LED chip, manufacturing method thereof, and LED display device

Abstract

The application provides an LED chip, a manufacturing method thereof and an LED display device, wherein an epitaxial structure of the LED chip is formed with a recess structure with an inner recess, a side wall of the recess structure has an included angle with a normal direction of a light emitting surface of the LED chip, so that the side wall of the recess structure is an inclined side wall, when light emitted by the LED chip is scattered to the inclined side wall, the inclined side wall is aligned to reflect and gather, so that the light emitted by the LED is as much as possible to be limited in the normal direction, thereby greatly reducing the light emitting angle of the LED chip, increasing the light emitting amount in the normal direction of the LED chip and the light emitting efficiency of the LED chip. In addition, the above structure and the reflection structure on the electrode side of the LED chip jointly act, further increase the reflection of the light emitted by the LED, and can further increase the light emitting amount in the normal direction of the LED chip and the light emitting efficiency of the LED chip. The display device of the application comprises the above LED chip, and the above LED chip can improve the display effect of the display device, and is also beneficial to reduce the power consumption of the display device.

Description

Technical Field

[0001] This invention relates to the field of semiconductor device technology, and in particular to an LED chip and its manufacturing method. Background Technology

[0002] LEDs have gained widespread attention due to their high luminous efficiency, long lifespan, safety, reliability, and energy efficiency. Micro LED chips, in particular, are typically substrate-free LED chips. In existing technologies, after forming the epitaxial layer of an LED chip, plasma etching is commonly used to create mesas or holes in the epitaxial layer to achieve electrical connection between the P / N electrodes and the semiconductor layer. Metal stacks are then fabricated within these mesas or holes to serve as electrodes.

[0003] When current flows from the P electrode to the N electrode, it induces electron flare in the light-emitting layer, causing light emission. However, the current causes the emitted light to lack directionality, i.e., it is diffuse light. To improve the utilization rate of the light emitted by the light-emitting layer, a reflective layer or mirror is usually fabricated on the electrode side of the LED chip to reflect the diffused light back to the light-emitting surface of the LED chip, thereby achieving better light utilization. However, even with the above-mentioned reflective layer or mirror, the light emission angle of the LED chip is still around + / - 70 degrees, and the optimal light emission angle still does not reach the normal angle of the light-emitting surface (i.e., 0 degrees).

[0004] Therefore, there is an urgent need for a solution to improve the light emission angle of micro LED chips and enhance the luminous efficiency of LED chips. Summary of the Invention

[0005] In view of the above-mentioned problems existing in LED chips, especially micro LED chips, the present invention provides an LED chip and its manufacturing method. In the present invention, the epitaxial layer of the LED chip has an indented groove structure. The sidewall of the groove structure has a certain tilt angle with the normal direction of the light-emitting surface of the LED chip. Thus, when the light emitted by the LED chip is scattered to the sidewall, the sidewall reflects the light and concentrates it in the normal direction, thereby further optimizing the light emission angle of the LED chip and increasing the light utilization rate.

[0006] According to one embodiment of the present invention, an LED chip is provided, the LED chip comprising:

[0007] An epitaxial structure includes a first semiconductor layer, an active layer, and a second semiconductor layer with a conductivity type opposite to that of the first semiconductor layer. The epitaxial structure has a groove structure that is recessed from the first semiconductor layer toward the second semiconductor layer, and the surface of the groove structure forms the light-emitting surface of the LED chip.

[0008] Optionally, the cross-section of the groove structure is an inverted trapezoid.

[0009] Optionally, the angle between the sidewall of the groove structure and the normal direction of the light-emitting surface of the epitaxial structure is between 15° and 65°.

[0010] Optionally, the ratio of the depth of the groove structure to the thickness of the LED chip is between 0.1 and 0.45.

[0011] Optionally, the LED chip further includes an electrode structure, the electrode structure including a first electrode electrically connected to the first semiconductor layer and a second electrode electrically connected to the second semiconductor layer.

