Micro LED structure and manufacturing method thereof

Abstract

To provide a micro-LED structure in which a transparent substrate and a light-emitting element structure including an AlGaInP-based active layer are bonded to each other through an adhesive or a bonding agent, and the crack of the micro-LED structure can be reduced or avoided at the transfer in an LLO step.SOLUTION: A micro-LED structure includes a light-emitting element structure including (AlyGa1-y)xIn1-xP (0.4≤x≤0.6, 0≤y≤0.5) as an active layer. The light-emitting element structure is bonded to a transparent substrate that is transparent to light-emitting wavelength and laser light for LLO transfer with an adhesive or a bonding material that is transparent to the light-emitting wavelength and absorbs the laser light for the LLO transfer. The light-emitting element structure is separated for each element, and the light-emitting element structure after the element separation includes at least two electrodes with different polarities on one surface. A long-side direction of an outer shape in a plan view of the light-emitting element structure after the element separation does not coincide with a crystal orientation <110>.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a micro LED structure and a method for manufacturing the same. [Background technology]

[0002] To realize a micro light-emitting diode display (micro LED display), a technology has been disclosed in which LEDs are peeled off from a starting substrate using laser lift-off (LLO), transferred to a mounting substrate, and then transferred to a drive substrate (Patent Document 1). However, all of this technology is only for GaN-based LEDs, and there are few technical disclosures regarding micro LEDs (μ-LEDs) using AlGaInP-based LEDs.

[0003] To realize a micro LED element using the LLO process with an AlGaInP LED, it is necessary to transfer the LED to a substrate that is transparent to the LLO laser, such as a sapphire substrate. Prior art disclosures regarding the technology for transferring an AlGaInP LED to a sapphire substrate include Patent Document 2. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Special Publication No. 2020-521181 [Patent Document 2] Japanese Patent Publication No. 2022-013203 [Patent Document 3] Japanese Patent Application Laid-Open No. 2016-004892 [Patent Document 4] Japanese Patent Application Laid-Open No. 2007-242804 [Patent Document 5] Japanese Patent Application Laid-Open No. 2015-084448 Summary of the Invention [Problem to be solved by the invention]

[0005] However, AlGaInP-based LEDs are mechanically more fragile than GaN-based LEDs, and there is a problem that die cracking is more likely to occur during the LLO process depending on the appropriateness of the die design. There is no disclosure of technology to prevent cracking of the micro LED structure during the LLO process (also known as "μ-LED die cracking").

[0006] Furthermore, due to their thinness, micro LEDs are more susceptible to stress than conventional LEDs. According to the inventors' investigations, due to this low strength, when the element is pressed against the transfer substrate during the LLO process, stress is applied to the step portion of the element to attach electrodes with different polarities, and the direction in which the step extends in a planar view is different from the crystal orientation. <110> It was found that when the thickness of the crystal is approximately equal to the cleavage property of the crystal, the crystal is very susceptible to cracking.

[0007] In addition, Patent Document 3 discloses a technique for preventing chipping during the dicing process when forming dice of conventional-sized LEDs, rather than the cracking of the dice when transferring micro LEDs. In Patent Document 3, when dicing conventional-sized LEDs, the planned dicing line is aligned with the crystal orientation. <110> However, Patent Document 3 discloses a technology to prevent chipping during the dicing process of conventional-sized LEDs, and does not address the issue of die cracking when transferring micro LEDs in the LLO process.

[0008] Furthermore, prior art for angled dies is disclosed in Patent Document 4. This is a technology for angled dies relative to the growth direction, but it is not intended to address dies cracking when transferring micro LEDs in the LLO process.

[0009] In Patent Document 5, the device functional part is formed by adjusting the crystal orientation independently from the base of the device. <110> However, Patent Document 5 does not address the issue of die cracking when transferring micro LEDs in the LLO process.

[0010] For the reasons mentioned above, there is no disclosure of technology to prevent micro LED die cracking during the LLO process.

[0011] The present invention has been made in consideration of the above-mentioned problems, and aims to provide a micro LED structure in which a light emitting element structure having an AlGaInP-based active layer is bonded to a transparent substrate via an adhesive or bonding agent, and which can reduce or avoid cracking of the micro LED structure when transferred in the LLO process, and a manufacturing method thereof. [Means for solving the problem]

[0012] The present invention has been made to achieve the above object, and y Ga 1-y ) x In 1-x A micro LED structure having a light emitting element structure having P (0.4≦x≦0.6, 0≦y≦0.5) as an active layer, the light emitting element structure being bonded to a transparent substrate that is transparent to the emission wavelength and laser light for LLO transfer with an adhesive or bonding material that is transparent to the emission wavelength and absorbs the laser light for LLO transfer, the light emitting element structure being isolated from the other element, the isolated light emitting element structure having at least two electrodes of different polarities on one surface, and the direction of the long side of the outline of the isolated light emitting element structure in a plan view being aligned along a crystal orientation <110> The present invention provides a micro LED structure characterized in that it does not match the above.

[0013] Generally, a micro LED structure having an AlGaInP-based active layer has low mechanical strength, but the micro LED structure of the present invention can prevent the parts with particularly low structural strength from being easily cracked due to the cleavage of the crystal, and as a result, cracking (dice cracking, breakage) of the micro LED structure can be reduced or avoided when transferring the micro LED structure in the LLO process.

[0014] In this case, the direction of the long side of the outline of the light emitting element structure in plan view is <110> It is preferable that the angle is shifted in the range of 10° to 45° from the angle.

