DEVICE AND A METHOD FOR MANUFACTURING THE SAME

The present disclosure provides devices and method of manufacturing the devices. An example device includes a substrate, a first electrode on the substrate, a light-emitting element electrically connected to the first electrode by a first metal wiring, and a second electrode electrically connected to the light-emitting element. The first electrode and the light-emitting element are laterally separated from each other. The light-emitting element is connected to the first metal wiring at a side that faces the substrate.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of International Application No. PCT/CN2020/098457, filed on Jun. 28, 2020, the disclosure of which is hereby incorporated by reference in its entirety.

TECHNICAL FIELD

The present disclosure relates to a device and a method for manufacture the same. In particular, the present disclosure relates to a display and a method for manufacturing the same using micro-LED.

BACKGROUND ART

In various applications such as mobile phones, automatic display, AR, VR, monitor, TV, and large screen display, etc., high resolution, high brightness, wide viewing angle, and low power consumption, etc. are required, and the need for a display using micrometer-size LED (micro-LED) is increasing.

SUMMARY OF INVENTION

Technical Problem

However, one of the problems with a display, which uses a micro-LED, is a high assembly cost. Conventionally, since the LED has been connected one by one by using bonding processes such as a wire bonding and a flip-chip bonding, the manufacturing cost is high. Therefore, as the number of pixels increases, the manufacturing cost increases. For example, in the case of a 4K display, about 25,000,000 micro-LED are used. Even if the yield of the micro-LED is 99.99%, it is necessary to repair about 2500 micro-LED.

A gang-bonding method as shown inFIG.1is present as a method to reduce assembly costs. The gang-bonding method allows a plurality of micro-LED3to be bonded to a substrate 1 through the solder2at a time, by applying pressure to the plurality of micro-LED3by a bonding head4. However, since the thicknesses of the plurality of micro-LED3may vary, the thickness variation absorption film5is required for canceling the difference of thicknesses. Even if the thickness variation absorption film5is used, the variation in the thickness of the plurality of micro-LED3may not be completely cancelled. As a result, different stresses can be applied on the plurality of micro-LED3. In particular, since the red-light emitting micro-LED3can be fabricated from a fragile GaAs, it is easily destroyed by an excessive stress. Therefore, the production of devices using the gang-bonding method has a low yield.

Also, the larger the device’s area, the greater the variation of the stresses applied to the device. Moreover, the gang-bonding method has a small area that can be accurately bonded at one time, due to the limited size of the bonding head4. Therefore, it is difficult to manufacture large screen displays by the gang-bonding method.

In addition, manufacturers need to verify that the micro-LED in the device is operating normally during or after the manufacturing process. However, it is difficult to repair the micro-LED embedded in the device.

Therefore, there is a need for a display and a manufacturing method that have inexpensive manufacturing cost and high yields.

Solution To Problem

The first aspect of the present disclosure is a device comprising:a substrate;a first electrode on the substrate;a light-emitting element electrically connected to the first electrode by a first metal wiring; anda second electrode electrically connected to the light-emitting element,wherein the first electrode and the light-emitting element are laterally separated from each other, andwherein the light-emitting element is connected to the first metal wiring at the side which faces the substrate.

In the above aspect of the present disclosure, the device may further comprise a first aspect including the light-emitting element, wherein a thickness of the first dielectric layer may be greater than or equal to a thickness of the light-emitting element.

In the above aspect of the present disclosure, the first electrode may comprise a pad on the substrate, a first contact metal electrically connected to the pad, and wherein the first metal wiring may be electrically connected to the first contact metal.

In the above aspect of the present disclosure, the device may further comprise an adhesive layer on the substrate, wherein a thickness of the pad may be less than or equal to a thickness of the adhesive layer.

In the above aspect of the present disclosure, the device may further comprise a second dielectric layer on the first electrode, wherein at least one of the first dielectric layer and the dielectric layer may be made of a photosensitive transparent resin.

In the above aspect of the present disclosure, the device may comprise a plurality of the light-emitting elements having different thicknesses.

In the above aspect of the present disclosure, the light-emitting element may be a vertical type micro-LED.

In the above aspect of the present disclosure, the device may further comprise:a third electrode on the substrate;a repair light-emitting element electrically coupled to the third electrode; anda fourth electrode electrically connected to the repair light-emitting element,wherein the repair light-emitting element may cover at least a portion of the third electrode.

In the above aspect of the present disclosure, the second electrode and the fourth electrode may be common electrodes.

