Laser lift-off method and mass transfer method

Abstract

The present application relates to a laser lift-off method and a mass transfer method, the laser lift-off method comprising: making a retaining wall, the retaining wall is formed on a growth substrate, and the retaining wall separates a plurality of light-emitting elements on the growth substrate one by one; providing a temporary substrate, and coating an adhesive layer on the temporary substrate, the adhesive layer being mixed with a gas adsorption material; bonding a plurality of light-emitting elements on the growth substrate to the adhesive layer on the temporary substrate; irradiating a plurality of light-emitting elements with laser light on the side of the growth substrate facing away from the light-emitting elements. By setting a retaining wall to block nitrogen from diffusing to adjacent light-emitting elements, and using the gas adsorption material in the adhesive layer to adsorb nitrogen, when laser irradiation is performed, the nitrogen generated by the light-emitting element is blocked by the retaining wall and adsorbed by the gas adsorption material, thereby reducing or even eliminating the influence of nitrogen on adjacent light-emitting elements, and preventing the adjacent light-emitting elements from being tilted or even flipped by nitrogen.

Description

Technical Field

[0001] The present application relates to the technical field of laser lift-off in mass transfer, and in particular to a laser lift-off method and a mass transfer method. Background Art

[0002] At present, a key technology facing Micro-LED (Micro-light-emitting diode) is to transfer Micro-LED chips to the display backplane through mass transfer. In this process, the Micro-LED chips grown on the substrate need to be peeled off and then transferred to a temporary substrate.

[0003] The peeling of Micro-LED chips on the growth substrate often uses the laser lift off (LLO) method. The peeling principle is that the gallium nitride (GaN) at the bottom of the chip is decomposed into nitrogen (N2) and liquid gallium (Ga) under laser irradiation, thereby separating the chip from the growth substrate.

[0004] Currently, in order to improve production efficiency, multiple chips are often peeled at the same time. However, the nitrogen generated will diffuse in all directions and will tilt or even flip other chips around.

[0005] Therefore, how to prevent nitrogen from diffusing around and affecting surrounding chips is an urgent problem to be solved. Summary of the invention

[0006] In view of the above-mentioned deficiencies in the prior art, the purpose of the present application is to provide a laser lift-off method and a mass transfer method, aiming to solve the problem of how to prevent nitrogen from diffusing to the surroundings and affecting the surrounding chips.

[0007] A laser lift-off method comprises: making a retaining wall, wherein the retaining wall is formed on a growth substrate and separates a plurality of light-emitting elements on the growth substrate one by one; providing a temporary substrate and coating an adhesive layer on the temporary substrate, wherein the adhesive layer is mixed with a gas adsorption material; bonding the plurality of light-emitting elements on the growth substrate to the adhesive layer on the temporary substrate; and irradiating the plurality of light-emitting elements with laser on a side of the growth substrate facing away from the light-emitting elements.

[0008] By setting up a retaining wall to block the diffusion of nitrogen to adjacent light-emitting elements, and using the gas adsorption material in the adhesive layer to adsorb the nitrogen, during laser irradiation, the nitrogen generated by the light-emitting element is blocked by the retaining wall and adsorbed by the gas adsorption material, thereby reducing or even eliminating the influence of nitrogen on adjacent light-emitting elements, and preventing the adjacent light-emitting elements from being tilted or even flipped by nitrogen.

[0009] Optionally, the making of the retaining wall includes: taking the surface of the growth substrate as a reference, making the height of the retaining wall equal to the height of the light-emitting element. During the laser lift-off process, the adhesive layer on the temporary substrate is connected to the light-emitting element and the retaining wall at the same time, so that two adjacent light-emitting elements are completely isolated from each other, and the nitrogen generated by one light-emitting element will not diffuse to the adjacent light-emitting element, thereby completely avoiding the influence of nitrogen on the light-emitting element.

[0010] Optionally, the making of the retaining wall comprises: stacking a functional layer on the growth substrate, the functional layer being equal in height to the light emitting elements and filling the gaps between the plurality of light emitting elements; processing the functional layer, removing the portion connected to the light emitting elements, and leaving the portion between two adjacent light emitting elements to form the retaining wall. This process is mature and easy to make.

