Mass transfer method

Abstract

The invention relates to the technical field of chip processing, in particular to a mass transfer method, which comprises the following steps that: firstly, chips are sequentially transferred into a driving back plate, chip electrodes are in one-to-one correspondence with bonding pads in the driving back plate, and meanwhile, the distance from the upper surface of the later transferred chip to the driving back plate is greater than the distance from the upper surface of the transferred chip to the driving back plate; in other words, a certain height difference exists between the post-transfer chip and the transferred chip, so that the subsequent chip alignment transfer is facilitated, the transfer difficulty is reduced, and high-density arrangement of pixels is facilitated.

Description

Technical Field

[0001] The present invention relates to the field of semiconductor processing technology, and in particular to a mass transfer method. Background Art

[0002] A pixel, short for "picture element," is the smallest unit of a digital image. On display devices like computer screens, digital cameras, and mobile phone screens, images are composed of tiny dots. Each pixel contains information such as color and brightness. When numerous pixels are arranged in a specific pattern, they form a complete image.

[0003] Pixel density is crucial for improving display clarity, fidelity, and detail. High-pixel-density screens provide sharper, more realistic images. Increasing pixel density allows displays to better adapt to high-resolution content, fully leveraging its image quality and avoiding image stretching or distortion caused by insufficient pixels.

[0004] In display devices, under the premise of ensuring display effects such as display brightness, in order to increase pixel arrangement density, microchips can be used to form pixels while reducing the pixel pitch. The size of the microchip can be below 100μm, such as Micro LED, with a pixel pitch below 200μm.

[0005] During display device manufacturing, mass transfer technology is often used to transfer chips from wafer substrates to driver backplanes. This technology requires extremely high efficiency, yield, and transfer accuracy. However, the extremely small pixel pitch in high-pixel-density display devices greatly increases the difficulty of transfer. Summary of the Invention

[0006] In view of the above-mentioned deficiencies in the prior art, the present application provides a mass transfer method, which can reduce the difficulty of high-density pixel transfer of display devices.

[0007] The technical solutions adopted in this application are as follows: A mass transfer method, applied to a display device, is characterized in that the method comprises: Provide a plurality of chips, the chips comprising at least: a first light color chip, a second light color chip to an Nth light color chip, where N is an integer greater than or equal to 2; A driving backplane is provided, wherein a plurality of pads are provided in the driving backplane, and the pads include at least: a first pad, a second pad to an Nth pad; The first light color chip, the second light color chip to the Nth light color chip are transferred to the driving backplane in sequence, and are flip-chip connected to the first pad and the second pad to the Nth pad in a one-to-one correspondence. The distance from the upper surface of the second light color chip to the driving backplane is greater than the distance from the upper surface of the first light color chip to the driving backplane, the distance from the upper surface of the third light color chip to the driving backplane is greater than the distance from the upper surface of the second light color chip to the driving backplane, and the distance from the upper surface of the Nth light color chip to the driving backplane is greater than the distance from the upper surface of the N-1th light color chip to the driving backplane.

[0008] It is further characterized in that Before the transfer, the first light color chip array is distributed on the first substrate, the second light color chip array is distributed on the second substrate, and the Nth light color chip array is distributed on the Nth substrate.

[0009] Preferably, among the first light color chip, the second light color chip to the Nth light color chip, at least the first light color chip and the second light color chip have different light colors.

[0010] Preferably, the first light color chip includes: a first transfer luminescent body and a first backup luminescent body, at least one column and / or row of first luminescent bodies adjacent to the first transfer luminescent body is the first backup luminescent body, and a first electrode is prepared in the first transfer luminescent body; Similarly, the second light color chip includes: a second transfer light-emitting body, a second backup light-emitting body, at least one column and / or a row of second light-emitting bodies adjacent to the second transfer light-emitting body is the second backup light-emitting body, and a second electrode is prepared in the second transfer light-emitting body~the Nth light color chip includes: an Nth transfer light-emitting body, an Nth backup light-emitting body, at least one column and / or a row of Nth light-emitting bodies adjacent to the Nth transfer light-emitting body is the Nth backup light-emitting body, and an Nth electrode is prepared in the Nth transfer light-emitting body.

[0011] Preferably, the electrodes of the same light color chip have the same height.

[0012] Preferably, the height of the first electrode, the height of the second electrode to the height of the Nth electrode increase in sequence, and the height difference between the second electrode and the first electrode is set to M1, the height difference between the third electrode and the second electrode is set to M2, and the height difference between the Nth electrode and the N-1th electrode is set to M. N-1 , then the height difference M1 is greater than the thickness of the first luminous body, and the height difference M2 is greater than the thickness of the second luminous body. N-1 The height difference between the second pad and the first pad is set to M1, the height difference between the third pad and the second pad is set to M2, and the height difference between the Nth pad and the N-1th pad is set to M. N-1, the height difference M1 is greater than the thickness of the first light-emitting body, the height difference M2 is greater than the thickness of the second light-emitting body ~ the height difference M N-1 is greater than the thickness of the (N - 1)th light-emitting body.

[0013] Preferably, an inverted alignment bonding process is adopted to sequentially transfer the first light-color chip, the second light-color chip ~ the Nth light-color chip to the driving backplane, including: The first electrode is pre-bonded in alignment with the first pad, and the first substrate is peeled off; The second electrode is pre-bonded in alignment with the second pad, and the second substrate is peeled off; And so on. The Nth electrode is pre-bonded in alignment with the Nth pad, and the Nth substrate is peeled off.

[0014] Preferably, after the transfer of the Nth light-color chip is completed, bonding is performed again so that the upper surface of the Nth light-color chip ~ the upper surface of the second light-color chip is flush with the upper surface of the first light-color chip.