[0012] Optionally, the system further includes a reflective structure formed between the electrode structure and the epitaxial structure. This reflective structure, together with the aforementioned groove structure of the epitaxial structure, further optimizes the light emission angle of the LED chip and increases light utilization.

[0013] According to another embodiment of the present invention, a method for manufacturing an LED chip is provided, the method comprising the following steps:

[0014] A growth substrate is provided, and a protrusion is formed on the growth substrate by etching.

[0015] An epitaxial structure is formed by sequentially growing a first semiconductor layer, an active layer, and a second semiconductor layer with the opposite conductivity type to the first semiconductor layer on the growth substrate.

[0016] The growth substrate is peeled off to obtain an LED chip with a groove structure corresponding to the protrusion.

[0017] Optionally, the cross-sectional shape of the protrusion formed on the growth substrate is trapezoidal.

[0018] Optionally, the angle between the sidewall of the protrusion formed on the growth substrate and the normal direction of the substrate surface is between 15° and 65°.

[0019] Optionally, the ratio of the height of the protrusion to the thickness of the LED chip is between 0.1 and 0.45.

[0020] Optionally, the method for manufacturing the LED chip further includes the following steps:

[0021] The epitaxial structure on the growth substrate on both sides of the protrusion structure is etched until the growth substrate is exposed to form an isolation trench, which separates the epitaxial structure into discrete structures.

[0022] Optionally, the method for manufacturing the LED chip further includes the following steps:

[0023] A reflective structure is formed on the surface and sidewalls of the epitaxial structure other than the first electrode structure and the second electrode structure.

[0024] According to another embodiment of the present invention, an LED display device is provided, comprising:

[0025] Circuit board; and

[0026] A light-emitting device located on the circuit board, the light-emitting device being soldered to the board through the circuit layer, wherein the light-emitting device includes the LED chip described in this invention.

[0027] As described above, the LED chip and its manufacturing method of the present invention have the following beneficial effects:

[0028] The LED chip provided by this invention has an epitaxial structure with a recessed groove structure. The sidewall of this groove structure forms an angle with the normal direction of the light-emitting surface of the LED chip, making the sidewall of the groove structure an inclined sidewall. When light emitted by the LED chip is scattered to the inclined sidewall, the inclined sidewall aligns and reflects and focuses the light, confining the emitted light as much as possible to the normal direction. This greatly reduces the light emission angle of the LED chip, increases the amount of light emitted in the normal direction, and improves the light extraction efficiency of the LED chip. Furthermore, the above structure, together with the reflective structure on the electrode side of the LED chip, further increases the reflection of the light emitted by the LED, further increasing the amount of light emitted in the normal direction and the light extraction efficiency of the LED chip. Display devices including the above-mentioned LED chip therefore have better display effects and the advantage of low power consumption.

[0029] This invention involves etching a growth substrate to form protrusions, then growing an epitaxial structure on the substrate, and finally peeling off the growth substrate using laser lift-off technology to form an LED chip with a groove structure complementary to the protrusions. This method achieves the above structure through substrate processing, resulting in a simple process and cost savings. Attached Figure Description

[0030] Figure 1 The diagram shows the structure of an LED chip in the prior art.

[0031] Figure 2 The diagram shown is a structural schematic of an LED chip provided in an embodiment of the present invention.

[0032] Figure 3 The diagram shows a process flow diagram of a method for manufacturing an LED chip according to another embodiment of the present invention.

[0033] Figure 4The diagram shown is a schematic representation of the provided substrate.

[0034] Figure 5 Displayed as in Figure 4 A schematic diagram showing the formation of an epitaxial structure on the substrate.

[0035] Figure 6 Displayed as in Figure 5 The diagram shows an isolation groove formed in the epitaxial structure.

[0036] Figure 7 Displayed as in Figure 6 A schematic diagram showing the electrode structure formed above the structure shown.

[0037] Figure 8 Displayed as in Figure 7 A schematic diagram showing a reflective structure formed above the structure shown.

[0038] Figure 9 The diagram shown is a structural schematic of an LED display device provided in another embodiment of the present invention.

