded to the adhesive layer, the thickened layer being made of a thermally conductive material having a thermal expansion coefficient that is smaller than a thermal expansion coefficient of the thinned sapphire substrate.

[0023] As an improvement of the above scheme, the thickened layer is bonded to the adhesive layer under the conditions of a pressure of 1 to 3 tons and a temperature of 300 to 350° C., and the bonding time is 30 to 90 minutes.

[0024] The implementation of the present invention has the following beneficial effects:

[0025] The present invention adopts a thinned sapphire substrate, which is cheap and can also improve the heat dissipation effect of the composite substrate.

[0026] The present invention forms a defect barrier layer with a plurality of openings on a thinned sapphire substrate. The defect barrier layer uses a transparent non-conductive material whose lattice matches that of gallium nitride. The openings are used to increase the contact area between the gallium nitride epitaxy and the composite substrate, so that the longitudinal epitaxy of gallium nitride is changed to lateral epitaxy, thereby reducing the dislocation density of the gallium nitride epitaxial material and reducing the lattice defects.

[0027] In addition, the invention forms a thickening layer on the back side of the thinned sapphire substrate, which not only reduces the substrate warping by the thickness of the thickening layer itself, but also further reduces the substrate warping by the material properties of the thickening layer itself, and improves the heat dissipation effect of the composite substrate.

[0028] Secondly, the present invention can alternately stack multiple adhesion layers and defect barrier layers to form a reflector structure, thereby improving the light extraction efficiency of the chip.

[0029] The invention effectively bonds the thickened layer to the back side of the sapphire composite substrate without damaging the thinned sapphire substrate by adjusting the bonding temperature and pressure. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 It is a schematic structural diagram of the sapphire composite substrate of the present invention. DETAILED DESCRIPTION

[0031] In order to make the objectives, technical solutions and advantages of the present invention more clear, the present invention will be further described in detail below with reference to the accompanying drawings.

[0032] See also Figure 1 A sapphire composite substrate provided by the present invention is used in growing gallium nitride epitaxy, which includes a thinned sapphire substrate 10, a defect barrier layer 20 arranged on the front side of the thinned sapphire substrate 10, a thickening layer 40 to prevent the thinned sapphire substrate 10 from bending, and an adhesive layer 30 to bond the thickening layer 40 to the back side of the thinned sapphire substrate 10.

[0033] The thickness of the thinned sapphire substrate 10 of the present invention is only 22% to 45% of the thickness of a general sapphire substrate. Preferably, the thickness of the thinned sapphire substrate 10 is 90 to 200 μm. More preferably, the thickness of the thinned sapphire substrate 10 is 130 to 160 μm. The thinned sapphire substrate 10 of the present invention is formed by dividing a general sapphire substrate and is cheaper than a general sapphire substrate. The existing 4-inch sapphire substrate has a thickness of 450 μm, and the 6-inch sapphire substrate has a thickness of 650 μm.

[0034] The thinner the substrate is, the better the heat dissipation effect is, but the greater the lattice mismatch with the epitaxial layer is, and the substrate is more likely to warp.

[0035] To this end, the present invention forms a defect barrier layer 20 on the front side of the thinned sapphire substrate 10 to reduce defects caused by the lattice mismatch between the thinned sapphire substrate and GaN during the epitaxial growth of GaN.

[0036] Since GaN is epitaxially formed directly on the defect blocking layer 20, the material lattice of the defect blocking layer 20 must match the lattice of GaN, and the defect blocking layer 20 must be a transparent non-conductive material. Preferably, the material of the defect blocking layer 20 is SiO2 or Si2N4.

[0037] The defect barrier layer 20 is provided with a plurality of openings 21, which are etched from the surface of the defect barrier layer 20 to the front surface of the thinned sapphire substrate 10. If the depth of the openings 21 does not reach the thinned sapphire substrate 10, the defect barrier layer will remain, affecting the quality of epitaxial growth.