[0015] Preferably, an inverted alignment bonding process is adopted to sequentially transfer the first light-color chip, the second light-color chip ~ the Nth light-color chip to the driving backplane so that the upper surface of the second light-color chip ~ the upper surface of the Nth light-color chip is flush with the upper surface of the first light-color chip, including: The first electrode is pre-bonded in alignment with the corresponding first pad, and the first substrate is peeled off; The second electrode is pre-bonded in alignment with the corresponding second pad, the second substrate is peeled off, and bonding is performed again so that the upper surface of the second light-color chip is flush with the upper surface of the first light-color chip; And so on. The Nth electrode is pre-bonded in alignment with the corresponding Nth pad, the Nth substrate is peeled off, and bonding is performed again so that the upper surface of the Nth light-color chip is flush with the upper surface of the first light-color chip.

[0016] Preferably, when N = 3, the pads include a first pad, a second pad, and a third pad. The first pad, the second pad, and the third pad are arranged at intervals in sequence along the horizontal and / or vertical directions in the driving backplane, or the first pad, the second pad, and the third pad are arranged in a "pin" shape in the driving backplane.

[0017] Preferably, when N=4, the pads include a first pad, a second pad, a third pad, and a fourth pad, and the first pad, the second pad, the third pad, and the fourth pad are distributed in a rectangular shape in the driving backplane, and the chip includes a first light color chip, two second light color chips, and a third light color chip. After transfer, the first light color chip and the third light color chip are diagonally distributed, and the two second light color chips are diagonally distributed.

[0018] Preferably, the light colors of the first light color chip, the second light color chip, and the third light color chip are red, green, and blue, respectively.

[0019] Preferably, the first electrode, the second electrode to the Nth electrode are all protrusions, and the middle parts of the first pad, the second pad to the Nth pad are all grooves, or the middle parts of the first electrode, the second electrode to the Nth electrode are grooves, and the first pad, the second pad to the Nth pad are protrusions, and the shape of the protrusions matches that of the grooves. During pre-bonding and re-bonding, the protrusions engage with the grooves accordingly.

[0020] Preferably, the protrusion is nail-shaped, and the cross-sectional shape of the protrusion is circular, square, triangular or cross-shaped.

[0021] The above-mentioned scheme of the present invention can achieve the following beneficial effects: in the mass transfer process of the present application, the distance from the upper surface of the post-transfer chip to the driving backplane is greater than the distance from the upper surface of the transferred chip to the driving backplane: the distance from the upper surface of the second light color chip to the driving backplane is greater than the distance from the upper surface of the first light color chip to the driving backplane, the distance from the upper surface of the third light color chip to the driving backplane is greater than the distance from the upper surface of the second light color chip to the driving backplane~the distance from the upper surface of the Nth light color chip to the driving backplane is greater than the distance from the upper surface of the N-1th light color chip to the driving backplane, that is, there is a certain height difference between the post-transfer chip and the transferred chip, thereby reducing the difficulty of high-density pixel transfer of the display device. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 This is a schematic structural diagram of the first wafer of this application; Figure 2 This is a schematic diagram of the top view of the first wafer of this application Figure 3 This is a schematic structural diagram of the second wafer of this application; Figure 4 This is a schematic diagram of the top view of the second wafer of the present application; Figure 5 This is a schematic structural diagram of the third wafer of this application; Figure 6 This is a schematic diagram of the top view of the third wafer of this application; Figure 7This is a schematic diagram of the structure of the first wafer and the driving backplane correspondingly bonded to each other in this application; Figure 8 This is a schematic diagram of the structure of peeling off the first substrate in this application; Figure 9 This is a schematic structural diagram of the corresponding bonding between the second wafer and the driving backplane in the first embodiment of the present application; Figure 10 This is a schematic diagram of the structure of peeling off the second substrate in Example 1 of the present application; Figure 11 This is a schematic structural diagram of the corresponding bonding between the third wafer and the driver backplane in the first embodiment of the present application; Figure 12 This is a schematic diagram of the structure of peeling off the third substrate in Example 1 of the present application; Figure 13 This is a schematic diagram of the structure in which the upper surface of the third light color chip is flush with the upper surface of the second light color chip and the upper surface of the first light color chip in Example 1 of the present application; Figure 14 This is a schematic structural diagram of the second electrode and the corresponding second pad after pre-bonding in the second embodiment of the present application; Figure 15 This is a schematic diagram of the structure after the second substrate is peeled off in Example 2 of the present application; Figure 16 Schematic diagram of the structure after pre-bonding of the third electrode and the corresponding third pad in the second embodiment of the present application; Figure 17 This is a schematic diagram of the structure after the third substrate is peeled off in Example 2 of the present application; Figure 18 This is a structural diagram of the second embodiment of the present application in which the upper surface of the third light color chip is flush with the upper surface of the second light color chip and the upper surface of the first light color chip; Figure 19 This is a schematic diagram of the structure in which the upper surface of the second light color chip is flush with the upper surface of the first light color chip in Example 3 of the present application; Figure 20 This is a structural diagram of the third light color chip in Example 3 of the present application, in which the upper surface of the third light color chip is flush with the upper surface of the second light color chip and the upper surface of the first light color chip; Figure 21 This is a schematic diagram of the structure in which the upper surface of the second light color chip is flush with the upper surface of the first light color chip in the fourth embodiment of the present application; Figure 22 This is a structural diagram of the fourth embodiment of the present application in which the upper surface of the third light color chip is flush with the upper surface of the second light color chip and the upper surface of the first light color chip.

