A mass transfer method and apparatus

Abstract

This invention relates to the field of mass transfer technology, specifically to a mass transfer method and apparatus. The method includes providing a growth substrate on which multiple independent light-emitting chips are arranged in an array; spin-coating a first photoresist layer between the light-emitting chips; spin-coating a second photoresist layer on the first photoresist layer; the sum of the thicknesses of the first and second photoresists not exceeding the electrodes of the light-emitting chips; removing a portion of the second photoresist between adjacent light-emitting chips, as well as all of the first photoresist; and providing a driving backplate, aligning the side of the growth substrate with the multiple light-emitting chips with the driving backplate; and using a laser to peel the light-emitting chips from the growth substrate and bond them to the driving backplate. This method effectively prevents debris generated under laser irradiation from flying out by wrapping the sidewalls of the light-emitting chips with the second photoresist, thus effectively improving the transfer yield.

Description

Technical Field

[0001] This invention relates to the field of mass transfer technology, and more specifically, to a mass transfer method and apparatus. Background Technology

[0002] Compared to the mature and mass-produced LCD (Liquid Crystal Display) and OLED (Organic Light Emitting Display) technologies, MicroLED (Micro Light-Emitting Diode) is gradually becoming the preferred choice for ultra-high-definition displays due to its superior performance in contrast ratio, response time, wide viewing angle, power consumption, device lifespan, and color gamut. It may even dominate the display technology field in the future. However, MicroLED currently faces challenges such as high process technology requirements, a high rate of production defects, and difficulties in reducing manufacturing costs, all of which hinder its goal of mass production and large-scale commercialization.

[0003] Mass transfer is a critical process step. Currently, laser direct transfer is widely used. However, since a passivation layer is usually placed on the outer side of the MicroLED chip to protect it from damage, a lot of debris is generated during the laser process when the chip is peeled off from the growth substrate. This debris will affect the bonding effect between the chip and the driver backplane, resulting in a decrease in the mass transfer yield. Summary of the Invention

[0004] The purpose of this invention is to provide a mass transfer method and apparatus to reduce passivation layer debris contamination and improve mass transfer yield.

[0005] To achieve the above objectives, the technical solutions adopted in the embodiments of the present invention are as follows:

[0006] In a first aspect, a mass transfer method is provided, the method comprising: providing a growth substrate on which multiple independent light-emitting chips are arranged in an array; spin-coating a first photoresist layer between the multiple light-emitting chips; spin-coating a second photoresist layer on the first photoresist layer, wherein the sum of the thicknesses of the first photoresist and the second photoresist layer is not higher than the electrodes of the light-emitting chips; removing a portion of the second photoresist layer between adjacent light-emitting chips and all of the first photoresist layer; providing a driving backplate; aligning the side of the growth substrate on which the multiple light-emitting chips are disposed with the driving backplate; and peeling the light-emitting chips off the growth substrate and bonding them to the driving backplate using a laser.

[0007] In a second aspect, a mass transfer apparatus includes: a growth substrate on which multiple independent light-emitting chips are arranged in an array; a second photoresist, which wraps around the outer wall of each light-emitting chip and is spaced apart from the growth substrate by a first predetermined distance, and the second photoresist between adjacent light-emitting chips is spaced apart by a second predetermined distance; when the light-emitting chips are peeled off from the growth substrate by a laser and bonded to a driving backplane, the second photoresist located on the outer wall of the light-emitting chip contains the generated debris.

[0008] This invention provides a mass transfer method and apparatus, comprising: providing a growth substrate on which multiple independent light-emitting chips are arranged in an array; spin-coating a first photoresist layer between the multiple light-emitting chips; spin-coating a second photoresist layer on the first photoresist layer; the sum of the thicknesses of the first and second photoresists not exceeding the electrodes of the light-emitting chips; removing a portion of the second photoresist between adjacent light-emitting chips and all of the first photoresist; providing a driving backplate; aligning the side of the growth substrate with the multiple light-emitting chips with the driving backplate; and using a laser to peel the light-emitting chips from the growth substrate and bond them to the driving backplate. This solution effectively prevents debris generated under laser action by wrapping the sidewalls of the light-emitting chips with the second photoresist, and because the entire first photoresist layer is removed, the light-emitting chips are not adhered to the growth substrate during transfer, thus not affecting the transfer effect and improving the transfer yield.

