Micro LED element

Abstract

The present invention provides a Micro LED element, one side of which is less than 100 [mu] m, the Micro LED element having: a light-emitting element structure in which an active layer comprising (AlyGa1-y) xIn1-xP (0.4 < = x < = 0.6, 0 < = y < = 0.5) is sandwiched between a first cladding layer and a second cladding layer; an upper electrode; and a lower electrode having a polarity different from that of the upper electrode, the Micro LED element being characterized in that in the Micro LED element, the light-emitting element structure, the upper electrode and the lower electrode are arranged on a first surface of the Micro LED element, the upper electrode is arranged on a top surface of the light-emitting element structure, and the lower electrode is arranged on a second surface of the Micro LED element. The lower electrode is disposed at a position where the light-emitting element structure is not present, and the Micro LED element has the light-emitting element structure so as to surround the periphery of the lower electrode. As a result, provided is a Micro LED element which has an AlGaInP-based light-emitting element structure and two electrodes having different polarities on the same surface, and which is capable of reducing or avoiding cracks in a Micro LED element (crystal grain) having a size of less than 100 [mu] m on one side.

Description

Technical Field

[0001] The present invention relates to a Micro LED element, and more particularly to a structure of a Micro LED element capable of reducing or avoiding cracking. Background Art

[0002] Patent Document 1 discloses a technique for realizing a Micro LED display. In order to achieve this, it uses laser lift-off (LLO) to peel the LED from the starting substrate, transfer it to the packaging substrate, and then transfer it to the driving substrate. However, all of these are only for GaN-based LEDs, and there is little disclosure of techniques related to Micro LEDs using AlGaInP-based LEDs.

[0003] In order to realize a Micro LED element using an AlGaInP-based LED through the LLO process, it is necessary to transfer it to a sapphire substrate. Regarding the technique of transferring an AlGaInP-based LED to a sapphire substrate, for example, there are disclosures of prior arts such as Patent Document 7.

[0004] However, compared with GaN-based LEDs, AlGaInP-based LEDs are mechanically more fragile and are prone to grain cracking during the LLO process depending on the appropriateness of the grain design. There is no disclosure of a technique related to avoiding Micro LED grain cracking during the LLO process. In particular, there is no disclosure of prior art related to grain design and cracking.

[0005] Patent Document 2 discloses a design in which a rectangular ohmic electrode is arranged at the end in the long side direction in a chip having a long side and a short side. Although it is a typical chip design, it does not consider grain cracking, and the lower electrode and the upper electrode are formed separately (in batches), so it is difficult to make the heights absolutely consistent. Due to the different heights, stress is applied to the area between the upper electrode and the lower electrode during LLO. When the mechanical strength of the pedestal part connecting the upper electrode domain and the lower electrode domain is weak, it will cause grain cracking. In the AlGaInP-based LED, the part corresponding to the pedestal is generally set to GaP having a high density of crystal dislocations, and the mechanical strength is extremely low.

[0006] Patent Document 3 discloses a structure in which the lower electrode is surrounded by a DH layer (light-emitting layer) in three directions. In this structure, since the lower electrode and the upper electrode are formed separately (in batches), it is difficult to make the heights absolutely consistent. Therefore, in the technique shown in Patent Document 3, grain cracking is as likely to occur as in the case of Patent Document 2. Therefore, the technique shown in Patent Document 3 is not a technique for improving the mechanical strength of grains.

[0007] As a technology similar to Patent Document 3, Patent Document 4 discloses a design in which the lower electrode has a long side and the upper electrode surrounds three sides of the lower electrode. However, one side of the lower electrode is not surrounded, and the lower electrode extends in the direction where it is not surrounded. Further, there is an opening in the upper part, and the element part of the opening part is thinner. Therefore, the mechanical strength of the lower electrode in the opening part becomes low. Generally, the sides of the grains are formed along the <100> direction as the cleavage direction, so it is a structure that is prone to cleavage. Therefore, the configuration of Patent Document 4 with one side not surrounded is not a suitable technology in terms of avoiding grain breakage.

[0008] Patent Document 5 discloses a design of a plurality of circular lower electrodes surrounded in GaN-based LEDs. On the other hand, in Micro LED elements, generally, one side of the grain is less than 100 μm, the long side of the lower electrode is about 50 μm or less, and the short side is mostly about half of it. If Patent Document 5 is to be applied to AlGaInP-based LEDs, it is necessary to remove the AlGaInP-based light-emitting layer with a thickness of about 2 - 3 μm to provide a plurality of electrodes. During the process of removing the AlGaInP-based light-emitting layer, the active layer will be exposed. Therefore, in order to prevent short circuits, it is necessary to form a passivation film on the processed cross-section. As a result, the area where Ohmic contact can be made will be smaller than the diameter of the opened hole. If it is not a Micro LED element but a grain with a size larger than that, the fact that the area of the contact electrode is smaller than the opening processing area will not be a big problem. However, for a micro-sized grain like a Micro LED element, the space efficiency is poor. In addition, in the prior art, the electrode part in contact with a plurality of lower electrodes is provided in another space, and this design also deteriorates the space efficiency. Although Patent Document 5 does not explicitly state the grain size, it is clearly not a technology suitable for designing grains as small as Micro LED elements.