[0038] The present invention increases the contact area between the GaN epitaxy and the composite substrate by forming a plurality of openings 21 on the defect barrier layer 20; since GaN cannot grow alone on the defect barrier layer, the openings can only be filled by the lateral growth of GaN. Therefore, when growing GaN, the longitudinal epitaxy of GaN is transformed into lateral epitaxy, which can effectively reduce the dislocation density of the GaN epitaxial material and effectively reduce the lattice defects.

[0039] Preferably, the openings 21 are arranged in an array, and the openings 21 are formed in a circular shape. In other embodiments of the present invention, the openings 21 may also be in a triangular, elliptical, square, rectangular or star-shaped shape.

[0040] It should be noted that the width of the openings 21 and the intervals between the openings 21 have an important influence on the formation of GaN epitaxy.

[0041] Preferably, the width of the opening 21 is 2-5 μm. If the width of the opening 21 is less than 2 μm, the formation of GaN epitaxy will be affected; if the width of the opening 21 is greater than 5 μm, the lattice defects of GaN epitaxy will increase.

[0042] Preferably, the intervals between the openings 21 are 2-5 μm. If the intervals between the openings 21 are greater than 5 μm, the formation of GaN epitaxy will be affected. Due to process limitations, the intervals between the openings 21 are rarely less than 2 μm.

[0043] Since the adhesion between the defect barrier layer 20 and the thinned sapphire substrate 10 is poor, in order to prevent the defect barrier layer 20 from falling off, the present invention sets an adhesion layer 50 between the defect barrier layer 20 and the thinned sapphire substrate 10 to firmly fix the defect barrier layer 20 on the thinned sapphire substrate 10. Preferably, the material of the adhesion layer 50 is similar to that of the sapphire substrate 10. Specifically, the material of the adhesion layer 50 is Al2O3. The opening 21 penetrates the defect barrier layer 20 and the adhesion layer 50, and is etched to the front side of the thinned sapphire substrate 10.

[0044] It should be noted that the thickness of the defect barrier layer 20 and the adhesion layer 50 has an important influence on the quality of GaN epitaxy. Preferably, the thickness of the defect barrier layer 20 is 1000-1500nm. If the thickness of the defect barrier layer 20 is less than 1000nm, the thickness is too thin, the effect of reducing lattice defects is not good, and the overall reflectivity of the substrate is insufficient, which reduces the light extraction efficiency of the chip. If the thickness of the defect barrier layer 20 is greater than 1500nm, the thickness is too thick, the longitudinal height of the GaN epitaxial growth is too high, affecting the lateral growth of the GaN epitaxy.

[0045] Preferably, the thickness of the adhesion layer 50 is 10 to 100 nm. More preferably, the thickness of the adhesion layer 50 is 30 to 60 nm. If the thickness of the adhesion layer 50 is less than 10 nm, the thickness is too thin and cannot play the role of adhering to the defect barrier layer 20, thereby causing the defect barrier layer 20 to fall off. If the thickness of the adhesion layer 50 is greater than 100 nm, the thickness is too thick, and there are the following two problems: (1) The manufacturing process is limited. Since the adhesion layer 50 is formed by evaporation, the evaporation temperature of Al2O3 is very high. If the evaporation forms too thick Al2O3, the continuous high temperature is likely to damage the equipment; (2) The crystallization of the evaporated Al2O3 is poor, and it is easy to form light yellow AlO crystals. This crystal will absorb the light emitted by the epitaxial layer, thereby reducing the brightness of the chip.

[0046] Since the defect blocking layer 20 and the adhesion layer 50 of the present invention are two materials with different refractive indices, wherein the material of the adhesion layer 50 is Al2O3 and the material of the defect blocking layer 20 is SiO2 or Si2N4, the present invention can alternately stack multiple layers of adhesion layers 50 and defect blocking layers 20 to form a reflector structure, thereby improving the light extraction efficiency of the chip.

