Display device and method of manufacturing the same

Abstract

A method for manufacturing a display device according to one embodiment of the present invention includes the steps of growing at least one light emitting diode (LED) on a first substrate, coating the first substrate with a selectable material, etching a region surrounding the at least one LED, disposing a buffer material at a location spaced apart from the at least one LED, and transferring the at least one LED positioned on the first substrate to a second substrate.

Description

Technical Field

[0001] This disclosure is applicable to all areas of technology related to display devices, and more specifically, for example, to display devices using micro light-emitting diodes (LEDs) and methods for manufacturing them. In particular, this disclosure simplifies the transfer process of RGB LED light sources, and thus can even be applied to high-resolution displays. Background Technology

[0002] Recently, display devices with excellent properties such as thinness and flexibility have been developed in the field of display technology. Currently, the main commercially available displays are represented by liquid crystal displays (LCDs) and organic light-emitting diodes (OLEDs).

[0003] In one example, light-emitting diodes (LEDs), as well-known semiconductor light-emitting devices that convert electric current into light, have been used as light sources for images displayed in electronic devices, including information and communication devices and electronic devices based on GaP:N green LEDs, beginning with the commercialization of red LEDs using GaAsP compound semiconductors in 1962. Therefore, using semiconductor light-emitting devices to implement displays can provide a solution to the aforementioned problems. Compared to filament-based light-emitting devices, semiconductor light-emitting devices have various advantages, such as longer lifespan, lower power consumption, superior initial drive characteristics, and higher vibration resistance.

[0004] Recently, the size of this semiconductor light-emitting device has been reduced to tens of micrometers. Summary of the Invention

[0005] Technical issues

[0006] One object of this disclosure is to provide a method that allows a light-emitting diode (LED) chip to be stably separated from a sapphire substrate and stably transferred to a donor substrate or wiring substrate without any impact.

[0007] Technical solution

[0008] To achieve this objective, a method of manufacturing a display device includes the following steps: growing at least one light-emitting diode (LED) on a first substrate; applying any material to the first substrate; etching a region around the at least one LED; disposing a buffer material at a location spaced apart from the at least one LED; and transferring the at least one LED located on the first substrate to a second substrate.

[0009] For example, the cushioning material may correspond to nanofibers.

[0010] For example, the interval position can be less than 10 μm.

[0011] For example, the arbitrary material may correspond to a polymer-based material (e.g., SU-8).

[0012] For example, the transfer step may also include the following steps: transferring the at least one LED to the buffer material once; and transferring the at least one LED disposed on the buffer material to the second substrate a second time.

[0013] For example, the laser used in the single transfer can be applied to all LEDs simultaneously.

[0014] For example, the laser used in the secondary transfer can be applied sequentially to each LED.

[0015] For example, the intensity of the laser used in the secondary transfer can be lower than the intensity of the laser used in the primary transfer (e.g., a high-power laser that separates GaN from the sapphire substrate).

[0016] For example, the first substrate may correspond to at least one of a sapphire substrate or a silicon substrate.

[0017] For example, the second substrate may correspond to at least one of a donor substrate or a wiring substrate.

[0018] Display devices manufactured according to any of the above methods also fall within the scope of this disclosure.

[0019] Beneficial effects

[0020] According to embodiments of this disclosure, there is a technical advantage that the light-emitting diode (LED) chip can be stably separated from the sapphire substrate, etc.

[0021] The technical advantage is that LED chips, which are separate from sapphire substrates, can be stably arranged on donor substrates or wiring substrates.

[0022] According to another embodiment of this disclosure, additional technical effects may exist that are not described herein. Such additional technical effects can be understood by those skilled in the art from the full disclosure of the specification and drawings. Attached Figure Description

[0023] Figure 1 A conventional transfer method using a donor substrate is shown.

[0024] Figure 2 A conventional remote transfer method is shown.

[0025] Figure 3 This diagram is used to explain the problems of conventional remote transfer methods from the perspective of chip separation via lasers.

[0026] Figure 4This diagram is used to explain the problems of conventional remote transfer methods from the perspective of receiving chips on the donor substrate.

[0027] Figure 5 This is a diagram used to explain the conditions for stably separating a light-emitting diode (LED) chip from a first substrate according to an embodiment of the present disclosure.

[0028] Figure 6 This is a diagram used to explain the conditions for stably capturing an LED chip on a second substrate according to an embodiment of the present disclosure.

[0029] Figure 7 This is a diagram used to explain the cushioning material required according to embodiments of this disclosure.

