Micro light emitting diode display panel and preparation method thereof

Abstract

The embodiment of the present application provides a micro-LED display panel and a method for preparing the same. The preparation method includes: preparing an epitaxial layer on one side of a substrate, the epitaxial layer includes a first semiconductor layer, a light-emitting material layer, a second semiconductor layer and a first conductive layer, the first semiconductor layer is in direct contact with the substrate, and the first conductive layer is the film layer farthest from the substrate in the epitaxial layer; dividing the epitaxial layer into a plurality of LED grains arranged in an array; providing a backplane, and making a binding structure on the backplane; binding the first conductive layer of at least part of the plurality of LED grains to the binding structure; and peeling the LED grains bound to the binding structure from the substrate. The embodiment of the present application improves the transfer efficiency and transfer accuracy of mass transfer, and can realize the transfer of micro-LED grains with vertical electrode structures.

Description

Technical Field

[0001] The present application relates to the field of display technology, and in particular, to a micro light emitting diode display panel and a method for preparing the same. Background Art

[0002] In the preparation process of micro light emitting diode (Micro LED) display panels, mass transfer is usually required after the epitaxial process is completed.

[0003] Mass transfer refers to the correct and efficient transfer of millions or even tens of millions of micron-sized Micro LED grains to the circuit substrate. Taking a 4K three-color display (UHD TV with a display resolution of 3840×2160 and above, which is 8 times that of HD and 4 times that of full HD) as an example, the number of grains that need to be transferred is as high as 24 million (4000×2000×3). Even if 10,000 grains are transferred at a time, it needs to be repeated 2,400 times.

[0004] Among the existing mass transfer technologies, laser transfer is popular in the industry for its advantages of high reliability, high yield, high scalability, high selectivity and high success rate. However, the commonly used laser transfer has the following defects: it requires at least one carrier (paste substrate or transfer substrate) as a transfer layer, there are many transfer links and devices to cooperate with the transfer, the transfer efficiency is low, and the transfer accuracy is limited; currently, it can only realize the transfer of Micro LEDs with horizontal electrode structures, and it is difficult to realize the transfer of Micro LEDs with vertical electrode structures, and the compatibility is insufficient. Summary of the invention

[0005] In view of the shortcomings of the existing methods, the present application proposes a micro light emitting diode display panel and a preparation method thereof, so as to solve the technical problems of low transfer efficiency, limited transfer accuracy or difficulty in transferring micro light emitting diode grains with horizontal electrode structures in the existing technology.

[0006] In a first aspect, an embodiment of the present application provides a method for preparing a micro light emitting diode display panel, comprising:

[0007] An epitaxial layer is prepared on one side of the substrate, wherein the epitaxial layer includes a first semiconductor layer, a light emitting material layer, a second semiconductor layer and a first conductive layer, wherein the first semiconductor layer is in direct contact with the substrate, and the first conductive layer is the film layer farthest from the substrate in the epitaxial layer;

[0008] Dividing the epitaxial layer into a plurality of light emitting diode grains arranged in an array;

[0009] Providing a back plate and making a binding structure on the back plate;

[0010] Binding the first conductive layers of at least some of the light emitting diode dies among the plurality of light emitting diode dies to the binding structure;

[0011] The light emitting diode die bonded to the bonding structure is peeled off from the substrate base material.

[0012] In a second aspect, an embodiment of the present application provides a micro light emitting diode display panel, comprising: a back panel and a plurality of light emitting diode dies;

[0013] Each of the plurality of light-emitting diode crystals comprises a first semiconductor layer, a light-emitting material layer, a second semiconductor layer and a first conductive layer which are stacked;

[0014] The first conductive layer is bonded to the bonding structure on the backplane;

[0015] The second semiconductor layer is located on a side of the first conductive layer away from the back plate;

[0016] The light emitting material layer is located on a side of the second semiconductor layer away from the first conductive layer;

[0017] The first semiconductor layer is located on a side of the light emitting material layer away from the second semiconductor layer.

[0018] The beneficial technical effects brought about by the preparation method of the micro-LED display panel provided in the embodiment of the present application include: preparing a plurality of LED grains with a vertical electrode structure arranged in an array on a substrate, and using selective stripping to directly transfer the specified LED grains to the target backplane, that is, using a one-time transfer, without the need to use a pasting substrate or a transfer substrate as a transfer, thereby simplifying the transfer process, reducing the number of devices involved in the transfer, and greatly improving the transfer efficiency and transfer accuracy; the prepared LED grains are a vertical electrode structure, which improves the limitation of the prior art that only the transfer of LED grains with a horizontal electrode structure can be achieved, realizes the transfer of LED grains with a vertical electrode structure, and improves the compatibility of mass transfer.

[0019] The beneficial technical effects brought about by the micro-light emitting diode display panel and display device provided in the embodiments of the present application include: using a micro-light emitting diode with a vertical electrode structure, so that the current almost entirely flows vertically through the epitaxial layer of the micro-light emitting diode, with very little current flowing horizontally, which is beneficial to the diffusion of current and the dissipation of heat, and can meet the development trend of high power.

[0020] Additional aspects and advantages of the present application will be partially given in the following description, which will become apparent from the following description, or will be understood through the practice of the present application. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] The above and / or additional aspects and advantages of the present application will become apparent and easily understood from the following description of the embodiments in conjunction with the accompanying drawings, in which:

[0022] Figure 1 A schematic diagram of a process for preparing a micro light emitting diode display panel provided in an embodiment of the present application;

[0023] Figure 2 A schematic flow chart of another method for preparing a micro light emitting diode display panel provided in an embodiment of the present application;

[0024] Figure 3 A schematic flow chart of another method for preparing a micro light emitting diode display panel provided in an embodiment of the present application;

[0025] Figure 4 A schematic diagram of the structure of the substrate and the backplane obtained after preparing an epitaxial layer on one side of the substrate in step S201, dividing the epitaxial layer into a plurality of light-emitting diode grains arranged in an array in step S202, and providing a backplane in step S203, and making a binding structure on the backplane;

[0026] Figure 5 is a schematic diagram of the positional relationship between the substrate base material and the backplane obtained after the first conductive layers of at least some of the plurality of LED dies are bound to the binding structure in step S204;

[0027] Figure 6 It is a schematic diagram of a peeling state in which the light-emitting diode die bound to the binding structure is peeled off from the substrate in step S205;

[0028] Figure 7 A schematic diagram of the structure of a light-emitting diode grain obtained by laser ablation for cambering provided in an embodiment of the present application;

[0029] Figure 8 A schematic diagram of a top view of a micro light emitting diode display panel provided in an embodiment of the present application;

[0030] Fig. 9 for Figure 8 Schematic diagram of a cross-sectional structure of the ZZ plane.

