Low thermal resistance LED chip and preparation method and separation method thereof

Abstract

The application provides a low-thermal-resistance LED chip, a preparation method and a separation method thereof, and a composite substrate, wherein the composite substrate comprises a first substrate, a first bonding layer and a second substrate which are stacked in sequence along a first direction; an epitaxial stack is bonded to a side surface of the second substrate away from the first bonding layer through the second bonding layer; and the second bonding layer and the second substrate have conductivity. Thus, the high thermal conductivity of the second substrate solves the problem of thermal resistance of the LED chip; meanwhile, the temporary support of the composite substrate enhances the strength of the LED wafer, avoids the warping and fragmentation problems in the preparation process; meanwhile, the temporary support of the composite substrate can eliminate the grinding process, ensures the consistency of the thickness of the LED chip, and saves the cost. The application is especially suitable for the LED chip with high current density.

Description

Technical Field

[0001] This invention relates to the field of light-emitting diodes, and more particularly to a low thermal resistance LED chip and its preparation and separation methods. Background Technology

[0002] With the rapid development of LED technology and the gradual improvement of LED luminous efficacy, LED applications are becoming increasingly widespread, and people are paying more and more attention to the development prospects of LEDs in displays. An LED chip's function is to convert electrical energy into light energy. Specifically, it includes an epitaxial light-emitting structure and N-type and P-type electrodes respectively disposed on the epitaxial light-emitting structure. The epitaxial light-emitting structure includes a P-type semiconductor layer, an N-type semiconductor layer, and an active layer located between the N-type and P-type semiconductor layers. When current flows through the LED chip, holes in the P-type semiconductor and electrons in the N-type semiconductor move towards the active layer and recombine there, causing the LED chip to emit light.

[0003] Epitaxial light-emitting structures are multilayer semiconductor structures grown on a substrate. This substrate is typically GaAs, Si, Al2O3, or SiC, and the semiconductor layers are usually AlGaInP or AlInGaN. At lower current densities, the epitaxial light-emitting structure releases less heat during operation, and generally, upright or flip-chip structures are used without removing the growth substrate. As current density increases, the heat generated per unit area increases, and the thermal conductivity and thickness of the growth substrate directly affect the chip's heat dissipation. Therefore, for high-current-density chips, it is usually necessary to produce a substrate that is as thin as possible, or even to transfer the epitaxial light-emitting structure from the growth substrate to a substrate with high thermal conductivity by replacing the substrate, in order to reduce the overall thermal resistance of the chip.

[0004] However, for applications using high thermal conductivity substrates, in addition to high thermal conductivity, the substrate usually also needs to possess properties that match the chip manufacturing process, such as chemical stability, a certain degree of support rigidity, ease of processing, and resistance to deformation / cracks. However, in reality, materials possessing all of these properties are rare. For example, commonly used silicon substrates are chemically stable and possess a certain degree of rigidity, but they are prone to cracking during processing, especially after thinning. Metal substrates are generally not prone to cracking, but their rigidity is insufficient; thinner substrates are prone to warping and deformation, affecting the manufacturing process.

[0005] In view of this, in order to overcome the above-mentioned defects of existing LED chips, the inventor has specially designed a low thermal resistance LED chip and its preparation and separation methods, which leads to this invention. Summary of the Invention

[0006] The purpose of this invention is to provide a low thermal resistance LED chip and its preparation and separation methods to solve the problems of high thermal resistance of LED chips and warping and breakage of their supporting substrates.

[0007] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0008] A low thermal resistance LED chip, comprising:

[0009] A composite substrate, the composite substrate comprising a first substrate, a first bonding layer and a second substrate stacked sequentially along a first direction;

[0010] A plurality of sub-epitaxial stack units isolated from each other by dicing channels are formed on the surface of the second substrate away from the first bonding layer by bonding through a second bonding layer; and the dicing channels expose the first substrate; each sub-epitaxial stack includes at least a second type semiconductor layer, an active region and a first type semiconductor layer stacked sequentially along the first direction; the first direction is perpendicular to the composite substrate and points from the composite substrate to the epitaxial stack;

[0011] The first contact electrode is disposed on the surface of the first type semiconductor layer away from the active region.

