LED epitaxial wafer and manufacturing and separating method thereof
By setting the first sacrificial layer and the U-shaped GaN layer between the sapphire substrate and the epitaxial stack, and using a combination method of laser and corrosion solution, the lossless peeling of the sapphire substrate is achieved, solving the problems of damage and non-reusability in the prior art, and improving the reliability and yield of the LED chip.
Patent Information
- Application Number
- CN202411831996.0
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-12-12
- Publication Date
- 2025-03-18
AI Technical Summary
In the prior art, when the sapphire substrate is peeled off, it is easy to cause damage to the epitaxial structure and the sapphire substrate, resulting in low reliability and low yield, and the sapphire substrate cannot be reused.
A first sacrificial layer and a U-shaped GaN layer are provided between the sapphire substrate and the epitaxial stack. The gap channel is formed by laser acting on the U-shaped GaN layer, and the first sacrificial layer is dissolved by a corrosion solution to achieve lossless peeling of the sapphire substrate.
The efficient and low-cost lossless peeling of the sapphire substrate is achieved, making the sapphire substrate reusable, avoiding damage to the epitaxial structure in the prior art, and improving the reliability and yield of the LED chip.
Smart Images
Figure CN119653938A_ABST
Abstract
Description
Technical Field
[0001] The invention belongs to the field of LEDs, and more specifically, relates to an LED epitaxial wafer and a manufacturing and separation method thereof. Background Art
[0002] LED is a PN junction electroluminescent light-emitting device. As a new generation of solid cold light source, it has the advantages of high electro-optical conversion efficiency, low energy consumption, long life, energy saving and environmental protection, high reliability, etc. It is widely used in various places such as indoor lighting, photovoltaics, medical lighting, automobile lights, display screens, etc.
[0003] According to the chip structure, LED chips can be divided into three types: upright chips, flip chips and vertical chips. Regardless of the structure of the LED chip, there is a need to peel off the sapphire substrate during the production of the LED chip. The peeling technology can be used to separate the sapphire substrate and the epitaxial layer.
[0004] Some people use grinding to separate the substrate and epitaxial material, but sapphire is very difficult to machine due to its high hardness and brittleness, which not only increases the difficulty of device processing. Currently, laser stripping is the most studied and used method. Due to the immaturity of laser stripping debugging technology, the laser acts on the entire stripping interface of the sapphire substrate during the laser stripping process, which can easily cause damage to the material surface, manifested as broken pieces, large-area scanning marks, and tearing damage in the center area, resulting in poor stripping integrity between the substrate and the epitaxial structure, which will damage the epitaxial structure and cause increased leakage rate, low yield and other problems. Moreover, grinding and laser stripping will damage the sapphire substrate and cannot be reused. Summary of the invention
[0005] In view of this, the present invention provides an LED epitaxial wafer and a method for manufacturing and separating the same, so as to solve the problem in the prior art that when peeling off the sapphire substrate, the epitaxial structure and the sapphire substrate are easily damaged, resulting in low reliability and low yield, and the sapphire substrate cannot be reused.
[0006] To achieve the above purpose, the technical solution adopted by the present invention is as follows:
[0007] An LED epitaxial wafer, characterized by comprising:
[0008] Sapphire substrate;
[0009] An epitaxial stack is provided on one side of the sapphire substrate, and a first sacrificial layer and a U-type GaN layer are provided between the sapphire substrate and the epitaxial stack, wherein the first sacrificial layer is provided on a portion of the surface of the sapphire substrate, and the U-type GaN layer covers the first sacrificial layer by being stacked on the surface of the sapphire substrate;
[0010] The epitaxial stack at least includes a first-type semiconductor layer, an active region, and a second-type semiconductor layer sequentially stacked along a first direction, wherein the first direction is perpendicular to the sapphire substrate and points from the sapphire substrate to the epitaxial stack.
[0011] Preferably, the first sacrificial layer comprises a water-soluble single crystal thin film, and the U-type GaN layer comprises a low-temperature U-type GaN layer.
[0012] Preferably, the thickness of the first sacrificial layer is 0.8-1 times the thickness of the U-type GaN layer, including the end values.
[0013] Preferably, a buffer structure is provided between the U-type GaN layer and the epitaxial stack, and the buffer structure at least comprises an Al N nucleation layer.
[0014] Preferably, a second sacrificial layer is provided between the U-type GaN layer and the buffer structure, and the second sacrificial layer is arranged on a portion of the surface of the U-type GaN layer facing away from the first sacrificial layer. The buffer structure covers the second sacrificial layer by being stacked on the surface of the U-type GaN layer, wherein the thickness of the first sacrificial layer is greater than the thickness of the second sacrificial layer.
