Micro light emitting element, micro light emitting array, transfer method and display thereof

Abstract

A micro light emitting element, a micro light emitting array, a transfer method and a display thereof, the micro light emitting element has a side surface, an oppositely arranged bottom surface and a top surface, the top surface is a light emitting surface; the micro light emitting element comprises a substrate arranged under the bottom surface and a transfer adhesive film covering the top surface, the transfer adhesive film does not exceed the edge of the top surface, and the adhesive is adhered to the top surface during the laser removal of the transfer adhesive film or the transfer process, so as to avoid falling on the substrate and avoid producing dirty substrate.

Description

Technical Field

[0001] This invention relates to a structure for a light-emitting element, and more particularly to a micro light-emitting diode structure. Background Technology

[0002] Currently, the mainstream approach for mass transfer is the Pick-Place pattern selection scheme, which corresponds to a weakened structure with bridge arms in MicroLEDs. This structure is difficult to control in terms of yield and has high cost. Summary of the Invention

[0003] To address the problems mentioned in the background art, reduce the difficulty of yield control, and lower production costs, this invention provides a micro-light-emitting element. For clarity of the product structure, the micro-light-emitting element is defined as including a bottom surface, a top surface, and a side surface. The micro-light-emitting element includes: a semiconductor layer sequence, a first electrical connection layer, and a second electrical connection layer; it has a side surface, a bottom surface, and a top surface disposed opposite each other; at least the top surface is a light-emitting surface, which is the main light-emitting surface of the micro-light-emitting element; light emission is not limited to the side surface and the bottom surface. It also includes a substrate disposed under the bottom surface and a transfer adhesive film covering the top surface. The top surface includes a first region and a second region. The transfer adhesive film is located only in the first region, the first region is located in the second region, and the second region is located at the periphery of the top surface. Structurally, the top surface has a stepped surface composed of the transfer adhesive film, and the distance between the transfer adhesive film and the edge of the top surface is 0.2 μm to 2 μm, or 2 μm to 10 μm.

[0004] According to the present invention, preferably, the top surface and the transfer adhesive film are rectangular, the top surface includes a first long side and a first short side, the transfer adhesive film includes a second long side and a second short side, the length of the first long side is compared with the length of the first short side to form a first ratio, and the length of the second long side is compared with the length of the second short side to form a second ratio, wherein the first ratio is 0.9 to 1.1 times the second ratio.

[0005] According to the present invention, preferably, the top surface of the micro light-emitting diode includes a regular or irregular roughened surface, where regularity generally refers to the patterning of the process.

[0006] According to the present invention, preferably, the transfer adhesive film is a continuous film or a discontinuous film. As an example, a discontinuous film may be two or more separate patterns.

[0007] According to the present invention, preferably, when the transfer adhesive film is a discontinuous film, the spacing between the transfer adhesive films is 1 μm to 5 μm.

[0008] According to the present invention, preferably, the transfer adhesive film is a particulate film, and the particulate film with matching properties can serve as a photoextraction structure when it is transparent.

[0009] According to the present invention, preferably, the thickness of the transfer adhesive film is 0.1 μm to 2 μm, or not greater than 0.1 μm. Here, the thickness mainly refers to the distance from the highest point of the core to the far end face of the transfer adhesive film, excluding the thickness of the transfer adhesive film in the semiconductor layer sequence pattern or holes. This balances transfer reliability and light transmittance. For some smaller core sizes, if reliability is prioritized, the thickness of the transfer adhesive film is preferably 0.1 μm to 2 μm. For some applications that require high brightness, it is preferably not greater than 0.1 μm.

[0010] According to the present invention, preferably, in order to match the ultraviolet laser decomposition of the transfer adhesive film and ensure the transmittance of visible light, the transfer adhesive film transmits light with a wavelength of 400nm to 750nm, wherein the transmittance is not less than 90%; and at least partially absorbs light with a wavelength of less than 360nm, wherein the absorption rate is not less than 90%, and the transfer adhesive film absorbs ultraviolet laser decomposition.

[0011] According to the present invention, preferably, the material of the transfer adhesive film includes polyimide or acrylic adhesive.

[0012] According to the present invention, preferably, the edge of the transfer adhesive film is inclined, wherein the inclination angle is 40° to 75°, thereby changing the path of light emission.

[0013] According to the present invention, preferably, the side length of any side of the transfer adhesive film in contact with the top surface is not less than 10 μm.

