Micro-LED display and preparation method thereof
By preparing a beveled shaped protruding structure on a sapphire substrate, and using nitrogen impact force during laser peeling to separate the component forces in the opposite horizontal directions, the crack problem caused by lattice mismatch in Micro-LED displays is solved, and the reliability and service life of the display are improved.
Patent Information
- Application Number
- CN202411478764.1
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-10-22
- Publication Date
- 2025-03-07
AI Technical Summary
During the preparation of Micro-LED display, the lattice mismatch between the sapphire substrate and the GaN epitaxial layer leads to dislocations and defects, affecting the photoelectric performance of the LED chip, and easily causing cracks in the functional layer of the LED chip during the peeling process.
A meter-shaped protruding structure with a slope is prepared on a sapphire substrate. When the laser peels off the LED chip, the laser refracts through the slope, decomposes gallium nitride and generates a nitrogen impact force. The nitrogen impact force is separated through the plane top part of the meter-shaped protruding structure to avoid cracks in the opposite horizontal direction being too close to each other.
It effectively avoids cracks in LED chips and improves the reliability and service life of the display.
Smart Images
Figure CN119584740A_ABST
Abstract
Description
Technical Field
[0001] The present application relates to the technical field of display panels, and in particular to a Micro-LED display and a method for preparing the same. Background Art
[0002] In the preparation process of MICRO-LED displays, the quality of LED chips directly determines the performance and life of the display. However, in the early stages of LED chip preparation, the lattice mismatch between the sapphire substrate and the GaN epitaxial layer has always been an insurmountable technical obstacle. This lattice mismatch easily leads to dislocations and defects, which in turn affects the growth quality of the epitaxial layer and ultimately reduces the optoelectronic performance of the LED chip.
[0003] In order to overcome this technical difficulty, the industry began to try to make periodic micro-nano patterns on sapphire substrates, namely the so-called PASS (Patterned Sapphire Substrate) structure. The introduction of this structure can effectively alleviate the dislocation and defect problems caused by lattice mismatch, significantly improve the growth quality of the epitaxial layer, and thus lay the foundation for the preparation of high-performance LED chips.
[0004] However, conventional PASS structures usually adopt a conical design. This design will cause conical pits to appear on the LED surface in subsequent processes, especially when peeling off the LED chip and sapphire substrate. The presence of these conical pits often becomes a stress concentration area, which in turn causes cracks in the functional layer of the LED chip. The generation of cracks will not only reduce the photoelectric conversion efficiency of the LED chip, but also seriously affect its reliability and service life. Summary of the invention
[0005] The purpose of this application is to provide a Micro-LED display and a method for preparing the same, which can improve the above-mentioned problems.
[0006] In a first aspect, the present application provides a method for preparing a Micro-LED display, comprising steps S1 to S4, wherein S1, S2, etc. are merely step identifiers, and the execution order of the method is not necessarily in ascending order of numbers, for example, step S2 may be executed first and then step S1, and the present application does not impose any limitation thereto.
[0007] S1, providing a sapphire substrate having a front surface and a back surface arranged oppositely, and etching a convex structure arranged in an array on the front surface; along a first direction perpendicular to the sapphire substrate and from the front surface to the back surface, the cross-section of the convex structure gradually increases, and the top of the convex structure is a plane parallel to the front surface;
[0008] S2, after growing a gallium nitride buffer layer on the front surface, sequentially growing epitaxial layers on the gallium nitride buffer layer, and preparing an LED chip;
[0009] S3, peeling the LED chip prepared on the sapphire substrate onto a temporary substrate by laser;
[0010] S4, transferring the LED chip on the temporary substrate to a display backplane for packaging through a mass transfer process.
[0011] It can be understood that the present application provides a method for preparing a Micro-LED display, in which a trapezoidal protrusion structure with an inclined surface is prepared on a sapphire substrate before growing a gallium nitride buffer layer and an LED epitaxial layer. When the LED chip and the sapphire substrate are peeled off by laser, the laser is refracted by the inclined surface, decomposes the gallium nitride along the refraction direction and generates a nitrogen impact force. Since the top of the trapezoidal protrusion structure is a plane, the nitrogen impact force in the refraction direction can be effectively separated to prevent the force components in the opposite horizontal direction from being too close and tearing the LED epitaxial layer. The method for preparing a Micro-LED display provided in the present application can prevent cracks in the LED chip and improve the reliability and service life of the display.