[0031] in:

[0032] 100-back plate; 110-binding structure; 120-driving device;

[0033] 200-substrate base material;

[0034] 300-light-emitting diode grain; 310-first conductive layer; 320-second semiconductor layer; 330-light-emitting material layer; 340-first semiconductor layer; 340a-arc surface; 350-top electrode layer; 350a-arc region; 360-second electrode pattern;

[0035] 400-Mask plate. DETAILED DESCRIPTION

[0036] The present application is described in detail below, and examples of embodiments of the present application are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar components or components with the same or similar functions. In addition, if the detailed description of the known technology is unnecessary for the features of the present application shown, it will be omitted. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present application, and cannot be interpreted as limiting the present application.

[0037] It will be understood by those skilled in the art that, unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as those generally understood by those skilled in the art to which this application belongs. It should also be understood that terms such as those defined in general dictionaries should be understood to have meanings consistent with those in the context of the prior art, and will not be interpreted with idealized or overly formal meanings unless specifically defined as here.

[0038] It will be understood by those skilled in the art that, unless expressly stated, the singular forms "one", "said", and "the" used herein may also include plural forms. It should be further understood that the term "comprising" used in the specification of the present application refers to the presence of the features, integers, steps, operations, elements and / or components, but does not exclude the presence or addition of one or more other features, integers, steps, operations, elements, components and / or groups thereof. It should be understood that when we refer to an element as being "connected" or "coupled" to another element, it may be directly connected or coupled to the other element, or there may be an intermediate element. In addition, the "connection" or "coupling" used herein may include wireless connection or wireless coupling. The term "and / or" used herein includes all or any unit and all combinations of one or more associated listed items.

[0039] The inventors of this application conducted research and found that in the existing mass transfer technology, the currently commonly used laser transfer has the following defects: at least one carrier (adhesive substrate or transfer substrate) is required as a transfer layer, there are many transfer links and devices to cooperate with the transfer, the transfer efficiency is low, and the transfer accuracy is limited; currently, only the transfer of MicroLEDs with horizontal electrode structures can be achieved, and the compatibility is insufficient.

[0040] The micro light emitting diode display panel and the preparation method thereof provided in the present application are intended to solve the above technical problems of the prior art.

[0041] The technical solution of the present application and how the technical solution of the present application solves the above-mentioned technical problems are described in detail below with specific embodiments.

[0042] The present application provides a method for preparing a micro light emitting diode display panel. The process diagram of the preparation method is shown in FIG. Figure 1 As shown, steps S101-S105 are included:

[0043] S101. Prepare an epitaxial layer on one side of the substrate base material 200. The epitaxial layer includes a first semiconductor layer 340, a light-emitting material layer 330, a second semiconductor layer 320 and a first conductive layer 310. The first semiconductor layer 340 is in direct contact with the substrate base material 200. The first conductive layer 310 is the film layer farthest from the substrate base material 200 in the epitaxial layer.

[0044] S102: Divide the epitaxial layer into a plurality of light emitting diode chips 300 arranged in an array, and then execute step S104.

[0045] S103 : providing a backplane 100 , and manufacturing a binding structure 110 on the backplane 100 .

[0046] S104 : Binding the first conductive layer 310 of at least some of the LED dies 300 among the plurality of LED dies 300 to the binding structure 110 .

[0047] S105 : peeling the light emitting diode die 300 bound to the binding structure 110 from the substrate base material 200 .

[0048] In this embodiment, a plurality of light-emitting diode grains 300 with vertical electrode structures arranged in an array are prepared on a substrate base material 200, and selective stripping is used to directly transfer the designated light-emitting diode grains 300 to a target backplane 100, i.e., a one-time transfer is used without using an adhesive substrate or a transfer substrate as a transfer, thereby simplifying the transfer process, reducing the number of devices involved in the transfer, and greatly improving the transfer efficiency and transfer accuracy.

[0049] In the epitaxial layer prepared on the substrate 200, the first semiconductor layer 340 is in direct contact with the substrate 200, and the first conductive layer 310 is located in the film layer farthest from the substrate 200 in the epitaxial layer, and is used to be bound to the binding structure 110 of the backplane 100. The prepared epitaxial layer is a vertical electrode structure, and the multiple light-emitting diode grains 300 obtained after the epitaxial layer array is divided are also vertical electrode structures, which improves the limitation of the prior art that only the light-emitting diode grains 300 with a horizontal electrode structure can be transferred, and realizes the transfer of the light-emitting diode grains 300 with a vertical electrode structure, thereby improving the compatibility of mass transfer.

[0050] In some possible implementations, Figure 1 The provided preparation method can first execute steps S101-S102 to complete the preparation of multiple LED grains 300 arranged in an array on one side of the substrate base material 200, then execute step S103 to make a binding structure 110 on the backplane 100, and then execute steps S104-S105 to complete the binding of at least part (i.e., specified) of the LED grains 300 to the binding structure 110 on the backplane 100, and peel off this part of the LED grains 300 from one side of the substrate base material 200.

[0051] In some possible implementations, Figure 1 The provided preparation method can first execute step S103 to make a binding structure 110 on the backplane 100, then execute steps S101-S102 to complete the preparation of multiple LED grains 300 arranged in an array on one side of the substrate base material 200, and then execute steps S104-S105 to complete the binding of at least part (i.e., specified) of the LED grains 300 to the binding structure 110 on the backplane 100, and peel off this part of the LED grains 300 from one side of the substrate base material 200.

[0052] In some possible implementations, Figure 1 The provided preparation method performs step S103 during the process of performing steps S101-S102, and then performs steps S104-S105.

