TWI875219B - Light-emitting device - Google Patents

Abstract

A light-emitting device is provided. The light-emitting device includes a light-emitting diode (LED) die, the LED die includes: a semiconductor layer and a first electrode, the first electrode is located on the front side of the LED die and electrically connected with the semiconductor layer, wherein the LED die has an emission light emitted from the semiconductor layer; a first reflective layer and a second reflective layer, the first and second reflective layers are sequentially stacked on the front side of the LED die, and the first reflective layer and the second reflective layer are disposed between the semiconductor layer and the first electrode, wherein the first reflective layer is configured to reflect the emission light emitted from the LED die, and the second reflective layer is configured to reflect a laser from outside, and a wavelength of the laser is less than 420nm.

Description

Light emitting device

The present disclosure relates to a light emitting device, and more particularly to a light emitting device including a reflective layer.

Light-emitting diodes (LEDs) are light-emitting devices that emit light when voltage is applied. Nitride LEDs are often used as semiconductor optical elements that produce blue or green light. Taking into account the lattice matching of the compound, nitride semiconductor materials are generally grown on a sapphire substrate, and then an electrode structure is formed to form a nitride LED. However, the sapphire substrate has high hardness, low thermal conductivity and low electrical conductivity. It not only has electrostatic problems, but is also the main factor limiting the heat dissipation of the original regular LED chip; in addition, in the original regular LED structure, the electrode will block part of the light and reduce the luminous efficiency. Therefore, the flip chip structure of LED has gradually developed.

The most common LED flip chip technology currently is to flip the prepared LED chip and then solder it to the package substrate. Since the chip is flipped, the heat conduction path can be directly conducted from the semiconductor layer to the package substrate, which can avoid the problem of poor heat dissipation of the sapphire substrate. In addition, traditionally, during the flip chip technology period, a series of processes are used to form an array of LED chips, and a pick-up head is used to select or transfer one chip from one carrier to another. However, the traditional process may encounter some difficulties. For example, the side length of the micro-LED die is smaller than the minimum size limit of the selection head, resulting in the inability to effectively pick up the LED chip. For example, the miniaturization of the die size means that the number of die that can be formed on the same size wafer will increase dramatically. The one-to-one picking method in the traditional process will inevitably be unable to meet the demand for mass transfer of LED chips, resulting in a decrease in the yield of LEDs.

In the evolution of mass transfer LED chip technology, in order to meet the high efficiency requirements and achieve higher production capacity, selective laser lift-off (selective LLO) technology is used to replace the traditional process. However, although the existing selective laser lift-off technology can generally meet the requirements, it is not satisfactory in all aspects. Therefore, there is still a need to improve the selective laser lift-off technology and the structure and formation method of the light-emitting device to manufacture a light-emitting device that meets product requirements.

According to some embodiments of the present disclosure, a light-emitting device is provided. The light-emitting device includes: a first-type light-emitting diode die, including a semiconductor layer and a first electrode, the first electrode is located at the front side of the first-type light-emitting diode die and electrically connected to the semiconductor layer, wherein the first-type light-emitting diode die has an output light, which is emitted from the inside of the semiconductor layer; a first reflective layer and a second reflective layer, which are sequentially stacked at the front side of the first-type light-emitting diode die, and the first reflective layer and the second reflective layer are located between the semiconductor layer and the first electrode, wherein the first reflective layer is used to reflect the output light from the inside of the first-type light-emitting diode die, and the second reflective layer is used to reflect the laser light from the outside, and the wavelength of the laser light is less than 420nm.

The following embodiments provide a detailed description with reference to the accompanying drawings.

The following describes the light emitting device and its forming method of the disclosed embodiment. However, it should be understood that the disclosed embodiment provides many suitable inventive concepts and can be implemented in a wide variety of specific contexts. The disclosed specific embodiment is only used to illustrate the manufacture and use of the invention in a specific method, and is not used to limit the scope of the invention. Furthermore, the same reference numerals are used in the drawings and descriptions of the disclosed embodiment to represent the same or similar components.

In addition, the present disclosure provides many embodiments or examples for implementing different elements of the subject matter provided. Specific examples of each element and its configuration are described below to simplify the description of the embodiments of the present invention. Of course, these are merely examples and are not intended to limit the embodiments of the present invention. For example, if the description refers to a first element formed on a second element, it may include an embodiment in which the first and second elements are directly in contact, and it may also include an embodiment in which an additional element is formed between the first and second elements so that they are not in direct contact.