[0023] Reference numerals: first photochromic chip 101 , first substrate 102 , first electrode 103 ; The first transfer light-emitting body 101a and the first backup light-emitting body 101b; A second photochromic chip 201, a second substrate 202, and a second electrode 203; A third light color chip 301, a third substrate 302, and a third electrode 303; Driving backplane 4, first pad 401, second pad 402, third pad 403, fourth pad 404. DETAILED DESCRIPTION

[0024] In order to enable those skilled in the art to better understand the solutions of the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts should fall within the scope of protection of the present invention.

[0025] It should be noted that the terms "including" and "having" and any variations thereof in the specification and claims of the present invention and the above-mentioned drawings are intended to cover non-exclusive inclusions. For example, a process, method, apparatus, product or equipment that includes a series of steps or units is not necessarily limited to those steps or units clearly listed, but may include other steps or units that are not clearly listed or are inherent to these processes, methods, products or equipment.

[0026] In display devices, higher pixel density means that the number of pixels per inch on the screen increases, which improves resolution and realism, and allows image details to be presented more accurately.

[0027] During the display device manufacturing process, chip transfer is primarily achieved through mass transfer technology. Mass transfer technology refers to the technology for transferring chips (such as Micro LEDs) grown on an epitaxial substrate (such as a wafer substrate) to a target substrate (such as a driver backplane) at high speed and precision. It includes two key processes: epitaxial substrate separation and chip placement. Epitaxial substrate separation mainly includes two types of technology: laser lift-off technology and chemical lift-off technology. Laser lift-off refers to the use of laser to irradiate the side of the epitaxial substrate away from the chip, thereby separating the epitaxial substrate from the chip, thereby arranging the chip array on the target substrate. Chemical lift-off technology refers to the use of chemical etching to remove the epitaxial substrate.

[0028] Mass transfer technology requires extremely high efficiency, yield, and transfer accuracy. However, the extremely small pixel pitch in high-pixel-density display devices greatly increases the difficulty of transfer.

[0029] In response to the technical problem of difficulty in transferring high-density pixels in display devices in the prior art, several specific embodiments of mass transfer methods are provided below to achieve precise transfer of high-density pixels. Example 1

[0030] The specific steps of mass transfer include: S1, providing a number of chips. In this embodiment, N=3, and the chips include: a first light color chip 101, a second light color chip 201, and a third light color chip 301. The first light color chip 101, the second light color chip 201, and the third light color chip 301 are all Micro LED chips. The first light color chip 101 is arrayed on the first substrate 102 of the first wafer, the second light color chip 201 is arrayed on the second substrate 202 of the second wafer, and the third light color chip 301 is arrayed on the third substrate 302 of the third wafer. Figures 1 to 6 Micro LED is a micron-scale light-emitting unit, typically less than 100μm in size. Compared to LCD and OLED, it has advantages in display performance, such as small size, high brightness, low energy consumption, and long service life. When assembled onto a driver backplane, it can form a high-density pixel Micro LED display device. In this application, the first, second, and third substrates are all epitaxial substrates, and the driver backplane is the target substrate.

[0031] The first wafer, the second wafer, and the third wafer are prepared in advance and ready for use. Taking the preparation of the first light color chip 101 in the first wafer as an example, specifically, S11, a first substrate 102 is provided. The first substrate 102 is a light-transmitting substrate, and the material is preferably sapphire. A metal organic compound chemical vapor deposition method is used to deposit a first-type GaN material, a light-emitting material, and a second-type GaN material in sequence on the front side of the first substrate 102 to form an epitaxial layer.

[0032] S12. Use a photolithography and etching process to etch the epitaxial layer to form a plurality of first light-emitting bodies distributed in an array. The first light-emitting bodies include an N-type GaN layer, a light-emitting layer, and a P-type GaN layer distributed in sequence from bottom to top.

[0033] S13. Use photolithography, deposition and stripping processes to sequentially prepare a current spreading layer and a reflective layer on the surface of the P-type GaN layer of the first light-emitting body. The current spreading layer is an ITO current spreading layer, which is used to quickly expand the current of the P electrode and evenly transmit it to the P-type GaN layer. The reflective layer is a metal reflective layer or a DBR reflective layer, which is used to reflect the light emitted by the light-emitting layer to improve the light extraction efficiency of the first light-emitting body.

[0034] S14. Using chemical vapor deposition or atomic layer deposition, an insulating material is deposited on the entire surface including the surface of the reflective layer to form an insulating layer.

[0035] S15. Divide the first light-emitting body into a first transfer light-emitting body 101a and a first backup light-emitting body 101b. At least one column and / or row of first light-emitting bodies adjacent to the first transfer light-emitting body 101a are first backup light-emitting bodies 101b. The first transfer light-emitting body 101a is used for the current transfer, and the first backup light-emitting body 101b is reserved for subsequent process transfer.

[0036] During transfer, the first transferred light-emitting element 101a corresponds to the first soldering pad 401 on the driver backplane 4. In this embodiment, the first light-emitting elements in the two columns and two rows adjacent to the first transferred light-emitting element 101a are the first backup light-emitting elements 101b. In subsequent processes, the first P electrode and the first N electrode are only prepared on the first transferred light-emitting element 101a, and the first electrode is not prepared on the first backup light-emitting element 101b. This allows for a safe clearance during subsequent alignment and pre-bonding. This prevents the first electrode of the first backup light-emitting element 101b from connecting to the soldering pad adjacent to the first soldering pad 401 during pre-bonding, thereby preventing the subsequent transfer of the second light color chip 201 and the third light color chip 301 from occurring.

[0037] S16. Use a photolithography process to etch the insulating layer corresponding to the first transfer light-emitting body 101a, and etch a first etching hole and a second etching hole above the first transfer light-emitting body 101a.