[0053] The present application provides another method for preparing a micro-LED display panel. The process diagram of the method is shown in FIG. Figure 2 As shown, the method includes steps S201-S207:

[0054] S201: Prepare an epitaxial layer on one side of the substrate base material 200, the epitaxial layer includes a first semiconductor layer 340, a light emitting material layer 330, a second semiconductor layer 320 and a first conductive layer 310, the first semiconductor layer 340 is in direct contact with the substrate base material 200, and the first conductive layer 310 is the film layer farthest from the substrate base material 200 in the epitaxial layer.

[0055] After the above step S201, an epitaxial layer of a vertical electrode structure can be obtained on one side of the substrate 200, which is ready for the next step of obtaining an array of light-emitting diode grains 300 of a vertical electrode structure. The first semiconductor layer 340 in the epitaxial layer is in direct contact with the substrate 200, which can facilitate the subsequent peeling of the light-emitting diode grains 300 from one side of the substrate 200. The first conductive layer 310 is the film layer farthest from the substrate 200 in the epitaxial layer, which can facilitate the subsequent binding of the light-emitting diode grains 300 to the binding structure 110 on the backplane 100.

[0056] Optionally, the substrate 200 may be made of a transparent material, so that when laser stripping is subsequently performed, the laser passes through the substrate 200 and acts on the surface of the light-emitting diode crystal 300 where the first semiconductor layer 340 contacts the substrate 200, thereby stripping the light-emitting diode crystal 300 from one side of the substrate 200. Optionally, the substrate 200 may be sapphire.

[0057] Optionally, the first semiconductor layer 340 is an N-type semiconductor, and can be made of gallium nitride material. Gallium nitride material can be decomposed into nitrogen and metal gallium under the ablation effect of laser, which is conducive to the subsequent laser lift-off.

[0058] Optionally, the second semiconductor layer 320 is a P-type semiconductor, and may also be made of gallium nitride.

[0059] Optionally, the light emitting material layer 330 includes a multi-quantum well structure.

[0060] S202: Divide the epitaxial layer into a plurality of light emitting diode chips 300 arranged in an array, and then execute step S204.

[0061] In some possible implementations, the epitaxial layer is divided into a plurality of light-emitting diode grains 300 arranged in an array in the above step S202, including: performing array etching on the first semiconductor layer 340, the light-emitting material layer 330, the second semiconductor layer 320 and the first conductive layer 310. The array etching can be achieved with the aid of a mask plate, and the pattern on the mask plate is adapted to the target array of light-emitting diode grains 300, that is, the hollowed-out area on the mask plate corresponds to the gap between each light-emitting diode grain 300 in the array of light-emitting diode grains 300. After the above operation, a plurality of light-emitting diode grains 300 with a vertical electrode structure arranged in an array can be obtained on one side of the substrate 200.

[0062] In some other possible embodiments, the epitaxial layer is divided into a plurality of light-emitting diode grains 300 arranged in an array in the above step S202, including: the first semiconductor layer 340, the light-emitting material layer 330, the second semiconductor layer 320 and the first conductive layer 310 are subjected to array etching to obtain a plurality of light-emitting diode grains 300 arranged in an array; the cross-sectional shape of any one of the plurality of light-emitting diode grains 300 is a trapezoid or a circle, and the cross-sectional shape is parallel to the plane where the substrate base material 200 is located.

[0063] After the above operation, not only can a plurality of light-emitting diode crystal grains 300 with vertical electrode structures arranged in an array be obtained on one side of the substrate 200, but the cross-sectional shape of the obtained light-emitting diode crystal grains 300 parallel to the substrate 200 can also be made into a trapezoidal or circular shape. Specifically, the mask plate used in the array etching can be adjusted so that the pattern on the mask plate is adapted to the cross-sectional shape of each light-emitting diode crystal grain 300 in the light-emitting diode crystal grain 300 array.

[0064] The obtained light-emitting diode grain 300 has a trapezoidal or circular cross-sectional shape, that is, a structure with a gradually increasing cross-sectional shape along the laser scanning direction can be formed. When the light-emitting diode grain 300 is subsequently peeled off from one side of the substrate base material 200 by laser peeling, the area of ​​the first semiconductor layer 340 ablated by the laser along the laser scanning direction gradually increases, which can facilitate the rapid separation of a large amount of gas generated by the laser peeling from the first semiconductor layer 340 from the light-emitting diode grain 300, and can avoid the accumulation of rapidly generated gas inside the light-emitting diode grain 300, which may cause the light-emitting diode grain 300 to break.

[0065] Optionally, when the cross section of the LED die 300 parallel to the substrate 200 is a trapezoidal cross section, the upper base of the trapezoidal cross section is located upstream in the laser scanning direction of the laser lift-off, and the lower base of the trapezoidal cross section is located downstream in the laser scanning direction of the laser lift-off. Figure 8 As shown, Figure 8 The solid arrow in the figure indicates the laser scanning direction during laser stripping; Figure 8 The dotted arrow in the figure indicates the exhaust direction.

[0066] It is understandable that the aforementioned array etching of the cross section of the light-emitting diode grain 300 parallel to the substrate base material 200 may also include other shaped array etchings, as long as the size at the upstream end in the laser scanning direction is smaller than the size at the midstream part. For example, the first semiconductor layer 340, the light-emitting material layer 330, the second semiconductor layer 320 and the first conductive layer 310 are subjected to triangular patterning or elliptical patterning array etching.

[0067] S203 : providing a backplane 100 , and manufacturing a binding structure 110 on the backplane 100 .

[0068] In some possible embodiments, the manufacturing of the binding structure 110 on the backplane 100 in the above step S203 may include the steps of: depositing a conductive layer for binding on the backplane 100, and adaptively patterning the conductive layer for binding on the backplane 100 according to the distribution of the first conductive layer 310 of at least part of the light-emitting diode grains 300 on the substrate base material 200, that is, the distribution of the first conductive layer 310 of the specified light-emitting diode grains 300 on the substrate base material 200400, to obtain the binding structure 110.

[0069] Optionally, the back plate 100 may further include a driving device 120 for driving the light emitting diode grain 300 to emit light, such as a TFT (Thin Film Transistor) or a μIC (micro control circuit).

[0070] After steps S201-S203, the obtained structures of the substrate 200 and the backplane 100 are as follows. Figure 4 As shown, a plurality of light-emitting diode dies 300 with vertical electrode structures arranged in an array are manufactured on the substrate base material 200 , and a binding structure 110 for binding selected light-emitting diode dies 300 is manufactured on the back plate 100 .

