KR20240067493A - Apparatus for inspecting defect of self-light emitting diode using non-contact electroluminescence - Google Patents

Abstract

The present invention relates to a defect inspection device for a self-luminous device using non-contact electroluminescence. The defect inspection device for a self-luminous device using non-contact electroluminescence according to the present invention is a device for inspecting defects in a self-luminous device mounted on a board. A defect detection unit that detects defects by receiving light emitted from the self-luminous element, a coil unit in which a plurality of coils are spaced apart from each other with the self-luminous element at the center, and a power supply unit that applies current to the coil unit. It is characterized in that, when current is applied to the coil portion, an induced electric field is formed at the p-n junction portion of the self-light emitting device, thereby causing electric field emission of light from the self-light emitting device.

Description

Defect inspection device for self-luminous devices using non-contact electroluminescence {APPARATUS FOR INSPECTING DEFECT OF SELF-LIGHT EMITTING DIODE USING NON-CONTACT ELECTROLUMINESCENCE}

The present invention relates to a defect inspection device for self-light emitting devices using non-contact electroluminescence, and more specifically, to generate electroluminescence in a non-contact manner by generating an induced current in a self-light emitting diode such as OLED or micro LED. The present invention relates to a defect inspection device for a self-luminous device using non-contact electroluminescence, which can detect defects in a self-luminous device.

A light emitting diode (LED) is a semiconductor device that generates light when a voltage is applied in the forward direction.

When a positive (+) voltage is applied to the P-type semiconductor that makes up the light emitting diode and a negative (-) voltage is applied to the N-type semiconductor, holes and electrons move near the junction surface of the P-type semiconductor and N-type semiconductor, respectively. When holes and electrons combine and transition from the excited state to the ground state, energy corresponding to the band gap is emitted as light, a photon.

This phenomenon is called electroluminescence (EL), and LEDs can emit light by photoluminescence (PL) rather than electroluminescence. Photoluminescence is a phenomenon in which, when light with energy above the band gap is supplied to an LED, the LED absorbs photons and is then excited to emit light.

Recently, micro LEDs, which reduce the horizontal and vertical lengths of light-emitting diodes to less than 100 μm each, have been developed and are in the spotlight. Micro LED has a small chip size and can have a very thin thickness of less than 10 μm, so it can be easily applied to flexible devices and is superior to existing display devices in terms of resolution, power consumption, display thickness, and contrast ratio. It is known to have good performance compared to .

However, defects such as scratches, line defects, electrode contamination and peeling, and separation of micro LED chips may occur during the manufacturing process. In the case of micro LED, there are many defective elements that must be managed in each manufacturing process, so defects can be detected at each process step. It is important to test accurately and quickly.

PL (Photoluminescence) technology and EL (Electro Luminescence) technology are known methods for inspecting defects in self-luminous devices.

PL technology is an inspection method that utilizes the photoluminescence phenomenon by irradiating light to a self-luminous device. It has the advantage of fast inspection speed, but has the disadvantage of lower accuracy compared to EL technology.

As an example of field emission technology, a method of connecting an external power source directly to the cathode and anode of a self-luminous device is known. This has the advantage of being able to simultaneously measure the presence or absence of p-n junction and ohmic junction defects of a self-luminous device. However, as the number of display pixels increases and the size of self-light-emitting devices decreases, it is difficult to connect power to each self-light-emitting device and inspect for defects. Therefore, an inspection technology using non-contact electric field emission that enables high-speed and large-area inspection is required.

Figure 1 is a schematic diagram of a conventional inspection device for a self-luminous device using non-contact field emission.

In Figure 1, in order to implement large-area non-contact field emission, a transparent electrode (ITO) 10 module with an insulating layer 20 is placed above and below the p-n junction of a self-light emitting device (μLED) mounted on a substrate, and the transparent electrode is placed. Apply high frequency to (10). When the module generates an external electric field suitable for the diffusion speed of electrons and holes in the p-n junction, a current flows in the p-n junction due to the induced electric field, and the self-luminous device can emit light. At this time, the presence or absence of defects in the joint can be inspected by receiving and analyzing the light emission signal.

