KR20220139703A - Method for aligning fluid-based micro led - Google Patents

Abstract

Disclosed is a fluid-based micro LED alignment method capable of aligning a micro LED in a groove by moving a fluid including a micro LED in one direction along a surface of a substrate using a blade. The fluid-based micro LED alignment method according to the present invention comprises the steps of: (a) preparing a substrate with a groove and a fluid including a micro LED; (b) supplying the fluid including the micro LED onto the substrate with the groove; and (c) aligning the micro LED to the groove. In the step (b), the fluid including the micro LED is supplied to a blade in a state of being in contact therewith, so that the fluid including the micro LED moves in one direction along the surface of the substrate.

Description

METHOD FOR ALIGNING FLUID-BASED MICRO LED

The present invention relates to a fluid-based micro LED alignment method capable of aligning a micro LED in a specific groove by moving a fluid including the micro LED in one direction along the surface of a substrate.

LEDs based on compound semiconductors are fabricated through thin-film growth on sapphire or silicon substrates. In general, an LED having a size of 100 μm or more has a disadvantage in that it is damaged during external impact and bending.

Recently, many attempts have been made to develop a micro LED with a size of 100 μm or less.

By transferring the micro LED onto a flexible substrate, a display that can be folded or bent can be made, and it can be applied to various fields such as smart textiles, body-attached and implantable medical devices.

Micro LED has advantages of higher power efficiency and shorter response time than conventional LEDs and OLEDs. In addition, micro LED has a long lifespan and high luminance, so it can be applied to products such as smart watches, VLC (Visible Light Communication), automotive electronic components, and HMD (Head Mounted Display).

In addition, it can be applied to ultra-high-resolution TVs, smart glasses, AR (Augmented Reality) glasses, etc. that require a high number of pixels per unit area with a size of several μm to several tens of μm.

In the manufacturing technology using the micro LED, the micro LED may be divided into a micro LED device manufacturing technique, a micro LED transfer/bonding technique, and a micro LED display manufacturing technique.

Micro LED display consumes much less power than existing OLED displays and has excellent screen brightness, so it is also expected that micro LED display technology will be applied to smart watches, which are wearable devices.

Recently, we have developed an alignment method of micro LEDs through movement control. The principle is that bonding force is generated by Van Der Waals, and the bonding strength is adjusted by controlling the speed of peeling off the flexible stamp (PDMS). It is a technology that separates micro LEDs by controlling

As such, in manufacturing technology using micro LEDs, micro LED bonding technology has the highest technical barrier and many tasks to be solved.

As a method of bonding micro LEDs, there are a method using an elastic rubber stamp, a method using an electrostatic head, a laser irradiation method using a thermal release tape, and a roll to roll method.

In the prior art described above, physical damage to the micro LED inevitably occurs, which adversely affects the driving of the micro LED. In addition, there is a disadvantage in that the yield is reduced when sorting in large quantities because it cannot be precisely controlled when assembling.

Therefore, there is a need for an alignment technology that can minimize damage to the micro LED and obtain a high yield.

It is an object of the present invention to provide a fluid-based micro LED alignment method capable of aligning micro LEDs in a specific groove.

It is an object of the present invention to provide a fluid-based micro LED alignment method capable of aligning one micro LED in one groove.

It is also an object of the present invention to provide a fluid-based micro LED alignment method capable of self-aligning over a large area.

It is also an object of the present invention to provide a fluid-based micro LED alignment method with improved yield and minimizing damage to micro LEDs.

It is also an object of the present invention to provide a fluid-based micro LED alignment method capable of minimizing an error range for an alignment position.

It is also an object of the present invention to provide a method for aligning micro LEDs having the effect of shortening the process time by shortening the drying time of the substrate and also shortening the time for aligning the micro LEDs.

The objects of the present invention are not limited to the above-mentioned objects, and other objects and advantages of the present invention not mentioned may be understood by the following description, and will be more clearly understood by the examples of the present invention. It will also be readily apparent that the objects and advantages of the present invention may be realized by the means and combinations thereof indicated in the appended claims.

A fluid-based micro LED alignment method according to the present invention comprises the steps of: (a) providing a substrate in which a groove is formed and a fluid including the micro LED; (b) supplying a fluid including the micro LED onto a substrate in which a groove is formed; and (c) aligning the micro LED to the groove; and supplying the fluid containing the micro LED to the blade in a state in which the fluid is in contact with the blade in step (b) to apply the fluid containing the micro LED to the substrate. It moves in one direction along the surface.

The fluid-based micro LED alignment method according to the present invention can align micro LEDs in a specific groove and align one micro LED in one groove.