[0071] S204 : Binding the first conductive layer 310 of at least some of the LED dies 300 among the plurality of LED dies 300 to the binding structure 110 .

[0072] In the step S204 , the first conductive layer 310 of at least some of the LED dies 300 is bonded to the bonding structure 110 , which may include: bonding the first conductive layer 310 of at least some of the LED dies 300 to the bonding structure 110 through a eutectic reaction.

[0073] After step S204, the positional relationship between the substrate 200 and the backplane 100 is as follows: Figure 5 At this time, the first conductive layer 310 of the light-emitting diode die 300 and the binding structure 110 on the back plate 100 have been bound.

[0074] S205 : peeling the light emitting diode die 300 bound to the binding structure 110 from the substrate base material 200 .

[0075] In some possible embodiments, the light-emitting diode crystal 300 bound to the binding structure 110 is peeled off from the substrate base material 200 in the above-mentioned step S205, including: laser ablation of the first semiconductor layer 340 of the light-emitting diode crystal 300 bound to the binding structure 110 to separate the first semiconductor layer 340 of the light-emitting diode crystal 300 from the substrate base material 200.

[0076] The peeling in step S205 is performed by taking laser peeling as an example. Figure 6 As shown, Figure 6 The arrow in the figure indicates the direction of laser irradiation. A mask plate 400 may be used, and the hollowed-out area on the mask plate 400 corresponds to each LED grain 300 bound to the binding structure 110 in the LED grain 300 array, so that the laser passes through the hollowed-out portion of the pattern on the mask plate 400, passes through the substrate 200, and acts on the surface of the first semiconductor layer 340 of the designated micro-LED grain 300 directly contacting the substrate 200, decomposing the surface of the first semiconductor layer 340 made of gallium nitride connected to the substrate 200 into nitrogen and metal gallium, thereby achieving laser lift-off.

[0077] Optionally, laser stripping can be performed using a laser device such as an Excimer 248nm laser or a 266nm DPSS laser, in combination with a DOE (Diffractive Optical Elements) or a galvanometer and a mask plate 400 to achieve laser stripping.

[0078] Optionally, in the aforementioned method, laser ablation is performed on the first semiconductor layer 340 of the LED crystal 300 bound to the binding structure 110, including: performing arc-forming laser ablation on a surface of the first semiconductor layer 340 of the LED crystal 300 away from the back plate 100.

[0079] In this embodiment, since the light wavefront of the point light source is a curved surface 340a, and during the laser ablation process, the edge of the hollow area on the mask plate 400 can have a certain shielding effect on the laser ablation, that is, the rate at which the first semiconductor layer 340 corresponding to the edge of the hollow area on the mask plate is ablated by the laser will be lower than the rate at which the first semiconductor layer 340 corresponding to the center of the hollow area on the mask plate is ablated by the laser. By utilizing this ablation rate difference, the side surface of the first semiconductor layer 340 away from the back plate 100 can be ablated to obtain a curved surface, and then the required depth of the curved surface 340a can be obtained by controlling the intensity and irradiation time of the laser. After the aforementioned curved surface laser ablation, the side surface of the first semiconductor layer 340 of the light-emitting diode grain 300 away from the light-emitting material layer 330 can form a curved surface 340a structure that is concave toward the light-emitting material layer 330. The structure of the light-emitting diode grain 300 is as shown in FIG. Figure 7 The arc surface 340a structure on the first semiconductor layer 340 of the LED chip 300 can reduce the current crowding of the LED chip 300 with the vertical electrode structure, and can increase the light extraction current efficiency. Since the first conductive layer 310 of the LED chip 300 and the binding structure 110 can be bound by eutectic reaction, Figure 7 and Fig. 9 The first conductive layer 310 and the binding structure 110 after binding are regarded as the same film layer structure.

[0080] S206 : forming a top conductor layer (TCL) layer on a side of the first semiconductor layer 340 of the light emitting diode die 300 away from the back plate 100 .

[0081] S207 : manufacturing a second electrode pattern 360 on a side of the top electrode layer 350 away from the back plate 100 .

[0082] After step S206 and step S207, the following can be obtained: Fig. 9 The display panel structure shown. Fig. 9 The solid arrow in the figure indicates the light emission direction of the display panel. Fig. 9 The dotted arrows in the diagram indicate two conductive paths from the first conductive layer 310 to the second electrode pattern 360 in the structure of the light-emitting diode die 300. R1 is the equivalent resistance of one of the conductive paths (i.e., a path that faces the second electrode pattern 360 in a direction perpendicular to the first conductive layer 310). R2 is the equivalent resistance of the other conductive path (i.e., a path that does not face the second electrode pattern 360 in a direction perpendicular to the first conductive layer 310). The resistance from the first conductive layer 310 to the first semiconductor layer 340 (specifically, to the boundary of the first semiconductor layer 340 near the TCL layer) is R TCL is another path through the equivalent resistance in the TCL layer. It can be seen that after the surface of the first semiconductor layer 340 of the light-emitting diode crystal grain 300 away from the light-emitting material layer 330 is cambered, R2+R TCL The value can be closer to R1 or even R2+R TCL The value of can be equal to R1, that is, the current crowding existing in the light emitting diode chip 300 with a vertical electrode structure can be reduced, and the light extraction current efficiency can be increased.

[0083] It can be understood that, similar to the method for preparing a micro-light-emitting diode display panel provided in one of the aforementioned embodiments, in another method for preparing a micro-light-emitting diode display panel provided in this embodiment, the order of steps S201-S202 and step S203 does not need to be strictly specified, and steps S201-S202 may be executed before step S203, or after step S203, or steps S201-S202 and step S203 may be executed simultaneously.

[0084] The present application provides another method for preparing a micro-LED display panel. The process diagram of the method is as follows: Figure 3 As shown, the method includes steps S301-S307:

[0085] S301: Prepare an epitaxial layer on one side of the substrate base material 200, the epitaxial layer includes a first semiconductor layer 340, a light emitting material layer 330, a second semiconductor layer 320 and a first conductive layer 310, the first semiconductor layer 340 is in direct contact with the substrate base material 200, and the first conductive layer 310 is the film layer farthest from the substrate base material 200 in the epitaxial layer.

