CN115621372A - Device and method for stripping LED epitaxial substrate by laser - Google Patents

Device and method for stripping LED epitaxial substrate by laser Download PDF

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Publication number
CN115621372A
CN115621372A CN202110796299.6A CN202110796299A CN115621372A CN 115621372 A CN115621372 A CN 115621372A CN 202110796299 A CN202110796299 A CN 202110796299A CN 115621372 A CN115621372 A CN 115621372A
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laser
led wafer
led
epitaxial substrate
wafer
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Inventor
范伟宏
毕京锋
郭茂峰
操晓敏
谢安军
赵进超
金全鑫
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Xiamen Silan Advanced Compound Semiconductor Co Ltd
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Xiamen Silan Advanced Compound Semiconductor Co Ltd
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Priority to CN202110796299.6A priority Critical patent/CN115621372A/en
Priority to PCT/CN2022/078632 priority patent/WO2023284305A1/en
Publication of CN115621372A publication Critical patent/CN115621372A/en
Pending legal-status Critical Current

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Abstract

The invention provides equipment and a method for stripping an LED epitaxial substrate by laser, wherein a cover plate can be adopted to compress an LED wafer during laser stripping, so that the warping problem of the LED wafer is improved, the LED wafer is flatly fixed on a bearing table, and the defocusing problem of certain positions on the LED wafer during laser scanning is avoided, so that the time for focal point adjustment in the laser scanning process is reduced, the production efficiency is improved, the cracking phenomenon during the stress realization of the warping position of the wafer during laser scanning can be avoided, and the production yield is improved; because the cover plate can transmit ultraviolet light, the transmission of laser beams in an ultraviolet wave band is not influenced.

Description

Device and method for stripping LED epitaxial substrate by laser
Technical Field
The invention relates to the technical field of laser lift-off, in particular to a device and a method for laser lift-off of an LED epitaxial substrate.
Background
Compared with the LED chip technology of a forward mounting structure and an inverted mounting structure, the LED chip with the vertical structure has the remarkable advantages that: on one hand, the LED chip can bear higher working current and obtain higher brightness because the epitaxial layer is transferred from the epitaxial substrate (such as sapphire) with poor insulation and heat dissipation to the bonding substrate with excellent electric conduction and heat conduction capability; on the other hand, the surface of the LED chip with the vertical structure is easy to carry out micro-nano processing, the total reflection of nitride materials (GaN, alN and ternary alloy compounds thereof) and an air interface is reduced, the light extraction efficiency of the LED chip can be increased, and the improvement of the brightness and the light effect is greatly facilitated. The mainstream substrate transfer technology of the current vertical structure LED chip adopts a silicon substrate or a metal substrate as a bonding substrate, the metal substrate has the advantages of providing better electric conduction and heat conduction capability, and because the metal substrate has better extensibility, the thicker metal substrate can relieve the warping phenomenon generated after the LED wafer is bonded, but because the metal substrate has higher cost, and the cutting processing of the thicker metal substrate needs to use a laser with high power and small light spot size (the laser light spots are prevented from damaging the chip area at the periphery of a cutting channel), the equipment investment is further increased, and the large-scale application of the LED chip based on the vertical structure of the metal substrate is limited.
The silicon substrate has poorer electric and heat conduction capability than a metal substrate, relatively lower cost and very mature cutting processing technology, so the silicon substrate has more advantages in comparison of material and process cost. However, the lattice mismatch and thermal mismatch of silicon and gallium nitride materials are both large, and a metal bonding layer needs to be used for bonding under a relatively high temperature condition (greater than 200 ℃) to obtain good mechanical strength, due to the problems of lattice mismatch and thermal mismatch of silicon, gallium nitride and sapphire materials, the LED wafer is inevitably warped due to cooling after bonding, and the problem of LED wafer warping is aggravated in LED wafers with larger sizes such as 6 inches and above, although the phenomenon can be improved to a certain extent by adopting the manner of thinning the sapphire substrate and thickening the silicon substrate, the technical cost is increased and the problem of waste of unnecessary materials is solved by adopting the scheme.
When the LED epitaxial layer is stripped from the epitaxial substrate, the interface between the epitaxial layer and the epitaxial substrate needs to be scanned by laser, in the laser scanning process, an ultraviolet light wave band laser beam with photon energy larger than the forbidden band width of the epitaxial layer is generally adopted, laser penetrates through sapphire and is focused on the interface between the sapphire and nitride, so that the nitride is thermally decomposed, metal generated after the nitride is decomposed is heated and melted, and then the stripping of the epitaxial substrate can be realized. However, the LED wafer cannot be flatly fixed on the carrying table when warped, so that the LED wafer always has some defocused positions during laser scanning, and in order to achieve the purpose of peeling off the epitaxial substrate, the focus adjustment time needs to be increased, the peeling process time is increased, and the production efficiency is affected; and the nitride at the interface absorbs the high heat of the laser beam, and is rapidly decomposed and expanded to generate a large amount of gas and plasma to form impact force, so that cracks are easy to appear at the warping position, and the production yield is reduced.
Disclosure of Invention
The invention aims to provide equipment and a method for stripping an LED epitaxial substrate by laser, which aim to solve the problems of low production efficiency and yield of the existing equipment for stripping the LED epitaxial substrate by laser.