In the above aspect of the present disclosure, the second electrode and the fourth electrode may be transparent electrodes.

A second aspect of the present disclosure is a method of manufacturing a device, comprising:a step of arranging a light-emitting element on a carrier;a step of forming a first dielectric layer on the carrier so that the light-emitting element is exposed;a step of forming a metal wiring on the light-emitting element and the first dielectric layer;a step of forming an adhesive layer on a substrate having a pad;a step of bonding the carrier and the substrate,wherein the metal wiring on the carrier faces the pad and the adhesive layer on the substrate, andwherein the light-emitting element and the pad are laterally separated from each other;a step of removing the carrier;a step of etching the first dielectric layer and the adhesive layer until reaching the pad to form an opening;a step of depositing a contact metal on the opening so that the pad and the metal wiring are electrically connected each other;a step of forming a second dielectric layer on at least the first dielectric layer so that the light-emitting element is exposed; anda step of forming an electrode on the light-emitting element.

In the above aspect of the present disclosure, the light-emitting element may be a vertical type micro-LED.

In the above aspect of the present disclosure, a thickness of the first dielectric layer may be greater than or equal to a thickness of the light-emitting element.

In the above aspect of the present disclosure, the light-emitting element may comprise a plurality of light-emitting elements having different thicknesses.

In the above aspect of the present disclosure, a thickness of the pad may be less than or equal to a thickness of the adhesive layer.

In the above aspect of the present disclosure, the step of arranging a light-emitting element on the carrier may comprise a step of transferring the light-emitting element provided on a spare substrate to a spare carrier, and a step of transferring the light-emitting element transferred to the spare carrier, to the carrier.

In the above aspect of the present disclosure, the electrode may be a common electrode.

In the above aspect of the present disclosure, the electrode may be a transparent electrode.

In the above aspect of the present disclosure, at least one of the first dielectric layer and the dielectric layer may be made of a photosensitive transparent resin.

In the above aspect of the present disclosure, the method may comprise:prior to the step of forming the second dielectric layer, a step of testing an operation of the light-emitting element;when the light-emitting element does not operate, a step of cutting the metal wiring connected to the non-operating light-emitting element; anda step of arranging a repair light-emitting element on a contact metal connected to the cut metal wiring.

In the above aspect of the present disclosure, the step of testing an operation of the light-emitting element may comprise a step of electrically connecting a test carrier having a conductive layer to the light-emitting element.

In the above aspect of the present disclosure, the step of arranging a repair light-emitting element on the contact metal may comprise a step of bonding using solder.

In the above aspect of the present disclosure, the step of forming a second dielectric layer on at least the first dielectric layer may comprise a step of forming the second dielectric layer on the opening so that the repair light-emitting element is exposed, and the steep of forming an electrode on the light-emitting element comprises a step of forming the electrode on the repair light-emitting element.

Advantageous Effects Of Invention

Since the present disclosure uses the wiring process which is a mature technology, it can provide a display and a manufacturing method that have inexpensive manufacturing cost and high yields.

DESCRIPTION OF EMBODIMENTS

Hereinafter, the embodiment of the present disclosure will be described in detail with reference to the accompanying drawings. Although the following detailed description describes the display where the micro-LED is used, the present disclosure is applicable to an edge-emitting laser, an optical communication device using a VCSEL (vertical-resonant surface-emitting laser), a ToF module (image sensor), a laser printer, and the like.

FIG.2shows a device100according to the present disclosure.

The device100of the present disclosure may include a substrate10; a first electrode20which includes a pad22on the substrate10, and a contact metal24electrically connected to the pad22; an adhesive layer26; a first dielectric layer36; a light-emitting element30which has an upper electrode34at the opposite side of the substrate10and a lower electrode32at the side which faces the substrate10; a metal wiring28one end of which is electrically connected to the contact metal24and the other end of which is electrically connected to the lower electrode32of the light-emitting element30; a second dielectric layer40; and a second electrode42electrically connected to the upper electrode34of the light-emitting element30. The metal wiring28electrically connects the first electrode20and the light-emitting element30. The metal wiring28extends laterally from the contact metal24toward the light-emitting element30. Also, the first electrode20and the light-emitting element30are laterally separated from each other. Herein, the term of “laterally” refers to a direction parallel to the surface of the substrate10. For example, a plurality of components being laterally separated means that each component does not overlap in the top view. A plurality of components being laterally separated does not limit that each component is present in the same plane.