[0047] Since the present invention adopts a thinned sapphire substrate 10, the present invention needs to bond a thickening layer 40 on the back of the thinned sapphire substrate 10 to reduce the warping of the thinned sapphire substrate 10. Specifically, the material of the thickening layer 40 must meet the following requirements: (1) the thermal expansion coefficient of the material must be smaller than the thermal expansion coefficient of the thinned sapphire substrate; (2) the material has good thermal conductivity; (3) high hardness; (4) the material lattice is similar to that of the thinned sapphire substrate.

[0048] Preferably, the thickening layer 40 is an AlN substrate or a SiC substrate. Specifically, the thermal expansion coefficient of AlN is 8.53*10-6 / K, and the thermal expansion coefficient of the sapphire substrate is 7.85*10-6 / K. Therefore, the present invention can avoid thermal expansion warping of the thinned sapphire substrate 10 by bonding the thickening layer 40 on the back of the thinned sapphire substrate 10, and AlN has good thermal conductivity and is suitable for gallium nitride epitaxial growth.

[0049] It should be noted that the thickness of the thickened layer 40 of the present invention plus the thickness of the thinned sapphire substrate 10 is generally equal to the thickness of a conventional sapphire substrate. Preferably, the thickness of the thickened layer 40 is 300 to 500 μm. If the thickness of the thickened layer 40 is too small, it will not prevent the thinned sapphire substrate 10 from warping; if the thickness of the thickened layer 40 is too large, it will affect the heat dissipation effect of the composite substrate.

[0050] Since the thickness of the thickened layer 40 is relatively large and the bonding force between the material of the thickened layer 40 and the material of the thinned sapphire substrate 10 is relatively weak, the present invention bonds the thickened layer 40 to the back side of the thinned sapphire substrate 10 through the bonding layer 30 .

[0051] Specifically, the material of the bonding layer 30 should match the material of the thickening layer 40. When the material of the thickening layer is AlN, preferably, the material of the bonding layer 30 is Al. In addition, when the material of the thickening layer is SiC, the material of the bonding layer 30 may also be Al.

[0052] The thickness of the adhesive layer 30 is 300-1000 nm. If the thickness of the adhesive layer 30 is less than 300 nm, the thickness is too thin and cannot play the role of bonding the thickening layer, which leads to the shedding of the thickening layer.

[0053] The present invention adopts a thinned sapphire substrate, which is cheap and can also improve the heat dissipation effect of the composite substrate.

[0054] The present invention forms a defect barrier layer with a plurality of openings on a thinned sapphire substrate. The defect barrier layer uses a transparent non-conductive material whose lattice matches that of gallium nitride. The openings are used to increase the contact area between the gallium nitride epitaxy and the composite substrate, so that the longitudinal epitaxy of gallium nitride is changed to lateral epitaxy, thereby reducing the dislocation density of the gallium nitride epitaxial material and reducing the lattice defects.

[0055] In addition, the invention forms a thickening layer on the back side of the thinned sapphire substrate, which not only reduces the substrate warping by the thickness of the thickening layer itself, but also further reduces the substrate warping by the material properties of the thickening layer itself, and improves the heat dissipation effect of the composite substrate.

[0056] Secondly, the present invention can alternately stack multiple adhesion layers and defect barrier layers to form a reflector structure, thereby improving the light extraction efficiency of the chip.

[0057] Accordingly, the present invention also provides a method for manufacturing a sapphire composite substrate, comprising the following steps:

[0058] 1. forming a defect barrier layer on the front side of the thinned sapphire substrate;

[0059] The thickness of the thinned sapphire substrate of the present invention is only 22% to 45% of the thickness of a general sapphire substrate. Preferably, the thickness of the thinned sapphire substrate is 90 to 200 μm. More preferably, the thickness of the thinned sapphire substrate is 130 to 160 μm. The thinned sapphire substrate of the present invention is formed by splitting a general sapphire substrate and is cheaper than a general sapphire substrate. The existing 4-inch sapphire substrate has a thickness of 450 μm, and the 6-inch sapphire substrate has a thickness of 650 μm.