[0030] Figure 8 The preparation operations for a remote transfer process according to an embodiment of this disclosure are shown.

[0031] Figure 9 A remote transfer process according to an embodiment of this disclosure is illustrated.

[0032] Figure 10 This is a scanning electron microscope (SEM) image of an LED chip temporarily arranged on nanofibers according to an embodiment of the present disclosure.

[0033] Figure 11 These are images of various LED chips stably and ultimately arranged on a donor substrate or wiring substrate according to embodiments of the present disclosure. Detailed Implementation

[0034] A detailed description will now be given with reference to the accompanying drawings and exemplary embodiments disclosed herein. For the sake of brevity with reference to the drawings, identical or equivalent parts may have the same reference numerals and their descriptions will not be repeated. Generally, suffixes such as “module” and “unit” are used to refer to elements or components. Such suffixes are used herein merely for ease of description and are not intended to give any particular meaning or function. In this disclosure, for the sake of brevity, content well known to those skilled in the art is generally omitted. The drawings are provided to aid in the easy understanding of various technical features, and it should be understood that the embodiments presented herein are not limited to the drawings.

[0035] Although each figure has been described for ease of illustration, it will be apparent to those skilled in the art that another embodiment can be achieved by combining at least two or more figures, which also falls within the scope of this disclosure.

[0036] When an element such as a layer, region, or substrate is referred to as being “on” another element, it should be understood that the element may be directly on the other element, or there may be an intervening element therebetween.

[0037] The display device described herein is a concept encompassing all display devices that display information using a single pixel or a set of single pixels. Therefore, this display device can be applied not only to finished products but also to components. For example, a panel corresponding to a component of a digital television can independently correspond to the display device described herein. Finished products may include mobile phones, smartphones, laptop computers, digital broadcasting terminals, personal digital assistants (PDAs), portable multimedia players (PMPs), navigation devices, panel PCs, tablet PCs, ultrabooks, digital TVs, desktop computers, etc.

[0038] However, those skilled in the art will readily understand that the configuration according to the embodiments described herein can be applied to display devices, even if such devices are in the form of new products to be developed in the future.

[0039] The semiconductor light-emitting devices mentioned here include concepts such as LEDs and micro LEDs, and these terms can be used interchangeably.

[0040] Figure 1 A conventional transfer method using a donor substrate is illustrated. Figure 1 The transfers are executed in the order of (a), (b), and (c).

[0041] First, such as Figure 1 As shown in (a), at least one light-emitting diode (LED) 120 is arranged on a chip-on-a-wafer (COW) 110.

[0042] In addition, such as Figure 1 As shown in (b), the LED is attached to the donor substrate 130 using the mold 140, and then, as Figure 1 As shown in (c), the LED is finally transferred onto the wiring substrate 150.

[0043] However, according to existing technology, when using such Figure 1 When the donor substrate is transferred, the manufacturing cost increases, the time taken up increases, and the yield problem increases due to the increase in the number of processes.

[0044] There are limitations in supporting high-resolution displays. In other words, there are considerable problems in actual commercialization.

[0045] Some publicly disclosed remote transfer methods require a donor substrate, thus contact may be unavoidable during the transfer process. However, this presents limitations for application in large-area display devices and also increases costs.

[0046] Therefore, contactless remote transfer has been actively discussed. In this regard, reference will be made to... Figure 2 A description is provided below.

[0047] Figure 2 A conventional remote transfer method is shown.

[0048] like Figure 2 As shown, in a single transfer process using laser 210, chip 230 is selectively transferred directly from sapphire substrate 220 to wiring substrate 240. Because this method is non-contact, it is unaffected by the substrate, and therefore has the advantage that the same technology can be applied to both small and large display devices.

[0049] The non-contact transfer method also offers the advantage of ease of repair. For example, during initial inspection on the COW, it may not be necessary to attempt to transfer the chip at the fault location, and a good chip can subsequently be remotely transferred to the corresponding coordinates. If a chip is damaged during transfer, it has not yet been bonded, so it can be easily removed, and a remote transfer can be immediately performed to the same location.

[0050] However, Figure 2 The reason why the non-contact remote transfer shown is difficult to implement in practice is related to the transfer principle of GaN, which will be referred to below. Figure 3 Detailed description.

[0051] Figure 3 This diagram is used to explain the problems of conventional remote transfer methods from the perspective of chip separation via lasers.

[0052] First, the problem is that the chip 320 separates from the sapphire substrate 310 with excessive energy.

