Micro LED structural body and manufacturing method thereof

Abstract

The present invention is a Micro LED structure having a light-emitting element structure having (AlyGa1-y) xIn1-xP (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 light-emitting wavelength and to the laser light for LLO transfer using an adhesive or bonding material that is transparent to the light-emitting wavelength and that absorbs the laser light for LLO transfer, the Micro LED structure is characterized in that the light-emitting element structure is element-separated, the element-separated light-emitting element structure has at least two electrodes having different polarities on one surface, and the long-side direction and the crystal orientation of the outer shape of the element-separated light-emitting element structure are viewed in plan view; 110gt, 110gt; and inconsistency. As a result, it is possible to provide a Micro LED structure in which a light-emitting element structure having an AlGaInP-based active layer and a transparent substrate are bonded via an adhesive or a bonding agent, and in which cracking of the Micro LED structure can be reduced or avoided when the light-emitting element structure and the transparent substrate are transferred by an LLO step.

Description

Technical Field

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

[0002] In order to realize a Micro LED Display, a technique has been disclosed in which an LED is peeled off from a starting substrate by laser lift-off (LLO) and transferred to a packaging substrate and then to a driving substrate (Patent Document 1). However, these techniques are only applicable to GaN-based LEDs, and there is still little disclosure of techniques for MicroLED (μ-LED) using AlGaInP-based LEDs.

[0003] In the case of AlGaInP-based LEDs, in order to realize a Micro LED element through the LLO process, it is necessary to transfer to a substrate that is transparent to the LLO laser, such as a sapphire substrate. Regarding the technique of transferring AlGaInP-based LEDs to a sapphire substrate, for example, there are disclosures of prior art such as Patent Document 2.

[0004] Prior Art Documents

[0005] Patent Documents

[0006] Patent Document 1: Japanese Patent Application Laid-Open No. 2020-521181.

[0007] Patent Document 2: Japanese Patent Application Laid-Open No. 2022-013203.

[0008] Patent Document 3: Japanese Patent Application Laid-Open No. 2016-004892.

[0009] Patent Document 4: Japanese Patent Application Laid-Open No. 2007-242804.

[0010] Patent Document 5: Japanese Patent Application Laid-Open No. 2015-084448. Summary of the Invention

[0011] (1) Technical Problem to be Solved

[0012] However, compared with GaN-based LEDs, AlGaInP-based LEDs are mechanically more fragile, and there is a problem that chip cracking is likely to occur during the LLO process depending on the appropriateness of the die design. There is no technique for avoiding the cracking of the Micro LED structure (also referred to as "μ-LED chip cracking") during the LLO process.

[0013] Furthermore, the thickness of the Micro LED is relatively thin, so it is weaker in terms of stress compared to conventional LEDs. According to the research of the inventors of the present application, due to such low strength, the following situation is known to occur: when the element is pressed onto the transfer substrate during the LLO process, in order to attach electrodes with different polarities, stress is applied to the step portion where the element is provided. If the step extension direction is substantially consistent with the crystal orientation <110> in the top view of the step, it is very easy to break due to the cleavage of the crystal.

[0014] In addition, Patent Document 3 discloses chipping prevention in the dicing process during the formation of conventional-sized LED chips, rather than chip cracking during the transfer of such Micro LEDs. In this Patent Document 3, in the dicing of conventional-sized LEDs, dicing is performed in such a way that the dicing predetermined line is offset from the crystal orientation <110>. However, Patent Document 3 discloses a technique for preventing chipping during the dicing process of conventional-sized LEDs, rather than a technique for chip cracking during the transfer of Micro LEDs in the LLO process.

[0015] Furthermore, as an existing technique for adjusting the chip angle, there is Patent Document 4. This technique is for adjusting the angle of the growth direction, rather than a technique for chip cracking during the transfer of Micro LEDs in the LLO process.

[0016] Patent Document 5 discloses a technique for arranging device functional parts in a manner offset from the crystal orientation <110>. However, Patent Document 5 is not a technique for chip cracking during the transfer of Micro LEDs in the LLO process.

[0017] From the above perspectives, there is no technical disclosure on avoiding chip cracking of Micro LED chips during the LLO process.

[0018] The present invention is made in view of the above technical problems, and its object is to provide a Micro LED structure and a manufacturing method thereof. In the Micro LED structure formed by bonding a light-emitting element structure having an AlGaInP-based active layer and a transparent substrate with an adhesive or bonding agent, when transferred through the LLO process, the cracking of the Micro LED structure can be reduced or avoided.

[0019] (II) Technical Solution

[0020] The present invention is made to achieve the above object, and it provides a Micro LED structure having (Al y Ga 1-y ) x In1-x A light-emitting element structure with P(0.4≤x≤0.6, 0≤y≤0.5) as the active layer is bonded to a transparent substrate that is transparent to the emission wavelength and absorbs the laser for LLO transfer using an adhesive or bonding material that is transparent to the emission wavelength and the laser for LLO transfer. The Micro LED structure is characterized in that the light-emitting element structure is element-separated, and the element-separated light-emitting element structure has at least two electrodes with different polarities on one surface, and the long side direction of the outer shape when the element-separated light-emitting element structure is observed from above does not coincide with the crystal orientation <110>.

[0021] Generally, the mechanical strength of a Micro LED structure having an AlGaInP-based active layer is low. However, in the Micro LED structure of the present invention described above, it is possible to prevent a portion with particularly low structural strength from being easily broken due to the cleavage property of the crystal. As a result, it is possible to reduce or avoid the breakage (chip breakage, damage) of the Micro LED structure when the Micro LED structure is transferred in the LLO process.