[0012] Preferably, the second bonding layer and the second substrate are conductive.

[0013] Preferably, the melting point of the second bonding layer is higher than that of the first bonding layer.

[0014] Preferably, the first bonding layer is conductive.

[0015] Preferably, the temperature required to peel off the first substrate is between the melting point of the first bonding layer and the melting point of the second bonding layer.

[0016] Preferably, the second bonding layer includes at least one of an ohmic contact layer and a metal reflective layer.

[0017] Preferably, the second bonding layer comprises an alloy formed from one or at least two of Au, In, Ni, Sn, Ag, and Cu.

[0018] The present invention also provides a method for fabricating a low thermal resistance LED chip, the method comprising the following steps:

[0019] S01, Provide a growth substrate;

[0020] S02. Growing an epitaxial stack, wherein the epitaxial stack comprises a first type semiconductor layer, an active layer, and a second type semiconductor layer sequentially stacked on the surface of the growth substrate;

[0021] S03. A composite substrate is provided, the composite substrate comprising a first substrate, a first bonding layer and a second substrate stacked sequentially along a growth direction, wherein the first bonding layer and the second substrate are conductive;

[0022] S04. A second bonding layer is formed on the surface of the epitaxial stack, wherein the second bonding layer is conductive;

[0023] S05. The composite substrate is bonded to the surface of the epitaxial stack via the second bonding layer;

[0024] S06. Peel off the growth substrate;

[0025] S07. By etching the epitaxial stack, a plurality of sub-epitaxy stack units isolated from each other by trenches are formed;

[0026] S08. Deposit a first contact electrode on the surface of each of the sub-epipolar stacks facing away from the composite substrate;

[0027] S09. Cut along each of the grooves to the surface of the first substrate, thereby forming a plurality of LED light-emitting units that are isolated from each other by the cut channels.

[0028] The present invention also provides a separation method for separating the LED light-emitting units prepared above, the separation method comprising:

[0029] The first substrate is peeled off, leaving the first bonding layer on the bottom surface of each LED light-emitting unit.

[0030] Preferably, the first substrate is peeled off by heating, etching, ultrasound, laser, or light irradiation.

[0031] Preferably, when the first substrate is peeled off by heating, the peeling temperature of the first substrate is between the melting point of the first bonding layer and the melting point of the second bonding layer.

[0032] This invention also provides another method for fabricating a low thermal resistance LED chip, the method comprising the following steps:

[0033] A01. Provide a growth substrate;

[0034] A02. Growing an epitaxial stack, wherein the epitaxial stack comprises a first type semiconductor layer, an active layer, and a second type semiconductor layer sequentially stacked on the surface of the growth substrate;

[0035] A03. A composite substrate is provided, the composite substrate comprising a first substrate, a first bonding layer and a second substrate stacked sequentially along a growth direction, wherein the second substrate is conductive;

[0036] A04. A second bonding layer is formed on the surface of the epitaxial stack, wherein the second bonding layer is conductive;

[0037] A05. The composite substrate is bonded to the surface of the epitaxial stack via the second bonding layer;

[0038] A06. Peel off the growth substrate;

[0039] A07. By etching the epitaxial stack, a plurality of sub-epitaxy stack units isolated from each other by trenches are formed;

[0040] A08. Deposit a first contact electrode on the surface of each of the sub-epipolar stacks on the side opposite to the composite substrate;

[0041] A09. Cut along each of the grooves to the surface of the first substrate, thereby forming a plurality of LED light-emitting units that are isolated from each other by the cut channels.

[0042] The present invention also provides another separation method for separating the LED light-emitting units prepared above, the separation method comprising:

[0043] The first substrate and the first bonding layer are stripped away, so that the second substrate serves as another contact electrode plate for each of the LED light-emitting units.

[0044] Preferably, the first substrate and the first bonding layer are peeled off by heating, etching, ultrasound, laser, or light irradiation.