[0053] The instantaneous gas pressure increases the stress on chip 320, and this stress varies depending on the chip structure and process conditions. It is difficult for the force applied to the chip to have a uniform pressure distribution. That is, as shown in Equation 1 below, the pressure applied to the left, center, and right sides of the chip is different.

[0054] [Formula 1]

[0055] Due to the relationship expressed by the above formula, when the LED chip 320 separates from the sapphire substrate 310, the initial emission angle θ1 becomes larger, as shown in Formula 2 below.

[0056] [Equation 2]

[0057] Micro LEDs are thin films with a thickness of a few μm and relatively small weight, like a sheet of paper, making them susceptible to air resistance. Therefore, the final emission angle θf becomes random and satisfies the condition expressed by Equation 3 below.

[0058] [Formula 3]

[0059] That is, in the process of decomposing GaN into Ga and N2 gas using lasers, the chip is separated from the sapphire substrate by the pressure of the N2 gas. However, a problem arises because the chip is subjected to stress due to the gas pressure during separation, resulting in uneven separation across the entire attachment area of ​​the chip. Therefore, as... Figure 3 As shown, there is a high probability that chip 320 could fly away in any direction.

[0060] Figure 4 This diagram is used to explain the problems of conventional remote transfer methods from the perspective of receiving chips on the donor substrate.

[0061] From the perspective of the donor substrate, when the LED chip emitted from the sapphire substrate reaches the donor substrate, due to the excessive energy of the LED chip, it is difficult to improve the fracture (1) and bounce (2) characteristics simultaneously, even when the conditions of the donor substrate are optimized.

[0062] First, because the chip is incident with excessively high energy, breakage or bouncing is unavoidable depending on the angle of incidence. The following results occur depending on the range of the angle of incidence.

[0063] θ ~ 90 degrees: The probability of breakage increases, while the probability of bouncing decreases.

[0064] θ ~ 0 degrees: The probability of breakage decreases, while the probability of bouncing increases.

[0065] On the other hand, when the elastic modulus of the donor substrate increases to maximize the buffering effect, the probability of breakage increases, while the probability of bouncing decreases.

[0066] When the elastic modulus of the donor substrate is reduced to decrease the fracture problem, conversely, the probability of fracture decreases, but the probability of bounce increases.

[0067] That is, the chip released from the sapphire substrate flies toward the donor substrate or wiring substrate at a random angle θ with very high energy, so there are fundamental problems such as the chip may break and the chip's position is difficult to align.

[0068] Therefore, conventional discussions have concluded that non-contact remote transfer is difficult due to the trade-off between chip breakage and position control issues.

[0069] According to embodiments of this disclosure, it is important to allow the LED chip, which is separable from the sapphire substrate, to be stably separated. In this regard, reference will be made to… Figure 5 A description is provided below.

[0070] Figure 5 This is a diagram used to explain the conditions for stably separating an LED chip from a first substrate according to an embodiment of the present disclosure.

[0071] like Figure 5 As shown, when the LED 520 is separated from the first substrate 510 by the laser 530, the following equation 4 is satisfied.

[0072] [Formula 4]

[0073] Here, we assume that θ is random and difficult to control, and D is a factor that is highly sensitive to d. Therefore, in order to control the LED520 to the desired position, D decreases as d decreases.

[0074] For example, θ≤Φ / 2, therefore the maximum value (Max) of tanθ is 1, and the minimum value (Min) is 0. When the spacing between LED chips is 50 μm and the position error is assumed to be ±5 μm, d, which is the distance the chip flies towards the donor substrate or wiring substrate, needs to have a gap of 10 μm.

[0075] The following will refer to Figure 6 Description with sapphire substrate (e.g., Figure 5 The conditions under which the separate chip (as shown by reference numeral 510) can be stably positioned on the donor substrate or wiring substrate.

[0076] Figure 6 This is a diagram used to explain the conditions for stably capturing an LED chip on a second substrate according to an embodiment of the present disclosure.

[0077] like Figure 6 As shown in the left figure, depending on the angle of incidence of the chip as it flies toward the donor substrate or wiring substrate, breakage or bouncing may occur. This situation can be explained by the relationship between the chip's impact and momentum.

[0078] like Figure 6 As shown in the right figure, shock absorption is very important. However, when focusing on shock absorption, repulsive forces also need to be considered.

[0079] To address these various problems, according to embodiments of this disclosure, a buffer material (e.g., nanofibers) is introduced during the transfer process. This will be referenced below. Figure 7 Describe it.