[0022] At this time, it is preferable that the long side direction of the outer shape when the light-emitting element structure is observed from above is offset from the crystal orientation <110> in a range of 10° or more and 45° or less.

[0023] In addition, at this time, it is preferable that the long side direction of the outer shape when the light-emitting element structure is observed from above is offset from the crystal orientation <110> in a range of 22.5° or more and 30° or less.

[0024] As long as it is such an angle, it is possible to set the long side direction of the outer shape when the light-emitting element structure is observed from above to an angle that is not only away from the crystal orientation <110> but also away from the <110> orientation with easy breakage. Therefore, it is possible to more effectively reduce and improve the proportion of breakage (chip breakage, damage) of the Micro LED structure generated during the LLO process.

[0025] In addition, it is preferable that the light-emitting element structure in the Micro LED structure of the present invention does not have a starting substrate.

[0026] In this way, by making the light-emitting element structure not have a starting substrate, it is possible to perform the transfer to a desired transfer substrate.

[0027] In addition, it is preferable that the adhesive or bonding material is benzocyclobutene.

[0028] In this way, by using benzocyclobutene as the adhesive or bonding material, it is possible to surely perform the LLO process by excimer laser.

[0029] In addition, it is preferable that the transparent substrate is sapphire or quartz.

[0030] As the transparent substrate, the above-mentioned substrates can be applied, and in particular, a substrate with high penetrability for the LLO laser can be selected.

[0031] In addition, the present invention provides a method for manufacturing a Micro LED structure, which manufactures a Micro LED structure by the following processes: forming a light-emitting element structure having (Al y Ga 1-y ) x In 1-x P (0.4 ≤ x ≤ 0.6, 0 ≤ y ≤ 0.5) as an active layer on a starting substrate; bonding the light-emitting element structure to a transparent substrate that is transparent to the emission wavelength of the light-emitting element structure using an adhesive or a bonding material; separating the light-emitting element structure into elements; and forming at least two electrodes with different polarities on one surface of the light-emitting element structure separated into elements. The manufacturing method is characterized in that, in the process of separating the elements, the long side direction of the outer shape of the light-emitting element structure separated into elements when viewed from above is set to be inconsistent with the crystal orientation <110>.

[0032] If it is such a method for manufacturing a Micro LED structure, it is possible to prevent a portion with particularly low structural strength of the manufactured Micro LED structure from being easily broken due to the cleavage of the crystal. As a result, it is possible to reduce or avoid the breakage (damage) of the Micro LED structure when transferring the Micro LED structure in the LLO process.

[0033] At this time, it is preferable that the long side direction of the outer shape of the light-emitting element structure when viewed from above is offset from the crystal orientation <110> in a range of 10° or more and 45° or less.

[0034] Furthermore, at this time, the long side direction of the outer shape of the light-emitting element structure when viewed from above can be offset from the crystal orientation <110> in a range of 22.5° or more and 30° or less.

[0035] By separating the elements with the long side direction of the outer shape of the light-emitting element structure viewed from above offset from the crystal orientation <110> at such an angle, it is possible to more effectively reduce and improve the proportion of breakage of the Micro LED structure generated during the LLO process.

[0036] In addition, it is preferable that in the method for manufacturing a Micro LED structure of the present invention, a process of removing the starting substrate is further included.

[0037] Thus, by removing the starting substrate, the transfer to the desired transfer substrate can be performed.

[0038] In addition, it is preferable that the adhesive or bonding material is benzocyclobutene.

[0039] Thus, by using benzocyclobutene as the adhesive or bonding material, the LLO process using excimer laser can be surely carried out.

[0040] In addition, it is preferable that the transparent substrate is sapphire or quartz.

[0041] As the transparent substrate, these substrates can be applied, and in particular, a substrate with high penetrability for the LLO laser can be selected.

[0042] (III) Beneficial effects

[0043] Generally, the mechanical strength of a Micro LED structure having an AlGaInP-based active layer is low. In view of this, the Micro LED structure of the present invention can prevent the parts with particularly low structural strength from being easily broken due to the cleavage of the crystal. Therefore, according to the present invention, the breakage (chip breakage, damage) of the Micro LED structure during the transfer of the Micro LED structure in the LLO process can be reduced or avoided. In addition, the manufacturing method of the Micro LED structure of the present invention can manufacture such a Micro LED structure. Description of the drawings

[0044] Figure 1 It is a schematic diagram when observing an example (first embodiment) of the Micro LED structure of the present invention from above.

[0045] Figure 2 It is a schematic diagram when observing another example (second embodiment) of the Micro LED structure of the present invention from above.

[0046] Figure 3 It is a schematic diagram when observing another example (third embodiment) of the Micro LED structure of the present invention from above.

[0047] Figure 4 It is a schematic diagram when observing another example (fourth embodiment) of the Micro LED structure of the present invention from above.

[0048] Figure 5 It is a schematic cross-sectional view showing a part of the manufacturing method of the Micro LED structure of the present invention.

[0049] Figure 6It is a schematic cross-sectional view showing another part of the manufacturing method of the Micro LED structure of the present invention.

[0050] Figure 7 It is a schematic cross-sectional view showing another part of the manufacturing method of the Micro LED structure of the present invention.

[0051] Figure 8 It is a schematic cross-sectional view showing another part of the manufacturing method of the Micro LED structure of the present invention.

[0052] Figure 9 It is a schematic cross-sectional view showing another part of the manufacturing method of the Micro LED structure of the present invention.