In this capacitor-type induced electric field generation method, the strength of the electric field can be determined by the vertical thickness and dielectric constant of the transparent electrode to which the high-frequency voltage is applied. Gallium nitride (GaN, ε _r = 8.9) and gallium arsenide (GaAs, ε _r = 12.9), which are generally used in self-luminous devices, have a higher dielectric constant than atmospheric air (ε _r = 1.004). The pn junction thickness in a self-luminous device is about 4㎛, and a voltage of 2~3 V is usually required for lighting. Therefore, when applying an electric field using the capacitor method of FIG. 1, an electric field of 500 to 750 V/mm needs to be applied to the pn junction area of the self-luminous device. The size of the required electric field may vary depending on the thickness of the pn junction, type of material, band gap, etc.

When an induced electric field is applied to a self-light-emitting device to be inspected through a capacitor method including the insulating layer 20, a waiting space is created in the area between the self-light-emitting devices or between the insulating layer 20 and the self-light-emitting device. When an electric field of 500 to 750 V/mm is applied to the p-n junction area, a dielectric breakdown electric field (3 kV/mm) or more may be applied to the atmosphere due to the dielectric constant difference between the p-n junction layer and the atmosphere, and thus a local arc may occur. This may cause damage to the self-luminous device during inspection.

Republic of Korea Patent No. 10-2286322

Therefore, the purpose of the present invention is to solve such conventional problems. By placing the self-light emitting device, which is the subject, at the center and disposing a plurality of coils at a distance from each other, the induced electric field is concentrated in the local area of the p-n junction, thereby causing localized arcing. The aim is to provide a defect inspection device for self-light-emitting devices using non-contact electroluminescence, which can prevent damage to light-emitting devices and apply a uniform induced electric field.

The problems to be solved by the present invention are not limited to the problems mentioned above, and other problems not mentioned will be clearly understood by those skilled in the art from the description below.

The above object is to provide, according to the present invention, an apparatus for inspecting defects in a self-light-emitting device mounted on a substrate, comprising: a defect detection unit that detects a defect by receiving light emitted by a field from the self-light-emitting device; a coil unit in which a plurality of coils are spaced apart from each other with the self-luminous element at the center; and a power supply unit that applies current to the coil unit, and when current is applied to the coil unit, an induced electric field is formed at a p-n junction of the self-luminous element, thereby causing electric field emission of light from the self-luminous element. This can be achieved by a defect inspection device for self-luminous devices using non-contact electroluminescence.

Here, the coil unit may be disposed on the upper or lower side of the substrate.

Here, the central axis of the coil may be formed in a circumferential direction with the self-luminous element at the center.

Here, each of the plurality of coils may be formed by being wound around a rod-shaped magnetic flux focusing unit.

Here, the coil unit may be formed by being wound around a ring-shaped magnetic flux focusing unit.

Here, the magnetic flux focusing part may be formed of a magnetic material.

Here, the coil unit may be arranged in multiple layers on the upper or lower side of the substrate.

Here, the diameter of the coil may be different depending on the layer location.

Here, when the coil unit is disposed on the lower side of the substrate, it may further include an electric field concentration part that is formed of a magnetic material and is disposed in the center of the plurality of coils perpendicular to the self-luminous device to concentrate the induced electric field.

According to the defect inspection device for a self-luminous device using non-contact electroluminescence of the present invention as described above, the induced electric field generated from a plurality of coils can be accumulated to improve the uniformity of the induced electric field at the p-n junction of the self-luminous device.

In addition, the intensity of the current applied to each coil can be reduced and the induced electric field can be concentrated at the p-n junction of the self-luminous device, thereby reducing the intensity of the induced electric field formed in areas other than the self-luminous device, resulting in local arcing. It also has the advantage of being able to suppress.