[0014] According to the present invention, preferably, the surface of the transfer adhesive film away from the semiconductor layer sequence has grooves, such as a periodically distributed array of grooves. The periodic grooves are the process structure after the step-by-step laser decomposition of the transfer adhesive film. The spacing between the grooves is no more than 7 μm. If the spacing is too large, it is not conducive to the transfer of core particles after the laser decomposition of the transfer adhesive film, and core particle rotation and displacement are likely to occur. In some embodiments, it is not limited to a periodic distribution. More importantly, the spacing between the grooves is important.

[0015] In some embodiments of the present invention, core transfer can be achieved by using a large spot laser on a transfer adhesive film through a few grooves, such as a single groove on a single core transfer adhesive film.

[0016] According to the present invention, preferably, the depth of the groove is 0.1 μm to 1 μm.

[0017] According to the present invention, preferably, the groove occupies 50% to 80% of the surface area of ​​the transfer adhesive film away from the semiconductor layer sequence, which is a sufficiently large proportion to ensure sufficient separation between the transfer adhesive film and the temporary substrate.

[0018] According to the present invention, preferably, the minimum side length of the micro-light-emitting diode is 50 μm to 100 μm, or less than 50 μm.

[0019] According to the present invention, preferably, the first electrical connection layer and / or the second electrical connection layer are located on the bottom surface, and the micro-light-emitting element is, for example, a flip-chip or a vertical chip, and in some embodiments, it may also be a regular chip.

[0020] According to the present invention, preferably, the substrate is a circuit board, and the bottom surface of the micro light-emitting diode is fixed on the circuit board.

[0021] According to the present invention, preferably, the semiconductor layer sequence thickness is 2.5 μm to 6 μm. In the field of micro-light-emitting element transfer, the epitaxial layer thickness is usually thinner than conventional-sized core particles, making it more susceptible to damage from external forces. Therefore, the product structure is designed to match this in the present invention.

[0022] In this invention, a micro-light-emitting array is also disclosed, including a plurality of micro-light-emitting diodes. Each micro-light-emitting diode includes a bottom surface, a top surface, and a side surface. The array also includes a substrate disposed under the bottom surface and a transfer adhesive film covering the top surface. The surface of the transfer adhesive film away from the semiconductor layer sequence has periodic grooves. The distance from the transfer adhesive film to the edge of the top surface is 0.2 μm to 2 μm, or 2 μm to 10 μm.

[0023] According to the present invention, preferably, the transfer adhesive film has a roughened surface on the side near the semiconductor layer sequence.

[0024] According to the present invention, preferably, the thickness of the transfer adhesive film is 0.1 μm to 2 μm, or not greater than 0.1 μm. If the thickness of the transfer adhesive film is too large, it will lead to increased peel stress, which, combined with the epitaxial design of the micro light-emitting diode, will easily cause the core to break. Therefore, the present invention proposes to reduce the thickness of the transfer adhesive film. Preferably, the thickness of the transfer adhesive film is 1.5 μm. In practical applications, if the thickness is too thin, the ability to absorb laser during the transfer process will be weakened, which will easily cause laser damage to the epitaxial material.

[0025] According to the present invention, preferably, the transfer adhesive film transmits light with a wavelength of 400 nm to 750 nm and at least partially absorbs light with a wavelength of less than 360 nm.

[0026] According to the present invention, preferably, the plurality of micro light-emitting diodes have multiple wavelengths, for example, they may include micro light-emitting diodes with RGB (red, green, and blue) colors.

[0027] According to the present invention, preferably, the edge of the transfer adhesive film is inclined, wherein the inclination angle is 40° to 75°.

[0028] According to the present invention, preferably, the side length of the side of the transfer adhesive film in contact with the top surface is not less than 10 μm.

[0029] According to the present invention, preferably, the surface of the transfer adhesive film away from the semiconductor layer sequence has periodic grooves, and the spacing between the grooves is no greater than 7 μm.

[0030] According to the present invention, preferably, the material of the transfer adhesive film includes polyimide or acrylic adhesive.

[0031] According to the present invention, preferably, the minimum side length of the micro-light-emitting diode is 50 μm to 100 μm, or less than 50 μm.

[0032] According to the present invention, preferably, the first electrical connection layer and / or the second electrical connection layer are located on the bottom surface.

[0033] According to the present invention, preferably, the substrate is a circuit board, and the bottom surface of the micro light-emitting diode is fixed on the circuit board.

[0034] According to the present invention, preferably, the thickness of the semiconductor layer sequence is 2.5 μm to 6 μm.