[0012] In an optional embodiment of the present application, the protrusion structure includes at least one of the following:
[0013] The protrusion structure is a truncated cone-shaped protrusion structure, which is a symmetrical structure about an axis perpendicular to the center of the circle. When peeling the LED chip and the growth substrate, the refracted light of the laser passing through the inclined surface also diverges about the above axis in the horizontal direction. Therefore, when peeling the LED chip, the nitrogen impact force generated by the laser can be balanced in the horizontal direction, and the LED chip can be peeled more stably.
[0014] The raised structure includes at least three side surfaces connected to the top, and the at least three side surfaces include a single inclined surface and at least two vertical surfaces. The inclined surface is inclined relative to the front surface, and the vertical surface is perpendicular to the front surface. The inclination direction and inclination angle of each of the inclined surfaces in the sapphire substrate are consistent.
[0015] In an optional embodiment of the present application, S3 includes at least one of the following:
[0016] Starting a laser light source to irradiate the sapphire substrate in a direction opposite to the first direction;
[0017] The laser generates a light beam toward a second horizontal direction through the inclined surface, and applies a pulling force in a direction opposite to the second horizontal direction to the temporary substrate.
[0018] In an optional embodiment of the present application, the distance between two adjacent truncated cone-shaped protrusion structures on the sapphire substrate is less than a preset distance value. It can be understood that the adjacent inclined surface areas of the two adjacent truncated cone-shaped protrusion structures are inclined in different directions. Therefore, when peeling the LED chip, the laser will generate nitrogen impact force components in opposite horizontal directions, thereby generating thrust on the LED epitaxial region between the two adjacent truncated cone-shaped protrusion structures. By reducing the distance between the two adjacent truncated cone-shaped protrusion structures, this thrust can be enhanced, and the LED chip can be peeled more effectively.
[0019] In an optional embodiment of the present application, S2 includes the following steps:
[0020] S21, growing a gallium nitride buffer layer on the front surface;
[0021] S22, sequentially growing an N-type semiconductor layer, a light-emitting layer, and a P-type semiconductor layer on the gallium nitride buffer layer to form an epitaxial layer, wherein the thickness of the N-type semiconductor layer is greater than a preset thickness value;
[0022] S23, cutting the epitaxial layer into light-emitting units arranged in an array, and manufacturing a first electrode and a second electrode on the light-emitting units to form each LED chip.
[0023] It can be understood that when the LED chip and the growth substrate are peeled off, the gallium nitride buffer layer at the interface will absorb a large amount of photon energy and undergo chemical decomposition to form metal gallium and nitrogen, thereby generating nitrogen impact force along the laser direction. If nitrogen impact force components in opposite horizontal directions are generated in adjacent areas, tearing force may be generated in the LED epitaxial region. Thickening the thickness of the N-type semiconductor layer is conducive to alleviating the tearing effect generated by the tearing force, thereby avoiding cracks in the LED chip.
[0024] In an optional embodiment of the present application, S4 includes the following steps:
[0025] S41, transferring the LED chip on the temporary substrate to a display backplane for welding through a mass transfer process;
[0026] S42, applying packaging glue on the display back panel and covering the LED chip;
[0027] S43, covering the packaging adhesive with a protective layer.
[0028] In an optional embodiment of the present application, the display back panel includes a flexible substrate, a circuit layer and a planarization layer stacked in sequence; electrode pad pairs are arrayed on the planarization layer, and the electrode pad pairs are connected to the circuit layer through conductive through holes, each electrode pad pair includes a first electrode pad and a second electrode pad, the first electrode pad is used to be welded to the first electrode, and the second electrode pad is used to be welded to the second electrode.