[0039] Component designation explanation

[0040] 01 Epitaxial layer 103 Second semiconductor layer 011 N-type semiconductor layer 104 First electrode 012 Active layer 105 Second electrode 013 P-type semiconductor layer 106 Isolation trench 021 N electrode 107 Countertop structure 022 P electrode 110 Groove structure 100 Epitaxial structure 200 Growth substrate 101 First semiconductor layer 201 Protrusion 102 Active layer 300 Reflective structure 400 LED display devices 402 Circuit board 401 face mask 403 LED indicator lights Detailed Implementation

[0041] The following specific examples illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and various details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention.

[0042] like Figure 1As shown, a conventional substrate-free micro LED chip includes an epitaxial layer 01, which comprises an N-type semiconductor layer 011, an active layer 012, and a P-type semiconductor layer 013, as well as N-electrodes 021 and P-electrodes 022 electrically connected to the N-type and P-type semiconductor layers, respectively. These N-electrodes and P-electrodes are typically formed on the mesa formed by etching the epitaxial layer, or in the holes formed by etching the epitaxial layer. When current flows from the P-electrode 022 to the N-electrode 021, the current induces electron flare in the light-emitting layer, resulting in light emission. However, the current causes the light emitted by the light-emitting layer to lack directionality, i.e., the emitted light is divergent. To improve the utilization rate of the light emitted by the light-emitting layer, a reflective layer or mirror is typically fabricated on the electrode side of the LED chip to reflect the divergent light back to the light-emitting surface of the LED chip, thereby achieving better light utilization. However, even with the aforementioned reflective layer or mirror, the light emission angle of the LED chip is still around + / -70 degrees, and the optimal light emission angle still cannot reach the normal angle of the light emission surface (i.e., 0 degrees).

[0043] Example 1

[0044] To address the aforementioned deficiencies in the prior art, this embodiment provides an LED chip, preferably a micro LED chip with a size of less than 75 μm. For example... Figure 2 As shown, the LED chip includes an epitaxial structure 100, which includes a first semiconductor layer 101, an active layer 102, and a second semiconductor layer 103. The first semiconductor layer can be an N-type semiconductor layer, and the second semiconductor layer can be a P-type semiconductor layer. It is understood that a transparent conductive layer or similar structure can also be formed above the second semiconductor layer. Of course, it is also possible for the first semiconductor layer to be a P-type semiconductor layer and the second semiconductor layer to be an N-type semiconductor layer. In an optional embodiment, the first semiconductor layer 101 can be an n-type GaN layer, the active layer 102 can be a quantum well layer, and the second semiconductor layer can be a p-type GaN layer. Alternatively, the first semiconductor layer 101 can be an n-type GaN layer, such as a Si-doped GaN layer; the active layer 102 can be an InGaN / GaN multiple quantum well layer; and the second semiconductor layer can be a p-type GaN layer, such as a Mg-doped GaN layer.

[0045] Similarly, refer to Figure 2In this embodiment, the epitaxial structure 100 of the LED chip has a recessed structure 110, which is recessed from the first semiconductor layer 101 towards the second semiconductor layer 103. The surface of the recessed structure 110 forms the light-emitting surface of the LED chip. Correspondingly, on the side opposite to the light-emitting surface, the epitaxial structure 100 forms a protrusion corresponding to the recessed structure 110. That is, the first semiconductor layer 101, the active layer 102, and the second semiconductor layer 103 of the epitaxial structure 100 are recessed from the first semiconductor layer 101 towards the second semiconductor layer 103. Preferably, the ratio of the depth of the recessed structure 110 to the thickness of the LED chip is between 0.1 and 0.45. Taking a micro LED chip as an example, the thickness of the epitaxial structure is approximately 3 μm to 5 μm, and in this case, the height of the recessed structure 110 is approximately 0.3 μm to 2 μm. The ratio of the groove structure 110 to the LED chip thickness ensures that the groove structure 110 can be effectively formed during the formation of the aforementioned epitaxial structure. This avoids the risk of insufficient light concentration due to an excessively shallow groove structure 110, or uneven film formation or film breakage at the corners due to an excessively deep groove structure 110. For example... Figure 2 As shown, the cross-section of the groove structure 110 (i.e., the cross-section along the thickness direction of the LED chip) is formed as an inverted trapezoid. The angle α between the sidewall of the inverted trapezoidal groove structure and the normal direction of the light-emitting surface of the LED chip is between 15° and 65°. This angle setting can ensure that the sidewall effectively reflects the light emitted by the LED chip while ensuring the film uniformity during the formation of the epitaxial structure. Due to the groove structure 110, when the light emitted by the LED chip is scattered to the sidewall of the groove structure 110, it will be reflected by the sidewall. After multiple reflections, the emitted light is concentrated in the normal direction, thereby achieving a light-focusing effect, increasing the amount of light emitted in the normal direction of the LED chip, and increasing the light extraction efficiency.