[0015] Furthermore, in this case, the direction of the long side of the outline of the light emitting element structure in plan view is <110> It is preferable that the deviation is in the range of 22.5° to 30° from the reference angle.

[0016] At such an angle, the long side direction of the outline of the light emitting element structure in plan view is aligned with the crystal orientation <110> Not only that, but it is also prone to breaking. <100> Since it can be angled far from the azimuth, it can more effectively reduce and improve the rate of cracks (dice cracks, breakage) occurring in the micro LED structure during the LLO process.

[0017] In addition, in the micro LED structure of the present invention, it is preferable that the light emitting element structure does not have a starting substrate.

[0018] In this way, by making the light emitting element structure not have a starting substrate, it becomes possible to transfer it to a desired transfer substrate.

[0019] The adhesive or bonding material is preferably benzocyclobutene.

[0020] In this way, by using benzocyclobutene as an adhesive or bonding material, the LLO treatment using an excimer laser can be carried out reliably.

[0021] The transparent substrate is preferably made of sapphire or quartz.

[0022] As the transparent substrate, these substrates can be suitably used, and substrates having particularly high transparency to the laser for LLO can be selected.

[0023] The present invention also provides a method for manufacturing a semiconductor device comprising: y Ga 1-y ) x In 1-xA method for manufacturing a micro LED structure, comprising the steps of: forming a light emitting device structure having P (0.4≦x≦0.6, 0≦y≦0.5) as an active layer; bonding the light emitting device structure to a transparent substrate transparent to the emission wavelength of the light emitting device structure with an adhesive or a bonding material; isolating the light emitting device structure; and forming at least two electrodes of different polarities on one surface of the isolated light emitting device structure, wherein in the isolating step, the direction of the long side of the outline of the isolated light emitting device structure in a plan view is oriented in a direction of a crystal orientation <110> The present invention provides a method for manufacturing a micro LED structure, characterized in that the micro LED structure is not coincident with the

[0024] This method for manufacturing a micro LED structure can prevent the structurally weak portions of the manufactured micro LED structure from being easily cracked due to the cleavage of the crystal, and as a result, cracking (breakage) of the micro LED structure can be reduced or avoided when transferring the micro LED structure in the LLO process.

[0025] In this case, the direction of the long side of the outline of the light emitting element structure in plan view is <110> It is preferable that the angle be shifted in the range of 10° to 45° from the reference angle.

[0026] Furthermore, in this case, the direction of the long side of the outline of the light emitting element structure in plan view is <110> The angle can be shifted within a range of 22.5° to 30°.

[0027] At this angle, the long side direction of the outline of the light emitting element structure in plan view is set to the crystal orientation. <110> By performing element isolation that is offset from the wafer, the rate of die cracking during the LLO process can be more effectively reduced and improved.

[0028] In addition, the method for manufacturing a micro LED structure of the present invention preferably further comprises a step of removing the starting substrate.

[0029] In this way, by removing the starting substrate, transfer to a desired transfer substrate becomes possible.

[0030] The adhesive or bonding material is preferably benzocyclobutene.

[0031] In this way, by using benzocyclobutene as an adhesive or bonding material, the LLO treatment using an excimer laser can be carried out reliably.

[0032] The transparent substrate is preferably made of sapphire or quartz.

[0033] As the transparent substrate, these substrates can be suitably used, and substrates having particularly high transparency to the laser for LLO can be selected. [Effects of the Invention]

[0034] Generally, micro LED structures having an AlGaInP-based active layer have low mechanical strength. In contrast, the micro LED structure of the present invention can prevent portions with low structural strength from being easily cracked due to the cleavage of the crystal. Therefore, according to the present invention, cracking (dice cracking, breakage) of the micro LED structure can be reduced or avoided when transferring the micro LED structure in the LLO process. Furthermore, the manufacturing method of the micro LED structure of the present invention can manufacture such a micro LED structure. [Brief explanation of the drawings]

[0035] [Figure 1] 1 is a schematic plan view of an example (first embodiment) of a micro LED structure of the present invention. [Figure 2] FIG. 2 is a schematic plan view of another example (second embodiment) of the micro LED structure of the present invention. [Figure 3] FIG. 10 is a schematic plan view of yet another example (third embodiment) of the micro LED structure of the present invention. [Figure 4] FIG. 10 is a schematic plan view of yet another example (fourth embodiment) of the micro LED structure of the present invention. [Figure 5]1A-1D are schematic cross-sectional views illustrating a part of a method for manufacturing a micro LED structure of the present invention. [Figure 6] 5A to 5C are schematic cross-sectional views illustrating another part of the method for manufacturing the micro LED structure of the present invention. [Figure 7] 5A to 5C are schematic cross-sectional views illustrating another part of the method for manufacturing the micro LED structure of the present invention. [Figure 8] 5A to 5C are schematic cross-sectional views illustrating another part of the method for manufacturing the micro LED structure of the present invention. [Figure 9] 5A to 5C are schematic cross-sectional views illustrating another part of the method for manufacturing the micro LED structure of the present invention. [Figure 10] 5A to 5C are schematic cross-sectional views illustrating another part of the method for manufacturing the micro LED structure of the present invention. [Figure 11] 1 is a schematic cross-sectional view showing a part of a method for transferring the micro LED structure of the present invention to a transfer substrate after manufacturing the micro LED structure. [Figure 12] 1 is a graph showing the results of Examples and Comparative Examples. DETAILED DESCRIPTION OF THE INVENTION

[0036] The micro LED structure of the present invention is y Ga 1-y ) x In 1-x A micro LED structure having a light emitting element structure having P (0.4≦x≦0.6, 0≦y≦0.5) as an active layer, the light emitting element structure being bonded to a transparent substrate that is transparent to the emission wavelength and laser light for LLO transfer with an adhesive or bonding material that is transparent to the emission wavelength and absorbs the laser light for LLO transfer, the light emitting element structure being isolated from the other element, the isolated light emitting element structure having at least two electrodes of different polarities on one surface, and the direction of the long side of the outline of the isolated light emitting element structure in a plan view being oriented in a crystal orientation <110> The micro LED structure may have a side length not exceeding 100 μm.