Furthermore, spatially relative terms such as "under", "below", "lower", "above", "higher" and the like may be used to facilitate describing the relationship between one component or feature and another component or feature in the drawings. Spatially relative terms are used to include different orientations of the device in use or operation, as well as the orientations described in the drawings. When the device is rotated 90 degrees or in other orientations, the spatially relative adjectives used will also be interpreted based on the rotated orientation.

According to some embodiments of the present disclosure, the light emitting device includes a first reflective layer and a second reflective layer, wherein the first reflective layer is disposed on a light emitting diode die, and the second reflective layer is disposed on the first reflective layer. In the mass transfer process used in existing light emitting devices, when using selective laser lift-off (selective LLO) technology, the high temperature of the laser may damage the light emitting diode die, thereby reducing the yield of the light emitting diode die and affecting the performance of the light emitting device. To solve the above problems, in the light-emitting device provided by the embodiment of the present disclosure, a double reflection layer is provided on the LED grain, which can not only improve the external quantum efficiency (EQE) of the LED grain, but also reflect the laser used in the selective laser lift-off technology (selective LLO) to prevent the LED grain from being slightly damaged.

FIG. 1 shows a cross-sectional schematic diagram of a light-emitting device 10 according to an embodiment of the present disclosure. In FIG. 1, the light-emitting device 10 includes a substrate 102 and a plurality of light-emitting diode grains 104 disposed on the substrate 102 at intervals. To simplify the diagram, only three light-emitting diode grains 104 are shown in the figure, but the present disclosure is not limited thereto. Each light-emitting diode grain 104 has a first electrode 112a (e.g., a positive electrode) and a second electrode 112b (e.g., a negative electrode). In some embodiments, the first electrode 112a is a negative electrode, and the second electrode 112b is a positive electrode. The first electrode 112a and the second electrode 112b are disposed on the same side (which may be referred to as the front side) of the LED grain 104 away from the substrate 102. In some embodiments, the substrate 102 may be a sapphire substrate, a silicon substrate, a silicon carbide substrate or a ceramic substrate. The LED grain 104 may be a LED chip that emits blue light, red light or green light.

FIG. 2 shows a detailed cross-sectional structure of the LED grain 104 of FIG. 1. In FIG. 2, a first reflective layer 106 is disposed on the LED grain 104, and a second reflective layer 108 is further disposed on the first reflective layer 106. The first reflective layer 106 is used to reflect the outgoing light from the inside of the LED grain 104 to increase the external quantum efficiency (EQE). The second reflective layer 108 is used to reflect the external laser of the selective laser lift-off technology (selective LLO) used in the subsequent batch transfer of the LED grains 104 to prevent the LED grains from being slightly damaged. In some embodiments, the first electrode 112a and the second electrode 112b pass through the second reflective layer 108 and are in electrical contact with the LED die 104, as shown in the figure. The process of forming the first reflective layer 106 and the second reflective layer 108 will be described in more detail later.

FIGS. 3A to 3D are cross-sectional views of various intermediate stages in the process of forming a light-emitting diode grain 104 according to various embodiments disclosed herein. Referring to FIG. 3A , an epitaxial semiconductor layer 118 is deposited on a semiconductor substrate 102. In some embodiments, before depositing the epitaxial semiconductor layer 118, a roughening process may be performed on the semiconductor substrate 102 to form a periodically roughened surface 102a. In some embodiments, a patterned substrate (Patterened Sapphire Substrate, PSS) technology is used to form a patterned substrate to increase light extraction efficiency. For example, the patterned substrate may be formed by a lithography process and an etching process. In the lithography process, a photoresist layer (not shown) is first applied to the semiconductor substrate 102 by, for example, spin coating. Next, the photoresist layer is exposed according to a pattern mask and developed to form a periodic pattern in the photoresist layer. The photoresist layer with a periodic pattern can be used as an etching mask to pattern the semiconductor substrate 102. The patterned photoresist layer is then used to protect a portion of the surface of the semiconductor substrate 102, and the etching process forms a recessed hole in the unprotected area into the surface of the semiconductor substrate 102, thereby leaving a periodically roughened surface 102a. Finally, the photoresist layer is removed, for example, by ashing. In some embodiments, the periodic roughened surface 102a is formed using dry etching such as reactive ion etching (RIE), wet etching, or a combination thereof.