The device100of the present disclosure is manufactured by the mature wiring method without using a bonding method that applies a high pressure. Therefore, the yield of the manufactured device is improved compared to the process using the bonding which is highly likely to break the light-emitting element30, and the manufacture of the large-size device is facilitated.

In addition, the device100of the present disclosure may further comprise a repair light-emitting element50. The repair light-emitting element50is electrically connected to the contact metal24via the lower electrode52and the solder56, and may be electrically connected to the second electrode42via the upper electrode54thereof.

Furthermore, the device100of the present disclosure may include a NG emitting element60that does not operate normally. The NG light-emitting element60may be electrically connected to a cut metal wiring58at lower electrode62thereof, and may be electrically connected to the second electrode42at the upper electrode64thereof. Because the metal wiring is cut, no voltage is applied for the NG light-emitting element60between the first electrode20and the second electrode42.

The method of manufacturing the device100of the present disclosure will be described.

FIG.3shows a step of transferring the light-emitting element30provided on the spare substrate12to the spare carrier14. The spare carrier14may have a first adhesive13. The spare substrate12is brought close to the spare carrier14, so that the light-emitting element30on the spare substrate12comes into contact with the first adhesive13on the spare carrier14. Thereafter, the light-emitting element30is removed from the spare substrate12, for example with a laser lift off (LLO) using a laser15, and is transferred on the spare carrier14.

The spare substrate12may be a substrate commonly used in the art. For example, the spare substrate12may be a sapphire substrate, a gallium nitride substrate, or the like.

The light-emitting element30may be a plurality of light-emitting elements, for example a red light-emitting element, a green light-emitting element, and a blue light-emitting element. The plurality of light-emitting elements may have different thicknesses. Since the device100of the present disclosure may comprise light-emitting elements having different thicknesses, a multi-color display can be provided.

The light-emitting element30may be a light-emitting diode (LED). The LED may be a micro-LED. The micro-LED refers to an LED having a footprint of less than about 50 µm × 50 µm, preferably less than 20 µm × 20 µm or less, and more preferably less than about 10 µm × 10 µm. The micro-LED can be a vertical type micro-LED. The vertical type micro-LED refers to an LED having the upper electrode34and the lower electrode32. Since the vertical type micro-LED with the electrodes in the vertical direction can be smaller in footprint, the higher pixel per inches (PPI) can be achieved.

At least one electrode of the vertical type micro-LED face the substrate10. Therefore, in the conventional technology, the electrode which faces the substrate is electrically connected to the pad on the substrate, by bonding method using solder or the like. In the bonding method, it is difficult to connect the micro-LED and the substrate accurately at a time. In contrast, the metal wiring28which uses the wiring method can electrically connect to the micro-LED30 and the pad22in the present disclosure.

The first adhesive13may be an adhesive commonly used in the art. For example, the first adhesive13may be a thermoset adhesive such as epoxy, acrylic, or silicone-based adhesive, or a UV-curable adhesive.

The pad22may be a pad commonly used in the art. For example, the pad22may be titanium, nickel, chromium, gold, copper, or an alloy thereof.

The laser15may be a laser commonly used in the art. For example, the laser15may be a UV laser emitting a wavelength of 200-400 nm, a green-emitting laser, or a near-infrared laser emitting a wavelength of 800-1,000 nm.

FIG.4shows a step of transferring the light-emitting element30which is transferred to the spare carrier14, to the carrier18. The carrier18may have a second adhesive17. The spare carrier14is brought close to the carrier18so that the light-emitting element30on the spare carrier14comes into contact with the second adhesive17on the carrier18. Then, the light-emitting element30is removed from the spare carrier14, for example by utilizing the difference of adhesion force between the first adhesive13on the spare carrier14and the second adhesive17on the carrier18, and the light-emitting element30is transferred on the carrier18. In this case, the adhesion force of the second adhesive17on the carrier18is greater than the adhesion force of the first adhesive13on the spare carrier14.

As shown in the top view in the lower-right ofFIG.4, the plurality of light-emitting elements30may be accurately placed on a predetermined location on the carrier18.

The carrier18may be a carrier commonly used in the field. For example, the carrier18may be a carrier made of quartz or glass. The spare carrier14and the carrier18may be made of the same material or different materials.

The second adhesive17may be an adhesive commonly used in the art. For example, the second adhesive17may be a thermoset adhesive such as epoxy, acrylic, or silicone-based adhesive, or a UV-curable adhesive. The first adhesive13and the second adhesive17may be made of the same material or different materials.