[0038] S17. Using photolithography and electroplating processes, form a first electrode 103 within and above the first etched hole and the second etched hole. The first electrode 103 includes a first P electrode and a first N electrode. The bottom end of the first P electrode extends through the first etched hole and contacts the reflective layer in the first transfer light-emitting body. The electrode is electrically connected to the P-type GaN layer in the first transfer light-emitting body through the reflective layer and the current spreading layer. The bottom end of the first N electrode extends through the second etched hole and contacts the N-type GaN layer to achieve electrical connection, thereby obtaining the first light color chip 101. In this embodiment, the first P electrode and the first N electrode are shaped as nail-shaped protrusions. The cross-section of the protrusions includes, but is not limited to, circular, square, triangular, or cross-shaped. In this embodiment, the cross-shaped shape is preferred.

[0039] Similarly, through the above steps S11 to S17, the second photochromic chip 201 and the third photochromic chip 301 are respectively prepared. In the first photochromic chip 101, the second photochromic chip 201, and the third photochromic chip 301 prepared in the above manner, the first electrode height, the second electrode height, and the third electrode height increase in sequence. The first electrode height, the second electrode height, and the third electrode height refer to the vertical distances from the upper surface of the first electrode, the upper surface of the second electrode, and the upper surface of the third electrode to the upper surface of the corresponding insulating layer, respectively, and are set to h1, h2, and h3, respectively, such that h3>h2>h1.

[0040] In addition, the chips in the same wafer have the same light color: the first light color chips in the first wafer are all red light chips, the second light color chips in the second wafer are all green light chips, and the third light color chips in the third wafer are all blue light chips. When displaying, the red, green, and blue light colors are mixed to form the required display color.

[0041] S2. Provide a driving backplane, which is provided with a plurality of pads, N=3, and the pads include: a first pad 401 matching the size of the first electrode 103, a second pad 402 matching the size of the second electrode 203, and a third pad 403 matching the size of the third electrode 303; in this embodiment, the heights of the first pad 401, the second pad 402, and the third pad 403 are consistent, that is, the surfaces of the first pad 401, the second pad 402, and the third pad 403 are flush, which is conducive to reliable bonding of the first pad 401, the second pad 402, and the third pad 403 to the corresponding electrodes.

[0042] Using photolithography and electroplating processes, a first pad 401, a second pad 402, and a third pad 403 are formed on the surface of the driver backplane. In this embodiment, the first electrode 103, the second electrode 203, and the third electrode 303 are all nail-shaped protrusions. The middle portions of the first pad 401, the second pad 402, and the third pad 403 are grooves. The shape of the grooves matches the shape of the nail-shaped protrusions, facilitating the alignment of the electrodes and pads in the subsequent pre-bonding process. At the same time, the corresponding engagement of the protrusions and the grooves forms a mortise and tenon structure, which helps to improve the reliability of the pre-bonding and re-bonding of the electrodes and pads.

[0043] S3. Transfer the first light color chip 101, the second light color chip 201, and the third light color chip 301 to the driving backplane 4 in sequence, and the first electrode 103, the second electrode 203, and the third electrode 303 correspond one to one with the first pad 401, the second pad 402, and the third pad 403 in the driving backplane 4.

[0044] 10. The first electrode 103 is bonded to the first soldering pad 401 by the first soldering pad 401. The first soldering pad 401 is bonded to the first soldering pad 401 by the first soldering pad 401. The first soldering pad 401 is bonded to the first soldering pad 401 by the first soldering pad 401. Figure 7 .

[0045] S32, peeling off the first substrate 103. In this embodiment, the first light color chip 101 is a red light chip. After the pre-bonding is completed, a laser peeling process is used to peel off the first substrate. Specifically, the laser irradiates the side of the first substrate 102 away from the first light color chip 101 to reduce the adhesion between the first substrate 102 and the first light color chip 101, so that the first light color chip 101 is arranged in the driving backplane 4. Figure 8 .

[0046] S33, the second electrode 203 is pre-bonded to the second pad 402. Specifically, the second wafer is moved so that the surface where the active area of ​​the second transfer light-emitting body is located (i.e., the surface where the second P electrode and the second N electrode are located) corresponds to the surface where the second pad 402 in the driving backplane 4 is located. The distance from the upper surface of the second light-color chip (i.e., the light-emitting surface of the second light-color chip) to the driving backplane 4 is greater than the distance from the upper surface of the first light-color chip (i.e., the light-emitting surface of the first light-color chip) to the driving backplane 4, so as to form an avoidance. The distance from the upper surface of the first light-color chip to the driving backplane 4 is set to H1, and the distance from the upper surface of the second light-color chip (i.e., the light-emitting surface of the second light-color chip) to the driving backplane 4 is set to H2, then H2>H1, that is, a first height difference M1 is formed, and the first height difference is greater than the first light-emitting body thickness H of the first light-color chip 101, thereby facilitating the transfer of the second light-color chip 201.

[0047] The second electrode 203 is aligned and pre-bonded with the second pad 402. During the pre-bonding process, heating and pressurization are performed. The heating temperature is 25°C to 150°C. The appropriate heating temperature is selected according to the electrode and pad materials. In the first embodiment, the second electrode and the second pad are both made of copper. Therefore, the heating temperature is preferably 120°C. The applied pressure is 10Mpa to 100Mpa, preferably 75Mpa. The extrusion time is 1min to 10min, preferably 5min, so as to achieve the corresponding pre-bonding of the second electrode 203 and the second pad 402. After the pre-bonding is completed, the distance H2 from the upper surface of the second light color chip (i.e., the light emitting surface of the second light color chip) to the driving backplane 4 is still greater than the distance H1 from the upper surface of the first light color chip (i.e., the light emitting surface of the first light color chip) to the driving backplane 4. Figure 9 .