It should be noted that the roughening process here is optional and may not be performed, or the light-emitting diode grains 104 may be roughened in a subsequent process (described in detail below). In some embodiments, the epitaxial semiconductor layer 118 includes a first-type semiconductor layer, a light-emitting layer, and a second-type semiconductor layer sequentially formed on the substrate 102. For example, the first-type semiconductor layer and the second-type semiconductor layer may be different types of semiconductor materials, such as the first-type semiconductor layer is gallium nitride (n-GaN) with n-type conductivity, and the second-type semiconductor layer is gallium nitride (p-GaN) with p-type conductivity, and they may also be interchangeable. Other III-V compounds may be used, such as indium nitride (InN), aluminum nitride (AlN), indium gallium nitride (InxGa(1-x)N), aluminum gallium nitride (AlxGa(1-x)N), or aluminum indium gallium nitride (AlxInyGa(1-x-y)N), etc., where 0＜x ≤1, 0＜y ≤1 and 0≤x+y ≤1. The light-emitting layer may have a multiple quantum well (MQW) structure composed of semiconductor materials. The light-emitting layer may include other suitable light-emitting materials, but is not limited thereto. In one embodiment, the formation method of the epitaxial semiconductor layer 118 may include an epitaxial growth process, such as chemical vapor deposition (CVD), metal organic chemical vapor deposition (MOCVD), molecular beam epitaxy (MBE), hydride vapor phase epitaxy (HVPE), liquid phase epitaxy (LPE) or other suitable chemical vapor deposition methods.

Referring again to FIG. 3A , a patterned mesa structure 120 is then formed on the epitaxial semiconductor layer 118 to define the range of the device to be formed next through a patterning process. The patterning process may include lithography and etching processes, which are similar to the aforementioned patterning process and will not be described in detail here.

Referring to FIG. 3B , a first reflective layer 106 is formed on the platform structure 120. The first reflective layer 106 has a high reflectivity for the light emitted from the LED crystal grain 104, for example, greater than 90%, and is used to reflect the light emitted from the LED crystal grain 104 to increase the external quantum efficiency (EQE). In some embodiments, the first reflective layer 106 may be a Bragg reflective layer. In one embodiment, the Bragg reflective layer may include a periodic structure formed by alternating and arranging two material layers with different refractive indices, or a dielectric waveguide with a periodic variation characteristic of the effective refractive index. In one embodiment, the material of the Bragg reflective layer may include an insulator. For example, the material of the Bragg reflector may include silicon dioxide (SiO ₂ ), titanium dioxide (TiO ₂ ), tantalum oxide (Ta ₂ O ₅ ), aluminum oxide (Al ₂ O ₃ ) or silicon nitride (Si ₃ N ₄ ), but is not limited thereto. The thickness of each layer is related to the wavelength of the incident light. When the product of the refractive index and the optical thickness of each layer is equal to one-fourth of the wavelength of the incident light, because the optical path difference between the incident light and the reflected light is exactly an integer multiple of the wavelength of the incident light (nλ, n=1,2,3…), constructive interference is generated and the light cannot penetrate the Bragg reflector layer. By the above principle and material characteristics, the light emitted by the LED crystal grain 104 is reflected to increase the external quantum efficiency (EQE). In one embodiment, the higher the number of Bragg reflector layers, the more obvious the light reflection is. In some embodiments, the thickness of the first reflective layer 106 can be controlled within a range of 0.1µm to 4µm, such as 0.6µm to 2µm.

Next, a second reflective layer 108 is formed on the first reflective layer 106. The second reflective layer 108 has a high reflectivity, for example, greater than 90%, for the laser of the selective laser stripping technology (selective LLO) used in the subsequent process of batch transferring the LED die 104. Therefore, the second reflective layer 108 can reflect the laser of the selective laser stripping technology (selective LLO) used subsequently to prevent micro-damage of the LED die. In some embodiments, the second reflective layer 108 can be a Bragg reflective layer, using a different thickness from the aforementioned first reflective layer 106 as a Bragg reflective layer. In some embodiments, the material of the second reflective layer 108 can be similar to the material of the first reflective layer 106 as a Bragg reflective layer. In some embodiments, the material of the second reflective layer 108 can be completely the same as the material of the first reflective layer 106 as the Bragg reflective layer, reducing the difficulty of the process. In some embodiments, the material of the second reflective layer 108 can be different from the material of the first reflective layer 106 as the Bragg reflective layer, according to the design requirements of the light-emitting device. In some embodiments, the higher the number of layers of the second reflective layer 108, the better the reflection effect, which improves the yield of the light-emitting device. In some embodiments, the thickness of the second reflective layer 108 can be controlled in the range of 0.1µm~4µm, for example, 0.6µm~2µm. In some embodiments, the thickness of the second reflective layer 108 is less than the thickness of the first reflective layer 106.

Then, the first reflective layer 106 and the second reflective layer 108 are patterned to form a cavity 111 that passes through the first reflective layer 106 and the second reflective layer 108, exposing a portion of the epitaxial semiconductor layer 118, as shown in FIG. 3B. The cavity 111 will be used to form an electrode of a light-emitting diode crystal grain later. The patterning process can be similar to the aforementioned patterning process, which will not be described in detail here.