[0011] Optionally, the light emitting element includes an epitaxial layer, a first electrode and a second electrode, the epitaxial layer is connected to the growth substrate, and the first electrode and the second electrode are arranged at intervals on a surface of the epitaxial layer facing away from the growth substrate.

[0012] Optionally, the specific surface area of ​​the gas adsorption material is greater than a preset value. Using a gas adsorption material with a specific surface area greater than the preset value can have a better adsorption effect and can better adsorb gas, so that the nitrogen generated during laser stripping can be fully adsorbed and the amount of diffused gas can be reduced.

[0013] Optionally, irradiating the plurality of light-emitting elements with laser light on one side of the growth substrate comprises: providing a mask, the mask comprising a plurality of opaque regions and a plurality of translucent regions; arranging the mask on the side of the growth substrate facing away from the light-emitting elements, one of the two adjacent light-emitting elements corresponding to the translucent region, and the other light-emitting element corresponding to the opaque region; irradiating the mask with laser light on the side of the mask facing away from the growth substrate. By setting a special structure of the mask, a light-emitting element corresponds to a translucent region, and an adjacent light-emitting element corresponds to an opaque region, so that two adjacent light-emitting elements will not be laser-stripped at the same time, thereby avoiding the influence of nitrogen diffusion on the adjacent light-emitting elements when the two adjacent light-emitting elements are laser-stripped at the same time.

[0014] Optionally, irradiating the plurality of light-emitting elements with laser light on one side of the growth substrate further includes: after the laser light passes through the light-transmitting area to irradiate the light-emitting element, moving the mask so that another light-emitting element adjacent to the light-emitting element corresponds to the light-transmitting area; irradiating the mask with laser light on the side of the mask facing away from the growth substrate so that the light-emitting element that has not been irradiated with laser light before is irradiated with laser light. This arrangement can avoid the influence of nitrogen generated by the light-emitting element on the adjacent light-emitting element when the adjacent light-emitting elements are irradiated with laser light at the same time.

[0015] Optionally, a plurality of the light-emitting elements are arranged in an array on the growth substrate, and a plurality of the opaque regions are connected to form a "cross" or "X" shape. By arranging the opaque regions to form a "cross" or "X" shape, two adjacent light-emitting elements will not be irradiated by the laser at the same time, and the structure is simple.

[0016] Optionally, the laser lift-off method further comprises: after all the light-emitting elements are irradiated by the laser, lift-off the growth substrate.

[0017] Based on the same inventive concept, the present application also provides a mass transfer method, including the laser lift-off method described in any one of the aforementioned embodiments.

[0018] The mass transfer method of the present application sets a retaining wall to block the diffusion of nitrogen to adjacent light-emitting elements, and uses the gas adsorption material in the adhesive layer to adsorb the nitrogen. When laser irradiation is performed, the nitrogen generated by the light-emitting element is blocked by the retaining wall and adsorbed by the gas adsorption material, thereby reducing or even eliminating the influence of nitrogen on adjacent light-emitting elements, and preventing the adjacent light-emitting elements from being tilted or even flipped by the nitrogen. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 A flowchart of a laser lift-off method according to an embodiment;

[0020] Figure 2 A structural diagram of a step of a laser lift-off method according to an embodiment;

[0021] Figure 3 A structural diagram of a step of a laser lift-off method according to an embodiment;

[0022] Figure 4 A structural diagram of a step of a laser lift-off method according to an embodiment;

[0023] Figure 5 A structural diagram of a step of a laser lift-off method according to an embodiment;

[0024] Figure 6A structural diagram of a step of a laser lift-off method according to an embodiment;

[0025] Figure 7 A structural diagram of a step of a laser lift-off method according to an embodiment;

[0026] Figure 8 A structural diagram of a step of a laser lift-off method according to an embodiment.

[0027] Description of reference numerals:

[0028] 10- Growth substrate;

[0029] 20-light emitting element, 21-epitaxial layer, 22-first electrode, 23-second electrode;

[0030] 30- retaining wall;

[0031] 40-transient substrate;

[0032] 50-adhesive layer;

[0033] 60-mask, 65-light-transmitting area. DETAILED DESCRIPTION

[0034] In order to facilitate the understanding of the present application, the present application will be described more fully below with reference to the relevant drawings. The preferred embodiments of the present application are given in the drawings. However, the present application can be implemented in many different forms and is not limited to the embodiments described herein. On the contrary, the purpose of providing these embodiments is to make the disclosure of the present application more thoroughly and comprehensively understood.