[0009] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, preferred embodiments are described below in detail with reference to the accompanying drawings. Attached Figure Description

[0010] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as a limitation on the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0011] Figure 1 A schematic flowchart of a mass transfer method provided by an embodiment of the present invention is shown.

[0012] Figure 2 A schematic diagram of a growth substrate provided in an embodiment of the present invention is shown.

[0013] Figure 3 A schematic diagram of the structure of a light-emitting chip provided in an embodiment of the present invention is shown.

[0014] Figure 4This diagram illustrates a spin-coating of a first photoresist according to an embodiment of the present invention.

[0015] Figure 5 This diagram illustrates a spin-coating of a second photoresist according to an embodiment of the present invention.

[0016] Figure 6 This diagram illustrates a post-adhesive removal process according to an embodiment of the present invention.

[0017] Figure 7 This diagram illustrates a mass transfer method provided by an embodiment of the present invention.

[0018] Figure 8 This diagram illustrates the state after a mass transfer, as provided in an embodiment of the present invention.

[0019] Figure 9 This diagram illustrates another example of adhesive removal provided by an embodiment of the present invention.

[0020] Illustration:

[0021] 100 - Growth substrate; 200 - Light-emitting chip; 300 - First photoresist; 400 - Second photoresist; 500 - Driving backplane. Detailed Implementation

[0022] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. The components of the embodiments of the present invention described and shown in the accompanying drawings can generally be arranged and designed in various different configurations. Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

[0023] It should be noted that similar reference numerals and letters in the following figures indicate similar items; therefore, once an item is defined in one figure, it does not need to be further defined and explained in subsequent figures. Furthermore, in the description of this invention, terms such as "first," "second," etc., are used only to distinguish descriptions and should not be construed as indicating or implying relative importance.

[0024] Please refer to Figure 1 This is a flowchart illustrating a mass transfer method provided in an embodiment of the present invention. The method includes:

[0025] S110 provides a growth substrate on which multiple independent light-emitting chips are arranged in an array.

[0026] like Figure 2 The diagram shows a schematic representation of a growth substrate 100 according to an embodiment of the present invention. Multiple independent light-emitting chips 200 are arrayed on the growth substrate 100. That is, the growth substrate 100 can be a sapphire substrate, a silicon substrate, etc. An epitaxial structure is first grown on the growth substrate 100, and then the epitaxial structure is cut into multiple independent light-emitting chips 200. The light-emitting chips 200 can be red light-emitting chips that emit red light, green light-emitting chips that emit green light, and blue light-emitting chips that emit blue light, etc. Furthermore, the light-emitting chips 200 can be vertical structure light-emitting chips or flip-chip structure light-emitting chips. A vertical structure light-emitting chip means that the electrodes are located on both sides of the epitaxial structure, while a flip-chip structure light-emitting chip means that the electrodes are located on the same side of the epitaxial structure.

[0027] Please refer to Figure 3 The diagram shown is a schematic representation of a light-emitting chip 200 according to an embodiment of the present invention. The light-emitting chip 200 includes at least an N-type gallium nitride layer (N-GaN), a light-emitting layer (Multiple Quantum Well, MQW), a P-type gallium nitride layer (P-GaN), electrodes (including P-Pad and N-Pad), and a passivation layer (which may be, but is not limited to, an insulating protective layer such as SiO2). Figure 3 The light-emitting chip 200 shown is a flip-chip structure, with its N-Pad and P-Pad located on the same side of the epitaxial structure. The N-type gallium nitride layer, the light-emitting layer, and the P-type gallium nitride layer are stacked sequentially. The N-Pad is connected to the N-type gallium nitride layer, and the P-Pad is connected to the P-type gallium nitride layer. The passivation layer covers the sidewalls of the N-type gallium nitride layer, the light-emitting layer, and the P-type gallium nitride layer, and exposes the surfaces of the N-Pad and P-Pad.