[0046] The LED chip also includes an electrode structure, similarly referring to... Figure 2 The electrode structure includes a first electrode 104 electrically connected to a first semiconductor layer 101 and a second electrode 105 electrically connected to a second semiconductor layer 103. The first electrode 104 is formed on both sides of the groove structure 110. For example, by dry etching, mesas or holes exposing the first semiconductor layer are formed in the epitaxial structures on both sides of the groove structure. Then, a metal material, such as Au, Ag, Al, Cu, Zn, etc., is deposited in the mesas or holes to form the first electrode. In this embodiment, as... Figure 2As shown, mesa structures 107 exposing the first semiconductor layer are formed on both sides of the groove structure 110, and the first electrode 104 is formed above the mesa structure 107. A second electrode is formed on the epitaxial structure corresponding to the groove structure 110. For example, it can be formed by dry etching to create holes exposing the second semiconductor layer in the epitaxial structure, and then depositing a metal material, such as Au, Ag, Al, or Cu, in the holes to form the second electrode structure. Although not shown, a transparent conductive layer and a current-blocking layer are also formed between the second electrode and the second semiconductor layer.

[0047] In addition, to concentrate and reflect the light emitted from the active layer of the chip to the light-emitting surface and improve the light extraction efficiency, a reflective structure 300 is formed on the surface of the epitaxial structure on one side of the electrode structure. This reflective structure 300 can be a DBR reflective layer formed by alternating stacks of TiO2 / SiO2. Alternatively, it can be a total internal reflection mirror (ODR) structure, which may include a DBR reflective layer, an Al reflective layer, and an insulating layer formed on top of the epitaxial structure.

[0048] In this embodiment, the sidewalls of the aforementioned groove structure of the LED chip are inclined sidewalls. When light emitted from the LED chip is scattered to these inclined sidewalls, the sidewalls align and reflect and concentrate the light, confining the emitted light as much as possible to the normal direction. This significantly reduces the emission angle of the LED chip, increases the amount of light emitted in the normal direction, and enhances the light extraction efficiency of the LED chip. Furthermore, the above structure, together with the reflective structure on the electrode side of the LED chip, further increases the reflection of light emitted from the LED, thereby further increasing the amount of light emitted in the normal direction and the light extraction efficiency of the LED chip.

[0049] Example 2

[0050] This embodiment provides a method for manufacturing an LED chip, such as... Figure 3 As shown, the method includes the following steps:

[0051] S101: Provide a growth substrate and etch the growth substrate to form a protrusion on the growth substrate;

[0052] like Figure 4As shown, firstly, a growth substrate 200 suitable for growing a light-emitting epitaxial structure, such as a sapphire substrate, is provided. Then, the growth substrate 200 is etched to form a plurality of protrusions 201 on the growth substrate 200. The plurality of protrusions 201 are arranged at intervals on the growth substrate 200, and the cross-section of the protrusions 201 is trapezoidal. The sidewalls of the protrusions 201 form an angle β with the normal direction of the surface of the growth substrate 200, the angle β being between 15° and 65°. The ratio of the height of the protrusions 201 to the thickness of the subsequent epitaxial structure grown on the growth substrate 200 is between 0.1 and 0.45. Taking a micro LED chip as an example, the thickness of the subsequently formed epitaxial structure is approximately 3 μm to 5 μm; in this case, the height of the protrusions 201 is set to approximately 0.3 μm to 2 μm. The aforementioned tilt angle and height of the protrusion ensure that the epitaxial structure of the subsequent LED chip is uniformly formed on the growth substrate, and there is no risk of uneven film layer or film layer breakage due to the protrusion being too high or the tilt angle being too large or too small.

