Flip LED chip, display module and preparation method of flip LED chip
By introducing a high-refractive-index transparent dielectric layer and micro-patterned structure into the flip-chip LED, the problem of small light emission angle is solved, enabling light transmission at a wider angle and higher luminous efficiency, thus expanding the application fields.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2026-01-26
- Publication Date
- 2026-03-27
AI Technical Summary
The narrow beam angle of flip-chip LEDs limits their application range, especially the beam angle of quaternary red flip-chip LEDs, which is only 120°-130°.
Introducing a transparent dielectric layer into a flip-chip LED, with a refractive index higher than that of the substrate and bonding layer, combined with the micro-patterned structure on the substrate surface, increases the light transmission angle and extends the emission angle through scattering.
This increases the light-emitting angle of flip-chip LEDs, improves luminous efficiency, and expands their application range.
Smart Images
Figure CN121751840A_ABST
Abstract
Description
TECHNICAL FIELD
[0001] The present application relates to the technical field of light emitting diode, in particular to a flip LED chip, a display module and a preparation method of the flip LED chip. BACKGROUND
[0002] The flip light emitting diode (LED) chip solves the heat dissipation bottleneck, light shielding and gold wire reliability of the traditional LED chip by turning the electrode upside down and directly welding, and has been widely used in high-power lighting, automobile headlamps and display terminals.
[0003] However, there is an inherent problem in the flip LED chip on the market at present, that is, the flip LED chip has a small light emitting angle, for example, the light emitting angle of a quaternary red flip LED chip is only 120°-130°, which greatly limits the application of the flip LED chip. SUMMARY
[0004] To solve the above technical problems, the present application provides a flip LED chip, a display module and a preparation method of the flip LED chip, so as to increase the light emitting angle of the flip LED chip, improve the light emitting efficiency of the flip LED chip and expand the application of the flip LED chip.
[0005] To achieve the above purpose, the present application provides the following technical solutions:
[0006] In a first aspect, the present application provides a flip LED chip, comprising:
[0007] A first substrate, the first substrate has a first surface and a second surface arranged oppositely, the first surface has a plurality of first micro-pattern structures, and the second surface is a light emitting surface of the flip LED chip;
[0008] A transparent dielectric layer located on one side of the first surface of the first substrate, the thickness of the transparent dielectric layer is not less than the height of the first micro-pattern structure, and the refractive index of the transparent dielectric layer is greater than the refractive index of the first substrate;
[0009] A bonding layer located on the side of the transparent dielectric layer away from the first substrate, and the refractive index of the transparent dielectric layer is greater than the refractive index of the bonding layer;
[0010] A first epitaxial layer located on the side of the bonding layer away from the first substrate.
[0011] Optionally, the first substrate comprises a sapphire substrate.
[0012] Optionally, the first micro-pattern structure comprises a micro-protrusion structure or a micro-groove structure.
[0013] Optionally, the transparent dielectric layer comprises a stack of one or more of a gallium nitride layer, a zinc germanium layer, a zinc sulfide layer, and a titanium dioxide layer.
[0014] Optionally, the bonding layer comprises a stack of one or at least two of a silicon oxide layer, a silicon nitride layer, an aluminum oxide layer, and a silicon oxynitride layer.
[0015] Optionally, the first epitaxial stack comprises, in a direction away from the first substrate, a first-type semiconductor layer, an active layer, and a second-type semiconductor layer, and the first epitaxial stack has a first recess on a side away from the first substrate, the first recess exposing part of the first-type semiconductor layer;
[0016] A first electrode is disposed on a surface of the first-type semiconductor layer exposed by the first recess;
[0017] A second electrode is disposed on a side of the second-type semiconductor layer away from the first substrate.
[0018] Optionally, the flip-chip LED further comprises:
[0019] A first insulating reflective layer covering the first epitaxial stack on a side of the first epitaxial stack away from the first substrate, the first insulating reflective layer having a first through-hole and a second through-hole, the first through-hole exposing at least part of the first electrode, and the second through-hole exposing at least part of the second electrode;
[0020] A first pad and a second pad on a side of the first insulating reflective layer away from the first substrate, the first pad being electrically connected to the first electrode through the first through-hole, and the second pad being electrically connected to the second electrode through the second through-hole.
[0021] Optionally, the flip-chip LED is a red flip-chip LED.
[0022] Optionally, the first epitaxial stack comprises a III-V compound semiconductor material, and the active layer comprises a quaternary semiconductor material.
[0023] In a second aspect, the present application provides a display module, comprising:
[0024] A substrate;
[0025] A plurality of first flip-chip LEDs and a plurality of second flip-chip LEDs on a side of the substrate, wherein the first flip-chip LED is any of the flip-chip LEDs described above.
[0026] Optionally, the second flip-chip LED comprises:
[0027] a second substrate having oppositely arranged third and fourth surfaces, the third surface having a plurality of second micro-pattern structures, and the fourth surface being a light-out surface of the second flip LED chip;
[0028] a buffer layer located on the third surface side of the second substrate, the buffer layer having a thickness not less than a height of the second micro-pattern structures;
[0029] a second epitaxial layer located on the buffer layer side away from the second substrate.
[0030] In a third aspect, the application provides a method for preparing a flip LED chip, comprising:
[0031] providing a first substrate having oppositely arranged first and second surfaces, and forming a plurality of first micro-pattern structures on the first surface of the first substrate;
[0032] forming a transparent dielectric layer on the first surface side of the first substrate, the transparent dielectric layer having a thickness not less than a height of the first micro-pattern structures, and the transparent dielectric layer having a refractive index greater than a refractive index of the first substrate;
[0033] forming a first sub-bonding layer on the transparent dielectric layer side away from the first substrate;
[0034] providing a stack structure comprising a growth substrate and a first epitaxial layer located on the growth substrate side, and forming a second sub-bonding layer on the first epitaxial layer side away from the growth substrate;
[0035] bonding the first sub-bonding layer and the second sub-bonding layer together to form a bonding layer, so that the first epitaxial layer is bonded to the transparent dielectric layer side away from the first substrate through the bonding layer, and the transparent dielectric layer has a refractive index greater than a refractive index of the bonding layer;
[0036] removing the growth substrate.