In order to achieve the above object, the present invention provides an apparatus for laser lift-off of an LED epitaxial substrate, comprising:
the wafer bearing assembly comprises a movable bearing platform, and the bearing platform is used for bearing and fixing the LED wafer;
the cover plate assembly comprises a cover plate capable of transmitting ultraviolet light, and the cover plate is positioned above the bearing table and can move in a direction close to or far away from the bearing table so as to press or release the LED wafer; and the number of the first and second groups,
and the laser component is used for emitting at least one laser beam, and the laser beam irradiates the LED wafer after penetrating through the cover plate and scans the LED wafer so as to strip the epitaxial substrate of the LED wafer.
Optionally, the LED wafer is a vertical LED wafer.
Optionally, the wafer carrying assembly further includes:
and the heating unit is used for heating the bearing table to a preset temperature.
Optionally, the predetermined temperature is 25 ℃ to 800 ℃.
Optionally, when the cover plate presses the LED wafer, a pressure within a range of 10kgf to 1000kgf is applied to the LED wafer.
Optionally, the wafer carrying assembly further includes a first driving unit for driving the carrying table to move; and/or the cover plate assembly further comprises a second driving unit for driving the cover plate to move along the direction close to or far away from the bearing table.
Optionally, the bearing surface of the bearing table and the surface of the cover plate facing the bearing table are both flat surfaces.
Optionally, a groove for accommodating the LED wafer is formed in the carrier, a protrusion is formed on one surface of the cover plate facing the carrier, and when the cover plate moves in a direction close to the carrier, the protrusion enters the groove and compresses the LED wafer.
Optionally, the inner wall of the groove and the outer wall of the protrusion are both step-shaped, and the shape and size of the step of the protrusion are matched with those of the step of the groove.
Optionally, the carrying table further has a plurality of adsorption holes for vacuum adsorption of the LED wafer.
Optionally, the carrier assembly further includes a third driving unit and at least three pins located in the carrier table, the vertices of the at least three pins are not collinear, and the third driving unit is configured to drive the pins to jack up or put down the LED wafer.
Optionally, the laser assembly includes:
the light source module is used for emitting laser beams with preset wavelengths;
the light splitting module is used for splitting the laser beam emitted by the light source module into at least two laser beams with the same energy distribution; and the number of the first and second groups,
and the shaping module is used for shaping at least two laser beams and irradiating the laser beams onto the LED wafer.
Optionally, the laser assembly further includes:
and the scanning projection module is used for controlling the laser beam to move along at least one preset track so as to scan the LED wafer.
Optionally, the laser assembly further includes:
and the splicing module is used for splicing and irradiating the shaped at least two laser beams onto the LED wafer.
Optionally, the light source module is an excimer laser or a DPSS laser, and the predetermined wavelength is 150nm to 330nm.
Optionally, the light spot of the laser beam is a point light spot or a linear light spot.
Optionally, the method further includes:
the first image detection assembly is used for detecting the marks on the LED wafer so as to acquire the position information of the LED wafer; and the number of the first and second groups,
and the second image detection assembly is used for monitoring the stripping condition of the epitaxial substrate of the LED wafer in real time.
Optionally, the bearing surface of the bearing table is made of one or more of anodized aluminum, stainless steel, silicon carbide, or aluminum nitride.
Optionally, the cover plate is made of high-purity quartz, sapphire or aluminum nitride crystal.
Optionally, the method further includes:
and the control assembly is used for controlling the bearing table and/or the cover plate to move.
Optionally, the method further includes:
and the upper and lower wafer assemblies are used for placing the LED wafer on the bearing table and sequentially taking down the stripped epitaxial substrate and the LED wafer.
The invention also provides a method for carrying out laser stripping on the LED epitaxial substrate by using the device for laser stripping the LED epitaxial substrate, which comprises the following steps:
placing the LED wafer on a bearing table;
the cover plate moves along the direction close to the bearing table until the LED wafer is pressed tightly;
the bearing table moves to realize the alignment of the LED wafer and the laser assembly;
the laser assembly emits at least one laser beam and scans the LED wafer to strip the epitaxial substrate of the LED wafer; and the number of the first and second groups,
and the cover plate moves in the direction far away from the bearing table to release the LED wafer, and the stripped epitaxial substrate and the stripped LED wafer are taken down from the bearing table in sequence.
Optionally, before the laser assembly emits at least one laser beam and scans the LED wafer, the heating unit heats the susceptor to a predetermined temperature.
Optionally, the carrying table moves along a predetermined track to enable the laser beam to scan the LED wafer; or the laser beam moves along the preset track to scan the LED wafer.
The device and the method for stripping the LED epitaxial substrate by laser provided by the invention have the following beneficial effects:
1) The cover plate can be adopted to compress the LED wafer during laser stripping, so that the warping problem of the LED wafer is improved, the LED wafer is flatly fixed on the bearing table, the defocusing problem of certain positions on the LED wafer during laser scanning is avoided, the time for focal point adjustment in the laser scanning process is reduced, the production efficiency is improved, the crack phenomenon during the stress realization of the warping position of the wafer during laser scanning can be avoided, and the production yield is improved; because the cover plate can transmit ultraviolet light, the transmission of laser beams in an ultraviolet band cannot be influenced.
2) Before the laser assembly emits at least one laser beam and scans the LED wafer, the heating unit heats the bearing table to a preset temperature, so that metal generated after nitride absorbs laser energy and is decomposed is melted, and the laser stripping effect and speed are improved.
3) The bearing table is provided with a groove for accommodating the LED wafer, and the LED wafer is limited by the groove, so that an adsorption hole is not required to be formed in the bearing table, and the structure is simplified.