[0045] Preferably, when the first substrate and the first bonding layer are peeled off by heating, the peeling temperature of both is lower than the melting point of the second bonding layer.

[0046] As can be seen from the above technical solution, the low thermal resistance LED chip and its fabrication method provided by the present invention provide a composite substrate, the composite substrate comprising a first substrate, a first bonding layer, and a second substrate stacked sequentially along a first direction; thereby, the epitaxial stack is formed on the side surface of the second substrate opposite to the first bonding layer by bonding through the second bonding layer. Furthermore, the second bonding layer and the second substrate are conductive. Thus, the high thermal conductivity of the second substrate solves the thermal resistance problem of the LED chip; simultaneously, the temporary support of the composite substrate enhances the strength of the LED chip, avoiding warping and breakage problems during fabrication; furthermore, the temporary support of the composite substrate eliminates the need for a polishing process, ensuring the consistency of the LED chip thickness and saving costs. This is particularly suitable for LED chips with high current density.

[0047] Based on this, subsequent separation methods can be used to obtain independent LED light-emitting units by peeling off the first substrate while retaining the first bonding layer on the bottom surface of each LED light-emitting unit; or by peeling off the first substrate and the first bonding layer, leaving the second substrate as another contact electrode plate for each LED light-emitting unit, thus obtaining independent LED light-emitting units. This separation method is flexible, simple, and easy to implement, and can reduce damage to the LED chip. Attached Figure Description

[0048] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the provided drawings without creative effort.

[0049] Figure 1 This is a schematic diagram of the low thermal resistance LED chip provided in Embodiments 1 and 2 of the present invention;

[0050] Figures 2.1 to 2.9 This is a schematic diagram of the structure corresponding to the steps of the method for manufacturing a low thermal resistance LED chip provided in Embodiment 1 of the present invention.

[0051] Figure 3 This is a schematic diagram of the structure corresponding to the separation method provided in Embodiment 1 of the present invention;

[0052] Figure 4 This is a schematic diagram of the structure corresponding to the separation method provided in Embodiment 2 of the present invention;

[0053] Figure 5 This is a schematic diagram of the epitaxial stack structure provided in an embodiment of the present invention;

[0054] Symbols in the figure: 1. Growth substrate, 2. Epitaxial stack, 2.1. Type I semiconductor layer, 2.2. Active region, 2.3. Type II semiconductor layer, 3. Second bonding layer, 4. Trench, 5. First contact electrode, 6. Cutting track, 10. Composite substrate, 11. First substrate, 12. First bonding layer, 13. Second substrate. Detailed Implementation

[0055] To make the content of this invention clearer, the following description, in conjunction with the accompanying drawings, further illustrates the invention. This invention is not limited to this specific embodiment. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without inventive effort are within the scope of protection of this invention.

[0056] Example 1

[0057] like Figure 1 As shown, a low thermal resistance LED chip includes:

[0058] A composite substrate 10, the composite substrate 10 comprising a first substrate 11, a first bonding layer 12 and a second substrate 13 stacked sequentially along a first direction;

[0059] Several sub-epitaxial stack 2 units, isolated from each other by dicing channels 6, are formed on the surface of the second substrate 13 opposite to the first bonding layer 12 by bonding through a second bonding layer 3; and the dicing channels 6 expose the first substrate 11; as shown Figure 5 As shown, each of the sub-epitaxial stacks 2 includes at least a second type semiconductor layer 2.3, an active region 2.2, and a first type semiconductor layer 2.1 stacked sequentially along the first direction; the first direction is perpendicular to the composite substrate 10 and extends from the composite substrate 10 to the epitaxial stack 2;

[0060] The first contact electrode 5 is disposed on the surface of the first semiconductor layer 2.1 on the side opposite to the active region 2.2.

[0061] In this embodiment of the invention, the second bonding layer 3 and the second substrate 13 are conductive.

[0062] In this embodiment of the invention, the melting point of the second bonding layer 3 is higher than that of the first bonding layer 12.