[0086] S302: Divide the epitaxial layer into a plurality of light emitting diode chips 300 arranged in an array, and then execute step S304.

[0087] S303 : providing a backplane 100 , and manufacturing a binding structure 110 on the backplane 100 .

[0088] S304 : Binding the first conductive layer 310 of at least some of the LED dies 300 among the plurality of LED dies 300 to the binding structure 110 .

[0089] S305 : peeling the light emitting diode die 300 bound to the binding structure 110 from the substrate base material 200 .

[0090] S306 : manufacturing a second electrode pattern 360 on a side of the light emitting diode die 300 away from the back plate 100 .

[0091] S307 : using the second electrode pattern 360 as a mask, performing laser ablation on a surface of the first semiconductor layer 340 of the light-emitting diode chip 300 that is away from the light-emitting material layer 330 to form a curved surface.

[0092] The present embodiment provides another method for preparing a micro-LED display panel, which is basically the same as the principle of the aforementioned method for preparing another micro-LED display panel, except that: after the laser stripping of the first semiconductor layer 340 of the LED crystal 300 and the substrate 200 is completed, the second electrode pattern 360 is firstly made on the side of the LED crystal 300 away from the back plate 100, and then the second electrode pattern 360 is used as a mask to perform laser ablation of the surface of the first semiconductor layer 340 away from the light-emitting material layer 330 to form a curved surface. The present embodiment has the beneficial effect that the second electrode pattern 360 is made before the laser ablation of the curved surface of the first semiconductor layer 340, and the mask plate used to make the second electrode pattern 360 does not need to be designed according to the surface structure of the first semiconductor layer 340 that has been curved, which can reduce the difficulty of making the second electrode pattern 360.

[0093] Optionally, the second electrode pattern 360 may be a ring-shaped electrode pattern to cooperate with the first semiconductor layer 340 of the light-emitting diode chip 300 to form a curved surface 340a structure recessed toward the light-emitting material layer 330 on the side surface away from the light-emitting material layer 330, thereby improving the current distribution uniformity and conductivity within the vertically structured light-emitting diode chip 300.

[0094] Optionally, in any of the above preparation methods, the laser ablation satisfies at least one of the following conditions AD:

[0095] Condition A: The laser irradiation frequency of laser ablation is 0.1 Hz-1 kHz (Hertz), and can be matched with an appropriate duty cycle or pulse period.

[0096] Condition B: The ambient atmosphere for laser ablation includes air with a humidity lower than 5%, such as CDA (ie, Cold Dry Air).

[0097] Condition C: The laser ablation environment includes atomized hydrogen chloride with a concentration greater than 0.1 molar concentration, which is conducive to removing the metal gallium obtained by the decomposition of gallium nitride under the action of laser. Specifically, using CDA as a carrier and hydrogen chloride as a corrosive solvent to form an aerosol suspended in CDA, the metal gallium obtained by the decomposition of gallium nitride is dissolved and removed, which can accelerate the process and avoid the decrease in process uniformity or stripping rate due to the accumulation of gallium metal.

[0098] Condition D: Laser ablation was cooled with nitrogen gas at a temperature below 25°C.

[0099] Based on the same inventive concept, the present application provides a micro light emitting diode display panel. The structural schematic diagram of the display panel is as shown in FIG. Figure 8 As shown, it includes: a back plate 100 and a plurality of light emitting diode chips 300;

[0100] Each of the plurality of light-emitting diode dies 300 includes a first semiconductor layer 340 , a light-emitting material layer 330 , a second semiconductor layer 320 , and a first conductive layer 310 , which are stacked;

[0101] The first conductive layer 310 is bonded to the bonding structure 110 on the back plate 100;

[0102] The second semiconductor layer 320 is located on a side of the first conductive layer 310 away from the back plate 100;

[0103] The light emitting material layer 330 is located on a side of the second semiconductor layer 320 away from the first conductive layer 310 ;

[0104] The first semiconductor layer 340 is located on a side of the light emitting material layer 330 away from the second semiconductor layer 320 .

[0105] In this embodiment, the micro-LED crystal 300 adopts a vertical electrode structure, so that the current almost entirely flows vertically through the epitaxial layer of the micro-LED crystal 300, with very little current flowing laterally, which is beneficial to the diffusion of current and the dissipation of heat, and can meet the high-power development trend.

[0106] The LED chip 300 with a vertical electrode structure has all its manufacturing processes performed at the wafer level, and therefore has the following characteristics:

[0107] Compared with horizontal structure, it has high antistatic ability.

[0108] No gold wire is required. On the one hand, the package thickness is thin and can be used to manufacture ultra-thin devices such as backlight sources, large-screen displays, etc.; on the other hand, the yield rate and reliability are improved.

[0109] Aging can be performed before packaging to reduce production costs.

[0110] A through hole with a larger diameter and a metal filling plug, or a plurality of through holes and metal filling plugs, can be used to further improve the heat dissipation efficiency of the substrate, which is particularly suitable for the needs of high-power light-emitting diodes.

[0111] In some possible implementations, such as Fig. 9 As shown, the LED chip 300 not only includes the aforementioned first semiconductor layer 340 , light emitting material layer 330 , second semiconductor layer 320 and first conductive layer 310 , but also includes a second electrode pattern 360 and a top electrode (TCL) layer 350 .

[0112] The top electrode layer 350 is located on a side of the first semiconductor layer 340 away from the light emitting material layer 330 .

[0113] The second electrode pattern 360 is located on a side of the top electrode layer 350 away from the first semiconductor layer 340 .

[0114] The first semiconductor layer 340 includes a recessed area and a non-recessed area, and the surface of the recessed area on one side away from the light-emitting material layer 330 has a curved surface 340a, and the orthographic projection of the curved surface 340a on the plane where the back plate 100 is located does not overlap with the orthographic projection of the second electrode pattern 360 on the plane where the back plate 100 is located; the top electrode layer 350 has an arc-shaped area 350a adapted to the curved surface 340a of the first semiconductor layer 340.

[0115] This embodiment provides a specific vertical electrode structure of the LED chip 300. The arc surface 340a structure on the first semiconductor layer 340 of the LED chip 300 can reduce the current crowding of the vertical electrode structure of the LED chip 300, and can increase the light extraction current efficiency.