[0048] S34, peeling off the second substrate 202. In this embodiment, the second light color chip 201 is a green light chip. The laser peeling process is used to peel off the second substrate 202. Specifically, the laser irradiates the second substrate 202 to separate the second substrate 202 from the second light color chip 201, so that the second light color chip 201 is arranged in the driving backplane 4. Figure 10 .

[0049] S35. Pre-bond the third electrode 303 and the third pad 403. Specifically, move the third wafer so that the surface where the active area of ​​the third light color chip 301 in the third wafer is located (i.e., the surface where the third P electrode and the third N electrode are located) corresponds to the surface where the third pad 403 in the driving backplane 4 is located. During the transfer process, the distance H3 from the upper surface of the third light color chip (i.e., the light emitting surface of the third light color chip) to the driving backplane 4 is greater than the distance H2 from the upper surface of the second light color chip (i.e., the light emitting surface of the second light color chip) to the driving backplane 4, i.e., H3>H2, forming a height difference M2, which is greater than the thickness H of the second light-emitting body of the second light color chip 201, thereby facilitating the transfer of the third light color chip 301.

[0050] The third electrode 303 and the third pad 403 are aligned and pre-bonded. During the pre-bonding process, heating and pressurization are performed. The heating temperature is 25°C to 150°C. The appropriate heating temperature is selected according to the electrode and pad materials. In the first embodiment, the third electrode and the third pad are both made of copper. Therefore, the heating temperature is preferably 120°C, the applied pressure is 10Mpa to 100Mpa, preferably 75Mpa, and the extrusion time is 1min to 10min, preferably 5min, so as to achieve pre-bonding of the third electrode 303 and the third pad 403. After the pre-bonding is completed, the distance from the upper surface of the third light color chip to the driving backplane 4 is still greater than the distance from the upper surface of the second light color chip to the driving backplane 4. Figure 11 .

[0051] S36, peeling off the third substrate 302. In this embodiment, the third light color chip 301 is a blue light chip. The laser peeling process is used to peel off the third substrate 302. Specifically, the laser irradiates the third substrate 302 to separate the third substrate 302 from the third light color chip 301, so that the third light color chip 301 is arranged in the driving backplane 4. Figure 12 .

[0052] S4. Use a bonding process to perform re-bonding so that the upper surfaces of the third light color chip, the second light color chip, and the first light color chip remain flush.

[0053] In the first embodiment of the present invention, after the first substrate 102, the second substrate 202, and the third substrate 302 are peeled off, the distances from the light-emitting surfaces of the first light-color chip, the second light-color chip, and the third light-color chip to the driving backplane 4 continue to increase successively, that is, the first light-color chip 101, the second light-color chip 201, and the third light-color chip 301 are arranged in a stepped manner. In this application, a single chip is used as a pixel, and the minimum distance between two adjacent pixels can reach 10um. In order to keep the third light color chip, the second light color chip and the upper surface of the first light color chip flush, this embodiment adopts a bonding process for re-bonding. During re-bonding, heating and pressurization are performed. The heating temperature is 25°C~150°C, preferably 120°C, the applied pressure is 50Mpa~150Mpa, preferably 100Mpa, and the extrusion duration is 5min~15min, preferably 10min. Pressure is applied to the second light color chip 201 and the third light color chip 301 to make the distance from the upper surface of the second light color chip and the upper surface of the third light color chip to the driving backplane 4 equal to the distance from the upper surface of the first light color chip to the driving backplane 4, thereby achieving the flush setting of the upper surface of the third light color chip, the upper surface of the second light color chip and the upper surface of the first light color chip. Figure 13 This is beneficial for subsequent packaging operations. Currently, when packaging is performed using a lamination or laminating process, the chip surface is generally required to have a high degree of flatness. The upper surfaces of the third-color chip and the second-color chip are kept flush with the upper surface of the first-color chip. This effectively avoids problems such as poor brightness uniformity on the display screen caused by uneven light-emitting surfaces of the first, second, and third-color chips, and is beneficial for improving the display effect of the display device.

[0054] In the above steps, since both the second electrode 203 and the third electrode 303 are nail-shaped protrusions, during the pre-bonding process with the second pad 402 and the third pad 403 respectively, the end portions of the protrusion parts of the nail-shaped protrusions are installed in the corresponding grooves under the action of pressure, and a primary deformation occurs at the same time. Since the pressure applied during the pre-bonding process is small, the deformation generated is also small. When bonding again later, the pressure applied is greater than the pre-bonding pressure, so that the end portions of the protrusion parts of the nail-shaped protrusions generate a larger deformation and fill the corresponding grooves, realizing full contact between the electrodes and the pads, further improving the bonding reliability, and avoiding the problem of virtual connection affecting the electrical performance of the display device. In this application, the materials used to form the electrodes and pads are conductive metal materials, and the conductive metal materials need to have a relatively high melting point, generally at 1000 °C, such as copper. During the bonding process, it is easy to generate deformation, and at the same time, copper diffuses with copper to achieve firm bonding.

[0055] In this embodiment, after the transfer is completed, the first optical color chip 101, the second optical color chip 201, and the third optical color chip 301 are arranged at intervals in sequence along the horizontal direction in the driving backplane 4.

[0056] It should be noted that in another embodiment, if the first pad 401, the second pad 402, and the third pad 403 are distributed at intervals in sequence along the horizontal and vertical directions respectively, then the first optical color chip 101, the second optical color chip 201, and the third optical color chip 301 are distributed at intervals in sequence along the horizontal and vertical directions respectively in the driving backplane; if the first pad 401, the second pad 402, and the third pad 403 are arranged in a "pin" shape, then the first optical color chip 101, the second optical color chip 102, and the third optical color chip 103 are arranged in a "pin" shape in the driving backplane 4.

