KR102655631B1 - Apparatus and method of transfering led - Google Patents

Abstract

This specification discloses a light emitting diode (LED) transport device. The LED transfer device is. A head provided to lift an LED on one board and lower the LED on another board; a transport arm that moves the head; a cover provided to provide a closed space for accommodating the head and the one substrate or the other substrate; and a control unit that adjusts the air pressure of the closed space provided by the cover.

Description

LED transfer device and transfer method {APPARATUS AND METHOD OF TRANSFERING LED}

This specification relates to an LED transfer device and an LED transfer method using the device.

Liquid crystal displays and organic light emitting displays are widely used in screens of everyday electronic devices, such as cell phones and laptops, and their scope is gradually expanding. However, these display devices have limitations in reducing the size of the bezel area. For example, in the case of a liquid crystal display device, a sealant must be used to seal the liquid crystal and bond the upper and lower substrates, so there is a limit to reducing the size of the bezel area. In addition, in the case of organic light emitting display devices, the organic light emitting elements are made of organic materials and are very vulnerable to moisture or oxygen, so an encapsulation must be placed to protect the organic light emitting elements, so there is a limit to reducing the size of the bezel area. there is. Accordingly, when implementing a very large screen by arranging a plurality of liquid crystal displays or organic light emitting display devices in a tile form, there is a problem that the bezel area between adjacent panels is easily visible to the user.

As an alternative to this, display devices that use small LEDs as light-emitting elements are being studied. Since LEDs are made of inorganic materials rather than organic materials, they are highly reliable and have a longer lifespan than liquid crystal displays or organic light emitting displays. In addition, LED not only has a fast lighting speed, but also consumes less power, has excellent stability due to strong impact resistance, and can display high-brightness images, making it a device suitable for application to ultra-large screens. Above all, display devices using small LEDs as light-emitting devices can be implemented without a bezel, making them advantageous for application to ultra-large display devices in which multiple display devices are manufactured one after another.

Because securing productivity is essential for the commercialization of these small LED displays, various studies are being conducted to increase production speed and efficiency.

The purpose of this specification is to propose methods and equipment that can improve the production efficiency of small LED display devices. More specifically, we aim to provide a faster and safer LED transport device compared to the prior art. The tasks of this specification are not limited to the tasks mentioned above, and other tasks not mentioned will be clearly understood by those skilled in the art from the description below.

An LED transfer device according to an embodiment of the present specification includes a head provided to lift an LED on one substrate and lower the LED to another substrate; a transport arm that moves the head; a cover provided to provide a closed space for accommodating the head and the one substrate or the other substrate; and a control unit that adjusts the air pressure of the closed space provided by the cover.

The LED transfer device may further include a support provided to place the one substrate or the other substrate thereon and to provide the closed space together with the cover.

The head includes a plate connected to the transport arm; One side is bonded to the plate, and the other side provided to contact the LED may include a stamp with a fine groove. The stamp may be an elastic polymer having a predetermined elasticity, and the fine groove may have a diameter of 10 micrometers (μm) or less.

The control unit may be provided to set the pressure of the closed space to any one of atmospheric pressure, a first atmospheric pressure lower than the atmospheric pressure, and a second atmospheric pressure lower than the first atmospheric pressure.

According to another embodiment of the present specification, an LED transfer method for transferring a light emitting diode (LED) on one substrate to another substrate includes, at a standard atmospheric pressure, one side of the head having a fine groove on the upper surface of the LED on the one substrate. positioning; providing a first closed space including the substrate and the head, lowering the pressure inside the first closed space to a first air pressure lower than the reference air pressure, and bringing the head into contact with the upper surface of the LED; Raising the pressure inside the first sealed space to the reference pressure and lifting the head to separate the LED from the substrate; Positioning the separated LED and the head holding the LED on top of another substrate; lowering the head to bring the LED into contact with the other substrate; A second sealed space including a head holding the other substrate and the LED is provided, and the pressure inside the second closed space is lowered to a second air pressure lower than the first air pressure to release the attachment between the head and the LED. steps; It may include lifting the head and raising the pressure inside the second closed space to the reference atmospheric pressure.