[0063] In this embodiment of the invention, the first bonding layer 12 is conductive.

[0064] In this embodiment of the invention, the temperature required to peel off the first substrate 11 is between the melting point of the first bonding layer 12 and the melting point of the second bonding layer 3.

[0065] In this embodiment of the invention, the second bonding layer 3 includes at least one of an ohmic contact layer and a metal reflective layer.

[0066] In this embodiment of the invention, the second bonding layer 3 comprises an alloy formed from one or at least two of Au, In, Ni, Sn, Ag, and Cu.

[0067] It is worth mentioning that the type of composite substrate 10 is not limited in the LED chip of this embodiment, as long as the first bonding layer 12 and the second substrate 13 are conductive. For example, the second substrate 13 includes a metal substrate. The material of the first bonding layer 12 can be one or an alloy of at least two metals selected from Au, In, Ni, Sn, Ag, and Cu. This embodiment does not limit this.

[0068] In addition, the materials of the second type semiconductor layer 2.3, the active region 2.2 and the first type semiconductor layer 2.1 of the epitaxial stack 2 are not limited in the LED chip of this embodiment. For example, the first type semiconductor layer 2.1 can be, but is not limited to, an N-type gallium nitride layer, and correspondingly, the second type semiconductor layer 2.3 can be, but is not limited to, a P-type gallium nitride layer.

[0069] This invention also provides a method for fabricating a low thermal resistance LED chip, the method comprising the following steps:

[0070] S01, such as Figure 2.1 As shown, a growth substrate 1 is provided;

[0071] S02, such as Figure 2.2 As shown, an epitaxial stack 2 is grown, which includes a first type semiconductor layer 2.1, an active layer, and a second type semiconductor layer 2.3 sequentially stacked on the surface of the growth substrate 1;

[0072] S03, such as Figure 2.3 As shown, a composite substrate 10 is provided, the composite substrate 10 including a first substrate 11, a first bonding layer 12 and a second substrate 13 stacked sequentially along the growth direction, wherein the first bonding layer 12 and the second substrate 13 are conductive;

[0073] S04, such as Figure 2.4 As shown, a second bonding layer 3 is formed on the surface of the epitaxial stack 2, wherein the second bonding layer 3 is conductive;

[0074] S05, such as Figure 2.5 As shown, the composite substrate 10 is bonded to the surface of the epitaxial stack 2 via the second bonding layer 3;

[0075] S06, such as Figure 2.6 As shown, the growth substrate 1 is peeled off;

[0076] S07, such as Figure 2.7 As shown, by etching the epitaxial stack 2, a plurality of sub-epitaxy stack 2 units isolated from each other by trenches 4 are formed;

[0077] S08, such as Figure 2.8 As shown, a first contact electrode 5 is deposited on the surface of each of the sub-epipolar stacks 2 on the side opposite to the composite substrate 10;

[0078] S09, such as Figure 2.9 As shown, the grooves 4 are cut to the surface of the first substrate 11 to form a plurality of LED light-emitting units that are isolated from each other by the cut channels 6.

[0079] This invention also provides a separation method for separating the LED light-emitting units prepared above, such as... Figure 3 As shown, the separation method includes:

[0080] The first substrate 11 is peeled off, leaving the first bonding layer 12 on the bottom surface of each of the LED light-emitting units.

[0081] In this embodiment of the invention, the first substrate 11 is peeled off by heating, etching, ultrasound, laser, or light irradiation. Preferably, heating is used, and the peeling temperature of the first substrate 11 is between the melting point of the first bonding layer 12 and the melting point of the second bonding layer 3.