[0037] The present invention will be described in detail below with reference to the drawings, but the present invention is not limited thereto. Below, aspects of the present invention will be described by way of examples of first to fourth embodiments. Similar elements in each embodiment will be described with the same reference numerals.

[0038] (First embodiment) First, a first embodiment will be described, in which the micro LED structure has a square outer shape when viewed from above.

[0039] The micro LED structure of the present invention can be manufactured, for example, through the steps described below (FIGS. 5 to 10). Among these, the micro LED structure of the present invention will be described with reference to FIG. 10 and also with reference to FIG.

[0040] The micro LED structure 58 of the present invention, shown in schematic cross section in FIG. 10, is y Ga 1-y ) x In 1-x P (0.4≦x≦0.6, 0≦y≦0.5) as the active layer 14. The light emitting device structure 18 is bonded to a transparent substrate 30 that is transparent to the emission wavelength and the laser light for LLO transfer, with an adhesive or bonding material 25 that is transparent to the emission wavelength and absorbs the laser light for LLO transfer. The light emitting device structure 18 is isolated by an isolation trench (isolation trench 47 formed in FIG. 8, which will be described later). The isolated light emitting device structure 18 has at least two electrodes 54, 56 of different polarities on one surface. As shown in FIG. 1, which is a schematic plan view, the long side direction B of the outline of the isolated light emitting device structure 18 in plan view is aligned with the crystal orientation <110> It does not coincide with the direction A of the arrow.

[0041] In the present invention, as described above, the long side direction and the crystal orientation of the outline of the element-separated light-emitting element structure in plan view are <110> The long side of the outline is the longest side. In the first embodiment, the outline of the micro LED structure is a square when viewed from above. FIG. 1 shows a micro LED structure 58 having a light emitting element structure 18 that is separated into elements in a square shape. The long sides (longest sides) of the square are in two directions that are orthogonal to each other, and the crystal orientation of either long side is <110> The direction of is assumed to be shifted.

[0042] In FIG. 1, two electrodes 54, 56 of different polarities are shown, with the first electrode 54 as the upper electrode and the second electrode 56 as the lower electrode. The light-emitting layer region 19 shown in FIG. 1 indicates a region including the active layer 14 when viewed in plan. As can be seen from a comparison between FIG. 1 and FIG. 10, the first electrode 54 is located on the layer 13. The second electrode is located on the layer 15. As will be described later, since the layer 13 in FIG. 10 is of the first conductivity type and the layers 15 and 16 are of the second conductivity type, a step portion 57 is provided on each layer to attach electrodes of different polarities. Stress is applied to this step portion 57 when the element is pressed against the transfer substrate during the LLO process. The direction along this step portion 57 is the crystal orientation. <110> If the dice cleavage angle is the same as that of the GaN LED, the dice will be very susceptible to cracking. On the other hand, in the present invention, the step portion 57 has high strength and is less likely to crack. AlGaInP-based LEDs are mechanically weaker than GaN-based LEDs, and depending on the appropriateness of the dice design, dice cracking can easily occur during the LLO process. Therefore, the present invention is highly effective in suppressing dice cracking.

[0043] In this case, the direction of the long side of the outer shape of the light emitting element structure 18 when viewed from above is the crystal orientation <110> It is preferable that the direction of the long side of the outer shape of the light emitting element structure 18 when viewed from above is shifted from the crystal orientation in the range of 10° to 45°. <110> The deviation from (direction A) can be in the range of 22.5° to 30°.

[0044] Furthermore, in the micro LED structure 58 of the present invention, it is preferred that the light emitting device structure 18 does not have a starting substrate, as shown in Figure 10. By making the micro LED structure 58 free of a starting substrate, it becomes possible to transfer it to a desired transfer substrate. Making the light emitting device structure 18 free of a starting substrate can be achieved by removing the starting substrate 11 (see Figures 6 and 7) as described below.

[0045] In the micro LED structure 58 of the present invention, the adhesive or bonding material 25 is preferably benzocyclobutene (BCB). By using benzocyclobutene as the adhesive or bonding material, the LLO treatment using the excimer laser can be performed reliably.

[0046] In the micro LED structure 58 of the present invention, the transparent substrate 30 is preferably made of sapphire or quartz. These substrates can be suitably used as the transparent substrate, and those having high transparency to the LLO laser can be selected.

[0047] Next, a method for manufacturing such a micro LED structure of the present invention will be described. In the first embodiment, a case where a micro LED structure 58 having the outline shown in FIG. 1 in a plan view is manufactured will be described.