[0015] The present invention also provides a method for preparing and separating an LED epitaxial wafer, characterized in that the preparation method comprises the following steps:
[0016] Step 1: preparing LED epitaxial wafers;
[0017] The preparation of the LED epitaxial wafer includes the following steps:
[0018] Step S1, providing a sapphire substrate;
[0019] Step S2, growing a first sacrificial layer on a portion of the surface of one side of the sapphire substrate;
[0020] Step S3, preparing a U-type GaN layer on the first sacrificial layer, wherein the U-type GaN layer covers the first sacrificial layer by being stacked on the surface of the sapphire substrate;
[0021] Step S4, growing an epitaxial stack on the U-type GaN layer, wherein the epitaxial stack at least includes a first-type semiconductor layer, an active region, and a second-type semiconductor layer sequentially stacked along a growth direction;
[0022] Step 2: separating the sapphire substrate;
[0023] The contact surface between the U-type GaN layer and the sapphire substrate is A, the contact surface between the U-type GaN layer and the side wall of the first sacrificial layer is B, and the contact surface between the U-type GaN layer and the edge region of the upper surface of the first sacrificial layer is C;
[0024] Separating the sapphire substrate includes the following steps:
[0025] Step A1, applying laser to the A, B and C positions simultaneously to form a gap channel;
[0026] Step A2: using a corrosive solution to dissolve the first sacrificial layer through the gap channel to damagelessly separate the sapphire substrate and expose the U-type GaN layer.
[0027] Preferably, the contact surface between the U-type GaN layer and the middle area of the first sacrificial layer is D, and the laser can also act on a part or all of the area at D at the same time to form the gap channel.
[0028] Preferably, the first sacrificial layer comprises a water-soluble single crystal film, and the step A2 comprises: using deionized water to dissolve the water-soluble single crystal film through the gap channel to non-destructively separate the sapphire substrate and expose the U-type GaN layer;
[0029] When forming a water-soluble single crystal film, the following process conditions are used: a magnetron sputtering process is used to grow the water-soluble single crystal film, and the process vacuum is 2.0E -4 Pa-4.0E -4 Pa, including the endpoint value; the coating temperature is 600℃-700℃, including the endpoint value; the magnetron sputtering power range is 100W-150W, including the endpoint value;
[0030] Furthermore, the U-type GaN layer includes a low-temperature U-type GaN layer, the U-type GaN layer is grown by a chemical vapor deposition process, and the growth temperature of the U-type GaN layer is 500° C.-600° C., including end values.
[0031] Preferably, the thickness of the first sacrificial layer is 0.8-1 times the thickness of the U-type GaN layer, including the end values.
[0032] Preferably, a buffer structure is provided between the U-type GaN layer and the epitaxial stack, and the buffer structure at least comprises an Al N nucleation layer.
[0033] Preferably, a second sacrificial layer is provided between the U-type GaN layer and the buffer structure, the second sacrificial layer is provided on a portion of the surface of the U-type GaN layer away from the first sacrificial layer, the buffer structure covers the second sacrificial layer by being stacked on the surface of the U-type GaN layer, wherein the thickness of the first sacrificial layer is greater than the thickness of the second sacrificial layer;
[0034] Furthermore, after the step 2, the method further includes: step 3, separating the U-type GaN layer:
[0035] Separating the U-type GaN layer includes the following steps:
[0036] Step B1, using a dry etching process to etch along the edge region of the exposed U-type GaN layer, and exposing a portion of the second sacrificial layer;
[0037] Step B2: using a corrosive solution to dissolve the second sacrificial layer to damagelessly separate the U-type GaN layer and expose the buffer structure.
[0038] Through the above technical solution, the following effects are achieved:
[0039] 1. The LED epitaxial wafer provided by the present invention has a first sacrificial layer and a U-type GaN layer between a sapphire substrate and an epitaxial stack, wherein the first sacrificial layer is arranged on a part of the surface of the sapphire substrate, and the U-type GaN layer covers the first sacrificial layer by being stacked on the surface of the sapphire substrate; based on the above arrangement, since the U-type GaN layer can absorb laser energy and can be decomposed by the laser, conditions are provided for forming a gap channel so that a corrosive solution can pass through the gap channel to dissolve the first sacrificial layer, and the sapphire substrate can be non-destructively stripped efficiently and at low cost, so that the sapphire substrate can be recycled repeatedly, and the existing stripping process can be avoided to damage the epitaxial stack and cause the leakage rate to increase, the yield is low, and other problems, thereby improving the reliability and yield of the LED chip; the U-type GaN layer can effectively alleviate the lattice mismatch between the first sacrificial layer and the epitaxial stack, and ensure that the first sacrificial layer does not react with the corrosive solution before the sapphire substrate is stripped.
[0040] 2. Furthermore, a buffer structure is provided between the U-type GaN layer and the epitaxial stack, and the buffer structure at least includes an Al N nucleation layer, which can further alleviate the lattice mismatch between the first sacrificial layer and the epitaxial stack.
[0041] 3. Furthermore, by providing a second sacrificial layer between the U-type GaN layer and the buffer structure, the LED epitaxial wafer can be made to dissolve the first sacrificial layer with a corrosive solution according to actual needs, thereby realizing lossless stripping of the U-type GaN layer; the buffer structure covers the second sacrificial layer by being stacked on the surface of the U-type GaN layer, and the buffer structure can effectively alleviate the lattice mismatch between the second sacrificial layer and the epitaxial stack, and ensure that the second sacrificial layer does not react with the corrosive solution before stripping the U-type GaN layer; wherein, the thickness of the first sacrificial layer is greater than the thickness of the second sacrificial layer, because the formation environment of the second sacrificial layer has slightly worse roughness and flatness than the formation environment of the first sacrificial layer (that is, the second sacrificial layer is formed on the buffer structure, and the first sacrificial layer is formed on the sapphire substrate, and the roughness and flatness of the surface of the buffer structure are slightly worse than the roughness and flatness of the surface of the sapphire substrate), the thickness of the second sacrificial layer is set to be thinner, which can improve the flatness of the film layer itself, maintain the flatness transmitted by the U-type GaN layer, and ensure the growth quality of the epitaxial stack.