[0082] As can be seen from the above technical solution, the low thermal resistance LED chip and its fabrication method provided by the present invention provide a composite substrate 10, which includes a first substrate 11, a first bonding layer 12, and a second substrate 13 stacked sequentially along a first direction; thereby, the epitaxial stack 2 is formed on the side surface of the second substrate 13 opposite to the first bonding layer 12 by bonding through the second bonding layer 3. Further, the second bonding layer 3 and the second substrate 13 are conductive. Thus, the high thermal conductivity of the second substrate 13 solves the thermal resistance problem of the LED chip; at the same time, the temporary support of the composite substrate 10 enhances the strength of the LED chip, avoiding warping and breakage problems during the fabrication process; and the temporary support of the composite substrate 10 eliminates the need for a grinding process, ensuring the consistency of the LED chip thickness and saving costs. It is particularly suitable for LED chips with high current density.

[0083] Based on this, subsequent separation methods, such as peeling off the first substrate 11 while retaining the first bonding layer 12 on the bottom surface of each LED light-emitting unit, can yield independent LED light-emitting units. This separation method is flexible, simple, easy to implement, and can reduce damage to the LED chip.

[0084] Example 2

[0085] like Figure 1 As shown, this embodiment of the invention provides another low thermal resistance LED chip, comprising:

[0086] A composite substrate 10, the composite substrate 10 comprising a first substrate 11, a first bonding layer 12 and a second substrate 13 stacked sequentially along a first direction;

[0087] Several sub-epitaxial stack 2 units, isolated from each other by dicing channels 6, are formed on the surface of the second substrate 13 opposite to the first bonding layer 12 by bonding through a second bonding layer 3; and the dicing channels 6 expose the first substrate 11; as shown Figure 5As shown, each of the sub-epitaxial stacks 2 includes at least a second type semiconductor layer 2.3, an active region 2.2, and a first type semiconductor layer 2.1 stacked sequentially along the first direction; the first direction is perpendicular to the composite substrate 10 and extends from the composite substrate 10 to the epitaxial stack 2;

[0088] The first contact electrode 5 is disposed on the surface of the first semiconductor layer 2.1 on the side opposite to the active region 2.2.

[0089] In this embodiment of the invention, the second bonding layer 3 and the second substrate 13 are conductive.

[0090] In this embodiment of the invention, the melting point of the second bonding layer 3 is higher than that of the first bonding layer 12.

[0091] In this embodiment of the invention, the temperature required to peel off the first substrate 11 is between the melting point of the first bonding layer 12 and the melting point of the second bonding layer 3.

[0092] In this embodiment of the invention, the second bonding layer 3 includes at least one of an ohmic contact layer and a metal reflective layer.

[0093] In this embodiment of the invention, the second bonding layer 3 comprises an alloy formed from one or at least two of Au, In, Ni, Sn, Ag, and Cu.

[0094] It is worth mentioning that the type of composite substrate 10 is not limited in the LED chip of this embodiment, as long as the first bonding layer 12 and the second substrate 13 are conductive. For example, the second substrate 13 includes a metal substrate; the material of the first bonding layer 12 can be metal or non-metal, and this embodiment does not limit this.

[0095] In addition, the materials of the second type semiconductor layer 2.3, the active region 2.2 and the first type semiconductor layer 2.1 of the epitaxial stack 2 are not limited in the LED chip of this embodiment. For example, the first type semiconductor layer 2.1 can be, but is not limited to, an N-type gallium nitride layer, and correspondingly, the second type semiconductor layer 2.3 can be, but is not limited to, a P-type gallium nitride layer.

[0096] This invention also provides a method for fabricating a low thermal resistance LED chip, the method comprising the following steps:

[0097] A01, such as Figure 2.1 As shown, a growth substrate 1 is provided;

[0098] A02, such as Figure 2.2 As shown, an epitaxial stack 2 is grown, which includes a first type semiconductor layer 2.1, an active layer, and a second type semiconductor layer 2.3 sequentially stacked on the surface of the growth substrate 1;

[0099] A03, such as Figure 2.3 As shown, a composite substrate 10 is provided, the composite substrate 10 including a first substrate 11, a first bonding layer 12 and a second substrate 13 stacked sequentially along the growth direction, wherein the second substrate 13 is conductive;

[0100] A04, such as Figure 2.4 As shown, a second bonding layer 3 is formed on the surface of the epitaxial stack 2, wherein the second bonding layer 3 is conductive;