3C, the epitaxial semiconductor layer 118 is etched to form separate LED grains 104. The etching process may include dry etching such as reactive ion etching (RIE), wet etching, or a combination thereof.

Referring to FIG. 3D , a first electrode 112 a and a second electrode 112 b are formed through the first reflective layer 106 and the second reflective layer 108 and are in physical contact with the light-emitting diode grain 104. In some embodiments, the material of the first electrode 112 a and the second electrode 112 b may include metal or metal alloy. For example, the metal material of the first electrode 112 a and the second electrode 112 b may include: copper (Cu), aluminum (Al), indium (In), tin (Sn), gold (Au), platinum (Pt), zinc (Zn), silver (Ag), titanium (Ti), nickel (Ni) or a combination thereof, but is not limited thereto. In some embodiments, the first electrode 112a and the second electrode 112b may be formed using chemical vapor deposition (CVD), including low pressure chemical vapor deposition (LPCVD) and plasma chemical vapor deposition (PECVD), physical vapor deposition (PVD), atomic layer deposition (ALD) or other suitable deposition processes. Subsequently, the electrode layer is patterned using lithography and etching processes, as shown in FIG. 3D. For example, a patterning process similar to the above may be used, which will not be described in detail here.

Referring to FIGS. 4A-4D , according to various embodiments of the present disclosure, cross-sectional views of reflective layers having different types and/or different profiles are shown. In FIG. 4A , in some embodiments, the first reflective layer 106 and the second reflective layer 108 are both Bragg reflective layers, and the first reflective layer 106 can reflect the light emitted by the LED grain 104 toward the front side (the side with the electrode) to increase the external quantum efficiency (EQE). The second reflective layer 108 can reflect the laser of the selective laser lift-off technology (selective LLO) used in the subsequent mass transfer process of the LED grain 104 to prevent micro-damage to the LED grain. As shown in FIGS. 4A, 4C and 4D, in some embodiments, the sidewalls of the second reflective layer 108 are aligned with the exposed sidewalls of the LED die 104. In addition, as shown in FIGS. 4B-4C, the edge of the front side of the LED die 104 may have an opening lower than the platform structure 120. When the first reflective layer 106 and the second reflective layer 108 are formed on the front side of the LED die 104, the first reflective layer 106 and the second reflective layer 108 may extend toward the substrate to fill the opening to cover most of the sidewalls of the LED die 104. The extended portion of the first reflective layer 106 can reflect the light emitted by the LED die 104 to the left and right sides, thereby increasing the external quantum efficiency (EQE). The extended portion of the second reflective layer 108 can reflect the laser of the selective laser lift-off technology (selective LLO) used in the subsequent process of transferring the LED die 104 in batches. As shown in FIG. 4B , in some embodiments, the first reflective layer 106 and the second reflective layer 108 may fill the opening so that the sidewalls of the second reflective layer 108 are aligned with the exposed sidewalls of the LED die 104. This may retain thicker first reflective layer 106 and second reflective layer 108, thereby increasing external quantum efficiency (EQE) and enhancing the reflection of the laser in the selective laser lift-off technique (selective LLO) used in subsequent batch transfer. Alternatively, as shown in FIG. 4C , in some embodiments, the first reflective layer 106 and the second reflective layer 108 may not fill the opening, so that the sidewall of the second reflective layer 108 is retracted into the sidewall of the LED die 104 . This can reduce the complexity of the manufacturing process, thereby eliminating the need for an additional step to align the sidewall of the second reflective layer 108 with the exposed sidewall of the LED die 104 .

In addition, in other embodiments, the first reflective layer 106 can be a metal layer to reflect the output light of the LED grain 104 and increase the external quantum efficiency (EQE), as shown in FIG. 4D. In some embodiments, the material of the first reflective layer 106 includes metals, such as silver (Ag), aluminum (Al), and gold (Au). In some embodiments, the first reflective layer 106 can have a thickness ranging from about 1000Å to about 10000Å. The first reflective layer 106 can be formed by using chemical vapor deposition (CVD), including low pressure chemical vapor deposition (LPCVD) and plasma chemical vapor deposition (PECVD), physical vapor deposition (PVD), atomic layer deposition (ALD) or other suitable deposition processes. It is particularly noted that when the first reflective layer 106 is a metal layer, the metal layer can be directly deposited after the epitaxial semiconductor layer 118 is formed, and then the metal layer and the epitaxial semiconductor layer 118 are etched to form a platform structure 120 and a patterned first reflective layer 106 located on the upper surface of the platform structure 120. Next, a patterned second reflective layer 108 is formed on the first reflective layer 106, and the patterning process can use a patterning process similar to the above-mentioned patterning process. The patterned second reflective layer 108 exposes a portion of the first reflective layer 106 and a portion of the epitaxial semiconductor layer 118. Finally, a first electrode 112a is formed to contact the epitaxial semiconductor layer 118, and a second electrode 112b is formed to contact the first reflective layer 106, as shown in Figure 4D. To simplify the diagram, the process cross-sectional diagram of the embodiment only lists one configuration of the LED die 104 and the first reflective layer 106, but it can be any of 4A-4D.