[0048] First, (Al y Ga 1-y ) x In 1-x A light emitting device structure having P (0.4≦x≦0.6, 0≦y≦0.5) as an active layer is formed. To this end, as shown in FIG. 5, epitaxial growth is performed sequentially on a starting substrate 11 to form each layer, and an epitaxial wafer 20 is produced. This produces an etch stop layer 12 and an epitaxial layer having a light emitting device structure 18. More specifically, the epitaxial growth of each layer can be performed as follows.

[0049] In this process, first, as shown in Fig. 5, an etch stop layer 12 is epitaxially grown on a GaAs substrate 11 of a first conductivity type, which is a starting substrate. The etch stop layer 12 is formed, for example, by stacking a GaAs buffer layer of the first conductivity type and then growing a GaAs buffer layer of the first conductivity type. x In 1-x A P(0.4≦x≦0.6) first etch stop layer can be formed by growing a first conductivity type GaAs second etch stop layer to a thickness of, for example, 0.1 μm. Furthermore, a first conductivity type (Al y Ga 1-y ) x In 1-x P(0.4≦x≦0.6, 0.6≦y≦1.0) The first clad layer 13 is formed to a thickness of, for example, 1.0 μm, and is made of non-doped (Al y Ga 1-y ) x In 1-x P(0.4≦x≦0.6, 0≦y≦0.5) active layer 14, the second conductivity type (Al y Ga 1-y ) x In 1-x The second cladding layer 15 is made of P(0.4≦x≦0.6, 0.6≦y≦1.0) and has a thickness of, for example, 1.0 μm. x In 1-x An epitaxial wafer 20 is prepared, which has a light-emitting element structure 18 as an epitaxial functional layer, in which a P(0.5≦x≦1.0) intermediate layer (not shown) having a thickness of, for example, 0.1 μm, a second conductivity type GaP window layer 16, and so on are grown in this order. Here, the layers from the first cladding layer 13 to the second cladding layer 15 are referred to as a double hetero (DH) structure (FIG. 5).

[0050] The thicknesses described above are merely examples, and the thicknesses are merely parameters that should be changed depending on the operating specifications of the device, and needless to say, are not limited to the thicknesses described here. While the first cladding layer 13 and the second cladding layer 15 are both 1.0 μm thick, the rated current density of a micro LED is smaller than that of a discrete LED with a larger size, and the cladding layer function is not impaired even if the thickness is thinner than this.

[0051] As described below, since an electrode is formed in contact with the first cladding layer 13, it is preferable that the first cladding layer 13 has a thickness of 0.6 μm or more, taking into consideration metal diffusion during ohmic contact formation. Any thickness greater than this can be selected. However, it is preferable to design the first cladding layer 13 to be 10 μm or less. Such a thickness does not significantly increase costs, can ensure light emission efficiency during constant current operation, and can achieve a high yield by suppressing wafer warpage.

[0052] When the second conductivity type is P-type, the effective mass of holes is large, so even if the second cladding layer 15 is approximately 0.2 μm thick, it functions as if it were 1.0 μm thick. Therefore, a thickness of 0.2 μm or more is preferable, and any thickness can be selected. However, it is preferable to design the second cladding layer 15 to be 10 μm or less. Such a thickness does not significantly increase costs, can ensure light emission efficiency during constant current operation, and can achieve high yields by suppressing wafer warpage.

[0053] It goes without saying that each layer is not a single composition layer, but rather includes the concept of having multiple composition layers within the composition ranges exemplified, and that the level of carrier concentration is not uniform in each layer, but includes the concept of having multiple levels within each layer.

[0054] The active layer 14 may be composed of a single composition, or may have a superlattice structure in which multiple barrier layers and active layers are alternately stacked, and both have similar functions, so either structure can be selected. Regardless of which structure is selected, the effects of the present technology are the same.

[0055] The thickness of the GaP window layer 16 is preferably greater than 5 μm, and may be, for example, 6 μm. However, the thickness is not limited to 6 μm, and any thickness may be selected as long as it is thinner than the short side length of the isolation.

[0056] 6, the light-emitting element structure 18 and a transparent substrate 30 that is transparent to the emission wavelength of the light-emitting element structure and the laser light for LLO transfer are bonded together using an adhesive or bonding material 25 that is transparent to the emission wavelength and absorbs the laser light for LLO transfer. For example, the epitaxial wafer 20 is spin-coated with adhesive or bonding material 25, such as benzocyclobutene (BCB), a thermosetting bonding material, and then the epitaxial wafer 20 is placed face-to-face with a transparent substrate 30 such as a sapphire wafer, and thermocompression bonded in a vacuum atmosphere. When applying BCB by spin coating, the film thickness can be, for example, 0.6 μm.

[0057] The atmosphere for thermocompression bonding is not limited to a vacuum atmosphere, and any atmosphere can be used as long as the oxygen concentration is 100 ppm or less. For example, a nitrogen atmosphere or an argon atmosphere can also provide the same effect.

[0058] Furthermore, the transparent substrate 30 is not limited to sapphire, and any material can be selected as long as it ensures laser light transparency and flatness. In addition to sapphire, quartz can also be selected.

[0059] Furthermore, when BCB is used as the adhesive or bonding material 25, in addition to applying BCB in a layer, similar results can be obtained by using photosensitive BCB to pattern it into isolated islands, lines, or other shapes and then performing the bonding process.

[0060] Furthermore, the thickness of the adhesive or bonding material 25 such as BCB is not limited to 0.6 μm, and may be thinner than this thickness.