[0035] This invention discloses a wafer carrier method, such as a wafer transfer method, and discloses a micro-light-emitting array comprising a plurality of micro-light-emitting diodes, wherein the micro-light-emitting diodes include:

[0036] A semiconductor layer sequence, comprising a first semiconductor layer, a second semiconductor layer, and an active layer located between the two;

[0037] The first electrical connection layer is electrically connected to the first semiconductor layer;

[0038] The second electrical connection layer is electrically connected to the second semiconductor layer;

[0039] The component has a side surface, a bottom surface, and a top surface that are arranged opposite each other;

[0040] It also includes a substrate and a transfer adhesive film covering a portion of the top surface. The transfer adhesive film is located between the substrate and the top surface. The top surface includes a first region and a second region. The transfer adhesive film is located within the first region, and the second region surrounds the first region. The substrate material has a transmittance of not less than 95% for light with wavelengths below 360 nm, and the substrate material includes sapphire.

[0041] According to the present invention, preferably, the distance from the transfer adhesive film to the top edge is 0.2 μm to 2 μm, or 2 μm to 10 μm.

[0042] According to the present invention, preferably, the top surface and the transfer adhesive film are rectangular, the top surface includes a first long side and a first short side, the transfer adhesive film includes a second long side and a second short side, the length of the first long side is compared with the length of the first short side to form a first ratio, and the length of the second long side is compared with the length of the second short side to form a second ratio, wherein the first ratio is 0.9 to 1.1 times the second ratio.

[0043] According to the present invention, preferably, the transmittance of the transfer adhesive film for light with wavelengths from 400 nm to 750 nm is not less than 90%; and the absorption rate of the transfer adhesive film for light with wavelengths below 360 nm is not less than 90%, and the transfer adhesive film absorbs ultraviolet laser decomposition.

[0044] According to the present invention, preferably, the material of the transfer adhesive film includes polyimide or acrylic adhesive.

[0045] According to the present invention, preferably, the thickness of the semiconductor layer sequence is 2.5 μm to 6 μm.

[0046] This invention also provides a method for transferring a micro-light-emitting array, which can fabricate the aforementioned micro-light-emitting element and micro-light-emitting array, specifically including the following steps:

[0047] Step (1): Provide a growth substrate and fabricate a semiconductor layer sequence on the growth substrate. The semiconductor layer sequence includes a first semiconductor layer, a second semiconductor layer and an active layer located between the two.

[0048] Step (2): Fabricate a separate semiconductor layer sequence structure, which includes a first mesa and a second mesa, and fabricate a first electrical connection layer and a second electrical connection layer on the first mesa and the second mesa, respectively.

[0049] Step (3): Fix the side of the semiconductor layer sequence away from the growth substrate onto the first transfer substrate, and then remove the growth substrate;

[0050] Step (4): A transfer adhesive film is formed on the side surface of the semiconductor layer sequence away from the first transfer substrate. Part of the transfer adhesive film is removed. The side surface includes a first region and a second region. The transfer adhesive film covers the first region and the second region surrounds the first region. The transfer adhesive film does not exceed the edge of the surface. The distance from the transfer adhesive film to the edge is 0.2 μm to 2 μm, or 2 μm to 10 μm. The thickness of the transfer adhesive film is not greater than 2 μm. The transfer adhesive film is fixed on the second transfer substrate. Then, a portion of the transfer adhesive film is removed using a laser. The first transfer substrate is peeled off to expose the first electrical connection layer and / or the second electrical connection layer.

[0051] According to the present invention, preferably, the method further includes step (5), completely removing the transfer adhesive film.

[0052] This invention discloses a display fabricated using the aforementioned micro-light-emitting array transfer method.

[0053] The present invention discloses a display having a micro-light-emitting array, including a plurality of micro-light-emitting diodes, each micro-light-emitting diode having a bottom surface, a top surface, and a side surface, and further including a circuit board disposed under the bottom surface and a transfer adhesive film covering the top surface, wherein the distance from the transfer adhesive film to the edge of the top surface is 0.2 μm to 2 μm, or 2 μm to 10 μm.

[0054] According to the present invention, preferably, the surface of the transfer adhesive film away from the semiconductor layer sequence has periodic grooves, and the spacing between the grooves is no greater than 7 μm.

[0055] According to the present invention, preferably, the minimum side length of the micro-light-emitting diode is 50 μm to 100 μm, or less than 50 μm.

[0056] According to the present invention, preferably, the first electrical connection layer and / or the second electrical connection layer are located on the bottom surface.

[0057] According to the present invention, preferably, the thickness of the semiconductor layer sequence is 2.5 μm to 6 μm.

[0058] The beneficial effects of the present invention include: providing a micro-light-emitting diode chip structure with high transfer yield; other beneficial effects of the present invention will be described in conjunction with specific embodiments. Attached Figure Description

[0059] The accompanying drawings are provided to further illustrate the invention and form part of the specification. They are used in conjunction with the embodiments of the invention to explain the invention, but do not constitute a limitation thereof. Furthermore, the figures are descriptive outlines and are not drawn to scale.