[0042] 4. The preparation and separation method of the LED epitaxial wafer provided by the present invention comprises the following steps: firstly preparing the LED epitaxial wafer, the LED epitaxial wafer comprising a sapphire substrate and a first sacrificial layer, a U-type GaN layer and an epitaxial stack formed in sequence on the sapphire substrate, wherein the U-type GaN layer covers the first sacrificial layer by being stacked on the surface of the sapphire substrate; then applying a laser to the U-type GaN layer of the LED epitaxial wafer, because the U-type GaN layer can absorb laser energy, under the action of the laser energy, the U-type GaN layer absorbs a large amount of photon energy and decomposes to form liquid Ga and nitrogen to form a gap channel, and then using a corrosive solution to dissolve the first sacrificial layer through the gap channel, so that the sapphire substrate can be non-destructively stripped with high efficiency and low cost, so that the sapphire substrate can be recycled repeatedly, thereby saving production costs; and it can also avoid the existing stripping process from damaging the epitaxial stack and causing problems such as increased leakage rate and low yield, thereby improving the reliability and yield of the LED chip, and the process is simple and convenient to manufacture, and is easy to produce. BRIEF DESCRIPTION OF THE DRAWINGS
[0043] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the provided drawings without paying creative work.
[0044] Figure 1 A schematic diagram of the structure of an LED epitaxial wafer provided by an embodiment of the present invention;
[0045] Figure 2 A schematic diagram of another LED epitaxial wafer structure provided by an embodiment of the present invention;
[0046] Figure 3 A schematic diagram of another LED epitaxial wafer structure provided by an embodiment of the present invention;
[0047] Figures 4 to 10 A process cross-sectional view corresponding to each step of a method for preparing and separating an LED epitaxial wafer provided in an embodiment of the present invention.
[0048] Explanation of symbols in the figure:
[0049] 01. Sapphire substrate; 11. First sacrificial layer; 12. Second sacrificial layer; 21. U-type GaN layer; 22. Buffer structure; 3. Epitaxial stack; 31. First-type semiconductor layer; 32. Active region; 33. Second-type semiconductor layer; A. Contact surface between U-type GaN layer and sapphire substrate; B. Contact surface between U-type GaN layer and side wall of first sacrificial layer; C. Contact surface between U-type GaN layer and edge region of upper surface of first sacrificial layer; D. Contact surface between U-type GaN layer and middle region of first sacrificial layer. DETAILED DESCRIPTION
[0050] To make the content of the present invention clearer, the technical solutions in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.
[0051] In the following description, many specific details are set forth to facilitate a full understanding of the present application, but the present application may also be implemented in other ways different from those described herein, and those skilled in the art may make similar generalizations without violating the connotation of the present application. Therefore, the present application is not limited to the specific embodiments disclosed below.
[0052] Secondly, the present application is described in detail with reference to the schematic diagram. When describing the embodiments of the present application in detail, for the sake of convenience, the cross-sectional diagrams showing the device structure will not be partially enlarged according to the general scale, and the schematic diagrams are only examples, which should not limit the scope of protection of the present application. In addition, in actual production, the three-dimensional dimensions of length, width and depth should be included.
[0053] The present application embodiment provides an LED epitaxial wafer, such as Figure 1 As shown, the LED epitaxial wafer includes:
[0054] Sapphire substrate 01;
[0055] An epitaxial stack 3 is provided on one side of a sapphire substrate 01, and a first sacrificial layer 11 and a U-type GaN layer 21 are provided between the sapphire substrate 01 and the epitaxial stack 3, wherein the first sacrificial layer 11 is provided on a portion of the surface of the sapphire substrate 01, and the U-type GaN layer 21 covers the first sacrificial layer 11 by being stacked on the surface of the sapphire substrate 01;
[0056] The epitaxial stack 3 at least includes a first-type semiconductor layer 31 , an active region 32 and a second-type semiconductor layer 33 sequentially stacked along a first direction. The first direction is perpendicular to the sapphire substrate 01 and points from the sapphire substrate 01 to the epitaxial stack 3 .
[0057] It should be noted that the present embodiment does not limit the specific doping types of the first-type semiconductor layer 31 and the second-type semiconductor layer 33. The doping types of the first-type semiconductor layer 31 and the second-type semiconductor layer 33 are opposite. The first-type semiconductor layer 31 can be a P-type semiconductor layer or an N-type semiconductor layer. The materials of the N-type semiconductor layer and the P-type semiconductor layer can be GaN or AlGaN.
[0058] On the basis of the above embodiments, in one embodiment of the present application, the first sacrificial layer 11 includes a water-soluble single crystal thin film, and the U-type GaN layer 21 includes a low-temperature U-type GaN layer 21 .
[0059] It should be noted that the first sacrificial layer 11 of the present embodiment includes a water-soluble single crystal film, which can be dissolved by deionized water. Deionized water is obtained by removing cations and anions from water to make it nearly pure. High-purity deionized water is used to dissolve the water-soluble single crystal film, which is more environmentally friendly than other corrosive solutions.