[0080] Figure 7 This is a diagram used to explain the cushioning material required according to embodiments of this disclosure.

[0081] Typically, the impulse is obtained using Equation 5 below, and time needs to be increased to reduce the impact force.

[0082] [Formula 5]

[0083] The repulsive force is obtained through Equation 6 below, and in order to reduce the repulsive force, the time needs to be reduced.

[0084] [Formula 6]

[0085] In other words, to solve the chip breakage problem, it is important to minimize the impact force. To achieve this, t (time) can be increased.

[0086] On the other hand, to solve the chip bouncing problem, it is important to minimize the elastic modulus. To achieve this, if k can be set close to 0, the repulsive force also converges to 0.

[0087] However, t (time) depends on the elastic modulus (k), so it is impossible to increase t (time) while setting k (elastic modulus) close to 0.

[0088] That is, when the elastic modulus (k) decreases, the momentum time (t) decreases, thereby weakening the impact absorption. On the other hand, when the momentum time (t) of the chip flying toward the donor substrate due to continuous motion increases, the repulsive force caused by elasticity increases, resulting in the chip bouncing again.

[0089] However, the above assumption is based on a logical development that applies only to a single physical property, and the relationship can be defined differently from the above formula when a single physical property or a combination of multiple physical properties acts.

[0090] In order to design cushioning materials for long-distance transfer, we need to obtain the formula through modified Equation 6, which is the conventional relation described above.

[0091] This disclosure has derived the following formula, which is consistent with the law of conservation of momentum.

[0092] Equation 7 below is a standard relation.

[0093] [Formula 7]

[0094] Under the condition of a conventional single physical property, the following equation 8 is satisfied.

[0095] [Formula 8]

[0096] On the other hand, the new relations according to this disclosure in which the buffer material is introduced are represented by the following equations 9, 10 and 11.

[0097] [Formula 9]

[0098] [Formula 10]

[0099] [Equation 11]

[0100] Here, h is specified as the structural thickness factor.

[0101] According to an embodiment of this disclosure, in the case where composite physical properties are introduced into the cushioning material, Equation 12 is as follows.

[0102] [Equation 12]

[0103] Here, dt is the impulse absorption factor, and Δh is the repulsive force control factor.

[0104] In the above formula, the impact absorption time and momentum velocity are separated using a variety of physical properties. Let ∑ represent the elastic modulus of the material and hold momentum for time, and ∑ can be illustrated by a structure in which fibers are randomly entangled like cotton.

[0105] Therefore, nanofibers are suitable as buffer materials according to embodiments of the present disclosure, and h can be a variable factor for reducing repulsive forces, such as the thickness or density of the nanofibers.

[0106] Figure 8 The preparation operations for a remote transfer process according to an embodiment of this disclosure are shown.

[0107] like Figure 8 As shown in (a), at least one light-emitting diode (LED) 820 is grown on a first substrate 810. Here, the first substrate 810 corresponds to at least one of, for example, a sapphire substrate or a silicon substrate.

[0108] In addition, such as Figure 8 As shown in (b), the first substrate is coated with any material 830. Here, any material corresponds to, for example, a polymer-based material (e.g., SU-8).

[0109] For example, such as Figure 8As shown in (c), UV light is irradiated onto the substrate using an exposure device 840. Depending on the exposure method, the exposure device 840 can be classified as a stepper, a scanner, etc. A stepper irradiates light onto a corresponding area in a manner similar to taking a photograph with a camera, while a scanner forms a pattern by moving the light uniformly in a manner similar to a document scanner.

[0110] like Figure 8 As shown in (d), at least one area around an LED is etched. In this case, as referenced above... Figure 5 The value of d can be set to less than approximately 10 μm.

[0111] like Figure 8 As shown in (e), nanofibers 850, as an example of a buffer material, are arranged at a position spaced apart from the at least one LED.

[0112] The at least one LED disposed on the first substrate is designed to be transferred to the second substrate. Here, the second substrate corresponds to at least one of, for example, a donor substrate or a wiring substrate, and will be referred to below. Figure 9 A more specific process for transferring at least one LED to a second substrate is described.

[0113] Figure 9 A remote transfer process according to an embodiment of this disclosure is illustrated.

[0114] exist Figure 9 The first substrate shown in (a) is Figure 8 The substrate shown in (e) is flipped up and down.

[0115] like Figure 9 As shown in (b), at least one LED is transferred at a time to a buffer material (e.g., Figure 8 The figure shown is labeled 850, meaning nanofiber.