[0116] Alternatively, if Fig. 9 As shown, the thickness h1 of the non-recessed area of ​​the first semiconductor layer 340 is 5-10 μm (micrometers), and the minimum thickness h2 of the recessed area of ​​the first semiconductor layer 340 is 2-5 μm, that is, the thickness at the vertex of any arc surface 340a of the first semiconductor layer 340 is 2-5 μm. The curvature of the arc surface 340a is not greater than 0.3.

[0117] Alternatively, the first conductive layer 310 may be an anode, and the second electrode pattern 360 may be a cathode.

[0118] Optionally, both the first conductive layer 310 and the second electrode pattern 360 may be made of ITO (Indium Tin Oxides).

[0119] The inventor of the present application considers that the micro-LED crystal grain 300 needs to undergo mass transfer during the preparation process, and the laser stripping in the mass transfer process will emit a large amount of gas. If the gas is not discharged smoothly, it is easy to cause damage to the LED crystal grain 300. To this end, the present application provides the following possible implementation method for the micro-LED display panel:

[0120] like Figure 8 As shown, the cross-sectional shape of the light emitting diode die 300 in the embodiment of the present application parallel to the back plate 100 is a trapezoid or a circle.

[0121] Figure 8 The solid arrow in the figure indicates the laser scanning direction during laser stripping; Figure 8 The dotted arrow in the figure indicates the exhaust direction.

[0122] During the preparation of the LED crystal grain 300, when the LED crystal grain 300 is laser-stripped from the substrate 200, the direction of the laser scanning is usually parallel to the plane where the substrate 200 is located, and the back plate 100 is usually also parallel to the substrate 200. The trapezoidal or circular cross-section of the LED crystal grain 300 is parallel to the back plate 100, which means that it is parallel to the direction of the laser scanning. The LED crystal grain 300 has a trapezoidal or circular cross-sectional structure, which can form a structure with a gradually increasing cross-sectional area along the direction of the laser scanning, which is beneficial to the gradual increase of the area of ​​the first semiconductor layer 340 ablated by the laser per unit time in the mass transfer process, which can facilitate the rapid separation of a large amount of gas generated by the laser stripping of the first semiconductor layer 340 of the LED crystal grain 300 from the LED crystal grain 300, and can avoid the accumulation of the rapidly generated gas inside the LED crystal grain 300 and cause the LED crystal grain 300 to break, thereby improving the yield rate.

[0123] Optionally, when the cross section of the LED die 300 parallel to the back plate 100 is a trapezoidal cross section, the upper base of the trapezoidal cross section is located upstream in the laser scanning direction of laser stripping, and the lower base of the trapezoidal cross section is located downstream in the laser scanning direction of laser stripping.

[0124] It is understandable that the cross section of the LED die 300 parallel to the back plate 100 may also include other shapes, as long as the size at the upstream end in the laser scanning direction is smaller than the size at the midstream part. For example, the cross section of the LED die 300 parallel to the back plate 100 is triangular or elliptical.

[0125] In some possible implementations, such as Figure 8 As shown, if the cross section of the LED die 300 parallel to the back plate 100 is a trapezoid, the size of the cross section satisfies b>2a, c<b;

[0126] Among them, a is the size of the upper base of the trapezoid, b is the size of the lower base of the trapezoid, and c is the height of the trapezoid.

[0127] In this embodiment, after the cross-section of the LED grain 300 parallel to the backplane 100 meets the above-mentioned size requirements, it can be beneficial for the nitrogen generated after the decomposition of gallium nitride to quickly detach from the LED grain 300 during the laser stripping process, and it can avoid the accumulation of rapidly generated nitrogen inside the LED grain 300 and cause the LED grain 300 to break.

[0128] Optionally, the dimensions of the trapezoidal cross section may be: a<100 μm, b<200 μm, c<200 μm.

[0129] A specific embodiment of a method for preparing a micro light emitting diode display panel is provided below.

[0130] In the first step, the backplane is cleaned by a standard method, and the driving device 120 is made on the backplane. Taking the driving device 120 as a TFT, a metal Mo (molybdenum) layer with a thickness of about 0.2 μm can be deposited on the backplane in sequence, and the gate electrode of the TFT and the first signal line on the same layer can be patterned; a gate dielectric SiO2 (silicon dioxide) with a thickness of 0.15 μm can be formed; an IGZO (indium gallium zinc oxide) layer with a thickness of 40 nm can be formed, and an active pattern can be formed; a metal Mo (molybdenum) layer with a thickness of about 0.2 μm can be deposited, and the source and drain electrodes and the second signal line on the same layer can be patterned; a passivation layer SiO2 with a thickness of about 0.3 μm can be formed; a Ti (titanium) / Al (aluminum) / Ti stacked film layer can be formed, and the pixel electrode and the connecting electrode can be patterned, wherein the pixel electrode is electrically connected to one of the source and drain electrodes, and the connecting electrode is connected to the signal line that transmits a fixed level signal in the first signal line or the second signal line. The pixel electrode and the connecting electrode may be directly used as a binding structure, or other conductive patterns may be made on the surface of the pixel electrode and the connecting electrode as a binding structure to be electrically connected to the electrode of the light emitting diode die 300 .

[0131] In the second step, a substrate such as sapphire is cleaned by a standard method, and a P-GaN (P-type gallium nitride semiconductor) layer is sequentially formed on the sapphire substrate; a Ni (nickel) / Au (gold) layer is formed as an ohmic contact layer, and the thickness of Ni and Au is approximately 0.005 μm and 0.005 μm respectively; a light-emitting material layer is formed, including a multi-quantum well structure; an N-GaN (N-type gallium nitride semiconductor) layer is formed; a Ti / Au layer or a Ti / Al layer is deposited, and the thickness of Ti and Au is approximately 0.01 μm and 0.1 μm respectively, or the thickness of Ti and Al in the electrode is 0.01 μm and 0.1 μm respectively, and an electrode structure is formed through a patterning process. An epitaxial layer (including a stacked structure of a P-type gallium nitride semiconductor, an ohmic contact layer, an N-type gallium nitride semiconductor, a light-emitting material layer and an electrode layer) is obtained on the substrate, and a plurality of light-emitting diode grains 300 arranged in an array are obtained after the epitaxial layer array is divided.