[0009] Patent Document 6 discloses a structure in which the lower electrode is surrounded in two directions by a DH layer (light-emitting layer). The processing structure of the DH layer in Patent Document 6 is an example for improving luminance and interconnection and has a size of more than 100 μm on one side, and it is not a disclosure of a technology considering the breakage of Micro LED elements with a long side less than 100 μm.

[0010] As shown above, a technology for avoiding grain breakage during the LLO process in Micro LED elements having an AlGaInP-based material as the active layer has not been disclosed.

[0011] Prior art documents

[0012] Patent documents

[0013] Patent Document 1: Japanese Patent Application Laid-Open No. 2020-521181

[0014] Patent Document 2: Japanese Unexamined Patent Application Publication No. 2019-129299

[0015] Patent Document 3: Japanese Unexamined Patent Application Publication No. 2014-179590

[0016] Patent Document 4: Japanese Unexamined Patent Application Publication No. 2011-124248

[0017] Patent Document 5: Japanese Unexamined Patent Application Publication No. 2009-117796

[0018] Patent Document 6: WO2010 / 074288

[0019] Patent Document 7: Japanese Unexamined Patent Application Publication No. 2022-013203 Summary of the Invention

[0020] (1) Technical Problem to be Solved

[0021] In view of the above technical problems, the present invention aims to provide a Micro LED element capable of reducing or avoiding cracking of Micro LED elements (die), the Micro LED element having an AlGaInP-based light-emitting element structure and two electrodes with different polarities on the same surface and having a side length of less than 100 μm.

[0022] (2) Technical Solution

[0023] To achieve the above object, the present invention provides a Micro LED element having a side length of less than 100 μm, the Micro LED element comprising: a light-emitting element structure in which an active layer composed of (Al y Ga 1-y ) x In 1-x P is sandwiched between a first cladding layer and a second cladding layer, where 0.4 ≤ x ≤ 0.6 and 0 ≤ y ≤ 0.5; an upper electrode; and a lower electrode having a polarity different from that of the upper electrode, wherein the light-emitting element structure, the upper electrode, and the lower electrode are disposed on a first surface of the Micro LED element, the upper electrode is disposed on the top surface of the light-emitting element structure, the lower electrode is disposed at a position where the light-emitting element structure does not exist, and the Micro LED element has the light-emitting element structure so as to surround the periphery of the lower electrode.

[0024] In the structure of conventional Micro LED components, there is a height difference between the upper electrode and the lower electrode, which easily generates stress concentration points. However, in the Micro LED components of the present invention, by having a light-emitting element structure that surrounds the periphery of the lower electrode, the height difference around the upper electrode and the lower electrode can be reduced, and there is a light-emitting element structure at the part that should be the stress concentration point, making it less likely to cause a decrease in strength. Therefore, the frequency of grain cracking can be reduced.

[0025] In addition, it is preferable that the light-emitting element structure surrounding the periphery of the lower electrode continuously and uninterruptedly surrounds the periphery of the lower electrode, or has a partial notch, and the boundary part between the notch and the outside of the light-emitting element structure is located closer to the outside than the end of the lower electrode.

[0026] If the light-emitting element structure continuously and uninterruptedly surrounds the periphery of the lower electrode, there is no height difference around the lower electrode at all, and it is least likely to cause a decrease in strength. In addition, even if the light-emitting element structure has a partial notch, as long as the boundary part between the notch and the outside of the light-emitting element structure is located closer to the outside than the end of the lower electrode, it is also possible to sufficiently prevent a decrease in strength. By preventing a decrease in strength in this way, the frequency of grain cracking can be reduced.

[0027] In addition, it is preferable that a wafer transparent to the emission wavelength is bonded to the second surface of the Micro LED component using an adhesive or a bonding material.

[0028] When performing the LLO (laser lift-off) process in such a bonded wafer, although the conventional LLO is a process with a relatively high frequency of cracking, the present invention can reduce the frequency of grain cracking.

[0029] In addition, it is preferable that the adhesive or the bonding material is benzocyclobutene (BCB).

[0030] If such an adhesive or bonding material is used, it can be suitably applied to Micro LED components.

[0031] In addition, it is preferable that the transparent wafer is sapphire or quartz.

[0032] If such a transparent wafer is used, it can be suitably applied to Micro LED components.

[0033] (III) Beneficial effects

[0034] As described above, in the case of the Micro LED element of the present invention, by having a light-emitting element structure so as to surround the periphery of the lower electrode, the height difference between the upper electrode and the periphery of the lower electrode can be reduced, and the light-emitting element structure exists in the portion that should be the stress concentration point, so that a decrease in strength is not easily caused. Therefore, the frequency of grain cracking can be reduced. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 FIG. is a schematic cross-sectional view showing one process of a method for manufacturing a Micro LED element according to a first embodiment of the present invention.