4) The laser beam emitted by the light source module is divided into at least two laser beams with the same energy distribution by the light splitting module, and then the at least two laser beams are spliced or moved to different paths (graph complementation) and simultaneously irradiated onto the LED wafer, compared with single-beam laser beam scanning, a plurality of laser beams have larger unit area after being spliced, the laser stripping efficiency can be improved, and energy waste can not be caused; and the energy of the laser beam emitted by the light source module is reduced after the light beam is split, an attenuator is not required to be additionally arranged in the laser assembly, and the cost is reduced.
4) The bearing surface of the bearing table is made of one or more of anodized aluminum, stainless steel, silicon carbide or aluminum nitride, and the bearing surface is prevented from being uneven after being oxidized, so that the problem that the LED wafer cannot be smoothly fixed on the bearing table is solved.
Drawings
Fig. 1 is a schematic structural diagram of an apparatus for laser lift-off of an LED epitaxial substrate according to an embodiment of the present invention;
fig. 2 is a schematic structural diagram of a vertical deep ultraviolet LED wafer according to an embodiment of the present invention;
fig. 3 is a schematic structural diagram of a vertical structure green/blue/near-ultraviolet LED wafer according to an embodiment of the present invention;
fig. 4a is a schematic view of scanning the LED wafer according to an embodiment of the present invention;
fig. 4b is another schematic diagram of scanning the LED wafer according to the first embodiment of the present invention;
fig. 4c is another schematic view of scanning the LED wafer according to the first embodiment of the present invention;
fig. 5 is a flowchart of a method for laser lift-off of an LED epitaxial substrate according to an embodiment of the present invention;
fig. 6 is a schematic structural diagram of an apparatus for laser lift-off of an LED epitaxial substrate according to a second embodiment of the present invention;
wherein the reference numerals are:
101-a carrier table; 101 a-a groove; 102-a first drive unit; 103-a thimble; 104-a third drive unit; 105-a via; 106-adsorption pores; 201-cover plate; 201 a-projection; 202-a second drive unit; 301-a light source module; 302-an optical mechanism; 303 a-a first laser beam; 303 b-a second laser beam; 401-a first image detection component; 402-a second image detection component; 500-an LED wafer;
510-vertical structure deep ultraviolet LED wafer; 520-vertical structure green/blue/near ultraviolet LED wafer; 512. 522-bonding a substrate; 513. 523-a functional layer; 514. 524-epitaxial layer; 515-a buffer layer; 516. 526 an epitaxial substrate; 514a, 524 a-first semiconductor layer; 514b, 524 c-quantum well layer; 514c, 524 b-second semiconductor layer.
Detailed Description
The following describes in more detail embodiments of the present invention with reference to the schematic drawings. The advantages and features of the present invention will become more apparent from the following description. It is to be noted that the drawings are in a very simplified form and are not to precise scale, which is merely for the purpose of facilitating and distinctly claiming the embodiments of the present invention.
Example one
Fig. 1 is a schematic structural diagram of an apparatus for laser lift-off of an LED epitaxial substrate according to this embodiment. As shown in fig. 1, the apparatus for laser lift-off of an LED epitaxial substrate includes a wafer carrier assembly, a cover plate assembly, a laser assembly, an upper and a lower wafer assemblies, and a control assembly.
Referring to fig. 1, the wafer carrier assembly includes a susceptor 101, a first driving unit 102, at least three pins 103, a third driving unit 104, and a heating unit.
Specifically, the susceptor 101 is used for supporting and fixing the LED wafer 500. The upper surface of the susceptor 101 is a bearing surface thereof, and the LED wafer 500 is placed on the bearing surface of the susceptor 101.
The LED wafer 500 is a vertical structure LED wafer, for example, the LED wafer 500 may be a vertical structure deep ultraviolet LED wafer or a vertical structure green/blue/near ultraviolet LED wafer, and the size thereof may be 2 inches or 8 inches, and the invention is not limited thereto.
Fig. 2 is a schematic structural diagram of a vertical deep ultraviolet LED wafer 510 according to the present embodiment. As shown in fig. 2, the vertical deep ultraviolet LED wafer 510 includes a bonding substrate 512, a functional layer 513, an epitaxial layer 514, a buffer layer 515, and an epitaxial substrate 516, which are stacked in sequence from bottom to top. The bonding substrate 512 may be a metal substrate or a silicon substrate. The functional layer 513 is a combination of film layers such as a mirror layer, a metal protective layer, an insulating protective layer, and an electrode. The functional layer 513 is permanently bonded to the bonding substrate 512. The epitaxial layer 514 includes a first semiconductor layer 514a, a quantum well layer 514b and a second semiconductor layer 514c stacked in sequence from bottom to top, in this embodiment, the buffer layer 515 is made of AlN, the first semiconductor layer 514a is made of P-AlGaN, and the second semiconductor layer is made of N-AlGaN. When the deep ultraviolet LED wafer 510 with the vertical structure is placed on the bearing surface of the bearing table 101, the bonding substrate 512 is attached to the bearing surface, and the epitaxial substrate 516 faces upward.
Fig. 3 is a schematic structural diagram of a vertical structure green/blue/near-ultraviolet LED wafer 520 according to the present embodiment. As shown in fig. 3, the vertical structure green/blue/near ultraviolet LED wafer 520 includes a bonding substrate 522, a functional layer 523, an epitaxial layer 524, and an epitaxial substrate 526, which are stacked in sequence from bottom to top. The positions and structures of the bonding substrate 522 and the functional layer 523 are similar to those of the vertical structure deep ultraviolet LED wafer 510, and are not described in detail herein. The epitaxial layer 524 includes a first semiconductor layer 524a, a second semiconductor layer 524b, and a quantum well layer 524c stacked in sequence from bottom to top, in this embodiment, the first semiconductor layer 514a is made of P-GaN, and the second semiconductor layer is made of N-GaN. When the vertical structure green/blue/near ultraviolet LED wafer 510 is placed on the carrying surface of the carrying table 101, the bonding substrate 522 is attached to the carrying surface, and the epitaxial substrate 526 faces upward.