[0060] Moreover, there is a lattice mismatch between the water-soluble single crystal film and the GaN material. In this embodiment, a low-temperature U-type GaN layer is set. The low temperature refers to that the growth temperature of the U-type GaN layer 21 is lower than the growth temperature of other film layers in the LED epitaxial wafer. The U-type GaN layer formed at low temperature is an amorphous structure, which can effectively alleviate the adverse effects of the lattice mismatch and avoid the high dislocation density caused by the lattice mismatch, thereby improving the flatness of the epitaxial wafer. The U-type GaN layer is an undoped GaN layer, which is more conducive to absorbing laser energy and facilitates the peeling of the sapphire substrate 01.
[0061] Optionally, in this embodiment, the material of the water-soluble single crystal thin film includes Sr3Al2O6 or Sr4Al2O7.
[0062] Optionally, in this embodiment, the growth temperature of the U-type GaN layer 21 is 500° C.-600° C., including end points.
[0063] On the basis of the above embodiments, in one embodiment of the present application, high-temperature annealing is performed on the low-temperature U-type GaN layer 21 , and the annealing temperature ranges from 1100° C. to 1200° C., including end points.
[0064] It should be noted that in this embodiment, the low-temperature U-type GaN layer is subjected to high-temperature annealing to transform the amorphous U-type GaN layer into a polycrystalline U-type GaN layer. Forming the polycrystalline U-type GaN layer does not affect the crystal quality of the film layer itself.
[0065] Based on the above embodiments, in one embodiment of the present application, the thickness of the first sacrificial layer 11 is 0.8-1 times the thickness of the U-type GaN layer 21, including the end value, so that the structure of the first sacrificial layer is dense and the flatness is good, and the lattice mismatch with the U-type GaN layer is reduced.
[0066] On the basis of the above-mentioned embodiments, in one embodiment of the present application, the thickness of the first sacrificial layer 11 ranges from 20 nm to 200 nm, including the end value. It is avoided that the thickness is too thin, resulting in poor compactness of the first sacrificial layer 11 and poor non-destructive stripping effect; it is avoided that the thickness is too thick, resulting in too rough surface of the first sacrificial layer 11, which affects the crystal quality of the film layer disposed on the first sacrificial layer 11.
[0067] On the basis of the above embodiments, in one embodiment of the present application, the thickness of the U-type GaN layer 21 is in the range of 25 nm to 200 nm, including end points.
[0068] It should be noted that when laser stripping is used on the sapphire substrate 01, the U-type GaN layer 21 can play a role in laser isolation and protection. The thickness range of the U-type GaN layer 21 is set to 25nm-200nm, including the end value, to avoid the thickness being too thin, which will cause the film layer set on the side of the U-type GaN layer 21 away from the sapphire substrate 01 to be damaged by the laser, and the U-type GaN layer 21 has poor density, and the lattice mismatch between the water-soluble single crystal film and the U-type GaN layer 21 causes a high dislocation density; avoid the thickness being too thick, which will reduce the flatness of the film layer itself.
[0069] Based on the above embodiments, in an embodiment of the present application, Figure 2 As shown, a buffer structure 22 is provided between the U-type GaN layer 21 and the epitaxial stack 3, and the buffer structure 22 at least includes an AlN nucleation layer.
[0070] Optionally, in this embodiment, the thickness of the buffer structure 22 ranges from 50 nm to 2000 nm, including endpoint values.
[0071] Optionally, in this embodiment, the buffer structure 22 further includes an Al N / Al N layer disposed on the surface of the Al N nucleation layer facing away from the sapphire substrate 01. x Ga 1-x The N superlattice structure can further alleviate the lattice mismatch between the first sacrificial layer 11 and the epitaxial stack 3 .
[0072] Optionally, in this embodiment, Al N / Al x Ga 1-xN superlattice structure, wherein x is between 0.65 and 0.75 and the value of x gradually increases along the first direction, can reduce the accumulation of stress and strain in the epitaxial stack 3, help to achieve better crystal quality and surface morphology, thereby improving the crystallization quality of the epitaxial stack 3.
[0073] Optionally, in this embodiment, the thickness of the Al N nucleation layer ranges from 50 nm to 500 nm, including the end value, Al N / Al x Ga 1-x The total thickness of the N superlattice structure ranges from 100 nm to 1500 nm, both inclusive.
[0074] Based on the above embodiments, in an embodiment of the present application, Figure 3 As shown, a second sacrificial layer 12 is provided between the U-type GaN layer 21 and the buffer structure 22. The second sacrificial layer 12 is provided on a portion of the surface of the U-type GaN layer 21 facing away from the first sacrificial layer 11. The buffer structure 22 covers the second sacrificial layer 12 by being stacked on the surface of the U-type GaN layer 21, wherein the thickness of the first sacrificial layer 11 is greater than the thickness of the second sacrificial layer 12.
[0075] Optionally, in this embodiment, the thickness of the second sacrificial layer 12 is 0.05-0.2 times the thickness of the buffer structure 22, including the endpoint values; so that the second sacrificial layer 12 has a dense structure and good flatness, reduces the lattice mismatch with the buffer structure 22, and thereby improves the crystal quality of the epitaxial stack 3.
[0076] Optionally, in this embodiment, the thickness of the second sacrificial layer 12 ranges from 10 nm to 100 nm, including the end value. Avoid being too thin, which results in poor compactness of the second sacrificial layer 12 and poor lossless separation effect; avoid being too thick, which results in the surface of the second sacrificial layer 12 being too rough and affecting the crystal quality of the epitaxial stack 3.