[0036] Figure 2 FIG. is a schematic cross-sectional view showing one process of a method for manufacturing a Micro LED element according to a first embodiment of the present invention.

[0037] Figure 3 FIG. is a schematic cross-sectional view showing one process of a method for manufacturing a Micro LED element according to a first embodiment of the present invention.

[0038] Figure 4 FIG. is a schematic cross-sectional view showing one process of a method for manufacturing a Micro LED element according to a first embodiment of the present invention.

[0039] Figure 5 FIG. is a schematic cross-sectional view showing one process of a method for manufacturing a Micro LED element according to a first embodiment of the present invention.

[0040] Figure 6 FIG. is a schematic cross-sectional view showing one process of a method for manufacturing a Micro LED element according to a first embodiment of the present invention.

[0041] Figure 7 FIG. is a schematic cross-sectional view showing an example of a method for displacing a Micro LED element according to a first embodiment of the present invention.

[0042] Figure 8 FIG. is a top view of a Micro LED element according to a first embodiment of the present invention.

[0043] Figure 9 FIG. is a cross-sectional view of a Micro LED element according to a first embodiment of the present invention.

[0044] Figure 10 FIG. is a top view of a Micro LED element according to a second embodiment of the present invention.

[0045] Figure 11 FIG. is a cross-sectional view of a Micro LED element according to a second embodiment of the present invention.

[0046] Figure 12 is a cross-sectional view of a Micro LED element according to a second embodiment of the present invention.

[0047] Figure 13 is a cross-sectional view of a Micro LED element according to a second embodiment of the present invention.

[0048] Figure 14 FIG. 1 is a top view of another example of a Micro LED element according to the second embodiment of the present invention.

[0049] Figure 15 This is a top view of a previous Micro LED component.

[0050] Figure 16 This is a cross-sectional view of a conventional Micro LED component. DETAILED DESCRIPTION

[0051] As mentioned above, there is no known technology disclosed that can avoid grain cracking during the LLO process in a Micro LED element having an AlGaInP-based light-emitting element structure and two electrodes with different polarities on the same surface and a side less than 100 μm.

[0052] The inventors of the present application conducted further repeated research and found that in the above-mentioned Micro LED element, by having a light-emitting element structure in a manner surrounding the lower electrode, the height difference around the upper electrode and the lower electrode can be reduced, it is less likely to cause a decrease in strength, and the frequency of grain fracture can be reduced, thereby completing the present invention.

[0053] That is, the present invention is a Micro LED element, one side of which is less than 100 μm, and the Micro LED element has: a light emitting element structure, which is composed of (Al y Ga 1-y ) x In 1-x A light-emitting element structure in which an active layer composed of P (0.4≤x≤0.6, 0≤y≤0.5) is sandwiched between a first cladding layer and a second cladding layer; an upper electrode; and a lower electrode, whose polarity is different from that of the upper electrode, wherein the light-emitting element structure and the upper electrode and the lower electrode are arranged on the first surface of the Micro LED element, the upper electrode is arranged on the top surface of the light-emitting element structure, and the lower electrode is arranged at a position where the light-emitting element structure does not exist, and the Micro LED element has a light-emitting element structure in a manner surrounding the lower electrode. The lower limit value of one side of the Micro LED element is not particularly limited, and can be set to 1 μm or more, for example.

[0054] Hereinafter, the present invention will be described in detail, but the present invention is not limited to these descriptions.

[0055] (First Embodiment)

[0056] First, as Figure 1 shown, an epitaxial wafer 7 is prepared. The epitaxial wafer 7 is formed by laminating a first-conductive-type GaAs buffer layer on a first-conductive-type GaAs starting substrate 1, and then sequentially growing, for example, a 0.1-μm-thick first-conductive-type Ga x In 1-x P (0.4 ≤ x ≤ 0.6) first etch stop layer, for example, a 0.1-μm-thick first-conductive-type GaAs second etch stop layer, and for example, a 1.0-μm-thick first-conductive-type (Al y Ga 1-y ) x In 1-x P (0.4 ≤ x ≤ 0.6, 0.6 ≤ y ≤ 1.0) first cladding layer (first cladding layer 3), an undoped (Al y Ga 1-y ) x In 1-x P (0.4 ≤ x ≤ 0.6, 0 ≤ y ≤ 0.5) active layer 4, for example, a 1.0-μm-thick second-conductive-type (Al y Ga 1-y ) x In 1-x P (0.4 ≤ x ≤ 0.6, 0.6 ≤ y ≤ 1.0) second cladding layer (second cladding layer 5), for example, a 0.1-μm-thick second-conductive-type Ga x In 1-x P (0.5 ≤ x ≤ 1.0) intermediate layer, and a second-conductive-type GaP window layer 6, and has a light-emitting element structure as an epitaxial functional layer. Here, the first cladding layer 3 to the second cladding layer 5 are referred to as a double heterostructure (DH) portion (DH layer 8, or light-emitting element structure 8).