Referring to fig. 1, the bearing surface of the bearing table 101 is a flat surface, an absorption hole 106 is formed in the bearing table 101, the absorption hole 106 is located in the bearing table 101 and penetrates through the bearing table 101, the absorption hole 106 is connected to a vacuum device, when the LED wafer 500 is placed on the bearing surface of the bearing table 101, the vacuum device vacuumizes through the absorption hole 106, and negative pressure is generated in the absorption hole 106 to fix the LED wafer 500 on the bearing table 101.
The number of the adsorption holes 106 may be one or more, and the pore diameter of the adsorption holes 106 may be 10um to 100um.
Further, the bearing surface of the bearing table 101 is made of one or more of anodized aluminum, stainless steel, silicon carbide, aluminum nitride and other materials with stable performance and high thermal conductivity coefficient, so as to prevent the bearing surface of the bearing table 101 from being uneven after being oxidized, and further avoid the problem that the LED wafer 500 cannot be smoothly fixed on the bearing table 101.
Referring to fig. 1, the control device is electrically connected to the first driving unit 102, and the control device controls the first driving unit 102 to drive the susceptor 101 to move along the X/Y/Z direction and/or rotate in the XY plane, at this time, the LED wafer 500 also moves along with the susceptor 101. Therefore, the control component controls the first driving unit 102 to drive the carrying table 101 to move, so that the position of the LED wafer 500 can be changed.
Further, the heating unit is disposed in the susceptor 101 for heating the susceptor 101, and the susceptor 101 has a susceptor surface capable of conducting heat, so as to increase the temperature of the LED wafer 500. The heating unit may be, for example, a heating wire disposed in the susceptor 101, and the invention is not limited thereto.
In this embodiment, the heating unit may heat the susceptor 101 to a predetermined temperature according to requirements, and the predetermined temperature is, for example, 25 ℃ to 800 ℃.
Referring to fig. 1, at least three through holes 105 are formed in the susceptor 101, and one of the pins 103 is located in one of the through holes 105, that is, at least three pins 103 are formed in the susceptor 101. The control component is electrically connected to the third driving unit 104, and the control component can control the third driving unit 104 to drive at least three of the ejector pins 103 to move along the Z direction synchronously, so as to jack up or put down the LED wafer 500.
Further, the vertexes of at least three of the thimble 103 are not collinear, so that the thimble 103 can smoothly lift or lower the LED wafer 500.
With continued reference to fig. 1, the cover plate assembly includes a second driving unit 202 and a cover plate 201 capable of transmitting ultraviolet light.
The cover plate 201 is located above the susceptor 101, and the greater the transmittance of the ultraviolet light of the cover plate 201, the better, therefore, the cover plate 201 may be made of a material that can transmit ultraviolet light, such as high-purity quartz, sapphire, or aluminum nitride crystal.
The control component is electrically connected to the second driving unit 202, and the control component can control the second driving unit 202 to drive the cover plate 201 to move in a direction close to or away from the susceptor 101, so as to compress or release the LED wafer 500. When the cover plate 201 presses the LED wafer 500, a pressure in a range of 10kgf to 1000kgf may be applied to the LED wafer 500 at the same time, so as to substantially improve the problem of warping of the LED wafer 500, so that the LED wafer 500 is smoothly fixed on the susceptor 101.
Further, one surface of the cover plate 201 facing the susceptor 101 is also a flat surface, so that when the cover plate 201 compresses the LED wafer 500, the bearing surface of the susceptor 101 and the surface of the cover plate 201 facing the susceptor 101 may be respectively attached to the upper and lower surfaces of the LED wafer 500.
Referring to fig. 1, the laser assembly is located above the cover plate 201, and includes a light source module 301 and an optical mechanism 302, where the optical mechanism 302 includes a light splitting module, a shaping module, and a scanning projection module.
The light source module 301 is configured to emit a laser beam with a predetermined wavelength. In this embodiment, the light source module 301 is an excimer laser orOne of DPSS lasers, which may be a KrF excimer laser, an ArF excimer laser, or a F excimer laser 2 Excimer lasers and the like, which can achieve laser beam output of a predetermined wavelength in a wavelength range of 150nm to 330nm.
The optical splitting module may split the laser beam emitted by the light source module 301 into at least two laser beams with the same energy distribution, the shaping module shapes the at least two laser beams into laser beams with a predetermined shape and then irradiates the LED wafer 500 through the cover plate 201, and the scanning projection module may control the at least two laser beams to move along at least one predetermined track to scan the LED wafer 500, so as to scan the epitaxial substrate of the LED wafer 500.
In this embodiment, the optical mechanism 302 further includes a splicing module, configured to splice the shaped at least two laser beams and irradiate the laser beams onto the LED wafer, so that the at least two laser beams move along the same predetermined track.
It should be understood that when at least two laser beams are not spliced but directly irradiated onto the LED wafer 500, each laser beam respectively moves along one predetermined track, and the predetermined tracks corresponding to each laser beam may be the same or different.