[0029] In an optional embodiment of the present application, the following steps are also included after S41 and before S42: on the flat layer, a piezoelectric unit is arranged between adjacent LED chips, and the piezoelectric unit is subjected to a squeezing force when it is bent during the curling, thereby generating positive charges on the front side of the piezoelectric unit and negative charges on the negative side of the piezoelectric unit.
[0030] In an optional embodiment of the present application, the circuit layer includes a driving circuit unit arranged in an array, and the driving circuit unit includes a first thin film transistor, a second thin film transistor, a capacitor and a voltage divider resistor; the source of the first thin film transistor is connected to the data signal line of the circuit layer, and the gate of the first thin film transistor is connected to the scanning signal line of the circuit layer; the source of the second thin film transistor is connected to the positive power supply of the circuit layer, the gate of the second thin film transistor is connected to the drain of the first thin film transistor, and the capacitor is also connected between the gate and the drain of the second thin film transistor; the drain of the second thin film transistor is connected in series with the corresponding LED chip and the voltage divider resistor and then grounded, the connection point between the LED chip and the voltage divider resistor is connected to the positive side of the piezoelectric unit, and the negative side of the piezoelectric unit is grounded.
[0031] It can be understood that for roll-up screen terminal devices, it is often necessary to change the display brightness according to the bending angle of the screen. For example, the display screen needs to gradually light up during the screen extension process, and the display screen needs to gradually stop displaying during the screen extension process. Conventional practices require adding an angle detection device to monitor the curling angle of the screen, and control the display brightness through a processor. The present application sets a piezoelectric unit in the flat layer of the display. The piezoelectric unit is subjected to an extrusion force when it bends during curling, thereby generating a positive charge on the front side of the piezoelectric unit and a negative charge on the negative side of the piezoelectric unit. The piezoelectric unit is connected in parallel with the voltage divider resistor of the LED chip, and a piezoelectric voltage is generated during the curling process to reduce the voltage difference across the LED chip, so that the display gradually stops displaying; during the screen extension process, the piezoelectric voltage decreases, thereby restoring the voltage difference across the LED chip, and the display gradually lights up again.
[0032] In a second aspect, the present application discloses a Micro-LED display prepared by the method described in any one of the first aspects.
[0033] Beneficial effects:
[0034] The present application provides a Micro-LED display and a method for preparing the same. Before growing a gallium nitride buffer layer and an LED epitaxial layer, a trapezoidal protrusion structure with an inclined surface is prepared on a sapphire substrate. When the LED chip and the sapphire substrate are peeled off by laser, the laser is refracted by the inclined surface, decomposing the gallium nitride along the refraction direction and generating a nitrogen impact force. Since the top of the trapezoidal protrusion structure is a plane, the nitrogen impact force in the refraction direction can be effectively separated to prevent the force components in the opposite horizontal direction from being too close and thus tearing the LED epitaxial layer. The method for preparing the Micro-LED display provided by the present application can prevent cracks in the LED chip and improve the reliability and service life of the display.
[0035] In order to make the above-mentioned objects, features and advantages of the present application more obvious and understandable, optional embodiments are specifically listed below and described in detail with reference to the attached drawings. BRIEF DESCRIPTION OF THE DRAWINGS
[0036] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings required for use in the embodiments will be briefly introduced below. It should be understood that the following drawings only show certain embodiments of the present application and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other related drawings can be obtained based on these drawings without paying creative work.