InFIGS.5to14below, the top view and the cross-sectional views along A-A′, B-B′, and C-C′ in the top view of the embodiment of the present disclosure are shown.

FIG.5shows a step of forming a first dielectric layer36on the carrier18so that the light-emitting element30is exposed, and forming a metal wiring28on the light-emitting element30and the first dielectric layer36. As shown in the A-A′ section, the first dielectric layer36is formed on the carrier18. The first dielectric layer36includes a light-emitting element30. The first dielectric layer36has a via in which the electrode32of the light-emitting element30is exposed. Thereafter, the metal wiring28is formed on the first dielectric layer36and in the via, and one end of the metal wiring28is electrically connected to the light-emitting element30.

The metal wiring28is formed, for example by lithography using a photoresist. A metal layer is deposited on the first dielectric layer36and in the via, and the photoresist is patterned on the metal layer. Thereafter, the metal layer is patterned by etching along the photoresist pattern. Thereafter, the photoresist is removed to form the metal wiring28.

The first dielectric layer36may include a photosensitive material, or a non-photosensitive material such as thermoset material. Preferably, the first dielectric layer36may include a photosensitive material. More preferably, the first dielectric layer36may include a photosensitive resin. If the first dielectric layer36includes a photosensitive resin, the formation of the via by lithography is easy. Also, the flexibility of the device can be increased, enabling the production of large size devices.

The metal wiring28may be any conductive material including metal, and may be any conductive metal or conductive metal oxide. Preferably, the metal wiring28may be one or more selected from the group consisting of copper, nickel, titanium, chromium, and indium tin oxide (ITO).

The thickness of the first dielectric layer36may be greater than or equal to the thickness of the light-emitting element30. Since a portion of the light-emitting element30is covered by the first dielectric layer36, the mechanical strength of the device is increased. Therefore, the yield of the device can be improved, and enabling the manufacture of the large-size device.

Thereafter, a substrate10having a pad22is provided, and the adhesive layer26is formed on the substrate10.

FIG.6shows a step of bonding the carrier18and the substrate10. The metal wiring28on the carrier18may face the pad22and adhesive layer26on the substrate10. The metal wiring28can be accurately aligned with the pad22. The carrier18is brought close to the substrate10, the carrier18and the substrate10are bonded by the adhesive layer26so that the light-emitting element30and the pad22are laterally separated from each other. The pad22and the light-emitting element30are separated laterally and electrically connected by the metal wiring28.

The substrate10may be a substrate commonly used in the art. For example, the substrate10is, for example, a driving substrate in which a TFT is formed on a glass substrate.

The adhesive layer26may be a thermoset adhesive such as epoxy, acrylic, or silicone-based adhesive, or a UV-curable adhesive. Thus, the flexibility of the device can be increased, enabling the production of large size devices.

The thickness of pad22may be less than or equal to the thickness of adhesive layer26. Thus, since the metal wiring28does not come into contact with the pad22in the step of bonding the carrier18and the substrate10, the undesired stress does not occur. Therefore, the yield of the device can be improved, and enabling the manufacture of the large-size device.

FIG.7shows a step of removing the carrier18. The removal of the carrier18may be performed using known techniques in the art such as laser lift-off (LLO), mechanical removal, and the like. For example, a UV laser passing through the carrier18is irradiated to the second adhesive17, and the carrier18is peeled from the second adhesive17. Although not shown, the second adhesive17may be removed and the upper electrode34of the light-emitting element30may be exposed after the carrier18has been removed.

FIG.8shows a step of forming an opening38by etching the first dielectric layer36and the adhesive layer26until reaching the pad22. The metal wiring28may serve as a mask against etching. After etching, the pad22and the metal wiring28may be exposed at the opening38.

At this step, the pad22and the metal wiring28may not be electrically connected.

Etching may be performed using techniques known in the art. For example, etching may be performed by reactive ion etching, such as oxygen plasma etching.

FIG.9shows a step of depositing the contact metal24on the opening38, so that the pad22and the metal wiring28are electrically connected. The pad22and the contact metal24may constitute the first electrode20. Thus, the pad22and the light-emitting element30may be electrically connected via the contact metal24and the metal wiring28. The deposition of the contact metal24may be performed by sputtering, photoresist formation, and etching of metal layers, etc.

FIGS.10to12show from a step of testing the operation of the light-emitting element30to a step of arranging a repair light-emitting element50. These steps are any steps. These steps may be performed prior to a step of forming the second dielectric layer40.