[0060] Figure 1 This is a schematic cross-sectional view of a micro-luminescent array in the prior art;

[0061] Figure 2 and Figure 3 This is a schematic cross-sectional view of the epitaxial film grown in Example 1;

[0062] Figure 4 This is a cross-sectional schematic diagram of the chip structure fabricated in Example 1;

[0063] Figures 5 to 9 This is a cross-sectional schematic diagram of the first core transfer process in Example 1;

[0064] Figures 10 to 13 This is a cross-sectional schematic diagram of the second core transfer process in Example 1;

[0065] Figure 14 This is a cross-sectional schematic diagram of the third core transfer process in Example 1;

[0066] Figure 15 and Figure 16These are cross-sectional and top views of the micro-light-emitting element in Example 2;

[0067] Figure 17 , Figure 18 and Figure 19 This is a cross-sectional schematic diagram of the micro-light-emitting element in some embodiments of Example 2;

[0068] Figure 20 This is a cross-sectional schematic diagram of the micro-light-emitting element in Example 3;

[0069] Figure 21 This is a cross-sectional schematic diagram of the micro-light-emitting element in Example 4;

[0070] Figure 22 and Figure 23 This is a cross-sectional schematic diagram of the micro-luminescent array in Example 5;

[0071] Figure 24 This is a cross-sectional schematic diagram of the micro-light-emitting element in Example 6;

[0072] Figure 25 and Figure 26 This is a top view and a cross-sectional view of the display in Example 7.

[0073] In the diagram, the following labels are used: 111, first semiconductor layer; 111a, first region; 111b, second region; 111', first mesa; 112, second semiconductor layer; 112', second mesa; 121, first electrical connection layer; 122, second electrical connection layer; 210, transfer adhesive film; 220, adhesive layer; 310, wafer; 320, growth substrate; 330, first transfer substrate; 340, second transfer substrate; 350, carrier plate; 360, circuit board; 361, first conductive layer; 362, second conductive layer; Circle: laser focusing position; T: thickness of transfer adhesive film; a1, a2, b1, b2: length of corresponding side; α: tilt angle. Detailed Implementation

[0074] The following specific examples illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and various details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention.

[0075] It should be noted that the illustrations provided in this embodiment are only schematic representations of the basic concept of the present invention. Although the illustrations only show components related to the present invention and are not drawn according to the actual number, shape and size of the components, the actual implementation may involve changes in the form, quantity and proportion of each component, and the layout of the components may be more complex.

[0076] See Figure 1 A prior art micro-light-emitting array includes a plurality of micro-light-emitting diodes. The micro-light-emitting diodes of the present invention mainly refer to light-emitting diodes with a minimum side length of 50μm to 100μm, or less than 50μm.

[0077] A micro light-emitting diode includes a sequence of semiconductor layers, comprising a first semiconductor layer 111, a second semiconductor layer 112, and an active layer 113 located between the two. A first electrical connection layer 121 and a second electrical connection layer 122 are electrically connected to the first semiconductor layer 111 and the second semiconductor layer 112, respectively. The micro light-emitting diode has a side surface, a bottom surface and a top surface disposed opposite to each other, wherein the top surface is the light-emitting surface. The first electrical connection layer 121 and / or the second electrical connection layer 122 are metal conductive layers, non-metal conductive layers, or a combination of both.

[0078] A transfer adhesive film 210 is placed on the top surface of the micro-LED (the top surface mainly refers to the light-emitting surface of the product). The transfer adhesive film 210 is located on the wafer 310 and usually serves to fix the core in the prior art. Since the transfer adhesive film 210 is usually a continuous film layer, it is difficult to selectively transfer. In selective transfer, laser separation of the epitaxial material layer of the micro-LED is often used. For example, laser separation of the first semiconductor layer 111. Taking the first semiconductor layer 111 as gallium nitride-based as an example, laser decomposition of gallium nitride material can easily generate a lot of gas in a short time, requiring a large laser energy. This problem is not obvious in the transfer process of conventionally sized cores. The black circle in the figure shows the laser decomposition point. However, the epitaxial thickness of micron-sized cores is usually 2.5μm to 6μm. During the transfer process, on the one hand, gas compression of the core can easily cause core displacement and other problems, resulting in poor core transfer. On the other hand, the energy is large, and there is no effective support under the transfer of small cores, which can easily damage the epitaxial layer.

[0079] In the first embodiment of the present invention, based on the technical difficulties existing in the prior art, the present invention provides a method for transferring micro-luminescent arrays.