[0028] S120, spin-coating a first photoresist layer between the multiple light-emitting chips.

[0029] like Figure 4The diagram shown is a schematic of a spin-coating first photoresist 300 provided in an embodiment of the present invention. Specifically, the first photoresist 300 is spin-coated into the gaps between the light-emitting chips 200 on the growth substrate 100. The thinner the first photoresist 300, the better, preferably not exceeding 1 μm, because this layer of first photoresist 300 will be removed in subsequent processes, preventing the light-emitting chips 200 from adhering to the growth substrate 100 and facilitating transfer. The thinner first photoresist 300 facilitates removal and allows for the deposition of a thicker second photoresist 400 on top of it. The second photoresist 400 will remain on the outer wall of the light-emitting chips 200 during mass transfer. Furthermore, the thicker second photoresist 400 can cover a larger area of ​​the outer wall of the light-emitting chips 200, allowing debris generated during laser stripping of the light-emitting chips 200 to be contained within the second photoresist 400, preventing it from scattering and affecting the bonding effect of adjacent light-emitting chips 200.

[0030] S130, spin-coating a second photoresist onto the first photoresist, wherein the sum of the thicknesses of the first and second photoresists is not higher than the electrodes of the light-emitting chip.

[0031] like Figure 5 As shown, after the first photoresist 300 has cured, a second photoresist 400 is spin-coated onto it. To avoid poor soldering and open circuits between the light-emitting chip 200 and the driving backplane, the combined thickness of the first photoresist 300 and the second photoresist 400 is no greater than the electrodes of the light-emitting chip 200. Figure 3 As can be seen, N-Pad and P-Pad are located on the same horizontal plane, so the sum of the thicknesses of the first photoresist 300 and the second photoresist 400 is not higher than the surface of N-Pad or P-Pad.

[0032] S140, the portion of the second photoresist located between adjacent light-emitting chips, and all of the first photoresist, are removed.

[0033] like Figure 6 The diagram shown is a schematic representation of a photoresist after removal, according to an embodiment of the present invention. It should be noted that the first photoresist 300 can be either a positive or negative photoresist, and the second photoresist 400 can also be either a positive or negative photoresist. For positive photoresist, after ultraviolet light exposure, the exposed portion becomes more soluble, and the exposed portion will be removed by the developer, leaving the unexposed portion. For negative photoresist, after ultraviolet light exposure, the exposed portion undergoes a cross-linking reaction and becomes insoluble; therefore, the exposed portion will remain, and the unexposed portion will be removed. Furthermore, the adhesion between the positive and negative photoresist can be adjusted according to actual needs.

[0034] When the first photoresist 300 is a positive photoresist and the second photoresist 400 is a negative photoresist, in Figure 4 When the spin-coating of the first photoresist 300 is completed, all the spin-coated first photoresist 300 needs to undergo exposure processing, and then... Figure 5 After the second photoresist 400 is coated, all the other second photoresist 400 except for the portion of the second photoresist 400 located between adjacent light-emitting chips 200 are exposed. Finally, a developer is used to remove the portion of the second photoresist 400 between adjacent light-emitting chips 200 and all the first photoresist 300.

[0035] This is because the first photoresist 300 is a positive photoresist, and after spin coating and full exposure, it is easily removed by the developer. The second photoresist 400, however, is a negative photoresist. For the areas that need to be retained—that is, the portion of the second photoresist 400 between the light-emitting chips 200—exposure causes a cross-linking reaction, making it insoluble in the developer. The unexposed portions (i.e., the portion of the second photoresist 400 between the light-emitting chips 200) can then be removed by the developer. The final result is as follows: Figure 6 The state shown means that the first photoresist 300 is completely removed, so that the second photoresist 400 maintains a certain distance from the growth substrate 100. As a result, the light-emitting chips 200 will not be affected by adhesion during mass transfer, thus improving the transfer efficiency. In addition, the second photoresist 400 covers most of the outer wall of the light-emitting chips 200 and maintains a certain distance from the second photoresist 400 on the adjacent light-emitting chips 200, so that each light-emitting chip 200 remains independent, which facilitates mass transfer.