[0037] Figure 1 It is a schematic diagram of preparing an LED chip on a sapphire substrate in the prior art;
[0038] Figure 2 Laser peeling Figure 1 Light path analysis diagram of LED chips in the
[0039] Figure 3 yes Figure 2 The enlarged schematic diagram of the LED chip after peeling is shown;
[0040] Figure 4 This is a laser lift-off optical path analysis diagram of a PASS structure in the Micro-LED display manufacturing method provided in this application;
[0041] Figure 5 This is a laser lift-off optical path analysis diagram of another PASS structure in the Micro-LED display manufacturing method provided in this application;
[0042] Figure 6 It is another PASS structure provided by this application;
[0043] Figure 7 yes Figure 6 The laser lift-off optical path analysis diagram shown;
[0044] Figure 8 It is a schematic diagram of the structure after mass transfer in the method for preparing a Micro-LED display provided in the present application;
[0045] Fig. 9 It is a schematic diagram of the structure after packaging in the method for preparing a Micro-LED display provided in this application;
[0046] Fig.10 It is a schematic diagram of the structure of a display provided by the present application with a piezoelectric unit added;
[0047] Fig.11 yes Fig.10 The driving circuit of a single LED chip in the display shown. DETAILED DESCRIPTION
[0048] The following will be combined with the drawings in the embodiments of the present application to clearly and completely describe the technical solutions in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.
[0049] In the preparation process of MICRO-LED displays, the first thing to do is to prepare MICRO-LED chips. Generally, a gallium nitride buffer layer, an N-type semiconductor layer, a light-emitting layer and a P-type semiconductor layer are grown layer by layer on a sapphire substrate, wherein the N-type semiconductor layer, the light-emitting layer and the P-type semiconductor layer together constitute an LED epitaxial layer; then the light-emitting units are cut into an array, and the first electrode and the second electrode are made on the light-emitting units to form each LED chip.
[0050] In the process of growing the GaN buffer layer, there is a lattice mismatch problem between the sapphire substrate and GaN. The lattice mismatch can easily lead to the generation of dislocations and defects, which in turn affects the growth quality of GaN.
[0051] like Figure 1 As shown, in order to overcome this technical difficulty, the industry generally etches the surface of the sapphire substrate to make the surface of the sapphire substrate present a periodic micro-nano pattern of conical protrusions, namely a conical PASS (Patterned Sapphire Substrate) structure. The introduction of this structure can effectively alleviate the dislocation and defect problems caused by lattice mismatch.
[0052] However, since the surface of the sapphire substrate presents a periodic micro-nano pattern of conical protrusions, the surface of the matching gallium nitride buffer layer will present a periodic micro-nano pattern of conical pits. When the LED chip on the sapphire substrate is subsequently peeled off by laser, the gallium nitride buffer layer at the interface will absorb a large amount of photon energy and chemically decompose to form metal gallium and nitrogen, thereby generating nitrogen impact force along the direction of the laser to peel off the LED chip and sapphire substrate.
[0053] When performing the laser lift-off step, the light source is generally set on the side of the sapphire substrate away from the LED chip, and the laser beam is irradiated from the back perpendicular to the sapphire substrate, entering the gallium nitride buffer layer from the sapphire substrate. Since the refractive index of the sapphire material is lower than that of the gallium nitride material, the laser lift-off process is actually a process from a sparse medium to a dense medium, and the laser beam is refracted and deflected. Figure 2 As shown, the originally vertically incident light beam 1 is deflected to the left at the left inclined side of the conical convex structure, and the originally vertically incident light beam 2 is deflected to the right at the right inclined side of the conical convex structure; the nitrogen generated by the laser irradiation will act on the LED chip along the direction of the light beam, so the nitrogen generated by the light beam 1 will generate a component force to the left, and the nitrogen generated by the light beam 2 will generate a component force to the right, thereby generating a combined force to tear the LED chip, causing cracks in the LED chip, as shown in FIG. Figure 3 shown.
[0054] The purpose of this application is to provide a Micro-LED display and a method for preparing the same, which can improve the above-mentioned problems.
[0055] In a first aspect, the present application provides a method for preparing a Micro-LED display, comprising steps S1 to S4, wherein S1, S2, etc. are merely step identifiers, and the execution order of the method is not necessarily in ascending order of numbers, for example, step S2 may be executed first and then step S1, and the present application does not impose any limitation thereto.
[0056] S1, providing a sapphire substrate having a front surface and a back surface relatively disposed, and etching an array-arranged convex structure on the front surface; along a first direction perpendicular to the sapphire substrate and from the front surface to the back surface, the cross-section of the convex structure gradually increases, and the top of the convex structure is a plane parallel to the front surface.