[0057] The film thickness is only an example, and the film thickness is only a parameter that changes according to the operating specifications of the device, and is not limited to the film thickness described herein. In addition, although the first cladding layer and the second cladding layer are both exemplified as 1.0 μm, in MicroLED devices, the rated current density is less than that of larger-sized discrete LED devices, and even if it is thinner than this film thickness, the function as a cladding layer will not be impaired.

[0058] Since the electrode is formed in contact with the first cladding layer 3 as described below, considering the metal diffusion during the formation of ohmic contact, the first cladding layer 3 preferably has a thickness of 0.6 μm or more. Any thickness can be selected as long as it is 0.6 μm or more. However, if it becomes too thick, it will be the main cause of cost increase, and the luminous efficiency during constant current driving will decrease, or the production yield will decrease due to the increase in wafer warpage. Therefore, it is preferably designed within the range of 10 μm or less.

[0059] When the second conductivity type is P-type, the effective mass of holes is large. Therefore, even if the second cladding layer 5 has a thickness of about 0.2 μm, for example, it will function in the same way as 1.0 μm. Therefore, any thickness can be selected as long as it is 0.2 μm or more. However, if it becomes too thick, it will be the main cause of cost increase, and the luminous efficiency during constant current driving will decrease, or the production yield will decrease due to the increase in wafer warpage. Therefore, it is preferably designed within the range of 10 μm or less.

[0060] In addition, each layer is not a single composition layer and may have multiple composition layers within the composition range exemplified.

[0061] In addition, the level of carrier concentration is not uniform in each layer and may have multiple levels within each layer.

[0062] The active layer 4 can be composed of a single composition, and even a superlattice structure formed by alternately laminating multiple barrier layers and active layers has a similar function, and both can be selected. No matter which structure is selected, the effects of the present technology are the same.

[0063] The thickness of the GaP window layer 6 needs to exceed 5 μm. For example, it can be set to about 6 μm, but it is not limited to this thickness. Any film thickness can be selected as long as it is within the range thinner than the short side length of the following element isolation.

[0064] Subsequently, as shown in Figure 2 Benzocyclobutene (BCB) as a thermosetting bonding member (hereinafter referred to as bonding material 9) is spin-coated on the epitaxial wafer 7, overlapped with the sapphire wafer (transparent wafer 10) as the wafer to be bonded in an opposite manner, and thermocompression bonding is performed in a vacuum atmosphere. When spin-coating BCB, the designed film thickness can be set to 0.6 μm, for example.

[0065] In addition, it is not limited to a vacuum atmosphere. Any atmosphere can be adopted as long as an atmosphere with oxygen of 100 ppm or less can be produced. The same effect can be obtained even in a nitrogen atmosphere or an argon atmosphere.

[0066] In addition, the substrate to be bonded is not limited to sapphire, and any material can be selected as long as it can ensure the laser transmissivity and flatness for LLO. In addition to sapphire, quartz can also be selected.

[0067] In addition, BCB is not limited to the case where it is coated in a layered state. Even when using photosensitive BCB and patterning it into isolated island shapes, linear shapes, or other shapes and performing the bonding process, the same result can be obtained.

[0068] In addition, the thickness of BCB is not limited to 0.6 μm, and even if it is thinner than this thickness, the same effect can be obtained.

[0069] Subsequently, as Figure 3 shown, the GaAs starting substrate is removed by wet etching to expose the first etch stop layer, and the first etch stop layer and the second etch stop layer are removed using etchants suitable for them respectively to expose the first cladding layer 3, and an epitaxial bonded substrate 11 that only holds the DH layer 8 and the GaP window layer 6 is fabricated.

[0070] Subsequently, as Figure 4 shown, a plasma chemical vapor deposition (P-CVD) method using tetraethyl orthosilicate (TEOS) and O 2 as raw materials is used to form, for example, a 1-μm-thick SiO 2 film on the epitaxial layer of the epitaxial bonded substrate 11. Subsequently, a resist pattern is formed by photolithography (hereinafter referred to as photolithography method), and a pattern shape of SiO 2 is fabricated using a hydrofluoric acid solution. In addition, the pattern shape of this SiO 2 is set such that one side is less than 100 μm. Subsequently, using the SiO 2 pattern as a hard mask, inductively coupled plasma (ICP) processing is performed using an ICP apparatus introduced with a chlorine-based gas to dry-etch the DH layer 8 and the GaP window layer 6 to expose the BCB layer (bonding material 9), and the etching gas is switched to further dry-etch the exposed BCB layer (bonding material 9) to expose the sapphire wafer (transparent wafer 10), and an element isolation pattern composed of the DH layer 8 and the GaP window layer 6 is formed. After forming the element isolation pattern, a SiO 2 pattern is formed so as to open a part of the element isolation pattern, and a part of the DH layer 8 is etched using the ICP method as described above to expose the second cladding layer 5 or the intermediate layer, or the GaP window layer 6, and it is processed into a bathtub-shaped processing portion 12.