[0036] When the first photoresist 300 is a negative photoresist and the second photoresist 400 is a positive photoresist, then in Figure 4 After spin-coating to form the first photoresist 300, no additional processing is required. Once the first photoresist 300 has cured, spin-coating can be continued to form the second photoresist 400. Then, the portion of the second photoresist 400 located between adjacent light-emitting chips 200 is exposed. Finally, a developer is used to remove the portion of the second photoresist 400 located between adjacent light-emitting chips 200, as well as all of the first photoresist 300.

[0037] In other words, since the second photoresist 400 is a positive photoresist, after the portion of the second photoresist 400 located between adjacent light-emitting chips 200 is exposed, this portion of the second photoresist 400 becomes more soluble, and the exposed portion will be removed by the developer. Furthermore, since the first photoresist 300 is a negative photoresist, its unexposed portion will be removed. Therefore, the final step of using the developer can remove both the first photoresist 300 and the exposed portion of the second photoresist 400 between adjacent light-emitting chips 200, achieving the desired effect. Figure 6 The state shown.

[0038] Furthermore, the thickness of the first photoresist 300 is less than the thickness of the second photoresist 400. This is because the first photoresist 300 is only provided so that after subsequent removal, the second photoresist 400 can maintain a certain distance from the growth substrate 100, preventing the light-emitting chip 200 from adhering to the growth substrate 100 and affecting the mass transfer effect. Simultaneously, since the thickness of the first photoresist 300 and the second photoresist 400 should ideally not exceed the electrode surface of the light-emitting chip 200, making the first photoresist 300 thinner allows the second photoresist 400 to be thicker, enabling it to cover more of the outer walls of the light-emitting chip 200. This prevents debris generated during the passivation layer transfer process from scattering everywhere, effectively improving the mass transfer efficiency.

[0039] The S150 provides a drive backplane.

[0040] S160, the side of the growth substrate with multiple light-emitting chips is aligned with the driving backplate, and the light-emitting chips are peeled off from the growth substrate and bonded to the driving backplate by laser.

[0041] Combination Figure 7 and Figure 8 This is a schematic diagram of a mass transfer provided in an embodiment of the present invention. The side of the growth substrate 100 on which multiple light-emitting chips 200 are disposed is aligned with the driving back plate 500. A laser is irradiated from the back side of the growth substrate 100 (i.e. the side away from where the light-emitting chips 200 are disposed). The laser selectively peels off the light-emitting chips 200 from the growth substrate 100 and bonds them to the driving back plate 500.

[0042] like Figure 3As shown, in order to protect the light-emitting chip 200, a passivation layer is usually provided on the outer wall of its epitaxial structure. Since the passivation layer covers the entire light-emitting chip 200 and there is usually a passivation layer in the gap between the light-emitting chips 200, during the mass transfer process, when the light-emitting chip 200 is peeled off from the growth substrate 100 by laser irradiation, the passivation layer will break and generate some debris. If no measures are taken to deal with these debris, these debris will contaminate the adhesive material on the drive backplate 500 (used to assist in the support of the light-emitting chip 200 and facilitate the bonding of the light-emitting chip 200), and will also affect the bonding of adjacent light-emitting chips 200.