[0053] Figure 10 It is a schematic cross-sectional view showing another part of the manufacturing method of the Micro LED structure of the present invention.

[0054] Figure 11 It is a schematic cross-sectional view showing a part of the method of transferring the Micro LED structure of the present invention to a transfer substrate after manufacturing.

[0055] Figure 12 It is a chart showing the results of the examples and comparative examples. Detailed Description of the Invention

[0056] The Micro LED structure of the present invention has a light-emitting element structure with (Al y Ga 1-y ) x In 1-x P (0.4 ≤ x ≤ 0.6, 0 ≤ y ≤ 0.5) as the active layer. The light-emitting element structure is bonded to a transparent substrate that is transparent to the emission wavelength and absorbs the laser for LLO transfer using an adhesive or bonding material that is transparent to the emission wavelength and the laser for LLO transfer. The Micro LED structure is characterized in that the light-emitting element structure is element-separated, and the element-separated light-emitting element structure has at least two electrodes with different polarities on one surface, and the long side direction of the outer shape when the element-separated light-emitting element structure is viewed from above does not coincide with the crystal orientation <110>. As the Micro LED structure, it can be set to have a side length exceeding 100 μm.

[0057] Hereinafter, the present invention will be described in detail with reference to the drawings, but the present invention is not limited thereto. Hereinafter, the first embodiment to the fourth embodiment will be exemplified to describe the solution of the present invention. Similar elements in each embodiment are denoted by the same reference numerals for description.

[0058] (First Embodiment)

[0059] First, the first embodiment will be described. In this first embodiment, the outer shape of the Micro LED structure is square when viewed from above.

[0060] The Micro LED structure of the present invention can be manufactured, for example, through the processes described later ( Figures 5 to 10 ). Among them, reference is made to Figure 10 or reference is made to Figure 1 to describe the Micro LED structure of the present invention.

[0061] As shown in the schematic cross-sectional view Figure 10 the Micro LED structure 58 of the present invention has a light-emitting element structure 18 with (Al y Ga 1-y ) x In 1-x P (0.4 ≤ x ≤ 0.6, 0 ≤ y ≤ 0.5) as the active layer 14. In addition, the light-emitting element structure 18 is bonded to a transparent substrate 30 that is transparent to the emission wavelength and absorbs the laser for LLO transfer using an adhesive or bonding material 25. In addition, the light-emitting element structure 18 is separated into elements through element separation grooves (element separation grooves 47 formed in Figure 8 described later). The element-separated light-emitting element structure 18 has at least two electrodes 54 and 56 with different polarities on one surface. In addition, as shown in the schematic view for top-down observation Figure 1 , when the element-separated light-emitting element structure 18 is viewed from above, the long side direction B of the outer shape is not parallel to the direction A of the crystal orientation <110>.

[0062] In the present invention, as described above, the positional relationship (angular relationship) between the long side direction of the outer shape of the element-separated light-emitting element structure when viewed from above and the <110> crystal orientation direction is defined. The long side of this outer shape is the longest side. The first embodiment is the case where the outer shape of the Micro LED structure is square when viewed from above. Figure 1 shows a Micro LED structure 58 having a light-emitting element structure 18 separated into a square. The long side (the longest side) of the square has two orthogonal directions, and it is assumed that the <110> crystal orientation direction is offset with respect to any long side.

[0063] Figure 1 In, as the two electrodes 54 and 56 with different polarities, the first electrode 54 is represented as the upper electrode, and the second electrode 56 is represented as the second electrode. Figure 1 The light-emitting layer region 19 shown in shows the region including the active layer 14 when viewed from above. From Figure 1 and Figure 10From the comparison, the first electrode 54 is located on layer 13. In addition, the second electrode is located on layer 15. As will be described later, Figure 10 Layer 13 is of the first conductivity type, and layers 15 and 16 are of the second conductivity type. Therefore, a step portion 57 is provided to set electrodes with different polarities on each layer. When the element is pressed onto the transfer substrate during the LLO process, stress is applied to this step portion 57. If the direction along this step portion 57 is aligned with the crystal orientation <110>, it is very likely to break due to the cleavage of the crystal. On the other hand, in the present invention, the step portion 57 has high strength and can be made into a member that is not easily broken. Compared with GaN-based LEDs, AlGaInP-based LEDs are mechanically more fragile and are likely to cause chip breakage during the LLO process depending on the appropriateness of the chip design. Therefore, the effect of suppressing chip breakage brought by the present invention is very large.

[0064] At this time, it is preferable that the long side direction of the outer shape when observing the light-emitting element structure 18 from above is offset from the crystal orientation <110> (direction A) in a range of 10° or more and 45° or less. In addition, the long side direction of the outer shape when observing the light-emitting element structure 18 from above can be set to be offset from the crystal orientation <110> (direction A) in a range of 22.5° or more and 30° or less.

[0065] Furthermore, as Figure 10 shown, in the Micro LED structure 58 of the present invention, it is preferable that the light-emitting element structure 18 does not have a starting substrate. By the light-emitting element structure 18 not having a starting substrate, transfer to a desired transfer substrate can be performed. The fact that the light-emitting element structure 18 does not have a starting substrate can be achieved by removing the starting substrate 11 as described later (refer to Figure 6 , Figure 7 ).