[0071] Figure 4 The bathtub-shaped processing portion 12 of

[0072] In addition, the bathtub-shaped processing section 12 is not limited to a substantially quadrilateral shape as shown in Figure 8 , and may be a shape such as an ellipse, a circle, or a polygon. By forming the bathtub-shaped processing section 12 in this way, the outer periphery of the element (crystal grain 13) becomes a structure surrounded by the light-emitting element structure 8, and the light-emitting element structure 8 exists in the portion that should be the stress concentration point, so that a decrease in strength is less likely to occur. Therefore, the frequency of cracking of the crystal grain 13 decreases.

[0073] Subsequently, as shown in Figure 5 , the P-CVD method using TEOS and O 2 as raw materials is used to cover the entire surface with, for example, a 0.1-μm-thick SiO 2 layer to form the insulating film 14. In addition, not limited to the P-CVD method only, other film-forming methods such as sputtering, photo-CVD, electron beam (EB) evaporation, and pulsed laser deposition (PLD) method can also be used.

[0074] Subsequently, a resist is formed by photolithography in such a way that both the bottom of the bathtub-shaped processing section 12, that is, the second contact portion 15 (opening portion 15), and a part of the first coating layer 3, that is, the first contact portion 16 (opening portion 16), are opened, and the opening portions are formed by a wet etching method using a hydrofluoric acid-based etchant. The opening portions 15 and 16 are the second contact portion which is the bottom of the bathtub-shaped processing section and the first contact portion where a part of the first coating layer is exposed.

[0075] Subsequently, after the opening process, a first contact electrode (first ohmic electrode 17) is formed on the first contact portion 16, and a second contact electrode (second ohmic electrode 18) is formed on the second contact portion 15 (see Figure 8 ). When the first conductivity type is P-type, the first contact electrode is a metal containing AuZn or AuBe, and the second contact electrode is formed using a metal containing AuGe or AuSi. When the first conductivity type is N-type, the first contact electrode is a metal containing AuGe or AuSi, and the second contact electrode is formed using a metal containing AuZn or AuBe. The film thickness is substantially the same as that of the SiO 2 insulating film 14, and can be formed to be, for example, 0.1 μm respectively.

[0076] In addition, the thickness of each contact electrode is not limited to 0.1 μm. Whether it is thicker or thinner than this film thickness, the same effect can be obtained, but in the case of being too thin, the ohmic characteristics may deteriorate. To prevent this situation, a thickness of 0.05 μm or more is preferably provided. In this technology, the key point is to make the thickness of the contact electrode and the SiO 2 insulating film 14 substantially the same. Therefore, if the SiO 2If the insulating film 14 is too thin, the coverage rate of the processed side surface will decrease, and there is a possibility of leakage current occurring on the processed side surface. Therefore, it is not good for the SiO insulating film 14 to be too thin. Thus, it is preferably set to a film thickness of 0.05 μm or more. In addition, when the contact electrode is too thick, the effect of the present technology will be reduced when forming the following pad electrode. Therefore, the thickness of the contact electrode is preferably 1 / 5 or less of that of the following pad electrode. Generally, the pad electrode does not exceed 3 μm in thickness. Therefore, the contact electrode is preferably 0.6 μm or less. 2 Subsequently, as shown in and

[0077] , after forming the contact electrode, pad electrodes 19 and 20 are formed in such a manner as to contact at least a part of each contact electrode and be electrically isolated from each other. The thickness of the pad electrode is preferably set to the thickness of the contact electrode, and particularly preferably set to a thickness of 5 times or more of the contact electrode in contact with the first coating layer 3. The pad electrode can be formed, for example, by a vacuum evaporation method. In addition, by setting the pad electrode to a thickness of 5 times or more and 0.25 μm or more of the thickness of the contact electrode, the unevenness (height difference) between the SiO insulating film and the surface of the contact electrode is alleviated, and stress concentration during the LLO process can be reduced or avoided.