FIG.10shows a step of testing the operation of the light-emitting element30. This step may include a step of electrically connecting a test carrier68having a conductive layer66to the light-emitting element30. The test carrier may be made of glass. The conductive layer66may be a conductive sheet having a low modulus of elasticity. Since the conductive layer66has a low modulus of elasticity, the conductive layer66and the upper electrode34of the light-emitting element30may be electrically connected by applying an appropriate pressure.

Thereafter, it is possible to test whether the light-emitting element30operates normally by applying a voltage between the pad22and the conductive layer66to induce the electroluminescence (EL) of the light-emitting element30. Instead of the EL, it is possible to test the operation of the light-emitting element30by using photoluminescence (PL). When the PL is used, it is possible to test whether the light-emitting element30operates normally by inducing PL in the light-emitting layer of the light-emitting element30by an excitation light such as ultraviolet light.

FIG.11shows a step of cutting the metal wiring28connected to the light-emitting element60which does not operate normally. If the light-emitting element30does not operate normally, for example, it does not emit light or the light emission intensity is less than a predetermined value, such light-emitting element30is referred to as the NG light-emitting element60. The metal wiring28connected to the NG light-emitting element60is cut, for example, by the laser70, and the NG light-emitting element60and the pad22loses electrical connection therebetween.

The laser70may be a laser commonly used in the art. For example, the laser70may be a UV laser emitting a wavelength of 200-400 nm, a green-emitting laser, a near-infrared laser emitting a wavelength of 800-1,000 nm, or a CO2laser emitting a wavelength near 10 microns.

FIG.12shows a step of arranging a repair light-emitting element50on the contact metal24connected to the cut metal wiring58. This step may comprise a step of bonding the lower electrode52of the repair light-emitting element50and the contact metal24using solder56. The repair light-emitting element50may be electrically connected to the first electrode20on the substrate10. The solder56may be formed on the lower electrode52of the repair light-emitting element50or on the contact metal24. The repair light-emitting element50may cover at least a portion of the first electrode20including the contact metal24and the pad22.

According to any of the steps shown inFIGS.10to12, the test of the operation of the light-emitting element30and the arrangement of the repair light-emitting element50are carried out. Thus, in the process of the present disclosure, the test and the repair of the light-emitting element30can be easily performed.

FIG.13shows a step of forming a second dielectric layer40on at least the first dielectric layer36, so that the light-emitting element30is exposed. Optionally, this step may comprise a step of forming the second dielectric layer40on at least the first dielectric layer36, so that the repair element50is exposed.

The second dielectric layer40may have a via in which the upper electrode34of the light-emitting element30is exposed. Optionally, the second dielectric layer40may have a via in which the upper electrode54of the repair element50is exposed.

Also, the second dielectric layer40may be formed on at least one of the substrate10, the pad22, the contact metal24, the adhesive layer26, and the metal wiring28, at the opening38. The second dielectric layer40may be formed on the first electrode20.

The second dielectric layer40may include a photosensitive material, or a non-photosensitive material such as thermoset material. Preferably, the first dielectric layer36may include a photosensitive material. More preferably, the first dielectric layer36may include a photosensitive resin. If the second dielectric layer40includes a photosensitive resin, the formation of the via by dry etching is easy. Also, the flexibility of the device can be increased, enabling the production of large size devices. The first dielectric layer36and the second dielectric layer40may be made of the same material or different materials.

FIG.14shows a step of forming a second electrode42on the light-emitting element30. The second electrode42may be electrically connected to the upper electrode34of the light-emitting element30. The second electrode42may be formed on the second dielectric layer40. The second electrode42may be a common electrode that is electrically connected to the plurality of light emitting devices30. Also, the second electrode42may be a transparent electrode.

Optionally, the step of forming the second electrode42on the light-emitting element30may comprise a step of forming the second electrode42on the repair light-emitting element50. The second electrode42may be electrically connected to the upper electrode54of the repair light-emitting element50. The second electrode42may be a common electrode that is electrically connected to the repair light-emitting element50and the light-emitting element30.

As described above, the device100of the present disclosure is manufactured. In the manufacturing process of the present disclosure, the metal wiring28is formed by the mature wiring method. Although a bonding method is used in the step of arranging the repair light-emitting element50on the contact metal24, no bonding method is used in other processes.

Accordingly, the present disclosure can provide a display using micro-LED and a manufacturing method the same, which have high yield and is applicable to a large screen, and, if necessary, is capable of the repair of the micro-LED.

DESCRIPTION OF SYMBOLS