[0043] In this solution, through the structural arrangement of the second photoresist 400, after the aforementioned process, it independently wraps around the outer wall of each light-emitting chip 200, covering most of the outer wall area of ​​the light-emitting chip 200. When the passivation layer is irradiated by laser and breaks, producing debris, it can wrap around most of the debris, preventing it from affecting adjacent light-emitting chips 200. The small amount of debris generated on the outer wall of the light-emitting chip 200 that is not wrapped by the second photoresist 400 will also fall onto the side of the second photoresist 400 facing the growth substrate 100. That is to say, the second photoresist 400 can not only accommodate debris generated by the passivation layer it wraps, but also accept debris generated by the passivation layer that is not wrapped by it, thus preventing contamination of the adhesive material on the drive backplane 500 and improving the mass transfer yield.

[0044] Furthermore, after the light-emitting chip 200 is bonded to the driving backplane 500, the second photoresist 400 needs to be removed.

[0045] Specifically, if the second photoresist 400 is a positive photoresist, all of the second photoresist 400 is first exposed, and then washed away with a developer; if the second photoresist 400 is a negative photoresist, it is directly washed away with a developer. The effect of removing the second photoresist 400 is as follows: Figure 9 As shown.

[0046] Furthermore, if the second photoresist 400 is doped with opaque elements, giving it opaque properties, then after the light-emitting chip 200 is bonded to the driving backplane 500, the second photoresist 400 does not need to be removed. Instead, it is retained as a barrier layer, providing an encapsulation effect for the light-emitting chip 200. This also effectively prevents light crosstalk between adjacent light-emitting chips 200, which would affect the light emission effect. Gaps between the light-emitting chips 200 are filled with adhesive material, thus saving encapsulation steps and adhesive material. The second photoresist 400 can be made opaque by doping with metal particles, carbon black, or other opaque nanomaterials. These dopants can form a barrier layer in the second photoresist 400, preventing light from penetrating it.

[0047] Therefore, the mass transfer method provided by the present invention forms a second photoresist 400 on the outer wall of the light-emitting chip 200. The second photoresist 400 is spaced at a certain distance from the growth substrate 100, which can effectively reduce the adhesion force during mass transfer. The second photoresist 400 can also effectively accommodate passivation layer debris generated during mass transfer, avoid interference with adjacent light-emitting chips 200, and improve the yield of mass transfer.

[0048] As another implementation, embodiments of the present invention also provide a mass transfer device, which is as follows: Figure 6 As shown, it includes:

[0049] A growth substrate 100 on which multiple independent light-emitting chips 200 are arranged in an array.

[0050] The second photoresist 400 coats the outer wall of each light-emitting chip 200 and is spaced from the growth substrate 100 by a first predetermined distance. The second photoresist 400 between adjacent light-emitting chips 200 is spaced by a second predetermined distance. The first and second predetermined distances are not relative in size and are only used for distinction. When the light-emitting chips 200 are peeled from the growth substrate 100 using a laser and bonded to the driving backplane 500, the second photoresist 400 on the outer wall of the light-emitting chips 200 will contain the resulting passivation layer debris.

[0051] Furthermore, the second photoresist 400 can be a negative photoresist or a positive photoresist.

[0052] The specific formation process of this mass transfer device has been described in detail in the above-mentioned mass transfer method section, and will not be repeated here.

[0053] In summary, the embodiments of the present invention provide a mass transfer method and apparatus, which includes providing a growth substrate on which multiple independent light-emitting chips are arranged in an array; a first photoresist layer is spin-coated between the multiple light-emitting chips; a second photoresist layer is spin-coated on the first photoresist layer; the sum of the thicknesses of the first and second photoresists is not higher than the electrodes of the light-emitting chips; a portion of the second photoresist between adjacent light-emitting chips and all of the first photoresist are removed; a driving backplate is provided, and the side of the growth substrate with multiple light-emitting chips is aligned with the driving backplate; the light-emitting chips are peeled off from the growth substrate and bonded to the driving backplate by laser. This solution effectively prevents debris generated under laser action from flying out by wrapping the sidewalls of the light-emitting chips with the second photoresist. At the same time, since the entire first photoresist layer is removed, the light-emitting chips are not adhered to the growth substrate during transfer, and the transfer effect is not affected, thereby improving the transfer yield.