[0077] Subsequently, as Figure 6 shown, after forming the contact electrode, pad electrodes 19 and 20 are formed in such a manner as to contact at least a part of each contact electrode and be electrically isolated from each other. The thickness of the pad electrode is preferably set to the thickness of the contact electrode, and particularly preferably set to a thickness of 5 times or more of the contact electrode in contact with the first coating layer 3. The pad electrode can be formed, for example, by a vacuum evaporation method. In addition, by setting the pad electrode to a thickness of 5 times or more and 0.25 μm or more of the thickness of the contact electrode, the unevenness (height difference) between the SiO insulating film and the surface of the contact electrode is alleviated, and stress concentration during the LLO process can be reduced or avoided. 2 In addition, the top view after forming the pad electrodes 19 and 20 is shown in Figure 8 and Figure 8 , and it is described in such a way as to understand the relationship with the first contact electrode (first ohmic electrode 17) and the second contact electrode (second ohmic electrode 18). In addition, the cross-sectional view taken along the line A - A' of Figure 9 is shown in and

[0078] . Figure 8 In addition, the top view after forming the pad electrodes 19 and 20 is shown in Figure 8 and Figure 8 , and it is described in such a way as to understand the relationship with the first contact electrode (first ohmic electrode 17) and the second contact electrode (second ohmic electrode 18). In addition, the cross-sectional view taken along the line A - A' of Figure 9 is shown in and

[0078] . Figure 8 The cross-sectional view taken along the line A - A' of Figure 9 is shown in and

[0078] . Figure 9

[0078] Subsequently, as Figure 7 shown, the Micro LED element pattern is pressed against a quartz substrate (transfer substrate 22) having a silicone convex pattern (silicone layer 21) similar to the Micro LED element pattern and pitch, and excimer laser is irradiated from the sapphire substrate side to sublime the BCB. The LLO process of separating the Micro LED element from the sapphire by sublimating the BCB is performed, and the Micro LED element is transferred from the sapphire substrate to the quartz substrate.

[0079] As described above, the Micro LED element in the present embodiment is a Micro LED element having a side length of less than 100 μm, and the Micro LED element has a light-emitting element structure 8 which is composed of (Al y Ga 1-y ) x In 1-x ​A light-emitting element structure in which an active layer 4 formed by P(0.4≤x≤0.6, 0≤y≤0.5) is sandwiched between a first coating layer 3 and a second coating layer 5; an upper electrode 17 (first contact electrode, first Ohmic electrode); and a lower electrode 18 (second contact electrode, second Ohmic electrode) having a polarity different from that of the upper electrode. In this Micro LED element, the light-emitting element structure 8, the upper electrode 17, and the lower electrode 18 are disposed on the first surface of the Micro LED element. The upper electrode 17 is disposed on the top surface of the light-emitting element structure 8, and the lower electrode 18 is disposed at a position where the light-emitting element structure 8 does not exist. The Micro LED element has the light-emitting element structure 8 surrounding the periphery of the lower electrode 18.

[0080] In the conventional Micro LED element structure, there is a height difference between the upper electrode and the lower electrode, which easily generates stress concentration points. However, in the Micro LED element of the present invention, as can be seen from the structure of Figure 8 , Figure 9 , by having the light-emitting element structure 8 surrounding the periphery of the lower electrode 18, the light-emitting element structure 8 exists in the part that should be the stress concentration point, and it is not easy to cause a decrease in strength. Therefore, the frequency of grain cracking can be reduced.

[0081] In addition, in the first aspect, the light-emitting element structure 8 surrounding the periphery of the lower electrode 18 continuously and uninterruptedly surrounds the periphery of the lower electrode 18.

[0082] If the light-emitting element structure 8 continuously and uninterruptedly surrounds the periphery of the lower electrode 18, there is no height difference between the upper electrode 17 and the part surrounding the lower electrode 18, and it is least likely to cause a decrease in strength. By preventing the decrease in strength in this way, the frequency of grain cracking can be reduced.

[0083] In addition, a wafer (sapphire wafer 10) that is transparent to the emission wavelength and the laser for LLO transfer is bonded to the second surface of the Micro LED element using BCB (bonding material 9) that is transparent to the emission wavelength and absorbs the laser for LLO transfer. When performing the LLO (laser lift-off) process in such a bonded wafer, although the LLO process has a relatively high frequency of cracking in the past, the frequency of grain cracking can be reduced by the present invention.

[0084] In addition, although the bonding material 9 is set as BCB, it is not limited to BCB, and the same adhesive or bonding material can also be used.

[0085] In addition, although the transparent wafer 10 is set as sapphire, it is not limited to sapphire, and it can also be quartz. As long as the laser transmissivity and flatness for LLO can be ensured, any material can be selected.

[0086] (Second Embodiment)

[0087] In the second embodiment, the process of processing in such a manner as to have a tub-shaped processing portion exposing a second cladding layer, or a GaInP intermediate layer, or a GaP window layer, etc., which are second conductive type layers, is the same as in the first embodiment, but it is different from the first embodiment in that it has a notch portion in the corner direction of the element separation pattern.

[0088] As Figure 10 shown, there may be two notch portions 23 at the corners, and as Figure 14 shown, there may be one. In addition, Figure 11 shows the cross-sectional view taken along the line A-A’ shown in Figure 10 . Additionally, the cross-sectional view of Figure 14 is the same as that of Figure 11 , and thus is omitted.