[0035] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art to which this application belongs. The terms used herein in the specification of this application are only for the purpose of describing specific embodiments and are not intended to limit this application.

[0036] The peeling of Micro-LED chips on the growth substrate often uses the laser lift off (LLO) method. The peeling principle is that the gallium nitride (GaN) at the bottom of the chip is decomposed into nitrogen (N2) and liquid gallium (Ga) under laser irradiation, thereby separating the chip from the growth substrate.

[0037] Currently, in order to improve production efficiency, multiple chips are often peeled at the same time. However, the nitrogen generated will diffuse in all directions and will tilt or even flip other chips around.

[0038] Therefore, how to prevent nitrogen from diffusing around and affecting surrounding chips is an urgent problem to be solved.

[0039] Based on this, the present application hopes to provide a solution that can solve the above-mentioned technical problems, the details of which will be described in the subsequent embodiments.

[0040] Please refer to Figure 1 , the present application provides a laser lift-off method, comprising:

[0041] S10, manufacturing a retaining wall, wherein the retaining wall is formed on the growth substrate, and the retaining wall separates a plurality of light emitting elements on the growth substrate one by one;

[0042] S20, providing a transient substrate, and coating an adhesive layer on the transient substrate, wherein the adhesive layer is mixed with a gas adsorption material;

[0043] S30, bonding the plurality of light-emitting elements on the growth substrate to the adhesive layer on the transient substrate;

[0044] S40, irradiating a plurality of light emitting elements with laser light on a side of the growth substrate facing away from the light emitting elements.

[0045] For details, please refer to Figure 2 and Figure 3 Before step S10, a number of light-emitting elements 20 have been grown on the growth substrate 10. The growth substrate 10 may be made of sapphire, gallium arsenide or the like. The light-emitting element 20 may be a Micro-LED chip, and the Micro-LED chip of the light-emitting element 20 includes an epitaxial layer 21, a first electrode 22 and a second electrode 23. The epitaxial layer 21 is connected to the growth substrate 10, and the first electrode 22 and the second electrode 23 are arranged at intervals on the surface of the epitaxial layer 21 facing away from the growth substrate 10. A plurality of light-emitting elements 20 may be arranged in an array on the growth substrate 10 to be used as a display screen or a backlight module. For how to grow the light-emitting element 20 on the growth substrate 10, reference may be made to the prior art, and this application does not impose any specific restrictions.

[0046] In step S10, when making the retaining wall 30, a spacing distance can be provided between the retaining wall 30 and two adjacent light-emitting elements 20. Optionally, the retaining wall 30 is located in the middle position between two adjacent light-emitting elements 20. When a plurality of light-emitting elements 20 are arranged in an array of multiple rows and columns on the growth substrate 10, the retaining wall 30 is in a shape of multiple rows and columns crisscrossed, and two adjacent light-emitting elements 20 at any position are separated by the retaining wall 30. In other words, the plurality of light-emitting elements 20 on the growth substrate 10 are separated one by one by the retaining wall 30. The material of the retaining wall 30 can be silicon oxide (SiOx), silicon nitride (SiNx), organic material, etc. The plurality of light-emitting elements 20 are separated one by one by the retaining wall 30. When laser stripping is performed, the nitrogen generated by one of the light-emitting elements 20 is blocked by the retaining wall 30 during diffusion, which can reduce or even avoid the influence on the adjacent light-emitting elements 20, so that the light-emitting element 20 will not be tilted or even flipped by the nitrogen.

[0047] Combination Figure 2 , Figure 3 and Figure 5 In one embodiment, when making the retaining wall 30, the height of the retaining wall 30 is made equal to the height of the light-emitting element 20, with the surface of the growth substrate 10 as a reference. The height of the light-emitting element 20 is the total height of the epitaxial layer 21 and the first electrode 22 (or the second electrode 23). Since the retaining wall 30 is equal to the height of the light-emitting element 20, when the laser stripping process is performed, and the adhesive layer 50 on the temporary substrate 40 is connected to the light-emitting element 20 and the retaining wall 30 at the same time, the two adjacent light-emitting elements 20 are completely isolated, and the nitrogen generated by one light-emitting element 20 will not diffuse to the area where the adjacent light-emitting element 20 is located, thereby completely avoiding the influence of nitrogen on the light-emitting element 20.