[0066] In addition, it is preferable that: in the Micro LED structure 58 of the present invention, the adhesive or bonding material 25 is benzocyclobutene (BCB). By using benzocyclobutene as the adhesive or bonding material, the LLO process by excimer laser can be surely carried out

[0067] In addition, it is preferable that: in the Micro LED structure 58 of the present invention, the transparent substrate 30 is sapphire or quartz. As the transparent substrate, these substrates can be applied, and in particular, a substrate with high penetrability for LLO laser can be selected.

[0068] Next, the manufacturing method of such a Micro LED structure of the present invention will be described. In the first embodiment, the case of manufacturing the Micro LED structure 58 having the Figure 1 shown top view outer shape will be described.

[0069] First, form one having (Al yGa 1-y ) x In 1-x A light-emitting element structure with P(0.4 ≤ x ≤ 0.6, 0 ≤ y ≤ 0.5) as the active layer. Therefore, as Figure 5 shown, epitaxial growth is sequentially performed on the starting substrate 11 to form each layer, and an epitaxial wafer 20 is fabricated. Thus, an etch stop layer 12 or an epitaxial layer having a light-emitting element structure 18 is fabricated. More specifically, epitaxial growth of each layer can be performed as follows.

[0070] In this process, first, as Figure 5 shown, the etch stop layer 12 is epitaxially grown on the first conductive type GaAs substrate 11 serving as the starting substrate. The etch stop layer 12 can be formed, for example, by stacking a first conductive type GaAs buffer layer and then growing a first conductive type Ga x In 1-x P(0.4 ≤ x ≤ 0.6) first etch layer to a thickness of, for example, 0.1 μm and growing a first conductive type GaAs second etch layer to a thickness of, for example, 0.1 μm. Further, an epitaxial wafer 20 having a light-emitting element structure 18 as an epitaxial functional layer is prepared, and the following layers are sequentially grown on the etch stop layer 12 for this epitaxial functional layer: for example, a 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 13 with a thickness of, for example, 1.0 μm, an undoped (Al y Ga 1-y ) x In 1-x P(0.4 ≤ x ≤ 0.6, 0 ≤ y ≤ 0.5) active layer 14, a 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 15 with a thickness of, for example, 1.0 μm, a second conductive type Ga x In 1-x P(0.5 ≤ x ≤ 1.0) intermediate layer (not shown) with a thickness of, for example, 0.1 μm, and a second conductive type GaP window layer 16. Here, the first cladding layer 13 to the second cladding layer 15 are referred to as a double heterostructure (DH) section ( Figure 5 ).

[0071] The film thickness described above is only an example, and the film thickness is only a parameter that should be changed according to the operating specifications of the device. Therefore, it goes without saying that it is not limited to the film thickness described here. The case where both the first cladding layer 13 and the second cladding layer 15 are 1.0 μm is illustrated. However, in Micro LEDs, even if the rated current density is smaller than that of large-sized discrete LEDs and the film thickness is thinner than this, the function as a cladding layer will not be impaired.

[0072] In addition, as will be described later, the first cladding layer 13 forms an electrode in a state where it is in contact with the first cladding layer 13. Therefore, considering the metal diffusion during the formation of an ohmic contact, it is suitable to have a thickness of 0.6 μm or more. As long as it is above this thickness, any thickness can be selected. However, the first cladding layer 13 is preferably designed in the range of 10 μm or less. As long as it is such a thickness, it will not only not be the main cause of cost increase, but also ensure the luminous efficiency during rated current driving, and can also suppress the warping of the wafer, thereby enabling a high yield.

[0073] When the second cladding layer is P-type, the effective mass of holes is large. Therefore, even if the thickness of the second cladding layer 15 is, for example, about 0.2 μm, it can still act in the same way as 1.0 μm. Therefore, a thickness of 0.2 μm or more is preferred, and any such thickness can be selected. However, the second cladding layer 15 is preferably designed in the range of 10 μm or less. As long as it is such a thickness, it will not only not be the main cause of cost increase, but also ensure the luminous efficiency during rated current driving, and can also suppress the warping of the wafer, thereby enabling a high yield.

[0074] In addition, it goes without saying that each layer is not a single constituent layer, but also includes the concept of having multiple constituent layers within the illustrated compositional range. In addition, the level of carrier concentration is not uniform in each layer, but includes the concept of having multiple levels within each layer, which goes without saying.

[0075] The active layer 14 can be composed of a single composition, and can also be a superlattice structure in which a barrier layer and an active layer are alternately stacked in multiple layers. Both have similar functions, and either one can be selected. Whichever structure is selected, the effects of the present invention are still the same.

[0076] In addition, the thickness of the GaP window layer 16 is preferably more than 5 μm, and can be set to 6 μm, for example. However, it is not limited to this 6-μm thickness. For example, as long as the film thickness is within the range thinner than the short side length of the device separation, any film thickness can be selected.

[0077] Next, as Figure 6As shown, a light-emitting element structure 18 is bonded to a transparent substrate 30 that is transparent to the emission wavelength and absorbs the laser for LLO transfer using an adhesive or bonding material 25. For example, a thermosetting bonding member such as benzocyclobutene (BCB) as the adhesive or bonding material 25 is spin-coated on the epitaxial wafer 20, and is laminated facing a transparent substrate 30 such as a sapphire wafer, and thermocompression bonding is performed in a vacuum atmosphere. When BCB is coated by spin coating, the film thickness can be set to, for example, 0.6 μm.

[0078] In addition, the atmosphere for thermocompression bonding is not limited to a vacuum atmosphere. As long as the oxygen content is 100 ppm or less, any atmosphere can be adopted. For example, the same effect can be obtained even in a nitrogen atmosphere or an argon atmosphere.