[0037] Compared with the prior art, the above technical solution has the following advantages:
[0038] The flip LED chip provided in the application comprises a first substrate having oppositely arranged first and second surfaces, the first surface has a plurality of first micro-pattern structures, and the second surface is a light exit surface of the flip LED chip; the first surface of the first substrate is provided with a transparent medium layer, the thickness of the transparent medium layer is not less than the height of the first micro-pattern structure, that is, the transparent medium layer can fill the plurality of first micro-pattern structures on the first surface of the first substrate, or the transparent medium layer covers the plurality of first micro-pattern structures on the first surface of the first substrate; the side of the transparent medium layer away from the first substrate is provided with a bonding layer, and the side of the bonding layer away from the first substrate is provided with a first epitaxial layer, that is, the first epitaxial layer is bonded to the side of the transparent medium layer away from the first substrate through the bonding layer; thus, the light emitted by the epitaxial layer will pass through the bonding layer, the transparent medium layer, the first micro-pattern structure on the first surface of the first substrate and the first substrate in sequence and be emitted from the second surface of the first substrate; since the refractive index of the transparent medium layer is greater than the refractive index of the first substrate and greater than the refractive index of the bonding layer, that is, the transparent medium layer with a higher refractive index is added between the first substrate and the bonding layer, therefore, the transparent medium layer allows the transmission of light with a larger angle than the bonding layer, and allows more light with a larger incident angle to be incident to the first substrate, and then the scattering effect of the plurality of first micro-pattern structures on the first surface of the first substrate, so that the exit angle of the light emitted by the flip LED chip is widened, that is, the light-emitting angle of the flip LED chip is increased, and the light-emitting efficiency of the flip LED chip is improved, thereby expanding the application of the flip LED chip. BRIEF DESCRIPTION OF DRAWINGS
[0039] In order to more clearly illustrate the technical solutions in the embodiments of the application or the prior art, the following will briefly introduce the drawings needed to be used in the embodiments or the prior art description. Obviously, the drawings in the following description are only some embodiments of the application, and for those skilled in the art, other drawings can also be obtained without creative labor on the basis of these drawings.
[0040] Figure 1 A cross-sectional structure schematic diagram of a flip LED chip provided in an embodiment of the application;
[0041] Figure 2 A cross-sectional structure schematic diagram of another flip LED chip provided in an embodiment of the application;
[0042] Figure 3 A cross-sectional structure schematic diagram of a flip LED chip provided in an embodiment of the application;
[0043] Figure 4 A Figure 3 A schematic diagram of light emitted by the first epitaxial layer in the flip LED chip shown in the figure transmitting to the second surface of the first substrate;
[0044] Figure 5 for Figure 1 and Figure 2 a schematic diagram of light emitted by the first epitaxial stack in the flip LED chip shown in FIG. 1A being transmitted to the second surface of the first substrate;
[0045] Figures 6a-6j for a flip LED chip provided by an embodiment of the present application, a structure schematic diagram corresponding to each process step in a preparation method of the flip LED chip;
[0046] Figure 7 for a display module provided by an embodiment of the present application, a cross-sectional structure schematic diagram of the second flip LED chip.
[0047] Marked for explanation:
[0048] a first substrate 10; a first surface S1; a second surface S2; a first micro-pattern structure T1; a transparent dielectric layer 20; a bonding layer 30; a first sub-bonding layer 31; a second sub-bonding layer 32; a first epitaxial stack 40; a first type semiconductor layer 41; an active layer 42; a second type semiconductor layer 43; a first electrode D1; a second electrode D2; a first insulating reflective layer 50; a first pad P1; a second pad P2; a first recess U1; an isolation channel W1; a first via K1; a second via K2; a growth substrate 101; a second substrate 200; a third surface S3; a fourth surface S4; a second micro-pattern structure T2; a buffer layer 210; a second epitaxial stack 220; an N-type semiconductor layer 221; an active layer 222; a P-type semiconductor layer 223; a transparent conductive layer 230; an N-type electrode 241; a P-type electrode 242; a second insulating reflective layer 250; a second recess U2; a third via K3; a fourth via K4; a third pad 261; a fourth pad 262; a stacked structure 100. DETAILED DESCRIPTION
[0049] The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative work fall within the scope of protection of the present application.
[0050] The terms "first", "second", and the like in the description and in the claims of the present application and above drawings are used to distinguish similar objects and are not necessarily used to describe a specific sequential or chronological order. It should be understood that the terms so used are interchangeable under appropriate circumstances and are merely employed in the description of embodiments of the present application for descriptive purposes. Furthermore, the terms "comprising", "having", "including", and the like, are inclusive and are used in the broadest context only to include the items listed and also any items associated with or inherent to such items without limitation.
[0051] Secondly, the present application is described in detail in conjunction with the schematic diagram, in the detailed description of the embodiments of the present application, for the convenience of description, the drawing of the device structure will be partially enlarged without the general proportion, and the schematic diagram is only an example, which should not limit the scope of protection of the present application herein. In addition, the three-dimensional spatial dimensions of length, width and depth should be included in actual production.
[0052] As described in the background section, there is an inherent problem in the flip LED chip on the market at present, that is, the light emitting angle of the flip LED chip is small, for example, the light emitting angle of the quaternary system red light flip LED chip is only 120°-130°, which greatly limits the application of the flip LED chip.