5 , according to some embodiments of the present disclosure, the first reflective layer 106 laterally covers the light-emitting layer 119. The bottom of the first reflective layer 106 extending into the side wall may be lower than or equal to the bottom surface of the light-emitting layer 119, and may reflect the light emitted to the left and right sides by the light-emitting layer 119, thereby increasing the external quantum efficiency (EQE) of the light-emitting diode die 104.

Referring to FIG. 6 , according to other embodiments of the present disclosure, before depositing the first reflective layer and/or after depositing the second reflective layer, a barrier film 110a and/or 110b may be formed on the LED grain 104 and/or on the second reflective layer 108 as needed. The barrier films 110a and 110b are used to cover the surfaces of the first reflective layer 106 and the second reflective layer 108. In addition to protecting the first reflective layer 106 and the second reflective layer 108 from damage by external substances such as moisture or oxygen, the barrier films 110a and 110b may also fill in defects caused when depositing the reflective layers, prevent leakage current, and increase reliability. In some embodiments, the barrier films 110a and 110b may each include an inorganic material, such as a metal oxide (e.g., _SiO2 , _Al2O3 , _etc. ) or a metal nitride (e.g., _Si3N3 , _etc. ). In some embodiments, the barrier films 110a and 110b may be multi-layer barrier films, which are disposed on the surface of the first reflective layer 106 and/or the second reflective layer 108 by coating or laminating. In some embodiments, the thickness of the barrier films 110a and 110b is greater than 10 nm and less than 500 nm.

FIGS. 7, 8, 9, 10, 11, 12, 13, 14, 15 and 16 are cross-sectional views showing various intermediate stages in the process of mass transferring LED die 104 according to some embodiments of the present disclosure.

Referring to FIG. 7 , first, a carrier 202 is provided, and a first adhesive layer 114 (also referred to as a glue) is provided on the carrier 202. In some embodiments, the material of the carrier 202 may include a plastic substrate, a glass substrate, a silicon substrate or a sapphire substrate, or other suitable materials, but not limited thereto. In some embodiments, the first adhesive layer 114 may be a UV glue that reacts with the laser used later. In some embodiments, the first adhesive layer 114 will decompose after absorbing the laser used, so that the LED die 104 is peeled off from the first adhesive layer 114. In some embodiments, the wavelength of the laser used is less than 420 nm, for example, the wavelength is 248, 260, 280, 355 nm, etc., but not limited thereto.

In some embodiments, the first adhesive layer 114 can be deposited on the carrier 202 by spin coating. Then, the first electrode 112a and the second electrode 112b of the semiconductor device 10 of FIG. 1 are bonded to the first adhesive layer 114 on the carrier 202. In some embodiments, the first adhesive layer 114 is squeezed into the gap between the LED die 104, attached to part of the sidewall of the LED die 104, and covers the first electrode 112a and the second electrode 112b, but does not directly contact the substrate 102, as shown in FIG. 7. In some embodiments, the first adhesive layer 114 covers more than 80% of the surface of the LED die 104. In other embodiments, the first adhesive layer 114 may be attached around the LED die 104 and directly contact the substrate 102 (not shown).

8, the substrate 102 is removed by a fully laser lift-off (fully LLO) process 113 to transfer all the LED dies 104 to the carrier 202. In some embodiments, the fully laser lift-off (fully LLO) process 113 is applied from the surface of the substrate 102 to remove the substrate 102. In some embodiments, the wavelength of the laser used in the fully laser lift-off (fully LLO) process 113 is below 420nm, for example, the wavelength is 248, 260, 280, 355nm, etc., but not limited thereto. In some embodiments, the material of the LED grain 104 can completely absorb the laser used in the full laser lift-off technique (fully LLO) to avoid damage to the LED grain 104 caused by the laser. For example, in an embodiment where the LED grain 104 includes a III-V compound (such as gallium nitride), the III-V compound can completely absorb the laser at the interface with the substrate 102 to prevent the laser from damaging the LED grain 104, thereby improving the yield of the light-emitting device.