[0079] In addition, the transparent substrate 30 is not limited to sapphire. As long as laser penetrability and flatness can be ensured, any material can be selected. In addition to sapphire, quartz can also be selected.

[0080] In addition, when using BCB as the adhesive or bonding material 25, the same result can be obtained even if BCB is patterned into isolated islands or lines or other shapes using photosensitive BCB in addition to being coated in a layer form and the bonding process is performed.

[0081] In addition, the film thickness of the adhesive or bonding material 25 such as BCB is not limited to 0.6 μm, and it can also be thinner than this thickness.

[0082] Subsequently, as Figure 7 shown, it is preferable to remove the starting substrate 11 (for example, a GaAs substrate) by wet etching. Further, the etching stop layer 12 is also removed later. When removing the etching stop layer 12, when there are a first etching stop layer and a second etching stop layer as described above, first, the first etching stop layer is exposed by etching, and the etching agent is changed to remove the second etching stop layer, so that the epitaxial layer (the first cladding layer 13 in the light-emitting element structure 18) can be exposed. By operating in this way, a bonded wafer that only holds the double heterostructure (DH) part (the first cladding layer 13, the active layer 14, the second cladding layer 15) and the window layer 16 can be fabricated ( Figure 7 ).

[0083] After that, as Figure 8 shown, the light-emitting element structure 18 is separated into elements. At this time, the long side direction B of the outer shape of the element-separated light-emitting element structure 18 when viewed from above is not aligned with the direction A of the crystal orientation <110> (refer to Figure 1 ). Specifically, the element separation can be operated in the following manner, but as long as element separation can be performed, it is not limited to the following manner.

[0084] First, a 1-μm-thick SiO2 film is formed on the epitaxial wafer (i.e., on the first cladding layer 13) by using a P-CVD method (plasma CVD method) with TEOS (tetraethoxysilane) and O2 as raw materials.

[0085] Subsequently, a resist pattern is formed by photolithography, and a pattern shape of SiO2 is fabricated by wet etching with hydrofluoric acid. Subsequently, using the SiO2 pattern as a hard mask, ICP processing is performed using an ICP (Inductively Coupled Plasma) apparatus into which a chlorine-based gas is introduced, and the DH structure part (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 the BCB layer. The etching gas is switched to further dry-etch the exposed adhesive or bonding material 25 to expose the sapphire substrate, and an island pattern composed of the DH structure part (from the first cladding layer 13 to the second cladding layer 15) and the GaP window layer 16 is formed. The island pattern here is substantially the same as the above-mentioned SiO2 pattern.

[0086] The SiO2 pattern here, that is, the shape (the above-mentioned island pattern) that becomes the outer shape when the light-emitting element structure is observed from above after element isolation, preferably has a side length of less than 100 μm. In the present embodiment, this shape is a substantially square. In the present embodiment, this substantially square pattern is preferably formed such that the line connecting the corner points and their diagonals is substantially parallel to the <110> crystal direction (refer to Figure 1 ).

[0087] In this way, the line connecting the corner points and their diagonals of the SiO2 pattern (i.e., the shape that becomes the outer shape when the light-emitting element structure is observed from above after element isolation) is substantially parallel to the <110> crystal direction (direction A). However, even if it is not strictly parallel to the <110> direction, the same effect can still be obtained, which goes without saying. It is important that the sides of the SiO2 pattern are not substantially parallel to the <110> crystal direction. By shifting the direction of the sides by more than 10° from the <110> crystal direction, this effect can be obtained more surely. The maximum value of the angle formed by the line connecting the diagonals and the <110> crystal direction is 45°, so the maximum angle is 45°. That is, as Figure 1 shown, it is preferable that the long side direction B of the outer shape when the light-emitting element structure 18 after element isolation is observed from above is shifted from the <110> crystal direction A by a range of more than 10° and less than 45°. In addition, in particular, the long side direction B of the outer shape when the light-emitting element structure 58 after element isolation is observed from above can be shifted from the <110> crystal direction A by a range of more than 22.5° and less than 30°.

[0088] Subsequently, as Figure 8As shown in [figure], step portions for forming electrodes are provided in each light-emitting element structure after element separation. Specifically, after forming the above-described island pattern, a part of the double heterostructure (DH) portion (first cladding layer 13, active layer 14, second cladding layer 15) is etched using the same ICP method as described above to expose the second cladding layer 15 or the GaP window layer 16.

[0089] Figure 8 After the element separation process (and the exposure of the second cladding layer 15 or the GaP window layer 16) shown in [figure], as Figure 9 shown in [figure], a protective film 52 can be formed as an end face treatment on the processed cross-section. Here, for example, a SiO2 protective film can be formed as the protective film 52 using the same P-CVD method as described above. In addition, 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. SiN x or titanium oxide, magnesium oxide, etc. can also be selected.

[0090] Subsequently, as Figure 10 shown in [figure], at least two electrodes with different polarities are formed on one surface of the light-emitting element structure 18 after element separation. The so-called "one surface" here can be set to the side opposite to the side bonded to the transparent substrate 30 by an adhesive or a bonding material 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 manufacture a Micro LED structure 58 (also referred to as a "μ-LED chip").