[0060] The thinner the substrate is, the better the heat dissipation effect is, but the greater the lattice mismatch with the epitaxial layer is, and the substrate is more likely to warp.

[0061] To this end, the present invention forms a defect barrier layer 20 on the front side of the thinned sapphire substrate to reduce defects caused by the lattice mismatch between the thinned sapphire substrate and GaN during the epitaxial growth of GaN.

[0062] Since GaN is formed directly on the defect barrier layer by epitaxy, the material lattice of the defect barrier layer must match the lattice of GaN, and the defect barrier layer must be a transparent non-conductive material. Preferably, the material of the defect barrier layer is SiO2 or Si2N4.

[0063] Since the adhesion between the defect barrier layer and the thinned sapphire substrate is poor, in order to prevent the defect barrier layer from falling off, the present invention sets an adhesion layer between the defect barrier layer and the thinned sapphire substrate to firmly fix the defect barrier layer on the thinned sapphire substrate. Preferably, the material of the adhesion layer is similar to that of the sapphire substrate. Preferably, the material of the adhesion layer is Al2O3.

[0064] It should be noted that the thickness of the defect barrier layer and the adhesion layer has an important influence on the quality of GaN epitaxy. Preferably, the thickness of the defect barrier layer is 1000-1500nm. If the thickness of the defect barrier layer is less than 1000nm, the thickness is too thin, the effect of reducing lattice defects is not good, and the overall reflectivity of the substrate is insufficient, which reduces the light extraction efficiency of the chip. If the thickness of the defect barrier layer is greater than 1500nm, the thickness is too thick, the longitudinal height of the GaN epitaxial growth is too high, affecting the lateral growth of the GaN epitaxy.

[0065] Preferably, the thickness of the adhesion layer is 10 to 100 nm. More preferably, the thickness of the adhesion layer is 30 to 60 nm. If the thickness of the adhesion layer is less than 10 nm, it is too thin and cannot serve as an adhesion defect barrier layer, which in turn causes the defect barrier layer to fall off. If the thickness of the adhesion layer is greater than 100 nm, it is too thick and there are two problems: (1) The manufacturing process is limited because the adhesion layer is formed by an evaporation process, in which the evaporation temperature of Al2O3 is very high. If the evaporation forms too thick Al2O3, the continuous high temperature can easily damage the equipment; (2) The crystallization of the evaporated Al2O3 is poor, and it is easy to form light yellow AlO crystals, which absorb the light emitted by the epitaxial layer, thereby reducing the brightness of the chip.

[0066] Since the defect barrier layer and the adhesion layer of the present invention are two materials with different refractive indices, wherein the material of the adhesion layer is Al2O3 and the material of the defect barrier layer is SiO2 or Si2N4, the present invention can alternately stack multiple adhesion layers and defect barrier layers to form a reflector structure, thereby improving the light extraction efficiency of the chip.

[0067] Specifically, an adhesion layer and a defect barrier layer are sequentially formed on the front surface of the thinned sapphire substrate by an evaporation method.

[0068] 2. etching the defect barrier layer to form a plurality of openings;

[0069] Specifically, the defect barrier layer is etched by yellow light etching process to form a plurality of openings. The openings are etched from the surface of the defect barrier layer to the front side of the thinned sapphire substrate. If the depth of the openings does not reach the thinned sapphire substrate, the defect barrier layer will remain, affecting the quality of epitaxial growth.

[0070] The present invention increases the contact area between gallium nitride and the substrate by forming a plurality of openings on the defect barrier layer; since gallium nitride cannot grow alone on the defect barrier layer, the openings can only be filled by the lateral growth of gallium nitride. Therefore, when growing gallium nitride, the longitudinal epitaxy of gallium nitride is converted into lateral epitaxy, which can effectively reduce the dislocation density of the gallium nitride epitaxial material and effectively reduce the lattice defects.