[0061] Next, as shown in FIG. 7, the starting substrate 11 (e.g., a GaAs starting substrate) is preferably removed by wet etching. The etch stop layer 12 is then also removed. When the substrate has a first etch stop layer and a second etch stop layer as described above, the etch stop layer 12 can be removed by first exposing the first etch stop layer by etching, and then switching the etchant to remove the second etch stop layer and expose the epitaxial layer (first cladding layer 13 of the light-emitting device structure 18). In this way, a bonded wafer can be fabricated that retains only the double heterostructure (DH) portion (first cladding layer 13, active layer 14, second cladding layer 15) and the window layer 16 (FIG. 7).

[0062] 8, the light emitting element structure 18 is separated into elements. At this time, the long side direction B of the outer shape of the separated light emitting element structure 18 in plan view is aligned with the crystal orientation <110> The direction of the element isolation is set so as not to coincide with the direction A of the element isolation film (see FIG. 1). Specifically, this element isolation can be performed as follows, but is not limited to this as long as element isolation can be performed.

[0063] First, a SiO2 film is formed to a thickness of 1 μm on the epitaxially bonded wafer (that is, on the first cladding layer 13) by P-CVD (plasma CVD) using TEOS (tetraethoxysilane) and O2 as raw materials.

[0064] Next, a resist pattern is formed by photolithography, and a SiO2 pattern is created by wet etching with a hydrofluoric acid solution. Next, using the SiO2 pattern as a hard mask, an ICP (inductively coupled plasma) process is performed in an ICP device introducing chlorine-based gas. The DH structure (from the first cladding layer 13 to the second cladding layer 15) and the GaP window layer 16 are dry-etched to expose the adhesive or bonding material 25, such as a BCB layer. The etching gas is switched and the exposed adhesive or bonding material is further dry-etched to expose the sapphire substrate, forming an island pattern consisting of the DH structure (from the first cladding layer 13 to the second cladding layer 15) and the GaP window layer 16. This island pattern roughly matches the SiO2 pattern.

[0065] The shape of the SiO2 pattern here, that is, the shape that becomes the outline of the light emitting device structure in a plan view after element separation (the island-like pattern) is preferably less than 100 μm on a side, and in this embodiment, the shape is approximately square. In this embodiment, the approximately square pattern has a crystal orientation such that the line connecting the corner point and its diagonal corner is aligned with the crystal orientation. <110> It is preferable to form it so that it substantially coincides with the direction (see FIG. 1).

[0066] In this way, the line connecting the corner of the SiO2 pattern (that is, the shape that will become the outline of the light emitting device structure in a plan view after element separation) and its diagonal corner is the crystal orientation. <110> It can be formed so that it is approximately aligned with the direction (direction A), but the crystal orientation <110> It goes without saying that the same effect can be obtained even if the direction does not match exactly. <110> It is important that the direction of the edge does not coincide with the crystal orientation. <110> This effect can be more reliably achieved by shifting the diagonal line by 10 degrees or more. <110> That is, as shown in FIG. 1, the long side direction B of the outline of the element-isolated light-emitting element structure 18 when viewed from above is set to the direction of the crystal orientation <110> It is preferable that the direction of the long side of the outline of the isolated light emitting element structure 58 when viewed from above is shifted by 10° to 45° from the direction A of the crystal orientation. <110> The angle can be shifted from direction A by 22.5° to 30°.

[0067] Next, a step portion for forming an electrode is provided in each light-emitting element structure after element isolation, as shown in Fig. 8. Specifically, after the island pattern is formed, a part of the double hetero (DH) structure portion (first cladding layer 13, active layer 14, second cladding layer 15) is etched by the ICP method in the same manner as above, to expose the second cladding layer 15 or the GaP window layer 16.

[0068] After the element isolation process shown in FIG. 8 (and exposure of the second cladding layer 15 or GaP window layer 16), a protective film 52 can be formed on the processed cross section as end face processing, as shown in FIG. 9. Here, for example, a SiO2 protective film can be formed as the protective film 52 by the same P-CVD method as above. The protective film 52 is not limited to SiO2, and any material can be selected as long as it can protect the end face and has insulating properties. SiNx, titanium oxide, magnesium oxide, etc. can also be selected.

[0069] 10, at least two electrodes with different polarities are formed on one surface of the isolated light-emitting element structure 18. Here, "one surface" may refer to the surface opposite to the surface bonded to the transparent substrate 30 by the adhesive or bonding agent 25. Here, a first electrode 54 in contact with the first cladding layer 13 and a second electrode 56 in contact with the second cladding layer 15 or the GaP window layer 16 are formed to produce a micro LED structure 58 (also referred to as a "μ-LED die").

[0070] When the first conductivity type is P-type, it is preferable to select a metal containing Be or Zn for the surface of first electrode 54 in contact with first cladding layer 13, and a metal containing Si or Ge for the surface of second electrode 56 in contact with second cladding layer 15 or GaP window layer 16. When the first conductivity type is N-type, it is preferable to select a metal containing Si or Ge for the surface of first electrode 54 in contact with first cladding layer 13, and a metal containing Be or Zn for the surface of second electrode 56 in contact with second cladding layer 15 or GaP window layer 16. For example, when the first conductivity type is N-type and the second conductivity type is P-type, it is possible to use an AuSi-based alloy for the surface of first electrode 54 in contact with first cladding layer 13, and an AuBe-based alloy for the surface of second electrode 56 in contact with second cladding layer 15 or GaP window layer 16.