In addition, the fluid-based micro LED alignment method according to the present invention enables self-alignment over a large area, and can improve assembly yield at low cost.

In addition, the fluid-based micro LED alignment method according to the present invention has the effect of minimizing damage to the micro LED and minimizing the error range for the alignment position.

In addition, the fluid-based micro LED alignment method according to the present invention has the effect of shortening the process time by shortening the drying time of the substrate and greatly shortening the assembly time of the micro LED.

In addition, the fluid-based micro LED alignment method according to the present invention can be applied to the manufacture of high-resolution next-generation displays, smart watches, smart glasses, and medical optical sensors.

In addition to the above-described effects, the specific effects of the present invention will be described together while describing specific details for carrying out the invention below.

1 is a flowchart illustrating a fluid-based micro LED alignment method according to the present invention.
2 is a schematic diagram of a fluid-based micro LED alignment process according to the present invention.
3 and 4 are schematic diagrams of a process of additionally generating an electric field in the fluid-based micro LED alignment method according to the present invention.

The above-described objects, features and advantages will be described below in detail with reference to the accompanying drawings, and accordingly, those skilled in the art to which the present invention pertains will be able to easily implement the technical idea of the present invention. In describing the present invention, if it is determined that a detailed description of a known technology related to the present invention may unnecessarily obscure the gist of the present invention, the detailed description will be omitted. Hereinafter, preferred embodiments according to the present invention will be described in detail with reference to the accompanying drawings. In the drawings, the same reference numerals are used to refer to the same or similar components.

In the following, that an arbitrary component is disposed on the "upper (or lower)" of a component or "top (or below)" of a component means that any component is disposed in contact with the upper surface (or lower surface) of the component. Furthermore, it may mean that other components may be interposed between the component and any component disposed on (or under) the component.

Also, when it is described that a component is “connected”, “coupled” or “connected” to another component, the components may be directly connected or connected to each other, but other components are “interposed” between each component. It is to be understood that “or, each component may be “connected”, “coupled” or “connected” through another component.

Hereinafter, a fluid-based micro LED alignment method according to some embodiments of the present invention will be described.

The present invention is a technology for aligning the micro LEDs to the precise positions of the grooves based on the fluid.

The fluid referred to in the present invention may mean including both a liquid and a gas, and preferably may mean a liquid, which is a material that can flow freely.

The micro LED referred to in the present invention is a miniature light emitting material having a longest side length of about 100 μm or less. The micro LED is an organic and/or inorganic material dispersed in a fluid, and may have various sizes of 1D, 2D, or 3D shapes.

Specifically, the micro LED of the present invention may be in the form of a nanowire having a length, a disk shape having an aspect ratio of 0.5 to 2, or a miniature light emitting material in the shape of a cube.

Preferably, the micro LED of the present invention may be in the form of a disk or cube having an aspect ratio of 0.5 to 2.

For example, the disk-shaped or cube-shaped micro LED has an n-type semiconductor layer, an active layer disposed on the n-type semiconductor layer, a p-type semiconductor layer disposed on the active layer, and an insulating layer surrounding at least an outer circumferential surface of the active layer. and a multilayer electrode part disposed on an outer circumferential surface of the insulating layer. The multi-layer electrode part may include a first layer that is an ohmic junction electrode electrically connected to the p-type semiconductor layer, and a second layer disposed on the first layer and having excellent reflection and bonding characteristics, but is limited thereto. it is not

In the present invention, it will be described on the assumption that the micro LED has a disk shape or a cube shape.

1 is a flowchart illustrating a fluid-based micro LED alignment method according to the present invention.

Referring to FIG. 1 , the fluid-based micro LED alignment method according to the present invention includes a step of preparing a grooved substrate and a fluid including the microLED (S110), and applying a fluid including the microLED onto the grooved substrate. It includes the step of supplying to the (S120) and the step of aligning the micro LED to the groove (S130).

In particular, by moving the fluid containing the micro LED (ML) in one direction along the surface of the substrate when the fluid containing the micro LED (ML) is supplied on the substrate 10 in which the groove is formed, the micro LED (ML) in a non-contact manner ) can be aligned to the exact position of the groove.

The step (S110) of preparing the substrate on which the grooves are formed and the fluid including the micro LED is as follows.

The groove indicates a space in which the micro LED electrically connected to the electrode layer is disposed. In the substrate, the electrode layer and the insulating layer may be designed in various arrangement structures.

For example, as shown in FIG. 2 , one electrode layer 20 may be disposed on the substrate 10 , and an insulating layer 30 may be disposed between the electrode layers 20 .