[0053] Therefore, the embodiments of the present application provide a flip LED chip, Figure 1 The cross-sectional structure schematic diagram of the flip LED chip provided by the embodiments of the present application is shown, as shown in the figure, Figure 1 The flip LED chip includes a first substrate 10, the first substrate 10 has oppositely arranged first and second surfaces S1 and S2, the first surface S1 of the first substrate 10 has a plurality of first micro-pattern structures T1, and the second surface S2 of the first substrate 10 is the light emitting surface of the flip LED chip; the first surface S1 of the first substrate 10 is provided with a transparent medium layer 20, the thickness of the transparent medium layer 20 is not less than the height of the first micro-pattern structure T1, the refractive index of the transparent medium layer 20 is greater than the refractive index of the first substrate 10; the side of the transparent medium layer 20 away from the first substrate 10 is provided with a bonding layer 30, and the refractive index of the transparent medium layer 20 is also greater than the refractive index of the bonding layer 30; the side of the bonding layer 30 away from the first substrate 10 is provided with a first epitaxial layer 40.
[0054] Optionally, the first substrate 10 includes a sapphire substrate, but the present application is not limited thereto.
[0055] Optionally, the first micro-pattern structure T1 of the first surface S1 of the first substrate 10 can include a micro-protruding structure or a micro-groove structure, which is determined according to the specific circumstances.
[0056] Optionally, the first micro-pattern structure T1 of the first surface S1 of the first substrate 10 can comprise regular or irregular pattern structure; for example, can comprise multi-prism, in particular, like a cone, pyramid, platform cone, etc.; for example, can comprise a hemisphere or a semi-elliptical.
[0057] Optionally, the height of the first micro-pattern structure T1 can range from -5 μm to 5 μm, including the end point value, wherein the height of the first micro-pattern structure T1 is negative, the first micro-pattern structure T1 is a micro-groove structure; the height of the first micro-pattern structure T1 is positive, the first micro-pattern structure T1 is a micro-protrusion structure.
[0058] It can be understood that the thickness of the transparent dielectric layer 20 located on the side of the first surface S1 of the first substrate 10 is not less than the height of the first micro-pattern structure T1, so that the transparent dielectric layer 20 can fill the plurality of first micro-pattern structures T1 of the first surface S1 of the first substrate 10, such as Figure 1 As shown in the figure; or, as Figure 2 As shown, Figure 2 Another cross-sectional structure of the flip LED chip provided by the embodiment of the present application is shown, and the transparent dielectric layer 20 can also cover the plurality of first micro-pattern structures T1 of the first surface S1 of the first substrate 10.
[0059] Optionally, the transparent dielectric layer 20 can comprise a stack of one or more of a gallium nitride (GaN) layer, a zinc germanium (ZnGe) layer, a zinc sulfide (ZnS) layer, and a titanium dioxide (TiO2) layer.
[0060] Optionally, the bonding layer 30 comprises a stack of one or at least two of a silicon oxide layer, a silicon nitride layer, an aluminum oxide layer, and a silicon oxynitride layer.
[0061] It can be understood that the first epitaxial layer 40 is bonded to the side of the transparent dielectric layer 20 away from the first substrate 10 through the bonding layer 30, that is, the first epitaxial layer 40 is originally formed epitaxially on another growth substrate; then, a first sub-bonding layer is formed on the side of the transparent dielectric layer 20 away from the first substrate 10, and a second sub-bonding layer is formed on the side of the first epitaxial layer 40 away from the growth substrate; then, the first sub-bonding layer and the second sub-bonding layer are bonded together to form the bonding layer 30, so that the first epitaxial layer 40 is bonded to the side of the transparent dielectric layer 20 away from the first substrate 10 through the bonding layer 30, and then the growth substrate of the first epitaxial layer 40 is removed.
[0062] As a comparison, Figure 3 A cross-sectional structure of a flip LED chip is shown, as Figure 3As shown, the flip LED chip includes a first substrate 10, a bonding layer 30 located on the first surface S1 side of the first substrate 10, and a first epitaxial stack 40 located on the side of the bonding layer 30 away from the first substrate 10, that is, the first epitaxial stack 40 is directly bonded on the first surface S1 side of the first substrate 10 through the bonding layer 30, and the first surface S1 of the first substrate 10 is a plane.
[0063] As shown in Figures 1-3 The first epitaxial stack 40 includes a first type semiconductor layer 41, an active layer 42, and a second type semiconductor layer 43 stacked in the direction away from the first substrate 10. Optionally, the first epitaxial stack 40 includes a III-V compound semiconductor material, and the active layer 42 includes a quaternary semiconductor material. For example, taking the flip LED chip as a quaternary red flip LED chip as an example, in the first epitaxial stack 40, the first type semiconductor layer 41 is a P-type semiconductor layer, and the material of the first type semiconductor layer 41 includes but is not limited to one or more of GaP, AlGaInP, AlInP with P-type doping, accordingly, the second type semiconductor layer 43 is an N-type semiconductor layer, and the material of the second type semiconductor layer 43 includes but is not limited to one or more of GaP, AlGaInP, AlInP with N-type doping, and the active layer 42 is an AlGaInP multi-quantum well structure. The light emitted by the first epitaxial stack 40 (mainly the active layer 42) is finally emitted from the second surface S2 of the first substrate 10.
[0064] Figure 4 As shown in Figure 3 The flip LED chip shown in the schematic diagram of the light emitted by the first epitaxial stack 40 transmitting to the second surface S2 of the first substrate 10, in combination with Figure 3 and Figure 4 As shown in Figure 3 Taking the flip LED chip shown in as a quaternary red flip LED chip as an example, in the first epitaxial stack 40, the active layer 42 is an AlGaInP multi-quantum well structure, the material of the first type semiconductor layer 41 includes but is not limited to one or more of GaP, AlGaInP, AlInP with P-type doping, accordingly, the material of the second type semiconductor layer 43 includes but is not limited to one or more of GaP, AlGaInP, AlInP with N-type doping, and taking the bonding layer 30 as a silicon oxide layer and the first substrate 10 as a sapphire substrate as an example, thus, the light emitted by the first epitaxial stack 40 is emitted after sequentially passing through the bonding layer 30 and the first substrate 10.