9 , in some embodiments, since the substrate 102 has a patterned periodic surface 102a, the LED grain 104 also has a periodic roughened surface 104a at the interface with the substrate 102. After the laser stripping process, the periodic roughened surface 104a of the LED grain 104 can be exposed to increase the light extraction efficiency of the LED grain 104.

Referring to FIG. 10 , in other embodiments, after removing the substrate 102, a roughened surface 117a may be formed on the exposed surface of the LED grain 104 through a roughening process 117 as needed to increase the light extraction efficiency of the LED grain 104. In some embodiments, the roughened surface 117a may include semiconductor materials and/or high molecular polymers. For example, a light-transmitting layer (not shown) may be optionally formed on the periodically roughened surface of the LED grain 104. The light-transmitting layer may include a high molecular polymer such as silicone or resin, and may be formed by molding, glue-filling or other suitable processes. Then, a roughening process 117 is performed on the transparent layer to form a periodic roughened surface 117a, for example, by sandblasting or surface etching. In some embodiments, the surface roughness of the roughened surface 117a can be in the range of 0.1µm to 3µm, for example, 0.2µm to 2µm, but not limited thereto.

Referring to FIG. 11 , a light emitting device 20 is formed. Continuing with FIG. 9 , the first adhesive layer 114 between the side walls of the LED die 104 is etched to expose the upper surface of the carrier 202 and separate each LED die 104 to facilitate the subsequent process of selectively transferring the LED die 104 and reduce the difficulty of selective transfer caused by the first adhesive layer 114 remaining between each LED die 104. The etching process may include dry etching such as reactive ion etching (RIE), wet etching or a combination thereof.

Referring to FIG. 12, which is a continuation of FIG. 11, a second carrier 302 is provided, and a second adhesive layer 115 is provided on the second carrier 302. In some embodiments, the material of the second carrier 302 may include a plastic substrate, a glass substrate, a silicon substrate or a sapphire substrate, or other suitable materials, but is not limited thereto. In some embodiments, the second adhesive layer 115 may be a polymer material and an elastic body with viscosity, such as an elastic polymer material with viscosity. In some embodiments, the elastic polymer material with viscosity may include a polysiloxane material, such as polydimethylsiloxane (PDMS). In some embodiments, the second adhesive layer 115 may be deposited by spin coating. Next, the back side (the side away from the electrode) of the light emitting device 20 in FIG. 11 is bonded to the second adhesive layer 115 on the second carrier 302, as shown in FIG. 12 .

Referring to FIG. 13 , continuing from FIG. 12 , the LED die 104 is selectively transferred to the second carrier 302. The LED die 104 is selectively stripped from the first carrier 202 by performing a selective laser stripping (selective LLO) process 116 on the electrode side of the LED die 104 to be transferred. In some embodiments, the wavelength of the laser used in the selective laser stripping (selective LLO) process 116 is below 420 nm, for example, the wavelength is 248, 260, 280, 355 nm, etc., but not limited thereto. In some embodiments, the first adhesive layer 114 cannot completely absorb the laser used in the selective laser stripping process 116. In order to avoid damage to the LED die 104 caused by the high temperature of the laser, the second reflective layer 108 on the LED die 104 can reflect the laser used in the selective laser stripping process 116, thereby reducing the impact of the high temperature of the laser on the LED die 104 and increasing the yield of batch transfer.

14 , following FIG. 13 , the first carrier 202 is removed so that the LED die 104 to be transferred leaves the first carrier 202 and adheres to the second adhesive layer 115 , while the untransferred LED die 104 remains on the first carrier 202 and leaves the second adhesive layer 115 .

Referring to FIG. 15 , a light emitting device 30 is formed. Continuing with FIG. 14 , the first adhesive layer 114 on the LED die 104 is etched to expose the bottom surface and part of the sidewall of the first electrode 112 a and the second electrode 112 b of the LED die 104 to facilitate the subsequent bonding process so that the LED die 104 can be electrically connected to the target backplane. In some embodiments, the etching process can be similar to the etching process for etching the first adhesive layer previously. In some embodiments, the etching process can include other suitable processes. In some embodiments, the first adhesive layer 114 remains on the front side of the LED die 104, covers part of the sidewalls of the first electrode 112a and the second electrode 112b, and can protect the LED die 104 and part of the sidewalls of the first electrode 112a and the second electrode 112b. In some embodiments, when etching the first adhesive layer 114 of the LED die 104, a part of the second adhesive layer 115 between the LED die 104 may also be etched, so that the second adhesive layer 115 between the LED die 104 is thinned. This thinned portion can prevent the LED die from accidentally adhering to the existing LED die on the backplane when transferring the LED die to the backplane (described in detail below with reference to FIG. 18 ). In some embodiments, the second adhesive layer 115 includes a second adhesive layer 115a located between the LED die 104 and a second adhesive layer 115b directly contacting the LED die 104 . It is worth noting that the above etching process etches the second adhesive layer 115a between the LED dies 104, and uses the LED dies 104 as a hard mask, leaving the second adhesive layer 115b directly contacting the LED dies 104, so the thickness of the second adhesive layer 115a between the LED dies 104 is thinner than the thickness of the second adhesive layer 115b directly contacting the LED dies 104. Therefore, in some embodiments, the second adhesive layer 115 has an irregular surface. In some embodiments, the thickness of the second adhesive layer 115a between the LED dies 104 is different from the thickness of the second adhesive layer 115b directly contacting the LED dies 104.