[0071] Preferably, the openings are arranged in an array, and the openings are formed into a circle. In other embodiments of the present invention, the shape of the openings can also be a triangle, an ellipse, a square, a rectangle or a star.

[0072] It should be noted that the width of the openings and the intervals between the openings have an important influence on the formation of the GaN epitaxial layer.

[0073] Preferably, the width of the opening is 2-5 μm. If the width of the opening is less than 2 μm, the formation of GaN epitaxy will be affected; if the width of the opening is greater than 5 μm, the lattice defects of GaN epitaxy will increase.

[0074] Preferably, the interval between the openings is 2-5 μm. If the interval between the openings is greater than 5 μm, it will affect the formation of GaN epitaxy. Due to process limitations, the interval between the openings is rarely less than 2 μm.

[0075] 3. forming an adhesive layer on the back side of the thinned sapphire substrate;

[0076] Since the thickness of the thickened layer is relatively large and the bonding force between the material of the thickened layer and the material of the thinned sapphire substrate is relatively weak, the present invention bonds the thickened layer to the back side of the thinned sapphire substrate through an adhesive layer.

[0077] Specifically, the material of the bonding layer should match the material of the thickening layer. Preferably, the material of the bonding layer is Al.

[0078] The thickness of the adhesive layer is 300-1000 nm. If the thickness of the adhesive layer is less than 300 nm, the thickness is too thin and cannot play the role of bonding the thickening layer, which leads to the shedding of the thickening layer.

[0079] 4. bonding the thickened layer to the adhesive layer, wherein the thickened layer is made of a thermally conductive material having a thermal expansion coefficient that is smaller than the thermal expansion coefficient of the thinned sapphire substrate;

[0080] Since the present invention adopts a thinned sapphire substrate, the present invention needs to bond a thickening layer on the back of the thinned sapphire substrate to prevent the thinned sapphire substrate from warping. Specifically, the material of the thickening layer must meet the following requirements: (1) the thermal expansion coefficient of the material must be smaller than the thermal expansion coefficient of the thinned sapphire substrate; (2) the material has good thermal conductivity; (3) high hardness; (4) the material lattice is similar to that of the thinned sapphire substrate.

[0081] Preferably, the thickening layer is an AlN substrate or a SiC substrate. Specifically, the thermal expansion coefficient of AlN is 8.53*10-6 / K, and the thermal expansion coefficient of the sapphire substrate is 7.85*10-6 / K. Therefore, the present invention can avoid thermal expansion warping of the thinned sapphire substrate by bonding the thickening layer on the back of the thinned sapphire substrate, and AlN has good thermal conductivity and is suitable for gallium nitride epitaxial growth.

[0082] It should be noted that the thickness of the thickened layer of the present invention plus the thickness of the thinned sapphire substrate is generally equal to the thickness of the conventional sapphire substrate. Preferably, the thickness of the thickened layer is 300-500 μm. If the thickness of the thickened layer is too small, it will not prevent the thinned sapphire substrate from warping; if the thickness of the thickened layer is too large, it will affect the heat dissipation effect of the substrate.

[0083] In order to further enhance the bonding force between the thickened layer and the thinned sapphire substrate, the present invention uses a bonding machine to bond the thickened layer to the adhesive layer under a pressure of 1 to 3 tons and a temperature of 300 to 350° C. The bonding time is 30 to 90 minutes.

[0084] It should be noted that bonding pressure and temperature play an important role in the bonding effect between the thickened layer and the thinned sapphire substrate. If the bonding pressure is less than 1 ton, the pressure is too small, and the bonding force between the thinned sapphire substrate and the thickened layer is poor. If the bonding temperature is less than 300°C, the temperature is too low, and the adhesive layer is not hot enough to melt, making it difficult to bond the thinned sapphire substrate and the thickened layer. If the bonding pressure is greater than 3 tons, the pressure is too high, and the thickened layer or the thinned sapphire substrate is easily fractured.