[0065] The light emitted by the first epitaxial stack 40 first passes through the interface between the first epitaxial stack 40 and the bonding layer 30. Since the portion of the first epitaxial stack 40 close to the bonding layer 30 is a P-type semiconductor layer, its refractive index is approximately 3.4, and the bonding layer 30 is a silicon oxide layer, its refractive index is approximately 1.46, that is, the light emitted by the first epitaxial stack 40 enters a low refractive index layer (optically thin medium) from a high refractive index layer (optically thick medium), so total reflection may occur. The critical incident angle (relative to the normal direction of the interface between the first epitaxial stack 40 and the bonding layer 30) of total reflection is approximately 25.4°, that is, only the light with an incident angle (relative to the normal direction of the interface between the first epitaxial stack 40 and the bonding layer 30) less than 25.4° can enter the bonding layer 30. The refractive angle of the light with an incident angle (relative to the normal direction of the interface between the first epitaxial stack 40 and the bonding layer 30) equal to 25.4° is 90°, and the light with an incident angle (relative to the normal direction of the interface between the first epitaxial stack 40 and the bonding layer 30) greater than 25.4° is totally reflected, which limits the incident angle range (relative to the normal direction of the interface between the first epitaxial stack 40 and the bonding layer 30) of the light entering the bonding layer 30 to within ±25.4°.
[0066] Then, the light passes through the interface between the bonding layer 30 and the first substrate 10. Since the bonding layer 30 is a silicon oxide layer with a refractive index of approximately 1.46, and the first substrate 10 is a sapphire substrate with a refractive index of approximately 1.77, that is, the light enters a high refractive index layer (optically thick medium) from a low refractive index layer (optically thin medium), so total reflection does not occur, but the refracted light is deflected towards the normal direction of the interface between the bonding layer 30 and the first substrate 10. Assuming that the light enters the first substrate 10 from the bonding layer 30 at a maximum incident angle close to 90°, and refraction occurs at the interface between the bonding layer 30 and the first substrate 10, the maximum refractive angle of the refracted light incident on the first substrate 10 is 55.57°, that is, the maximum angle of the light transmitted in the first substrate 10 is 55.57°, but the majority is small-angle light.
[0067] Finally, the light passes through the interface between the first substrate 10 and the surrounding air, that is, the second surface S2 of the first substrate 10. Since the first substrate 10 is a sapphire substrate with a refractive index of approximately 1.77, and the refractive index of the surrounding air is 1, that is, the light enters a low refractive index layer (optically thin medium) from a high refractive index layer (optically thick medium), so total reflection may occur. In theory, the critical incident angle (relative to the normal direction of the second surface S2 of the first substrate 10) of total reflection is approximately 34.4°, that is, when the light reaches the second surface S2 of the first substrate 10, the light with an incident angle not exceeding the critical angle of total reflection of 34.4° can be emitted.
[0068] Therefore, in the existing flip LED chip, when the light emitted from the first epitaxial stack 40 is incident to the interface between the bonding layer 30 and the first substrate 10, due to the difference in refractive index between the bonding layer 30 and the first substrate 10, the angle of the light incident into the first substrate 10 will not exceed 55.57°, and the main proportion is small-angle light, so that the light-emitting angle of the existing flip LED chip is small, only 120°-130°.
[0069] In addition, although theoretically there are some scattered or specific mode light rays that can be incident to the first substrate 10 at an incident angle greater than 55.57°, for example, light rays that are transmitted in the first substrate 10 in a direction close to parallel to the first surface S1 of the first substrate 10, but the incident angle of these light rays at the interface between the first substrate 10 and the external air is much larger than the total reflection critical angle 34.4°, and they will be trapped in the first substrate 10 with a planar interface. The first substrate 10 with a planar interface lacks an effective mechanism to change the direction of these light rays to be less than the total reflection critical angle 34.4° to be emitted, and finally the angle distribution of the emitted light rays is concentrated, and the light-emitting angle is narrow.
[0070] Figure 5 The flip LED chip shown in Figure 1 and Figure 2 shows a schematic diagram of the light emitted from the first epitaxial stack 40 being transmitted to the second surface S2 of the first substrate 10, in combination with Figure 1 , Figure 2 and Figure 5 shown, also taking the flip LED chip shown in Figure 1 and Figure 2 as an example of a quaternary red light flip LED chip, then in the first epitaxial stack 40, the active layer 42 is an AlGaInP multi-quantum well structure, and the material of the first type semiconductor layer 41 includes but is not limited to one or more of GaP, AlGaInP, AlInP with P-type doping, accordingly, the material of the second type semiconductor layer 43 includes but is not limited to one or more of GaP, AlGaInP, AlInP with N-type doping, and taking the bonding layer 30 as a silicon oxide layer, the transparent dielectric layer 20 as a gallium nitride layer, and the first substrate 10 as a sapphire substrate as an example, the light emitted from the first epitaxial stack 40 is emitted after passing through the bonding layer 30, the transparent dielectric layer 20 and the first substrate 10 in turn.
[0071] Among them, the light emitted from the first epitaxial stack 40 first passes through the interface between the first epitaxial stack 40 and the bonding layer 30. Similar to the flip LED chip shown in Figure 3 , Figure 1 and Figure 2In the flip-chip LED shown, the light emitted by the first epitaxial stack 40 can be totally reflected when it passes through the interface between the first epitaxial stack 40 and the bonding layer 30. The critical incident angle of the total reflection (relative to the normal direction of the interface between the first epitaxial stack 40 and the bonding layer 30) is approximately 25.4°, so that the incident angle range of the light entering the bonding layer 30 (relative to the normal direction of the interface between the first epitaxial stack 40 and the bonding layer 30) is limited within ±25.4°.