[0048] In other embodiments, the height of the retaining wall 30 may be slightly lower than that of the light emitting element 20 , which can also prevent the nitrogen from diffusing to the adjacent light emitting element 20 .

[0049] In one embodiment, please refer to Figure 2 , making the retaining wall 30, including: stacking a functional layer (not shown in the figure) on the growth substrate 10, the functional layer is the same height as the light-emitting element 20 and fills the gaps between the multiple light-emitting elements 20; processing the functional layer, removing the part connected to the light-emitting element 20, leaving the part located between two adjacent light-emitting elements 20 to form the retaining wall 30.

[0050] Specifically, the functional layer can be deposited on the growth substrate 10 by a chemical vapor deposition (CVD) process, and the material of the functional layer can be silicon oxide (SiOx), silicon nitride (SiNx), organic materials, etc. The pattern of the retaining wall 30 can be defined by a photomask, and then the retaining wall 30 can be formed by a photolithography process of exposure, development and etching. This process is mature and easy to manufacture. If the functional layer is an inorganic material, an etching process can also be used to remove the excess part to form the retaining wall 30.

[0051] Please refer to Figure 1 , Figure 4 and Figure 5 In step S20, the material of the temporary substrate 40 can be glass, sapphire, etc. The adhesive layer 50 is an organic material, and a gas adsorbent material is mixed in the adhesive layer 50, and the gas adsorbent material is used to adsorb nitrogen. The gas adsorbent material can specifically be zeolite molecular sieve particles, activated carbon particles, activated alumina particles, etc. The temporary substrate 40 and the adhesive layer 50 are used to transfer the multiple light-emitting elements 20 on the growth substrate 10 to the circuit backplane.

[0052] The gas adsorption material has a high specific surface area. In other words, the specific surface area of ​​the gas adsorption material is greater than a preset value, which is the specific surface area of ​​a conventional gas adsorption material. The use of a gas adsorption material with a specific surface area greater than the preset value can have a better adsorption effect and can better adsorb gas, so that the nitrogen generated during laser stripping can be fully adsorbed, reducing the amount of diffused gas.

[0053] When the adhesive layer 50 is bonded to the plurality of light emitting elements 20, for the embodiment in which the height of the retaining wall 30 is equal to the height of the light emitting element 20, the adhesive layer 50 is also bonded to the retaining wall 30. Thus, the region where each light emitting element 20 is located is surrounded by the retaining wall 30, the growth substrate 10, and the transient substrate 40 to form a closed space. When the light emitting element 20 is laser-stripped, the generated nitrogen is in the closed space and does not diffuse to other locations. The nitrogen is then absorbed by the gas adsorption material in the adhesive layer 50, which can completely avoid the influence of nitrogen on other light emitting elements 20.

[0054] In one embodiment, please refer to Figure 1 and Figure 6 In step S40, irradiating the plurality of light emitting elements 20 with laser light on one side of the growth substrate 10 includes:

[0055] Providing a mask 60, the mask 60 comprising a plurality of opaque regions and a plurality of translucent regions 65;

[0056] The mask 60 is disposed on the side of the growth substrate 10 facing away from the light emitting element 20, one of the two adjacent light emitting elements 20 corresponds to the light-transmitting area 65, and the other light emitting element 20 corresponds to the opaque area;

[0057] The laser is irradiated toward the mask 60 at the side of the mask 60 facing away from the growth substrate 10 .

[0058] In this embodiment, the laser can penetrate the light-transmitting area 65 of the mask 60 to irradiate the growth substrate 10 and the light-emitting element 20, so that the light-emitting element 20 corresponding to the light-transmitting area 65 reacts and can be peeled off. Since the opaque area of ​​the mask 60 cannot penetrate the laser, the light-emitting element 20 corresponding to the opaque area cannot react with the laser and cannot be peeled off.

[0059] During laser lift-off, nitrogen generated by one light emitting element 20 is most likely to affect the light emitting elements 20 adjacent thereto.