[0085] After bonding is completed, the thickened layer is slowly cooled to reduce the stress between the thinned sapphire substrate and the thickened layer.

[0086] The invention effectively bonds the thickened layer to the back side of the sapphire composite substrate without damaging the thinned sapphire substrate by adjusting the bonding temperature and pressure.

[0087] The present invention will be further described below with specific embodiments.

[0088] Example 1

[0089] A sapphire composite substrate comprises a thinned sapphire substrate, an adhesion layer arranged on the front side of the thinned sapphire substrate, a defect barrier layer arranged on the adhesion layer, an adhesive layer arranged on the back side of the thinned sapphire substrate, and a thickening layer arranged on the adhesive layer; the thickness of the thinned sapphire substrate is 100 μm; the material of the adhesion layer is Al2O3, with a thickness of 10 nm; the material of the defect barrier layer is SiO2, with a thickness of 1000 nm; the material of the adhesive layer is Al, with a thickness of 800 nm; the material of the thickening layer is AlN, with a thickness of 450 μm;

[0090] The defect barrier layer is provided with a plurality of openings, which are etched from the surface of the defect barrier layer to the front side of the thinned sapphire substrate, with a width of 2 μm and an interval of 2 μm between the openings.

[0091] Example 2

[0092] A sapphire composite substrate comprises a thinned sapphire substrate, an adhesion layer arranged on the front side of the thinned sapphire substrate, a defect barrier layer arranged on the adhesion layer, an adhesive layer arranged on the back side of the thinned sapphire substrate, and a thickening layer arranged on the adhesive layer; the thickness of the thinned sapphire substrate is 150 μm; the material of the adhesion layer is Al2O3, with a thickness of 40 nm; the material of the defect barrier layer is SiO2, with a thickness of 1200 nm; the material of the adhesive layer is Al, with a thickness of 400 nm; the material of the thickening layer is AlN, with a thickness of 300 μm;

[0093] The defect barrier layer is provided with a plurality of openings, which are etched from the surface of the defect barrier layer to the front side of the thinned sapphire substrate, with a width of 3 μm and an interval between the openings of 3 μm.

[0094] Example 3

[0095] A sapphire composite substrate comprises a thinned sapphire substrate, an adhesion layer arranged on the front side of the thinned sapphire substrate, a defect barrier layer arranged on the adhesion layer, a bonding layer arranged on the back side of the thinned sapphire substrate, and a thickening layer arranged on the bonding layer; the thickness of the thinned sapphire substrate is 200 μm; the material of the adhesion layer is Al2O3, with a thickness of 80 nm; the material of the defect barrier layer is SiO2, with a thickness of 1500 nm; the material of the bonding layer is Al, with a thickness of 500 nm; the material of the thickening layer is AlN, with a thickness of 300 μm;

[0096] The defect barrier layer is provided with a plurality of openings, which are etched from the surface of the defect barrier layer to the front side of the thinned sapphire substrate, with a width of 5 μm and an interval of 5 μm between the openings.

[0097] Comparative Example 1

[0098] A type of sapphire with a thickness of 450μm.

[0099] Comparative Example 2

[0100] A sapphire composite substrate comprises a thinned sapphire substrate, an adhesion layer arranged on the front side of the thinned sapphire substrate, and a defect barrier layer arranged on the adhesion layer; the thickness of the thinned sapphire substrate is 150 μm; the material of the adhesion layer is Al2O3, and the thickness is 10 nm; the material of the defect barrier layer is SiO2, and the thickness is 1000 nm.