[0091] When the first conductivity type is P-type, it is preferable to select a metal in which the first electrode 54 contains Be or Zn on the surface in contact with the first cladding layer 13, and the second electrode 56 contains Si or Ge on the surface in contact with the second cladding layer 15 or the GaP window layer 16. When the first conductivity type is N-type, it is preferable to select a metal in which the first electrode 54 contains Si or Ge on the surface in contact with the first cladding layer 13, and the second electrode 56 contains Be or Zn on the surface in contact with the second cladding layer 15 or the GaP window layer 16. For example, when the first conductivity type is selected as N-type and the second conductivity type is selected as P-type, an AuSi-based alloy can be used on the surface where the first electrode 54 is in contact with the first cladding layer 13, and an AuBe-based alloy can be used on the surface where the second electrode 56 is in contact with the second cladding layer 15 or the GaP window layer 16.

[0092] In this embodiment, the total thickness of the first electrode 54 and the second electrode 56 can be set to about 0.5 μm respectively, but any film thickness can be selected as long as an ohmic contact can be formed. In addition, even if an additional metal layer, such as an Au or Al underlayer, various Au-based bumps, is formed on either or both of the first electrode 54 and the second electrode 56, the same effect can be obtained.

[0093] In addition, in order to align with the height of the first electrode 54, an additional cushion layer can be provided on the second electrode 56. For example, when the second electrode 56 is in contact with the GaP window layer 16 and a step difference of about several μm (e.g., set to 2.5 μm) is generated between the first electrode 54 and the second electrode 56, in order to align the heights, a pad electrode made of Au with a thickness of several μm (e.g., set to 2.5 μm) can be additionally fabricated.

[0094] As Figure 11 shown, the Micro LED structure fabricated by such an operation presses the pattern of the Micro LED structure onto a transfer substrate 70 composed of a pattern of a Micro LED structure (μ-LED chip) and a silicone convex pattern (silicone resin 65) integrated with a pitch and quartz, etc., and then excimer laser is irradiated from the side of a transparent substrate 30 such as sapphire to sublime an adhesive or bonding material 25 such as BCB. By sublimating the adhesive or bonding material 25 such as BCB, the μ-LED chip is separated from the transparent substrate 30 such as sapphire, and thus, the Micro LED chip is transferred from the transparent substrate 30 such as sapphire to the transfer substrate 70 composed of quartz, etc.

[0095] (Second Embodiment)

[0096] Next, the second embodiment will be described. In this second embodiment, the outer shape of the Micro LED structure is rectangular when viewed from above.

[0097] In the second embodiment, as Figure 2 shown, the outer shape of the light-emitting element structure 18 after element separation is rectangular when viewed from above. Here, as Figure 2 shown, the long side direction B of the outer shape of the light-emitting element structure 18 after element separation is set to be inconsistent with the direction A of the crystal orientation <110>.

[0098] The method of manufacturing this Micro LED structure is as follows. First, the process and structure of fabricating the bonding substrate ( Figures 5 to 7 ) are the same as those in the first embodiment.

[0099] The process of element separation (including the process of forming the SiO2 pattern) (refer to Figure 8 ) is also the same as that in the first embodiment, but the shape of the SiO2 pattern is different from that in the first embodiment. It is rectangular instead of square. Here, as Figure 2As shown, the long side direction B of the outer shape of the light-emitting element structure 18 after element separation when viewed from above is set to be inconsistent with the direction A of the crystal orientation <110>. In particular, in the direction of the crystal orientation <110> (direction A), it is preferable that the line connecting the corner point and its diagonal is substantially consistent with the <110> direction. The processes after the element separation process (including the process of forming the SiO2 pattern) ( Figures 9 to 11 ) are the same as those in the first embodiment.

[0100] (Third Embodiment)

[0101] Next, the third embodiment will be described. As Figure 3 shown, in this third embodiment, when the outer shape of the light-emitting element structure 18 after element separation is viewed from above, it is rectangular, and each side of the rectangle is substantially straight, but has a curve at the corner (that is, the corner has an R). That is, this third embodiment is a modified pattern of the second embodiment, and is a case where the corners of the rectangle are not 90°. At this time, the long side refers to the longest straight line. The fact that the corners can have an R is not limited to rectangles, and is the same in the case of a square of Figure 1 and the case of a polygon of Figure 4 described later, etc. Here, as Figure 3 shown, the long side direction B of the outer shape of the light-emitting element structure 18 after element separation when viewed from above is set to be inconsistent with the direction A of the crystal orientation <110>.

[0102] The method for manufacturing this Micro LED structure is as follows. First, the process and structure of manufacturing the bonding substrate ( Figures 5 to 7 ) are the same as those in the first embodiment.

[0103] The element separation process (including the process of forming the SiO2 pattern) (refer to Figure 8 ) is also the same as that in the first embodiment, but the shape of the SiO2 pattern is different from that in the first embodiment. It is a rectangle with a curve at the corner (that is, the corner has an R) instead of a square. Here, as Figure 3 shown, the long side direction B of the outer shape of the light-emitting element structure 18 after element separation when viewed from above is set to be inconsistent with the direction A of the crystal orientation <110>. In particular, in the direction of the crystal orientation <110> (direction A), it is preferable that the line connecting the corner point and its diagonal is substantially consistent with the <110> direction. The processes after the element separation process (including the process of forming the SiO2 pattern) ( Figures 9 to 11 ) are the same as those in the first embodiment.

[0104] (Fourth Embodiment)

[0105] Next, the fourth embodiment will be described. In this fourth embodiment, when the outer shape of the light-emitting element structure 18 after element separation is viewed from above, it is a polygon.

[0106] In the fourth embodiment, as Figure 4 shown, the outer shape of the light-emitting element structure 18 after element separation when viewed from above is a polygon ( Figure 4 a hexagon that is not a regular hexagon in Figure 4 ). Here, as

[0107] shown, the long side direction B of the outer shape of the light-emitting element structure 18 after element separation when viewed from above is set to be inconsistent with the direction A of the crystal orientation <110>.