[0072] In the flip-chip LED shown, Figure 3 In the flip-chip LED shown, Figure 1 In the flip-chip LED shown, Figure 2 In the flip-chip LED shown, a transparent medium layer 20 with a higher refractive index is arranged between the bonding layer 30 and the first substrate 10, and then the light passes through the interface between the bonding layer 30 and the transparent medium layer 20. Since the bonding layer 30 is a silicon oxide layer with a refractive index of approximately 1.46, and the transparent medium layer 20 is a gallium nitride layer with a refractive index of approximately 2.4, i.e., the light enters a high refractive index layer (optically dense medium) from a low refractive index layer (optically sparse medium), so no total reflection occurs, but the refracted light is deflected towards the normal direction of the interface between the bonding layer 30 and the transparent medium layer 20. Assuming that the light enters the transparent medium layer 20 from the bonding layer 30 at a maximum incident angle close to 90°, and is refracted at the interface between the bonding layer 30 and the transparent medium layer 20, the maximum refractive angle of the refracted light entering the transparent medium layer 20 is 37.47°.
[0073] Next, the light passes through the interface between the transparent medium layer 20 and the first substrate 10. Since the transparent medium layer 20 is a gallium nitride layer with a refractive index of approximately 2.4, and the first substrate 10 is a sapphire substrate with a refractive index of approximately 1.77, i.e., the light enters a low refractive index layer (optically sparse medium) from a high refractive index layer (optically dense medium), so total reflection can occur. In theory, the critical incident angle of the total reflection (relative to the normal direction of the interface between the transparent medium layer 20 and the first substrate 10) is approximately 47.5°. Moreover, according to the law of refraction, the refracted light is deflected away from the normal direction of the interface between the transparent medium layer 20 and the first substrate 10 when the light enters the first substrate 10 from the transparent medium layer 20. Assuming that the light enters the first substrate 10 at a maximum incident angle (close to 37.47°), according to the law of refraction, the maximum refractive angle of the refracted light entering the first substrate 10 is also 55.57°.
[0074] Although according to the law of refraction, the present application Figure 1 In the flip-chip LED shown, Figure 2 In the flip-chip LED shown, Figure 3The maximum incident angle range of the light rays shown in the existing flip LED chip finally incident to the first surface S1 of the first substrate 10 is approximately ±55.57°, but in theory, there are some scattered or specific mode light rays, for example, the light rays emitted by the active layer 42 that experience less refractive loss or scattering in the first epitaxial layer 40 and the bonding layer 30, which can be incident to the transparent medium layer 20 at a relatively large angle. Since the refractive index of the transparent medium layer 20 is greater than the refractive index of the first substrate 10 and greater than the refractive index of the bonding layer 30, the transmission of these large-angle light rays in the transparent medium layer 20 is allowed, in particular, the high-refractive transparent medium layer 20 allows the light rays to exist at a larger angle inside it without immediately reaching the total reflection critical angle; and the crystal defects, uneven doping, etc. inside the transparent medium layer 20 can scatter the light rays transmitted inside it, so that the light rays transmitted in the transparent medium layer 20 change direction and increase the diversity of light ray angles. Finally, the light rays incident to the first substrate 10 through the transparent medium layer 20 will actually have some light rays with an incident angle greater than 55.57°, and the proportion of large-angle light rays will increase.
[0075] Moreover, the first surface S1 of the first substrate 10 (i.e. the interface between the first substrate 10 and the transparent medium layer 20) is also provided with a plurality of first micro-pattern structures T1. When the light rays are transmitted to the first surface S1 of the first substrate 10, they will hit the inclined surfaces, edges and curved surfaces of these first micro-pattern structures T1. This impact will cause the light rays to be diffusely reflected and refracted, so that the transmission direction of the light rays is randomized and diversified.
[0076] Thus, the incident angle of the light rays entering the first substrate 10 will increase and be diversified, and the amount of light rays entering the first substrate 10 will also increase.
[0077] Finally, when the light rays pass through the interface between the first substrate 10 and the outside air (i.e. the second surface S2 of the first substrate 10), although the first substrate 10 is a sapphire substrate with a refractive index of approximately 1.77, and the refractive index of the outside air is 1, i.e. the light rays enter from a high-refractive layer (optically dense medium) to a low-refractive layer (optically sparse medium), thus total reflection can occur. In theory, the critical incident angle of total reflection (relative to the normal direction of the second surface S2 of the first substrate 10) is approximately 34.4°, but since the incident angle of the light rays actually transmitted in the first substrate 10 is increased and diversified, the incident angle of the light rays incident to the second surface S2 of the first substrate 10 can be larger, so that the exit angle of the light rays finally emitted by the flip LED chip is widened and no longer concentrated in a small angle region, i.e. the flip LED chip's light-emitting angle is increased; and the amount of light rays entering the first substrate 10 also increases, thereby improving the flip LED chip's light-emitting efficiency.
[0078] Therefore, in the flip LED chip provided by the embodiment of the present application, the light emitted by the first epitaxial stack 40 will pass through the bonding layer 30, the transparent medium layer 20, the first micro-pattern structure T1 of the first surface S1 of the first substrate 10 and the first substrate 10 in sequence and be emitted from the second surface S2 of the first substrate 10. Since the refractive index of the transparent medium layer 20 is greater than the refractive index of the first substrate 10 and greater than the refractive index of the bonding layer 30, that is, the transparent medium layer 20 with a higher refractive index is added between the first substrate 10 and the bonding layer 30, the transparent medium layer 20 allows the transmission of light with a larger angle than the bonding layer 30 and allows more light with a larger incident angle to be incident on the first substrate 10. Then, the light is scattered by the plurality of first micro-pattern structures T1 of the first surface S1 of the first substrate 10, so that the emission angle of the light emitted by the flip LED chip is widened, that is, the light-emitting angle of the flip LED chip is increased, and the light-emitting efficiency of the flip LED chip is improved, thereby expanding the application of the flip LED chip.