[0071] In this embodiment, the total thickness of the first electrode 54 and the second electrode 56 can be approximately 0.5 μm, but any thickness can be selected as long as ohmic contact can be formed. Furthermore, the same effect can be obtained by forming an additional metal layer, such as an Au or Al pad layer or various Au-based bumps, on either or both of the first electrode 54 and the second electrode 56.

[0072] Furthermore, an additional pad layer can be separately provided on the second electrode 56 to make the height equal to that of the first electrode 54. For example, if the second electrode 56 makes contact with the GaP window layer 16 and there is a step of about several μm (e.g., 2.5 μm) between the first electrode 54 and the second electrode 56, a pad electrode of several μm (e.g., 2.5 μm) made of Au can be additionally fabricated to make the height equal.

[0073] 11, the micro LED structure manufactured in this manner is fabricated by pressing the pattern of the micro LED structure (μ-LED die) onto a transfer substrate 70 made of quartz or the like having a silicone convex pattern (silicone resin 65) that matches the pattern and pitch of the micro LED structure, and irradiating an excimer laser from the side of the transparent substrate 30 made of sapphire or the like to sublimate the adhesive or bonding material 25 such as BCB. As the adhesive or bonding material 25 such as BCB sublimes, the μ-LED die is separated from the transparent substrate 30 made of sapphire or the like, and the micro LED die is transferred from the transparent substrate 30 made of sapphire or the like to the transfer substrate 70 made of quartz or the like.

[0074] (Second embodiment) Next, a second embodiment will be described, in which the micro LED structure has a rectangular outer shape in plan view.

[0075] In the second embodiment, the outline of the isolated light-emitting element structure 18 in plan view is rectangular, as shown in Fig. 2. Here, as shown in Fig. 2, the long side direction B of the outline of the isolated light-emitting element structure 18 in plan view is oriented in the direction of the crystal orientation <110> It is assumed that the direction A does not coincide with the direction A of the arrows.

[0076] The method for manufacturing this micro LED structure is as follows: First, the process and structure for manufacturing the bonding substrate (FIGS. 5 to 7) are the same as those in the first embodiment.

[0077] The element isolation process (including the process of forming an SiO2 pattern) (see FIG. 8) is also the same as in the first embodiment, but the SiO2 pattern shape is rectangular instead of square, unlike in the first embodiment. Here, as shown in FIG. 2, the long side direction B of the outline of the element-isolated light-emitting element structure 18 in a plan view is aligned with the crystal orientation <110> In particular, the crystal orientation <110> The direction (direction A) is the line connecting the corner and the diagonal corner. <110> It is preferable that the direction of the insulating film be approximately the same as that of the insulating film 1. The steps (FIGS. 9 to 11) after the element isolation step (including the step of forming the SiO2 pattern) are the same as those in the first embodiment.

[0078] (Third embodiment) Next, a third embodiment will be described. In this third embodiment, the outer shape of the element-isolated light-emitting element structure 18 when viewed from above is a rectangle with approximately straight sides but curved corners (i.e., rounded corners), as shown in FIG. 3. That is, this third embodiment is a modified version of the second embodiment, where the rectangle has corners that are not 90°. In this case, the long side is the longest straight line. The corners can have rounded corners not only in rectangles, but also in squares as shown in FIG. 1 and polygons as shown in FIG. 4, which will be described later. Here, as shown in FIG. 3, the long side direction B of the outer shape of the element-isolated light-emitting element structure 18 when viewed from above is a rectangle with a crystal orientation <110> It is assumed that the direction A does not coincide with the direction A of the arrows.

[0079] The method for manufacturing this micro LED structure is as follows: First, the process and structure for manufacturing the bonding substrate (FIGS. 5 to 7) are the same as those in the first embodiment.

[0080] The element isolation process (including the process of forming an SiO2 pattern) (see FIG. 8) is also the same as in the first embodiment, but the shape of the SiO2 pattern is not a square but a rectangle with curved corners (i.e., rounded corners), unlike in the first embodiment. Here, as shown in FIG. 3, the long side direction B of the outline of the element-isolated light-emitting element structure 18 in a plan view is aligned with the crystal orientation <110> In particular, the crystal orientation <110> The direction (direction A) is the line connecting the corner and the diagonal corner. <110> It is preferable that the direction of the insulating film be approximately the same as that of the insulating film 1. The steps (FIGS. 9 to 11) after the element isolation step (including the step of forming the SiO2 pattern) are the same as those in the first embodiment.

[0081] (Fourth embodiment) Next, a fourth embodiment will be described, in which the micro LED structure has a polygonal outer shape in plan view.

[0082] In the fourth embodiment, as shown in Fig. 4, the outer shape of the element-isolated light-emitting element structure 18 in plan view is polygonal (a hexagon that is not a regular hexagon in Fig. 4). Here, as shown in Fig. 4, the long side direction B of the outer shape of the element-isolated light-emitting element structure 18 in plan view is aligned with the crystal orientation <110> It is assumed that the direction A does not coincide with the direction A of the arrows.

[0083] The method for manufacturing this micro LED structure is as follows: First, the process and structure for manufacturing the bonding substrate (FIGS. 5 to 7) are the same as those in the first embodiment.