Specific details of other embodiments are included in the detailed description and drawings.

The LED transfer device and transfer method according to the embodiments of the present specification can reduce LED damage in the process and also increase the transfer speed. This can lead to increased productivity of LED display devices. The effects according to the embodiments of the present specification are not limited to the contents exemplified above, and further various effects are included in the present specification.

1 is a plan view schematically showing an LED display device according to an embodiment of the present specification.
Figure 2 is a cross-sectional view showing the display area of an LED display device according to an embodiment of the present specification.
Figure 3 is a diagram showing the structure of an LED according to an embodiment of the present specification.
Figures 4a and 4b are diagrams briefly showing an LED transport device according to an embodiment of the present specification.
5A to 5I are diagrams showing an LED transport method according to an embodiment of the present specification.

The advantages and features of the present specification and methods for achieving them will become clear by referring to the embodiments described in detail below along with the accompanying drawings. However, the present invention is not limited to the embodiments disclosed below and will be implemented in various different forms. The present embodiments only serve to ensure that the disclosure of the present invention is complete and that common knowledge in the technical field to which the present invention pertains is not limited. It is provided to fully inform those who have the scope of the invention, and the present invention is only defined by the scope of the claims.

The shape, size, ratio, angle, number, etc. disclosed in the drawings for explaining the embodiments of the present specification are illustrative, and the present specification is not limited to the matters shown. Like reference numerals refer to like elements throughout the specification. Additionally, in describing the present invention, if it is determined that a detailed description of related known technologies may unnecessarily obscure the gist of the present invention, the detailed description will be omitted. When 'includes', 'has', 'consists of', etc. mentioned in this specification are used, other parts may be added unless 'only' is used. When a component is expressed in the singular, the plural is included unless specifically stated otherwise. When interpreting a component, it is interpreted to include the margin of error even if there is no separate explicit description.

In the case of a description of a positional relationship, for example, if the positional relationship of two parts is described as 'on top', 'on the top', 'on the bottom', 'next to', etc., 'immediately' Alternatively, there may be one or more other parts placed between the two parts, unless 'directly' is used. When an element or layer is referred to as “on” another element or layer, it includes instances where the other layer or other element is directly on top of or interposed between the other elements. When a component is described as being “connected,” “coupled,” or “connected” to another component, that component may be directly connected or connected to that other component, but there are no other components between each component. It should be understood that may be “interposed” or that each component may be “connected,” “combined,” or “connected” through other components.

Although first, second, etc. are used to describe various elements, these elements are not limited by these terms. These terms are merely used to distinguish one component from another. Accordingly, the first component mentioned below may also be the second component within the technical spirit of the present invention.

The size and thickness of each component shown in the drawings are shown for convenience of explanation, and the present invention is not necessarily limited to the size and thickness of the components shown. Hereinafter, various embodiments of the present invention will be described in detail with reference to the attached drawings.

1 is a plan view schematically showing an LED display device according to an embodiment of the present specification.

The LED display device 100 may be composed of a plurality of pixels (P) disposed on a substrate 110. The pixel P may include a red sub-pixel 140R, a green sub-pixel 140G, and a blue sub-pixel 140B.

Each of the sub-pixels 140R, 140G, and 140B may be equipped with a thin film transistor (TFT) and an LED 140 as a driving element and a light-emitting element. The LED 140 and the thin film transistor may be connected to a driver such as a gate control circuit and a data control circuit through wiring such as a gate line and data line. If the chip size (width) of the LED 140 is less than 100 micrometers (μm), it is also called a micro LED display device. Meanwhile, if the chip size of the LED 140 is about several hundred micrometers, it is also called a mini LED display device.