In this case, the micro LED 30 may be disposed on one electrode layer 20 .

In addition, as shown in FIG. 3 , the substrate 10 includes an insulating layer 30 spaced apart on the first electrode layer 22 and a second electrode layer 24 spaced apart on each insulating layer 30 . can do.

A region between one insulating layer and the other insulating layer may be designed as a groove.

In this case, a micro LED (ML) may be disposed on the first electrode layer 22 .

In addition, as shown in FIG. 4 , the substrate 10 includes a first electrode layer 22 that is primarily spaced apart from each other in the insulating layer 30 having a thickness, and secondarily in the thickness direction of the insulating layer 30 . to include a second electrode layer 24 spaced apart from the first electrode layer 22 , and may include an insulating layer 30 spaced apart from the second electrode layer 24 .

A region between one insulating layer and the other insulating layer may be designed as a groove.

In this case, a micro LED (ML) may be disposed on the second electrode layer 24 .

In this way, the electrode layer may be disposed on the bottom surface of the groove.

Although the substrate in which the groove is formed has been described with reference to FIGS. 2 to 4 , the configuration of the groove using the electrode layer and the insulating layer may be changed according to the embodiment, but is not limited thereto.

The substrate 10 may be an active matrix backplane or an active matrix backplane.

The fluid including the micro LED (ML) may mean including both a liquid and a gas, and preferably may mean a liquid, which is a material that can flow freely.

The fluid includes a plurality of micro LEDs and may include a liquid having a suitable dielectric constant.

The liquid may include various kinds of organic solvents and/or distilled water.

For example, the liquid may include one or more of isopropyl alcohol, acetone, toluene, ethanol, methanol, glycerin, and distilled water, but is not limited thereto.

The concentration of micro LEDs (ML) in the fluid may include 10 ⁷ to 10 ¹² micro LEDs per liter of organic solvent and/or distilled water. If the concentration of micro LEDs is out of 10 ⁷ to 10 ¹² pcs/L, it may be difficult to place one micro LED in one groove.

Then, a fluid including the micro LED (ML) is supplied on the substrate 10 in which the groove is formed to align the micro LED (ML) with the groove.

2 to 4, when supplying the fluid containing the micro LED (ML) to the blade 40 in a contact state, when supplying the fluid on the substrate 10, the micro LED (ML) It is important to move the containing fluid in one direction along the surface of the substrate 10 .

The upper surface of the fluid is in contact with the blade 40 . A fluid may be placed between the blade 40 and the substrate 10 , and the fluid may be supplied in contact with the blade 40 .

The blade 40 is designed to continuously supply a uniform amount of fluid onto the surface of the substrate 10 , and serves to drag the fluid in one direction.

The blade 40 may be a device having a predetermined volume for supplying a fluid.

For example, the blade receives a fluid supply and uniformly distributes the cavity block having an accommodating space, a front portion disposed on the front surface of the cavity block, a front portion disposed in parallel with the front portion, and in contact with the outer circumferential surface of the cavity block is disposed, and may include a rear portion in the shape of an outer frame.

In addition, an empty gap is formed between the cavity block and the front part, and a region extending downward from the receiving space of the cavity block may be the empty gap. The gap acts as a discharge part, and since the discharge part is formed between the cavity block and the front part, the fluid accommodated in the cavity block can be discharged with a predetermined width through the discharge part.

The discharge part is formed as an opening having a length as long as the length of the substrate, and the fluid may flow out with a constant width through the opening.

As the fluid is discharged with a constant width, the upper surface of the fluid may be supplied in contact with the discharging end of the blade.

In general, when the fluid is supplied to the substrate without a blade, the micro LED is not aligned with the groove because it is impossible to control the amount and supply speed of the fluid.

In the present invention, the micro LED (ML) is sequentially coupled to the groove of the substrate by moving the tip of the fluid generated by the difference in surface energy at the triple point where the fluid, the substrate, and air meet by using the blade 40 in one direction. This has the effect of accurately aligning one micro LED (ML) in one groove.

In addition, the micro LED (ML) can be completely fixed in the groove as the liquid evaporates at the tip of the fluid, which is a triple point.

When the fluid is supplied onto the substrate 10 , the micro LED (ML) moves to the interface between the substrate surface and the fluid, so that the concentration of the micro LED at the interface becomes higher than the concentration of the micro LED around the interface.

Specifically, the solvent at the interface evaporates, and as the solvent evaporates, the micro LED also moves, so that the concentration of the micro LED at the interface decreases.

And the micro LED is diffused in the interface direction by the concentration difference.