[0077] Optionally, in this embodiment, the second sacrificial layer 12 includes a water-soluble single crystal film.
[0078] The embodiment of the present application also provides a method for preparing and separating an LED epitaxial wafer, and the method for preparing and separating an LED epitaxial wafer comprises the following steps:
[0079] Step 1: preparing LED epitaxial wafers;
[0080] The preparation of LED epitaxial wafers includes the following steps:
[0081] Step S1: Figure 4 As shown, a sapphire substrate 01 is provided;
[0082] Optionally, in this embodiment, before the sapphire substrate 01 is placed in the reaction chamber, the sapphire substrate 01 may be organically cleaned to remove surface dirt.
[0083] Step S2: Figure 5 As shown, a first sacrificial layer 11 is grown on a portion of the surface of one side of the sapphire substrate 01;
[0084] Step S3: Figure 6 As shown, a U-type GaN layer 21 is prepared on the first sacrificial layer 11, and the U-type GaN layer 21 covers the first sacrificial layer 11 by stacking on the surface of the sapphire substrate 01;
[0085] Step S4: Figure 7 As shown, an epitaxial stack 3 is grown on the U-type GaN layer 21 , and the epitaxial stack 3 at least includes a first-type semiconductor layer 31 , an active region 32 , and a second-type semiconductor layer 33 sequentially stacked along a growth direction.
[0086] Step 2: Separate the sapphire substrate 01;
[0087] Among them, continue as Figure 7 As shown, the contact surface between the U-type GaN layer 21 and the sapphire substrate 01 is A, the contact surface between the U-type GaN layer 21 and the side wall of the first sacrificial layer 11 is B, and the contact surface between the U-type GaN layer 21 and the edge region of the upper surface of the first sacrificial layer 11 is C;
[0088] Separating the sapphire substrate 01 includes the following steps:
[0089] Step A1, applying laser to A, B and C simultaneously to form a gap channel;
[0090] Step A2: Figure 8 As shown, a corrosive solution is used to dissolve the first sacrificial layer 11 through the gap channel to separate the sapphire substrate 01 without damage and expose the U-type GaN layer 21 .
[0091] It should be noted that the present embodiment does not limit the specific doping types of the first-type semiconductor layer 31 and the second-type semiconductor layer 33. The doping types of the first-type semiconductor layer 31 and the second-type semiconductor layer 33 are opposite. The first-type semiconductor layer 31 can be a P-type semiconductor layer or an N-type semiconductor layer. The materials of the N-type semiconductor layer and the P-type semiconductor layer can be GaN or AlGaN.
[0092] It should also be noted that the raised portion of the U-type GaN layer 21 exposed in this embodiment is in the edge region, and the edge region of the LED epitaxial wafer is not used for LED chip arrangement, and has no effect on the formation of LED chips. Optionally, in this embodiment, an etching process is used to remove the raised portion of the edge region of the U-type GaN layer 21.
[0093] Based on the above embodiments, in one embodiment of the present application, refer to Figure 7 As shown, the contact surface between the U-type GaN layer 21 and the middle area of the first sacrificial layer 11 is D, and the laser can also act on part or all of the area at D at the same time to form a gap channel. The dissolution rate of the etching solution can be accelerated, saving process time.
[0094] On the basis of the above embodiments, in one embodiment of the present application, the first sacrificial layer 11 includes a water-soluble single crystal film, and step A2 includes: using deionized water to dissolve the water-soluble single crystal film through the gap channel to non-destructively separate the sapphire substrate 01 and expose the U-type GaN layer 21;
[0095] When forming a water-soluble single crystal film, the following process conditions can be used: a magnetron sputtering process is used to grow a water-soluble single crystal film, and the process vacuum is 2.0E -4 Pa-4.0E -4 Pa, including the endpoint value; the coating temperature is 600℃-700℃, including the endpoint value; the magnetron sputtering power range is 100W-150W, including the endpoint value;
[0096] Furthermore, the U-type GaN layer 21 includes a low-temperature U-type GaN layer 21 . The U-type GaN layer 21 is grown by a chemical vapor deposition process. The growth temperature of the U-type GaN layer 21 is 500° C.-600° C., including end values.
[0097] It should be noted that the first sacrificial layer 11 of the present embodiment includes a water-soluble single crystal film, which can be dissolved by deionized water. Deionized water is obtained by removing cations and anions from water to make it nearly pure. High-purity deionized water is used to dissolve the water-soluble single crystal film, which is more environmentally friendly than other corrosive solutions.
[0098] Moreover, there is a lattice mismatch between the water-soluble single crystal film and the GaN material. In this embodiment, a low-temperature U-type GaN layer is set. The low temperature refers to that the growth temperature of the U-type GaN layer 21 is lower than the growth temperature of other film layers in the LED epitaxial wafer. The U-type GaN layer formed at low temperature is an amorphous structure, which can effectively alleviate the adverse effects of the lattice mismatch and avoid the high dislocation density caused by the lattice mismatch, thereby improving the flatness of the epitaxial wafer. The U-type GaN layer is an undoped GaN layer, which is more conducive to absorbing laser energy and facilitates the peeling of the sapphire substrate 01.