[0080] A method for transferring a micro-luminescent array includes the following steps:

[0081] (1) See Figure 2 and Figure 3A growth substrate 320 is provided. The growth substrate 320 is a common material such as sapphire, gallium arsenide or silicon. Depending on the surface morphology of the substrate, the growth substrate 320 can be a flat wafer or a patterned substrate. A semiconductor layer sequence is fabricated on the growth substrate 320 by chemical vapor deposition. The semiconductor layer sequence includes, from the growth substrate 320 upwards, a first semiconductor layer 111, a second semiconductor layer 112 and an active layer 113 located between the two.

[0082] (2) See Figure 4 A series of separate semiconductor layer sequences are fabricated, with isolation trenches extending to the growth substrate between individual semiconductor layer sequences. The separate semiconductor layer sequence structure includes a first mesa 111' and a second mesa 112'. Specifically, the first mesa 111' can be a P-type surface, and the second mesa 112' can be an N-type surface. A first electrical connection layer 121 and a second electrical connection layer 122 are fabricated on the first mesa 111' and the second mesa 112', respectively. In this embodiment, the first mesa 111' and the second mesa 112' are fabricated first, and then the isolation trenches between the semiconductor layer sequence structures are fabricated. In some embodiments, the order can be adjusted.

[0083] (3) See Figures 5 to 7 The semiconductor layer sequence is fixed on the side away from the growth substrate 320 on the first transfer substrate 330. The first transfer substrate 330 has an adhesive layer 220, which is bonded to the semiconductor layer sequence. The growth substrate 320 is then removed. In this embodiment, the fixing method is achieved by bonding with adhesive material.

[0084] See Figure 8 After removing the growth substrate 320, the adhesive material between the core particles is removed, thus achieving individual independence of the adhesive material.

[0085] See Figure 9 In some embodiments of this example, taking the flat growth substrate 320 as an example, the exposed side of the semiconductor layer sequence after removing the growth substrate 320 can be roughened. In this embodiment, the exposed side is the first semiconductor layer 111, and the roughening method includes wet etching or dry etching.

[0086] (4) See Figures 10 to 12A transfer adhesive film 210 is fabricated on the surface of the semiconductor layer sequence away from the first transfer substrate 330. For example, in this embodiment, the first semiconductor layer 111 is imprinted into the transfer adhesive film 210 fixed to the second transfer substrate 340. The micro-light-emitting diode is fixed to the second transfer substrate 340 through the transfer adhesive film 210. Subsequently, the first transfer substrate 330 is removed, realizing the transfer of the micro-light-emitting diode from the first transfer substrate 330 to the second transfer substrate 340, with the electrode surface of the micro-light-emitting diode facing upwards. The material of the transfer adhesive film 210 includes polyimide or acrylic adhesive. Ultraviolet laser light passes through the sapphire material, and the material of these transfer adhesive films 210 can be decomposed at low energy, protecting the epitaxial layer from laser damage.

[0087] See Figure 13 The transfer adhesive film 210 in a certain area is removed. This removal can be done by etching, including dry etching or wet etching. In this embodiment, directional dry etching is used. After the removal process, the coverage area of ​​the transfer adhesive film 210 does not exceed the edge of the surface. The transfer adhesive film has a stepped surface. The transfer adhesive film covers the first area of ​​the surface, while the transfer adhesive film is removed from the outer second area. The distance from the transfer adhesive film 210 to the edge is 0.2μm to 2μm, or 2μm to 10μm. That is, there is a groove at the edge of the transfer adhesive film 210 on the top surface of the micro-light-emitting element, which realizes the separation between individual transfer adhesive films 210 and also confines the individual transfer adhesive films 210 within the surface of the first semiconductor layer 111. The thickness T of the transfer adhesive film 210 is not greater than 2μm, preferably 1.5μm in this embodiment. During the transfer process, even a very thin transfer adhesive is not easy to fall off due to vibration. One side of the transfer adhesive film 210 is completely bonded to the first semiconductor layer 111, providing adhesion guarantee. After a removal process, the first electrical connection layer 121 and / or the second electrical connection layer 122 are exposed. The chip structure shown in the figure constitutes a micro-light-emitting array fixed on the wafer for transport and transfer, so that downstream users can continue to use it for laser pickup.

[0088] In this embodiment, for the sake of simplicity, the top surface is the first semiconductor layer 111. In some embodiments, the top surface may also include other materials, such as a transparent insulating layer or an insulating reflective layer.

[0089] In some embodiments of this example, a micro-light-emitting array composed of multiple micro-light-emitting diodes is bonded to a circuit board.