In addition, there is an advantage that defect inspection of self-light-emitting devices can be performed quickly and non-contactly while moving the coil unit or moving the substrate.

Figure 1 is a schematic diagram of a conventional inspection device for a self-luminous device using non-contact field emission.
Figure 2 is a diagram showing a defect inspection device for a self-luminous device using non-contact electroluminescence according to a first embodiment of the present invention.
Figure 3 is a diagram showing an example of a coil unit.
Figure 4 is a diagram showing another example of a coil unit.
Figure 5 is a diagram showing the coil arrangement of a defect inspection device for a self-luminous device using non-contact electroluminescence according to a second embodiment of the present invention.
FIG. 6 shows the results of simulating the electric field intensity around the area to be inspected when using a defect inspection device for a self-luminous device using non-contact electroluminescence having the same structure as that of FIG. 5.
Figure 7 is a diagram showing the coil arrangement of a defect inspection device for a self-luminous device using non-contact electroluminescence according to a third embodiment of the present invention.
Figure 8 is a diagram showing the coil arrangement of a defect inspection device for a self-luminous device using non-contact electroluminescence according to a fourth embodiment of the present invention.

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

The advantages and features of the present invention 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 may be implemented in various different forms. The present embodiments are merely provided to ensure that the disclosure of the present invention is complete and to be understood by those skilled in the art in the technical field to which the present invention pertains. 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. Like reference numerals refer to like elements throughout the specification.

Hereinafter, the present invention will be described with reference to the drawings for explaining a defect inspection device for a self-luminous device using non-contact electroluminescence according to embodiments of the present invention.

FIG. 2 is a diagram showing a defect inspection device for a self-luminous device using non-contact electroluminescence according to a first embodiment of the present invention, FIG. 3 is a diagram showing an example of a coil unit, and FIG. 4 is a diagram showing an example of a coil unit. It is a drawing showing another example, and FIG. 5 is a drawing showing the coil arrangement of a defect inspection device for a self-luminous device using non-contact electroluminescence according to a second embodiment of the present invention, and FIG. 6 has the same structure as FIG. 5. 7 shows the results of simulating the electric field intensity around the inspection object area when using a defect inspection device for a self-luminous device using non-contact electroluminescence, and FIG. It is a diagram showing the coil arrangement of a defect inspection device for a self-luminous device, and FIG. 8 is a diagram showing the coil layout of a defect inspection device for a self-luminous device using non-contact electroluminescence according to a fourth embodiment of the present invention.

A defect inspection device for a self-luminous device using non-contact electroluminescence according to an embodiment of the present invention may include a defect detection unit 200, a coil unit 100, and a power unit (not shown).

The defect detection unit 200 generates electric field-emitted light by flowing current in the p-n junction of a self-light-emitting device (e.g., micro LED (μLED)) by an induced electric field generated when a current is applied to the coil unit 100. Detects defects by receiving light.

The defect detection unit 200 may include a microscope that receives light emitted from a self-luminous device and a computer device that analyzes the light received from the microscope to determine whether there is a defect.

The coil unit 100 is disposed around the self-light emitting device mounted on the substrate S and generates an induced electric field in a vertical direction in the p-n junction region of the self-light emitting device when a current flows in the coil. At this time, in the present invention, the coil unit 100 may be formed by placing a self-luminous element at the center and spaced apart a plurality of coils, as shown.

When a coil is formed in the entire circumferential direction in a ring shape like a toroidal coil, the induced magnetic field is concentrated inside the coil and no induced electric field is generated at the center of the ring. However, as in the present invention, when a plurality of coils are spaced apart along the circumferential direction with the self-luminous element at the center, the magnetic field inside each coil leaks through the spaced portion, creating an induced electric field in the central area where the self-luminous element is located. It can occur.