The LED 140 may be manufactured separately from the array process of the substrate 110. In an organic light emitting display device, both the TFT and the light emitting element are formed through a photo process, while in the case of an LED display device, the TFT is formed through a photo process, but the LED 140 is manufactured through a separate process and then printed on the substrate 110. ) can be transferred to the As an example, the LED 140 can be obtained by growing an inorganic material such as Al, Ga, N, P, or As In on a growth substrate (sapphire substrate or silicon substrate) and then separating it from the growth substrate.

Figure 2 is a cross-sectional view showing the display area of an LED display device according to an embodiment of the present specification.

The LED display device 100 may be defined with a display area where an image is displayed (Active Area) and a non-display area surrounding the display area (Inactive Area). A light-emitting device (eg, LED) and a driving device (eg, thin film transistor) for driving the light-emitting device may be disposed in the display area. The non-display area is an area where images are not displayed, and various wiring and control circuits connected to elements arranged in the display area may be placed. Referring to FIG. 2, it can be seen that the LED display device according to an embodiment of the present specification is formed in a structure in which various functional elements are stacked on a substrate 110. The substrate 110 is a substrate that supports components and may be an insulating material. For example, the substrate 110 may be made of glass or resin. Additionally, the substrate 110 may be made of polymer or plastic. In some embodiments, the substrate 110 may be made of a material having flexibility or foldability.

The thin film transistor (TFT) includes a gate electrode 101 formed on a substrate 110; A gate insulating layer 112 covering the gate electrode 101; a semiconductor layer 103 formed on the gate insulating layer 112; It may be composed of a source electrode 105 and a drain electrode 107 on the semiconductor layer 103.

The gate electrode 101 may be formed of Cr, Mo, Ta, Cu, Ti, Al, or an alloy thereof, and the gate insulating layer 112 may be a single layer made of an inorganic insulating material such as SiOx or SiNx, or SiOx and It may be composed of a plurality of layers made of SiNx.

The semiconductor layer 103 may be composed of an amorphous semiconductor such as amorphous silicon, or an oxide semiconductor such as IGZO (Indium Gallium Zinc Oxide), TiO2, ZnO, WO3, or SnO2. Of course, the semiconductor layer of the thin film transistor is not limited to a specific material, and all types of semiconductor materials currently used in thin film transistors can be used.

The source electrode 105 and the drain electrode 107 may be made of metal such as Cr, Mo, Ta, Cu, Ti, Al, or an alloy thereof. At this time, the drain electrode 107 acts as a first electrode that applies a signal to the LED.

Meanwhile, the illustrated thin film transistor (TFT) is a bottom gate type thin film transistor, but thin film transistors of other structures, such as a top gate type thin film transistor, can also be applied as an embodiment of the present invention. .

A second electrode 109 is formed on the gate insulating layer 112 in the display area. At this time, the second electrode 109 may be formed of Cr, Mo, Ta, Cu, Ti, Al, or an alloy thereof, and may be formed through the same process as the drain electrode of the thin film transistor.

A first insulating layer 114 is formed on the source electrode 105, the drain electrode 107, and the second electrode 109, and the LED 140 is disposed on the first insulating layer 114. In the embodiment of FIG. 2, a portion of the first insulating layer 114 is removed and the LED 140 is placed in the corresponding area, but the first insulating layer 114 may not be removed. The first insulating layer 114 may be composed of an organic layer such as photoacrylic, an inorganic layer/organic layer, or an inorganic layer/organic layer/inorganic layer.

A second insulating layer 116 is located on the first insulating layer 114. At this time, the second insulating layer 116 may be composed of an organic layer such as photoacrylic, may be composed of an inorganic layer/organic layer, or may be composed of an inorganic layer/organic layer/inorganic layer, and may be composed of an inorganic layer/organic layer/inorganic layer. Covers the area.