[0090] See Figure 14In some embodiments of this example, step (5) is also included: laser decomposition of the transfer adhesive film 210, forming a groove on the side of the transfer adhesive film 210 close to the second transfer substrate 340. The circle in the figure represents the area where the laser acts. This area is located at the interface between the transfer adhesive film 210 and the second transfer substrate 340. The transfer adhesive film 210, together with the micro light-emitting diode, is separated from the second transfer substrate 340.

[0091] In this step, the wavelength of the laser is preferably in the ultraviolet band, which is not visible light. The transfer adhesive film 210 is preferably excited by the chip with a wavelength of 400nm to 750nm. Here, transmission means that the transmittance is not less than 90%. The material of the transfer adhesive film 210 is, for example, the polyimide or acrylic adhesive mentioned in the above steps, to avoid the reduction of light extraction efficiency due to the light absorption of the transfer adhesive film during application. At least some of the light with wavelengths below 360nm is absorbed. Here, absorption means that the absorption rate is not less than 90%. In the ultraviolet band, it can be fully decomposed by the laser to avoid the laser damaging the semiconductor layer sequence.

[0092] In some embodiments, after the transfer adhesive film 210, which is fixed on, for example, a circuit board or other carrier, is separated from the second transfer substrate 340 along with the micro light-emitting diode, the transfer adhesive film 210 on the surface of the micro light-emitting diode is then completely removed.

[0093] In some implementations, the transfer method of this embodiment is used to fabricate the display chip in the display.

[0094] In a second embodiment of the present invention, in order to improve the transfer efficiency or brightness of the micro-light-emitting diode, a micro-light-emitting diode is provided, wherein the minimum side length of the micro-light-emitting diode is 50μm to 100μm, or less than 50μm, and preferably less than 50μm in this embodiment.

[0095] See Figure 15 and Figure 16 A micro light-emitting diode includes a semiconductor layer sequence, a first electrical connection layer 121 and a second electrical connection layer 122. The semiconductor layer sequence includes a first semiconductor layer 111, a second semiconductor layer 112 and an active layer 113 located between the two. The micro light-emitting diode has a side surface, a bottom surface and a top surface disposed opposite each other, at least the top surface is the light-emitting surface. In some embodiments, the bottom surface of the micro light-emitting diode is fixed on a circuit board.

[0096] From a top view, the transfer adhesive film 210 is disposed within the first region 111a on the top surface of the micro-LED. The top surface also includes a second region 111b. The first region 111a is located within the second region 111b, and the second region 111b is located at the edge of the top surface. The top surface of the micro-LED has steps formed by the transfer adhesive film 210 and protrusions formed by the transfer adhesive film 210. The transfer adhesive film 210 does not extend beyond the edge of the top surface. It should be noted that "not extending beyond the edge of the top surface" means that in the top view of the product in the vertical direction, the projection of the transfer adhesive film 210 is located within the top surface mainly composed of the first semiconductor layer 111. Specifically, the distance D1 from the transfer adhesive film 210 to the edge of the top surface is 0.2μm to 2μm, or 2μm to 10μm. In this embodiment, D1 is preferably 1μm, but it can also be 3μm or 5μm to ensure that the transfer adhesive film 210 is connected to the top surface and that no chips fall off during the transfer process.

[0097] In the design of this invention, if the transfer adhesive film 210 extends beyond the top edge, debris is easily generated during the laser decomposition of the transfer adhesive film 210, causing pollution and performance degradation.

[0098] In the implementation of this invention, it was found that the distance D1 is related to the shape of the chip. For example, in the long side direction, D1 is usually larger than in the short side direction. It can also be described as the shape of the transfer adhesive film 210 being proportionally reduced in length-to-width ratio during dry etching, reducing chip rotational offset caused by different etching actions and lowering transfer yield. As shown in the figure, the ratio of the length a1 of the long side and the length b1 of the short side of the top surface is approximately close to the ratio of the length a2 of the long side and the length b2 of the short side of the transfer adhesive film. Preferably, a1 / b1 = (0.9~1.1) * a2 / b2.

[0099] Furthermore, to address the stress and light absorption issues of the transfer adhesive film layer 210, the thickness of the transfer adhesive film 210 is set to be no greater than 2 μm, preferably less than 0.5 μm. In some embodiments, the thickness of the transfer adhesive film 210 is no greater than 0.1 μm to minimize the impact of light absorption by the adhesive material. The material of the transfer adhesive film 210 includes polyimide or acrylic adhesive.