[0099] It should also be noted that, in this embodiment, a magnetron sputtering process is used to grow a water-soluble single crystal film to form a water-soluble single crystal film with a dense structure and good flatness; a chemical vapor deposition process is used to grow the U-type GaN layer 21. Compared with physical vapor deposition, chemical vapor deposition has good wrapping properties and can enhance the coating effect of the U-type GaN layer 21 on the exposed surface of the first sacrificial layer 11.
[0100] Optionally, in this embodiment, the material of the water-soluble single crystal thin film includes Sr3Al2O6 or Sr4Al2O7.
[0101] On the basis of the above embodiments, in one embodiment of the present application, high-temperature annealing is performed on the low-temperature U-type GaN layer 21 , and the annealing temperature ranges from 1100° C. to 1200° C., including end points.
[0102] It should be noted that in this embodiment, the low-temperature U-type GaN layer is subjected to high-temperature annealing to transform the amorphous U-type GaN layer into a polycrystalline U-type GaN layer. Forming the polycrystalline U-type GaN layer does not affect the crystal quality of the film layer itself.
[0103] Based on the above embodiments, in one embodiment of the present application, the thickness of the first sacrificial layer 11 is 0.8-1 times the thickness of the U-type GaN layer 21, including the end value, so that the structure of the first sacrificial layer is dense and the flatness is good, and the lattice mismatch with the U-type GaN layer is reduced.
[0104] On the basis of the above-mentioned embodiments, in one embodiment of the present application, the thickness of the first sacrificial layer 11 ranges from 20 nm to 200 nm, including the end value. It is avoided that the thickness is too thin, resulting in poor compactness of the first sacrificial layer 11 and poor non-destructive stripping effect; it is avoided that the thickness is too thick, resulting in too rough surface of the first sacrificial layer 11 and affecting the crystal quality of the U-type GaN layer 21.
[0105] On the basis of the above embodiments, in one embodiment of the present application, the thickness of the U-type GaN layer 21 is in the range of 25 nm to 200 nm, including end points.
[0106] It should be noted that when laser stripping is used on the sapphire substrate 01, the U-type GaN layer 21 can play a role in laser isolation and protection. The thickness range of the U-type GaN layer 21 is set to 25nm-200nm, including the end value, to avoid the thickness being too thin, which will cause the film layer set on the side of the U-type GaN layer 21 away from the sapphire substrate 01 to be damaged by the laser, and the U-type GaN layer 21 has poor density, and the lattice mismatch between the water-soluble single crystal film and the U-type GaN layer 21 causes a high dislocation density; avoid the thickness being too thick, which will reduce the flatness of the film layer itself.
[0107] Based on the above embodiments, in one embodiment of the present application, refer to Figure 2 As shown, a buffer structure 22 is provided between the U-type GaN layer 21 and the epitaxial stack 3, and the buffer structure 22 at least includes an AlN nucleation layer.
[0108] Optionally, in this embodiment, the thickness of the buffer structure 22 ranges from 50 nm to 2000 nm, including endpoint values.
[0109] Optionally, in this embodiment, the buffer structure 22 further includes an Al N / Al N layer disposed on the surface of the Al N nucleation layer facing away from the sapphire substrate 01. x Ga 1-x The N superlattice structure can further alleviate the lattice mismatch between the first sacrificial layer 11 and the epitaxial stack 3 .
[0110] Optionally, in this embodiment, Al N / Al x Ga 1-x N superlattice structure, wherein x is between 0.65 and 0.75 and the value of x gradually increases along the growth direction, can reduce the accumulation of stress and strain in the epitaxial stack 3, help to achieve better crystal quality and surface morphology, thereby improving the crystallization quality of the epitaxial stack 3.
[0111] Optionally, in this embodiment, the thickness of the Al N nucleation layer ranges from 50 nm to 500 nm, including the end value, Al N / Al x Ga 1-x The total thickness of the N superlattice structure ranges from 100 nm to 1500 nm, both inclusive.
[0112] Based on the above embodiments, in one embodiment of the present application, refer to Figure 3 As shown, a second sacrificial layer 12 is provided between the U-type GaN layer 21 and the buffer structure 22, the second sacrificial layer 12 is provided on a portion of the surface of the U-type GaN layer 21 away from the first sacrificial layer 11, and the buffer structure 22 covers the second sacrificial layer 12 by being stacked on the surface of the U-type GaN layer 21, wherein the thickness of the first sacrificial layer 11 is greater than the thickness of the second sacrificial layer 12;
[0113] Furthermore, after step 2, the method further includes: step 3, separating the U-type GaN layer 21:
[0114] Separating the U-type GaN layer 21 includes the following steps:
[0115] Step B1: Fig. 9 As shown, a dry etching process is used to etch along the edge region of the exposed U-type GaN layer 21, and a portion of the second sacrificial layer 12 is exposed;
[0116] Step B2: Fig.10As shown, the second sacrificial layer 12 is dissolved by a corrosive solution to separate the U-type GaN layer 21 without damage, thereby exposing the buffer structure 22 .
[0117] It should be noted that the second sacrificial layer 12 of this embodiment can enhance the laser isolation and protection effect when the sapphire substrate 01 is laser stripped to avoid damaging the epitaxial stack 3. In addition, the buffer structure 22 exposed in this embodiment has a smooth surface to increase the LED light extraction efficiency.