[0089] In Figure 10 , the boundary portion 24 between the notch portion 23 at the corner and the outside of the light-emitting element structure 8 is provided so as not to be closer to the inside than the end portion 25 of the lower electrode (the second contact electrode (the second ohmic electrode 18)). That is, the length D of Figure 10 is set to D≥0. By adopting such a structure, the light-emitting element structure 8 exists in the portion that should be the stress concentration point, preventing stress from being applied to the lower electrode (the second contact electrode (the second ohmic electrode 18)), which is a thinner portion in the element (die), and it is not easy to cause a decrease in strength. Therefore, the frequency of die cracking decreases.

[0090] In addition, Figure 12 shows the cross-sectional view taken along the line B-B’ shown in Figure 10 , and Figure 13 shows the cross-sectional view taken along the line C-C’ shown in Figure 10 . It can be understood that by arranging the light-emitting element structure 8 at both ends of Figure 12 and in the center of Figure 13 , it is not easy to apply stress to the lower electrode (the second contact electrode (the second ohmic electrode 18)).

[0091] As described above, in the present embodiment, the light-emitting element structure 8 surrounding the periphery of the lower electrode (the second contact electrode (the second ohmic electrode 18)) has a partial notch portion 23, and the boundary portion 24 between the notch portion 23 and the outside of the light-emitting element structure 8 is located outside the end portion 25 of the lower electrode (the second contact electrode (the second ohmic electrode 18)).

[0092] Thus, even if the light-emitting element structure 8 has a partial notch portion 23, as long as the boundary portion 24 between the notch portion 23 and the outside of the light-emitting element structure 8 is located closer to the outside than the end portion 25 of the lower electrode (second contact electrode (second ohmic electrode 18)), a sufficient prevention of intensity degradation can be achieved. By preventing intensity degradation in this way, the frequency of crystal grain cracking can be reduced.

[0093] Example

[0094] Hereinafter, examples and comparative examples are shown to more specifically illustrate the present invention, but the present invention is not limited to these examples.

[0095] (Example 1)

[0096] An epitaxial wafer was prepared. After laminating a first-conductive-type GaAs buffer layer on a first-conductive-type GaAs starting substrate, a first-conductive-type Ga x In 1-x P (0.4 ≤ x ≤ 0.6) first etch stop layer, a 0.1-μm-thick first-conductive-type GaAs second etch stop layer, a 1.0-μm-thick first-conductive-type (Al y Ga 1-y ) x In 1-x P (0.4 ≤ x ≤ 0.6, 0.6 ≤ y ≤ 1.0) first cladding layer, an undoped (Al y Ga 1-y ) x In 1-x P (0.4 ≤ x ≤ 0.6, 0 ≤ y ≤ 0.5) active layer, a 1.0-μm-thick second-conductive-type (Al y Ga 1-y ) x In 1-x P (0.4 ≤ x ≤ 0.6, 0.6 ≤ y ≤ 1.0) second cladding layer, a 0.1-μm-thick second-conductive-type Ga x In 1-x P (0.5 ≤ x ≤ 1.0) intermediate layer, and a second-conductive-type GaP window layer with a thickness of 6 μm were formed, and it had a light-emitting element structure as an epitaxial functional layer.

[0097] Subsequently, benzocyclobutene (BCB) as a thermosetting bonding member was spin-coated on the epitaxial wafer, overlapped with a sapphire wafer as a wafer to be bonded in a facing manner, and thermocompression bonding was performed in a vacuum atmosphere. When BCB was spin-coated, the designed film thickness was set to 0.6 μm.

[0098] Subsequently, the GaAs starting substrate is removed by wet etching to expose the first etch stop layer, and the first etch stop layer is removed using etchants suitable for the first etch stop layer and the second etch stop layer respectively to expose the first cladding layer, and an epitaxial junction substrate retaining only the DH layer and the window layer is fabricated.

[0099] Subsequently, a 1-μm-thick SiO 2 film is formed on the EP junction substrate by P-CVD method using TEOS and O 2 as raw materials. A resist pattern is formed by photolithography, and the pattern shape of SiO 2 is fabricated using a hydrofluoric acid solution. The pattern shape of this SiO 2 is a quadrilateral of 35×55 μm. Using the SiO 2 pattern as a hard mask, ICP processing is performed using an ICP apparatus introduced with a chlorine-based gas to dry-etch the DH layer portion and the GaP layer to expose the BCB layer, and the BCB layer is dry-etched by changing to a CF-based gas to form an element isolation pattern composed of the DH layer portion and the GaP layer. After forming the element isolation pattern, a SiO 2 pattern is formed in such a manner that a part of the element isolation pattern is opened, and a part of the DH layer portion is etched by the ICP method in the same manner as described above to expose the second cladding layer or the intermediate layer, or the GaP layer, and it is processed into a shape having a bathtub-shaped processed portion.

[0100] After forming the bathtub-shaped processed portion, a 0.1-μm-thick SiO 2 layer is formed to cover the entire surface by P-CVD method using TEOS and O 2 as raw materials to form an insulating film.