[0100] In some embodiments, in order to minimize the area of ​​the transfer adhesive film 210 while ensuring the adhesion between the transfer adhesive film 210 and the micro light-emitting diode, for example when the transfer adhesive film 210 occupies less than 80% of the surface area of ​​the first semiconductor layer 111, or which can be described as the area of ​​the transfer adhesive film 210 in contact with the surface of the first semiconductor layer 111 accounting for less than 80% of the total projected area of ​​the micro light-emitting diode, it is preferable to form an irregular roughened structure or a regular patterned roughened structure on the surface of the first semiconductor layer 111 facing the transfer adhesive film 210.

[0101] In this embodiment, the transfer adhesive film 210 has periodic grooves 211 on the side away from the top surface. These grooves 211 are located on the surface of the transfer adhesive film 210 and are generated by laser decomposition of the adhesive material to achieve core transfer. The spacing between the grooves 211 is no greater than 7 μm. If the spacing between the grooves 211 is too large, it will be difficult to achieve core transfer and separation, and the adhesive material may be pulled and shifted. The depth of the grooves 211 is 0.1 μm to 1 μm. Too shallow a groove depth is not conducive to peeling, while too deep a groove depth corresponds to excessive laser energy, which may damage the chip epitaxy. The grooves 211 occupy 50% to 80% of the surface area of ​​the transfer adhesive film 210 away from the semiconductor layer sequence.

[0102] See Figure 17 In some embodiments, in order to release internal stress in the film layer and improve product reliability, the transfer adhesive film 210 is a patterned discontinuous film with intervals, such as intervals of 1 μm to 5 μm, and some transfer structures or optical structures can also be formed in the intervals.

[0103] See Figure 18 and Figure 19 The transfer adhesive film 210 is a discretely distributed particle film. For example, the transfer adhesive film 210 can be partially removed by etching to form a discretely distributed adhesive material. The refractive index of the adhesive material is preferably 1 to 2.5, which has a certain light extraction effect. In some embodiments, it is combined with a patterned first semiconductor layer 111, with the particles located in the patterned holes in the semiconductor layer sequence. The boundary of the adhesive material is the boundary between the first region 111a and the second region 112b.

[0104] See Figure 20 In the third embodiment of the present invention, a micro-light-emitting element suitable for use in mobile phone or watch displays is provided. Since these application fields emphasize normal light intensity and privacy and reduce side light emission, the difference between this embodiment and embodiment 2 is that the edge of the transfer adhesive film 210 is inclined, wherein the inclination angle α is 40°~80°, preferably 45°~75°.

[0105] See Figure 21 In a fourth embodiment of the present invention, as an optional solution, this embodiment provides a micro-light-emitting element, wherein a transfer adhesive film is covered on the top surface of the micro-light-emitting element, and the area of ​​the side of the transfer adhesive film in contact with the semiconductor layer sequence is larger than the area of ​​the side away from the semiconductor layer sequence. The trapezoidal shape of the transfer adhesive film reduces the possibility of chipping.

[0106] See Figure 22 and Figure 23In a fifth embodiment of the present invention, a micro-light-emitting array is provided, comprising a plurality of micro-light-emitting diodes (LEDs) located on a support. The plurality of LEDs can emit light of the same color, light of different wavelengths, or light of different colors. For example, the plurality of LEDs can be composed of red, green, and blue LEDs. Each LED includes a bottom surface, a top surface, and a side surface, wherein the bottom surface is an electrical connection surface, the top surface is a light-emitting surface, and a transfer adhesive film 210 is independent of each other between the LEDs. The transfer adhesive film 210 is located on the top surface of the LEDs and does not extend beyond the edge of the top surface. The distance from the transfer adhesive film 210 to the edge of the top surface is 0.2 μm to 2 μm, or 2 μm to 10 μm. When the transfer adhesive film 210 extends beyond the edge of the top surface, debris is easily generated during the laser decomposition of the transfer adhesive film 210. This debris easily falls onto the support, causing contamination and performance degradation. The support includes an adhesion layer 230 and a carrier plate 350. The adhesive layer 230 can be an insulating adhesive film; the adhesive layer 230 can also be a bonding metal such as solder paste, and the carrier board 350 can be a circuit board for bonding connections.

[0107] The transfer adhesive film 210 is transparent to light with wavelengths from 400 nm to 750 nm. To achieve laser lift-off and absorb the laser, the transfer adhesive film 210 at least partially absorbs light with wavelengths below 360 nm. The material of the transfer adhesive film is preferably polyimide or acrylic adhesive. Furthermore, to address the stress and light absorption issues of the transfer adhesive film 210, the thickness of the transfer adhesive film 210 is set to be no greater than 2 μm, for example, 1.5 μm. In some embodiments, the thickness of the transfer adhesive film 210 is no greater than 0.1 μm to minimize the impact of light absorption by the transfer adhesive film 210.