[0084] The element isolation process (including the process of forming an SiO2 pattern) (see FIG. 8) is also the same as in the first embodiment, but the SiO2 pattern shape is not square but polygonal, unlike in the first embodiment. Here, as shown in FIG. 4, the long side direction B of the outline of the element-isolated light-emitting element structure 18 in a plan view is aligned with the crystal orientation <110> It is assumed that the direction does not coincide with the direction A. The steps (FIGS. 9 to 11) after the element isolation step (including the step of forming the SiO2 pattern) are the same as those in the first embodiment. [Example]

[0085] EXAMPLES The present invention will be described in detail below with reference to examples and comparative examples, but the present invention is not limited thereto.

[0086] Examples and Comparative Examples According to the second embodiment, a micro LED structure 58 having a light emitting element structure 18 was manufactured. That is, as shown in Figure 2, the outline of the isolated light emitting element structure in plan view is rectangular.

[0087] First, an epitaxial wafer having a light emitting device structure as an epitaxial functional layer was prepared as shown in Fig. 5. Specifically, the following procedure was performed: First, an N-type GaAs buffer layer was laminated on an N-type GaAs starting substrate 11, and then a 0.1 µm thick N-type Ga x In 1-x A P (0.4≦x≦0.6) first etch stop layer and a 0.1 μm thick N-type GaAs second etch stop layer were formed to form the etch stop layer 12. On the etch stop layer 12, a 1.0 μm thick N-type (Al y Ga 1-y ) x In 1-x P(0.4≦x≦0.6, 0.6≦y≦1.0) first cladding layer 13, undoped (Al y Ga 1-y ) x In 1-x P(0.4≦x≦0.6, 0≦y≦0.5) active layer 14, 1.0 μm thick P-type (Al y Ga 1-y ) x In 1-x P(0.4≦x≦0.6, 0.6≦y≦1.0) second cladding layer 15, 0.1 μm thick P-type Ga x In 1-x A P(0.5≦x≦1.0) intermediate layer (not shown) and a 6 μm thick P-type GaP window layer 16 were grown in this order to prepare an epitaxial wafer 20 having a light emitting device structure 18 as an epitaxial functional layer (FIG. 5).

[0088] 6, benzocyclobutene (BCB), a thermosetting bonding material, was spin-coated onto the epitaxial wafer 20 as an adhesive or bonding material 25, and then the epitaxial wafer 20 was placed face-to-face with a sapphire wafer, which was a transparent substrate 30, and the two were thermocompression-bonded in a vacuum atmosphere. When applying BCB by spin coating, the designed film thickness was 0.6 μm.

[0089] 7, the GaAs starting substrate 11 was then removed by wet etching to expose the N-type first etch stop layer, and the first and second etch stop layers were then removed with appropriate etchants to expose the first cladding layer 13. This resulted in the fabrication of an epitaxial junction substrate that retains only the DH layer and window layer 16.

[0090] Next, a rectangular SiO2 pattern measuring 50 μm in length and 25 μm in width was formed by P-CVD, photolithography, and wet etching, followed by element isolation to form an island pattern. After the island pattern was formed, a portion of the DH layer was etched by ICP to expose the second cladding layer 15 (FIG. 8). Then, an SiO2 protective film 52 was formed on the processed cross section (FIG. 9). Then, as shown in FIGS. 2 and 10, a first electrode 54 and a second electrode 56 with opposite polarities were arranged near the ends in the long axis direction in plan view. A micro LED structure 58 was fabricated in this manner. A plurality of epitaxial junction substrates were fabricated, and the micro LED structure 58 was fabricated by arranging the epitaxial junction substrates in the long side direction B and the crystal orientation <110> The angle of the direction A was set to 0° (comparative example), 5°, 10°, 15°, 20°, 25°, 30°, 35°, 40°, and 45° (examples). <110> It is formed in approximately the same direction.

[0091] The micro LED structures 58 manufactured in each of the examples and comparative examples were transferred onto a transfer substrate 70 as shown in FIG.

[0092] The results of the example and the comparative example are shown in Fig. 12. The direction of the long side of the outline of the light emitting device structure in plan view is the crystal orientation. <110> In the case of a comparative example, when the shape is roughly the same as the crystal orientation, the die cracking rate is about 30%. <110> The cracking rate decreased when the crystal was tilted from the center, and reached zero when the angle was 10 degrees or more. <110> Since the upper limit of the angle of inclination from is 45°, 45° is the upper limit of the inclination.

[0093] The present specification includes the following aspects. [1]: (Al y Ga 1-y ) x In 1-x A micro LED structure having a light emitting element structure having P (0.4≦x≦0.6, 0≦y≦0.5) as an active layer, the light emitting element structure being bonded to a transparent substrate that is transparent to the emission wavelength and the laser light for LLO transfer with an adhesive or bonding material that is transparent to the emission wavelength and absorbs the laser light for LLO transfer, The light-emitting device structure is isolated from other elements, The light-emitting element structure is isolated from the other element and has at least two electrodes of different polarities on one surface thereof, The direction of the long side of the outline of the separated light emitting element structure in plan view is a crystal orientation <110> A micro LED structure characterized in that it does not match. [2]: The direction of the long side of the outline of the light-emitting element structure in a plan view is the crystal orientation <110> The micro LED structure of [1] above is offset by a range of 10° to 45°. [3]: The direction of the long side of the outline of the light-emitting element structure in a plan view is the crystal orientation <110> The micro LED structure of [2] above is offset by a range of 22.5° to 30°. [4]: The micro LED structure according to any one of [1] to [3] above, wherein the light-emitting element structure does not have a starting substrate. [5]: The micro LED structure according to any one of [1] to [4], wherein the adhesive or bonding material is benzocyclobutene. [6]: The micro LED structure according to any one of [1] to [5] above, wherein the transparent substrate is sapphire or quartz. [7]: On the starting substrate, (Al y Ga 1-y ) x In 1-x forming a light-emitting device structure having P(0.4≦x≦0.6, 0≦y≦0.5) as an active layer; a step of bonding the light emitting element structure to a transparent substrate that is transparent to the emission wavelength of the light emitting element structure and the laser light for LLO transfer using an adhesive or bonding material that is transparent to the emission wavelength and absorbs the laser light for LLO transfer; isolating the light emitting device structure; forming at least two electrodes having different polarities on one surface of the isolated light emitting element structure; 1. A method for manufacturing a micro LED structure by: In the element isolation step, the direction of the long side of the outline of the isolated light emitting element structure in plan view is determined to be along a crystal orientation <110> A method for manufacturing a micro LED structure, characterized in that: [8]: The direction of the long side of the outline of the light-emitting element structure in a plan view is the direction of the crystal orientation. <110> The manufacturing method of the micro LED structure of [7] above, wherein the offset is in the range of 10° to 45°. [9]: The direction of the long side of the outline of the light-emitting element structure in a plan view is the direction of the crystal orientation <110> The manufacturing method of the micro LED structure of [8] above, wherein the offset is in the range of 22.5° to 30°.