For example, fig. 4a is a schematic diagram of scanning the LED wafer 500 according to the present embodiment. As shown in fig. 4a, the splitting module splits the laser beam emitted from the light source module 301 into two laser beams, and for convenience of description, the two laser beams formed by splitting are referred to as a first laser beam 303a and a second laser beam 303b. The shaping module shapes the first laser beam 303a and the second laser beam 303b into a linear beam, and the splicing module seamlessly splices the first laser beam 303a and the second laser beam 303b together along the Y direction. After the first laser beam 303a and the second laser beam 303b are irradiated onto the LED wafer 500, two linear light spots are formed. The sum of the widths of the first laser beam 303a and the second laser beam 303b in the Y direction after being spliced is greater than or equal to the diameter of the LED wafer 500, so that the scanning projection module controls the first laser beam 303a and the second laser beam 303b to synchronously reciprocate in the X direction, and the LED wafer 500 can be scanned.
Fig. 4b is another schematic diagram of the LED wafer 500 according to the present embodiment. As shown in fig. 4b, the shaping module may further shape the first laser beam 303a and the second laser beam 303b into a spot beam, and the splicing module seamlessly splices the first laser beam 303a and the second laser beam 303b together along the X direction. After the first laser beam 303a and the second laser beam 303b are irradiated onto the LED wafer 500, two square point-like light spots are formed. In this way, the scanning projection module controls the first laser beam 303a and the second laser beam 303b to move along the S-shaped track synchronously, so as to scan the LED wafer 500.
Fig. 4c is another schematic diagram of the LED wafer 500 according to the embodiment. As shown in fig. 4c, the shaping module may further shape the first laser beam 303a and the second laser beam 303b into spot beams, where the first laser beam 303a and the second laser beam 303b are not spliced but directly irradiate onto the LED wafer 500, and the first laser beam 303a and the second laser beam 303b have a gap in the X direction and have the same position in the Y direction. After the first laser beam 303a and the second laser beam 303b are irradiated onto the LED wafer 500, two square point-like light spots are formed. In this way, the scanning projection module controls the first laser beam 303a and the second laser beam 303b to synchronously move along the X direction and the Y direction, so as to scan the LED wafer 500.
Compared with the method that the laser beam emitted by the light source module 301 is directly irradiated to the LED wafer 500 for scanning, the energy of the laser beam after light splitting is reduced, an attenuator is not required to be additionally arranged in a laser assembly, and the cost is reduced; in addition, the laser beam formed after splicing has larger unit area, the efficiency of laser stripping can be improved, and the waste of energy can not be caused.
Alternatively, the light splitting unit may be an optical element such as a grating that can split light.
As an alternative embodiment, the laser assembly may also only include the light source module 301, but since the energy of the laser beam emitted by the light source module 301 is high, an attenuator may be added in the optical path of the laser beam, so as to avoid damaging the epitaxial layers of the LED wafer 500 during the laser lift-off process.
As an alternative embodiment, the scanning projection module may also be omitted, and in this case, the control component controls the first driving unit 102 to drive the carrying table 101 to move along a predetermined trajectory, so as to also implement scanning of the LED wafer 500.
As an alternative embodiment, the laser assembly may further include a laser spot quality analysis module, configured to detect an energy size, an energy distribution uniformity, and the like of the laser beam before scanning. The energy distribution of the laser beam may be a flat-top distribution or a gaussian distribution.
As an alternative embodiment, the laser assembly may further comprise a laser power meter, which may detect the power of the laser beam.
Referring to fig. 1, a first image inspection assembly 401 and a second image inspection assembly 402 are disposed above the cover plate 201. The first image detection assembly 401 is configured to detect a mark on the LED wafer 500 to obtain position information of the LED wafer 500, the first image detection assembly 401 is electrically connected to the control assembly, and the control assembly can control the first driving unit 102 to drive the carrying table 101 to move according to the position information detected by the first image detection assembly 401, so as to align the LED wafer 500. Specifically, the control module may control the first driving unit 102 to drive the stage 101 to move along the X/Y direction or rotate in the XY plane, so that the LED wafer 500 is located within the scanning range of the laser module; meanwhile, the control assembly can also control the first driving unit 102 to drive the carrying table 101 to move along the Z direction, so that the LED wafer 500 and the laser assembly are focused. Further, the second image detection component 402 is configured to shoot the LED wafer 500 in real time on the whole surface, so as to monitor the peeling condition of the epitaxial substrate of the LED wafer 500 in real time.
In this embodiment, the first image detection assembly 401 and the second image detection assembly 402 are both high-resolution CCD image detectors, and light sources thereof may adopt multi-wavelength visible light or infrared LED light sources.
Further, the upper and lower wafer assemblies are electrically connected to the control assembly, and the control assembly can control the upper and lower wafer assemblies to place the LED wafer 500 on the platform 101, and to take the stripped epitaxial substrate and the LED wafer 500 off the platform 101.
Based on the above, the present embodiment also provides a method for performing laser lift-off of an LED epitaxial substrate by using the apparatus for laser lift-off of an LED epitaxial substrate. Fig. 5 is a flowchart of a method for laser lift-off of an LED epitaxial substrate according to this embodiment, and as shown in fig. 5, the method for laser lift-off of an LED epitaxial substrate includes:
step S100: placing the LED wafer 500 on the susceptor 101;
step S200: the cover plate 201 moves in a direction close to the bearing table 101 until the LED wafer 500 is pressed;
step S300: the bearing table 101 moves to achieve alignment of the LED wafer 500 and the laser assembly;
step S400: the laser component emits at least one laser beam and scans the LED wafer 500 to strip the epitaxial substrate of the LED wafer 500; and (c) a second step of,
step S500: the cover plate 201 moves in the direction away from the bearing table 101, releases the LED wafer 500, and sequentially takes off the epitaxial substrate and the LED wafer 500 after being peeled from the bearing table 101.