[0057] It should be further noted that in another embodiment, when N = 4, the pads include a first pad 401, a second pad 402, a third pad 403, and a fourth pad. The first pad 401, the second pad 402, the third pad 403, and the fourth pad are distributed in a rectangle in the driving backplane 4. The chips include one first optical color chip 101, two second optical color chips 201, and one third optical color chip 301. After the transfer, the first optical color chip 101 and the third optical color chip 301 are distributed diagonally, and the two second optical color chips 301 are distributed diagonally.

[0058] In the first embodiment, the first light-color chip 101, the second light-color chip 102, and the third light-color chip 103 are directly transferred from the wafer substrate to the driving backplane. In another embodiment, when the first light-color chip 101, the second light-color chip 102, and the third light-color chip 103 are arranged in a "pin" shape, or when the first light-color chip 101, the second light-color chip 102, and the third light-color chip 103 are arranged in a rectangle, a temporary substrate can be set up. First, the chips to be transferred are transferred from the wafer substrate to the temporary substrate, and then the chips in the temporary substrate are transferred to the driving backplane. Embodiment 2

[0059] The mass transfer method in this second embodiment includes the above steps S1 to S4. The difference is that in step S17, the shapes of the second electrode 203 and the third electrode 303 formed are different from those in the first embodiment, and in step S2, the shapes of the second pad 402 and the third pad 403 formed are different from those in the first embodiment. In this second embodiment, the middle parts of the second electrode 203 and the third electrode 303 are grooves, and the second pad 402 and the third pad 403 are nail-shaped protrusions. The cross-sectional shape of the protrusion is circular, square, triangular or cross-shaped, preferably cross-shaped. During pre-bonding and re-bonding, the protrusion and the groove are correspondingly engaged to achieve a stable connection between the electrode and the pad.

[0060] The structure of the first electrode and the first pad is the same as that in the first embodiment above, and the structure of the second pad 402 is as Figure 14 、 Figure 15 shown. Figure 14 is a schematic structural diagram after pre-bonding the second electrode 203 and the corresponding second pad 402 in this second embodiment. After pre-bonding, the distance H2 from the upper surface of the second light-color chip 201 to the driving backplane is greater than the distance H1 from the upper surface of the first light-color chip to the driving backplane. Figure 15 is a schematic structural diagram after peeling off the second substrate 202 in this second embodiment.

[0061] The structure of the third pad 403 is as Figure 16 And Figure 17 shown, Figure 16 is a schematic structural diagram after pre-bonding the third electrode 303 and the corresponding third pad 403 in this second embodiment. After pre-bonding, the distance H3 from the upper surface of the third light-color chip to the driving backplane is greater than the distance H2 from the upper surface of the second light-color chip 201 to the driving backplane, Figure 17 is a schematic structural diagram after peeling off the third substrate 302 in this third embodiment.

[0062] After peeling off the third substrate, the second and third pads 402 and 403 are bonded again. Under the action of heat and pressure, the ends of the protrusions are deformed and filled in the grooves of the corresponding second and third electrodes 203 and 303, thereby achieving reliable bonding. At the same time, the upper surface of the third light color chip is flush with the upper surface of the second and first light color chips. Figure 18 .

[0063] In the second embodiment, the heights of the first electrode, the second electrode and the third electrode are consistent, and the heights of the first pad, the second pad and the third pad increase successively, so that the distance from the upper surface of the second photochromic chip to the driving backplane 4 is greater than the distance from the upper surface of the first photochromic chip to the driving backplane 4, and the distance from the upper surface of the third photochromic chip to the driving backplane 4 is greater than the distance from the upper surface of the second photochromic chip to the driving backplane 4, thereby facilitating the sequential transfer of the second photochromic chip 201 and the third photochromic chip 301 and reducing the difficulty of high-density pixel arrangement. Example 3

[0064] The mass transfer method in the third embodiment includes steps S1 to S3 of the first embodiment, with the difference being that in step S34 of the third embodiment, after peeling off the second substrate 202, it is re-bonded, heated, and pressurized. The heating temperature is 25°C to 150°C, preferably 120°C, the applied pressure is 50Mpa to 150Mpa, preferably 100Mpa, and the extrusion duration is 5min to 15min, preferably 10min, so that the distance from the upper surface of the second photochromic chip to the driving backplane 4 is equal to the distance from the upper surface of the first photochromic chip to the driving backplane 4, that is, the light-emitting surface of the second photochromic chip is flush with the light-emitting surface of the first photochromic chip. During the re-bonding process, the end of the second electrode is deformed and filled in the groove of the second pad 402 to achieve stable bonding. Figure 19 .

[0065] Similarly, in step S36 of the third embodiment, after peeling off the third substrate, it is re-bonded, heated, and pressurized. The heating temperature is 25°C~150°C, preferably 120°C, the applied pressure is 50Mpa~150Mpa, preferably 100Mpa, and the extrusion duration is 5min~15min, preferably 10min, so that the distance from the upper surface of the third light color chip to the driving backplane 4 is equal to the distance from the upper surface of the first light color chip to the driving backplane 4, that is, the light emitting surface of the third light color chip is flush with the light emitting surface of the second light color chip and the light emitting surface of the first light color chip. During the re-bonding process, the end of the third electrode is deformed and filled in the groove of the third pad 403 to achieve stable bonding. Figure 20 .