[0060] By setting a special structure of the mask plate 60, a light-emitting element 20 corresponds to the light-transmitting area 65, and the adjacent light-emitting element 20 corresponds to the opaque area, so that the two adjacent light-emitting elements 20 will not be laser-stripped at the same time, thereby avoiding the influence of nitrogen diffusion on the adjacent light-emitting elements 20 when the two adjacent light-emitting elements 20 are laser-stripped at the same time.

[0061] In other embodiments, each light-emitting element 20 may correspond to a light-transmitting area 65, and multiple light-emitting elements 20 may be irradiated with laser at the same time. Since the retaining wall 30 and the gas adsorption material are provided, the diffusion of nitrogen between two adjacent light-emitting elements 20 and the nitrogen generated by the absorption reaction can be blocked, so that the nitrogen will hardly diffuse to affect the adjacent light-emitting elements 20, and the requirements can be met when the product requirements are not high.

[0062] In an embodiment where a plurality of light emitting elements 20 are arranged in an array on the growth substrate 10 and two adjacent light emitting elements 20 are not irradiated with laser light at the same time, the shape of the mask 60 can be designed as required, for example: Figure 7 , multiple opaque areas are connected and form a "cross" shape; for example: please refer to Figure 8 , multiple opaque areas are connected and form an "X" shape. Among them, multiple opaque areas are connected so that the mask 60 can form an integral plate, and multiple transparent areas 65 can be hollow holes opened on the mask 60. By setting the opaque areas to form a "cross" shape or an "X" shape, two adjacent light-emitting elements 20 will not be irradiated by the laser at the same time, and the structure is simple. The shape of the opaque area of ​​the mask 60 can also be set to other shapes as needed, which are not enumerated here.

[0063] In one embodiment, please refer to Figure 6 , irradiating a plurality of light emitting elements 20 with laser light on one side of the growth substrate 10, further comprising: after the laser light irradiates the light emitting element 20 through the light-transmitting region 65, moving the mask 60 so that another light emitting element 20 adjacent to the light emitting element 20 corresponds to the light-transmitting region 65;

[0064] The laser is irradiated toward the mask 60 at the side of the mask 60 facing away from the growth substrate 10 , so that the light emitting elements 20 that have not been irradiated with the laser are irradiated with the laser.

[0065] That is to say, since two adjacent light emitting elements 20 are not laser irradiated at the same time, after one of the light emitting elements 20 is laser irradiated, the other light emitting element 20 needs to be laser irradiated. At this time, it is only necessary to move the mask 60 so that the light-transmitting area 65 corresponds to the light emitting element 20 that has not been laser irradiated, and the corresponding light-opaque area corresponds to the light emitting element 20 that has been laser irradiated before. The laser irradiation of all the light emitting elements 20 is changed from completing the laser irradiation of all the light emitting elements 20 at one time to completing the laser irradiation of all the light emitting elements 20 in multiple times. Such a setting can avoid the influence of nitrogen generated by the light emitting element 20 on the adjacent light emitting elements 20 when the adjacent light emitting elements 20 are laser irradiated at the same time.

[0066] Please refer to Figure 1 and Figure 6 After step S40, the laser lift-off method of the present application further includes: after all the light-emitting elements 20 are irradiated by the laser, lift-off the growth substrate 10.

[0067] After all the light emitting elements 20 are irradiated with laser for multiple times, all the light emitting elements 20 react with the laser and are in a state that can be peeled off. By peeling off the growth substrate 10, all the light emitting elements 20 are transferred to the temporary substrate 40, and the retaining wall 30 will not react with the laser, and the retaining wall 30 will remain on the growth substrate 10, thereby not affecting the subsequent process of transferring multiple light emitting elements 20 to the circuit backplane by the temporary substrate 40.

[0068] The present application sets up steps S10-S40, sets up a retaining wall 30 to block the diffusion of nitrogen to the adjacent light-emitting element 20, and uses the gas adsorption material in the adhesive layer 50 to adsorb the nitrogen. When laser irradiation is performed, the nitrogen generated by the light-emitting element 20 is blocked by the retaining wall 30 and adsorbed by the gas adsorption material, thereby reducing or even eliminating the influence of nitrogen on the adjacent light-emitting element 20, and preventing the adjacent light-emitting element 20 from being tilted or even flipped by the nitrogen.