[0053] S102: A first semiconductor layer, an active layer, and a second semiconductor layer with the opposite conductivity type to the first semiconductor layer are sequentially grown on the growth substrate to form an epitaxial structure;

[0054] like Figure 5 As shown, a first semiconductor layer 101, an active layer 102, and a second semiconductor layer 103 are sequentially deposited on a growth substrate 200 to form a light-emitting epitaxial structure 100. In an optional embodiment of this example, the first semiconductor layer is an n-type GaN layer, such as a Si-doped GaN layer; the active layer is an InGaN / GaN multiple quantum well layer; and the second semiconductor layer is a p-type GaN layer, such as a Mg-doped GaN layer. Optionally, a buffer layer, such as a low-temperature GaN buffer layer, may be formed on the growth substrate before growing the first semiconductor layer.

[0055] After that, as Figure 6 As shown, after forming the epitaxial structure described above, the epitaxial structure located on both sides of the protrusion 201 on the growth substrate 200 is etched until the growth substrate 200 is exposed to form an isolation trench 106, which divides the epitaxial structure into several discrete structures. Then, as... Figure 7As shown, a first electrode 104 and a second electrode 105 are formed in each discrete structure. In an optional embodiment, firstly, the epitaxial structures on both sides of the protrusion structure of each discrete structure are etched to form a mesa structure 107 exposing the first semiconductor layer 101. A metal material, such as Au, Ag, Al, Cu, Zn, etc., is deposited on the mesa structure 107 to form the first electrode 104. Then, the epitaxial structure above the protrusion 201 is etched to form a hole in the second semiconductor layer. A metal material, such as Au, Ag, Al, Cu, Zn, etc., is deposited in the hole to form the second electrode 105. After forming the first and second electrodes, as shown... Figure 8 As shown, after forming the aforementioned electrodes, a reflective structure 300 is formed on the surface of the epitaxial structure other than the first and second electrodes. This reflective structure is also formed on the sidewalls of the epitaxial structure. A DBR reflective layer can be formed by alternately stacking TiO2 / SiO2 on the surface and sidewalls of the epitaxial structure. Alternatively, a total reflection mirror (ODR) structure can be formed by sequentially placing a DBR reflective layer, an Al reflective layer, and an insulating layer on top of the epitaxial structure.

[0056] S103: Peel off the growth substrate to obtain an LED chip with a groove structure that is complementary to the protrusion.

[0057] form Figure 8 After the structure shown, the growth substrate 200 is peeled off to obtain an LED chip having a groove structure 110 that is complementary to the protrusion 201 of the growth substrate 200.

[0058] Taking a GaN epitaxial structure as an example, the structure formed in step S103 is first transferred to a Si substrate. Then, laser lift-off technology is used to remove the growth substrate. For example, ultraviolet light with a wavelength of about 280 nm is used to irradiate the interface between the growth substrate and the epitaxial structure. After absorbing the ultraviolet light, GaN dissociates into Ga and nitrogen gas, thus separating the growth substrate from the epitaxial structure. At the interface between the protrusion and the epitaxial structure, the epitaxial structure at the corner of the protrusion can be completely separated from the growth substrate by increasing the laser irradiation or changing the laser path. After the epitaxial structure is separated from the growth substrate, hydrochloric acid solution can be used to remove the residual Ga in the GaN layer, resulting in a good epitaxial layer surface.

[0059] As described above, this embodiment involves etching a growth substrate to form protrusions, then growing an epitaxial structure on the substrate, and finally peeling off the growth substrate using laser lift-off technology to form an LED chip with a groove structure complementary to the protrusions. This method obtains the above structure through substrate processing, resulting in a simple process and cost savings.