[0118] Optionally, in this embodiment, the thickness of the second sacrificial layer 12 is 0.05-0.2 times the thickness of the buffer structure 22, including the endpoint values; so that the second sacrificial layer 12 has a dense structure and good flatness, reduces the lattice mismatch with the buffer structure 22, and thereby improves the crystal quality of the epitaxial stack 3.
[0119] Optionally, in this embodiment, the thickness of the second sacrificial layer 12 ranges from 10 nm to 100 nm, including the end value. Avoid being too thin, which results in poor compactness of the second sacrificial layer 12 and poor lossless separation effect; avoid being too thick, which results in the surface of the second sacrificial layer 12 being too rough and affecting the crystal quality of the epitaxial stack 3.
[0120] On the basis of the above embodiments, in one embodiment of the present application, the second sacrificial layer 12 includes a water-soluble single crystal film, and step B2 includes: using deionized water to dissolve the second sacrificial layer 12 to separate the U-type GaN layer 21 without damage.
[0121] In summary, through the above technical solution, the following effects are achieved:
[0122] 1. The LED epitaxial wafer provided in this embodiment has a first sacrificial layer and a U-type GaN layer between a sapphire substrate and an epitaxial stack, wherein the first sacrificial layer is arranged on a portion of the surface of the sapphire substrate, and the U-type GaN layer covers the first sacrificial layer by being stacked on the surface of the sapphire substrate. Based on the above arrangement, since the U-type GaN layer can absorb laser energy and can be decomposed by the laser, conditions are provided for forming a gap channel so that the corrosive solution can pass through the gap channel to dissolve the first sacrificial layer, and the sapphire substrate can be non-destructively stripped efficiently and at low cost, so that the sapphire substrate can be recycled repeatedly, and the existing stripping process can be avoided to damage the epitaxial stack and cause problems such as increased leakage rate and low yield, thereby improving the reliability and yield of the LED chip. The U-type GaN layer can effectively alleviate the lattice mismatch between the first sacrificial layer and the epitaxial stack, and ensure that the first sacrificial layer does not react with the corrosive solution before stripping the sapphire substrate.
[0123] 2. Furthermore, a buffer structure is provided between the U-type GaN layer and the epitaxial stack, and the buffer structure at least includes an Al N nucleation layer, which can further alleviate the lattice mismatch between the first sacrificial layer and the epitaxial stack.
[0124] 3. Furthermore, by providing a second sacrificial layer between the U-type GaN layer and the buffer structure, the LED epitaxial wafer can be made to dissolve the first sacrificial layer with a corrosive solution according to actual needs, thereby realizing lossless stripping of the U-type GaN layer; the buffer structure covers the second sacrificial layer by being stacked on the surface of the U-type GaN layer, and the buffer structure can effectively alleviate the lattice mismatch between the second sacrificial layer and the epitaxial stack, and ensure that the second sacrificial layer does not react with the corrosive solution before stripping the U-type GaN layer; wherein, the thickness of the first sacrificial layer is greater than the thickness of the second sacrificial layer, because the formation environment of the second sacrificial layer has slightly worse roughness and flatness than the formation environment of the first sacrificial layer (that is, the second sacrificial layer is formed on the buffer structure, and the first sacrificial layer is formed on the sapphire substrate, and the roughness and flatness of the surface of the buffer structure are slightly worse than the roughness and flatness of the surface of the sapphire substrate), the thickness of the second sacrificial layer is set to be thinner, which can improve the flatness of the film layer itself, maintain the flatness transmitted by the U-type GaN layer, and ensure the growth quality of the epitaxial stack.
[0125] 4. The preparation and separation method of the LED epitaxial wafer provided in this embodiment first prepares the LED epitaxial wafer, the LED epitaxial wafer includes a sapphire substrate and a first sacrificial layer, a U-type GaN layer and an epitaxial stack formed in sequence on the sapphire substrate, the U-type GaN layer covers the first sacrificial layer by being stacked on the surface of the sapphire substrate; then a laser is applied to the U-type GaN layer of the LED epitaxial wafer, because the U-type GaN layer can absorb laser energy, under the action of the laser energy, the U-type GaN layer absorbs a large amount of photon energy and decomposes to form liquid Ga and nitrogen to form a gap channel, and then a corrosive solution is used to dissolve the first sacrificial layer through the gap channel, so that the sapphire substrate can be stripped non-destructively with high efficiency and low cost, so that the sapphire substrate can be recycled repeatedly, saving production costs; it can also avoid the existing stripping process from damaging the epitaxial stack and causing problems such as increased leakage rate and low yield, thereby improving the reliability and yield of the LED chip, and the process is simple and convenient to manufacture, and is easy to produce.
[0126] Those skilled in the art should understand that, in the disclosure of the present invention, the terms "horizontal", "vertical", "upper", "lower", etc., indicating the orientation or position relationship are based on the orientation or position relationship shown in the drawings, which are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation. Therefore, the above terms should not be understood as limiting the present invention.
[0127] It should be noted that the various embodiments in this specification are described in a progressive manner, and each embodiment focuses on the differences from other embodiments. The same or similar parts between the various embodiments can be referenced to each other.
[0128] The above description of the disclosed embodiments enables one skilled in the art to implement or use the present invention. Various modifications to these embodiments will be apparent to one skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to the embodiments shown herein, but rather to the widest scope consistent with the principles and novel features disclosed herein.