[0066] In the third embodiment, the light-emitting surfaces of the third light-color chip, the second light-color chip, and the first light-color chip are kept flush through the above-mentioned steps S34 and S36. Therefore, there is no need to perform step S4. However, compared with the first embodiment, the third embodiment requires two re-bondings, while the first embodiment only requires one re-bonding. Therefore, the processing technology of the first embodiment is simpler. Example 4

[0067] The mass transfer method in the fourth embodiment includes steps S1 to S3 of the second embodiment, with the difference being that in step S34 of the fourth embodiment, after peeling off the second substrate 202, it is bonded again, heated, and pressurized. The heating temperature is 25°C to 150°C, preferably 120°C, the applied pressure is 50Mpa to 150Mpa, preferably 100Mpa, and the extrusion duration is 5min to 15min, preferably 10min, so that the distance from the upper surface of the second light color chip to the driving backplane 4 is equal to the distance from the upper surface of the first light color chip to the driving backplane 4, that is, the light emitting surface of the second light color chip is flush with the light emitting surface of the first light color chip. During the re-bonding process, the end of the second pad is deformed and filled in the groove of the second electrode 203 to achieve stable bonding. Figure 21 .

[0068] Similarly, in step S36 of the fourth embodiment of the present invention, after peeling off the third substrate, it is re-bonded, heated, and pressurized. The heating temperature is 25°C~150°C, preferably 120°C, the applied pressure is 50Mpa~150Mpa, preferably 100Mpa, and the extrusion duration is 5min~15min, preferably 10min, so that the distance from the upper surface of the third light color chip to the driving backplane 4 is equal to the distance from the upper surface of the first light color chip to the driving backplane 4, that is, the light emitting surface of the third light color chip is flush with the light emitting surface of the second light color chip and the light emitting surface of the first light color chip. During the re-bonding process, the end of the third pad is deformed and filled in the groove of the third electrode 303 to achieve stable bonding. Figure 22 .

[0069] In the third embodiment, the light-emitting surfaces of the third light-color chip, the second light-color chip, and the first light-color chip are re-bonded through the above-mentioned steps S34 and S36, so that the light-emitting surfaces of the third light-color chip, the second light-color chip, and the first light-color chip remain flush. Therefore, there is no need to perform step S4. However, compared with the second embodiment, the fourth embodiment requires two re-bondings, while the second embodiment only requires one re-bonding. Therefore, the processing technology of the second embodiment is simpler.

[0070] The mass transfer method in this fifth embodiment includes steps S1 to S3 of the first embodiment or steps S1 to S3 of the second embodiment. The distance from the upper surface of the second photochromic chip to the driver backplane 4 is greater than the distance from the upper surface of the first photochromic chip to the driver backplane 4. The distance from the upper surface of the third photochromic chip to the driver backplane 4 is greater than the distance from the upper surface of the second photochromic chip to the driver backplane 4. This facilitates the sequential transfer of the second photochromic chip 201 and the third photochromic chip 301. After the transfer is completed, the minimum spacing between two adjacent pixels is 10 μm, achieving a high-density pixel arrangement. The difference in this fifth embodiment is that after the transfer of the first, second, and third photochromic chips is completed, there is no re-bonding. The light-emitting surfaces of the first, second, and third photochromic chips are uneven, affecting subsequent packaging. During display, uneven brightness is likely to occur, seriously affecting the display effect. The re-bonding of step S4 in the above-mentioned embodiment 1 and embodiment 2, and steps S34 and S36 in embodiment 3 and embodiment 4, can solve the above-mentioned problem, so that the light-emitting surfaces of the first light-color chip 101, the second light-color chip 201, and the third light-color chip 301 remain flush, which is beneficial for subsequent packaging and at the same time beneficial for improving the uniformity of display brightness.

[0071] The technical solutions of the above embodiments of the present application have the following advantages: (1) The chip in the display device of this application adopts a smaller Micro LED. Through mass transfer, a large number of chips can be integrated in a limited display area. The minimum spacing between two adjacent chips can be as small as 10μm. For example, in various display devices such as mobile phones and televisions, a higher pixel density can be achieved, thereby presenting clearer and more delicate images and texts, meeting consumers' demand for high-definition and ultra-high-definition displays.

[0072] (2) High-density pixel arrangement can significantly improve the brightness of the entire display device screen. At the same time, the mass transfer method of this application can accurately control the transfer position and spacing of the chip, thereby achieving a uniform luminous effect and providing users with a high-quality visual experience.

[0073] (3) By using the mass transfer method of the present application, the red, green and blue light color chips can be transferred to the driver backplane in a high-density arrangement to meet the color display requirements of the display device.

[0074] (4) The mass transfer method of this application is not only applicable to traditional rigid display screens, but can also meet the needs of emerging fields such as flexible display and wearable display. For example, in flexible display, Micro LED with high-density pixel arrangement can achieve high-resolution and high-brightness display effects on flexible substrates, providing technical support for the development of flexible display products.

[0075] (5) From a production perspective, the mass transfer method can complete the transfer of multiple chips in one transfer process, which greatly improves production efficiency and reduces production time and cost compared to the traditional chip-by-chip transfer method.

[0076] It is understood that the above specific description of the present invention is only used to illustrate the present invention and is not limited to the technical solutions described in the embodiments of the present invention. Those skilled in the art should understand that the present invention can still be modified or replaced with equivalents to achieve the same technical effects; as long as the use requirements are met, they are all within the scope of protection of the present invention.

Claims

1. A mass transfer method, applied to a display device, characterized in that: The method includes: A plurality of chips are provided, the chips comprising at least: a first light color chip (101), a second light color chip (201) to an Nth light color chip, where N is an integer greater than or equal to 2; A driving backplane (4) is provided, wherein a plurality of pads are provided in the driving backplane (4), and the pads at least include: a first pad (401), a second pad (402) to an Nth pad; The first light color chip (101), the second light color chip (201) to the Nth light color chip are sequentially transferred to the driving backplane (4), and are flip-chip connected to the first solder pad (401), the second solder pad (402) to the Nth solder pad in a one-to-one correspondence, the distance from the upper surface of the second light color chip to the driving backplane (4) is greater than the distance from the upper surface of the first light color chip to the driving backplane (4), the distance from the upper surface of the third light color chip to the driving backplane (4) is greater than the distance from the upper surface of the second light color chip to the driving backplane (4), and the distance from the upper surface of the Nth light color chip to the driving backplane (4) is greater than the distance from the upper surface of the N-1th light color chip to the driving backplane (4).