[0057] S2, after growing a gallium nitride buffer layer on the front surface, sequentially growing epitaxial layers on the gallium nitride buffer layer, and preparing an LED chip.
[0058] S3, peeling the LED chip prepared on the sapphire substrate onto a temporary substrate by laser.
[0059] S4, the LED chips on the temporary substrate are transferred to the display backplane for packaging through a mass transfer process.
[0060] It can be understood that since the top of the terrace-shaped protruding structure is a plane, the nitrogen impact force in the refraction direction can be effectively separated to prevent the force components in the opposite horizontal direction from being too close to each other and thus tearing the LED epitaxial layer.
[0061] In an optional embodiment of the present application, the protrusion structure may be a truncated cone-shaped protrusion structure, such as Figure 4 As shown, the originally vertically incident light beam 3 is deflected to the left at the left inclined side of the truncated cone shaped protrusion structure, and the originally vertically incident light beam 4 is deflected to the right at the right inclined side of the truncated cone shaped protrusion structure. The nitrogen generated by the light beam 3 will generate a first component force to the left, and the nitrogen generated by the light beam 4 will generate a second component force to the right. Since the top of the truncated cone shaped protrusion structure is a plane that separates the first component force and the second component force, the combined force generated by the first component force and the second component force is difficult to tear the LED chip, thus avoiding the occurrence of cracks on the LED chip.
[0062] It can be understood that the truncated cone shaped protrusion structure is a symmetrical structure about the axis perpendicular to the center of the circle. When peeling the LED chip and the growth substrate, the refracted light of the laser passing through the inclined surface also diverges in the horizontal direction about the above axis. Therefore, when peeling the LED chip, the nitrogen impact force generated by the laser can be balanced in the horizontal direction, and the LED chip can be peeled off more stably.
[0063] Optionally, the distance between two adjacent truncated cone-shaped protrusion structures on the sapphire substrate is less than a preset distance value. Figure 5 As shown, the originally vertically incident light beam 5 is deflected to the left at the left inclined side of the truncated cone shaped protrusion structure, and the originally vertically incident light beam 6 is deflected to the right at the right inclined side of the truncated cone shaped protrusion structure. The nitrogen generated by light beam 5 will generate a third force component to the left, and the nitrogen generated by light beam 6 will generate a fourth force component to the right. Since the top of the truncated cone shaped protrusion structure is a plane that separates the third force component from the fourth force component, the difficulty of the combined force generated by the third force component and the fourth force component to tear the LED chip is increased. At this time, the adjacent third force component and fourth force component will form a thrust combined force for the spacing area S. Since the spacing area S is small enough, this thrust can be enhanced to more effectively peel off the LED chip.
[0064] In an optional embodiment of the present application, the protruding structure includes at least three side surfaces connected to the top, the at least three side surfaces include a single inclined surface and at least two vertical surfaces, the inclined surface is inclined relative to the front surface, the vertical surface is perpendicular to the front surface, and the inclination direction and inclination angle of each inclined surface in the sapphire substrate are consistent.
[0065] like Figure 6The convex structure shown includes a top surface 11, a first side surface 12, a second side surface 13, a third side surface 14 and a fourth side surface 15, wherein the first side surface 12 is an inclined surface. Figure 7 As shown, the originally vertically incident light beam deflects to the left after passing through the first side surface 12, thereby generating a nitrogen impact force to the left. At this time, if a pulling force in the opposite direction of the second horizontal direction is applied to the temporary substrate, the LED chip can be peeled off more easily.
[0066] It can be understood that the present application provides a method for preparing a Micro-LED display, in which a trapezoidal protrusion structure with an inclined surface is prepared on a sapphire substrate before growing a gallium nitride buffer layer and an LED epitaxial layer. When the LED chip and the sapphire substrate are peeled off by laser, the laser is refracted by the inclined surface, decomposes the gallium nitride along the refraction direction and generates a nitrogen impact force. Since the top of the trapezoidal protrusion structure is a plane, the nitrogen impact force in the refraction direction can be effectively separated to prevent the force components in the opposite horizontal direction from being too close and tearing the LED epitaxial layer. The method for preparing a Micro-LED display provided in the present application can prevent cracks in the LED chip and improve the reliability and service life of the display.