[0069] Please refer to Figures 1 to 8 The embodiment of the present application also provides a mass transfer method, including the laser lift-off method in any of the above embodiments. After the laser lift-off method of the present application completes step S40, the growth substrate 10 and the retaining wall 30 thereon are peeled off, and then the peeled multiple light-emitting elements 20 are transferred to the circuit backplane through the temporary substrate 40 and the adhesive layer 50 thereon, and then the temporary substrate 40 and the adhesive layer 50 are removed, and the mass transfer process can be completed.

[0070] The mass transfer method of the present application sets a retaining wall 30 to block the diffusion of nitrogen to the adjacent light-emitting element 20, and uses the gas adsorption material in the adhesive layer 50 to adsorb the nitrogen. When laser irradiation is performed, the nitrogen generated by the light-emitting element 20 is blocked by the retaining wall 30 and adsorbed by the gas adsorption material, thereby reducing or even eliminating the influence of nitrogen on the adjacent light-emitting element 20, and preventing the adjacent light-emitting element 20 from being tilted or even flipped by the nitrogen.

[0071] It should be understood that the application of the present application is not limited to the above examples. For ordinary technicians in this field, improvements or changes can be made based on the above description. All these improvements and changes should fall within the scope of protection of the claims attached to this application.

Claims

1. A laser lift-off method, characterized in that: include: Making a retaining wall, wherein the retaining wall is formed on the growth substrate, and the retaining wall separates a plurality of light emitting elements on the growth substrate one by one; Providing a temporary substrate, and coating an adhesive layer on the temporary substrate, wherein the adhesive layer is mixed with a gas adsorption material; bonding the plurality of light emitting elements on the growth substrate to the adhesive layer on the temporary substrate; The plurality of light emitting elements are irradiated with laser light at a side of the growth substrate facing away from the light emitting elements.

2. The laser lift-off method according to claim 1, characterized in that: The method of making a retaining wall comprises: The height of the retaining wall is made equal to the height of the light emitting element based on the surface of the growth substrate.

3. The laser lift-off method according to claim 1 or 2, characterized in that: The method of making a retaining wall comprises: stacking a functional layer on the growth substrate, wherein the functional layer is at the same height as the light-emitting elements and fills the gaps between the plurality of light-emitting elements; The functional layer is processed to remove the portion connected to the light emitting element and leave the portion located between two adjacent light emitting elements to form the retaining wall.

4. The laser lift-off method according to claim 1, wherein: The light emitting element comprises an epitaxial layer, a first electrode and a second electrode. The epitaxial layer is connected to the growth substrate. The first electrode and the second electrode are arranged at intervals on a surface of the epitaxial layer facing away from the growth substrate.

5. The laser lift-off method according to claim 1, wherein: The specific surface area of ​​the gas adsorption material is greater than a preset value.

6. The laser lift-off method according to claim 1, wherein: The step of irradiating the plurality of light emitting elements with laser light on one side of the growth substrate comprises: Providing a mask, wherein the mask includes a plurality of opaque regions and a plurality of translucent regions; The mask is arranged on a side of the growth substrate facing away from the light-emitting element, one of two adjacent light-emitting elements corresponds to the light-transmitting area, and the other light-emitting element corresponds to the opaque area; The mask is irradiated with laser light at a side of the mask facing away from the growth substrate.

7. The laser lift-off method according to claim 6, wherein: The step of irradiating the plurality of light emitting elements with laser light on one side of the growth substrate further comprises: After the laser irradiates the light-emitting element through the light-transmitting area, the mask is moved so that another light-emitting element adjacent to the light-emitting element corresponds to the light-transmitting area; The laser is irradiated toward the mask at a side of the mask facing away from the growth substrate, so that the light emitting elements which have not been irradiated by the laser are irradiated by the laser.

8. The laser lift-off method according to claim 6, wherein: The plurality of light-emitting elements are arranged in an array on the growth substrate, and the plurality of light-proof regions are connected to form a "cross" shape or an "X" shape.

9. The laser lift-off method according to claim 1, wherein: The laser lift-off method further comprises: After all the light emitting elements are irradiated with laser, the growth substrate is peeled off.

10. A method for mass transfer, characterized in that: The method comprises the laser lift-off method as claimed in any one of claims 1 to 9.

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