[0101] Comparative Example 3

[0102] A sapphire composite substrate comprises a thinned sapphire substrate, an adhesive layer arranged on the back of the thinned sapphire substrate, and a thickening layer arranged on the adhesive layer; the adhesive layer is made of Al with a thickness of 300nm, and the thickening layer is made of AlN with a thickness of 300μm.

[0103] The gallium nitride epitaxy with the same structure is formed on the substrates of Examples 1 to 3 and Comparative Examples 1 to 3, and is made into a size of 10*30mil. 2 Then all the chips were tested, and the results are as follows:

[0104]

[0105]

[0106] From the above results, it can be seen that Examples 1 to 3 and Comparative Example 2 form a defect barrier layer with a plurality of openings on the front side of the thinned sapphire substrate, which effectively reduces the lattice mismatch of the epitaxial layer, improves the light extraction efficiency of the chip, and reduces the light attenuation of the chip; Examples 1 to 3 and Comparative Example 3 form a thickened layer on the back side of the thinned sapphire substrate, which effectively reduces the warping of the chip.

[0107] The above disclosure is only a preferred embodiment of the present invention, which certainly cannot be used to limit the scope of the present invention. Therefore, equivalent changes made according to the claims of the present invention are still within the scope of the present invention.

Claims

1. A sapphire composite substrate, characterized in that: It includes a thinned sapphire substrate, a defect barrier layer arranged on the front side of the thinned sapphire substrate, a thickening layer for preventing the thinned sapphire substrate from bending, and a bonding layer for bonding the thickening layer to the back side of the thinned sapphire substrate; The defect barrier layer is provided with a plurality of openings, the openings are etched from the surface of the defect barrier layer to the front side of the thinned sapphire substrate, the defect barrier layer is made of a transparent non-conductive material, and the crystal lattice of the transparent non-conductive material matches the crystal lattice of the epitaxial layer; The thickened layer is made of a heat-conducting material, and the thermal expansion coefficient of the heat-conducting material is smaller than the thermal expansion coefficient of the thinned sapphire substrate; An adhesion layer is provided between the defect barrier layer and the thinned sapphire substrate; Multiple layers of adhesion layers and defect barrier layers are alternately stacked to form a reflector structure; The thickness of the defect barrier layer is 1000-1500 nm, and the thickness of the adhesion layer is 10-100 nm.

2. The sapphire composite substrate according to claim 1, characterized in that: The material of the defect barrier layer is SiO2 or Si2N4, and the material of the adhesion layer is Al2O3.

3. The sapphire composite substrate according to claim 1, characterized in that: The width of the openings is 2-5 μm, and the intervals between the openings are 2-5 μm.

4. The sapphire composite substrate according to claim 1, characterized in that: The thickening layer is an AlN substrate or a SiC substrate, and the material of the bonding layer is Al.

5. The sapphire composite substrate according to claim 4, characterized in that: The thickness of the thickening layer is 300-500 μm, and the thickness of the bonding layer is 300-1000 nm.

6. The sapphire composite substrate according to claim 1, characterized in that: The thickness of the thinned sapphire substrate is 90-200 μm.

7. A method for preparing a sapphire composite substrate, for preparing the sapphire composite substrate according to any one of claims 1 to 6, characterized in that: include: forming a defect barrier layer on the front side of the thinned sapphire substrate, the defect barrier layer being made of a transparent non-conductive material having a lattice matching that of the epitaxial layer; Etching the defect barrier layer to form a plurality of openings, wherein the openings are etched from the defect barrier layer to the front side of the thinned sapphire substrate; forming an adhesive layer on the back side of the thinned sapphire substrate; The thickened layer is bonded to the adhesive layer, the thickened layer being made of a thermally conductive material having a thermal expansion coefficient that is smaller than a thermal expansion coefficient of the thinned sapphire substrate.

8. The method for manufacturing a sapphire composite substrate according to claim 7, characterized in that: The thickened layer is bonded to the adhesive layer at a temperature of 300 to 350°C for a bonding time of 30 to 90 minutes.

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