[0067] In an optional embodiment of the present application, S2 includes the following steps:
[0068] S21, growing a GaN buffer layer on the front surface;
[0069] S22, sequentially growing an N-type semiconductor layer, a light-emitting layer, and a P-type semiconductor layer on the gallium nitride buffer layer to form an epitaxial layer, wherein the thickness of the N-type semiconductor layer is greater than a preset thickness value;
[0070] S23, cutting the epitaxial layer into light-emitting units arranged in an array, and manufacturing a first electrode and a second electrode on the light-emitting units to form each LED chip.
[0071] It can be understood that when the LED chip and the growth substrate are peeled off, the gallium nitride buffer layer at the interface will absorb a large amount of photon energy and undergo chemical decomposition to form metal gallium and nitrogen, thereby generating a nitrogen impact force along the laser direction. If a nitrogen impact force component in the opposite horizontal direction is generated in the adjacent area, a tearing force may be generated in the LED epitaxial region. Thickening the N-type semiconductor layer to a thickness greater than the preset thickness value is conducive to alleviating the tearing effect generated by the tearing force, thereby avoiding cracks in the LED chip.
[0072] In an optional embodiment of the present application, S4 includes the following steps:
[0073] S41, such as Figure 8 As shown, the LED chip 10 on the temporary substrate is transferred to the display backplane 20 for welding through a mass transfer process.
[0074] In an optional embodiment of the present application, if Figure 8 As shown, the display backplane 20 includes a flexible substrate 21, a circuit layer 22 and a planarization layer 23 stacked in sequence; electrode pad pairs are arrayed on the planarization layer 23, and the electrode pad pairs are connected to the circuit layer 22 through conductive through holes. Each electrode pad pair includes a first electrode pad 24 and a second electrode pad 25. The first electrode pad 24 is used to be welded to the first electrode 31 of the LED chip 10, and the second electrode pad 25 is used to be welded to the second electrode 32 of the LED chip 10.
[0075] S42, such as Fig. 9 As shown, the packaging glue 40 is coated on the display back plate 20 and covers the LED chip.
[0076] S43, such as Fig. 9 As shown, a protection layer 50 is covered on the packaging glue 40 .
[0077] In an optional embodiment of the present application, if Fig.10 As shown, after S41 and before S42, the following steps are also included: on the flat layer 40, a piezoelectric unit 60 is arranged between adjacent LED chips, and the piezoelectric unit 60 is subjected to a squeezing force when it is bent during curling, thereby generating positive charges on the front side of the piezoelectric unit 60 and negative charges on the negative side of the piezoelectric unit.
[0078] In an optional embodiment of the present application, the circuit layer includes drive circuit units arranged in an array, and the drive circuit units are used to drive the brightness of a single LED chip. Fig.11 As shown, the driving circuit unit includes a first thin film transistor T1, a second thin film transistor T2, a capacitor C and a voltage-dividing resistor R1; the source electrode s of the first thin film transistor T1 is connected to the data signal line DATA of the circuit layer, and the gate electrode g of the first thin film transistor T1 is connected to the scanning signal line SCAN of the circuit layer; the source electrode s of the second thin film transistor T2 is connected to the positive power supply electrode Vdd of the circuit layer, the gate electrode g of the second thin film transistor T2 is connected to the drain electrode d of the first thin film transistor T1, and a capacitor C is further connected between the gate electrode g and the drain electrode d of the second thin film transistor T2; the drain electrode d of the second thin film transistor T2 is connected in series with the corresponding LED chip and the voltage-dividing resistor R1 in sequence and then grounded, the connection point between the LED chip and the voltage-dividing resistor R1 is connected to the front side of the piezoelectric unit 60, and the negative side of the piezoelectric unit is grounded.