Claims
1. An LED epitaxial wafer, characterized in that: include: Sapphire substrate; An epitaxial stack is provided on one side of the sapphire substrate, and a first sacrificial layer and a U-type GaN layer are provided between the sapphire substrate and the epitaxial stack, wherein the first sacrificial layer is provided on a portion of the surface of the sapphire substrate, and the U-type GaN layer covers the first sacrificial layer by being stacked on the surface of the sapphire substrate; The epitaxial stack at least includes a first-type semiconductor layer, an active region, and a second-type semiconductor layer sequentially stacked along a first direction, wherein the first direction is perpendicular to the sapphire substrate and points from the sapphire substrate to the epitaxial stack.
2. The LED epitaxial wafer according to claim 1, characterized in that: The first sacrificial layer includes a water-soluble single crystal thin film, and the U-type GaN layer includes a low-temperature U-type GaN layer.
3. The LED epitaxial wafer according to claim 1, characterized in that: The thickness of the first sacrificial layer is 0.8-1 times the thickness of the U-type GaN layer, including the end values.
4. The LED epitaxial wafer according to claim 1, characterized in that: A buffer structure is provided between the U-type GaN layer and the epitaxial stack, and the buffer structure at least comprises an AlN nucleation layer.
5. The LED epitaxial wafer according to claim 4, characterized in that: A second sacrificial layer is provided between the U-type GaN layer and the buffer structure, and the second sacrificial layer is provided on a portion of the surface of the U-type GaN layer facing away from the first sacrificial layer. The buffer structure covers the second sacrificial layer by being stacked on the surface of the U-type GaN layer, wherein the thickness of the first sacrificial layer is greater than the thickness of the second sacrificial layer.
6. A method for preparing and separating LED epitaxial wafers, characterized in that: The production method comprises the following steps: Step 1: preparing LED epitaxial wafers; The preparation of the LED epitaxial wafer includes the following steps: Step S1, providing a sapphire substrate; Step S2, growing a first sacrificial layer on a portion of the surface of one side of the sapphire substrate; Step S3, preparing a U-type GaN layer on the first sacrificial layer, wherein the U-type GaN layer covers the first sacrificial layer by being stacked on the surface of the sapphire substrate; Step S4, growing an epitaxial stack on the U-type GaN layer, wherein the epitaxial stack at least includes a first-type semiconductor layer, an active region, and a second-type semiconductor layer sequentially stacked along a growth direction; Step 2: separating the sapphire substrate; The contact surface between the U-type GaN layer and the sapphire substrate is A, the contact surface between the U-type GaN layer and the side wall of the first sacrificial layer is B, and the contact surface between the U-type GaN layer and the edge region of the upper surface of the first sacrificial layer is C; Separating the sapphire substrate includes the following steps: Step A1, applying laser to the A, B and C positions simultaneously to form a gap channel; Step A2: using a corrosive solution to dissolve the first sacrificial layer through the gap channel to damagelessly separate the sapphire substrate and expose the U-type GaN layer.
7. The method for preparing and separating LED epitaxial wafers according to claim 6, characterized in that: The contact surface between the U-type GaN layer and the middle area of the first sacrificial layer is D, and the laser can also act on a part of the area or the whole area at D at the same time to form the gap channel.
8. The method for preparing and separating LED epitaxial wafers according to claim 6, characterized in that: The first sacrificial layer includes a water-soluble single crystal film, and the step A2 includes: using deionized water to dissolve the water-soluble single crystal film through the gap channel to non-destructively separate the sapphire substrate and expose the U-type GaN layer; When forming a water-soluble single crystal film, the following process conditions are used: a magnetron sputtering process is used to grow the water-soluble single crystal film, and the process vacuum is 2.0E -4 Pa-4.0E -4 Pa, including the endpoint value; the coating temperature is 600℃-700℃, including the endpoint value; the magnetron sputtering power range is 100W-150W, including the endpoint value; Furthermore, the U-type GaN layer includes a low-temperature U-type GaN layer, the U-type GaN layer is grown by a chemical vapor deposition process, and the growth temperature of the U-type GaN layer is 500° C.-600° C., including end values.
9. The method for preparing and separating LED epitaxial wafers according to claim 6, characterized in that: The thickness of the first sacrificial layer is 0.8-1 times the thickness of the U-type GaN layer, including the end values.
10. The method for preparing and separating LED epitaxial wafers according to claim 6, characterized in that: A buffer structure is provided between the U-type GaN layer and the epitaxial stack, and the buffer structure at least comprises an AlN nucleation layer.
11. The method for preparing and separating LED epitaxial wafers according to claim 10, characterized in that: A second sacrificial layer is provided between the U-type GaN layer and the buffer structure, the second sacrificial layer is provided on a portion of the surface of the U-type GaN layer away from the first sacrificial layer, the buffer structure covers the second sacrificial layer by being stacked on the surface of the U-type GaN layer, wherein the thickness of the first sacrificial layer is greater than the thickness of the second sacrificial layer; Furthermore, after the step 2, the method further includes: step 3, separating the U-type GaN layer: Separating the U-type GaN layer includes the following steps: Step B1, using a dry etching process to etch along the edge region of the exposed U-type GaN layer, and exposing a portion of the second sacrificial layer; Step B2: using a corrosive solution to dissolve the second sacrificial layer to damagelessly separate the U-type GaN layer and expose the buffer structure.