As shown, the coil unit 100 may be arranged in a circumferential direction with the central axis of each coil having the self-luminous element at the center. In the present invention, the meaning that the central axes of the plurality of coils are arranged in the circumferential direction not only means that the coils are formed in the form of a plurality of coils forming an arc around the self-luminous element as shown in FIG. 4, but also in FIG. As shown in Figure 3, a plurality of coils can be interpreted as having a polygonal shape (square in Figure 3) surrounding a self-light emitting element at the center.

At this time, it is desirable to apply current to the coil in a direction in which an induced electric field is formed perpendicular to the p-n junction region.

A plurality of coils may be individually formed as shown in FIG. 3 and configured so that power is applied to each coil. Alternatively, as shown in FIG. 4, it may be formed in a form in which coils with concentrated coiling in the circumferential direction are spaced apart into one winding.

At this time, a magnetic flux focusing unit 120 may be disposed inside the coil. As shown in FIG. 3, a bar-shaped magnetic flux focusing part 120 may be disposed for each coil. That is, each coil may be formed by winding the outer periphery of each divided magnetic flux focusing unit 120. At this time, the magnetic flux focusing unit 120 may be a cylindrical bar, but is not necessarily limited thereto.

Alternatively, as shown in FIG. 4, a plurality of coils can be formed by winding a winding around the outer peripheral surface of the ring-shaped magnetic flux focusing part 120.

The magnetic flux focusing portion 120 is preferably formed of a magnetic material such as ferrite. As the magnetic flux focusing unit 120 is disposed within the coil, the intensity and distribution density of the induced magnetic force and dielectric electric field can be increased.

The power supply unit applies current to the coil.

In this way, when current is applied to the coil by the power supply, the induced magnetic field may leak from the spaced area between the coils, and an induced electric field may be formed in a direction perpendicular to the center of the coil as the magnetic field changes. By arranging a self-light-emitting device at the center of the plurality of coils where the induced electric field is formed, the current in the p-n junction can flow and emit light due to the induced electric field applied to the self-light-emitting device.

The above-described microscope is placed on top of the self-luminous device to receive light and inspect the self-luminous device for defects.

At this time, the coil unit 100 may be disposed on the upper side of the substrate S with the self-luminous element at the center, as shown in FIG. 2. Alternatively, the coil unit 100 may be disposed on the lower side of the substrate S with the self-light emitting device at the center. Alternatively, as shown in FIG. 5, the coil units 100a and 100b may be disposed on both the upper and lower sides of the substrate S with the self-luminous element at the center.

Let us assume that an induced electric field is formed in a self-luminous device using one of the four coils shown in FIG. 3. The intensity of the induced electric field decreases in proportion to the square of the distance from the coil. Therefore, in order to generate an induced electric field with a strength that causes electroluminescence in the self-luminous device, a larger current must be applied to the coil compared to the case of FIG. 3. As the intensity of the current applied to the coil increases, a high induced electric field is formed around the self-light-emitting device, which may generate sparks in the self-light-emitting device.

However, in the present invention, a plurality of coils are arranged with the self-luminous element at the center. The induced electric field generated from each coil can be accumulated at the center where the self-luminous element is placed. By causing the self-luminous device to emit electroluminescence due to the accumulated induced electric field, the intensity of the current applied to each coil can be reduced.

Therefore, the induced electric field can be concentrated at the p-n junction of the self-light emitting device, and a weak induced electric field is formed around the outside of the self-light emitting device to prevent local arcing.

FIG. 5 shows a case where the coil unit 100 is formed on the upper and lower sides of the substrate S, respectively. When the coil portions 100a and 100b are formed on the upper and lower sides of the substrate S, the vertically induced electric field component accumulated at the p-n junction portion of the self-luminous device may increase, so the intensity of the current applied to each coil can be further weakened, and the uniformity of the induced electric field at the p-n junction of the self-luminous device can be controlled more precisely.

At this time, when the coil unit 100 is disposed below the substrate S, the substrate S is preferably made of a material other than a metal material that shields the induced electric field.