[0079] It can be understood that for roll-up screen terminal devices, it is often necessary to change the display brightness according to the bending angle of the screen. For example, the display screen needs to gradually light up during the screen extension process, and the display screen needs to gradually stop displaying during the screen extension process. Conventional practices require adding an angle detection device to monitor the curling angle of the screen, and control the display brightness through a processor. The present application sets a piezoelectric unit in the flat layer of the display. The piezoelectric unit is subjected to a squeezing force when it bends during curling, thereby generating a positive charge on the front side of the piezoelectric unit and a negative charge on the negative side of the piezoelectric unit. The piezoelectric unit is connected in parallel with the voltage divider resistor R1 of the LED chip, and generates a piezoelectric voltage during the curling process to reduce the voltage difference across the LED chip, so that the display gradually stops displaying; the piezoelectric voltage decreases during the screen extension process, thereby restoring the voltage difference across the LED chip, and the display gradually lights up again.
[0080] In a second aspect, the present application discloses a Micro-LED display prepared by any method of the first aspect.
[0081] The expressions "first", "second", "the first" or "the second" used in various embodiments of the present disclosure may modify various components regardless of order and / or importance, but these expressions do not limit the corresponding components. The above expressions are only configured for the purpose of distinguishing an element from other elements. For example, a first user device and a second user device represent different user devices, although both are user devices. For example, a first element may be referred to as a second element, and similarly, a second element may be referred to as a first element without departing from the scope of the present disclosure.
[0082] When one element (e.g., a first element) is referred to as being "(operably or communicatively) coupled" or "(operably or communicatively) coupled to" or "connected to" another element (e.g., a second element), it is understood that the one element is directly connected to the other element or the one element is indirectly connected to the other element via yet another element (e.g., a third element). Conversely, it is understood that when an element (e.g., a first element) is referred to as being "directly connected" or "directly coupled" to another element (the second element), no element (e.g., a third element) is interposed between the two.
[0083] It should be noted that, in this article, the terms "include", "comprises" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also includes other elements not explicitly listed, or also includes elements inherent to such process, method, article or device. In the absence of further restrictions, an element defined by the sentence "includes a ..." does not exclude the existence of other identical elements in the process, method, article or device including the element. In addition, components, features, and elements with the same name in different embodiments of the present application may have the same meaning or different meanings, and their specific meanings need to be determined by their explanation in the specific embodiment or further combined with the context of the specific embodiment.
[0084] The above description is only an optional embodiment of the present application and an explanation of the technical principles used. Those skilled in the art should understand that the scope of the invention involved in the present application is not limited to the technical solution formed by a specific combination of the above technical features, but should also cover other technical solutions formed by any combination of the above technical features or their equivalent features without departing from the above invention concept. For example, the above features are replaced with the technical features with similar functions disclosed in this application (but not limited to) by each other.
[0085] As used herein, the words "if" and "if" may be interpreted as "at the time of" or "when" or "in response to determining" or "in response to detecting", depending on the context. Similarly, the phrases "if it is determined" or "if (stated condition or event) is detected" may be interpreted as "when it is determined" or "in response to determining" or "when detecting (stated condition or event)" or "in response to detecting (stated condition or event)", depending on the context.
[0086] The above description is only an optional embodiment of the present application and an explanation of the technical principles used. Those skilled in the art should understand that the scope of the invention involved in the present application is not limited to the technical solution formed by a specific combination of the above technical features, but should also cover other technical solutions formed by any combination of the above technical features or their equivalent features without departing from the above invention concept. For example, the above features are replaced with the technical features with similar functions disclosed in this application (but not limited to) by each other.
[0087] The above description is only an optional embodiment of the present application and is not intended to limit the present application. For those skilled in the art, the present application may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.
Claims
1. A method for preparing a Micro-LED display, characterized in that: The following steps are involved: S1, providing a sapphire substrate having a front surface and a back surface arranged opposite to each other, and etching a convex structure arranged in an array on the front surface; Along a first direction perpendicular to the sapphire substrate and from the front surface to the back surface, the cross section of the protruding structure gradually becomes larger, and the top of the protruding structure is a plane parallel to the front surface; S2, after growing a gallium nitride buffer layer on the front surface, sequentially growing epitaxial layers on the gallium nitride buffer layer, and preparing an LED chip; S3, peeling the LED chip prepared on the sapphire substrate onto a temporary substrate by laser; S4, transferring the LED chip on the temporary substrate to a display backplane for packaging through a mass transfer process.