[0108] To minimize the area of ​​the transfer adhesive film 210 while ensuring adhesion between the transfer adhesive film 210 and the micro-LED, for example, when the transfer adhesive film 210 occupies less than 80% of the surface area of ​​the first semiconductor layer 111, or as can be described as the area of ​​the transfer adhesive film 210 in contact with the surface of the first semiconductor layer 111 being less than 80% of the total projected area of ​​the micro-LED, it is preferable to create an irregular roughened structure or a regular patterned roughened structure on the surface of the first semiconductor layer 111 facing the transfer adhesive film 210. To provide stable adhesion, the side length of the side of the transfer adhesive film 210 in contact with the top surface is not less than 10 μm.

[0109] In this embodiment, the side of the transfer adhesive film 210 away from the top surface has periodic grooves 211. The periodic grooves 211 are located on the surface of the transfer adhesive film 210. The grooves 211 are generated by laser decomposition of the adhesive material to achieve core transfer. The spacing of the grooves 211 is no more than 7μm. If the spacing of the grooves 211 is too large, it is difficult to achieve core transfer and separation, and the adhesive material is easily pulled and shifted.

[0110] See Figure 24 In the sixth embodiment of the present invention, the difference from embodiment 5 is that the edge of the transfer adhesive film 210 is inclined, wherein the inclination angle is 40°~75°.

[0111] See Figure 25 and Figure 26 In a seventh embodiment of the present invention, a display is provided having a micro-light-emitting array. The micro-light-emitting array includes a plurality of micro-light-emitting diodes (LEDs). Each LED has a bottom surface, a top surface, and a side surface. The bottom surface is an electrical connection surface, and the top surface is a light-emitting surface. The micro-light-emitting array includes a first electrical connection layer 121, a second electrical connection layer 122, and a transfer adhesive film 210. The transfer adhesive film 210 is located on the top surface of the LEDs and does not extend beyond the edge of the top surface. The distance from the transfer adhesive film 210 to the edge of the top surface is 0.2 μm to 2 μm, or 2 μm to 10 μm. To improve the display effect, the thickness of the transfer adhesive film 210 can be reduced to no more than 0.5 μm, or, in extreme cases, the entire transfer adhesive film 210 can be removed. The side of the transfer adhesive film 210 away from the top surface has periodic grooves 211, and the spacing between the grooves 211 in the micro-light-emitting array is no more than 7 μm.

[0112] A circuit board 360 is provided on the bottom surface of the micro-light-emitting array of the display. The circuit board 360 includes a first conductive layer 361 that is bonded and electrically connected to the first electrical connection layer 121 and a second conductive layer 362 that is bonded and electrically connected to the second electrical connection layer 122. The micro-light-emitting array is fixed on the circuit board 360.

[0113] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and substitutions can be made without departing from the technical principles of the present invention, and these improvements and substitutions should also be considered within the scope of protection of the present invention.

Claims

1. A method for transferring a micro-luminescent array, comprising the following steps: (1) Provide a growth substrate, and fabricate a semiconductor layer sequence on the growth substrate, the semiconductor layer sequence including a first semiconductor layer, a second semiconductor layer and an active layer located between the two; (2) A separate semiconductor layer sequence is fabricated, the separate semiconductor layer sequence including a first mesa and a second mesa, and a first electrical connection layer and a second electrical connection layer are fabricated on the first mesa and the second mesa respectively. (3) Fix the side of the semiconductor layer sequence away from the growth substrate onto the first transfer substrate, and then remove the growth substrate; (4) A transfer adhesive film is formed on the top surface of the semiconductor layer sequence away from the first transfer substrate. The formation of the transfer adhesive film on the top surface of the semiconductor layer sequence away from the first transfer substrate includes: imprinting the first semiconductor layer into a transfer adhesive film fixed on the second transfer substrate, wherein the semiconductor layer sequence is fixed on the second transfer substrate by the transfer adhesive film; the top surface includes a first region and a second region, the second region surrounds the first region, the transfer adhesive film in the second region is etched away, the distance from the transfer adhesive film to the edge of the top surface is 0.2 μm to 2 μm, or 2 μm to 10 μm, and the thickness of the transfer adhesive film is not greater than 2 μm; thereafter, a portion of the transfer adhesive film is removed by laser.

2. The method for transferring micro-light-emitting arrays according to claim 1, characterized in that, It also includes step (5), which completely removes the transfer adhesive film.

3. A display, characterized in that, It is fabricated using the transfer method of the micro-luminescent array as described in claim 1 or 2.

Images