[0107] The method of manufacturing this Micro LED structure is as follows. First, the process and structure of manufacturing the bonding substrate ( Figures 5 to 7 ) are the same as those in the first embodiment.

[0108] The process of element separation (including the process of forming the SiO2 pattern) (refer to Figure 8 ) is also the same as that in the first embodiment, but the shape of the SiO2 pattern is different from that in the first embodiment and is a polygon instead of a square. Here, as Figure 4 shown, the long side direction B of the outer shape of the light-emitting element structure 18 after element separation when viewed from above is set to be inconsistent with the direction A of the crystal orientation <110>. The processes ( Figures 9 to 11 ) after the process of element separation (including the process of forming the SiO2 pattern) are the same as those in the first embodiment.

[0109] Examples

[0110] Hereinafter, examples and comparative examples will be given to illustrate the present invention in detail, but they are not intended to limit the present invention.

[0111] (Examples and Comparative Examples)

[0112] According to the second embodiment, a Micro LED structure 58 having a light-emitting element structure 18 is manufactured. That is, as Figure 2 shown, the outer shape when the light-emitting element structure after element separation is viewed from above is a rectangle.

[0113] First, as Figure 5 shown, an epitaxial wafer having a light-emitting element structure as an epitaxial functional layer is prepared. Specifically, it is as follows. First, on an N-type GaAs starting substrate 11, after laminating an N-type GaAs buffer layer, an N-type Ga x In 1-x P (0.4 ≤ x ≤ 0.6) first etch stop layer and an N-type GaAs second etch stop layer with a thickness of 0.1 μm are formed to form an etch stop layer 12. On the etch stop layer 12, an N-type (Al y Ga 1-y ) x In 1-xP(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, 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, P-type Ga x In 1-x P(0.5 ≤ x ≤ 1.0) intermediate layer (not shown), P-type GaP window layer 16 with a thickness of 6 μm, prepare an epitaxial wafer 20 having a light-emitting element structure 18 as an epitaxial functional layer ( Figure 5 )

[0114] Subsequently, as Figure 6 shown, spin-coat a thermosetting bonding member, i.e., benzocyclobutene (BCB), as the adhesive or bonding material 25 on the epitaxial wafer 20, stack it opposite to a sapphire substrate as the transparent substrate 30, and perform thermocompression bonding in a vacuum atmosphere. When coating BCB by spin-coating, the designed film thickness is set to 0.6 μm.

[0115] Subsequently, as Figure 7 shown, remove the GaAs starting substrate 11 by wet etching to expose the N-type first etch stop layer, and remove the first cladding layer 13 by using etchants suitable for the first etch stop layer and the second etch stop layer, respectively. Thus, an epitaxial bonding substrate having only the DH layer and the window layer 16 can be fabricated.

[0116] Subsequently, use P-CVD, photolithography, and wet etching methods to form a rectangular SiO2 pattern with a length of 50 μm and a width of 25 μm, and perform device isolation to form an island pattern. After forming the island pattern, etch a part of the DH layer portion by ICP method to expose the second cladding layer 15 ( Figure 8 ). After that, form a SiO2 protective film 52 on the processed cross-section ( Figure 9 ). After that, as Figure 2 、 Figure 10As shown in the figure, the first electrode 54 and the second electrode 56 with different polarities are arranged near the end portion in the major axis direction when viewed from above. The Micro LED structure 58 is fabricated in this way. However, as the Micro LED structure 58, a plurality of epitaxial bonding substrates are fabricated, and the angles between the long side direction B and the direction A of the crystal orientation <110> are set to 0° (comparative example), 5°, 10°, 15°, 20°, 25°, 30°, 35°, 40°, and 45° (the above are examples) respectively. In the comparative example, the long side direction of the pattern is formed to be substantially consistent with the <110> direction.

[0117] For the Micro LED structures 58 fabricated in each of the examples and the comparative example, as Figure 11 shown, they are transferred to the transfer substrate 70.

[0118] Figure 12 The results of the examples and the comparative example are shown. When the long side direction of the outer shape of the light-emitting element structure is substantially consistent with the <110> direction of the crystal orientation when viewed from above, that is, in the case of the comparative example, about 30% of the chips are broken. However, by tilting the long side direction from the <110> crystal orientation, the breakage rate is reduced, and when the angle is set to 10° or more, the breakage rate is zero. Since the upper limit of the angle tilted from the <110> crystal orientation is 45°, 45° is the upper limit of the tilt.

[0119] This specification includes the following aspects.

[0120] [1] A Micro LED structure having a light-emitting element structure with (Al y Ga 1-y ) x In 1-x P (0.4 ≤ x ≤ 0.6, 0 ≤ y ≤ 0.5) as the active layer, the light-emitting element structure being bonded to a transparent substrate that is transparent to the emission wavelength and absorbs the laser for LLO transfer by an adhesive or bonding material that is transparent to the emission wavelength and the laser for LLO transfer. The Micro LED structure is characterized in that

[0121] the light-emitting element structure is element-separated,

[0122] the element-separated light-emitting element structure has at least two electrodes with different polarities on one surface,

[0123] when viewed from above, the long side direction of the outer shape of the element-separated light-emitting element structure is not consistent with the <110> crystal orientation.

[0124] [2] The Micro LED structure as described in [1] above, wherein, when observing the shape of the light-emitting element structure from above, the long side direction of the shape is offset from the crystal orientation <110> within a range of 10° or more and 45° or less.