[0132] In the third step, the electrodes of the LED grains 300 corresponding to the positions of the binding structures on the backplane are selected from the plurality of LED grains 300 arranged in an array and are bound together with the binding structures on the backplane through a eutectic reaction, and the P-GaN layer of the LED grains 300 bound to the backplane is laser ablated, thereby peeling the corresponding LED grains 300 from the substrate base material; in addition, by controlling the parameters of the laser ablation process (such as the contents described in the above embodiments of the present invention), the surface of the P-GaN layer of the LED grain 300 away from the backplane 100 includes a curved surface portion, and then the substrate base material with the LED grains not bound to the backplane is completely removed from one side of the backplane.

[0133] In the fourth step, the residual Ga (gallium) metal on the P-GaN layer of the light-emitting diode crystal grain 300 is removed by using air mixed with atomized HCl (hydrogen chloride).

[0134] The fifth step is to form a flat layer, which covers the LED chips 300 on the back plate 100 and fills the gaps between adjacent LED chips 300 , and then performs a patterning process to expose a portion of the surface of the LED chip 300 away from the back plate 100 .

[0135] The sixth step is to make an electrode on the exposed surface of the LED crystal 300 away from the back plate 100. The electrode can be the cathode of the LED crystal 300 or other conductive layer electrically connected to the cathode, and finally a micro LED display panel is obtained.

[0136] By applying the embodiments of the present application, at least the following beneficial effects can be achieved:

[0137] 1. Prepare a plurality of light-emitting diode grains 300 with vertical electrode structures arranged in an array on a substrate 200, and adopt selective stripping to directly transfer the designated light-emitting diode grains 300 to the target backplane 100, that is, adopt a one-time transfer, without using a pasting substrate or a transfer substrate as a transfer, simplifying the transfer process, reducing the number of devices to be transferred, and greatly improving the transfer efficiency and transfer accuracy.

[0138] 2. The prepared epitaxial layer is a vertical electrode structure, and the multiple light-emitting diode grains 300 obtained after dividing the epitaxial layer array are also a vertical electrode structure, which improves the limitation of the prior art that only the light-emitting diode grains 300 with a horizontal electrode structure can be transferred, realizes the transfer of the light-emitting diode grains 300 with a vertical electrode structure, and improves the compatibility of mass transfer.

[0139] 3. The light-emitting diode epitaxial layer is etched in an array manner in a trapezoidal pattern or a circular pattern, so that the cross-sectional shape of the light-emitting diode grain 300 obtained by etching parallel to the substrate base material 200 is a trapezoid or a circle, and a structure with a gradually increasing cross-sectional shape along the laser scanning direction can be formed. When the light-emitting diode grain 300 is subsequently peeled off from one side of the substrate base material 200 by laser peeling, the area of ​​the first semiconductor layer 340 ablated by the laser along the laser scanning direction gradually increases, which can facilitate the rapid separation of a large amount of gas generated by the laser peeling from the first semiconductor layer 340 from the light-emitting diode grain 300, and can avoid the accumulation of the rapidly generated gas inside the light-emitting diode grain 300 and cause the light-emitting diode grain 300 to break.

[0140] 4. The laser ablation of the cambered surface can form a cambered surface 340a structure that is recessed toward the light-emitting material layer 330 on the surface of the first semiconductor layer 340 of the light-emitting diode crystal grain 300 that is away from the light-emitting material layer 330. The required depth of the cambered surface 340a can be obtained by controlling the intensity and irradiation time of the laser. The cambered surface 340a structure on the first semiconductor layer 340 of the light-emitting diode crystal grain 300 can reduce the current crowding existing in the light-emitting diode crystal grain 300 with a vertical electrode structure, and can increase the light extraction current efficiency.

[0141] 5. After the laser stripping of the first semiconductor layer 340 of the LED crystal 300 and the substrate 200 is completed, the second electrode pattern 360 is firstly made on the side of the LED crystal 300 away from the back plate 100, and then the second electrode pattern 360 is used as a mask to perform laser ablation on the side of the first semiconductor layer 340 away from the light-emitting material layer 330 to form a curved surface. In this way, the mask plate used to form the second electrode pattern 360 does not need to be designed according to the surface structure of the first semiconductor layer 340 that has been curved, which can reduce the difficulty of forming the second electrode pattern 360.

[0142] 6. A micro-LED crystal grain 300 with a vertical electrode structure is provided, so that almost all current flows vertically through the epitaxial layer of the micro-LED, with very little current flowing laterally, which is conducive to current diffusion and heat dissipation and can meet the high-power development trend.

[0143] 7. The arc surface 340a structure on the first semiconductor layer 340 of the light-emitting diode chip 300 can reduce the current crowding existing in the light-emitting diode chip 300 with a vertical electrode structure, and can increase the light extraction current efficiency.

[0144] 8. The cross-section of the LED crystal grain 300 parallel to the back plate 100 is trapezoidal or circular, which is beneficial to the gradual increase of the area of ​​the first semiconductor layer 340 ablated by laser per unit time in the mass transfer process, and can facilitate the rapid separation of a large amount of gas generated by laser stripping of the first semiconductor layer 340 of the LED crystal grain 300 from the LED crystal grain 300, thereby avoiding the accumulation of rapidly generated gas inside the LED crystal grain 300 and causing the LED crystal grain 300 to break, thereby improving the yield rate.

[0145] Those skilled in the art will appreciate that the various operations, methods, steps, measures, and schemes in the processes discussed in this application may be alternated, altered, combined, or deleted. Further, other steps, measures, and schemes in the various operations, methods, and processes discussed in this application may also be alternated, altered, rearranged, decomposed, combined, or deleted. Further, the steps, measures, and schemes in the prior art that are similar to those disclosed in this application may also be alternated, altered, rearranged, decomposed, combined, or deleted.

[0146] In the description of the present application, it should be understood that the terms "center", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", etc., indicating orientations or positional relationships, are based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as a limitation on the present application.

[0147] The terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of the features. In the description of this application, unless otherwise specified, "plurality" means two or more.

[0148] In the description of this application, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a direct connection, or an indirect connection through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in this application can be understood according to specific circumstances.