[0079] Optionally, in some embodiments of the present application, as shown in Figure 1 and Figure 2 , the first epitaxial stack 40 has a first groove U1 on the side away from the first substrate 10, and the first groove U1 exposes part of the first-type semiconductor layer 41. Specifically, the first groove U1 can only penetrate the second-type semiconductor layer 43 and the active layer 42 to expose part of the first-type semiconductor layer 41, or the first groove U1 can penetrate the second-type semiconductor layer 43, the active layer 42 and part of the first-type semiconductor layer 41 to expose part of the first-type semiconductor layer 41. A first electrode D1 is arranged on the surface of the first-type semiconductor layer 41 exposed by the first groove U1, and the first electrode D1 is electrically connected with the first-type semiconductor layer 41. A second electrode D2 is arranged on the side of the second-type semiconductor layer 43 away from the first substrate 10, and the second electrode D2 is electrically connected with the second-type semiconductor layer 43.
[0080] Further optionally, in some embodiments of the present application, as shown in Figure 1 and Figure 2 , the flip LED chip can further include a first insulating reflective layer 50 covering the first epitaxial stack 40 from the side of the first epitaxial stack 40 away from the first substrate 10. The first insulating reflective layer 50 has a first through hole K1 and a second through hole K2. The first through hole K1 exposes at least part of the first electrode D1, and the second through hole K2 exposes at least part of the second electrode D2. The flip LED chip can further include a first pad P1 and a second pad P2 on the side of the first insulating reflective layer 50 away from the first substrate 10. The first pad P1 is electrically connected with the first electrode D1 through the first through hole K1, and the second pad P2 is electrically connected with the second electrode D2 through the second through hole K2.
[0081] It can be understood that the first insulating reflective layer 50 can reflect the light emitted by the first epitaxial layer 40 (mainly the active layer 42) in the direction away from the first substrate 10 to the side of the first substrate 10, so as to improve the light emitting efficiency of the flip LED chip.
[0082] Optionally, the flip LED chip shown in the application Figure 1 and Figure 2 The flip LED chip shown in the application is a red flip LED chip for emitting red light. At this time, in the first epitaxial layer 40, the first type semiconductor layer 41 can be a P-type semiconductor layer, the active layer 42 is an AlGaInP multi-quantum well structure, and the second type semiconductor layer 43 can be an N-type semiconductor layer.
[0083] Correspondingly, the application also provides a preparation method of a flip LED chip, which comprises:
[0084] S1: as Figure 6a shown, a first substrate 10 is provided, the first substrate 10 has oppositely arranged first and second surfaces S1 and S2, and a plurality of first micro-pattern structures T1 are formed on the first surface S1 of the first substrate 10.
[0085] Optionally, the first substrate 10 comprises a sapphire substrate, but the application is not limited thereto.
[0086] Optionally, the first micro-pattern structure T1 of the first surface S1 of the first substrate 10 can comprise a micro-protrusion structure or a micro-groove structure, which is determined according to the specific situation.
[0087] Optionally, the first micro-pattern structure T1 of the first surface S1 of the first substrate 10 can comprise a regular or irregular pattern structure; for example, it can comprise a multi-prism, such as a conical shape, a pyramid shape, a platform conical shape, etc.; for another example, it can comprise a hemispherical or semi-elliptical shape.
[0088] Optionally, the height of the first micro-pattern structure T1 can range from -5 μm to 5 μm, including the end point value. When the height of the first micro-pattern structure T1 is negative, the first micro-pattern structure T1 is a micro-groove structure; when the height of the first micro-pattern structure T1 is positive, the first micro-pattern structure T1 is a micro-protrusion structure.
[0089] Optionally, a dry etching process can be used to form a plurality of first micro-pattern structures T1 on the first surface S1 of the first substrate 10, but the application is not limited thereto.
[0090] S2: as Figure 6bAs shown, a transparent dielectric layer 20 is formed on one side of the first surface S1 of the first substrate 10. The thickness of the transparent dielectric layer 20 is not less than the height of the first micro-pattern structure T1, and the refractive index of the transparent dielectric layer 20 is greater than the refractive index of the first substrate 10.
[0091] It is understood that the thickness of the transparent dielectric layer 20 located on one side of the first surface S1 of the first substrate 10 is not less than the height of the first micro-pattern structure T1. Therefore, the transparent dielectric layer 20 can fill the multiple first micro-pattern structures T1 on the first surface S1 of the first substrate 10, such as... Figure 1 As shown; or, as Figure 2 and Figure 6b As shown, the transparent dielectric layer 20 can also cover multiple first micro-patterned structures T1 on the first surface S1 of the first substrate 10.
[0092] Optionally, the transparent dielectric layer 20 may include one or more stacks of gallium nitride (GaN) layer, zinc germanium (ZnGe) layer, zinc sulfide (ZnS) layer and titanium dioxide (TiO2) layer.
[0093] S3: As Figure 6c As shown, a first subbonding layer 31 is formed on the side of the transparent dielectric layer 20 opposite to the first substrate 10.
[0094] S4: As Figure 6d As shown, a stacked structure 100 is provided, which includes a growth substrate 101 and a first epitaxial layer 40 located on one side of the growth substrate 101, as... Figure 6e As shown, a second sub-bonding layer 32 is formed on the side of the first epitaxial stack 40 away from the growth substrate 101.
[0095] The first epitaxial layer 40 includes a second type semiconductor layer 43, an active layer 42, and a first type semiconductor layer 41 stacked along a direction away from the growth substrate 101.
[0096] S5: As Figure 6f As shown, the first sub-bonding layer 31 and the second sub-bonding layer 32 are bonded together to form a bonding layer 30, such that the first epitaxial stack 40 is bonded to the transparent dielectric layer 20 on the side away from the first substrate 10 through the bonding layer 30, and the refractive index of the transparent dielectric layer 20 is greater than the refractive index of the bonding layer 30.
[0097] Optionally, the bonding layer 30 includes a stack of one or more of the following: a silicon oxide layer, a silicon nitride layer, an aluminum oxide layer, and a silicon oxynitride layer.