[0054] It should be noted that, in this document, relational terms such as "first" and "second" are used only 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 a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, 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 process, method, article, or apparatus that includes said element.

[0055] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the invention should be included within the scope of protection of the invention. It should be noted that similar reference numerals and letters in the following figures denote similar items; therefore, once an item is defined in one figure, it does not need to be further defined and explained in subsequent figures.

[0056] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A mass transfer method, characterized in that, The method includes: A growth substrate is provided, on which multiple independent light-emitting chips are arranged in an array; A first photoresist layer is spin-coated between the multiple light-emitting chips; A second photoresist is spin-coated onto the first photoresist, wherein the sum of the thicknesses of the first and second photoresists is not higher than the electrodes of the light-emitting chip; The portion of the second photoresist located between adjacent light-emitting chips, as well as all of the first photoresist, is removed; Provide a drive backplane; The side of the growth substrate with multiple light-emitting chips is aligned with the driving backplate, and the light-emitting chips are peeled off from the growth substrate and bonded to the driving backplate by laser.

2. The mass transfer method as described in claim 1, characterized in that, The first photoresist is a positive photoresist, and the second photoresist is a negative photoresist. The step of spin-coating a first photoresist layer between the multiple light-emitting chips further includes: The first photoresist is fully exposed; The step of removing the portion of the second photoresist located between adjacent light-emitting chips, and all of the first photoresist, includes: Exposure is performed on the portion of the second photoresist located between adjacent light-emitting chips, excluding the portion of the second photoresist that is located on the second photoresist. The second photoresist located between adjacent light-emitting chips, as well as all of the first photoresist, are removed using a developer.

3. The mass transfer method as described in claim 1, characterized in that, The first photoresist is a negative photoresist, and the second photoresist is a positive photoresist. The step of removing the portion of the second photoresist located between adjacent light-emitting chips, and all of the first photoresist, includes: The portion of the second photoresist located between adjacent light-emitting chips is exposed. The second photoresist located between adjacent light-emitting chips, as well as all of the first photoresist, are removed using a developer.

4. The mass transfer method as described in claim 1, characterized in that, The thickness of the first photoresist is less than the thickness of the second photoresist.

5. The mass transfer method as described in claim 1, characterized in that, The method further includes: After the light-emitting chip is bonded to the driving backplane, the second photoresist is removed.

6. The mass transfer method as described in claim 5, characterized in that, The step of removing the second photoresist specifically includes: If the second photoresist is a positive photoresist, first expose all of the second photoresist, and then use a developer to wash away the second photoresist. If the second photoresist is a negative photoresist, then the second photoresist can be directly washed away using a developer.

7. The mass transfer method as described in claim 1, characterized in that, The light-emitting chip includes a vertical structure light-emitting chip or a flip-chip light-emitting chip.

8. The mass transfer method as described in claim 7, characterized in that, The light-emitting chip includes at least an N-type gallium nitride layer, a light-emitting layer, a P-type gallium nitride layer, an electrode, and a passivation layer. The N-type gallium nitride layer, the light-emitting layer, and the P-type gallium nitride layer are stacked sequentially. The electrode is electrically connected to the N-type gallium nitride layer and / or the P-type gallium nitride layer. The passivation layer covers the sidewalls of the N-type gallium nitride layer, the light-emitting layer, and the P-type gallium nitride layer and exposes the surface of the electrode.

9. A mass transfer device, characterized in that, include: A growth substrate on which multiple independent light-emitting chips are arranged in an array; The second photoresist covers the outer wall of each of the light-emitting chips and is spaced a first predetermined distance from the growth substrate. The second photoresist between adjacent light-emitting chips is spaced a second predetermined distance apart. When the light-emitting chips are peeled off from the growth substrate by laser and bonded to the driving backplane, the second photoresist located on the outer wall of the light-emitting chip contains the generated debris.

10. The mass transfer device as described in claim 9, characterized in that, The second photoresist is either a negative photoresist or a positive photoresist.

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