2. The method for preparing a Micro-LED display according to claim 1, characterized in that: The protrusion structure includes at least one of the following: The protrusion structure is a truncated cone-shaped protrusion structure; The raised structure includes at least three side surfaces connected to the top, and the at least three side surfaces include a single inclined surface and at least two vertical surfaces. The inclined surface is inclined relative to the front surface, and the vertical surface is perpendicular to the front surface. The inclination direction and inclination angle of each of the inclined surfaces in the sapphire substrate are consistent.
3. The method for preparing a Micro-LED display according to claim 2, characterized in that: The distance between two adjacent truncated cone-shaped protruding structures on the sapphire substrate is less than a preset distance value.
4. The method for preparing a Micro-LED display according to claim 2, characterized in that: The S3 includes at least one of the following: Starting a laser light source to irradiate the sapphire substrate in a direction opposite to the first direction; The laser generates a light beam toward a second horizontal direction through the inclined surface, and applies a pulling force in a direction opposite to the second horizontal direction to the temporary substrate.
5. The method for preparing a Micro-LED display according to any one of claims 1 to 4, characterized in that: The S2 comprises the following steps: S21, growing a gallium nitride buffer layer on the front surface; S22, sequentially growing an N-type semiconductor layer, a light-emitting layer, and a P-type semiconductor layer on the gallium nitride buffer layer to form an epitaxial layer, wherein the thickness of the N-type semiconductor layer is greater than a preset thickness value; S23, cutting the epitaxial layer into light-emitting units arranged in an array, and manufacturing a first electrode and a second electrode on the light-emitting units to form each LED chip.
6. The method for preparing a Micro-LED display according to claim 5, characterized in that: The S4 comprises the following steps: S41, transferring the LED chip on the temporary substrate to a display backplane for welding through a mass transfer process; S42, applying packaging glue on the display back panel and covering the LED chip; S43, covering the packaging adhesive with a protective layer.
7. The method for preparing a Micro-LED display according to claim 6, characterized in that: The display backplane includes a flexible substrate, a circuit layer and a planarization layer stacked in sequence; electrode pad pairs are arranged in an array on the planarization layer, and the electrode pad pairs are connected to the circuit layer through conductive through holes. Each electrode pad pair includes a first electrode pad and a second electrode pad, the first electrode pad is used to be welded to the first electrode, and the second electrode pad is used to be welded to the second electrode.
8. The method for preparing a Micro-LED display according to claim 7, characterized in that: The following steps are also included after S41 and before S42: On the flat layer, a piezoelectric unit is arranged between adjacent LED chips. The piezoelectric unit is subjected to a squeezing force when it is bent during the curling process, thereby generating positive charges on the front side of the piezoelectric unit and negative charges on the negative side of the piezoelectric unit.
9. The method for preparing a Micro-LED display according to claim 8, characterized in that: The circuit layer includes a driving circuit unit arranged in an array, and the driving circuit unit includes a first thin film transistor, a second thin film transistor, a capacitor and a voltage dividing resistor; The source of the first thin film transistor is connected to the data signal line of the circuit layer, and the gate of the first thin film transistor is connected to the scanning signal line of the circuit layer; The source electrode of the second thin film transistor is connected to the positive electrode of the power supply of the circuit layer, the gate electrode of the second thin film transistor is connected to the drain electrode of the first thin film transistor, and the capacitor is further connected between the gate electrode and the drain electrode of the second thin film transistor; The drain of the second thin film transistor is connected in series with the corresponding LED chip and the voltage-dividing resistor and then grounded. The connection point between the LED chip and the voltage-dividing resistor is connected to the front side of the piezoelectric unit, and the negative side of the piezoelectric unit is grounded.
10. A Micro-LED display, characterized in that: Prepared by any one of the methods of claims 1 to 9.