[0060] Example 3

[0061] This embodiment provides a display device, such as... Figure 9 As shown, the display device 400 of this embodiment includes a face mask 401, a circuit board 402, and a plurality of LED display lights 403. The LED display lights 403 are disposed on the circuit board 402. Figure 9 The diagram illustrates an LED display lamp arranged in a rectangular array on the circuit board 402. This is merely exemplary and not limiting; the LED display lamps 403 can be arranged on the circuit board 402 in various suitable or desired configurations. The aforementioned LED display lamps 403 are composed of LED chips as described in Embodiments 1 to 2 of the present invention. The LED chips are sorted and binned, and then connected to the circuit board 402 via pads. The circuit board 402 can be a TFT substrate or a PCB circuit board.

[0062] The display device in this embodiment also includes a bottom shell (not shown in detail), and a circuit board is sandwiched between the face mask and the bottom shell. The face mask and the bottom shell are fixed to each other to form a cavity for accommodating the circuit board and the LED display lamp.

[0063] The aforementioned display device includes the LED chip of the present invention, which can improve the display effect of the display device and at the same time help reduce the power consumption of the display device.

[0064] The above embodiments are merely illustrative of the principles and effects of the present invention and are not intended to limit the invention. Any person skilled in the art can modify or alter the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or alterations made by those skilled in the art without departing from the spirit and technical concept disclosed in the present invention should still be covered by the claims of the present invention.

Claims

1. An LED chip, characterized in that, include: An epitaxial structure includes a first semiconductor layer, an active layer, and a second semiconductor layer with a conductivity type opposite to that of the first semiconductor layer. The epitaxial structure has a groove structure that is recessed from the first semiconductor layer toward the second semiconductor layer. The cross-section of the groove structure is an inverted trapezoid, and the surface of the groove structure forms the light-emitting surface of the LED chip. The angle between the sidewall of the groove structure and the normal direction of the light-emitting surface of the epitaxial structure is between 15° and 65°; the ratio of the depth of the groove structure to the thickness of the LED chip is between 0.1 and 0.

45. The electrode structure includes a first electrode electrically connected to the first semiconductor layer and a second electrode electrically connected to the second semiconductor layer. The first electrode is located on both sides of the groove structure, and the first electrodes on both sides of the groove structure have a height difference.

2. The LED chip according to claim 1, characterized in that, It also includes a reflective structure formed between the electrode structure and the epitaxial structure.

3. A method for manufacturing an LED chip, characterized in that, Includes the following steps: A growth substrate is provided, and the growth substrate is etched to form a protrusion on the growth substrate. The protrusion has a trapezoidal cross-sectional shape, and the angle between the sidewall of the protrusion and the normal direction of the substrate surface is between 15° and 65°. The ratio of the height of the protrusion to the thickness of the LED chip is between 0.1 and 0.

45. An epitaxial structure is formed by sequentially growing a first semiconductor layer, an active layer, and a second semiconductor layer with the opposite conductivity type to the first semiconductor layer on the growth substrate. A first electrode is formed on both sides of the protrusion, and a second electrode is formed above the protrusion. The first electrodes located on both sides of the protrusion have a height difference. The growth substrate is peeled off to obtain an LED chip with a groove structure that is complementary to the protrusion. The surface of the groove structure forms the main light-emitting surface of the LED chip.

4. The method for manufacturing an LED chip according to claim 3, characterized in that, It also includes the following steps: The epitaxial structure above the growth substrate on both sides of the protrusion is etched until the growth substrate is exposed to form an isolation trench, which separates the epitaxial structure into discrete structures.

5. The method for manufacturing an LED chip according to claim 3, characterized in that, It also includes the following steps: A reflective structure is formed on the surface and sidewalls of the epitaxial structure, excluding the first electrode and the second electrode.

6. An LED display device, characterized in that, include: Circuit board; as well as A light-emitting device located on the circuit board, the light-emitting device being soldered to the board through a circuit layer, wherein the light-emitting device includes an LED chip as described in any one of claims 1 to 2.

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