Referring to FIG. 16 , which is a continuation of FIG. 15 , a backplane 402 is provided, and a plurality of conductive components 412 are provided on the backplane 402. In some embodiments, the material of the backplane 402 may include a glass substrate or a plastic substrate or other suitable materials, but is not limited thereto. The conductive component 412 may be a metal electrode, for example, the material of the conductive component 412 may include nickel (Ni), tin (Sn), indium (In), gold (Au), titanium (Ti), copper (Cu) or a combination thereof, but is not limited thereto. In some embodiments, the conductive component 412 may be pre-melted to have adhesiveness, or the conductive component 412 may further include solder or adhesive material with similar effects pre-set on the metal electrode. Next, the first electrode 112a and the second electrode 112b of the light emitting device 30 of FIG. 15 are bonded to the conductive component 412 on the back plate 402. In some embodiments, the first electrode 112a and the second electrode 112b are electrically in contact with the conductive component 412, respectively, as shown in FIG. 16 .

17 , following FIG. 16 , the second carrier 302 is removed so that the LED die 104 to be transferred leaves the second carrier 302 and is bonded to the conductive component 412 of the back plate 402 , as shown in FIG. 17 .

The batch transfer disclosed in the present invention can selectively transfer the LED chips 104 to the target backplane 402 according to the design requirements of the target backplane 402. For example, the first type of LED chips 104 (e.g., blue diodes) arranged at intervals can be transferred to the target backplane 402 first, and then the second type of LED chips 105 (e.g., red diodes) can be transferred to the intervals on the target backplane 402, as shown in Figures 18 and 19. The above description is only an example, but is not limited thereto. More types of LED chips can be transferred to the target backplane 402 according to the design requirements of the backplane. In addition, as shown in FIG. 18, since the thickness of the second adhesive layer 115a between the LED dies 104 is thinner than the thickness of the second adhesive layer 115b directly contacting the LED dies 104, the second adhesive layer 115a can be prevented from adhering to the LED dies 104 that have been transferred to the target backplane in the subsequent transfer process, thereby increasing the process yield. Afterwards, the carrier 302 is removed to obtain the backplane shown in FIG. 19. In some embodiments, the spacing between each LED die 104 can be changed according to the design requirements of the backplane. The batch transfer disclosed in the present invention can not only be applied to different types of LED dies 104, but can also be widely applied to the field of batch transfer or mass transfer of various micro-semiconductor structures.

It should be noted that the present disclosure generally describes a process for batch transfer of LED dies. Other processes and sequences may be used. For example, fewer or additional carriers may be used, a different sequence of steps may be used, additional carriers may be formed and removed, and/or similar processes may be used. Furthermore, different structures and steps may be used to form LED dies.

According to the embodiment provided by the present disclosure, the light-emitting device includes a first reflective layer and a second reflective layer. The first reflective layer is on the LED crystal grain, and the second reflective layer is on the first reflective layer. By setting the first reflective layer on the LED crystal grain, the first reflective layer can reflect the light emitted by the LED crystal grain, thereby improving the external quantum efficiency (EQE) of the LED crystal grain, thereby improving the light extraction efficiency of the light-emitting device. In addition, by setting the second reflective layer on the first reflective layer on the LED crystal grain, the second reflective layer can reflect the laser of the selective laser stripping process (selective LLO) used in the batch transfer process, thereby reducing the influence of the high temperature of the laser on the LED crystal grain, thereby increasing the yield of the batch transfer.