A first contact hole 114a and a second contact hole 114b are formed in the first insulating layer 114 and the second insulating layer 116 on the thin film transistor (TFT) and the second electrode 119, respectively. Thus, the drain electrode 107 and the second electrode 119 of the thin film transistor (TFT) are exposed to the outside, respectively. In addition, the second insulating layer 116 above the p-type electrode 141 and the n-type electrode 143 of the LED 140 has a third contact hole 116a and a fourth contact hole 116b, respectively. is formed so that the p-type electrode 141 and the n-type electrode 143 are exposed to the outside.

A first connection electrode 117a and a second connection electrode 117b made of transparent metal oxide such as ITO, IGZO or IGO are formed on the second insulating layer 116, thereby forming the first contact hole 114a. And the drain electrode 107 of the thin film transistor (TFT) and the p-type electrode 141 of the LED 140 are electrically connected to the first connection electrode 117a through the third contact hole 116a, The second electrode 109 and the n-type electrode 143 of the LED 140 are electrically connected to the second connection electrode 117b through the second contact hole 114b and the fourth contact hole 116b.

On the upper surface of the substrate 110, a buffer layer 118 made of an inorganic material and/or an organic material may cover and protect the LED 140.

Figure 3 is a diagram showing the structure of an LED according to an embodiment of the present specification.

The LED 140 may be a micro LED with a size of 10 to 100 μm. The LED 140 includes an undoped GaN layer 144, an n-type GaN layer 145 disposed on the GaN layer 144, and a multiple quantum well disposed on the n-type GaN layer 145. -An active layer 146 having a Quantum-Well (MQW) structure, a p-type GaN layer 147 disposed on the active layer 145, and a transparent conductive material formed on the p-type GaN layer 147. An ohmic contact layer 148 disposed, a p-type electrode 141 in contact with a portion of the ohmic contact layer 148, the active layer 146, a p-type GaN layer 147 and an ohmic contact layer 148 ) is composed of an n-type electrode 143 that is in contact with a portion of the n-type GaN layer 145 that is exposed by etching a portion of the layer.

The n-type GaN layer 145 is a layer for supplying electrons to the active layer 146, and is formed by doping an n-type impurity such as Si into the GaN semiconductor layer.

The active layer 146 is a layer that emits light by combining injected electrons and holes. The multi-quantum well structure of the active layer 146 includes a plurality of barrier layers and well layers arranged alternately, and the well layer may be composed of an InGaN layer and the barrier layer may be composed of GaN, but is not limited thereto.

The p-type GaN layer 147 is a layer that injects holes into the active layer 146, and is formed by doping the GaN semiconductor layer with p-type impurities such as Mg, Zn, and Be.

The ohmic contact layer 148 is for ohmic contact between the p-type GaN layer 147 and the p-type electrode 141, and is made of Indium Tin Oxide (ITO), Indium Galium Zinc Oxide (IGZO), A transparent metal oxide such as IZO (Indium Zinc Oxide) may be used.

The p-type electrode 141 and the n-type electrode 143 may be composed of a single layer or multiple layers made of at least one metal selected from Ni, Au, Pt, Ti, Al, and Cr or an alloy thereof. .

In the LED 140 of this structure, as a voltage is applied to the p-type electrode 141 and the n-type electrode 143, the active layer ( 145), when electrons and holes are respectively injected, excitons are generated within the active layer 146, and as these excitons decay, LUMO (Lowest Unoccupied Molecular Orbital) and HOMO (Highest Unoccupied Orbital) of the light-emitting layer Light corresponding to the energy difference of Occupied Molecular Orbital is generated and radiated to the outside. At this time, the wavelength of light emitted from the LED 140 can be adjusted by adjusting the thickness of the barrier layer of the multi-quantum well structure of the active layer 146.

The LED 140 is manufactured by forming a buffer layer on a substrate and growing a GaN thin film on the buffer layer. At this time, sapphire (sapphire), silicon (si), GaN, silicon carbide (SiC), gallium arsenide (GaAs), zinc oxide (ZnO), etc. may be used as a substrate for the growth of the GaN thin film.