Specifically, step S100 is executed first, the control component controls the third driving unit 104 to drive the thimble 103 to rise above the platform 101, the upper and lower wafer components place the LED wafer 500 on the thimble 103, and the epitaxial substrate of the LED wafer 500 is placed facing upward. The thimble 103 descends, the LED wafer 500 is placed on the carrying table 101, and the suction holes 106 suck the LED wafer 500.
Then, the heating unit heats the susceptor 101, so as to increase the temperature of the LED wafer 500. Of course, when the temperature to be maintained by the susceptor 101 is high, the heating time is long, and in order not to affect the subsequent steps, the heating of the susceptor 101 may be started before the LED wafer 500 is placed on the susceptor 101; conversely, when the temperature of the susceptor 101 needs to be kept low, the susceptor 101 may be heated again in the subsequent step.
Step S200 is executed, in which the control component controls the second driving unit 202 to drive the cover plate 201 to move in a direction close to the susceptor 101 until the LED wafer 500 is pressed, and applies pressure to the LED wafer 500 at the same time, so that the LED wafer 500 is flatly fixed on the susceptor 101.
In step S300, the first image inspection module 401 starts to inspect the position information of the LED wafer 500 and sends the inspected position information to the control module. The control component determines whether the LED wafer 500 is aligned with the laser component according to the detection result of the first image detection component 401, and when the LED wafer 500 is not in the scanning range of the laser component and/or the LED wafer 500 is not in focus with the laser component, the control component controls the first driving unit 102 to drive the carrying table 101 to move along the X/Y/Z direction and/or rotate in the XY plane until the LED wafer 500 is aligned with the laser component.
Step S400 is executed, at this time, the carrying table 101 has reached the predetermined temperature, the scanning projection module controls the spliced laser beam to move along the predetermined trajectory to scan the LED wafer 500, the nitride on the interface between the epitaxial substrate of the LED wafer 500 and the epitaxial layer thereof is thermally decomposed under the action of the high-energy laser, metal and nitrogen gas are generated, wherein the metal is melted at the predetermined temperature, and thus the epitaxial substrate of the LED wafer 500 can be peeled.
It should be understood that, as an alternative embodiment, the control component may also control the first driving unit 102 to drive the carrier stage 101 to move along the predetermined track, so that the spliced laser beam scans the LED wafer 500 until the epitaxial substrate of the LED wafer 500 is peeled.
When the LED wafer 500 is scanned, the second image detection component 402 monitors the peeling condition of the epitaxial substrate of the LED wafer 500 in real time, and can determine the peeling condition of the epitaxial substrate according to the detection result of the second image detection component 402, so as to perform supplementary scanning on the area with poor peeling effect in time.
Step S500 is executed, the second driving unit 202 drives the cover plate 201 to move in a direction away from the susceptor 101, and after the cover plate 201 leaves, the pressure on the LED wafer 500 disappears. The control assembly controls the third driving unit 104 to drive the thimble 103 to jack up the LED wafer 500, and the upper and lower wafer assemblies firstly take and place the stripped epitaxial substrate at a recycling station, and then take and place the rest part of the LED wafer 500 in a wafer box.
Further, as shown in fig. 2, when the LED wafer 500 is a vertical deep ultraviolet LED wafer 510, the laser module selects a 193nm ArF excimer laser as the light source module 301, and the cover plate 201 applies a pressure greater than 400kgf to the vertical deep ultraviolet LED wafer 510, and heats the carrier stage 101 to 600 ℃, so that Al generated after thermal decomposition of the buffer layer 515 is melted to peel off the epitaxial substrate.
As shown in fig. 3, when the LED wafer 500 is a vertical structure green/blue/near-ultraviolet LED wafer 510, the laser module uses a KrF excimer laser with a wavelength of 248nm as the light source module 301, and the cover plate 201 applies a pressure greater than 200kgf to the vertical structure deep-ultraviolet LED wafer 510, and heats the susceptor 101 to 150 ℃, so that the Ga metal decomposed from the buffer layer 525 is melted to peel off the epitaxial substrate.
Example two
Fig. 6 is a schematic structural diagram of the apparatus for laser lift-off of an LED epitaxial substrate according to this embodiment. As shown in fig. 6, the difference from the first embodiment is that in the first embodiment, the carrier 101 has a groove 101a for accommodating the LED wafer 500, a surface of the cover plate 201 facing the carrier 101 has a protrusion 201a, and when the cover plate 201 moves in a direction approaching or moving away from the carrier 101, the protrusion 201a enters the groove 101a and presses the LED wafer 500.
Optionally, the shapes of the groove 101a and the protrusion 201a may be both circular, and the outer diameters of the groove 101a and the protrusion 201a are matched. In this way, the protrusion 201a can enter the groove 101a to cooperate with the groove 101a to fix the LED wafer 500.
Of course, as an alternative embodiment, the shapes of the groove 101a and the protrusion 201a may also be different, for example, the shape of the groove 101a is circular, and the shape of the protrusion 201a is rectangular; the outer diameters of the groove 101a and the protrusion 201a may not match, and the outer diameter of the protrusion 201a is smaller than the outer diameter of the groove 101 a.
Referring to fig. 6, in this embodiment, the inner wall of the groove 101a and the outer wall of the protrusion 201a are both stepped and have two steps, the steps of the protrusion 201a are matched with the steps of the groove 101a in shape and size, and when the LED wafer 500 is not placed in the groove 101a, the protrusion 201a enters the groove 101a and is just matched with the groove 101 a. In this way, the grooves 101a can accommodate two sizes of LED wafers 500, the cover plate 201 can also realize the compression of the LED wafers with different sizes, and the apparatus for laser lift-off of the LED epitaxial substrate has wider application.