FIG. 6 shows the results of simulating the intensity of the induced electric field generated in the central region of the plurality of coils where the self-luminous elements are located after forming the coil portion 100 on the upper and lower sides of the substrate S as shown in FIG. 5. Since the induced electric field can be accumulated by a plurality of coils, it can be determined through computational analysis that the induced electric field can be concentrated in the central area where the self-luminous device is placed.

As shown in FIG. 7, the coil units 100a and 100c may be formed in multiple layers. In this way, the uniformity of the intensity of the induced electric field at the p-n junction of the self-light emitting device can be improved by overlapping the coil parts 100a and 100c in multiple layers.

At this time, the drawing shows that the coil portions 100a and 100c are formed in multiple layers on the upper side of the substrate S, but the coil portion 100 may also be formed in multilayers on the lower side of the substrate S.

At this time, as shown, the coil diameter of each layer may be different. Additionally, the horizontal distance between the self-luminous element and the coil of each layer may be different.

As shown in FIG. 8, when the coil portion 100b is disposed on the lower side of the substrate S, the electric field concentration portion 150 formed of a magnetic material is positioned vertically below the self-light emitting device of the substrate S, the lower coil portion 100b. ) can be placed in the center of a plurality of coils. In this way, as the electric field concentrator 150 is disposed on the lower side of the substrate S, the induced electric field can be further concentrated in the local area where the self-light emitting device is located, thereby improving the induced electric field uniformity and surrounding the self-light emitting device. Local arcing can be prevented by applying a high induced electric field.

The scope of the present invention is not limited to the above-described embodiments, but may be implemented in various forms of embodiments within the scope of the appended claims. It is considered to be within the scope of the claims of the present invention to the extent that anyone skilled in the art can make modifications without departing from the gist of the invention as claimed in the claims.

100: Coil part
120: magnetic flux focusing unit
150: Electric field concentration part
200: defect detection unit
S: substrate

Claims (9)

In a device for inspecting defects in a self-luminous device mounted on a board,
a defect detection unit that detects defects by receiving light emitted from the self-luminous device;
a coil unit in which a plurality of coils are spaced apart from each other with the self-luminous element at the center; and
It includes a power supply unit that applies current to the coil unit,
A defect inspection device for a self-light-emitting device using non-contact electroluminescence, characterized in that when current is applied to the coil portion, an induced electric field is formed at the pn junction of the self-light-emitting device, thereby field-emitting light from the self-light-emitting device. According to claim 1,
A defect inspection device for a self-luminous device using non-contact electroluminescence, wherein the coil unit is disposed on the upper or lower side of the substrate. According to claim 2,
A defect inspection device for a self-light-emitting device using non-contact electroluminescence, wherein the central axis of the coil is formed in a circumferential direction with the self-light-emitting device at the center. According to claim 1,
A defect inspection device for a self-luminous device using non-contact electroluminescence, wherein each of the plurality of coils is wound around a rod-shaped magnetic flux collection part. According to claim 1,
A defect inspection device for a self-luminous device using non-contact electroluminescence, wherein the coil unit is wound around a ring-shaped magnetic flux focusing unit. The method of claim 4 or 5,
A defect inspection device for a self-luminous device using non-contact electroluminescence wherein the magnetic flux focusing unit is formed of a magnetic material. According to claim 1,
A defect inspection device for a self-luminous device using non-contact electroluminescence, wherein the coil unit is arranged in multiple layers on the upper or lower side of the substrate. According to claim 7,
A defect inspection device for a self-luminous device using non-contact electroluminescence where the diameter of the coil is different depending on the layer location. According to claim 2,
When the coil unit is disposed on the lower side of the substrate, a self-luminous device using non-contact electroluminescence further includes an electric field concentration portion formed of a magnetic material and disposed in the center of the plurality of coils perpendicular to the self-luminous device to concentrate the induced electric field. defect inspection device.

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