The buffer layer prevents quality degradation due to lattice mismatch that occurs when the n-GaN layer 120, which is an epi layer, is directly grown on the substrate when the substrate for GaN thin film growth is made of a material other than the GaN substrate. To prevent this, AlN or GaN may be used.

The n-type GaN layer 145 may be formed by growing a GaN layer 144 that is not doped with impurities and then doping an n-type impurity, such as Si, on top of the undoped thin film. Additionally, the p-type GaN layer 147 can be formed by growing an undoped GaN thin film and then doping it with p-type impurities such as Mg, Zn, and Be.

The LED 140 made through the above process is transferred to the substrate 110 as shown in FIG. 2 and used in a display device. At this time, the process of transferring the LED 140 is also called transfer. Representative examples of the transfer process are direct transfer and print transfer.

The direct transfer is a technology that directly bonds the material or thin film to be transferred to the target substrate. As an example of the direct transfer, a method of separating p-type GaN into several micro-sized pieces through an etching process and then directly bonding it to the substrate on which the switching device is formed can be used.

Meanwhile, print transfer is a technology that utilizes an intermediate medium such as an electrostatic stamp or bonded stamp. As transfer equipment used in the above print transfer method, it is known that ⅰ) using an electrostatic head and ⅱ) using an elastomer stamp as a pickup device for picking up the LED. In the above ⅰ), voltage is applied to the head portion to generate adhesion to the LED due to charging phenomenon. This method has the advantage of being able to selectively transfer a desired area or a single element, but it may cause the LED to be damaged by the voltage applied to the head during electrostatic induction. Above ii) is a method of transferring an LED to a desired substrate using an elastic polymer material as a transfer head. This method has no problems with LED damage compared to the electrostatic head method, but the transfer speed is slow and it is based on the Wan der Waals force, which is weaker than other bonding forces, so it is difficult to control the pickup intensity and/or sustainability. there is.

The inventors of this specification recognized the pros and cons of the above LED transport methods and devised a solution to solve the problem of LED damage and transport stability.

Figures 4a and 4b are diagrams briefly showing an LED transport device according to an embodiment of the present specification.

The LED transfer device that transfers the above-described LED from one substrate to another may be composed of several functional units. Hereinafter, a pickup unit that picks up the LED 140 from a substrate and lowers it to another substrate is referred to as a pickup unit. The description will focus on the LED transport device. The LED transfer device is equipped with a control unit and can control various functional units including the pickup unit. The substrate 10 shown in FIG. 4A is a substrate before the LED transfer is completed, and may be a growth substrate on which the LED 140 is generated, or it may be a transport substrate at a stage before the LED is finally mounted.

The pickup unit includes a head 230 provided to lift the LED 140 on one substrate and lower the LED 140 to another substrate; A transport arm (arm, 220) that moves the head (230); It may include a cover 250 provided to provide a specific space to accommodate the head 230 and the one substrate or the other substrate. Meanwhile, the control unit controls the attachment or detachment of the LED 140 from the head 230 by adjusting the air pressure of the closed space provided by the cover 250.

In addition, the LED transfer device may further include a support 210 provided to place the one substrate or the other substrate thereon and to provide a closed space together with the cover 250. In another embodiment, the support 210 may be configured separately from the LED transfer device.

The head 230 includes a plate 231 connected to the transport arm 220; One side is bonded to the plate 231, and the other side provided to contact the LED 140 may include a stamp 232 with a fine groove.

Figure 4b shows an example of the stamp 232. The stamp 232 may be made of an elastomer with a certain elasticity so as not to be shocked when in contact with the LED. For example, the stamp 232 may be made of polymeric organosilicon such as rubber or PDMS. The stamp 232 has one or more fine grooves on one side. The fine grooves may have a cylindrical, conical, or polygonal pillar shape, and several of them are placed on the upper surface of the LED 140. Accordingly, the LED 140 can be held or released depending on the difference between the pressure inside the fine groove and the pressure outside it. At this time, it is appropriate for the stamp 232 to have elasticity (layer pushing elastic coefficient of about 10 ^-3 to ^{10 -1} GPa) so that it is not pushed away from the upper surface of the LED 140 when contacted. The fine grooves may have a diameter of 10 micrometers (μm) or less and may be formed to occupy 40 to 80% of the total stamp area. Additionally, the depth of the fine groove may be 2 to 5 times the diameter.