[0101] A05, such as Figure 2.5 As shown, the composite substrate 10 is bonded to the surface of the epitaxial stack 2 via the second bonding layer 3;

[0102] A06, such as Figure 2.6 As shown, the growth substrate 1 is peeled off;

[0103] A07, such as Figure 2.7 As shown, by etching the epitaxial stack 2, a plurality of sub-epitaxy stack 2 units isolated from each other by trenches 4 are formed;

[0104] A08, such as Figure 2.8 As shown, a first contact electrode 5 is deposited on the surface of each of the sub-epipolar stacks 2 on the side opposite to the composite substrate 10;

[0105] A09, such as Figure 2.9 As shown, the grooves 4 are cut to the surface of the first substrate 11 to form a plurality of LED light-emitting units that are isolated from each other by the cut channels 6.

[0106] This invention also provides another separation method for separating the LED light-emitting units prepared above, such as... Figure 4 The separation method includes:

[0107] The first substrate 11 and the first bonding layer 12 are stripped away, so that the second substrate 13 serves as another contact electrode plate for each of the LED light-emitting units.

[0108] In this embodiment of the invention, the first substrate 11 and the first bonding layer 12 are peeled off by heating, etching, ultrasound, laser, or light irradiation.

[0109] In this embodiment of the invention, when the first substrate 11 and the first bonding layer 12 are peeled off by heating, the peeling temperature of both is lower than the melting point of the second bonding layer 3.

[0110] As can be seen from the above technical solution, the low thermal resistance LED chip and its fabrication method provided by the present invention provide a composite substrate 10, which includes a first substrate 11, a first bonding layer 12, and a second substrate 13 stacked sequentially along a first direction; thereby, the epitaxial stack 2 is formed on the side surface of the second substrate 13 opposite to the first bonding layer 12 by bonding through the second bonding layer 3. Further, the second bonding layer 3 and the second substrate 13 are conductive. Thus, the high thermal conductivity of the second substrate 13 solves the thermal resistance problem of the LED chip; at the same time, the temporary support of the composite substrate 10 enhances the strength of the LED chip, avoiding warping and breakage problems during the fabrication process; and the temporary support of the composite substrate 10 eliminates the need for a grinding process, ensuring the consistency of the LED chip thickness and saving costs. It is particularly suitable for LED chips with high current density.

[0111] Based on this, subsequent separation methods, such as peeling off the first substrate 11 and the first bonding layer 12, and using the second substrate 13 as another contact electrode plate for each LED light-emitting unit, yield independent LED light-emitting units. This separation method is flexible, simple, easy to implement, and reduces damage to the LED chip.

[0112] Example 3

[0113] The only difference between this embodiment and Embodiment 1 is the preparation method. Specifically, in the preparation method of this embodiment, after the epitaxial stack 2 is grown in step S02, it is first directly bonded to the second substrate 13 through the second bonding layer 3 on its surface, and then bonded to the first substrate 11 through the first bonding layer 12. Then, steps S06, S07, S08 and S09 described in Embodiment 1 are executed in sequence.

[0114] Example 4

[0115] The only difference between this embodiment and embodiment 2 is the preparation method. Specifically, in the preparation method of this embodiment, after the epitaxial stack 2 is grown in step A02, it is first directly bonded to the second substrate 13 through the second bonding layer 3 on its surface, and then bonded to the first substrate 11 through the first bonding layer 12. Then, steps A06, A07, A08, and A09 described in embodiment 2 are executed in sequence.

[0116] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on the differences from other embodiments. The same or similar parts between the various embodiments can be referred to each other.

[0117] It should also be noted that, in this document, relational terms such as "first" and "second" are used merely to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that an article or apparatus comprising a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such an article or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the article or apparatus that includes the aforementioned element.