[0116] Then, as Figure 9 As shown in (c), at least one LED 940 disposed on the buffer material 930 is transferred to the second substrate 950 for a second time.

[0117] According to another embodiment of this disclosure, in Figure 9 In (b) a single transfer operation, laser 910 is applied to all LEDs simultaneously, and will Figure 9 In the secondary transfer operation of (c), the laser 920 used is sequentially applied to each LED.

[0118] According to another embodiment of this disclosure, although in Figure 9The laser 910 used in one transfer operation of (b) is a high-power laser capable of separating at least one LED chip from the sapphire substrate, but in Figure 9 The laser 920 used in the secondary transfer operation of (c) is designed to melt and cut nanofibers.

[0119] Figure 10 This is a scanning electron microscope (SEM) image of an LED chip temporarily arranged on nanofibers according to an embodiment of the present disclosure. Figure 11 These are images of various LED chips stably and ultimately arranged on a donor substrate or wiring substrate according to embodiments of the present disclosure. Figure 10 and Figure 11 This is a diagram used to illustrate the effects of this disclosure.

[0120] First, when Figure 9 When one of the transfers shown in (b) is completed, it can be seen that, as Figure 10 As shown, the LED chip 1010 is separated from the sapphire substrate and appropriately arranged on the nanofiber 1000. Figure 10 This corresponds to an image captured using a scanning electron microscope (SEM).

[0121] when Figure 9 When the secondary transition shown in (c) is completed, it can be seen that, as Figure 11 As shown, the LED chip is stably transferred to the donor substrate or wiring substrate, which serves as the second substrate, regardless of the chip's size and shape.

[0122] Using 4-inch chips Figure 11 The experiment. In Figure 11 In (a), this disclosure is applied to cases where the size of the LED chip is less than 40 μm. Figure 11 In (b), this disclosure is applied to cases where the size of the LED chip is less than 20 μm.

[0123] exist Figure 11 In (c), this disclosure is applied to the case where the LED chip has a circular shape, and Figure 11 In (d), this disclosure is applied to the case where the LED chip is a flip-type.

[0124] In all cases, the LED chip is stably transferred when non-contact transfer is performed according to this disclosure.

[0125] The above description is merely an illustration of the technical spirit of this disclosure, and various modifications and changes can be made by those skilled in the art without departing from the basic characteristics of this disclosure.

[0126] Therefore, the embodiments disclosed herein are intended to describe rather than limit the technical spirit of this disclosure, and the scope of the technical spirit of this disclosure is not limited by these embodiments.

[0127] The scope of protection of this disclosure shall be interpreted based on the following claims, and all technical ideas falling within its equivalent scope shall be interpreted as being included within the scope of this disclosure.

[0128] Invention methods

[0129] Various embodiments for implementing this disclosure have already been described above in the preceding section entitled “Detailed Description”, and therefore redundant descriptions thereof will be omitted.

[0130] Industrial applicability

[0131] This disclosure can be applied to display devices in various fields and therefore has industrial applicability.

Claims

1. A method for manufacturing a display device, the method comprising the following steps: At least one light-emitting diode (LED) is grown on the first substrate; Apply any material to the first substrate; Etch the area surrounding the at least one LED; A cushioning material is attached at a position spaced apart from the at least one LED; as well as The at least one LED located on the first substrate is transferred to the second substrate.

2. The method according to claim 1, wherein, The buffer material corresponds to nanofibers.

3. The method according to claim 1, wherein, The interval position is less than 10 μm.

4. The method according to claim 1, wherein, The arbitrary material refers to a polymer-based material.

5. The method according to claim 1, wherein, The transfer process also includes the following steps: Transfer the at least one LED to the buffer material in one step; and The at least one LED arranged on the buffer material is transferred to the second substrate.

6. The method according to claim 5, wherein, The laser used in the first transfer is applied simultaneously to all LEDs, and The laser used in the secondary transfer is applied sequentially to each LED.

7. The method according to claim 5, wherein, The output of the laser used in the secondary transfer is lower than that of the high-power laser used in the primary transfer to separate GaN from the sapphire substrate.

8. The method according to claim 1, wherein, The first substrate corresponds to at least one of a sapphire substrate or a silicon substrate.

9. The method according to claim 1, wherein, The second substrate corresponds to at least one of a donor substrate or a wiring substrate.

10. A display device manufactured according to the method of any one of claims 1 to 9.

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