2. The mass transfer method according to claim 1, wherein: Before the transfer, the first light color chip (101) array is distributed on the first substrate (102), the second light color chip (201) array is distributed on the second substrate (202), and the Nth light color chip array is distributed on the Nth substrate.

3. The method for mass transfer according to claim 2, wherein: The first light color chip (101) comprises: a first transfer luminescent body (101a), a first backup luminescent body (101b), at least one column and / or one row of first luminescent bodies adjacent to the first transfer luminescent body (101a) being the first backup luminescent body (101b), and a first electrode being prepared in the first transfer luminescent body (101a); Similarly, the second light color chip (201) includes: a second transfer light-emitting body, a second backup light-emitting body, at least one column and / or one row of second light-emitting bodies adjacent to the second transfer light-emitting body is the second backup light-emitting body, and a second electrode is prepared in the second transfer light-emitting body~the Nth light color chip includes: an Nth transfer light-emitting body, an Nth backup light-emitting body, at least one column and / or one row of Nth light-emitting bodies adjacent to the Nth transfer light-emitting body is the Nth backup light-emitting body, and an Nth electrode is prepared in the Nth transfer light-emitting body.

4. The method for mass transfer according to claim 3, wherein: The height of the first electrode (103), the height of the second electrode (203) and the height of the Nth electrode increase in sequence, and the height difference between the second electrode and the first electrode is set to M1, the height difference between the third electrode and the second electrode is set to M2, and the height difference between the Nth electrode and the N-1th electrode is set to M N-1 , then the height difference M1 is greater than the thickness of the first luminous body, and the height difference M2 is greater than the thickness of the second luminous body. N-1 The height difference between the second pad and the first pad is set to M1, the height difference between the third pad and the second pad is set to M2, and the height difference between the Nth pad and the N-1th pad is set to M. N-1 , then the height difference M1 is greater than the thickness of the first luminous body, and the height difference M2 is greater than the thickness of the second luminous body. N-1 Greater than the thickness of the N-1th luminous body.

5. The method for mass transfer according to claim 4, wherein: The first light color chip (101), the second light color chip (201) to the Nth light color chip are sequentially transferred to the driving backplane (4) using a flip-chip bonding process, comprising: The first electrode (103) and the first pad (401) are aligned and pre-bonded, and the first substrate (102) is peeled off; The second electrode (203) and the second pad (402) are aligned and pre-bonded, and the second substrate (202) is peeled off; And so on. The Nth electrode is aligned and pre-bonded to the Nth pad, and the Nth substrate is peeled off.

6. The method for mass transfer according to claim 5, wherein: After the Nth light color chip is transferred, they are bonded again so that the upper surface of the Nth light color chip to the upper surface of the second light color chip are flush with the upper surface of the first light color chip.

7. The method for mass transfer according to claim 4, wherein: Adopt the flip-chip alignment bonding process to sequentially transfer the first optical color chip (101), the second optical color chip (201) to the Nth optical color chip to the driving backplane (4), including: The first electrode (103) is pre-bonded in alignment with the first pad (401), and the first substrate (102) is peeled off; The second electrode (203) is pre-bonded in alignment with the second pad (402). The distance from the upper surface of the second optical color chip to the driving backplane is greater than the distance from the upper surface of the first optical color chip to the driving backplane. The second substrate (202) is peeled off and bonded again to make the upper surface of the second optical color chip flush with the upper surface of the first optical color chip; And so on. The Nth electrode is pre-bonded in alignment with the Nth pad. The distance from the upper surface of the Nth optical color chip to the driving backplane is greater than the distance from the upper surface of the (N - 1)th optical color chip to the driving backplane. The Nth substrate is peeled off and bonded again to make the upper surface of the Nth optical color chip flush with the upper surface of the (N - 1)th optical color chip.

8. The method for mass transfer according to claim 6 or 7, wherein: The first electrode, the second electrode to the Nth electrode are all protrusions, and the middle parts of the first pad, the second pad to the Nth pad are all grooves, or the middle parts of the first electrode, the second electrode to the Nth electrode are grooves, and the first pad, the second pad to the Nth pad are protrusions. The shapes of the protrusions and the grooves match. When pre-bonding and bonding again, the protrusions and the grooves are correspondingly engaged.

9. The method for mass transfer according to claim 8, wherein: When N = 3, the chips include a first optical color chip (101), a second optical color chip (201), and a third optical color chip (301). The optical colors of the first optical color chip (101), the second optical color chip (201), and the third optical color chip (301) are red, green, and blue respectively. The pads include a first pad (401), a second pad (402), and a third pad (403). The first pad (401), the second pad (402), and the third pad (403) are arranged at intervals in sequence in the driving backplane (4) in the horizontal and / or vertical directions, or the first pad (401), the second pad (402), and the third pad (403) are arranged in a "pin" shape in the driving backplane (4).

10. The mass transfer method according to claim 8, wherein: When N = 4, the pads include a first pad (401), a second pad (402), a third pad (403), and a fourth pad (404). The first pad (401), the second pad (402), the third pad (403), and the fourth pad (404) are distributed in a rectangle in the driving backplane (4). The chips include one first optical color chip (101), two second optical color chips (201), and one third optical color chip (301). The optical colors of the first optical color chip (101), the second optical color chip (201), and the third optical color chip (301) are red, green, and blue respectively. After transfer, the first optical color chip (101) and the third optical color chip (301) are distributed diagonally, and the two second optical color chips (201) are distributed diagonally.

Images