[0118] The above description of the disclosed embodiments enables those skilled in the art to make or use this application. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of this application. Therefore, this application is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A low thermal resistance LED chip, characterized in that, include: A composite substrate, the composite substrate comprising a first substrate, a first bonding layer and a second substrate stacked sequentially along a first direction; A plurality of sub-epitaxial stack units isolated from each other by dicing channels are formed on the surface of the second substrate away from the first bonding layer by bonding through a second bonding layer; and the dicing channels expose the first substrate; each sub-epitaxial stack includes at least a second type semiconductor layer, an active region and a first type semiconductor layer stacked sequentially along the first direction; the first direction is perpendicular to the composite substrate and points from the composite substrate to the epitaxial stack; The first contact electrode is disposed on the surface of the first type semiconductor layer on the side away from the active region; The second bonding layer and the second substrate are conductive.

2. The low thermal resistance LED chip according to claim 1, characterized in that, The melting point of the second bonding layer is higher than that of the first bonding layer.

3. The low thermal resistance LED chip according to claim 1, characterized in that, The first bonding layer is conductive.

4. The low thermal resistance LED chip according to claim 1, characterized in that, The temperature required to peel off the first substrate is between the melting point of the first bonding layer and the melting point of the second bonding layer.

5. The low thermal resistance LED chip according to claim 1, characterized in that, The second bonding layer includes at least one of an ohmic contact layer and a metal reflective layer.

6. The low thermal resistance LED chip according to claim 1, characterized in that, The second bonding layer comprises an alloy formed from one or at least two of Au, In, Ni, Sn, Ag, and Cu.

7. A method for fabricating a low thermal resistance LED chip, characterized in that, The preparation method includes the following steps: S01, Provide a growth substrate; S02. Growing an epitaxial stack, wherein the epitaxial stack comprises a first type semiconductor layer, an active layer, and a second type semiconductor layer sequentially stacked on the surface of the growth substrate; S03. A composite substrate is provided, the composite substrate comprising a first substrate, a first bonding layer and a second substrate stacked sequentially along a growth direction, wherein the first bonding layer and the second substrate are conductive; S04. A second bonding layer is formed on the surface of the epitaxial stack, wherein the second bonding layer is conductive; S05. The composite substrate is bonded to the surface of the epitaxial stack via the second bonding layer; S06. Peel off the growth substrate; S07. By etching the epitaxial stack, a plurality of sub-epitaxy stack units isolated from each other by trenches are formed; S08. Deposit a first contact electrode on the surface of each of the sub-epipolar stacks facing away from the composite substrate; S09. Cut along each of the grooves to the surface of the first substrate, thereby forming a plurality of LED light-emitting units that are isolated from each other by the cut channels.

8. A separation method, characterized in that, The method for separating the LED light-emitting unit prepared according to claim 7 includes: The first substrate is peeled off, leaving the first bonding layer on the bottom surface of each of the LED light-emitting units.

9. A method for fabricating a low thermal resistance LED chip, characterized in that, The preparation method includes the following steps: A01. Provide a growth substrate; A02. Growing an epitaxial stack, wherein the epitaxial stack comprises a first type semiconductor layer, an active layer, and a second type semiconductor layer sequentially stacked on the surface of the growth substrate; A03. A composite substrate is provided, the composite substrate comprising a first substrate, a first bonding layer and a second substrate stacked sequentially along a growth direction, wherein the second substrate is conductive; A04. A second bonding layer is formed on the surface of the epitaxial stack, wherein the second bonding layer is conductive; A05. The composite substrate is bonded to the surface of the epitaxial stack via the second bonding layer; A06. Peel off the growth substrate; A07. By etching the epitaxial stack, a plurality of sub-epitaxy stack units isolated from each other by trenches are formed; A08. Deposit a first contact electrode on the surface of each of the sub-epipolar stacks facing away from the composite substrate; A09. Cut along each of the grooves to the surface of the first substrate, thereby forming a plurality of LED light-emitting units that are isolated from each other by the cut channels.

10. A separation method, characterized in that, The method for separating the LED light-emitting unit prepared according to claim 9 includes: The first substrate and the first bonding layer are stripped away, so that the second substrate serves as another contact electrode plate for each of the LED light-emitting units.

Images