In the drawing, the plate 231 and the stamp 232 are depicted separately, but the two parts may be one integrated piece. That is, a stamp with a fine groove on one side may be directly connected to the transport arm 220.

The transport arm 220 is connected to the head and moves the head 230 three-dimensionally under the control of a control unit. The cover 250 may be seated on the upper part of the support 210 to form a predetermined closed space (chamber). The enclosed space created in this way is very small, so vacuum levels of 10 ^-1 atm or less can be easily created.

The control unit is provided to set the pressure of the closed space to one of atmospheric pressure, a first atmospheric pressure lower than the atmospheric pressure, and a second atmospheric pressure lower than the first atmospheric pressure. Here, the first atmospheric pressure may be 10 ^-1 atm, and the second atmospheric pressure may be 10 ^-2 atm. At this time, in order to change the air pressure, a passage for air in and out may be provided in the cover 250 and/or the support 210. Additionally, known equipment such as a vacuum pump may be used to control the pressure inside the enclosed space.

5A to 5I are diagrams showing an LED transport method according to an embodiment of the present specification.

According to an embodiment of the present specification, a method of transferring a light emitting diode (LED) on one substrate to another substrate may be performed by the LED transfer device described in FIGS. 4A and 4B. The method can be performed as follows.

First, one side of the head 230 having a fine groove is placed on the upper surface of the LED 140 on the substrate 10. At this time, the head 230 is provided with an elastic stamp made of a polymer material on one side, and the elastic stamp has at least one fine groove. The head 230 may contact only a portion of the LEDs to be picked up among all LEDs on the substrate 10. This is to meet the LED arrangement conditions required for the substrate to be transferred. The process may be carried out at a reference atmospheric pressure (eg, 1 atm).

Next, as shown in FIG. 5A, a first sealed space including the substrate 10 and the head 230 is prepared, and the pressure inside the first closed space is set to a first atmospheric pressure (L1) lower than the reference atmospheric pressure. lower it The first atmospheric pressure (L1) may be about 10 ^-1 atm. The first closed space may be formed by the cover 250 being in close contact with the support 210. Thereafter, as shown in FIG. 5B, the head 230 is brought into contact with the upper surface of the LED 140 while the inside of the closed space is at the first atmospheric pressure L1.

Next, as shown in FIG. 5C, the pressure inside the first closed space is raised to the reference atmospheric pressure (L0). At this time, the inside of the fine groove is maintained at the first atmospheric pressure (L1). Thereafter, as shown in FIG. 5B, the head 230 is lifted to separate the LED 140 from the substrate 10. At this time, the LED 140 is separated from the substrate 10 by the vacuum inside the micro groove and is raised together with the head 230.

Next, as shown in FIG. 5E, the separated LED 140 and the head 230 holding the LED 140 are placed on the top of the other substrate 20. Here, the other substrate 20 may be a final substrate or an intermediate transport substrate. The above process may be carried out at reference atmospheric pressure (L0). At this time, the inside of the fine groove is still maintained at the first atmospheric pressure (L1).

Next, as shown in FIG. 5F, the head 230 is lowered to bring the LED 140 into contact with the other substrate 20. Before or after the contact, a second sealed space including the head 230 holding the other substrate 20 and the LED 140 is provided. Thereafter, as shown in FIG. 5G, the pressure inside the second closed space is lowered to a second atmospheric pressure (L2) lower than the first atmospheric pressure (L1). The second atmospheric pressure (L2) may be about 10 ^-2 atm. Due to this change in air pressure, the vacuum adhesion force caused by the micro grooves is lost and the adhesion between the head 230 and the LED 140 is released.