[0101] A resist pattern is formed by photolithography in such a manner that the bottom of the bathtub-shaped processed portion, i.e., the second contact portion, and a part of the first cladding layer and the first contact portion are opened, and an opening portion is formed by wet etching using a hydrofluoric acid-based etchant. The opening portion is the bottom of the bathtub-shaped processed portion, i.e., the second contact portion, and the first contact portion where a part of the first cladding layer is exposed.

[0102] After the opening process, a first contact electrode is formed on the first contact portion, and a second contact electrode is formed on the second contact portion. The film thickness is substantially the same as that of the SiO 2 insulating film, and they are formed to be 0.1 μm respectively.

[0103] After forming the contact electrodes, a pad electrode is formed in such a manner that it contacts at least a part of each contact electrode and the electrodes are electrically isolated from each other.

[0104] The Micro LED element pattern is pressed against a quartz substrate having a silicone convex pattern similar to the Micro LED element pattern and pitch. The LLO process of separating the Micro LED element from the sapphire substrate by irradiating excimer laser from the sapphire substrate side to sublime the BCB is performed, and the Micro LED element is transferred from the sapphire substrate to the quartz substrate.

[0105] (Example 2)

[0106] Example 2 is the same as Example 1 except that Figure 10 as shown, there are two notch portions symmetrically on the left and right at the corners of the element separation pattern. In addition, the length D of the notch portion at the corner is set to 2 μm as Figure 10 shown.

[0107] (Example 3)

[0108] Example 3 is the same as Example 2 except that the length D is set to 0 μm.

[0109] (Comparative Example 1)

[0110] In Comparative Example 1, the processing of exposing the second conductive type layer of the second cladding layer is performed in the same manner as in Example 1, but it is not a bathtub-shaped processing, and as Figure 15 , Figure 16 shown, the entire periphery of the second contact electrode is set to a structure where the second conductive type layer is exposed. Except for this, the Micro LED element is manufactured under the same conditions as in Example 1.

[0111] (Comparative Example 2)

[0112] Comparative Example 2 is the same as Example 2 except that the length D is set to -2 μm.

[0113] (Fracture conditions of Micro LED elements in Examples and Comparative Examples)

[0114] Table 1 shows the incidence rate (%) of cracking of Micro LED elements during the LLO process in Examples 1, 2, 3 and Comparative Examples 1, 2. As shown in Table 1, the average cracking incidence rate in Example 1 or Examples 2, 3 is 0%. Example 1 has a light-emitting element structure that continuously and uninterruptedly surrounds the periphery of the lower electrode. Examples 2, 3 have a notch at the corner, and the boundary between the notch and the outer side of the light-emitting element structure is provided outside the end of the lower electrode (D≥0). It can be seen that compared with the average cracking incidence rate in Comparative Example 1 or Comparative Example 2 (30%, 27%), this example has been greatly improved. Comparative Example 1 is a comparative example in which there is no light-emitting element structure around the lower electrode as the conventional structure. Comparative Example 2 has a light-emitting element structure that has a notch at the corner, but the boundary between the notch and the outer side of the light-emitting element structure is provided closer to the inside than the end of the lower electrode (D<0).

[0115] [Table 1]

[0116]

[0117] In addition, the present invention is not limited to the above embodiments. The above embodiments are illustrative, and any technical solutions having the same essential structure as the technical idea described in the claims of the present invention and achieving the same effects are included in the technical scope of the present invention.

Claims

1. A Micro LED element, one side of which is less than 100 μm, the Micro LED element having: Light-emitting element structure, which is a light-emitting element structure in which an active layer composed of (Al y Ga 1-y ) x In 1-x P is sandwiched between a first cladding layer and a second cladding layer Wherein, 0.4 ≤ x ≤ 0.6, 0 ≤ y ≤ 0.5; An upper electrode; And A lower electrode, the polarity of which is different from that of the upper electrode, The Micro LED element is characterized in that The light-emitting element structure, the upper electrode, and the lower electrode are disposed on the first surface of the Micro LED element, The upper electrode is disposed on the top surface of the light-emitting element structure, The lower electrode is disposed at a position where there is no light-emitting element structure, The Micro LED element has the light-emitting element structure so as to surround the periphery of the lower electrode.

2. The Micro LED element according to claim 1, Characterized in that The light-emitting element structure surrounding the periphery of the lower electrode continuously and uninterruptedly surrounds the periphery of the lower electrode, or has a partial notch, and the boundary portion of the notch with the outside of the light-emitting element structure is located closer to the outside than the end portion of the lower electrode.

3. The Micro LED element according to claim 2, Characterized in that A wafer transparent to the emission wavelength is bonded to the second surface of the Micro LED element by an adhesive or a bonding material.

4. The Micro LED element according to claim 3, Characterized in that The adhesive or the bonding material is BCB.

5. The Micro LED element according to claim 3 or 4, Characterized in that The transparent wafer is sapphire or quartz.

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