[0149] In the description of this specification, specific features, structures, materials or characteristics may be combined in an appropriate manner in any one or more embodiments or examples.

[0150] It should be understood that, although the steps in the flowchart of the accompanying drawings are displayed in sequence as indicated by the arrows, these steps are not necessarily executed in sequence in the order indicated by the arrows. Unless otherwise specified herein, there is no strict order restriction on the execution of these steps, and they can be executed in other orders. Moreover, at least a part of the steps in the flowchart of the accompanying drawings may include multiple sub-steps or multiple stages, and these sub-steps or stages are not necessarily executed at the same time, but can be executed at different times, and their execution order is not necessarily sequential, but can be executed in turn or alternately with other steps or at least a part of the sub-steps or stages of other steps.

[0151] The above is only a partial implementation method of the present application. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present application. These improvements and modifications should also be regarded as the scope of protection of the present application.

Claims

1. A method for preparing a micro light emitting diode display panel, characterized in that: include: An epitaxial layer is prepared on one side of a substrate, wherein the epitaxial layer includes a first semiconductor layer, a light emitting material layer, a second semiconductor layer and a first conductive layer, wherein the first semiconductor layer is in direct contact with the substrate, and the first conductive layer is the film layer farthest from the substrate in the epitaxial layer; Dividing the epitaxial layer into a plurality of light emitting diode grains arranged in an array; providing a back plate, and making a binding structure on the back plate; Binding the first conductive layers of at least some of the light emitting diode dies among the plurality of light emitting diode dies to the binding structure; peeling the light-emitting diode die bound to the binding structure from the substrate base material; The step of dividing the epitaxial layer into a plurality of light emitting diode grains arranged in an array comprises: Performing array etching on the first semiconductor layer, the light emitting material layer, the second semiconductor layer and the first conductive layer to obtain the plurality of light emitting diode grains arranged in an array; The cross-sectional shape of any one of the plurality of LED grains is a trapezoid, the cross-sectional shape is parallel to the substrate base material, the upper base of the trapezoidal cross-sectional shape is located upstream of the laser scanning direction of laser stripping, and the lower base of the trapezoidal cross-sectional shape is located downstream of the laser scanning direction of laser stripping.

2. The preparation method according to claim 1, characterized in that: The step of peeling the light emitting diode die bound to the binding structure from the substrate base material comprises: Laser ablation is performed on the first semiconductor layer of the light-emitting diode crystal grain bound to the binding structure to separate the first semiconductor layer of the light-emitting diode crystal grain from the substrate base material.

3. The preparation method according to claim 2, characterized in that: The laser ablation of the first semiconductor layer of the light-emitting diode crystal grain bound to the binding structure includes: performing arc-shaped laser ablation on a side surface of the first semiconductor layer of the light-emitting diode crystal grain away from the back plate.

4. The preparation method according to claim 3, characterized in that: After the light emitting diode die bound to the binding structure is peeled off from the substrate, the method further includes: Making a top electrode layer on a side of the first semiconductor layer of the light-emitting diode crystal grain away from the back plate; A second electrode pattern is formed on a side of the top electrode layer away from the back plate.

5. The preparation method according to claim 1, characterized in that: After the light emitting diode die bound to the binding structure is peeled off from the one side of the substrate, the method further includes: Making a second electrode pattern on a side of the light emitting diode die away from the back plate; Using the second electrode pattern as a mask, laser ablation is performed on a surface of the first semiconductor layer of the light-emitting diode crystal grain that is away from the light-emitting material layer to form a curved surface.

6. The preparation method according to any one of claims 2 to 5, characterized in that: The laser ablation satisfies at least one of the following conditions: The laser irradiation frequency of the laser ablation is 0.1 Hz-1 kHz; The laser ablation environment atmosphere includes air with a humidity lower than 5%; The laser ablation environment atmosphere includes atomized hydrogen chloride with a concentration greater than 0.1 molar; The laser ablation is cooled by nitrogen gas with a temperature below 25°C.

7. A micro light emitting diode display panel, characterized in that: Prepared by the preparation method according to any one of claims 1 to 6, the display panel comprises: a backplane (100) and a plurality of light-emitting diode grains (300); Each of the plurality of light-emitting diode crystals (300) comprises a first semiconductor layer (340), a light-emitting material layer (330), a second semiconductor layer (320) and a first conductive layer (310) which are stacked; The first conductive layer (310) is bound to the binding structure (110) on the back plate (100); The second semiconductor layer (320) is located on a side of the first conductive layer (310) away from the back plate (100); The light emitting material layer (330) is located on a side of the second semiconductor layer (320) away from the first conductive layer (310); The first semiconductor layer (340) is located on a side of the light emitting material layer (330) away from the second semiconductor layer (320).

8. The display panel according to claim 7, characterized in that: The light-emitting diode crystal grain (300) further comprises a second electrode pattern (360) and a top electrode layer (350); The top electrode layer (350) is located on a side of the first semiconductor layer (340) away from the light-emitting material layer (330); The second electrode pattern (360) is located on a side of the top electrode layer (350) away from the first semiconductor layer (340); The first semiconductor layer (340) comprises a recessed area and a non-recessed area, and a surface of the recessed area on one side away from the light-emitting material layer (330) has a curved surface, and the orthographic projection of the curved surface (340a) on the plane where the back plate is located does not overlap with the orthographic projection of the second electrode pattern (360) on the plane where the back plate is located; the top electrode layer (350) has an arc-shaped area (350a) adapted to the curved surface (340a) of the first semiconductor layer (340).

9. The display panel according to claim 8, characterized in that: The thickness of the non-depressed area of ​​the first semiconductor layer (340) is 5-10 μm, the minimum thickness of the depressed area of ​​the first semiconductor layer (340) is 2-5 μm, and the curvature of the arc surface (340a) is not greater than 0.

3.

10. The display panel according to any one of claims 7 to 9, characterized in that: The cross-sectional shape of the light-emitting diode crystal grain parallel to the back plate (100) is a trapezoid.

11. The display panel according to claim 10, characterized in that: If the cross section of the light emitting diode die (300) parallel to the back plate (100) is a trapezoid, the size of the cross section satisfies b>2a, c<b; Among them, a is the upper base size of the cross-section, b is the lower base size of the cross-section, and c is the height of the cross-section.

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