Although some embodiments of the present invention and their advantages have been described in detail, it should be understood that various changes, substitutions and modifications may be made without departing from the spirit and scope of the invention as defined by the scope of protection of the present invention. For example, a person having ordinary knowledge in the art to which the present invention belongs should readily understand that many of the components, functions, processes and materials described herein may be changed without departing from the scope of the present invention. Furthermore, the scope of this application is not limited to the specific embodiments of the processes, machines, manufactures, material compositions, methods and steps described in the specification. A person with ordinary knowledge in the technical field to which the present invention belongs can easily understand from the present invention that any process, machine, manufacturing, material composition, method or step currently or developed in the future, as long as it can achieve substantially the same function or substantially the same result as the corresponding embodiment described herein, can be used according to the embodiments of the present invention. Therefore, the protection scope of the present invention includes the above-mentioned process, machine, manufacturing, material composition, method or step.

10,20,30: light-emitting device 102: substrate 102a: roughened surface 104: light-emitting diode grain 104a: roughened surface 106: first reflective layer 108: second reflective layer 111: cavity 112a,112b: electrode 113: laser stripping process 114: first adhesive layer 115: second adhesive layer 116: laser stripping process 117: roughening process 117a: roughened surface 118: semiconductor layer 119: light-emitting layer 120: platform structure

Reading the subsequent detailed description and examples with the attached figures will enable a more comprehensive understanding of the embodiments of the present invention, wherein: FIG. 1 is a cross-sectional view of a light-emitting device according to an embodiment of the present disclosure. FIG. 2 is a cross-sectional view of a light-emitting diode crystal grain according to an embodiment of the present disclosure. FIGS. 3A to 3D are cross-sectional views of various intermediate stages in the process of forming a light-emitting diode crystal grain according to some embodiments of the present disclosure. FIGS. 4A to 4D are cross-sectional views of forming a reflective layer with different types and/or different profiles according to various embodiments of the present disclosure. FIG. 5 is a cross-sectional view of forming a light-emitting diode crystal grain with a light-emitting layer according to an embodiment of the present disclosure. FIG. 6 is a cross-sectional view showing the formation of a light-emitting diode grain with a barrier film according to an embodiment of the present disclosure. FIG. 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18 and 19 are cross-sectional views showing various intermediate stages in the process of mass transfer of light-emitting diode grains according to some embodiments of the present disclosure.

104: LED grains

104a: Roughened surface

106: First reflection layer

108: Second reflective layer

112a,112b:Electrode

Claims (13)

A light-emitting device, comprising: A first-type light-emitting diode crystal, comprising a semiconductor layer and a first electrode, the first electrode being located at a front side of the first-type light-emitting diode crystal and electrically connected to the semiconductor layer, wherein the first-type light-emitting diode crystal has an output light, which is emitted from the inside of the semiconductor layer; and; A first reflection layer and a second reflection layer are sequentially stacked on the front side of the first-type light-emitting diode crystal grain, and the first reflection layer and the second reflection layer are located between the semiconductor layer and the first electrode, wherein the first reflection layer is used to reflect the outgoing light from the inside of the first-type light-emitting diode crystal grain, and the second reflection layer is used to reflect a laser light from the outside, and the wavelength of the laser light is less than 420nm. The light-emitting device of claim 1, wherein the second reflection layer is a Bragg reflection layer. The light-emitting device of claim 1, wherein the first reflection layer is a metal reflection layer, a Bragg reflection layer or a combination thereof. The light emitting device of claim 1, wherein the first type light emitting diode die comprises an opening located at an edge of the front side, and the second reflective layer extends from the front side to fill the opening. A light-emitting device as claimed in claim 4, wherein the second reflective layer fills the opening. A light-emitting device as claimed in claim 4, wherein the second reflective layer does not fill the opening. A light-emitting device as claimed in claim 4, wherein the first reflective layer extends from the front side to fill the opening. The light-emitting device of claim 7, wherein the first reflective layer and the second reflective layer fill the opening. The light-emitting device of claim 1, wherein the sidewall of the second reflective layer is aligned with the exposed sidewall of the first-type light-emitting diode grain. The light emitting device of claim 1, wherein the first type light emitting diode die further comprises a second electrode located at the front side and electrically connected to the semiconductor layer. Any light emitting device as in claim 1 to 10 further comprises a carrier comprising a plurality of conductive components, the first type light emitting diode die is located on the carrier, wherein the first electrode of the first type light emitting diode die faces the carrier, and the first electrode is electrically connected to one of the conductive components. The light emitting device of claim 11 further comprises a colloid located on the front side of the first type light emitting diode die, wherein the colloid covers a portion of the side wall of the first electrode. The light emitting device of claim 11 further comprises a second type of light emitting diode die located on the carrier, wherein the light emitting type of the second type of light emitting diode die is different from the light emitting type of the first type of light emitting diode die.

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