[0098] At this time, in the first epitaxial stack 40, the stacking order along the direction away from the first substrate 10 is a first type semiconductor layer 41, an active layer 42, and a second type semiconductor layer 43.
[0099] S6: Remove growth substrate 101.
[0100] Furthermore, the method for fabricating this flip-chip LED may also include:
[0101] S7: As Figure 6g As shown, mesa etching is performed on the side of the first epitaxial stack 40 away from the first substrate 10, so that the side of the first epitaxial stack 40 away from the first substrate 10 has a first groove U1, and the first groove U1 exposes a portion of the first type semiconductor layer 41.
[0102] Specifically, the first groove U1 may penetrate only the second type semiconductor layer 43 and the active layer 42 to expose part of the first type semiconductor layer 41, or the first groove U1 may penetrate the second type semiconductor layer 43, the active layer 42 and part of the first type semiconductor layer 41 to expose part of the first type semiconductor layer 41.
[0103] S8: As Figure 6h As shown, the first epitaxial stack 40 is deeply etched to create an isolation channel W1, which exposes the bonding layer 30.
[0104] It is understandable that the isolation channel W1 can isolate different first epitaxial layers 40, and different first epitaxial layers 40 correspond to different flip-chip LEDs.
[0105] S9: such as Figure 6i As shown, a first electrode D1 is formed on the surface of the first type semiconductor layer 41 exposed in the first groove U1, and the first electrode D1 is electrically connected to the first type semiconductor layer 41; and a second electrode D2 is formed on the side of the second type semiconductor layer 43 away from the first substrate 10, and the second electrode D2 is electrically connected to the second type semiconductor layer 43.
[0106] S10: As Figure 6j As shown, a first insulating reflective layer 50 is formed from the side of the first epitaxial stack 40 away from the first substrate 10. The first insulating reflective layer 50 covers the first epitaxial stack 40 and is etched to make the first insulating reflective layer 50 have a first through hole K1 and a second through hole K2. The first through hole K1 exposes at least a portion of the first electrode D1, and the second through hole K2 exposes at least a portion of the second electrode D2.
[0107] S11: As Figure 1 and Figure 2 As shown, a first pad P1 and a second pad P2 are formed on the side of the first insulating reflective layer 50 away from the first substrate 10. The first pad P1 is electrically connected to the first electrode D1 through the first through hole K1, and the second pad P2 is electrically connected to the second electrode D2 through the second through hole K2.
[0108] It can be understood that the first insulating reflective layer 50 can reflect the light emitted by the epitaxial stack 40 (mainly the active layer 42) in the direction away from the first substrate 10 back to the side of the first substrate 10 for emission, so as to improve the light-emitting efficiency of the flip LED chip.
[0109] In addition, the display module provided by the embodiment of the present application comprises a substrate and a plurality of first flip LED chips and a plurality of second flip LED chips located on one side of the substrate; wherein the first flip LED chip is the flip LED chip provided by any one of the foregoing embodiments, and optionally, the first flip LED chip can be a quaternary red flip LED chip.
[0110] The cross-sectional structure of the second flip LED chip is shown in Figure 7 The second flip LED chip comprises a second substrate 200, the second substrate 200 has oppositely arranged third and fourth surfaces S3 and S4, the third surface S3 of the second substrate 200 has a plurality of second micro-pattern structures T2, and the fourth surface S4 of the second substrate 200 is the light-emitting surface of the second flip LED chip; a buffer layer 210 is arranged on one side of the third surface S3 of the second substrate 200, the thickness of the buffer layer 210 is not less than the height of the second micro-pattern structure T2, that is, the buffer layer 210 can fill the plurality of second micro-pattern structures T2 of the third surface S3 of the second substrate 200, or the buffer layer 210 can also cover the plurality of second micro-pattern structures T2 of the third surface S3 of the second substrate 200; a second epitaxial stack 220 is arranged on one side of the buffer layer 210 away from the second substrate 200.
[0111] Specifically, the second epitaxial stack 220 can comprise an N-type semiconductor layer 221, an active layer 222 and a P-type semiconductor layer 223 stacked in the direction away from the second substrate 200, wherein the N-type semiconductor layer 221 can be an N-type GaN layer, and the P-type semiconductor layer 223 can be a P-type GaN layer.
[0112] As shown in Figure 7 In the second flip LED chip, the second epitaxial stack 220 has a second groove U2 on one side thereof away from the second substrate 200, the second groove U2 exposes part of the N-type semiconductor layer 221; an N-type electrode 241 is arranged on the surface of the N-type semiconductor layer 221 exposed by the second groove U2; a transparent conductive layer 230 is arranged on one side of the P-type semiconductor layer 223 away from the second substrate 200, the transparent conductive layer 230 can function to laterally spread the current, and a P-type electrode 242 is arranged on one side of the transparent conductive layer 230 away from the second substrate 200.
[0113] As shown in Figure 7As shown, the second flip LED chip can further include a second insulating reflective layer 250 covering the second epitaxial layer 220 and the transparent conductive layer 230, the second insulating reflective layer 250 having a third through hole K3 and a fourth through hole K4, the third through hole K3 exposing at least part of the N-type electrode 241, and the fourth through hole K4 exposing at least part of the P-type electrode 242; the second insulating reflective layer 250 is provided with a third pad 261 and a fourth pad 262 on the side away from the second substrate 200, wherein the third pad 261 is electrically connected to the N-type electrode 241 through the third through hole K3, and the fourth pad 262 is electrically connected to the P-type electrode 242 through the fourth through hole K4.
[0114] It can be understood that the second substrate 200 is a growth substrate of the second epitaxial layer 220, that is, after the plurality of second micro-pattern structures T2 are formed on the third surface S3 of the second substrate 200, the buffer layer 210 is first formed, and then the second epitaxial layer 220 and subsequent structures are formed.