[0125] [3] The Micro LED structure as described in [2] above, wherein, when observing the shape of the light-emitting element structure from above, the long side direction of the shape is offset from the crystal orientation <110> within a range of 22.5° or more and 30° or less.

[0126] [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.

[0127] [5] The Micro LED structure according to any one of [1] to [4] above, wherein the adhesive or bonding material is benzocyclobutene.

[0128] [6] The Micro LED structure according to any one of [1] to [5] above, wherein the transparent substrate is sapphire or quartz.

[0129] [7] A method for manufacturing a Micro LED structure, which is a method for manufacturing a Micro LED structure by using the following steps:

[0130] Forming a light-emitting element structure having (Al y Ga 1-y ) x In 1-x P (0.4 ≤ x ≤ 0.6, 0 ≤ y ≤ 0.5) as an active layer on a starting substrate;

[0131] Bonding the light-emitting element structure to a transparent substrate that is transparent to the emission wavelength and absorbs the laser for LLO transfer with an adhesive or bonding material;

[0132] Separating the light-emitting element structure into elements; and,

[0133] Forming at least two electrodes with different polarities on one surface of the light-emitting element structure separated into elements,

[0134] The feature of this manufacturing method is that

[0135] In the step of separating the elements, the long side direction of the shape when observing the light-emitting element structure separated into elements from above is set to be inconsistent with the crystal orientation <110>.

[0136] [8] The manufacturing method of the Micro LED structure as described in [7] above, wherein the long side direction of the outer shape when observing the light-emitting element structure from above is offset from the crystal orientation <110> in a range of 10° or more and 45° or less.

[0137] [9] The manufacturing method of the Micro LED structure as described in [8] above, wherein the long side direction of the outer shape when observing the light-emitting element structure from above is offset from the crystal orientation <110> in a range of 22.5° or more and 30° or less.

[0138]

[10] The manufacturing method of the Micro LED structure as described in any one of [7] to [9] above, which further has a step of removing the starting substrate.

[0139]

[11] The manufacturing method of the Micro LED structure as described in any one of [7] to

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

[0140]

[12] The manufacturing method of the Micro LED structure as described in any one of [7] to

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

[0141] In addition, the present invention is not limited to the above embodiments. The above embodiments are illustrative, and technical solutions having the same constituent elements as the technical idea described in the claims of the present invention and exhibiting the same effects are all included in the technical scope of the present invention.

Claims

1. A Micro LED structure having a light-emitting element structure with (Al y Ga 1-y ) x In 1-x P as an active layer, wherein, 0.4 ≤ x ≤ 0.6, 0 ≤ y ≤ 0.

5. The light-emitting element structure is bonded to a transparent substrate that is transparent to the light-emitting wavelength and absorbs the laser for LLO transfer using an adhesive or bonding material. The Micro LED structure is characterized in that the light-emitting element structure is element-separated. The element-separated light-emitting element structure has at least two electrodes with different polarities on one surface. When viewed from above, the long side direction of the outer shape of the element-separated light-emitting element structure does not coincide with the crystal orientation <110>.

2. The Micro LED structure according to claim 1, wherein When viewed from above, the long side direction of the outer shape of the light-emitting element structure is offset from the crystal orientation <110> in a range of 10° or more and 45° or less.

3. The Micro LED structure according to claim 2, wherein When viewed from above, the long side direction of the outer shape of the light-emitting element structure is offset from the crystal orientation <110> in a range of 22.5° or more and 30° or less.

4. The Micro LED structure according to claim 1 or 2, characterized in that, The light-emitting element structure does not have a starting substrate.

5. The Micro LED structure according to claim 1 or 2, wherein, The adhesive or bonding material is benzocyclobutene.

6. The Micro LED structure according to claim 1 or 2, wherein The transparent substrate is sapphire or quartz.

7. A method for manufacturing a Micro LED structure, which is a method for manufacturing a Micro LED structure using the following steps: Forming a light-emitting element structure having (Al y Ga 1-y ) x In 1-x P as an active layer, wherein, 0.4 ≤ x ≤ 0.6, 0 ≤ y ≤ 0.5; A step of bonding the light-emitting element structure to a transparent substrate that is transparent to the light-emitting wavelength of the light-emitting element structure and the laser for LLO transfer using an adhesive or bonding material; A step of element-separating the light-emitting element structure; and A step of forming at least two electrodes with different polarities on one surface of the element-separated light-emitting element structure, The method for manufacturing the Micro LED structure is characterized in that in the step of element-separating, the long side direction of the outer shape of the element-separated light-emitting element structure is set to be inconsistent with the crystal orientation <110>.

8. The manufacturing method of the Micro LED structure according to claim 7, characterized in that, The long side direction of the outer shape of the light-emitting element structure when viewed from above is offset from the crystal orientation <110> in a range of 10° or more and 45° or less.

9. The manufacturing method of the Micro LED structure according to claim 8, characterized in that, The long side direction of the outer shape of the light-emitting element structure when viewed from above is offset from the crystal orientation <110> in a range of 22.5° or more and 30° or less.

10. The manufacturing method of the Micro LED structure according to claim 7 or 8, characterized in that, It further has a step of removing the starting substrate.

11. The manufacturing method of the Micro LED structure according to claim 7 or 8, characterized in that, The adhesive or bonding material is set to benzocyclobutene.

12. The manufacturing method of the Micro LED structure according to claim 7 or 8, characterized in that, The transparent substrate is set to sapphire or quartz.

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