Of course, the inner wall of the groove 101a and the outer wall of the protrusion 201a are not limited to have two steps, but may have three or four steps, etc., so that LED wafers with more sizes may be applied, which is not illustrated herein.
Compared with the first embodiment, in the present embodiment, since the susceptor 101 has the groove 101a, the LED wafer 500 can be limited by the groove 101a, and after the LED wafer 500 is placed on the susceptor 101, even if the cover plate 201 does not press the LED wafer 500, the LED wafer 500 does not shake freely, so that the suction hole 106 does not need to be formed in the susceptor 101, and the structure is simplified.
Of course, even if the susceptor 101 has the grooves 101a, the susceptor 101 may be provided with the adsorption holes 106, which does not affect the implementation of the present invention.
In summary, in the apparatus and method for laser lift-off of an LED epitaxial substrate according to the embodiments of the present invention, a cover plate may be used to compress an LED wafer during laser lift-off, so as to improve the warpage of the LED wafer, so that the LED wafer is smoothly fixed on a carrier table, and the defocusing of some positions on the LED wafer during laser scanning is avoided, thereby reducing the time for adjusting a focal point during laser scanning, improving the production efficiency, and avoiding the occurrence of cracks when the stress of the warped position of the wafer during laser scanning is realized, thereby improving the production yield; because the cover plate can transmit ultraviolet light, the transmission of laser beams in an ultraviolet band cannot be influenced. Furthermore, before the laser assembly emits at least one laser beam and scans the LED wafer, the heating unit heats the bearing table to a preset temperature, so that metal generated after nitride absorbs laser energy and is decomposed is melted, and the laser stripping effect and speed are improved. Furthermore, the bearing table is provided with a groove for accommodating the LED wafer, and the LED wafer is limited by the groove, so that an adsorption hole is not required to be formed in the bearing table, and the structure is simplified. Furthermore, the light splitting module is used for splitting the laser beam emitted by the light source module into at least two laser beams with the same energy distribution, and then the at least two laser beams are spliced or moved to different paths (graph complementation) and simultaneously irradiated onto the LED wafer, compared with single-beam laser beam scanning, a plurality of laser beams have larger unit area after being spliced, the laser stripping efficiency can be improved, and energy waste can be avoided; and the energy of the laser beam emitted by the light source module is reduced after the light beam is split, an attenuator is not required to be additionally arranged in the laser assembly, and the cost is reduced. Furthermore, the bearing surface of the bearing table is made of one or more of anodized aluminum, stainless steel, silicon carbide or aluminum nitride, so that the bearing surface is prevented from being uneven after being oxidized, and the problem that the LED wafer cannot be smoothly fixed on the bearing table is avoided.
It should be noted that, in the present specification, the embodiments are described in a progressive manner, each embodiment focuses on differences from other embodiments, and the same and similar parts among the embodiments may be referred to each other. For the system disclosed by the embodiment, the description is relatively simple because the system corresponds to the method disclosed by the embodiment, and the relevant points can be referred to the method part for description.
It should be noted that, although the present invention has been described with reference to the preferred embodiments, the present invention is not limited to the embodiments. It will be apparent to those skilled in the art from this disclosure that many changes and modifications can be made, or equivalents modified, in the embodiments of the invention without departing from the scope of the invention. Therefore, any simple modification, equivalent change and modification made to the above embodiments according to the technical essence of the present invention will still fall within the protection scope of the technical solution of the present invention.
It should be further understood that the terms "first," "second," "third," and the like in the description are used for distinguishing between various components, elements, steps, and the like, and are not intended to imply a logical or sequential relationship between various components, elements, steps, or the like, unless otherwise indicated or indicated.
It is also to be understood that the terminology used herein is for the purpose of describing particular embodiments only, and is not intended to limit the scope of the present invention. It must be noted that, as used herein and in the appended claims, the singular forms "a," "an," and "the" include plural referents unless the context clearly dictates otherwise. For example, reference to "a step" or "an apparatus" means a reference to one or more steps or apparatuses and may include sub-steps as well as sub-apparatuses. All conjunctions used should be understood in the broadest sense. And the word "or" should be understood to have the definition of logical "or" rather than the definition of logical "exclusive or" unless the context clearly dictates otherwise. Further, implementation of the methods and/or apparatus of embodiments of the present invention may include performing the selected task manually, automatically, or in combination.
The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention in any way. It will be understood by those skilled in the art that various changes, substitutions and alterations can be made herein without departing from the spirit and scope of the invention as defined by the appended claims.

Claims (24)

1. An apparatus for laser lift-off of an LED epitaxial substrate, comprising:
the wafer bearing assembly comprises a movable bearing table, and the bearing table is used for bearing and fixing the LED wafer;
the cover plate assembly comprises a cover plate capable of transmitting ultraviolet light, and the cover plate is positioned above the bearing table and can move in a direction close to or far away from the bearing table so as to compress or release the LED wafer; and the number of the first and second groups,
and the laser component is used for emitting at least one laser beam, and the laser beam irradiates the LED wafer after penetrating through the cover plate and scans the LED wafer so as to strip the epitaxial substrate of the LED wafer.
2. The apparatus for laser lift-off of an LED epitaxial substrate of claim 1 wherein the LED wafer is a vertical structure LED wafer.