[0115] It can also be understood that the second flip LED chip can be a blue flip LED chip or a green flip LED chip, and the light emitted by the second epitaxial layer 220 (mainly the active layer 222) is emitted from the fourth surface S4 of the second substrate 200 after passing through the buffer layer 210 and the second substrate 200. Since the third surface S3 of the second substrate 200 has a plurality of second micro-pattern structures T2, the light can be scattered and refracted, and therefore the light-emitting angle of the second flip LED chip can also be large. The second micro-pattern structure T2 can be set with reference to the first micro-pattern structure T1, and will not be described again.
[0116] In the display module, the first flip LED chip can adopt the structure shown in Figure 1 or Figure 2 to emit red light; and the second flip LED chip can adopt the structure shown in Figure 7 to emit blue light or green light, so that the light-emitting angles of the first flip LED chip and the second flip LED chip in the display module can both be large, for example, the light-emitting angles are both 140°-150°, thereby improving the display effect of the display module.
[0117] In this specification, each part is described in a parallel and progressive manner, and each part mainly explains the difference from other parts. The same or similar parts between each part can be referred to each other.
[0118] The above description of disclosed embodiments, the features recited in the description of the embodiments herein can be replaced or combined with each other, so that those skilled in the art can realize or use the present application. Various modifications of these embodiments will be apparent to those skilled in the art, and the general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the present application. Therefore, the present application will not be limited to the embodiments shown herein, but will conform to the widest scope consistent with the principles and novel features disclosed herein.
Claims
1. A flip-chip LED, characterized in that, include: A first substrate has a first surface and a second surface disposed opposite to each other. The first surface has a plurality of first micro-pattern structures, and the second surface is the light-emitting surface of the flip-chip LED. A transparent dielectric layer located on one side of the first surface of the first substrate, wherein the thickness of the transparent dielectric layer is not less than the height of the first micro-pattern structure, and the refractive index of the transparent dielectric layer is greater than the refractive index of the first substrate; A bonding layer located on the side of the transparent dielectric layer opposite to the first substrate, wherein the refractive index of the transparent dielectric layer is greater than the refractive index of the bonding layer; The first epitaxial layer is located on the side of the bonding layer opposite to the first substrate.
2. The flip-chip LED according to claim 1, characterized in that, The first substrate includes a sapphire substrate.
3. The flip-chip LED according to claim 1, characterized in that, The first micro-pattern structure includes a micro-protrusion structure or a micro-groove structure.
4. The flip-chip LED according to claim 1, characterized in that, The transparent dielectric layer comprises one or more stacks of gallium nitride, zinc germanium, zinc sulfide, and titanium dioxide.
5. The flip-chip LED according to claim 1, characterized in that, The bonding layer comprises a stack of one or at least two of the following: a silicon oxide layer, a silicon nitride layer, an aluminum oxide layer, and a silicon oxynitride layer.
6. The flip-chip LED according to claim 1, characterized in that, The first epitaxial stack includes a first type semiconductor layer, an active layer, and a second type semiconductor layer stacked along a direction away from the first substrate. The first epitaxial stack has a first groove on the side away from the first substrate, and the first groove exposes a portion of the first type semiconductor layer. A first electrode is disposed on the surface of the first type semiconductor layer exposed in the first groove; A second electrode is disposed on the side of the second type semiconductor layer that is away from the first substrate.
7. The flip-chip LED according to claim 6, characterized in that, The flip-chip LED also includes: A first insulating reflective layer extends from the side of the first epitaxial stack away from the first substrate and covers the first epitaxial stack. The first insulating reflective layer has a first through-hole and a second through-hole. The first through-hole exposes at least a portion of the first electrode, and the second through-hole exposes at least a portion of the second electrode. The first pad and the second pad are located on the side of the first insulating reflective layer opposite to the first substrate. The first pad is electrically connected to the first electrode through the first through hole, and the second pad is electrically connected to the second electrode through the second through hole.
8. The flip-chip LED according to any one of claims 1-7, characterized in that, The flip-chip LED is a red flip-chip LED.
9. The flip-chip LED according to claim 6, characterized in that, The first epitaxial stack comprises a III-V compound semiconductor material, and the active layer comprises a quaternary semiconductor material.
10. A display module, characterized in that, include: substrate; A plurality of first flip-chip LEDs and a plurality of second flip-chip LEDs are located on one side of the substrate, wherein the first flip-chip LEDs are the flip-chip LEDs according to any one of claims 1-9.
11. The display module according to claim 10, characterized in that, The second flip-chip LED includes: The second substrate has a third surface and a fourth surface disposed opposite to each other. The third surface has a plurality of second micro-pattern structures, and the fourth surface is the light-emitting surface of the second flip-chip LED. A buffer layer located on one side of the third surface of the second substrate, the thickness of the buffer layer being not less than the height of the second micro-pattern structure; The second epitaxial layer is located on the side of the buffer layer opposite to the second substrate.
12. A method for fabricating a flip-chip LED, characterized in that, include: A first substrate is provided, the first substrate having a first surface and a second surface disposed opposite to each other, and a plurality of first micro-pattern structures are formed on the first surface of the first substrate; A transparent dielectric layer is formed on one side of the first surface of the first substrate, the thickness of the transparent dielectric layer is not less than the height of the first micro-pattern structure, and the refractive index of the transparent dielectric layer is greater than the refractive index of the first substrate. A first sub-bonding layer is formed on the side of the transparent dielectric layer opposite to the first substrate; A stacked structure is provided, the stacked structure including a growth substrate and a first epitaxial stack located on one side of the growth substrate, and a second sub-bonding layer is formed on the side of the first epitaxial stack opposite to the growth substrate; The first sub-bonding layer and the second sub-bonding layer are bonded together to form a bonding layer, such that the first epitaxial stack is bonded to the transparent dielectric layer on the side away from the first substrate through the bonding layer, and the refractive index of the transparent dielectric layer is greater than the refractive index of the bonding layer. Remove the growth substrate.