[10] : The method for manufacturing a micro LED structure according to any one of [7] to [9] above, further comprising the step of removing the starting substrate.

[11] : The method for manufacturing a micro LED structure according to any one of [7] to

[10] above, wherein the adhesive or bonding material is benzocyclobutene.

[12] : The method for manufacturing a micro LED structure according to any one of [7] to

[11] above, wherein the transparent substrate is made of sapphire or quartz.

[0094] The present invention is not limited to the above-described embodiments. The above-described embodiments are merely examples, and anything that has substantially the same configuration as the technical idea described in the claims of the present invention and that exhibits similar effects is included within the technical scope of the present invention. [Explanation of symbols]

[0095] 11...Starting substrate, 12...etch stop layer, 13...first cladding layer, 14...active layer, 15...second cladding layer, 16...Window layer, 18...Light emitting element structure, 19...light-emitting layer region, 20... epitaxial wafer, 25...adhesives or bonding materials, 30...Transparent substrate, 47...Element isolation trench, 52...protective film, 54...first electrode, 56...second electrode, 57...Stepped part, 58...Micro LED structure, 65...Silicone resin, 70...Transferred board, A...Crystal orientation <110> direction, B...long side direction.

Claims

1. (Al ｙ Ga １－ｙ ) ｘ In １－ｘ A micro LED structure having a light emitting element structure having P (0.4≦x≦0.6, 0≦y≦0.5) as an active layer, the light emitting element structure being bonded to a transparent substrate that is transparent to the emission wavelength and laser light for LLO transfer using an adhesive or bonding material that is transparent to the emission wavelength and absorbs the laser light for LLO transfer, The light-emitting device structure is isolated from other elements, The light-emitting element structure separated into elements has at least two electrodes of different polarities on one surface, A micro LED structure characterized in that the long side direction of the outline of the element-separated light-emitting element structure when viewed in a plane does not coincide with the crystal orientation <110>.

2. The micro LED structure according to claim 1, characterized in that the long side direction of the outline of the light emitting element structure in a planar view is shifted from the crystal orientation <110> by 10° to 45°.

3. The micro LED structure according to claim 2, characterized in that the long side direction of the outline of the light-emitting element structure in a planar view is deviated from the crystal orientation <110> by 22.5° to 30°.

4. 3. The micro LED structure of claim 1, wherein the light emitting device structure does not have a starting substrate.

5. 3. The micro LED structure of claim 1 or claim 2, wherein the adhesive or bonding material is benzocyclobutene.

6. 3. The micro LED structure of claim 1 or claim 2, wherein the transparent substrate is sapphire or quartz.

7. On the starting substrate, (Al ｙ Ga １－ｙ ) ｘ In １－ｘ forming a light-emitting device structure having P (0.4≦x≦0.6, 0≦y≦0.5) as an active layer; a step of bonding the light emitting element structure to a transparent substrate that is transparent to the emission wavelength of the light emitting element structure and the laser light for LLO transfer using an adhesive or bonding material that is transparent to the emission wavelength and absorbs the laser light for LLO transfer; isolating the light emitting device structure; forming at least two electrodes having different polarities on one surface of the isolated light emitting element structure; 1. A method of manufacturing a micro LED structure by: A method for manufacturing a micro LED structure, characterized in that, in the element isolation step, the direction of the long side of the outline of the isolated light-emitting element structure in a planar view is not aligned with the crystal orientation <110>.

8. 8. The method for manufacturing a micro LED structure according to claim 7, wherein the direction of the long side of the outer shape of the light-emitting element structure in a planar view is shifted from the crystal orientation <110> by 10° to 45°.

9. 9. The method for manufacturing a micro LED structure according to claim 8, wherein the direction of the long side of the outer shape of the light-emitting element structure in a planar view is shifted from the crystal orientation <110> by 22.5° to 30°.

10. 9. A method for manufacturing a micro LED structure according to claim 7 or claim 8, further comprising the step of removing the starting substrate.

11. 9. A method for manufacturing a micro LED structure according to claim 7 or 8, characterized in that the adhesive or bonding material is benzocyclobutene.

12. 9. The method of claim 7 or 8, wherein the transparent substrate is sapphire or quartz.

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