3. The apparatus for laser lift-off of an LED epitaxial substrate of claim 1 or 2, wherein the wafer carrier assembly further comprises:
and the heating unit is used for heating the bearing table to a preset temperature.
4. The apparatus for laser lift-off of an LED epitaxial substrate according to claim 3, wherein the predetermined temperature is 25 ℃ to 800 ℃.
5. The apparatus for laser lift-off of an LED epitaxial substrate according to claim 1 or 2, wherein a pressure within a range of 10kgf to 1000kgf is applied to the LED wafer while the cover plate is pressed against the LED wafer.
6. The apparatus for laser lift-off of an LED epitaxial substrate according to claim 1, wherein the wafer carrier assembly further comprises a first driving unit for driving the movement of the carrier table; and/or the cover plate assembly further comprises a second driving unit for driving the cover plate to move along the direction close to or far away from the bearing table.
7. The apparatus for laser lift-off of an LED epitaxial substrate of claim 1 wherein the carrying surface of the carrying stage and the side of the cover plate facing the carrying stage are both flat surfaces.
8. The apparatus for laser lift-off of an LED epitaxial substrate according to claim 1 wherein the carrier has a recess for receiving the LED wafer, the cover plate has a protrusion on a side facing the carrier, and the protrusion enters the recess and presses the LED wafer when the cover plate is moved in a direction close to the carrier.
9. The apparatus for laser lift-off of an LED epitaxial substrate of claim 8 wherein the inner wall of the recess and the outer wall of the protrusion are stepped and the step of the protrusion matches the profile and dimensions of the step of the recess.
10. The apparatus for laser lift-off of an LED epitaxial substrate according to any one of claims 7 to 9, wherein the susceptor further has a plurality of suction holes for vacuum suction of the LED wafer.
11. The apparatus according to claim 1, wherein the carrier assembly further comprises a third driving unit and at least three pins disposed in the carrier, the vertices of the at least three pins are not collinear, and the third driving unit is configured to drive the pins to lift up or lower down the LED wafer.
12. The apparatus for laser lift-off of an LED epitaxial substrate of claim 1, wherein the laser assembly comprises:
the light source module is used for emitting laser beams with preset wavelengths;
the light splitting module is used for splitting the laser beam emitted by the light source module into at least two laser beams with the same energy distribution; and the number of the first and second groups,
and the shaping module is used for shaping at least two laser beams and irradiating the laser beams onto the LED wafer.
13. An apparatus for laser lift-off of an LED epitaxial substrate according to claim 12, wherein the laser assembly further comprises:
and the scanning projection module is used for controlling the laser beam to move along at least one preset track so as to scan the LED wafer.
14. An apparatus for laser lift-off of an LED epitaxial substrate according to claim 12, wherein the laser assembly further comprises:
and the splicing module is used for splicing the shaped at least two laser beams and irradiating the laser beams onto the LED wafer.
15. The apparatus for laser lift-off of an LED epitaxial substrate according to any one of claims 12 to 14, wherein the light source module is an excimer laser or a DPSS laser, and the predetermined wavelength is 150nm to 330nm.
16. The apparatus for laser lift-off of an LED epitaxial substrate according to any of claims 12 to 14, wherein the spot of the laser beam is a point-like spot or a line-like spot.
17. The apparatus for laser lift-off of an LED epitaxial substrate of claim 1, further comprising:
the first image detection assembly is used for detecting the marks on the LED wafer so as to acquire the position information of the LED wafer; and the number of the first and second groups,
and the second image detection assembly is used for monitoring the stripping condition of the epitaxial substrate of the LED wafer in real time.
18. The apparatus for laser lift-off of LED epitaxial substrates of claim 1 wherein the material of the carrying surface of the stage is one or more of anodized aluminum, stainless steel, silicon carbide or aluminum nitride.
19. The apparatus for laser lift-off of an LED epitaxial substrate according to claim 1, wherein the material of the cover plate is high-purity quartz, sapphire or aluminum nitride crystal.
20. The apparatus for laser lift-off of an LED epitaxial substrate of claim 1, further comprising:
and the control assembly is used for controlling the bearing table and/or the cover plate to move.
21. The apparatus for laser lift-off of an LED epitaxial substrate of claim 1, further comprising:
and the upper and lower wafer assemblies are used for placing the LED wafer on the bearing table and sequentially taking down the stripped epitaxial substrate and the LED wafer.
22. A method for laser lift-off of an LED epitaxial substrate using the apparatus for laser lift-off of an LED epitaxial substrate according to any one of claims 1 to 21, comprising:
placing the LED wafer on a bearing table;
the cover plate moves along the direction close to the bearing table until the LED wafer is pressed tightly;
the bearing table moves to realize the alignment of the LED wafer and the laser assembly;
the laser assembly emits at least one laser beam and scans the LED wafer to strip the epitaxial substrate of the LED wafer; and the number of the first and second groups,
and the cover plate moves along the direction far away from the bearing table, the LED wafer is released, and the stripped epitaxial substrate and the stripped LED wafer are taken down from the bearing table in sequence.
23. The method of laser lift off an LED epitaxial substrate of claim 22 wherein a heating unit heats the susceptor to a predetermined temperature before the laser assembly emits at least one laser beam and scans the LED wafer.
24. The method of laser lift off of an LED epitaxial substrate of claim 22 or 23 wherein the stage moves along a predetermined trajectory to cause the laser beam to scan the LED wafer; or the laser beam moves along the preset track to scan the LED wafer.
CN202110796299.6A 2021-07-14 2021-07-14 Device and method for stripping LED epitaxial substrate by laser Pending CN115621372A (en)

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