Next, as shown in FIG. 5H, the head 230 is lifted, and as shown in FIG. 5I, the pressure inside the second closed space is raised to the reference air pressure (L0). Then, when the cover 250 and head 230 are lifted, the transfer process is completed.

The LED transfer device and transfer method described above reduces damage to the LED compared to the conventional transfer method, and the transfer speed can also be shortened from several minutes (min) to several seconds (s). This can lead to increased productivity of LED display devices.

Although embodiments of the present specification have been described in detail with reference to the attached drawings, the present specification is not necessarily limited to these embodiments, and various modifications may be made without departing from the technical spirit thereof. Accordingly, the embodiments disclosed in this specification are not intended to limit the technical idea of the present invention, but rather to explain it, and the scope of the technical idea of the present invention is not limited by these embodiments. Each feature of the various embodiments of the present invention can be partially or entirely combined or combined with each other, and can be technically linked and driven in various ways by those skilled in the art, and each embodiment can be performed independently of each other or together in a related relationship. It may be implemented. The scope of protection of the present invention should be interpreted in accordance with the claims below, and all technical ideas within the equivalent scope should be construed as being included in the scope of rights of the present invention.

Claims (14)

A light emitting diode (LED) transfer device, comprising:
A head provided to lift an LED on one board and lower the LED on another board;
a transport arm that moves the head;
a cover provided to provide a closed space for accommodating the head and the one substrate or the other substrate;
a control unit that adjusts the air pressure of the closed space provided by the cover; and
An LED transfer device comprising a support provided to place the one substrate or the other substrate on top of the substrate and to provide the closed space together with the cover. delete According to claim 1,
The head is,
a plate connected to the transport arm; and
An LED transfer device comprising a stamp that is bonded to the plate on one side and has a fine groove on the other side that is provided to contact the LED. According to clause 3,
An LED transport device, wherein the stamp is an elastomer having a predetermined elasticity. According to clause 3,
The micro groove has a diameter of 10 micrometers (μm) or less. According to claim 1,
The control unit is provided to bring the pressure of the enclosed space to any one of atmospheric pressure, a first atmospheric pressure lower than the atmospheric pressure, and a second atmospheric pressure lower than the first atmospheric pressure. In a method of transferring a light emitting diode (LED) on one substrate to another substrate,
At a reference atmospheric pressure, positioning one side of a head having a fine groove on the upper surface of the LED on the one substrate;
providing a first closed space including the substrate and the head, lowering the pressure inside the first closed space to a first air pressure lower than the reference air pressure, and bringing the head into contact with the upper surface of the LED;
Raising the pressure inside the first sealed space to the reference pressure and lifting the head to separate the LED from the substrate;
Positioning the separated LED and the head holding the LED on top of another substrate;
lowering the head to bring the LED into contact with the other substrate;
A second sealed space including a head holding the other substrate and the LED is provided, and the pressure inside the second closed space is lowered to a second air pressure lower than the first air pressure to release the attachment between the head and the LED. steps;
A method comprising lifting the head and raising the pressure inside the second enclosed space to the reference atmospheric pressure. According to clause 7,
In the step of separating the LED from the one substrate, the inside of the micro groove is maintained at the first atmospheric pressure. According to clause 7,
The method of claim 1, wherein the head contacts only some of the LEDs on the substrate. According to clause 7,
The reference atmospheric pressure is 1 atm, the first atmospheric pressure is 10 ^-1 atm, and the second atmospheric pressure is 10 ^-2 atm. According to clause 7,
The method of claim 1, wherein the LED has a width of 100 micrometers (μm) or less. According to clause 7,
The method of claim 1, wherein the head has an elastic stamp made of a polymer material on one surface, and the elastic stamp has at least one micro groove. According to claim 12,
The method of claim 1 , wherein the fine grooves have a diameter of 10 micrometers (μm) or less and a depth of 2 to 5 times the diameter. According to claim 12,
The method wherein the micro grooves occupy 40 to 80% of the stamp area.

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