Accordingly, the microLED concentration at the interface is higher than the microLED concentration around the interface. If the microLED concentration at the interface is high, the probability of the microLED being constrained in the groove increases, and since self-alignment is possible in a non-contact method, it is possible to align a large area while minimizing damage to the microLED.

It is preferable to continuously supply the fluid including the micro LED (ML) on the substrate 10 in a uniform amount.

As the fluid is continuously supplied in a uniform amount, there is an effect of self-aligning the micro LEDs on the large-area substrate 10 . Accordingly, there is an effect of minimizing damage to the micro LED (ML) and improving the yield when aligning wafer units in large quantities.

In addition, when the fluid is continuously supplied, there is an advantage that it is possible to arrange the micro LEDs corresponding to the R-G-B colors at once.

On the other hand, when the fluid is supplied discontinuously in a non-uniform amount, the concentration of the microLED at the interface becomes spatially non-uniform when the fluid is supplied, so there is a problem in that the probability of alignment in the groove and the accuracy of the position are lowered. .

3 and 4, when the fluid is supplied on the substrate 10, an electric signal is applied to the first electrode layer and the second electrode layer spaced apart on the substrate 10 to form the first electrode layer and An electric field may be generated between the second electrode layers.

A direct current signal, an alternating current signal, or a pulsed DC signal of alternating current and direct current may be supplied to the first electrode layer and the second electrode layer.

When an electric field is generated around the electrode layer, attractive force acts between the electrode layer and the micro LED (ML), and a repulsive force acts between the micro LED (ML).

When a relatively high electric field is formed in the electrode layer, the micro LED (ML) contained in the fluid can be floated directly on the groove by strong attractive force, thereby further improving the alignment efficiency and securing the alignment position accuracy.

Accordingly, if the electric field is additionally generated when the fluid is supplied on the substrate, the alignment efficiency of the micro LED with respect to an accurate position can be further improved.

On the other hand, since the fluid-based micro LED alignment method of the present invention does not require a guide plate spaced apart from the upper direction of the substrate, there is no limitation in the shape of the substrate, and the alignment method of the micro LED is easy.

In addition, since the present invention is not affected by the structural limitations of the plate on the substrate, there is an advantage in that the degree of integration of the device is improved and the micro LED alignment on the large-area substrate is easy.

If a plate serving as a guide is installed on the substrate, there is a disadvantage in that it is necessary to make a precise plate and increase the size of the plate at the same time.

In addition, since the internal space is reduced by the location of the barrier rib called the plate on the substrate, there is a problem in that the number of grooves in which the micro LEDs are aligned is reduced.

Accordingly, it is preferable to align the micro LED in the groove using a blade that drags the fluid in one direction as in the present invention.

As described above, the present invention has been described with reference to the illustrated drawings, but the present invention is not limited by the embodiments and drawings disclosed in the present specification. It is obvious that variations can be made. In addition, although the effects according to the configuration of the present invention are not explicitly described and described while describing the embodiments of the present invention, it is natural that the effects predictable by the configuration should also be recognized.

Micro LED: ML
Substrate: 10
Electrode layer: 20
First electrode layer: 22
Second electrode layer: 24
Insulation layer: 30
Blade: 40

Claims (7)

(a) providing a substrate on which a groove is formed and a fluid including a micro LED;
(b) supplying a fluid including the micro LED onto a substrate in which a groove is formed; and
(c) aligning the micro LED with the groove;
A fluid-based micro LED alignment method in which the fluid including the micro LED is supplied to the blade in a contact state in the step (b), and the fluid including the micro LED is moved in one direction along the substrate surface.
According to claim 1,
The blade includes a cavity block receiving a fluid therein and an outlet for discharging the fluid,
A fluid-based micro LED alignment method in which the fluid accommodated in the blade is discharged through the discharge unit, and the fluid is supplied in contact with the discharging end of the blade.
According to claim 1,
The substrate on which the groove is formed is a fluid-based micro LED alignment method in which an electrode layer is disposed in the groove.
According to claim 1,
In the step (b), as the micro LED moves to the interface between the substrate surface and the fluid, the micro LED concentration at the interface is higher than the micro LED concentration around the interface.
According to claim 1,
A fluid-based micro LED alignment method for fixing the micro LED to the groove while the liquid evaporates at the end of the fluid containing the micro LED in step (c).
According to claim 1,
A fluid-based micro LED alignment method for generating an electric field by applying an electric signal to the first electrode layer and the second electrode layer spaced apart on the substrate in step (b).
According to claim 1,
A fluid-based micro LED alignment method for continuously supplying a fluid containing micro LEDs in step (b).

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